Article

A study of flotation characteristics of monazite, hematite and quartz using anionic collectors

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Abstract

Rare earth elements (REE) minerals found in most South Australian ore deposits are in complex association with gangue minerals, typically hematite and quartz. Monazite, a phosphate mineral containing mainly light REE, is one of the principal minerals found in South Australian REE-bearing deposits. Froth flotation, which exploits the differences in the physicochemical properties of minerals has proven to be effective in the beneficiation of REE minerals. The physicochemical properties of monazite, hematite and quartz including zeta potential, contact angle and floatability were determined in this investigation. Sodium oleate, sodium dodecyl sulphate and hydroxamic acid were employed as collectors. Electroacoustic zeta potential measurements were used to identify the interaction between monazite, hematite and quartz and the selected collectors. The capillary rise method was used to determine the contact angle of the three minerals. Single mineral flotation using Denver microflotation cell was carried out to confirm physicochemical properties measured. It is shown that the contact angle of the minerals is dependent on the collector type used. The isoelectric point (IEP) of monazite, hematite and quartz occurred at pH of 6.5, 6.9 and 2.2, respectively. The zeta potential results also suggests that the collectors chemisorb onto monazite and hematite surfaces with a corresponding change in IEP values. Single mineral flotation results demonstrated that monazite and hematite could be floated by the selected collectors, however, low or no quartz flotation was observed in some cases. Results from electrokinetic and contact angle measurements are consistent with that of the floatability of monazite, hematite and quartz.

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... Anionic collectors namely sodium oleate, hydroxamic acid, and sodium dodecyl sulphate were found to chemisorb onto monazite and hematite surfaces, respectively at weak acid to strong alkaline conditions. It is expected that flotation of monazite from deposits enriched with hematite as the major gangue phase will be unselective (Abaka-Wood et al., 2017). The previous investigation revealed that flotation using sodium oleate, an anionic fatty acid collector, was relatively selective compared to hydroxamic acid and sodium dodecyl sulphate. ...
... Washburn method was employed in measuring contact angle of the minerals using Dynamic Contact Angle Meter and Tensiometer DCAT 21 (DataPhysics Instruments GmbH, Germany) as described in previous publication (Abaka-Wood et al., 2017). The packing of each mineral powder (pulverised to b 38 μm) in the absence and presence of 1000 g/t oleic acid into the glass tube was carried out manually via tapping in defined number of vertical motion at a rate of 1 tap/s over 30 s. ...
... In a previous investigation by Abaka-Wood et al. (2017), the contact angle of the exact minerals was determined. The contact angle of the The contact angle of monazite, hematite, and quartz in the absence and presence of 1000 g/t oleic acid has been presented in Table 4. ...
Conference Paper
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Monazite is a major rare earth elements (REE)-bearing phosphate mineral predominantly found in low grade concentrations. It commonly occurs in sub-economic (<1 wt.%) level in most South Australian ores, often in association with quartz and hematite gangue minerals. Monazite’s REE, cerium, lanthanum and neodymium, which are major constituents of many high-tech (eg. phosphors, glasses, lasers, magnets, optics) and green energy sector products where robust performance and low carbon emissions are important. Froth flotation, which exploits the differences in the hydrophobicity of minerals can be used to achieve significant monazite ore upgrade. The present work investigates the selective flotation recovery of monazite from hematite and quartz minerals mixture using oleic acid as a collector and sodium silicate and starch as depressants. Specifically, the effect of oleic acid dosage (500–2000 g/t), depressants dosage (1000–8000 g/t) and model ore grade (0.8, 10 and 33.3 wt.%) on flotation recovery of monazite was determined. It is shown that the depressant efficiency of both sodium silicate and starch on hematite and quartz increased with increasing depressants dosage. The results also show that sodium silicate and starch reduced the flotation recovery of both hematite and quartz than that of monazite and notable differences in recovery resulted. Flotation recovery of monazite decreased with increasing grade of monazite mixture in the presence of sodium silicate. A favourable condition for selective flotation of monazite from gangue minerals in low grade ores is envisaged if full mineral liberation is attained.
... Iron oxides can be recovered by direct flotation using anionic collectors or inverse flotation of siliceous gangue using both anionic and cationic collectors (Arantes and Lima, 2013;Araujo et al., 2004). Fatty acids are known to adsorb on the surface of hematite by means of chemical bonding which has been established by researchers (Abaka-Wood et al., 2017b;Filippov et al., 2014;Han et al., 1973;Joseph-Soly et al., 2015;Quast, 2000;Quast, 2006;Quast, 2015;Shibata and Fuerstenau, 2003). Silicate minerals, typically quartz have been reported to float poorly in the presence of anionic collectors, and will require surface activation by cationic impurities, at differing pulp pH to achieve flotation (Abaka-Wood et al., 2017a;Fuerstenau and Somasundaran, 2003). ...
... A review of the literature and previous model minerals studies (Abaka-Wood et al., 2017a;Abaka-Wood et al., 2017b) suggest that both monazite and hematite can be floated using fatty acids, hence the need for depressants that will selectively hinder the recovery of hematite. Starch has been used as a universal depressant for iron oxides. ...
... A critical review of the literature has indicated a lack of knowledge and data on the recovery of monazite from hematite and quartz in a unit ore system, using sodium oleate flotation. In a previous single minerals flotation investigation (Abaka-Wood et al., 2017b), it was identified that sodium oleate is capable of producing a comparatively selective monazite recovery from hematite and quartz, although the similarity in monazite-oleate and hematite-oleate adsorption warrants the use of depressants. This hypothesis gave the motivation for this study and has stimulated the focal research question: ...
Article
Froth flotation plays a significant role in the beneficiation of rare earth elements (REE) minerals from differing ores. Monazite has been identified as one of the principal REE minerals in most iron oxide silicate rich tailings generated in Australia from the extraction of primary commodities such as copper and gold. These tailings generally contain hematite and quartz as the major gangue minerals. A previous investigation has identified almost identical flotation response between monazite and hematite in the presence of anionic collectors. Therefore, it is necessary to investigate the feasibility of selective flotation of rare earth oxides (REO) in monazite from hematite–quartz mixtures, to identify cost-effective processing methods. The flotation conditions for selective REO separation from model minerals mixtures were tested in a 1.2 L Denver flotation cell using sodium oleate as a collector. Sodium silicate and starch were tested as depressants for hematite and quartz. Results from the flotation tests revealed that the increased dosage of sodium oleate led to an increase in REO recovery with a corresponding decrease in upgrade, and increased hematite (Fe2O3) and quartz (SiO2) recoveries. In the absence of depressants, the separation of REO from a low grade mixture (0.83% REO feed grade) was unselective, where 3000 g/t sodium oleate recovered 98% REO at a grade of 1.31% (enrichment ratio, E = 1.58) along with 77% Fe2O3 and 37% SiO2 recoveries. However, the depressants reduced the flotation recovery of Fe2O3 and SiO2, which was shown by an improvement in REO grade. The flotation recovery of REO decreased to 84% with a corresponding increase in grade to 4.13% when 1000 g/t sodium silicate was used in the presence of 3000 g/t sodium oleate. Furthermore, 1000 g/t starch in the presence of 3000 g/t sodium oleate increased REO concentrate grade to 5.56% although the recovery decreased to 65%. Subsequently, a rougher–scavenger flotation test conducted with the mixed depressants (sodium silicate: starch, 1:1) produced a final concentrate recovering 61% REO at a grade of 6.25%. This study has shown that REO can be separated selectively from hematite–quartz rich mixtures by flotation when using sodium oleate as the collector and sodium silicate and starch as depressants.
... Monazite ((Ce, La, Nd, Th) PO 4 ) is one of the three principle commercial rare earth minerals, i.e., monazite, bastnaesite, and xenotime. Due to the complex mineralogy and ultrafine grain size of several rare earth mineral sources, significant studies regarding monazite flotation using different collectors have been reported within the last few years [29][30][31][32][33][34][35][36][37]. Most of the studies used the electrokinetic properties of monazite to explain collector adsorption and particle coagulation. ...
... However, results from systematic studies of the surface charging mechanisms of monazite in aqueous systems are limited [21]. Isoelectric point (IEP) values of pH 5.0, 5.3, and 6.5 have been reported for monazite in recent studies [30,[32][33][34]36]. Based on the data reported by Cheng (2000), the IEP of monazite varied significantly from pH 1.1 to 9.0, indicating the necessity to conduct a systematic study on the surface charge mechanisms of monazite particles in solution [21]. ...
... The findings of the electrokinetic study revealed that the zeta potential of the natural monazite surface decreased by almost 60 mV when the solution pH value was increased from 3.0 to 9.5 ( Fig. 1), indicating that hydroxyl and hydrogen ions are potential determining ions for monazite surfaces. The IEP of the natural monazite occurred at pH 6.0, which agreed with reported values in literature [21,30,[32][33][34]36]. ...
Article
The surface charge mechanisms of monazite were studied using electrokinetic tests, solution equilibrium calculations, crystal structure characterization, and electrostatic model predictions. The isoelectric point (IEP) of a natural monazite sample was found to occur at pH 6.0. To allow a theoretical study of the surface charge on monazite, fundamental values associated with cerium monazite (CePO4) were utilized to quantify the isoelectric point (IEP) and point of zero charge (PZC) using solution equilibrium calculations and electrostatic models. The IEP and PZC of the cerium monazite were determined to be equal with a pH value of 7.2. Hydroxyl and hydrogen were found to be potential determining ions and preferential hydrolysis of the lattice ions played a minor role. The findings support the hypothesis that the charge of monazite surfaces in water is a result of protonation/deprotonation reactions. The difference in the IEP values obtained for the natural monazite and cerium monazite along with the wide range of values reported in literature may be partially explained by the amount of carbon dioxide dissolved in solution. When equilibrating with carbon dioxide at 10–3.5 atm partial pressure, the IEP of the cerium monazite shifted to a solution pH value of 4.5.
... Anionic collectors namely sodium oleate, hydroxamic acid, and sodium dodecyl sulphate were found to chemisorb onto monazite and hematite surfaces, respectively at weak acid to strong alkaline conditions. It is expected that flotation of monazite from deposits enriched with hematite as the major gangue phase will be unselective (Abaka-Wood et al., 2017). The previous investigation revealed that flotation using sodium oleate, an anionic fatty acid collector, was relatively selective compared to hydroxamic acid and sodium dodecyl sulphate. ...
... Washburn method was employed in measuring contact angle of the minerals using Dynamic Contact Angle Meter and Tensiometer DCAT 21 (DataPhysics Instruments GmbH, Germany) as described in previous publication (Abaka-Wood et al., 2017). The packing of each mineral powder (pulverised to b 38 μm) in the absence and presence of 1000 g/t oleic acid into the glass tube was carried out manually via tapping in defined number of vertical motion at a rate of 1 tap/s over 30 s. ...
... In a previous investigation by Abaka-Wood et al. (2017), the contact angle of the exact minerals was determined. The contact angle of the The contact angle of monazite, hematite, and quartz in the absence and presence of 1000 g/t oleic acid has been presented in Table 4. ...
... This technique which exploits the differences in surface wettability of mineral particles has proven to be efficient and economical for REE deposits which were otherwise proven to be uneconomical to treat [3,8]. REE minerals are naturally hydrophilic thus require the use of collectors to aid in flotation recovery [3,5,9,10]. ...
... This was carried out to provide an idea of the behaviour of each mineral under the influence of hydroxamic acid at different pulp pH, as well as to establish the selectivity of monazite over both hematite and quartz. Microflotation experiments were performed in a standard 250 cm 3 cell [Instytut Metali Niezelazych (IMN), Gliwice, Poland] with 10 g feed sample [9,10]. The flotation cell was operated at an agitation and airflow rate of 720 rpm and 1.5 dm 3 /min, respectively. ...
... This shows that flotation separation of REO from Fe 2 O 3 and SiO 2 using hydroxamic acid is unselective. A significant SiO 2 recovery in the mixed minerals test compared with that in the single minerals tests was observed, which may be attributed to surface activation of SiO 2 due the presence of soluble cations such as Fe 3+ (4.94 Â 10 À3 M) and Al 3+ (1.22 Â 10 À2 M) from mainly the Fe 2 O 3 ore in the mixture [9,10,35,36]; and entrainment recovery of fine SiO 2 mineral particles [8]. ...
Article
Monazite is a major rare earth elements (REE)-bearing phosphate mineral predominantly found in association with hematite and quartz in some Australian rare earth deposits. The flotation of rare earth oxides (REO) in monazite from mixtures containing monazite, hematite, and quartz with hydroxamic acid as a collector has been investigated using an IMN microflotation cell and a 1.2 L Denver flotation cell. Maximum flotation recovery of both monazite and hematite was attained at pH 7, whereas that of quartz, at pH 3. The flotation kinetics data indicated the need for depressants to achieve selective REO recovery from hematite and quartz mixtures. Sodium silicate and starch were thus tested as depressants of both hematite and quartz. The separation efficiency of REO in the absence of depressants was low and averaged 6.42% at 99% REO recovery, but could be increased to 44.78% with corresponding 93% REO recovery when 4000 g/t starch was used. However, the efficiencies of REO separation obtained with sodium silicate were generally lower (<18%), due to higher gangue minerals content in the flotation concentrates. A blend of sodium silicate and starch showed a good performance for REO recovery, with enhanced selectivity against hematite and quartz through a rougher-cleaner flotation test. This study presents the feasibility of upgrading REO from iron-oxide rich tailings using hydroxamic acid, in the presence of sodium silicate and starch as depressants.
... Compared to bastnӓsite, the adsorption of sodium oleate (and oleic acid) to the surface of both minerals has been shown to occur over a wider pH range (pH 3-11). Maximum monazite recoveries are generally reported at pH 3 and in the pH range 6-9 [25,69,73,85,87,90]. It is noted that while similar trends were observed by these authors there were differences in flotation response. ...
... Abeidu [87] tested the pH range 4-10 and observed elevated recoveries from 5 to 9, with a maximum at pH 7. Cheng et al. [25] observed high recoveries from pH 3 to 10. Pavez and Peres [85] and Pavez et al. [69] observed recovery maximums at pH 3 and 7, with elevated recovery across the pH range investigated (2-10). Abaka-Wood et al. [90] observed a maximum at pH 9, with relatively high recovery from pH 5-9 and a drastic decrease at pH 3 and 11. Espiritu et al. [73] found maximum recoveries in the pH range of 6-7, and low recoveries at pH 4 and from pH 8-11. ...
... These are summarized in Tables 15 and 16. Alkyl sulfates have been reported as collectors for monazite flotation [12,87,90,104]. Choi and Whang [104] and Abeidu [87] reported good monazite floatability at pH below its IEP (pH ≤~4), suggesting collector adsorption through electrostatic interactions. Abaka-Wood et al. [90] found contradictory results indicating monazite floats well across the pH range 3-11. ...
Article
The rare-earth elements (REE), which encompass the fifteen metallic elements of the lanthanoid series of the periodic table, yttrium and occasionally scandium, have gained enormous public, economic and scientific attention in recent years. These elements, which have been found in over 250 minerals, are of high economic and strategic importance to many high-technology industries. As such they have been designated as critical materials by several countries and many new deposits are being developed. Rare-earth mineral (REM) deposits can be broadly classified into four geological environments: carbonates, alkaline/peralkaline igneous rocks, placers and ion adsorption clays. Apart from ion adsorption clay deposits, which require no mineral processing steps, froth flotation is the most applied beneficiation technique. This paper reviews the flotation of REM, covering their surface chemical properties as well as the various flotation reagents which have been employed.
... At pulp pH 9, both sodium oleate and hydroxamic acid have been reported to adsorb chemically onto REE minerals' surfaces (Abaka-Wood et al., 2017b;Jordens et al., 2013;Pradip and Fuerstenau, 1983). The significant contrast between the hydroxamic acid and sodium oleate flotation performance agrees with previous studies by Abaka-Wood et al. (2018b), Espiritu et al. (2018), Filippov et al. (2016, and Pradip and Fuerstenau (1991). ...
... Mineralogical analysis on the non-magnetic tails indicated the dominance of silicate minerals (83.07%), mainly quartz (36.10%), annite (22.69%), and illite (14.49%), with comparatively low iron oxides (< 6%) content. Sodium oleate and hydroxamates have poor selectivity for silicate minerals (Abaka-Wood et al., 2017a, 2017bBulatovic, 2007). However, the hydrolysis of metallic cations such as Al 3+ , Ca 2+ , Fe 3+ , and Mg 2+ to Al(OH) 2+ , Ca(OH) + , Fe(OH) 2+ , and Mg(OH) + , respectively at pH > 2 ( Abaka-Wood et al., 2017b;Fuerstenau and Palmer, 1976;Fuerstenau and Somasundaran, 2003) could result in unintentional surface activation of silicate minerals, which promotes the flotation of silicate minerals, especially quartz (Fuerstenau and Somasundaran, 2003). ...
... Sodium oleate and hydroxamates have poor selectivity for silicate minerals (Abaka-Wood et al., 2017a, 2017bBulatovic, 2007). However, the hydrolysis of metallic cations such as Al 3+ , Ca 2+ , Fe 3+ , and Mg 2+ to Al(OH) 2+ , Ca(OH) + , Fe(OH) 2+ , and Mg(OH) + , respectively at pH > 2 ( Abaka-Wood et al., 2017b;Fuerstenau and Palmer, 1976;Fuerstenau and Somasundaran, 2003) could result in unintentional surface activation of silicate minerals, which promotes the flotation of silicate minerals, especially quartz (Fuerstenau and Somasundaran, 2003). Fuerstenau and Palmer (1976) showed that maximum quartz recovery at pH 7-9 was achieved in the presence of MnOH + (which is absent in the feed used in this work). ...
Article
This study is the second part of an ongoing investigation to recover and upgrade rare earth elements (REE) minerals from iron oxide–silicate rich tailings (IST) generated at a South Australian mining operation. Previous work (Part 1) has shown that REE minerals are preconcentrated in a high-intensity magnetic concentrate and non-magnetic tails along with iron oxides and silicate minerals, respectively. As a part of the overall beneficiation and enhanced REE minerals recovery strategy, complementary studies involving downstream froth flotation of the magnetic preconcentrates were conducted and the results presented in this paper. Froth flotation of the preconcentrates was carried out using sodium oleate and hydroxamic acid as collectors in the presence of sodium silicate and starch as depressants. A comparison of rougher flotation of the preconcentrates indicated that hydroxamic acid produced higher total rare earth oxides (TREO) recoveries (91–93%) with enrichment ratio ranging 1.03–1.30, whereas sodium oleate produced relatively higher upgrade (1.50–1.55 ratios) with significantly lower recoveries (12–36%). Scavenger and cleaner flotation tests were conducted on selected concentrates and tails, where further upgrade was achieved at the expense of recovery. Two process flowsheets for recovering REE minerals were then developed. Flowsheet 1 includes magnetic preconcentration followed by flotation using both collectors, whilst Flowsheet 2 includes magnetic preconcentration prior to hydroxamic acid flotation. Typical metallurgical results indicated Flowsheet 1 produced a final concentrate grade of 1.55% at 55% TREO recovery, whilst rejecting 47% Fe and 74% Si, whereas a final concentrate grade of 1.67% at 72% TREO recovery, with 39% Fe and 59% Si removed using Flowsheet 2. The REE minerals, in combination with mainly silicates in the non-magnetic tails, allows better upgrade, with 2.5 times enrichment through hydroxamic acid flotation, compared to 1.93 times enrichment from the REE–iron oxides magnetic preconcentrate. Florencite, which was not recovered and upgraded by magnetic separation, was successfully recovered and upgraded along with bastnäsite and monazite by froth flotation. The study has revealed that froth flotation can be used to complement the recovery of REE minerals by magnetic separation, suggesting the IST could be exploited for REE beneficiation. However, it is obvious that minerals liberation and particle size distribution are critical in achieving enhanced REE minerals recovery and upgrade.
... REE are often utilised in magnets due to their high remanence and coercivity, which is a result of the relatively large number of unpaired electrons in their atomic structure, in particular neodymium is a constituent of neodymium iron boron magnets [3]. Rare earth elements are contained within over 200 minerals and ore deposits located over seven continents [4][5][6][7], although the concentrations of REE within the ores are low and such they are difficult to process [2]. Although there is a broad range of interest in rare earth bearing minerals, with the European Commission identifying them as one of the twenty seven critical raw materials, the processing of them is still relatively poorly understood [8][9][10]. ...
... There have been many investigations into the mechanisms of fatty acid and hydroxamate adsorption onto REE minerals, using a range of methods from adsorption kinetic models to infrared spectroscopy [6,54,64,65]. Studies by Pavez et al. [64] and Jordens et al. [71] have shown chemisorption of hydroxamate and fatty acids, with both bonding with metal cations on the mineral surface [71].Other REE minerals such as monazite and ancylite have also been investigated showing they also chemisorb into hydroxamate [55,65]. ...
Article
Rare earth elements (REE) are critical to a wide range of technologies ranging from iPhones to wind turbines. However, processing and extraction of REE minerals from ore bodies is both challenging and relatively poorly understood. An improved understanding of the surface properties of the minerals is critical to informing and optimising their processing. The measurement of zeta potentials can be used to extract information regarding the electron double layer, and hence surface properties of these minerals. The bastnäsite series of REE fluorocarbonate minerals is made up of bastnäsite, synchysite, röntgenite and parisite. Bastnäsite, the most common member of the series, supplies over 50% of the worlds REE. Previous studies of bastnäsite have showed a wide range of surface behaviour, with the iso electric point, when the zeta potential is zero, being measured between pH values of 4.3 and 9.2. In contrast, no values of IEP have been reported for parisite, synchysite or röntgenite. In this work, we review previous studies of the zeta potentials of bastnäsite to investigate the effects of different methodologies and sample preparation. In addition, measurements of zeta potentials of parisite under water, collector and supernatant conditions were conducted, the first to be reported. These results showed an iso electric point for parisite of 5.6 under water, with a shift to a more negative zeta potential with both collector (hydroxamic and fatty acids) and supernatant conditions. The IEP with collectors and supernatant was <3.5. The close correlation between parisite zeta potentials obtained here and previous work on bastnäsite suggests that parisite may be processed in a similar way to bastnäsite, which is potentially, important for further processing of rare earth element bearing deposits.
... Therefore, we decided to use reverse flotation because it can be successful in cases where the gangue contains silicates (quartz or mica) and is floated with a collecto of amine-type, while the valuable minerals are hydrophilic and are enriched in the under flow fraction [13][14][15]. This method was also reported to be the most widely used technol ogy for the desilicification of various important minerals, i.e., iron ore and magnesite or [16][17][18]. Several studies have been focusing on various amines and their derivatives tha can be employed as cationic collectors in reverse flotation. ...
... Therefore, we decided to use reverse flotation because it can be successful in cases where the gangue contains silicates (quartz or mica) and is floated with a collector of amine-type, while the valuable minerals are hydrophilic and are enriched in the underflow fraction [13][14][15]. This method was also reported to be the most widely used technology for the desilicification of various important minerals, i.e., iron ore and magnesite ore [16][17][18]. Several studies have been focusing on various amines and their derivatives that can be employed as cationic collectors in reverse flotation. ...
Article
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Fluorite is a nonrenewable mineral used to produce anhydrous hydrofluoric acid (AHF) and aluminum fluoride. The demand for low-grade fluorite powder (CaF2 < 97%) has fallen sharply owing to the current market conditions. Therefore, a large number of fluorite concentrates have been improved by acid leaching. While this approach can efficiently remove CaCO3 from fluorite concentrate, the SiO2 content, which significantly affects AHF consumption during the production of HF or aluminum fluoride, cannot be completely removed. To solve this problem, in this study, we used reverse flotation before leaching the fluorite concentrates. Subsequently, the feasibility of reverse flotation desilication was determined. The obtained results of the ZP (zeta potential) measurements, solution chemistry analysis, FTIR (Fourier transform infrared spectroscopy) analysis, and micro-flotation tests indicated that employing dodecylamine as the collector and citric acid as the depressor could effectively separate sericite from fluorite. The batch flotation experiment and the pilot test were conducted in Chenzhou (Hunan, China) followed by their operation in Xinyuan Mining Co. Ltd., which produces monolithic fluorite ore on the large scale in Asia. Notably, we found that the contents of both SiO2 and Al2O3 were from 2.82%, 1.17% reduced to 1.28%, 0.74% in the batch flotation experiment. The results of the pilot test showed that the new reverse flotation + leaching technology could dramatically reduce the potential environmental impact and costs, thereby significantly improving the economic benefits by satisfying the requirements of the market.
... By contrast, the IEP of the glass powder was observed at pH 2, and the surface of glass powder was determined to be negatively charged across a broad pH range above pH 2. The cerium oxide abrasive is produced from rare earth minerals such as monazite. The IEP and zeta potentials of the cerium oxide abrasive are similar to the reported analysis results of the monazite [20]. The preceding results suggested that NaOL addition could improve the mutual separation of the cerium oxide abrasive and the polished glass in the abrasive-glass polishing waste, because NaOL could selectively improve the extraction of cerium oxide abrasive. ...
... By contrast, the IEP of the glass powder was observed at pH 2, and the surface of glass powder was determined to be negatively charged across a broad pH range above pH 2. The cerium oxide abrasive is produced from rare earth minerals such as monazite. The IEP and zeta potentials of the cerium oxide abrasive are similar to the reported analysis results of the monazite [20]. With respect to the surfactant collector of DAA, DAA (C14H31NO2) is substantially composed of two components: dodecylamine (C12H25NH2) and acetic acid (CH3COOH). ...
Article
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Applying a cerium oxide abrasive to polish glass components generates a polishing waste containing the cerium oxide abrasive and the glass powder produced during polishing. This research applied the liquid–liquid–powder extraction method to separate the cerium oxide abrasive and the polished glass powder in an abrasive-glass polishing waste for recovering the cerium oxide abrasive. Two liquids of isooctane and water were utilized. The effectiveness of using a cationic and an anionic surfactant collector, i.e., dodecylamine acetate (DAA) and sodium oleate (NaOL), respectively, in improving their extraction and separation was investigated and compared. The results indicated that NaOL addition could improve the mutual separation of cerium oxide abrasive and glass powder but DAA could not, because the former could selectively improve the extraction of cerium oxide abrasive from the water phase to isooctane phase whereas the latter could improve that of both powders. Optimal separation for the cerium oxide abrasive and the polished glass powder in an abrasive-glass polishing waste were achieved by adding NaOL of 7.5 kg/ton at pH 7; the content of cerium oxide abrasive in the solid recovered from the isooctane phase was 96.4% with a recovery of 88.1%.
... Although the REE minerals upgrade in the non-magnetic tails is lower, a comparatively better chance for further upgrade is envisaged. Previous studies have indicated better selectivity of REE minerals against silicates in the presence anionic collectors (Abaka-Wood et al., 2017a;Abaka-Wood et al., 2017b;Jordens et al., 2014a), as typically, quartz is marginally responsive to anionic collectors flotation at high pulp pH (> 6) conditions (Abaka-Wood et al., 2017b;Jordens et al., 2014a). Bulk flotation of the REE-silicates non-magnetic tails will preferentially recover and upgrade the REE minerals, whilst selectively rejecting barren and semi-barren silicate particles. ...
... Although the REE minerals upgrade in the non-magnetic tails is lower, a comparatively better chance for further upgrade is envisaged. Previous studies have indicated better selectivity of REE minerals against silicates in the presence anionic collectors (Abaka-Wood et al., 2017a;Abaka-Wood et al., 2017b;Jordens et al., 2014a), as typically, quartz is marginally responsive to anionic collectors flotation at high pulp pH (> 6) conditions (Abaka-Wood et al., 2017b;Jordens et al., 2014a). Bulk flotation of the REE-silicates non-magnetic tails will preferentially recover and upgrade the REE minerals, whilst selectively rejecting barren and semi-barren silicate particles. ...
Article
This work is part of an ongoing investigation being conducted to recover and upgrade rare earth elements (REE) minerals from iron oxide and silicate rich tailings generated at a South Australian mining operation. Detailed mineralogical characterisation via Quantitative Evaluation of Minerals by Scanning electron microscopy (QEMSCAN) of the tailings established the presence of low grade (<1 wt% REE), fine-sized REE minerals. The REE minerals (bastnäsite, monazite, florencite, stillwellite, brannerite, and stetindite) identified were in intimate associations with weakly ferromagnetic/strongly paramagnetic iron oxides (mainly hematite and goethite) and diamagnetic silicate (quartz, illite, and annite) minerals. Chemical analysis showed the tailings comprised 26.2% Fe, 18.6% Si, 3.9% Al, and 1.07% total rare earth oxides (TREO). A rougher–scavenger–cleaner magnetic separation process was deployed to produce two useful streams of REE minerals concentrate and tails using a wet high-intensity magnetic separator (WHIMS). Typical metallurgical results indicated the rejection of 25% of the iron oxides at 0.11 T, whilst producing a magnetic concentrate with TREO recovery of 51% at a grade of 1.25% and non-magnetic tails with TREO recovery of 41% at a grade of 1.08%, both at 1.74 T. Bastnäsite, monazite, florencite, and stillwellite minerals were confirmed to be paramagnetic, whilst stetindite and brannerite were found to be diamagnetic. Whilst the applied magnetic field intensity was the most important factor in the minerals’ magnetic separation efficacy, particle size distribution and mineralogical characteristics of ores also had significant effect. The findings exemplify both the challenges and opportunities for the beneficiation of complex, low grade REE-bearing iron oxide silicate rich tailings using WHIMS. They indicate that magnetic separation may be used to achieve modest preconcentration, the success of which is limited by the complex nature of the tailings and its concomitant magnetic properties, and thus warranting the need for further downstream processing (e.g., froth flotation) to produce cleaner, higher grade REE minerals concentrates for subsequent values extraction.
... Zeta potential of quartz and hematite as a function of pH (after[49]). ...
Article
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Froth flotation has been widely used in upgrading iron ores. Iron ore flotation can be performed in two technical routes: direct flotation of iron oxides and reverse flotation of gangue minerals with depression of iron oxides. Nowadays, reverse flotation is the most commonly used route in iron ore flotation. This review is focused on the reverse flotation of iron ores, consisting of reverse cationic flotation and reverse anionic flotation. It covers different types of collecting agents used in reverse iron ore flotation, the surface characteristics of minerals commonly present in iron ores (e.g., iron oxides, quartz, alumina-bearing minerals, phosphorus-bearing minerals, iron-bearing carbonates, and iron-bearing silicates), and the adsorption mechanisms of the collecting agents at the mineral surface. The implications of collecting agent-mineral interactions for improving iron ore flotation are discussed.
... Contact angles are considered as the most vital and straightforward measurement to quantify mineral wettability, or hydrophobicity. There are various techniques that can be applied to measure contact angles of mineral samples depending on the geometric form and size of the samples, such as sessile drop technique (de Meijer et al., 2000), captive bubble method ( Jiang et al., 2010), Wilhelmy balance method ( Shang et al., 2008), Washburn capillary rise method (Depalo and Santomaso, 2013;Abaka-Wood et al., 2017), environmental SEM ( Miller and Cooper, 2002;Awatey et al., 2014;Fosu et al., 2015), and AFM ( Ecke et al., 1999;Preuss and Butt, 1999). Nevertheless, measuring contact angles of particulate samples in real ores is difficult because of the irregular shape and size of the samples as well as the chemical heterogeneities of the sample surfaces. ...
... Rath at al. [21] got similar correlation between pH and recovery for magnetite flotation. Several studies on oleate-iron bearing minerals suggested that oleate adsorption on iron oxide minerals and formation stable complex mainly depends on solution pH [22][23][24]. The recovery curve of magnetite is similar to that of enstatite using NaOL as collector. ...
Article
The flotation technique is the most effective method for the silicon removal from magnetite ore, and mixed collectors exhibit superior selectivity and strong synergistic interaction in the flotation of muscovite, feldspar and spodumene ores. In this work, the flotation separation of enstatite and magnetite was investigated using mixed cationic collector cetyltrimethyl ammonium bromide (CTAB) and anionic collector sodium oleate (NaOL). The micro-flotation experiments were conducted on single minerals and mixture minerals with pure and mixed collectors. The results show that it is difficult to separation of magnetite from enstatite with CTAB or NaOL collector alone, and mixed CTAB/NaOL exhibits excellent performance with the mole ratio of 2/1 (CTAB/NaOL) at pH 5.5-8.5. Zeta potential measurements and Fourier transform infrared (FTIR) analyses were performed to detect the underlying mechanism. The results show that the co-adsorption of NaOL and CTAB is found on magnetite and enstatite surface. The limited CTAB adsorb on magnetite surface through hydrocarbon tail-tail interaction and CTAB is bound to the oxide and silicate on enstatite surface by electrostatic adsorption. The adsorption model of the mixed collector CTAB/NaOL on the mineral surface was drawn.
... With a composition of Fe and O is expected that the vast majority consists of minerals like hematite. It is also observed from the measurement of the pH of the IOTs samples that the pH is close to the natural pH, so according to the zeta potential studies of Abaka-Wood et al. and Tudu et al., the charge of the IOTs samples must be low [49,50]. Also, the main mineral in the IOTs is hematite with an isoelectric point of 8.5 [51], the IOTs could also have an isoelectric point similar. ...
Article
The low-grade iron ore generally contains goethite as the major iron phase mineral and kaolinite and other minerals as gangue minerals. During the beneficiation of low-grade iron ore, a lot of fines were generated during different unit operations. These fines report to the tailing pond for the settling of the particles. The presence of kaolinite and goethite minerals reduces the settling rate. Therefore, different flocculants are used to improve the settling rate in the tailings pond. This study highlights the utilization of different flocculants in the settling of Iron Ore Tailings slurry (IOTs) in a tailings pond. Performances of different flocculants such as polyacrylamide, guar gum, and alstafloc are used to study the efficiency of the settling behaviour of IOTs. The tests were performed with fixed doses of flocculant consumption, slurry concentration, and flocculant concentration. Rheological studies were also performed on the IOTs samples to determine the viscoelastic behaviour for specific applications. From the study, it has been observed that the use of polyacrylamide as a flocculant in IOTs results in faster settling of iron ore, leaving a clear supernatant.
... Considering the density, the contrast between BP and PCM is too low for gravity separation (Table 4) (Wills and Finch, 2016). Yet, previous research has shown that monazite can be separated from a FeTi-Oxide gangue minerals by flotation (Table 4) (Jordens et al., 2013;Chelgani et al., 2015;Mushidi, 2015;Northern Minerals, 2015;Abaka-Wood et al., 2017;Zhang et al., 2017). In addition, magnetic separation can successfully separate monazite from quartz (Rosenblum and Brownfield, 1999;Gupta and Krishnamurthy, 2005;Jordens et al., 2015;Kumari et al., 2015). ...
Article
Geometallurgy aims to develop and deploy predictive spatial models based on tangible and quantitative resource characteristics that are used to optimize the efficiency of minerals beneficiation and extractive metallurgy operations. While most current applications of geometallurgy are focused on the major commodity to be recovered from a mineral deposit, this contribution delineates the opportunity to use a geometallurgical approach to provide an early assessment of the economic potential of by-product recovery from an ongoing mining operation. As a case study for this methodology, possible rare earth element (REE) recovery as a by-product of Nb production at the Chapadão mine in the Catalão I carbonatite complex is used. Catalão I is part of the Alto Paranaíba igneous province in the Goias Province of Brazil. Currently, niobium is produced in the complex as a by-product of the Chapadão phosphates mine. This production is performed in the Tailings plant, the focus of this study. REEs, albeit present in significant concentrations, are currently not recovered as by-products. Nine samples from different stages of the Nb beneficiation process in the Tailings plant were taken and characterized by mineral liberation analyzer, X-ray powder diffraction, and bulk-rock chemistry. The recovery of REEs in each of the tailing streams was quantified by mass balance. The quantitative mineralogical and microstructural data are used to identify the most suitable approach to recover REEs as a by-product—without placing limitations on niobium production. Monazite, the most common rare earth mineral identified in the feed, occurs as Ce-rich and La-rich varieties that can be easily distinguished by scanning electron microscopy (SEM)-based image analysis. Quartz, Fe-Ti oxides, and several phosphate minerals are the main gangue minerals. The highest rare earth oxide content concentrations (1.75 wt % total rare earth oxides) and the greatest potential for REE processing are reported for the final flotation tailings stream. To place tentative economic constraints on REE recovery from the tailings material, an analogy to the Browns Range deposit in Australia is drawn. Its technical flow sheet was used to estimate the cost for a hypothetical REE production at Chapadão. Parameters derived from SEM-based image analysis were used to model possible monazite recovery and concentrate grades. This exercise illustrates that a marketable REE concentrate could be obtained at Chapadão if the process recovers at least 53% of the particles with no less than 60% of monazite on their surface. Applying capital expenditure and operational expenditure values similar to those of Browns Range suggests that such an operation would be profitable at current REE prices.
... Tall oil FA, a mixture of oleate and linoleate has been used in the flotation of REMs, specially xenotime and monazite, from a silicate-hematite ore [77]. Based on zeta potential measurements and micro-flotation tests, it was shown that quartz had poor floatability with sodium oleate but when sufficient HA or sodium dodecyl sulfate (SDS) were added, significant recovery was obtained [78]. ...
Article
A high-fidelity kinetic model was developed to identify and elucidate the effects of varying principle froth flotation parameters on the sub-processes that occur within and between the flotation zones. Whereas traditional models fail to adequately address froth recovery and recovery by entrainment, the high-fidelity model defines these phenomena based on an improved understanding of the pulp/froth interface. Solution chemistry considerations that govern rare earth mineral separation by flotation were identified, characterized, and optimized. Application of novel surfactants such H205 and salicylhydroxamic acid (collectors) and dimethyl glycol monobutyl ether (depressant) was evaluated to define optimal flotation conditions. The effect of pressure on fine particle entrainment was also studied because, with certain rare earth mineral ores, sufficient mineral liberation is not achieved at nominal flotation particle sizes. Pressure can be applied to produce the small bubble sizes required for fine particle flotation. The correct solution chemistry for flotation (and not entrainment) can then be utilized for the selective recovery of rare earth minerals. The predictive high-fidelity kinetic model was developed using experimentally derived and statistically significant rate equations and was confirmed through application to copper/molybdenum sulfide and rare earth mineral ore samples. The parametric models identified ideal flotation conditions that optimized the recovery of rare earth minerals using the novel collectors; when the same experiments were modeled using the high-fidelity kinetic model, recovery by entrainment was found to be significant. The effects of pressure on gas dispersion mechanisms, such as gas holdup, and how those mechanisms effect bubble size and kinetic parameters were determined.
... There has been many investigations into the mechanisms of fatty acid and hydroxamate adsorption onto REE minerals, using a range of methods from adsorption kinetic models to infrared spectroscopy [6,54,64,65 ]. Studies by Pavez et al., [64] and Jordens et al., [71] have shown chemisorption of hydroxamate and fatty acids, with both bonding with metal cations on the mineral surface [71].Other REE minerals such as monazite and ancylite have also been investigated showing they also chemisorb into hydroxamate [55,65] 1.5 The electrical double layer ...
Article
Rare earth elements (REE) are critical to a wide range of technologies ranging from mobile phones to wind turbines. Processing and extraction of REE minerals from ore bodies is, however, both challenging and relatively poorly understood, as the majority of deposits contain only limited enrichment of REEs. An improved understanding of the surface properties of the minerals is important in informing and optimising their processing, in particular for separation by froth flotation. The measurement of zeta potential can be used to extract information regarding the electrical double layer, and hence surface properties of these minerals. There are over 34 REE fluorcarbonate minerals currently identified, however bastnäsite, synchysite and parisite are of most economic importance. Bastnäsite–(Ce), the most common REE fluorcarbonate, supplies over 50% of the world's REE. Previous studies of bastnäsite have showed a wide range of surface behaviour, with the iso-electric point (IEP), being measured between pH values of 4.6 and 9.3. In contrast, no values of IEP have been reported for parisite or synchysite. In this work, we review previous studies of the zeta potentials of bastnäsite to investigate the effects of different methodologies and sample preparation. In addition, measurements of zeta potentials of parisite under water, collector and supernatant conditions were conducted, the first to be reported. These results showed an iso-electric point for parisite of 5.6 under water, with a shift to a more negative zeta potential with both collector (hydroxamic and fatty acids) and supernatant conditions. The IEP with collectors and supernatant was <3.5. As zeta potential measurements in the presence of reagents and supernatants are the most rigorous way of determining the efficiency of a flotation reagent, the agreement between parisite zeta potentials obtained here and previous work on bastnäsite suggests that parisite may be processed using similar reagent schemes to bastnäsite. This is important for future processing of REE deposits, comprising of more complex REE mineralogy.
... The zeta potential values of quartz particles with or without of 1 × 10 −4 mol·L −1 HDDPA are shown in Figure 6b. The IEP of quartz particles occurred at pH 2.0, similar to what was previously measured at pH 2.2 [41]. In the presence of HDDPA, the zeta potential of quartz particles barely changed, which implied that HDDPA species hardly adsorbed on to quartz surfaces. ...
Article
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1-hydroxydodecylidene-1,1-diphosphonic acid (HDDPA) was prepared and first applied in flotation of hemimorphite. HDDPA exhibited superior flotation performances for recovery of hemimorphite in comparison with lauric acid, and it also possessed good selectivity against quartz flotation under pH 7.0–11.0. Contact angle results revealed that HDDPA preferred to attach on hemimorphite rather than quartz and promoted the hydrophobicity of hemimorphite surfaces. In the presence of HDDPA anions, the zeta potential of hemimorphite particles shifted to more negative value even if hemimorphite was negatively charged, inferring a strong chemisorption of hemimorphite to HDDPA. The Fourier transform infrared (FTIR) recommended that HDDPA might anchor on hemimorphite surfaces through bonding the oxygen atoms of its P(=O)–O groups with surface Zn(II) atoms. X-ray photoelectron spectroscopy (XPS) gave additional evidence that the Zn(II)-HDDPA surface complexes were formed on hemimorphite.
... The difference between the floatability properties of natural and synthetic hematite was reported in some investigations. [19,[34][35][36][37][38][39] It has been demonstrated that in addition to the significant difference between the IEP of the synthetic and natural hematites, there are some other important differences (e.g., mineralogy, surface hydration, aging, crystal structure) which affect their surface properties and subsequent floatability. [40] Synthesized hematite micro-flotation test results ( Fig. 1) show that its floatability is around 24% in the absence of the depressants. ...
Article
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Starch, dextrin, sodium silicate (SS), and recently sodium co-silicate (SCS) are the most known depressants for the depression of iron oxides through the traditional reverse flotation. However, all these depressants’ adsorption mechanisms on the surface of iron oxides and their main associated minerals (silicate and phosphates) through the reverse anionic flotation did not yet been thoroughly investigated. For filling this gap, as a comparative investigation, this study implemented Fourier Transform Infrared Spectroscopy (FTIR), zeta potential measurement, and micro-flotation tests to determine the adsorption mechanisms of these depressants and explored their effects on the floatabilities of pure hematite, quartz, and fluorapatite. Micro-flotation test results illustrated that all the examined depressants could depress hematite in the presence of an anionic collector. Still, the efficiencies of SS and SCS were higher than those of starch and dextrin. SCS had the lowest depression effect on quartz, and fluorapatite floatability compared to other depressants. Surface analyses depicted that dextrin and starch decreased the collector adsorption on the fluorapatite surface, where SCS and SS had a negligible effect on its floatability. The co-existence of physical and chemical bonds created between dextrin/starch and fluorapatite was the reason for its depression through the anionic reverse flotation.
... Choi and Whang (1963) (Cheng et al., 1993). 하지만, Pavez et al.(1996) (Pavez and Peres, 1993;Pavez et al., 1996;Abeidu, 1972;Abaka-Wood et al., 2017b;Espiritu and Waters, 2018). 선택성이 떨어지는 지방산 계열의 포수제의 대안으로 희 토류 광물에 대해 높은 선택성을 갖는것으로 알려진 하이 드로자믹산을 이용한 연구 역시 다수 진행되어 왔다 Peres, 1993, 1994;Zhang et al., 2016bZhang et al., , 2017Honaker, 2017a, 2018;Espiritu and Waters, 2018;Abaka-Wood at al., 2017a (Sorensen and Lundgaard, 1996;Abeidu, 1972;Peres, 1993, 1994;Zhang et al., 2016;Abaka-Wood et al., 2017aZhang and Honaker, 2018). ...
... The isoelectric point (IEP) was observed at pH 4.2. The observed IEP falls in a pH range lower than the reported ranges of both iron and serpentine ores [66,67].This may be attributed to the existence of fine-grained silica in BIF whose IEP is below pH 2 [68]. ...
Article
In this paper, a dry particle-particle coating technique was implemented to develop magnetic adsorbent from natural mineral constituents. Iron ore, specifically banded iron formation (BIF), was used as guest magnetic particles while serpentine (Serp) was used as host adsorptive material. Surface characterizations for the synthesized composite were investigated. The results confirmed the formation of a composite that combines both magnetic and adsorptive properties. The capability of the composite for hexavalent chromium Cr(VI) removal was investigated under different conditions. A maximum adsorption capacity of 138 mg/g was achieved. The adsorption of Cr(VI) onto the magnetic composite ([email protected]) was further thermodynamically and kinetically investigated. The results indicated that the adsorption follows 1.2-order kinetics and occurs spontaneously with an exothermic nature. Application of [email protected] for the treatment of real tannery effluent was conducted, the composite showed an excellent removal performance not only with Cr(VI) but also with other heavy metals and organic contaminants.
... The zeta potential test can more directly reflect the difference in mineral surface potential and the difference in the adsorption amount of the flotation reagent before and after the adsorption of the flotation reagent [12,[35][36][37]. Therefore, the zeta potential charges were measured when the pH was 7.0 and the concentration of the flotation reagent was 1.6 × 10 −5 mol/L. ...
Article
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Fluorite and scheelite, which are strategic calcium-bearing minerals, have similar active sites (Ca2+); as a result, the efficient separation of the two minerals is still one of the world’s most difficult problems in the field of flotation. In this work, N-decanoylsarcosine sodium (SDAA), a non-toxic and low-cost amino acid surfactant, was applied in the flotation separation of fluorite from scheelite for the first time. In the test, single mineral, binary mixed minerals, and actual ore experiments showed that the pre-removal of fluorite from scheelite by reverse flotation can be achieved. The results of adsorption capacity detections, zeta potential tests, and FTIR analysis showed that the negatively charged SDAA prefers to adsorb onto the positively charged fluorite surface due to the electrostatic interaction. The results of crystal chemistry and DFT calculations showed that SDAA has a stronger chemical interaction and more electron transfer numbers to the Ca atom on the fluorite surface and forms a Ca-SDAA complex. Therefore, the significant difference in the adsorption behavior of SDAA on the surfaces of two minerals provided a new insight into the separation efficiency of amino acids and possesses a great potential for industrial application in scheelite flotation.
... The unliberated associations between REE silicates and iron oxide silicates within fine-grained particles promoted the flotation recovery of silicate minerals (typically quartz, annite, and illite), which may float poorly in the presence of anionic collectors [62]. Furthermore, the genuine interaction of iron oxides with anionic collectors coupled with their intimate associations with REE minerals limited the potency of depressants in preventing their recoveries. ...
Article
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The rapid depletion of high-grade rare earth elements (REE) resources implies that future supplies may be augmented with low-grade ores, tailings, and other unconventional resources to meet cut-off grades and, subsequently, supply demands. This paper presents an amalgamation of studies conducted on selected complex low-grade iron-oxide-silicate-rich tailings, with the overall aim of developing efficacious methods and associated process mineralogy characterization for enhanced REE minerals recovery and upgrade. To this end, a summary of the overarching key results from froth flotation, magnetic separation, and gravity separation studies of the tailings and their implications are presented in this review. Reconciliation of all the findings reveals lucid links between feed ore properties, mainly mineralogy and particle size distribution, as the key influential factors that affect the beneficiation of real complex low-grade tailings, although distinct differences in physicochemical properties of the valuable and gangue minerals may exist. It is clearly established that the unliberated association between REE and gangue minerals within the ore can lead to either synergistic or antagonistic effects on the quality of concentrates produced. Furthermore, the limitations presented by the poorly liberated minerals are exacerbated by their “fine” nature. With appreciable recoveries obtained using such readily available conventional separation methods, the tailings provide additional REE value to the primary commodities; hence, such material could be considered a potential resource for REE beneficiation. The learnings from the respective beneficiation studies are significantly important as they provide the knowledge base and greater understanding of the mineralogical characteristics and beneficiation response of REE minerals in typical complex, low-grade tailings.
... while at pH greater than 10.7, the copper species in the solution were mainly in the form of Cu(OH) 2 , Cu(OH) 3 − , and Cu(OH) 4 2− . Flotation is one of the most common methods used to recover iron ore, which includes reverse flotation of gangue with cationic collector [6][7][8] and direct flotation of iron ore with anionic collector [9][10][11]. Compared with reverse flotation, direct flotation of iron ore ...
Article
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Cu2+ exhibited a good activation effect on specularite. However, its microscopic activation mechanism needs further study. Additionally, Cu2+ was mainly present in the flotation solution as Cu2+, Cu(OH)+, and Cu(OH)2 at pH = 7. Therefore, density functional theory (DFT) calculations were used to investigate the effect of Cu species such as Cu2+, Cu(OH)+, and Cu(OH)2 adsorbed on the crystal structure and properties of the specularite (0 0 1) surface. The adsorption mechanism of different Cu components on the surface was also further clarified by the analyses of the adsorption model, adsorption energy, partial density of states (PDOS), charge transfer, and bond properties. In addition, the obtained results are discussed. Based on the obtained results, it can be concluded that the geometric structure and electronic properties on the surface changed after adsorbing Cu components and that the O3–Fe1–O1 structure was more susceptible to the adsorbates. The adsorption engines results show that Cu components could be spontaneously adsorbed onto the specularite (0 0 1) surface with adsorption energies of −0.76, −0.85, and −1.78 eV, corresponding to Cu2+, CuOH+, and Cu(OH)2, respectively. Therefore, the adsorption stability of the Cu species on the specularite surface increased in the order of Cu2+ < Cu(OH)+ < Cu(OH)2. Additionally, the adsorption sites for Cu species on the surface were different. Cu2+ interacted mainly with O atoms on the surface, forming Cu–O complexes, while Cu(OH)+ and Cu(OH)2 acted mainly through the O atom of –OH, interacting with Fe atoms to form Cu–O–Fe complexes. The formation of Cu–O and Cu–O–Fe complexes increased the adsorption sites for sodium oleate, with more hydrophobic species being generated to improve the floatability of specularite.
... The zeta potential measurements were performed to provide more details about EDA interaction with the mineral surfaces. The zeta potential measurement results of pure minerals as a function of pH indicated ( Figures 5-7) that the point of zero charges (pzc) of pure biotite, phlogopite, and quartz occurred around pH 2. Similar results were reported in other investigations (Table 2) [10,13,24,37,[44][45][46][47][48][49][50]. EDA solution (30 mg/dm3) exhibited a positive charge over a wide pH range ( Figures 5-7) which is associated with its cationic active species, e.g., aminium ion, RNH3+, and dimerization of aminium ions: (RNH3)2+2. ...
Article
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Micaceous minerals, known as layer silicates, are counted mostly as the gangue minerals associated with valuable minerals, especially iron oxides. They mainly reject through the reverse flotation process using the cationic collectors, e.g., ether amines, to improve process sustainability. Although ether amines have been applied for floating the wide range of silicates, few investigations explored their adsorption behaviors on the micaceous minerals. In this study, flotation of phlogo-pite, biotite, and quartz (for comparison purposes) in the presence of Flotigam ® EDA (EDA) (com-mercial ether monoamine collector), at pH 10 was investigated through the single mineral micro-flotation experiments. Adsorption behaviors were explored by the contact angle, residual surface tension measurements, and zeta potential analyses. Micro-flotation outcomes indicated that the quartz floatability was more than phlogopite and biotite. In the presence of 30 mg/dm 3 EDA, their recoveries were 97.1, 46.3, and 63.8%, respectively. Increasing EDA concentration made a substantial increase in micaceous minerals' floatability. Adsorption assessments confirmed that increasing the EDA concentration resulted in higher adsorption of EDA onto the surface of micaceous minerals than the quartz (all by physical adsorption). Such a behavior could be related to the nature of mica-ceous minerals, including their layer structure and low hardness.
... The high recoveries attained at pristine pH and pH 9 may be attributed to dissolved cations (Fe 3+ and REE 3+ ) in solution which dictate hydroxy complex formation and subsequently the stability of the cation-hydroxamate complex which promotes minerals floatability. The unexpected high SiO2 recoveries may be attributed to surface activation by dissolved cations, which are crucial for the flotation of SiO2 particles in the presence of hydroxamates and other anionic collectors (Abaka-Wood et al., 2017;Fuerstenau and Somasundaran, 2003). ...
Conference Paper
The progressive depletion of high-grade ores or commercially viable deposits, allied to the growing demand for rare earth elements (REEs) in the world, has led to increased interest in the judicious use of unconventional resources such as mining tailings for REEs beneficiation. Froth flotation has been identified as one of the effective conventional methods for recovering REE minerals from ores. Different collectors have been employed in the flotation of REE minerals, with hydroxamates identified as one of the most effective. Many mining tailings contain appreciable amounts of REE minerals for which there is limited processing knowledge in the literature. In this work, the technical feasibility of recovering REE minerals from historic tailings was evaluated using hydroxamic acid as a collector during flotation. The effects of pulp pH, hydroxamic acid dosage, and depressants (sodium silicate and starch) dosage on REEs recovery were investigated. The results indicate that flotation recovery of REEs is pulp pH-dependent and is significantly affected by the particle and mineralogical characteristics of the feed. Furthermore, the experimental results revealed that the depressants used were effective in inhibiting the recovery of silicate minerals, with a marginal effect on iron oxides. Specifically, starch appears to be comparatively selective in inhibiting the recovery of both hematite and quartz. Chemical and mineralogical analyses on typical flotation concentrates obtained indicate that REE and iron oxide particles are concentrated in the recovered froths. The results also revealed that florencite, bastnäsite, monazite, and stillwellite could be effectively recovered and upgraded via hydroxamic acid flotation. These findings exhibit great potential for hydroxamic acid application in the recovery of REE minerals from mining tailings, although particle and mineralogical characteristics of the flotation feed limit separation selectivity.
Article
Wolframite is often associated with calcium bearing minerals, leading to low grade, while conventional anionic collectors are hard to realize their efficient flotation separation, thus the effective structural modification of cationic collectors provides a new insight into enhancing the comprehensive development of wolframite resources. In this study, a surfactant 3-dodecyloxy propyl amidoxime (DOPA) was designed and first used as the collector in flotation separation of wolframite from fluorite and calcite. Computational calculations basically proved the correctness of predictions about the performances of DOPA. Micro-flotation tests indicated that compared to DDA and conventional anionic collector benzohydroxamic acid (BHA), DOPA possessed superior collecting ability to wolframite and excellent selectivity against fluorite and calcite at low concentration, with no frother or activator employed, which is supposed to be an efficient collector for separating wolframite from calcium bearing minerals. The separation mechanisms of DOPA between wolframite and fluorite/calcite were further probed, revealing that besides the electrostatic attraction between DOPA and wolframite, DOPA could chemisorb onto wolframite surfaces by forming five-membered ring towards the surface cation site Fe or Mn, with no significant interaction observed on fluorite/calcite surfaces, resulting to the excellent separation performance.
Article
The effects of various activators on the flotation behaviour of lime-depressed pyrrhotite (FeS1.1) were investigated. The activation mechanisms were studied using electrochemical analysis, Fourier transform infrared spectroscopy, zeta potential measurements, and X-ray photoelectron spectroscopy. Micro-flotation results showed that the floatability of pyrrhotite declined sharply from 97.6% to 5.1% with the addition of lime. The flotation performance improved with the addition of both acid and salt activators; oxalic acid was the best activator, with a recovery > 97.0%. Ca- and Fe-based hydrophilic films formed on the lime-depressed pyrrhotite surface, preventing the adsorption and oxidation of the collector on the pyrrhotite surface. The activator increases its own surface potential to prevent the production of hydrophiles, and also removed hydrophiles from the pyrrhotite surface. In addition, the oxalic acid formed a stable chelate and removed hydrophilic material from the pyrrhotite surface. This study contributes to understanding the flotation mechanism and activation of lime-depressed pyrrhotite.
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Effects of ion species, cation valence, ionic strength and hydrated ionic radius on the zeta potential of quartz have been systematically studied through the measurement of zeta potential, sedimentation rate and aggregation observation. The results show that the interaction between hydrolysis components and quartz particles result in three critical points CR1, CR2, CR3. And results of sedimentation and aggregation observation are in good agreement with the changes of zeta potential in 0.1 M MgCl2, the maximum sedimentation rate being 99.26% at the pH = 10.85. When the pH is around 6.25 or 10.00, the sedimentation rate is relatively lower and the size of aggregation smaller. The adsorption of hydrolyzable multivalent metal ions on the quartz surface is a combination of three adsorption forms, namely electrostatic adsorption, hydroxyl complex adsorption and hydroxide precipitation adsorption. Then the hydrolysis properties of metal ions and the surrounding environment determine the action of the hydrolysis components and the main form of adsorption.
Article
The dodecylbenzenesulfonate isopropanolamine (DBIA) as a collector was first adopted in ilmenite flotation in this study, and its effect on the surface properties of ilmenite and titanaugite was investigated by contact angle and zeta potential measurements, X-ray photoelectron spectroscopy (XPS) analysis, and atomic force microscopy (AFM) detection. The flotation results showed that ilmenite obtained a superior floatability after being treated by DBIA, and that was ascribed to the improvement of the surface hydrophobicity of ilmenite. The zeta potential analysis indicated that the adsorption of DBIA onto ilmenite was stronger than that onto titanaugite. In addition, XPS detection revealed that the DBIA chemisorbed on the surface of ilmenite through reacting with Fe³⁺ active site, while weakly physisorbed onto titanaugite surface. Furthermore, the adsorption difference of DBIA led to a thick hydrophobic layer onto ilmenite surface but a sparse on the surface of titanaugite, which was vividly evidenced by the scanning results of AFM.
Article
Over the years there have been a number of instances describing a minimum in the flotation recovery of hematite in the alkaline pH region when oleate is used as the collector. These cases usually coincide with the use of a commercial oleate sample containing other fatty acids and/or salts as the collector. It is the purpose of this paper to provide experimental data involving the effects of pH on the flotation of a natural hematite sample using two collectors containing oleate and compare these data to changes in surface tension and bubble characteristics of aqueous oleate systems also as a function of pH. The main aim of this paper is to highlight and address this difference in hematite flotation behaviour with oleate solution characteristics and develop a better understanding of these interactions. It is proposed that this flotation minimum is associated with a reduction in both contact angle and bubble-particle flotation rate constant under these conditions, even though the surfactant solution chemistries would suggest that flotation should still be strong in this region.
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Recently, coal fly ash has become a potential candidate as a secondary resource of rare earth elements (REE). In this investigation, we studied the recovery of REE from fly ash from a commercial power plant. The specific aim was to assess the technical feasibility of recovering REE from the coal fly ash using conventional preconcentration methods, including gravity separation, magnetic separation, and froth flotation. The experimental results revealed that flotation achieved major gains in REE recovery and upgrading. However, during gravity and wet magnetic separation tests, the bulk of REE reported to the tailings. The results showed significant variations in the performance of the various beneficiation methods investigated. This study has confirmed that existing physical separation methods could be used to recover REE from coal fly ash prior to hydrometallurgical and pyrometallurgical processing, although some challenges persist.
Article
Although the effect of surface roughness on the floatability of a single mineral has been investigated extensively, a systematic study for the effect of surface roughness on the flotation separation of different minerals, e.g., flotation recovery, has never been dwelled. To fulfill this gap, in this study, the effect of surface roughness on the flotation separation of hematite from quartz was investigated with a series of experiments and detections. Micro-flotation experiments demonstrated that hematite particles with higher roughness resulted in higher recoveries for both hematite and quartz, but the improvement of hematite recovery was more significant, which promoted the flotation separation of hematite from quartz with a higher separation index (SI). Adhesion force measurements revealed that after interacting with 125 mg/L sodium oleate at pH 9, increasing nano-scaled roughness improved the hydrophobicity of hematite surface, and reduced the adhesion force of water droplet on hematite surface. Scanning Electron Microscope - Energy Dispersive Spectrometer observations confirmed that increasing nano-scaled roughness increased the number of fine quartz particles coating on hematite surface. Combined with the analysis of adhesion of water droplet and observation of fine particles coating on hematite surface, the effect of surface roughness on minerals flotation separation could be better understood.
Article
Temperature affects the flotation of quartz in the calcium/sodium oleate (NaOL) system, while there is a lack of understanding of its potential mechanism. Therefore, in this work, the flotation response of quartz to temperature was investigated via micro-flotation experiments, interface property analyses, and theoretical calculations. Flotation results demonstrated that increasing temperature contributed to higher flotation recovery of quartz, which enhanced the removal of quartz from hematite. Surface tension results revealed that higher temperatures lowered the critical micelle concentration (CMC) and surface tension of the NaOL solution, and thus enhanced its surface activity. Solution chemistry calculations and X-ray photoelectron spectroscopy (XPS) measurements confirmed that the increased content of Ca(OH)⁺ achieved by increasing temperatures enhanced the adsorption amounts of calcium species (acting as activation sites) on the quartz surface. Dynamic light scattering (DLS) measurements verified that the association degree of RCOO⁻ to form (RCOO)2²⁻ was strengthened. Furthermore, adsorption density measurements and molecular dynamics (MD) simulations confirmed that increasing the temperature facilitated NaOL adsorption toward the surface of the quartz, which was attributed to the stronger interaction between NaOL and the calcium-activated quartz surface at higher temperatures. As a result, quartz flotation was improved by increasing temperatures. Accordingly, a possible adsorption model was proposed.
Article
In this study, a self-assembled ternary mixed collector, Pb–BHA–NaOL (PBN), was used for the flotation of ilmenite from titanaugite. The internal assembly mechanism and interfacial adsorption behavior of the collector were comprehensively explored. The highest flotation separation performance (ilmenite recovery, 95.2% vs. titanaugite recovery, 12.6%) in the system was achieved at pH6. New evidence for various assembly behaviors in the collectors, including electrostatic attraction, chemical bonding, and hydrogen bonding, were found using zeta potential and in situ attenuated total reflectance Fourier transform infrared spectroscopy (in situ FTIR) combined with 2D correlation spectroscopic analysis. The difference between the adsorption configurations of PBN on the surfaces of the two minerals were visualized by time-of-flight secondary ion-mass spectrometry. X-ray photoelectron spectroscopy analyses confirmed that the high amount of Ca and Mg ions on the surface of titanaugite did not permit the collector species to form a strong bond with it, which was the main reason for the inadequate floatability of the mineral. Based on this analysis and discussion, different adsorption processes of Pb–BHA–NaOL on the surfaces of ilmenite and titanaugite are described in detail.
Article
Reverse flotation desilication is an indispensable step for obtaining high-grade fluorapatite. In this work, dodecyltrimethylammonium bromide (DTAB) is recommended as an efficient collector for the reverse flotation separation of quartz from fluorapatite. Its collectivity for quartz and selectivity for fluorapatite were also compared with figures corresponding to the conventional collector dodecylamine hydrochloride (DAC) via microflotation experiments. The adsorption behaviors of DTAB and DAC on minerals were systematically investigated with surface chemical analyses, such as contact angle determination, zeta potential detection, and adsorption density measurement. The results revealed that compared to DAC, DTAB displayed a similar and strong collectivity for quartz, and it showed a better selectivity (or worse collectivity) for fluorapatite, resulting in a high-efficiency separation of the two minerals. The surface chemical analysis results showed that the adsorption ability of DTAB on the quartz surface was as strong as that of DAC, whereas the adsorption amount of DTAB on the fluorapatite surface was much lower than that of DAC, which is associated with the flotation performance. During the floatation separation of the actual ore, 8wt% fluorapatite with a higher grade can be obtained using DTAB in contrast to DAC. Therefore, DTAB is a promising collector for the high-efficiency purification and sustainable utilization of valuable fluorapatite recourses.
Article
In this study, the atom substitutions that commonly affect the monazite lattice were considered as potential factors affecting the monazite electrophoretic mobility. The influence of light rare earth elements (LREE) substitutions and the presence of thorium, calcium, and silicate within the monazite crystal lattice was also examined using a natural monazite and synthetic cerium, lanthanum and neodymium monazite materials. Electrophoretic mobility measurements performed after treatment in an electrolyte solution equilibrated with air outline that LREE substitutions and other substitutions observed in the tested natural monazite did not affect the mineral surface properties. Conversely, the electrophoretic mobility of the synthetic monazites was found to be significantly affected by the amount of dissolved carbonate species present in the aqueous media. More precisely, carbonate species were found to decrease the electrophoretic mobility of monazite. Unlike tests performed with a solution equilibrated with air, the electrophoretic mobility of monazite treated in a CO 2 depleted electrolyte solution, under controlled atmosphere, were found erratic. This highlights the difficulty in obtaining reliable electrophoretic mobility data when the carbonate content in the supporting electrolyte solutions is not controlled.
Article
The production of rare earth elements (REE) is crucial in modern world. They are increasingly utilized in numerous applications, especially in clean- and high-tech sectors. The froth flotation is commonly considered for the concentrate production of REE, from their bearing ore, in the course of mine-to-metal production chain. However, various environmental drawbacks are present in conventional flotation processes such as large amounts of tailings, chemical reagents and surfactants all released in the surroundings of the operations. In our previous work, we introduced the Pickering emulsification as a novel approach, and cleaner alternative to the froth flotation, which potentially offers multiple ecologic and economic advantages, where we achieved a recovery of about 50% of REE, and an enrichment ratio of 2.9. Here, we investigated the effects of two essential process parameters such as mixing intensity (i.e., changing the impellers speed), and shear uniformity (i.e., comparing the performance of two hydrodynamically different impellers) to improve the process performance. We achieved an optimum rotational speed and energy consumption with a Maxblend impeller, where the size of the emulsion droplets showed much more uniform distribution. Thus, the recovery and the enrichment ratio rose up to 65% and approximately 3.85, respectively, after one single stage of emulsification. We have shown that such conditions outperform the froth flotation besides the environmental advantages.
Article
Sodium oleate (NaOL), as an important collector, has been extensively applied in oxide and silicate mineral flotation. The quantitative determination has to be analyzed for investigating its adsorption mechanism on the mineral surface. In this study, a novel method of Gas Chromatography Mass Spectrometry (GCMS) was proposed to precisely and stably measure NaOL concentration in diaspore and kaolinite flotation pulp through methyl esterification pretreatment. Compared with Total Organic Carbon (TOC) analyzer and High Performance Liquid Chromatography (HPLC), this method can avoid systematical and manual operation error effectively, benefitting from the internal standard application of heptadecanoic acid. The obtained linear relevance coefficient is 0.99902 and the standard deviation of adsorption results on the diaspore and kaolinite is much smaller than that of TOC and HPLC.
Article
of the points of zero charge (PZC) and isoelectric points (IEP) of various materials published in the recent literature and of older results overlooked in the previous compilations. The roles of experimental conditions, especially of the temperature, of the nature and concentration of supporting electrolyte, and of the type of apparatus are emphasized. The newest results are compared with the zero points reported in previous reviews. Most recent studies were carried out with materials whose pH dependent surface charging is already well-documented, and the newest results are consistent with the older literature. Isoelectric points of Gd(OH)3, Sm(OH)3, and TeO2 have been reported for the first time in the recent literature.
Article
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A tremendous amount of research has been done on refining the flotation process for iron ore and designing the reagents which go into it. This paper reviews the industrial practices and fundamental research surrounding iron ore flotation. The advantages and disadvantages of direct flotation, cationic reverse flotation, and anionic reverse flotation are reviewed. A novel stepped flotation technique is discussed for the treatment of carbonate-rich iron ores. The necessity of desliming to enable effective flotation is discussed in detail. Selective flocculation desliming is discussed in particular detail as it is the primary deslime methodology used in industry. This paper also describes a large variety of reagents commonly used or in development in each flotation route, covering collectors, activators, depressants, dispersants, flocculants, and frothers. The impact of the zeta potential and surface chemistry on flotation and deslime is also discussed. The aim of this paper is to provide a well-detailed, well-referenced source for the current status of iron ore flotation, and thus provide a useful guide to its future development and to further improve flotation performance for iron ore.
Article
Specularite is generally recovered by flotation, but its floatability is relatively weak. Activation is an effective method to improve the floatability of minerals. Therefore, finding an economic and effective activator to improve the recovery of specularite is an important research direction. In this study, lead nitrate as an activator was found and confirmed to improve the floatability of specularite. Its activation mechanism was further investigated by various analytical methods. The micro-flotation tests results showed that the recovery of specularite increased from 69.57% to 92.47% at a Pb²⁺ concentration of 3×10⁻⁵ mol/L, an approximately 23% increase, indicating that Pb²⁺ could obviously activate specularite. The SEM-EDS results illustrated that the content of Pb on the specularite surface apparently increased after specularite treatment with lead nitrate, which confirmed the adsorption of Pb species on the surface of specularite. Zeta potential results showed that the zeta potential positively shifted within the pH range from 3 to 11, which was beneficial to the occurrence of electrostatic adsorption and chemisorption between negatively charged oleate species and specularite. XPS results revealed that lead species mainly adsorbed on the O atoms of Fe-O and Fe-OH at the specularite surface, and Pb atoms became new sites to interact with sodium oleate. In addition, Pb²⁺ and Pb(OH)⁺ were the predominant components that interacted with the specularite surface and formed -O-Pb and Fe-O-Pb complexes, which considerably increased the number of reactive sites on the specularite surface. After oleate components interacted with Pb-modified specularite, a denser hydrophobic layer was generated on the surface of specularite, which intensified the floatability of specularite.
Article
To study the sodium oleate (NaOL) adsorption on quartz and its effect on flotation under weak-acidic conditions, the adsorption characteristics of NaOL on the surface of quartz were determined at pH = 6.5 by Fourier transform infrared spectroscopy (FTIR). The solution chemical calculation results show that NaOL exists as oleic acid (HOL) under weakly acidic conditions. The existence form and charge distribution of quartz and HOL were analyzed by Molecular Dynamics Simulation (MDS) using Materials Studio (MS) software, and the results showed that HOL is prone to the (101) and (100) surfaces of quartz under weak-acidic conditions by hydrogen bonding. The flotation verification test with NaOL as a collector was also performed under weak-acidic conditions. The flotation test led to a partial flotation of quartz into the froth products, reducing the grade of hematite direct flotation concentrate, which is consistent with industrial production.
Article
Common collectors for rare earth mineral (REM) flotation, which include carboxylates and hydroxamates, face problems such as being non-selective and sensitive to impurity ions. A type of ionic liquid (IL), tetraethylammonium mono-(2-ethylhexyl)2-ethylhexyl phosphonate ([N2222][EHEHP]), has been investigated previously for rare earth elements (REE) solvent extraction, and was proven selective and effective. In this work, [N2222][EHEHP] was evaluated as a collector in bastnäsite (a primary REM source for REE production) flotation for the first time. The results were compared with quartz and hematite, two common gangue minerals in REM deposits. Zeta potential measurements and Fourier-transform infrared spectroscopy (FT-IR) were completed to investigate the surface chemical properties involved in the flotation of these minerals using this collector. The findings were compared to microflotation results. FT-IR and zeta potential measurements suggest adsorption of the collector’s phosphonate group onto bastnäsite and hematite, likely through chemisorption; whereas for quartz, minimum microflotation recovery is likely due to no adsorption of IL on its surface. Microflotation results show higher collectability of [N2222][EHEHP] for hematite than bastnäsite, the latter only showed appreciable recovery at pH 5 with elevated dosage of IL (500 g/t). To achieve better separation, a two-stage flotation scheme was designed and evaluated by bench scale flotation on a synthetic mineral mixture. The concentrates and tails were analyzed by magnetic separation, and it was found that bastnäsite recovery over 90% with maximum upgrade ratio 1.7 could be achieved with elevated collector dosage.
Article
Mineral processing is one of the important methods of resource utilization, and flotation and leaching are the main methods of mineral processing. The conventional reagents used in these methods usually show that they may lead to health, environment, safety, and other related problems. In order to make these methods safer and cleaners, it is necessary to explore the use of more green and environmentally friendly reagents. Ionic liquids (ILs) and deep eutectic solvents (DESs) are known as green solvents because of their wide liquid temperature range, good solubility, high thermal and chemical stability, almost nonvolatile and low toxicity. The application of ILs and DESs as agents in mineral flotation and extraction of valuable metal can provide new alternatives to traditional methods and processes and realize green and clean production. ILs and DESs have been successfully used to high-efficient float some minerals that are difficult to float, such as rare-earth minerals, quartz, and quartz hematite, as well as carbonate asphalt during recent years. Here we focus on the application progress, existing problems, and development direction of ILs and DESs in mineral processing. We introduced characteristics of ILs and DESs, and the research progress of ILs and DESs in green flotation of rare-earth ore, quartz and quartz hematite. The research works of ILs and DESs in the green leaching of chalcopyrite, sulfide ore, gold, and silver ore is summarized. Interactions of ILs and DESs with common minerals of soil also discussed to help understand the impact of ionic liquids on soil and groundwater. Compared with the traditional flotation and leaching reagents, the amount of ILs and DESs used is obviously smaller, and the selectivity and efficiency are better than that of the traditional system. After further research and optimization, it is expected to be developed into a new efficient and green mineral processing technology.
Article
The electroacoustic technique has been successfully used to determine the zeta potential of concentrated aqueous suspensions for over thirty years. This article reviews its use in mineral processing, ceramics, zeolites, and other industrial minerals and in particular identifies the isoelectric points of these materials, as this parameter is crucial for determining colloidal stability and hence subsequent processing. Some benefits of this technique over the traditional electrokinetic measurement techniques are also highlighted. Finally, the application of the technique to polymer lattices is summarized.
Article
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The flotation of monazite and xenotime using sodium oleate as collector has been investigated using a modified Hallimond tube and also by a technique which measures particle-bubble adhesion strength. The zeta potential of both minerals was also measured. There has been a wide range of values reported in the literature for the point of zero charge (pzc) of monazite, the results here indicate the pzc occurs at pH 5.3. For xenotime the pzc was found to occur at about pH 3.0, there appear to be no other values reported. Maximum floatability of both minerals occurred at pH values greater than 7, where the mineral surfaces were negatively charged suggesting that the anionic oleate collector is not physically adsorbed. The flotation results were found to correlate well with the distribution of Re(OH)2+ species in aqueous solution, suggesting the collector is chemisorbed. The results also confirm previous indications that xenotime is slightly more floatable than monazite.
Article
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Interest in the synthesis of composite colloidal particles consisting of a core and shell with different compositions stems from the fact that such particles can be useful in processes where the properties of both core (e.g., size and shape homogeneity, ease of preparation in large amounts, magnetic characteristics, etc.) and shell (interfacial properties, porosity, chemical stability, etc.) might be of interest. However, the applicability must be based on a proper characterization of those properties. In this work, colloidal spheres of hematite (α-Fe2O3) were used as nuclei of mixed particles where the shell is yttrium oxide. The electrical properties of the aqueous interface are compared to those of the pure oxides by means of potentiometric titration of their surface charge and potential against pH, as a function of indifferent electrolyte concentration. It is found that the mixed particles efficiently mimic yttrium oxide, since the behavior of their surface electrical characteristics closely resembles that of the latter compound. Differences are found, however, that can be ascribed to an incomplete or porous coverage, but such divergences are of little significance when an overall comparison is carried out.
Article
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Capillary rise experiments of different liquids in glass capillaries and in columns of packed powders were carried out. The analysis of this rise was performed according to the classical Washburn’s equation in which the calculation of a constant term is needed in order to be able to determine contact angle of the considered liquid on the capillary wall or powders. However, it was observed that this constant term apparently varies as a function of the liquid used, in contradiction with Washburn’s approach. A more fundamental study of alkane rise into glass capillaries was carried out showing that this apparent variation is due to the variation of contact angles, which can take large values (up to 60°) as a function of velocity of the liquid front, although their expected value is 0°. Therefore, in the case of powders, different approaches to determine the real constant term with respect to particle size are proposed. Consequently, the use of Washburn’s equation for the determination of contact angles of liquids on these powders is also discussed.
Article
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A systematic comparison of Wilhelmy-balance tensiometry (WBT), tilting-plate goniometry (TPG) and captive-drop goniometry (CDG), using a variety of silane-treated glass surfaces of variable wetting characteristics is reported. WBT was assumed to be the benchmark of comparison (gold standard). Advancing angles measured by TPG and CDG were in statistical agreement with corresponding WBT measurements. In contrast, receding angles from both goniometric techniques were systematically higher than WBT.
Book
New Edition Now Covers Recycling, Environmental Issues, and Analytical Determination Employing four decades of experience in the rare metal and rare earths industry, the authors of Extractive Metallurgy of Rare Earths, Second Edition present the entire subject of rare earth elements with depth and accuracy. This second edition updates the most important developments from the past 10 years. It emphasizes advances made in rare-earth materials processing (converting a rare-earth metal, alloy, or compound to a device-ready material), breakthroughs in the area of rare-earth separation, and now includes a chapter on the recycling of rare earth elements from magnets, batteries, and phosphors among others, covering both manufacturing scrap or materials in end of life devices. Essential to Your Collection This second edition presents comprehensive, detailed, and up-to-date coverage that includes: •All aspects of rare earth extractive metallurgy •A status of rare earth extraction from various world resources •Flow sheets that can be used for rare earths separation, metal reduction, alloy making, refining and end product materials preparation •Techniques of various rare earths recycling options •An outline of environmental issues in rare earths mining and processing •Methods of rare earths determination and analyses of components and impurities in rare earth materials •Information extensively linked to primary literature with a complete listing of references •A narration of the changing scenario of world rare earth resources and possibility of their exploitation An indispensable resource, Extractive Metallurgy of Rare Earths, Second Edition explainsthe many aspects of rare earth extractive metallurgy clearly and systematically. The text reveals process implementation possibilities and research opportunities, and considers potential solutions to the challenges impacting this rapidly changing industry.
Article
Apart from being a resource for iron/steel production, the iron oxide minerals, goethite and hematite, are used in the paint, cosmetics, and other industries as pigments. Surface characteristics of these minerals have been studied extensively both in resource recovery by flotation and in the preparation of colloidal dispersions. In this current research, the wetting characteristics of goethite (FeOOH) and hematite (Fe2O3) have been analyzed by means of contact angle, bubble attachment time, and Atomic Force Microscopy (AFM) measurements as well as by Molecular Dynamics Simulation (MDS). Goethite is naturally hydroxylated and wetted by water, with a contact angle of 0°at all pH values. In contrast, the anhydrous hematite surface (001) was found to be slightly hydrophobic at natural pH values with a contact angle of around 50°. At alkaline pH hydroxylation of the hematite surface occurs rapidly and the hematite becomes hydrophilic. The wetting characteristics of the hematite surface then vary between the hydrophobic anhydrous hematite and the completely hydrophilic hydroxylated hematite, similar to goethite. The hydrophobicity can be restored by heating of the hydroxylated hematite surface at 60°C. The hydrophobic character of the anhydrous hematite (001) surface is confirmed by MDS which also reveals that after hydrolysis the hematite (001) surface can be wetted by water, similar to the goethite (001) surface.
Article
The selective coating of colloidal magnetite on hematite and bauxite for enhancing the magnetic separation techniques which depends on surface and chemical phenomena is studied. The mechanism of colloidal magnetite interaction with hematite and bauxite is investigated through electrokinetic and IR studies. The point of zero charge and electrophoretic mobilities of pure hematite, bauxite and colloidal magnetite are determined. The effect of various ions such as PO4-3, SiO3-2 and the surfactant such as sodium oleate on surface properties of hematite and bauxite are examined. IR spectroscopy studies indicate that oleate ions are chemically bonded with hematite while it is only physically adsorbed on the surface of bauxite at certain pH. The zeta-potential also correlates the chemical interaction of oleate on hematite. The separation of quartz from hematite and hematite from bauxite is carried out by applying selective colloidal magnetite coating followed by magnetic separation techniques. Hematite is separated in magnetic fraction for both the cases.
Article
This paper reviews rare earth minerals (monazite and xenotime) separation by flotation. A wide range of monazite and xenotime flotation test results are summarized including: reasons of variation in the point of zero charges on these minerals, the effects of various flotation conditions on zeta potential of monazite and xenotime, interactions of collectors and depressants on the surface of these minerals during flotation separation, relationship between surface chemistry of the minerals and different types of collector adsorptions and effects of the conditioning temperature on flotation of rare earth minerals. This review collects various approaches for the selective separation of monazite and xenotime by flotation and gives perspectives for further research in the future.
Article
Flotation tests conducted on the two Iron Duke samples using oleate showed that the presence of goethite adversely affected the flotation response of the hematite but contact angle measurements showed a higher hydrophobicity for the sample containing 25% goethite. Correcting the oleate addition for the changes in surface area still showed that the goethite reduced the flotability of the hematite. Aspects of processing iron ores containing goethite will need to be addressed as the high grade hematite ores are depleted, especially if flotation is employed in the beneficiation process.
Article
Handbook of Flotation Reagents: Chemistry, Theory and Practice is a condensed form of the fundamental knowledge of chemical reagents commonly used in flotation and is addressed to the researchers and plant metallurgists who employ these reagents. Consisting of three distinct parts: 1) provides detailed description of the chemistry used in mineral processing industry; 2) describes theoretical aspects of the action of flotation reagents 3) provides information on the use of reagents in over 100 operating plants treating Cu, Cu/Zn, Cu/Pb, Zn, Pb/Zn/Ag, Cu/Ni and Ni ores. * Looks at the theoretical aspects of flotation reagents * Examines the practical aspects of using chemical reagents in operating plants * Provides guidelines for researchers and engineers involved in process design and development. Significant progress in understanding the science of mineral processing over the past several decades has been made, especially in the development of chemical reagents. It should be stressed that chemical reagents used in flotation are the backbone of every flotation process. Therefore, the development of an effective reagent scheme for treatment of mineral ores is closely related to understanding the chemistry and reaction of the individual reagents in relation to characteristics of the particular ore to be treated.
Article
Bastnäsite is the chief valuable mineral in two of the world’s largest rare earth (RE) mineral deposits and is also found in a number of new RE deposits currently under development. This work used electrophoretic and electroacoustic zeta potential measurements to identify the interaction between bastnäsite and several different collectors. The results of these measurements were then compared with microflotation of bastnäsite and quartz, a common RE gangue mineral. Zeta potential measurements of bastnäsite determined the isoelectric point of bastnäsite to occur at approximately pH 6.3 (via electrophoretic measurement) and pH 8.1 (via electroacoustic measurement). Sodium oleate and Flotinor SM15 (a commercial phosphoric acid ester) are both shown to chemically adsorb onto the bastnäsite surface. Zeta potential measurements of bastnäsite with benzohydroxamic acid indicate significant adsorption, especially from pH 5 to pH 10. The microflotation results show that all three collectors were able to successfully recover bastnäsite. SM15 is the least selective collector as it floats both quartz and bastnäsite whereas benzohydroxamic acid is able to selectively float bastnäsite at pH 9. The recovery of bastnäsite using benzohydroxamic acid is also shown to be highly dependent on frother selection. The optimum pH of flotation for all three collectors occurs at pH 9.
Article
This paper investigated the physicochemical properties of allanite, a RE-silicate, by measuring zeta potential in the absence and presence of three different flotation collectors (benzohydroxamic acid, sodium oleate and dodecylamine). This data was then verified by microflotation experiments and with bubble-particle attachment pictures. The investigated properties of allanite were compared to those of quartz, a common gangue mineral in many RE deposits. The results of this work indicated that only dodecylamine was able to achieve a selective separation of allanite and quartz. This was accomplished by lowering the dodecylamine dosage so that only quartz was recovered by microflotation.
Article
Rare earth elements (REEs) comprise the fifteen elements of the lanthanide series as well as yttrium, and may be found in over 250 different minerals. These elements are required for many different applications such as high-strength permanent magnets, catalysts for petroleum refining, metal and glass additives and phosphors used in electronic displays. The only REE bearing minerals that have been extracted on a commercial scale are bastnäsite, monazite, and xenotime. These minerals may be beneficiated using gravity, magnetic, electrostatic and flotation separation techniques. Increased demand for the different products manufactured from REE has resulted in a constriction of supply from China, which currently produces 97% of the world’s rare earths, via export quotas. Many new rare earth deposits are currently being developed to help meet the demand void created by the Chinese export quotas, however most of these developing deposits include rare earth minerals for which there is limited processing knowledge. This paper examines the separation techniques that are currently employed for rare earth mineral beneficiation and identifies areas in need of further research.
Article
The role of surfactant adsorption in the wetting of relatively low-energy solids was evaluated from contact angle measurement using various aqueous surfactant solution-solid combinations. Analysis of the resulting data indicates that with many systems, pure liquids of low surface tension and aqueous surfactant solutions having the same surface tension do not produce the same contact angles; pure liquids often are better wetting agents. For hydrocarbon surfactants these effects are more significant for semipolar solids such as polymethyl methacrylate than for nonpolar solids. For a fluorocarbon surfactant, perfluoro-n-octanoic acid, the effects were found to be important for semipolar solids as well as nonpolar solids such as paraffin. These differences can be explained by invoking a lower adsorption of surfactants to the solid-liquid interface in comparison to the vapor liquid interface. Independent evidence from adsorption data justifies this explanation both for hydrocarbon and fluorocarbon surfactants. Using directly determined adsorption data on Graphon for both types of surfactants and surface tension values of the aqueous solutions involved, changes in the contact angle for Graphon were calculated. These simulated wetting curves reproduce many features of the observed wetting data for nonpolar solids for similar surfactants.
Article
The technique of microelectrophoresis was used to obtain electrochemical evidence of any specific adsorption of saturated and unsaturated fatty acids and other surfactants at the Al2O3 and Fe2O3—water interfaces. The adsorption of alkyl sulfonates and sulfates on both of these oxide colloids resulted from simple physisorption together with subsequent hydrophobic interaction at higher adsorption densities. Lauric acid also adsorbed on alumina by simple physisorption plus hydrophobic interaction whereas on Fe2O3 it showed not only hydrophobic adsorption but also specific chemisorption. In contrast, potassium octyl hydroxamate showed very strong specific chemisorption but no hydrophobic interaction. Oleic acid appears to chemisorb on both Fe2O3 and A12O3, but it is complicated by deterioration of the oleic acid.
Article
Solid-liquid separation and size classification of ultra-fine hematite particles (smaller than 1 μ m) were examined by using column flotation method. Ultra-fine hematite particles prepared by hydro-thermal aging method were suspended in water, followed by introducing argon bubbles into the column flotation cell. Since no surface active agent as a collector was added, particle surfaces were maintained in hydrophilic condition. Recovery of hematite particles changed significantly by regulating chemical condition of suspension such as pH, and electrolyte concentration. In addition, size classification of poly-dispersed hematite particles was achieved in acid condition by the same method of introducing bubbles. Small sized hematite particles were floated selectively by bubbles, while larger particles remained in the suspension. It was found that separation techniques using bubbles in column flotator were very useful for solid-liquid separation and size classification of ultra-fine particles from low concentrated suspensions. Driving forces of those processes are suggested to be interfacial chemical interactions such as hetero-coagulation between bubble and hematite particle, or homocoagulation of hematite particles.
Article
Electrokinetic and flotation studies were carried out on single particles of bastnaesite and monazite to develop a flotation scheme for selectively removing monazite in the rare earth bulk concentrate from the Baiyunebo mine, in China (60.7% rare earth oxides or REO, 75% as bastnaesite and 25% as monazite). Low additions of potassium alum were found to efficiently depress monazite at pH 5 without affecting the flotability of bastnaesite with the collector benzoic acid. The bulk concentrate was treated through this scheme, and 85% of the bastnaesite was recovered in a concentrate that assayed 69.5% REO and contained 97% bastnaesite. The depressing effect of potassium alum appeared to be due to the preferential adsorption of hydrolyzed aluminum species on monazite in comparison to bastnaesite.
Article
The conditions for the separation of monazite from zircon in anionic (oleic acid and sodium dodecyl sulphate) and cationic (dodecylaminium chloride) collector systems using sodium sulphide as regulator have been studied by means of electrokinetic measurements, direct flotation tests, and adsorption determination of the collector. The results obtained indicate that sodium sulphide affects the soap flotation of monazite and of zircon differently, hence it is useful in obtaining a high degree of selective separation. On the other hand, sodium sulphide is without selective action in alkyl sulphate and amine flotation. It seems that SH− and S2− ions are adsorbed preferentially onto a monazite surface with subsequent partial displacement of phosphate sites. Since the pKa of oleic acid is relatively high and that of SH− is higher than the pKa of HPO2−4, it is likely that the activation of monazite by sodium sulphide takes place by the attachment of oleate ions to the adsorbed activating S2− and SHsut ions, leading to the successful flotation of monazite. By contrast, sodium sulphide was shown to exert no influence on the adsorptive capacity for oleic acid and floatability of zircon, presumably owing to the extremely low pH of the isoelectric point of silicon sites.
Article
Wettability has been recognized as one of the most important properties of fibrous materials for both fundamen- tal and practical applications. In this study, the plasma induced grafting of acrylic acid (AAc) was applied to improve the wettability of the electrospun poly(vinylidene fluoride) (PVDF) nanofiber membranes. The diameter and chemical struc- ture of the modified PVDF nanofibers were characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR). Nitrogen adsorption based on BET (Brunauer, Emmett and Teller) principle was employed to measure the specific surface areas and porosities of the modified nanofiber membrances. The contact angles of the modified membrane were evaluated by drop shape analysis (DSA) and the modified Washburn method. The dependence of contact angles on specific surface area and porosity was also discussed in this paper. Water adsorptions were used to evaluate the dynamic wetting behavior of the grafted membranes by a dynamic adsorption apparatus (CDCA100-F). The experimental results revealed that the wettablity of the modified PVDF membrane was significantly affected by both surface and porous contact angles.
Article
A comprehensive review is presented of the extractive metallurgy of rare earths. The topics covered are: world rare earth resources and production; ore processing and separation of individual rare earths; reduction, refining, and ultrapurification of rare earth elements; methods for rare earth materials analysis; and a selection of the numerous rare earth applications. World rare earth reserves are abundant and would last for well beyond the next century. However, all of the 16 naturally occurring rare earth elements are not equally distributed in the ore minerals. This, compounded with the problems specific to the isolation and recovery of each of the rare earths, sets the stage for an unequal rare earth availability. The close chemical similarity of rare earths looses its importance when divergent physical properties determine the processes for rare earth element reduction and refining. The rare earth metals, alloys, and compounds have been as pure as could be determined. Finally, the commercial demand for a rare earth has often been out of phase with its chemical availability. The review addresses itself to these points while providing a summary of the substantial body of information presently available on the extractive metallurgy of rare earths.
Article
The adsorption of sodium oleate and potassium octyl-hydroxamate onto the rare-earths minerals monazite and bastnaesite was investigated through microflotation experiments, zeta potential determinations and infrared spectroscopy.The monazite and bastnaesite samples were purified in the laboratory reaching, respectively, final grades of 68.7 and 45.3 % RE2O3 + ThO2.The results confirm that sodium oleate chemisorbs onto bastnaesite and suggest a physical adsorption mechanism of this reagent onto monazite. Despite the lack of a full confirmation from FTIR spectrometry, there is a possibility of oleate chemisorption onto monazite in the pH range above the isoelectric point.A chemical adsorption mechanism was established for the interaction between octylhydroxamate and both minerals.
Article
Contact angles (θ wicking) with apolar and polar liquids on monosized synthetic cuboid hematite particles were obtained by thin layer wicking. Contact angles (θ adv) of these liquids on films of hematite particles were also measured by the advancing drop method. The values of θ wicking and θ adv coincided within a few degrees. Thus, the thin layer wicking method and the direct contact angle approach appear equally valid.
Article
The advancing water contact angles of 17 different iron ores have been measured. The primary constituents of the ores were hematite and goethite and compositions varied from 98% hematite through to 87% goethite. The measured ore contact angles ranged from 0° to 74°. An approximately linear correlation was found between the contact angle and the ore composition given by, θ=45x+8 (±10°), where θ is the contact angle (°) and x is the volume fraction of hematite in the ore. Hence, the hydrophobic character of the ore was observed to increase with increasing hematite and decreasing goethite content. These results are important for mineral processing operations such as pelletising and flotation. In both cases, water contact angles play a critical role. For pelletising of porous iron ore fines, the contact angle influences the amount of liquid absorbed into the pores and also the amount of interparticle liquid required to promote granulation.
Article
The wettability of a powder is important, especially in chemical and pharmaceutical technologies when considering the manufacturing process and the properties of the final product. However, contact angle methods for powders are problematic. The common measurement techniques are the sessile drop method and the liquid penetration method. In this work the determination of contact angles of powders by liquid penetration is considered. In particular, we investigated the influence of the sample preparation and sampling device on the wetting process. A bulk with constant properties during the measurement must be guaranteed. We postulate a packing procedure to obtain reproducible measurements by ensuring constant powder properties.
Article
The homologous series of saturated fatty acids investigated in this study generally show a steady gradation of properties with chain length. The solution pKa values were assumed constant at 4.9, however reported pKa values could be lower or higher. Hematite flotation response and surface pressure for aqueous solutions of these fatty acids were measured as a function of pH. For the shorter chain fatty acids, the undissociated acid was shown to be the predominant surface active species with flotation, supplemented by the physical adsorption of acid anions as the chain length increased. The reduced solubility of the longer fatty acid carbon chains made these reagents ineffective as flotation agents. The maximum flotation response of hematite using tetradecanoic acid corresponded with the precipitation edge of the reagent. The results show that the values of surface pressure of the surfactants are not always a good indication of their effectiveness as flotation collectors.
Article
Hydrophilic films of phospholipids were deposited onto plastic substrates (surface-treated for cell cultures) and shown to adhere sufficiently for measuring their interfacial properties by the method of contact angles. Both by absolute magnitude and by their dependence on temperature, the interfacial properties of these phospholipid films were indistinguishable from those determined for black lipid bilayer membranes with a different method by other authors. According to both their vesicular micromorphology and water permeability, the surface films can be interpreted to consist essentially of multibilayer vesicles with the hydrophilic groups facing outward. Treatment of these films with cell-culture medium containing calf serum results in changes of interfacial properties that are very similar to those effected on virus-transformed 3T3 cells (earlier work). These interfacial effects may be attributed essentially to serum proteins (such as albumin) adsorbing to phospholipid or cellular surfaces. The interfacial properties of nontransformed 3T3 cells are much less affected by serum treatment (earlier work), which correlates closely with their higher serum requirement for proliferation. Comparison of these results with those on the interfacial effects of serum on phospholipid films suggests that at least part of the proliferation-stimulating effect of serum is mediated by changes of interfacial properties of cell membranes upon adsorption of serum proteins such as albumin. Treatment of phospholipid films with concanavalin A, an inhibitor of cell proliferation, does not result in effects on their interfacial properties correlating with those on cellular membranes. This confirms previous suggestions that the latter depends on specific binding of convanavalin A to specific carbohydrates on the cell membrane.
Article
The controversy with respect to measurement and interpretation of contact angles are shown to be due to violations of some or all of the assumptions made in all energetic approaches. For a large number of polar and nonpolar liquids on different solid surfaces, with appropriate experimental techniques and procedures, the liquid-vapor surface tension (LVST) times cosine of the contact angle depends only on the LV and the solid-vapor STs. Equations following these experimental patterns and which allow the determination of solid surface tensions from contact angles are discussed.
Article
The adsorption densities of Na+, Cl− and dodecylammonium chloride (DAC) at the quartz-solution interface have been determined as a function of pH and electrolyte concentration. This adsorption study is supplemented by streaming potential measurements. A close relation between changes in adsorption density and ζ-potential is revealed. The experimental results in the absence of DAC are shown to be consistent with the Grahame-Stern model of the double layer when specific adsorption is negligible. Under these conditions the electrokinetic data are seen to be in good agreement with the Lyklema-Overbeek concept of a slipping layer of variable thickness and the implied dependence of ζ on electrolyte concentration.In acid and neutral solutions the organic cation (DDA+) behaves in a manner analogous to that of Na+. The observed difference in the adsorption and electrokinetic behavior of quartz in alkaline solutions of NaCl only and in alkaline solutions containing DAC is ascribed to the strong adsorption of the free organic base which has no equivalent in inorganic solutions. The charge reversal in DAC solutions, especially at basic pH, is explained by the enhanced adsorption of DDA+ because of the strong adsorption of the uncharged molecules through the added Van der Waals interaction between charged and uncharged organic species. At high pH (~ 12) this charge reversal is absent because of the low limiting concentration of DDA+ (~ 10−6 M) and the competition of Na+ for the negatively charged surface.
Article
Contact angles can be of great value; however, making meaningful contact angle measurements and interpreting those measurements is complex. For years, researchers have addressed a wide variety of issues concerning contact angles. Some questions have been qualitatively answered; others remain open. In this paper, we focus on three issues which are particularly important for the measurement and use of contact angles: the appropriate definitions and use of macroscopic and microscopic contact angles, a brief survey of the length scales relevant to phenomena controlling contact angles, and the role of vibrations in determining contact angles. We emphasize contact angle issues relevant to heterogeneous surfaces, specifically, ambient surfaces prevalent in nature and industry.
Article
This paper presents a study on the shear flocculation of fine (38 μm) hematite using dodecylamine acetate and Aero 801 (a mixture of petroleum sulfonate and mineral oil) as collectors. The effects of pH, collector concentration and stirrer speed were investigated. In addition, contact angle and flotation recoveries of the mineral were determined at different pH values. The results indicated that shear flocculation was possible over a wide pH range with the amine, whereas it was restricted to a narrow pH range (2.5–3.5) with Aero 801. This was attributed to the better hydrophobicity of the mineral, indicated by higher flotation recoveries and contact angles within the same ranges.
Article
Data were obtained with hematite with octyl hydroxamate and oleate as collectors to determine the mechanism of collector adsorption and also to establish the roles that conditioning time and temperature assume in this system. The presence of hydroxy complexes of iron are apparently necessary for chemisorption of collector to occur, and it appears as if extended conditioning times and elevated temperature promote greater dissolution of the mineral and hence greater concentrations of hydroxy complexes. Data were also collected with two natural hematitic ores. With one ore that was ground to 70% - 15p, an addition of 0.4 Ib per ton hydroxamate resulted in a final concentrate recovery of 86% at a grade of 64% iron. Satisfactory concentrate grade could not be obtained with fatty acid under these conditions. The effect of conditioning time prior to the addition of collector was also examined with another ore. When the ore was conditioned for 3 min, 19% of the iron was recovered in the concenbrate at a grade of 67% Fe. With a conditioning time of 7 min, 73% of the iron reported to the concentrate at a grade of 62% Fe. These products were obtained with an addition of 0.2 lb per ton hydroxamate. This ore also responded well to flotation with fatty acid. Journal Article
Article
We compared five different methods, static sessile drop, dynamic sessile drop, Wilhelmy plate, thin-layer wicking, and column wicking, to determine the contact angle of colloids typical for soils and sediments. The colloids (smectite, kaolinite, illite, goethite, hematite) were chosen to represent 1:1 and 2:1 layered aluminosilicate clays and sesquioxides, and were either obtained in pure form or synthesized in our laboratory. Colloids were deposited as thin films on glass slides, and then used for contact angle measurements using three different test liquids (water, formamide, diiodomethane). The colloidal films could be categorized into three types: (1) films without pores and with polar-liquid interactions (smectite), (2) films with pores and with polar-liquid interactions (kaolinite, illite, goethite), and (3) films without pores and no polar-liquid interactions (hematite). The static and dynamic sessile drop methods yielded the most consistent contact angles. For porous films, the contact angles decreased with time, and we consider the initial contact angle to be the most accurate. The differences in contact angles among the different methods were large and varied considerably: the most consistent contact angles were obtained for kaolinite with water, and illite with diiodomethane (contact angles were within 3 degrees); but mostly the differences ranged from 10 degrees to 40 degrees among the different methods. The thin-layer and column wicking methods were the least consistent methods.
Article
Advancing contact angles measured on compacts of several drugs by the sessile drop method and also by penetration through a column of drug granules were used to find the critical surface tension of the drugs. After liquid was delivered at a very slow rate, the contact angle of sessile drops decreased with time, but use of a consistent method of timing always led to the same value for critical surface tension. Results from penetration studies and work on compacts were in agreement, provided that the surfaces of the compacts were smooth and highly reflective. Critical surface tension of the six drugs, three analgesics and three sulfonamides, ranged from 31 to 33 dynes/cm. The critical surface tension of mixtures of phenacetin and microcrystalline cellulose was not a linear function of the relative surface fractions of the two materials. If the surface contained 25% or more of phenacetin, the critical surface tension barely differed from that of pure phenacetin.
Article
We discuss the equilibrium condition for a liquid that partially wets a solid on the level of intermolecular forces. Using a mean field continuum description, we generalize the capillary pressure from variation of the free energy and show at what length scale the equilibrium contact angle is selected. After recovering Young's law for homogeneous substrates, it is shown how hysteresis of the contact angle can be incorporated in a self-consistent fashion. In all cases the liquid-vapor interface takes a nontrivial shape, which is compared to models using a disjoining pressure. Comment: 12 pages, 6 figures
Reagents Chemisorption on Minerals as a Process of Formation of Surface Compounds with a Coordination, XII International Mineral Processing Congress
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Contact angle and wetting properties