Article

Recovery of Rare Earth Metals as Critical Raw Materials from Phosphorus Slag of Long-term Storage

Authors:
  • The Institute of Metallurgy and Ore Benefication
  • Institute of Metallurgy and Ore Benefication, Kazakhstan, Almaty
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Abstract

The present research is directed to processing of slag originating during the yellow phosphorus production. Slag was investigated using a complex of physical and chemical treatment methods. The presence of the following elements of rare earth group in phosphorus slag was identified as: Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Ho, Tm, Yb, Lu. Thermodynamic calculation of reactions probability of phosphorous slag components interaction with nitric acid was made. Nitric-acid leaching of phosphorus production slag for extraction of rare earth metals (REMs) was investigated. Silicon containing cake obtained after leaching was fond to be suitable for precipitated silicon dioxide production. Behaviour during the leaching of associated components such as calcium, aluminum, and iron were studied. The following optimum parameters were selected for leaching studies: nitric acid concentration is 7.5 mol/dm3; solid-to-liquid ratio is 1:2.6-3; temperature is 50-80 ºС; process duration is 1 hour; pulp stirring rate is 500 rpm and the recovery of rare-earth metals, calcium, aluminum and iron into the solution were seen to be 85 %, 98 %, 80.7 %, and 11.8 %, respectively. Cake produced as a result of leaching contained ~80-85 % of amorphous SiO2. A solution after phosphorus slag leaching was processed with the solvent extraction methods to concentrate and separate it from basic macroimpurities. After precipitating of REMs oxalates from strip liquor and calcination of the precipitate a concentrate had been obtained, which contained ~17% of ∑REMs oxides.

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... Up to date, many scientists and research teams are involved in such issues [18]- [21], however, the issue has not been sufficiently studied from this point of view [22]- [26]. Thus, Institute of Geotechnical Mechanics named by N. Poljakov of National Academy of Sciences of Ukraine (Dnipro, Ukraine) employees of Ukraine has performed the studies related to gas-dynamic assessment of coal and rock massif [27]- [28], and particular attention is paid to methane release into the face of underground mine workings, to the gas pressure in the stratum, and other factors [29]- [31]. ...
... It can also be noted that formulas (28) and (29) are completely analogous to formulas (21) and (22), respectively. The only difference is in the recording of material constants. ...
... In turn, the solubility of REEs in phosphoric acid decreases. Regarding the latter phenomenon, the Gibbs energy of the REEPO 4 dissolution with nitric acid increases with increasing temperature [31]. Investigations carried out by CETINER [30], in fact, demonstrated that the solubility reactions of LREE phosphates are exothermic. ...
Article
In order to provide practical fundamental data for rare-earth elements (REEs) recovery from phosphoric acid and to better understand REEs behavior during the phosphoric acid evaporation process, the solubilities of REEs in phosphoric acid with various concentrations of phosphorus at different temperatures were measured. A simple linear model between REEs solubility and phosphoric acid concentration is built and the experimental data are found to fit it very well (R²>0.94). Hydrogen-ion concentration is found to be the predominant factor controlling the solubility of REEs in phosphoric acid. In addition, the solubility of REEs in phosphoric acid is found to sharply decrease with increasing temperature, which can be attributed to the increase of the Gibbs energy of the REEPO4 dissolution reaction or the restraint of the disassociation of phosphoric acid molecules owing to the elevated temperature.
... Existing technologies for CRMs production are briefly described in Table 2. Most of these technologies are for primary ores. Some applications for secondary sources such as industrial waste and mine tailings exist (Abisheva et al., 2017;Binnemans et al., 2015;Figueiredo et al., 2018;Innocenzi et al., 2014;Jorjani and Shahbazi, 2016;Peelman et al., 2016), but they should be treated as emerging technologies. Significant further development of these new technologies is required before they are suitable for industrial-scale usage (Kinnunen and Kaksonen, 2019). ...
Article
The mining industry produces large volumes of mine tailings – a mix of crushed rocks and process effluents from the processing of mineral ores. Mine tailings are a major environmental issue due to implications related to their handling and storage. Depending on the mined ore and the process used, it may be possible to recover valuable elements from mine tailings, among other critical raw materials (CRMs) like rare earths, vanadium, and antimony. The aim of this study was to investigate the techno-economic feasibility of producing critical raw materials (CRMs) from mine tailings. Data from 477 Chilean tailings facilities were analyzed and used in the techno-economic assessment of the valorization of mine tailings in the form of CRMs recovery. A review of applicable technologies was performed to identify suitable technologies for mine tailings processing. To assess the economic feasibility of CRMs production, net present value (NPV) was calculated using the discounted cash flow (DCF) method. Sensitivity analysis and design of experiments were performed to analyze the influence of independent variables on NPV. Two options were assessed, rare earth oxides (REOs) production and vanadium pentoxide (V2O5) production. The results show that it is possible to produce V2O5 with an NPV of 76 million US$. In the case of REOs, NPV is positive but rather low, which indicates that the investment is risky. Sensitivity analysis and the ANOVA run using the design of experiments indicated that the NPV of REOs is highly sensitive to the price of REOs and to the discount rate.
... Grinding of mineral feed with inclusions of soft minerals is subject to the laws of selective grinding as in hydrometallurgy [18]- [20]. In presence of a liquid phase, the pelite fraction of soft minerals reduces the concentration of stresses at the points of contact between the coarser particles, turning concentrated loads into distributed ones. ...
... Recent advances in hydrometallurgical operations have paved way for the feasibility of REE extraction from low grade unconventional resources such as mine tailings, fluorescent lamps, and permanent magnets (Binnemans et al., 2013;Jha et al., 2016;Tan et al., 2015;Wang et al., 2011;Yang et al., 2013). For example, Abisheva et al. (2017) processed slag (< 0.3 wt% TREO) generated during the treatment of phosphorite ores for REE recovery. Nitric acid leaching of the slag produced a leachate of total REE concentration of 0.19 g/dm 3 at 85% recovery, along with 98% Ca, 80.7% Al, and 11.8% Fe. ...
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.
... Some researches on reutilization of slag involve multiple applications such as recovery of metal values and subsequent reutilization of slag in ceramic industry [76][77][78][79][80]. In one of such attempts, Sarfo et al. used a pyrometallurgical method to recover metal values from copper slag and while producing a slag for further in ceramic industry at the same time [81]. ...
Article
Ever-increasing energy costs and environmental restrictions have compelled researchers to focus on the reutilization of vast amounts of industrial by-products such as blast furnace slag and steelmaking slag, in energy extensive and material extensive industries such as iron-steel production and construction. Attempts to reutilize these waste materials all around the world have yielded successful results up to date, such that, in some of these attempts they even surpassed their intended use as blend or replacement materials and became serious rivals to their industrial counterparts. Various ways to reutilize these waste materials have been explored up to date, including waste heat recovery, clinker substitute in cement production, and a number of comparatively more value added applications. The ongoing attempts have come to a point that pushes the limits for more technological uses such as alternative ceramic coating materials in surface engineering applications. In this regard, this review study aims to provide an overview of and a collective approach to various uses of blast furnace and steelmaking slag in diverse applications and fields, with a view to provide insight into the current attempts to optimize or improve their use, as well as emerging trends as to the potential use of these waste materials in higher value-added applications.
... In this context, it can be stated that, the radioactive wastes were not only accumulate as a result of uranium mining, but also during its processing resulted in release of radioactivity into the environment and soils [2,3] Solvent extraction is one of standard process that currently used for the removing of metal ions with a high selectivity [4][5][6][7], this technique was especially used for the high metal concentration as the same as precipitation technique. The most efficient function groups in the solvent extraction are that based on phosphorus moieties as alkyl phosphates [5,[8][9][10][11][12], and phosphoric acid derivatives [13]. A wide variety of functional groups characterized by a high affinity but also selectivity toward uranium even in low concentration from high saline solution. ...
Article
Full-text available
Promising green leaching technique was used by Humic acid (HA) for removing uranium from Abu Zeneima spent residue for environmental safety and cost-effective leaching. The studied residue is outlet from vat leaching process using sulfuric acid leaching of carbonaceous shale ore material with initial uranium assays 185 ppm, which representing a hazardous waste. The overall leaching efficiency assaying 93% of uranium using humic acid leaching at curing temperature 70 °C, 13% HA with S/L ratio of 1/1.5 for 15 day. Kinetic study of leaching process proved diffusion controlling mechanism with activated energy 10.297 kJ/mol. Finally; 98% of uranium was extracted using Amberlite IRA- 400 resin with purity of 97.3%.
... The amazing development of High-tech industry sectors (electronic devices, special magnets, screens, etc.) induces a growing demand for precious and strategic metals like rare earth elements (REEs). More specifically, the rarefaction and the geopolitical pressure of the resource for REEs have driven many governmental and intergovernmental agencies to publish recommendations or incentive politics [1] for promoting the recycling of these metals from wastes (DEEs) [2][3][4][5][6][7] and their recovery from secondary sources (sub-products) [2,[8][9][10][11][12]. ...
Article
The one-pot synthesis of algal biomass/ polyethyleneimine beads, ALPEI (electrostatic interaction followed by calcium ionotropic gelation), produces a stable sorbent whose sorption properties for rare earth elements (REEs) are significantly improved by functionalization. The grafting of sulfonic groups (S-ALPEI), which have high affinity for REEs, increases sorption capacities as high as 2.68 mmol Sc g⁻¹, 0.61 mmol Ce g⁻¹ and 0.53 mmol Ho g⁻¹, at pH close to 4 (equilibrium pH). Sorption isotherms are fitted by the Langmuir equation for scandium and cerium; for holmium, the Freundlich and the Sips equations show better fits. Sorption occurs within 30–40 min; kinetic profiles are fitted by the pseudo-second order rate equation and the Crank equation (resistance to intraparticle diffusion). The sorbent has a marked preference for Sc(III) against Ce(III) and Ho(III) (confirmed by selectivity tests). The sorbent is also selective for REEs against alkali-earth elements. The three metals are readily desorbed (within 20–30 min) using HCl/CaCl2 solution. Desorption remains higher than 99% for 5 cycles while sorption performance is decreased by less than 6% at the fifth cycle. The sorbent is tested for the recovery of valuable metals from red mud solution at different pH values. Despite the large excess of heavy metals in the industrial solution, S-ALPEI shows a good affinity for REEs at pH close to 3.46 with important enrichment factors (in the range 19–118 depending on the metal). The material is fully characterized by BET, TGA, FTIR, XPS, elemental analysis, titration. The sorption involves different mechanisms (on amine and sulfonic groups) including electrostatic attraction and chelation depending on pH and metal speciation.
... The total atomic fraction in the precipitate reaches up to 13% (i.e., 51% in weight). A final step of calcination would produce a concentrate of REEs oxides [62]. Globally, the process allows separating REEs from BMs. ...
Article
Alginate-PEI beads are functionalized by phosphorylation and applied for the sorption of Nd(III) and Mo(VI). The successful grafting of phosphoryl groups (as tributyl phosphate derivative) is characterized by FTIR and XPS analysis, elemental analysis, titration (pHPZC), TGA, BET and SEM-EDX analyses. The multi-functional characteristics of the sorbent (i.e., carboxylic, hydroxyl, amine and phosphate groups) contribute in the binding of metal ions having different physicochemical behaviors. The sorption of Nd(III) is strongly increased by phosphorylation, while for Mo(VI) the enhancement is rather limited. Optimum sorption occurs at pH 3–4: maximum sorption capacity reaches up to 1.46 mmol Nd(III) g⁻¹ and 2.09 mmol Mo(VI) g⁻¹; sorption isotherms are fitted by the Langmuir equation. The equilibrium is reached within 30–40 min and the kinetic profiles are simulated by the pseudo-first order rate equation. The coefficients of the effective diffusivity are close to the self-diffusivity of Nd(III) and Mo(VI) in water; as a confirmation of the limited impact of resistance to intraparticle diffusion in the kinetic control. The sorbent is selective for Nd(III) over Mo(VI) and other alkali-earth or base metals (at pH close to 2.5–3). Metals can be readily desorbed using 0.2 M HCl/0.5 M CaCl2 as the eluent. The loss in sorption does not exceed 5% at the fifth cycle, while desorption remains complete. A series of treatments (including acidic leachate, cementation, precipitation, sorption and elution) is successfully applied for the recovery of rare earths from Egyptian ore; with enrichment in the oxalate precipitate of Nd(III), Gd(III), Sm(III) and Eu(III).
... Kazakhstan-originated PG differs from PG from abovementioned countries by being a hazard class 4 material [17] and having low radiation background, which makes it potential feed for making construction materials and fertilizers as well as extraction of REE and strontium salts [18]. There is a lot of research on complex recycling and REE extraction out of PG, which mostly suggests obtaining purified CaSO 4 and other products [19][20][21][22]. ...
Article
This article looks into process of supercritical-CO2 phosphogypsum (PG) conversion, which is production residue after making mineral fertilizers by "Kasphosphate" LLC. Nowadays, over 30 million tons of PG have been accumulated in Kazakhstan; its background radiation is low enough to recycle it into valuables such as construction materials, rare earth elements and strontium salts. Complete factorial experiment method was used to describe conversion process; conversion of PG into CaCO3 was optimized using simplex method. Conversion optimization outcomes show possibility of using fewer reagents and shortening conversion process compared to existing technologies. Conversion degree is 87% after 10 min at 33 °С. Conversion was carried out at semi-industrial supercritical equipment with maximum CO2 flow rate up to 5000 g/min and integrated CO2 recirculation system. Characteristics of initial PG samples and conversion products/semi-products were done using X-ray phase analysis, scanning electron microscopy, atomic absorption spectroscopy, ICP-MS, and gravimetric procedure. In order to obtain purer CaCO3 PG was cleared of water-soluble impurities beforehand. As conversion result, finely dispersed CaCO3 and Ca(HCO3)2 as well as Na2SO4 solution were obtained.
... The ever-increasing demand and limited resources for the extraction of these elements have motivated the development of new and sustainable methods for separation and recovery of REEs. The current recovery methods are precipitation [7], electrochemical methods [8], adsorption [9,10], solvent extraction [11][12][13], ion-exchange [14], and ionic liquid systems [15,16]. However, some of these technologies generate chemical contamination and require high energy consumption causing environmentally damages and increase in operational costs. ...
Article
Full-text available
Rare earth elements (REEs), which include lanthanides as yttrium and europium became crucial in the last decade in many sectors like automotive, energy, and defense. They contribute to the increment efficiency and performance of different products. In this paper nanofiber membranes have been successfully applied for the selective recovery of Eu(III) and Y(III) from aqueous solutions. Polyacrylonitrile (PAN) electrospun nanofibers were impregnated with a commercial organic extractant, Cyanex 272, in order to increase their affinity to rare earth metals ions. The coated nanofibers were characterized by SEM, ATR-FTIR, and TGA. Firstly, the adsorption of Eu(III) and Y(III) were evaluated in batch mode. Experimental data showed that the adsorption of Y(III) and Eu(III) corresponds to pseudo-second order model, with Langmuir sorption model being the best fit for both target ions. The results demonstrated that the adsorption capacity was high, showing a maximum capacity of 200 and 400 mg/g for Y(III) and Eu(III), respectively. Additionally, the presence of interfering ions does not show significative effects in the adsorption process. Finally, experiments in continuous mode indicated that the adsorption of the target elements is close to 100%, showing that PAN-272 is a promising material for the recovery of earth metal ions.
... Solvent extraction is a standard process currently employed for the removal of REEs from acidic leachates [18][19][20][21], especially for solutions containing high metal concentrations. Most of these highly efficient extractants are based on phosphorus reagents such as alkyl phosphate [19,[22][23][24][25][26], alkyl phosphoric acid [27][28][29], alkyl phosphine oxide [30,31], phosphonium ionic liquids [32,33] and organophosphonic extractants [34][35][36][37]. The strong affinity of phosphorus-based extractants for rare earth easily explains that a strong effort has been made for designing synthetic resins bearing phosphorus-based reactive groups such as Tulsion CH-96 and T-PAR resins [38,39], Tulsion CH-93 [34], Purolite S957 and Diphonix [40] or metal-organic frameworks [41]. ...
Article
Full-text available
High-tech applications require increasing amounts of rare earth elements (REE). Their recovery from low-grade minerals and their recycling from secondary sources (as waste materials) are of critical importance. There is increasing attention paid to the development of new sorbents for REE recovery from dilute solutions. A new generation of composite sorbents based on brown algal biomass (alginate) and polyethylenimine (PEI) was recently developed (ALPEI hydrogel beads). The phosphorylation of the beads strongly improves the affinity of the sorbents for REEs (such as La and Tb): by 4.5 to 6.9 times compared with raw beads. The synthesis procedure (epicholorhydrin-activation, phosphorylation and de-esterification) is investigated by XPS and FTIR for characterizing the grafting route but also for interpreting the binding mechanism (contribution of N-bearing from PEI, O-bearing from alginate and P-bearing groups). Metal ions can be readily eluted using an acidic calcium chloride solution, which regenerates the sorbent: the FTIR spectra are hardly changed after five successive cycles of sorption and desorption. The materials are also characterized by elemental, textural and thermogravimetric analyses. The phosphorylation of ALPEI beads by this new method opens promising perspectives for the recovery of these strategic metals from mild acid solutions (i.e., pH ~ 4).
... Significant areas of agricultural land are allocated for phosphogypsum storage [10,11]. Thus, phosphogypsum dumps of PJSC "Rivneazot" cover an area of 58 hectares and their total volume is 15.2 million tons [7]. ...
Article
Full-text available
The article contains research materials on the storage of man-made deposits, including phosphogypsum dumps. The consequences of long-term operation of phosphogypsum dumps and their negative impact on the environment have been established. The quantitative content of microelements to the soil within the storage of technogenic phosphogypsum deposit was determined. Graphical dependences of phosphorus, manganese, fluorine, mobile sulfur, zinc, nickel content depending on the depth of sampling and distance from phosphogypsum dumps to settlements and the Goryn River are presented. The directions of processing and utilization of the given waste are offered. The elemental composition of phosphogypsum dumps of PJSC "Rivneazot" has been established, in particular, the presence of a group of valuable rare earth elements.
... Cánovas et al. (2019) studied samples from Spain and scandium concentration was 1 mg/kg, where its extraction achieved 99% using 0.5 mol/L H 2 SO 4 and 3 mol/L HNO 3(Cánovas et al., 2019). Similar REE extraction was obtained byAbisheva et al. (2017) HNO 3 7.5 mol/L(Abisheva et al., 2017a). ...
Article
Scandium is a critical metal in increasing demand for modern technologies, such as light-weight aluminum-scandium alloys. Evaluating current and identifying new sources of the element has become a pressing need in order to provide a reliable and cost effective future supply. As current resources are limited, new sources must be explored with due consideration for the environmental aspects of the mining and processing technologies. The present review considers scandium extraction from three different sources - primary, secondary and opportunities – focusing on clean technologies and eco-friendly processing to achieve goals 7, 8, 9, and 12 of the 17 sustainable development goals of the United Nations. The main scientific databases were explored using keyword combinations. The question “is it possible to have an ecofriendly process for scandium extraction?” - worldwide debated – was answered providing diversified opportunities for scandium extraction, demonstrating that the current development would achieve these goals. Several techniques were explored and compared. As important as technical studies, economic approaches must be deeply evaluated where both acid consumption and downstream refining are equally challenging.
... One of the most common reutilization of industrial slag is its recycling as a sustainable source in construction (FernandezJimenez and Puertas, 1997;Turner and Collins, 2013) and ceramic industry (Nadirov et al., 2013;Teo et al., 2014;Guo et al., 2016;Abisheva et al., 2017;Potysz et al., 2018). Exploitation of slag has been extended to biomedical applications such as bone replacement, dental and orthopaedic applications (Stamboulis et al., 2005). ...
Article
Full-text available
One of the main objectives of a sustainable development and circular economy is the recycling of by-products generated in industrial and agricultural production processes. One of the possible solution is the use of such by-product materials in the synthesis of environmental adsorbents. In the current research, we present the synthesis of a high charge swelling mica with enhance adsorbent properties from blast furnace slag and rice husk ash. Moreover, to ensure the sustainable synthesis a natural bentoniteis used as Si and Al source. Thus, the current study investigated the fabrication of swelling high charged micas, Na-Mn (n (layer charge) = 2 or 4), from FEBEX bentonite, blast furnace slag and rice husk ash thorough the NaCl melt method. The reaction yield, cation framework distribution and structural characteristic of micas have been studied thorough X-ray Diffrac-tion and Solid State Nuclear Magnetic Resonance. The yields of Na-Mn synthesis and degree of purity of the mica depends on the nature of these precursors. Thus, a sustainable, non-expensive and environmental friendly process has been evaluated.
... 2500 mg/kg Ba, .1000 mg/kg Sr, Zr, Cr, and Ce) were reported (Cao and Wang, 2013;Abisheva et al., 2017) and hence its environmental risk in the abovementioned applications should be thoroughly investigated. ...
Chapter
Many types and large quantities of slags are generated from a wide variety of pyrometallurgical processes. Their safe and economic treatment is crucial for the sustainable development of society, with regard to environmental protection and resource preservation/recovery. This chapter provides an overview of 10 types of different slags: their sources, physicochemical characteristics, chemical and mineralogical properties, and their potential environmental concerns. The various routes for utilizing these slags in civil and environmental applications are reviewed with a particular focus on the leaching behavior of the potentially toxic elements. The efficacy of different treatments on the leaching performance of these slags and their use for stabilization/solidification of contaminated soils are discussed and research gaps are identified. Finally, future research directions are proposed, calling for more fundamental research and a holistic approach to utilize this material economically and safely.
... Its operation caused a violation of the architectural, planning and aesthetic principles of Chervonohrad and Novovolynsk due to the emergence of embankments of waste rock in their territory i.e. dumps [1,2]. Phytomeliorants have transformative functions: reclamation (forest crops, planting and sowing of plants on reclaimed lands), sanitizing (forests, sanitary protection strips), recreational (parks and forest parks), engineering and protective (field and erosion protection), architectural planning (urban landscaping system), ethical and aesthetic (spiritual education) [3][4][5]. An important place is given to vegetative reclamation of devastated landscapes -eroded lands, quarries, landfills, heaps. ...
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Urbanization in Ukraine has led to the development of the Lviv-Volyn coal basin. One of the main negative factors in the operation of coal basins are mine dumps. In addition to environmental hazards, waste heaps of coal mines violate the attractiveness and aesthetics of towns. The wastewater from waste heaps is a secondary factor in reducing the environmental safety of the coal-mining region. These waters are concentrated at the foot of landfills forming the man-made reservoirs. The research presents the negative factors of mine dumps and the results of physical and chemical analysis of subtericone wastewater and its impact on environmental pollution. It is established that the most polluted is the wastewater from waste heaps of the Mezhyrichanska mine which is caused by its operating process. The man-made polluted wastewater from heaps is a secondary factor in reducing the level of ecological danger of the coal-mining region. These waters are concentrated at the foot of landfills in the form of man-made reservoirs. The aim of the research is to indicate the negative factors of urban waste heaps by studying the physical and chemical properties of underspoil waters within the cities of Chervonograd and Novovolynsk.
... Конференция материалдары материалтану және минералды шикізаттарды өңдеу саласында жұмыс жасайтын ғалымдар мен мамандарға арналған. В настоящее время разработана технология переработки шлаков фосфорного производства с получением осажденного диоксида кремния и коллективного концентрата редкоземельных металлов [1]. Однако качество конечных продуктов по наличию в них примесей не отвечает уровню, который определяется требованием потребителя. ...
Article
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Phosphorus slag is the most heavy-tonnage waste of yellow phosphorus production, which is stored in the dump fields for many years causing ecological problems in the regions. One of the relevant and priority directions is rare-earth metals (REMs) production, presence of which in the phosphorus slags allows considering the latter as an acceptable raw material source. Phosphorus slags contain about 30–40 wt % of silicon dioxide, therefore they can serve as a source of production of precipitated silicon dioxide highly required in different industries. The purpose of this work is studying the conditions for REMs recovery from phosphorus slag and further processing of silicon-containing cake to improve a quality of the obtained products. The work shows results of researches on the phosphorus slags’ chemical and phase compositions identification, processes of leaching of phosphorus slag and the obtained silicon-containing cake by nitric acid. Instrumental and chemical methods of phosphorus slag content analysis dive following data. It consists of 90–92 % of pseudowollastonite α-CaSiO3, and also there is gyrolite Ca4(H2O)4[Si6O15](OH)2, small amounts of serpentine Mg6[Si4O10](OH)8, hydrated calcium aluminosilicate impurities CaO∙2Al2O3∙2SiO2∙H2O, quartz α-SiO2, calcite CaCO3, hematite Fe2O3, iron phosphate FePO4 and metallic iron with manganese impurity. As a result of kinetic studies of leaching process of phosphorus slag, the apparent activation energy for ΣREMs, calcium, aluminum and iron was determined which amounted to 4.31, 8.53, 7.43 and 12.31 kJ/mol, respectively. This, in combination with value of the Pilling-Bedward Criterion CP-B = 1.1 for orthosilicate acid H4SiO4, indicates that the process is characterized by an intradiffusion region. With a decrease in temperature of nitric acid treatment from 90 to 70 °C, purification degree of precipitated silicon dioxide from iron and aluminium impurities increases. Results of the experimental data will serve as a basis for development of the technology of complex processing of production waste of phosphorus industry and for improving quality of obtained products as REMs concentrate and precipitated silicon dioxide.
Article
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Yellow phosphorus is used widely in the world for production of phosphoric acid, various phosphates, flame retardant, detergent, water treatment, metal surface treatment, etc. After the production of yellow phosphorus, a large amount of phosphorus sludge is discharged to environment, causing environment pollution. This work focused on treatment of yellow phosphorus slag (YPS) and application of it as an absorbent for chromium (VI) ion and methylene blue. The YPS was first washed with water to remove phosphoferrite (FeP) and impurities and then being milled and transferred to a float sorting system to obtain YPS particles. The characteristics of YPS particles were determined by inductively coupled plasma-mass-spectrometry (ICP-MS), energy-dispersive X-ray spectroscopy (EDX), infrared spectroscopy (IR), scanning electron microscopy (SEM), X-ray diffraction (XRD), zeta potential, and nitrogen adsorption methods. The YPS particles were retreated with NaOH, HNO3, and EDTA solutions to evaluate the influence of these agents on metal ion and organic compound adsorption ability by YPS. The adsorption parameters of chromium (VI) ion and methylene blue (MB) by treated YPS particles were recognized by the ultraviolet-visible (UV-Vis) spectrometer. The effects of temperature, pH solution, and initial concentration of absorbed substances on the adsorption ability were investigated. The adsorption isotherms and adsorption kinetics of chromium (VI) ion and MB by YPS particles were also determined. The obtained results confirmed that the green technology used to treat the YPS2 particles is suitable to obtain an effective absorbent. The adsorption efficiency of YPS2 particles for removal of chromium (VI) ions is smaller than that for removal of MB in aqueous solutions. The adsorption isotherm of MB adsorption process is complied with the Langmuir isotherm while the adsorption kinetic fits well with the pseudo-second-order reaction model. The thermodynamic parameters of MB adsorption processed on YPS2 were calculated and discussed. 1. Introduction Yellow phosphorus slag (YPS) is a waste product of manufacturing yellow phosphorus (P4) using the electrical furnace method at 1400°C–1600°C [1]. The worldwide yellow phosphorus production yields an average of 1.5 million tons of P4 each year [2]. In which, the countries discharge a large YPS weight including Chinese (75%), Kazakhstan (13%), America (8%), Western Europe (6%), Russia (4%), and the rest of India. For each ton of manufactured P4, about 8 to 10 tons of yellow phosphorus slag are produced [1]. This waste product is often left accumulated in the landfills, proposing a potential pollution thread to the environment. The majority of YPS particles compose of CaO and SiO2, accounting for approximately 85% of the slag mass [3]. Other components of the YPS are Al2O3, Fe2O3, MgO, and some rare earth metals [4, 5]. In Vietnam, the P4 is mainly produced and supplied by Lao Cai Yellow Phosphorus JSC (Tang Loong Industrial Zone, Bao Thang District, Lao Cai Province, Vietnam), with the productivity of 93,800 tons P4/year and about 750,000–1,031,000 tons of YPS waste are produced and released directly into the surrounding environment [6]. Therefore, it is important to find different ways to utilize this waste product. Recent studies have been focusing on applying YPS into asphalt or asphalt binder [7, 8], cemented backfilling [9], retarding the early hydration of cement [10] or recovering rare earth metals [5]. YPS had been treated by different technologies and methods [11–13]. In German Auslegeschrift No. 1,804,172, the YPS particles were heat treated at 1000°C to 1100°C in a rotary furnace [11]. In German Offenlegungsschrift No. 2,211,505, a physical separation method, for example, by gravity separation with tetrabromoethane as the liquid phase, the refinement of silicate slag phase was reported [12]. US patent No. 4,243,425 presented a method for refining of silicatic slag phase with steam at a temperature between 600°C and softening temperature of the slag [13]. In this work, an effective method for treatment of YPS was developed. This is a combination of the water washing flotation system with milling and sorting flotation. The waste water system was treated to recover P2O5, F, and minerals for other applications. The advantages of this technology were low energy consumption, reduction of noise and dust pollution, closed technology, and environmental friendly and waste water can be easily processed and reused (about 80–90%). The minimized weight of chemicals was used, and treatment process was carried in room temperature. This approached to the green technology, the general trend of the world. The study on metal ion adsorption ability of YPS in aqueous solutions has been limited in the research. Herein, the YPS was chosen as an absorbent due to its silicate structure with high content of silica. Moreover, the small size particle as compared with micrometer inorganic additives is an advantage of the YPS. Hence, the obtained YPS could be expected to use as an absorbent for removing toxicity substances in aqueous solutions. In this paper, chromium (VI) and methylene blue have been chosen as the model substances to study the adsorption ability of YPS. Chromium, commonly found in various sources of industrial waste water, is one of the most toxic metal ions, which influences seriously the biodiversity of the environment and causes several health issues to humans. Chromium often comes from discharge of industrial activities such as leather tanning, electroplating, or textiles [14]. It exists in water with various oxidation forms, but mainly in trivalent and hexavalent state [15], in which the hexavalent state is considered the most toxic because it is easily dilution and can bioaccumulate in human organs [16]. Some studies reveal that Cr (VI) ions can cause digestive system and lungs cancer, gastrointestinal and dermatological problems, severe diarrhea, and hemorrhage [17–19]. Many materials have been utilized to adsorb Cr (VI) ions in aqueous solutions including banana peel [20], coffee resins [21], fly ash [22], groundnut hull [23], or zeolite NaX [24] and showed good results. Dye has been an important ingredient in many common daily industries such as textile, leather, cosmetics, plastics, and food production [25]. Nevertheless, colored dye waste water constitutes considerable issues to the environment and water sources [26]. Complex aromatic molecular structures of dyes make them nondegradable [27]. Dyes, which have high demand for chemical and biological oxygen, high toxicity, and capability to hinder sunlight penetration into water bodies, are harmful pollutants to the aquatic ecosystem [28]. Methylene blue (MB), a cationic dye, is widely used in biology, medical science, chemistry, and dye field. However, long-term exposure to MB can cause certain symptoms and illnesses such as increased heart rate, vomiting, nausea, anemia, cyanosis, and tissue necrosis [29, 30]. Various adsorbents have been used to adsorb MB in aqueous solutions with promising output such as activated carbon [29], natural clay [31], sea grass dead leaves [32], or modified pumice stone [33]. According to our calculation, the price of one tone of YPS at the Tang Loong Industrial Zone is only about 22 USD. This indicates that YPS product is cost-effective and promising for application not only as an absorbent but also as an additive for other fields (composites, paint, coating, etc.). Acids and bases are used for treatment of inorganic waste, for example, fly ash and gypsum, to improve the adsorption ability of these waste products [18, 20, 22, 23]. Besides, EDTA is known as a chemical used for both industrial and medical purposes. In the industry, it is mainly used to sequester metal ions in aqueous solution. Thanks to its high affinity for metal ions, EDTA can enormously enhance the chelation properties of the adsorbent. Therefore, in this work, NaOH, HNO3, and EDTA were chosen for retreatment of YPS particles to evaluate their adsorption ability. We mainly focused on the characterization of YPS products as well as investigation of the factors affecting on the adsorption ability of YPS products for removal of chromium (VI) ions and methylene blue in aqueous solutions. 2. Experiment 2.1. Materials Yellow phosphorus slag (YPS0) is waste product of Lao Cai Yellow Phosphorus JSC (Tang Loong Industrial Zone, Bao Thang District, Lao Cai Province, Vietnam) with a particle size of 50–100 µm; density of 2.75 g/cm³; hardness of 1–3; compressive strength of 80–100 MPa; water absorption of 1–4%; and porosity of 10–12%. Ethylenediaminetetraacetic acid (EDTA); 1,5-diphenylcarbazide (DCP); potassium chromate; and methylene blue (MB) were purchased from Merck Co. HNO3 and NaOH are the commercial products which are used as received. 2.2. Surface Treatment of Yellow Phosphorus Slag 2.2.1. Treatment of Yellow Phosphorus Slag by Flotation System Firstly, the washing flotation system was used to remove preliminary soluble impurities and to separate the particles for next stage. In this stage, the large content of FeP, P2O5, fluorine compounds, and some other impurities were removed and the YPS0 was then wet sieved down to prepare a granular material which is smaller than 100 µm in diameter (YPS1) (by sieve analysis). These particles could be applied for cement production or concrete directly. In the next stage, the particles were milled and transferred to a float sorting system to obtain particles in smaller size. The solid part was then rotated in a spinning double-drum composter and dried at 100°C until unchanged weight. The product was designed as YPS2 with the calcium silicate content in particles higher than 90%. The waste water system was treated to recover P2O5, fluorine compounds, and minerals for other applications. The BET surface area/t-plot micropore area, pore diameter, and pore volume of YPS2 product are 1.3145 m²g⁻¹/0.3024 m²g⁻¹, 21.4897 nm, and 0.000134 cm³g⁻¹, respectively (determined by the nitrogen adsorption method on a TriStar 3000 V6.07 A device). 2.2.2. Surface Treatment of Yellow Phosphorus Slag (YPS) Using NaOH and HNO3 Solutions The YPS particles were retreated by NaOH or HNO3 solution as follows: 200 mL of NaOH 1 M (or HNO3 1 M) solution was added into a flask containing 20 g of YPS particles and stirred at 70°C for 3 hours. Then, the treated YPS particles by NaOH (or HNO3) solution were filtered and washed with distilled water until filtered aqueous solution reached to neutral medium (pH 7). After that, the treated YPS particles were dried in an oven at 100°C for 12 hours. The YPS0 particles and YPS2 particles which were treated with NaOH or HNO3 solution were designed as YPS0-NaOH, YPS2-NaOH, YPS0-HNO3, and YPS2-HNO3. 2.2.3. Surface Treatment of Yellow Phosphorus Slag (YPS) Using EDTA In this research, YPS was modified by using EDTA as follows: 5 g of YPS was added into 100 mL distilled water in a 250 mL glass beaker containing 0.5 g of EDTA. This solution was then stirred on a magnetic machine at a speed of 500 rpm for 2 hours at 60°C. Next, the solution was filtered to obtain the solid part. Finally, the solid part was dried in an oven at 100°C for 3 hours. 2.3. Characterizations 2.3.1. Infrared Spectroscopy (IR) IR spectra of YPS samples were recorded using a Nicolet iS10 spectrometer (Thermo Scientific, USA) in the range of wavenumbers from 4000 cm⁻¹ to 400 cm⁻¹, resolution of 8 cm⁻¹, and scan average of 32 times. 2.3.2. Energy-Dispersive X-Ray Spectroscopy (EDX) EDX spectra of the YPS samples were carried out on a SEM/EDS device (Oxford Instruments, UK). 2.3.3. Inductively Coupled Plasma-Mass-Spectrometry (ICP-MS) The element content of YPS samples was detected by NexION 2000 ICP-DRC-QMS (Perkin Elmer, USA). 2.3.4. Scanning Electron Microscopy (SEM) Scanning electron microscopy (SEM) of YPS samples was taken on a SEM-S-4800 device (Hitachi, Japan). The samples were coated a Pt layer on the surface to enhance the resolution of images. 2.3.5. X-Ray Diffraction Analysis (XRD) XRD patterns of YPS samples were performed on a Siemens D5000 X-ray diffractometer (XRD) with CuKα radiation source (λ = 0.154 nm) at 40 kV generator voltage with 0.03° step and 30 mA current by 0.043°/s scan speed in the range of 2θ from 2° to 70°. 2.3.6. Zeta Potential Zeta potential of the YPS2 sample was conducted on a Zetasizer, ver. 6.2, Malvern Instruments, with zeta runs of 12, count rate (kcps) of 288.7, and measurement position of 4.5 mm at 25°C. The YPS2 was dispersed in water (pH ≈ 7) with its dispersant RI of 1.330, viscosity of 0.8872 cP, and dispersant dielectric constant of 78.5. 2.3.7. Ultraviolet-Visible (UV-Vis) Absorption Spectrometry Spectra of samples were determined on a UV spectrophotometer (CINTRA 40, GBC, USA) in the range of wavelength from 200 to 800 nm. 2.4. Determination of Adsorption Ability of Yellow Phosphorus Slag in Aqueous Solution An exact weight of the YPS samples was added into a 100 mL of Cr (VI) or MB solution. The solution was stirred on a magnetic stirrer at room temperature for 120 minutes. The solution was then filtered, and 25 mL of aliquots was withdrawn. For MB adsorption, the withdrawn solution was monitored by a UV-Vis spectrophotometer (CINTRA 40, GBC, USA) at λmax = 664 nm. For Cr (VI) adsorption, 1 mL of H2SO4 1M and 1 mL of DCP 0.5% solution were introduced into the withdrawn solution and this solution was kept for 10 minutes before taking on a UV-Vis spectrophotometer at λmax = 540 nm. All studies were performed in triplicate to increase accuracy. 2.5. Determination of Cr (VI) Ion and Methylene Blue Adsorption Isotherms and Adsorption Kinetics of Yellow Phosphorus Slag 2.5.1. Adsorption of Cr (VI) Ions and Methylene Blue Using YPS Samples The amount of adsorbate per amount of adsorbent at equilibrium condition, Q (mg/g), was calculated as follows:where and are the concentration of adsorbate in solution at initial and equilibrium (mg/L), V is the solution volume (L), and W is the mass of YPS samples (g). The percentage of metal ions removed, H (%), was calculated using the following equation: 2.5.2. Adsorption Isotherms In this work, we study the adsorption behavior in the solid-liquid system using four adsorption isotherms: Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherms. Langmuir isotherm equation for ion adsorption: where is the maximum monolayer adsorption capacity (mg/g) and kL is the Langmuir isotherm constant representing binding energy of the adsorption system (L/mg). Freundlich isotherm equation: where is the Freundlich isotherm constant (mg/g) indicating adsorption capacity and is adsorption intensity. Temkin isotherm equation: where is the Temkin isotherm equilibrium binding constant (L/g), is the Temkin isotherm constant related to heat sorption (J/mg), T is absolute temperature (K), and R is the gas constant (8.314 J/mol/K). Dubinin–Radushkevich (DR) isotherm equation: where is the theoretical isotherm saturation capacity (mg/g) and is the Dubinin–Radushkevich isotherm constant (mol²/kJ²). 2.5.3. Adsorption Kinetics Adsorption kinetics were studied using four reaction models: first-order, pseudo-first-order, second-order, and pseudo-second-order reaction models. First-order reaction model: Pseudo-first-order reaction model: Second-order reaction model: Pseudo-second-order reaction model: where is the maximum monolayer coverage capacity (mg/g); and are the amount of adsorbate adsorbed per gram of adsorbent at equilibrium time and testing time t (mg/g); and are the solution concentration at the initial time and the testing time t (mg/l); and are the rate constant (per minute) of the first-order reaction model, pseudo-first-order reaction model, second-order reaction model, and pseudo-second-order reaction model, respectively. 3. Results and Discussion 3.1. Characteristics of Yellow Phosphorus Slag (YPS) Samples 3.1.1. FTIR Spectra of YPS Samples Figure 1 shows FTIR spectra of the YPS samples. It can be seen that the absorption peaks of YPS samples mostly appeared in the wavenumber range of 1500–500 cm⁻¹. In the low frequency region, the deformation vibration of bridge Si–O–Si and terminal O–Si–O groups and the metal-oxygen polyhedral (CaOn) results in the absorption bands of about 550 cm⁻¹. The adsorption peak at 699 cm⁻¹ assigned to the Al–O and Si–O bonds and showed the presence of pseudowollastonite α–CaSiO3 in the slag. The spectra from 750 cm⁻¹ to 1050 cm⁻¹ with the peak at 872 and 920 cm⁻¹ correspond to the stretching vibration of Si–O groups, indicating the presence of the glass-like earth silicon. Numerous unbridged connections of Si–O emerging are the result of breach of the polymer network Si–O–Si of the frame due to the introduction of Са atoms for replacement of Si atoms in the Si–O–Si network. Furthermore, the peaks at 1414 and 1484 cm⁻¹ represent the vibration of in calcite, one of main compositions of YPS samples. This result is similar to the report of Zinesh et al. [34].
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This article presents the results of a study conducted to investigate the recovery of rare earth metals and precipitated silicon dioxide from phosphorus slag. To determine the possibility and completeness of the studied processes, thermodynamic data was obtained through the determination of the Gibbs energy and equilibrium constant of the reactions of calcium metasilicate with different reagents, namely sodium hydroxide and carbonate as well as nitric, hydrochloric, and sulphuric acids. This article also presents the results of studies on the treatment of phosphorus slags via hydrometallurgical methods using alkaline agents (sodium hydroxide and sodium carbonate) and nitric acid. The recovery of silicon in solution by the autoclave leaching of phosphorus slag using solutions of sodium hydroxide and sodium carbonate resulted in recovery efficiencies of 1.1% and 16.6%, respectively. The nitric acid treatment of phosphorus slag was studied, and the recovery efficiencies of various elements were the following: rare earth metals, 98.3–98.6%; aluminium, 96.5–98.6%; iron, 94.9–96.5%; and calcium, 99.1–99.5%. Nitric acid (46.5%) was selected as the phosphorus slag recovery agent. The cake produced after the nitric acid treatment of phosphorus slag was leached using two processes based on the use of a sodium hydroxide solution: (1) in a temperature-controlled cell under normal conditions and (2) in an autoclave. The process of leaching under normal conditions was determined to be the most effective process, resulting in an efficiency of silicon recovery into solution of 97.7%.
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The feasibility of manufacturing non-autoclaved aerated concrete using alkali activated phosphorus slag as a cementitious material was investigated in this paper. Liquid sodium silicate with various modules (the molar ratio between SiO2 and Na2O) was used as alkali activator and a part of phosphorus slag was replaced with fly ash which was used to control the setting time of aerated concrete. The influences of the fly ash, curing procedure, modulus of sodium silicate solution and concentration of alkalis on the compressive strength and bulk density of non-autoclaved aerated concrete have been studied. Moreover, the types of the hydration products were investigated using XRD and SEM. The results indicate that: the compressive strength of aerated concrete was influenced by concentration of alkalis obviously. The compressive strength of 11.9MPa and the bulk density of 806kg/m3 were obtained with an activator of 1.2 modulus of sodium silicate and 6% concentration of alkalis under the circumstance of 60°C curing for 28 days.
Article
When precipitated silica was prepared from yellow phosphorus slag by the phosphoric acid leaching, the Fe content can not meet the quality requirements of the product. This article indicates the method of purifying precipitated silica with nitric acid solution, which may decrease the Fe content to about 0.02%. The purification optimum technical conditions are: the nitric acid concentration 8%, reaction time 2.0 hours, reaction temperature 343.15K, fluid solid ratio 4:1, stirring speed 300 rpm.
Article
Phosphorous slag, one of the pozzolanic active materials, is a by-product from the production of yellow phosphorous. In this paper, phosphorous slag was ground and adopted to prepare concrete as a mineral admixture. Specific strength method was used to assess the influences of phosphorous slag content on the pozzolannic effects in concrete with different age. The results indicated that with the increase of phosphorous slag content and age, the pozzolanic effects were enhanced in concrete. Phosphorous slag powder is beneficial to the development of long-term strength of concrete.
Article
With an increase in number of waste nickel-metal hydride batteries, and because of the importance of rare earth elements, the recycling of rare earth elements is becoming increasingly important. In this paper, we investigate the effects of temperature, hydrochloric acid concentration, and leaching time to optimize leaching conditions and determine leach kinetics. The results indicate that an increase in temperature, hydrochloric acid concentration, and leaching time enhance the leaching rate of rare earth elements. A maximum rare earth elements recovery of 95.16% was achieved at optimal leaching conditions of 70 °C, solid/liquid ratio of 1:10, 20% hydrochloric acid concentration, −74 μm particle size, and 100 min leaching time. The experimental data were best fitted by a chemical reaction-controlled model. The activation energy was 43.98 kJ/mol and the reaction order for hydrochloric acid concentration was 0.64. The kinetic equation for the leaching process was found to be: 1−(1−x)1/3=A/ρr0[HCl]0.64exp−439,8008.314Tt. After leaching and filtration, by adding saturated oxalic solution to the filtrate, rare earth element oxalates were obtained. After removing impurities by adding ammonia, filtering, washing with dilute hydrochloric acid, and calcining at 810 °C, a final product of 99% pure rare earth oxides was obtained.
Article
Yttrium is important rare earths (REs) used in numerous fields, mainly in the phosphor powders for low-energy lighting. The uses of these elements, especially for high-tech products are increased in recent years and combined with the scarcity of the resources and the environmental impact of the technologies to extract them from ores make the recycling waste, that contain Y and other RE, a priority. The present review summarized the main hydrometallurgical technologies to extract Y from ores, contaminated solutions, WEEE and generic wastes. Before to discuss the works about the treatment of wastes, the processes to retrieval Y from ores are discussed, since the processes are similar and derived from those already developed for the extraction from primary sources. Particular attention was given to the recovery of Y from WEEE because the recycle of them is important not only for economical point of view, considering its value, but also for environmental impact that this could be generated if not properly disposal.
Article
Current resource issues and the growing demand for metals used in advanced technologies have focused attention towards more efficient processing of end-of-life products and waste streams. Fluorescent lamp waste is a viable target for the recovery of rare earth metals (REMs); specifically cerium, europium, gadolinium, lanthanum, terbium, and yttrium. Waste originating from a discarded lamp processing facility was investigated using Scanning Electron Microscopy/Energy Dispersive Spectroscopy and X-ray Diffraction. Total dissolution experiments were carried out with aqua regia at elevated temperatures in order to estimate an average metal content and assess the recycling potential of the material.
Article
The leaching of rare-earth elements, phosphorus, and alkali metals from phosphodihydrate, obtained in processing of the Khibiny apatite concentrate into mineral fertilizers, with sulfate solutions with a sulfuric acid concentration c(H2SO4) = 0.5−4 wt % was studied.
Article
The extraction of rare earth elements from apatite concentrate of Chadormalu plant of Iran was studied with the dissolution of ore in nitric acid. The parameters of acidity: 60%, solid to liquid ratio: 30%, leaching time: 30 minute, agitation rate: 200 rpm, temperature: 60 °C and particle size (d80): 50 microns were determined as the optimum operational conditions. The recoveries of lanthanum, cerium, neodymium and yttrium were achieved at 74, 59, 72 and 73%, respectively, in the optimized conditions. Multivariable regression was used to predict La, Ce, Nd, Y and total REEs (Y+Nd+Ce+La) leaching recoveries, using experimental data from laboratory studies. It was achieved quite satisfactory correlations of 0.93, 0.98, 0.99, 0.97 and 0.99 for the prediction of Y, Nd, Ce, La and total REEs recoveries, respectively. It was shown that the proposed equations accurately reproduce the effects of operational variables on the different REEs recoveries, and can be used to optimize the REEs leaching plant. Key wordsLeaching–Apatite–Rare Earth Elements–Regression
Article
Phosphorite ores are a potential resource of rare earths (RE) as well as phosphate so the recovery of rare earths during the wet processing of phosphoric acid is important. This study investigates the influence of operating conditions and crystal modifiers on the leaching of RE and the solvent extraction of RE with organo-phosphorus reagents. The results indicate that lower temperature, higher concentration of phosphoric acid and larger liquid/solid ratio are beneficial to RE enrichment in the phosphoric acid. Surfactant additives which enhance the crystal growth of gypsum also enhanced RE leach recovery about 75% under optimized conditions. Studies on the solvent extraction of RE found that D2EHPA mixtures with neutral organo-phosphorus reagents were antagonistic and that Fe3+ competed strongly over RE. Higher D2EHPA concentration, larger phase ratio, lower temperature and lower phosphoric acid concentration increased the RE extraction efficiency. A negative enthalpy change was found indicating an exothermic extraction reaction.
Article
At the present, most industrial slags are being used without taking full advantage of their properties or disposed rather than used. The industrial slags, which have cementitious or pozzolanic properties, should be used as partial or full replacement for Portland cement rather than as bulk aggregates or ballasts because of the high cost of Portland cement, which is attributable to the high energy consumption for the production of Portland cement. The traditional way to utilize metallurgical slags in cementing materials is to partially replace Portland cement, which usually results in a lower early strength and longer setting times. Presence of activator(s) can accelerate the break-up of structure and hydration of slags. Many research results have indicated that clinkerless alkali-activated slags even exhibit higher strengths, denser structure and better durability compared with Portland cement. In this paper, the recent achievements in the development of high performance cementing materials based on activated slags such as blast furnace slag, steel slag, copper slag and phosphorus slag are reviewed.
Article
The future availability of rare earth elements (REEs) is of concern due to monopolistic supply conditions, environmentally unsustainable mining practices, and rapid demand growth. We present an evaluation of potential future demand scenarios for REEs with a focus on the issue of comining. Many assumptions were made to simplify the analysis, but the scenarios identify some key variables that could affect future rare earth markets and market behavior. Increased use of wind energy and electric vehicles are key elements of a more sustainable future. However, since present technologies for electric vehicles and wind turbines rely heavily on dysprosium (Dy) and neodymium (Nd), in rare-earth magnets, future adoption of these technologies may result in large and disproportionate increases in the demand for these two elements. For this study, upper and lower bound usage projections for REE in these applications were developed to evaluate the state of future REE supply availability. In the absence of efficient reuse and recycling or the development of technologies which use lower amounts of Dy and Nd, following a path consistent with stabilization of atmospheric CO(2) at 450 ppm may lead to an increase of more than 700% and 2600% for Nd and Dy, respectively, over the next 25 years if the present REE needs in automotive and wind applications are representative of future needs.
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Comprehensive processing of phosphogypsum resulting in the production of chemically precipitated chalk, gypsum, and concentrate of rare-earth elements
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Fluctuation Spectrums and Silicate Structure. Nauka
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Recovering rare-earth elements from byproducts and man-made wastes of Khibiny apatite concentrate processing
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Method for Acid Decomposition of Calcium Silicate and Zirconium Recovery. Applicant and Patentee is GUP "All-Russia Scientific and Research Institute of Chemical Technology
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Comprehensive Nitric-Acid Processing of Phosphate Raw Materials
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