Article

Recovery of Vanadium and Gallium from Solid Waste By-products of Bayer Process

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Abstract

In this study, recovery of vanadium and gallium from solids waste by-products (vanadium sludge and electrofilter dust of calcination plant) of Bayer process was investigated. An efficient purification process wasdevelopedbased on the removal of impurities such as phosphate by water leaching, neutralisation using CO2-enriched air and addition of aluminate solution. Recovery of V2O5 from the purified solution via the precipitation of ammonium metavanadate, its conversion into polyvanadate by the addition of ammonium sulphate and sulphuric acid, respectively, and then the ignition of the latter at 560°C was demonstrated. Effects of various parameters on the purification and precipitation processes were shown. A treatment process involving sintering and two-stage of carbonisation was also demonstrated to produce a Ga-rich precipitate. A gallate solution suitable for electrolysis of Ga was also shown to be prepared from this precipitate. A complete flowsheet was proposed for the treatment of vanadium sludge and electrofilter dust.

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... Recovery techniques of base metals, including alumina, soda, ferric oxide and titanium oxide, from red mud are of much interest (Balomenos et al., 2011;Lindsay, 2011;Samouhos et al., 2013;Gladyshev et al., 2015;Liu and Li, 2015;Okudan et al., 2015;Qu et al., 2015). However, few systematic investigations have been conducted regarding the Ga extraction from the residue. ...
... The aforementioned Ga-bearing resources and the corresponding extraction processes, optimum recovery efficiencies, end products and applied scales are summarized in Table 3 (Figueiredo et al., 2002;Zhao et al., 2012;Gladyshev et al., 2015;Carvalho et al., 2000;Abisheva et al., 2012;Carvalho et al., 2000;Liu and Li, 2015;Abdulvaliyev et al., 2015;Klein et al., 1975;Zheng and Gesser, 1996;Gutiérrez et al., 1997;Oriol et al., 2007;Liu et al., 2016;Kinoshita et al., 2011;Gu et al., 2014;Swain et al., 2015a,b;Lee and Nam, 1998;Lu et al., 2015;Xu et al., 2004Xu et al., , 2007. ...
... Hydrometallurgy 174 (2017) 105-115 Table 3 Summary of gallium-bearing resources and extracting processes. Figueiredo et al., 2002;Zhao et al., 2012;Gladyshev et al., 2015;Carvalho et al., 2000;Abisheva et al., 2012;Carvalho et al., 2000;Liu and Li, 2015;Abdulvaliyev et al., 2015;Klein et al., 1975;Zheng et al.,1996;Gutiérrez et al., 1997;Oriol et al., 2007;Liu et al., 2016;Kinoshita et al., 2011;Gu et al., 2014;Swain et al., 2015a,b;Lee and Nam, 1998;Lu et al., 2015;Xu et al., 2007Xu et al., , 2004 concentration. Simultaneous recoveries of other valuable metals from coal ash fly and red mud should also be considered during the Ga recycling process, which would make the technology even more economically feasible. ...
Article
Gallium (Ga) is extensively employed in integrated circuits and advanced electronic devices as it provides the benefits of low energy consumption and high computation speeds. However, the Ga-bearing host minerals are scarce in nature. Ga occurs in combination with several minerals, mainly including aluminum, zinc, iron ores and coals, of which bauxite, zinc ores and coals are the primary original sources of Ga currently. Mining minerals for the sole extraction of Ga is not economical due to the low concentration of Ga. Accordingly, Ga is mainly recovered as a by-product from the processing of minerals. The current main commercial resources of Ga are Bayer liquor and zinc residue, which contribute to nearly all of the worldwide Ga production. The production of low-grade (99.99% pure) Ga has been increasing at an average rate of 7.4% p.a. for the past four decades and amounted to 375 tons in 2016. It is estimated to increase by 20-fold by the year 2030 compared to the yield of 275 tons in 2012. The mounting worldwide demand for Ga necessitates the search for additional resources and recovery technologies for this particular element. Apart from the Bayer liquor and the zinc residue, there are several other Ga-resources, which include red mud, coal fly ash, Ga-bearing electronics industrial waste, and flue dust from electric furnaces at phosphorus factories. Based on the chemical properties of Ga, it is evident that both strong acidic/basic conditions and high temperatures favor the efficient extraction of Ga from its corresponding minerals. Several hydrometallurgical processes based mainly on acid/alkaline leaching along with solution purification and recovery (e.g. ion exchange, solvent extraction and precipitation) have been proposed for Ga extraction from these resources. In this paper, the current status of Ga recovery was reviewed and specific examples were utilized for each resource to discuss the extraction methods, the recoveries and the optimum Ga-recovery conditions for each resource. Additional research appears to be necessary to establish a highly efficient and environmentally friendly process to recover Ga from these resources.
... There has been a surge in research interest around metal recovery from sources such as steel slag (Barik et al., 2014;Mirazimi et al., 2015;Gladyshev et al., 2015). By comparison, little attention has been paid to the non-technical issues relating to resource recovery from industrial residues (Gomes et al., 2016a). ...
... The content of metals such as vanadium in these residues (dependent on the source of iron ore, as well as potential addition of vanadium to influence the type of steel obtained) can be equivalent to the concentrations found in ore-grade deposits (up to 5% vanadium pentoxide (V 2 O 5 ) in steel slag whilst concentrations can be less than 2% in mined ores (Aarabi-Karasgani et al., 2010). Given growing demand for vanadium as outlined above, there has been an explosion of interest in the technical and environmental science literature exploring the potential for extraction (e.g., Barik et al., 2014;Mirazimi et al., 2015;Gladyshev et al., 2015). ...
Article
Full-text available
Highly alkaline industrial residues (e.g., steel slag, bauxite processing residue (red mud) and ash from coal combustion) have been identified as stocks of potentially valuable metals. Technological change has created demand for metals, such as vanadium and certain rare earth elements, in electronics associated with renewable energy generation and storage. Current raw material and circular economy policy initiatives in the EU and industrial ecology research all promote resource recovery from residues, with research so far primarily from an environmental science perspective. This paper begins to address the deficit of research into the governance of resource recovery from a novel situation where re-use involves extraction of a component from a bulk residue that itself represents a risk to the environment. Taking a political industrial ecology approach, we briefly present emerging techniques for recovery and consider their regulatory implications in the light of potential environmental impacts. The paper draws on EU and UK regulatory framework for these residues along with semi-structured interviews with industry and regulatory bodies. A complex picture emerges of entwined ownerships and responsibilities for residues, with past practice and policy having a lasting impact on current possibilities for resource recovery.
... Given the geochemical affinity between Al and Ga, the latter occurs mainly concentrated in: i) aluminium oxides being bauxites the main mineral in the nature and ii) hosted by aluminosilicates such as clays, apatites, nephelines and frequently alunite. Bauxite ores are the primary sources for Ga production, in fact approximately 90 % of world primary Ga is produced from leaching solutions of Bayer process (Gladyshev et al., 2015). Results of the mineralogical analysis of sludge samples collected along the ponds (see Table 2) identified different aluminosilicates as illite, kaolinite, microcline, montmorillonite and ankerite. ...
Article
Seawater represents a potential resource for raw materials extraction. Although NaCl is the most representative mineral extracted other valuable compounds such as Mg, Li, Sr, Rb and B and elements at trace level (Cs, Co, In, Sc, Ga and Ge) are also contained in this “liquid mine”. Most of them are considered as Critical Raw Materials by the European Union. Solar saltworks, providing concentration factors of up-to 20 to 40, offer a perfect platform for the development of minerals and metal recovery schemes taking benefit of the concentration and purification achieved along the evaporation saltwork ponds. However, the geochemistry of these elements in this environment has not been yet thoroughly evaluated. Their knowledge could enable the deployment of technologies capable to achieve the recovery of valuable minerals. The high ionic strengths expected (0.5–7 mol/kg) and the chemical complexity of the solutions imply that only numerical geochemical codes, as PHREEQC, and the use of Pitzer model to estimate the activity coefficients of the different species in solution can be adopted to provide valuable description of the systems. In the present work, for the first time, PHREEQC Pitzer code database was extended to include the target minor and trace elements using Trapani saltworks (Sicily, Italy) as a case study system. The model was able to predict: i) the purity in halite and the major impurities contained, mainly Ca, Mg and sulphate species; ii) the fate of minor components as B, Sr, Cs, Co, Ge and Ga along the evaporation ponds. The results obtained pose a fundamental step in critical raw materials mining from seawater brine, for process intensification and combination with desalination.
... Annually, approximately 120 million tonnes of red mud is generated with an estimated global inventory of over 3 billion tonnes . For possible metal recovery techniques from bauxite or red mud are leached where Al, V, and Ga also dissolve in acidic leach solution (Gladyshev et al., 2013a(Gladyshev et al., , 2015Liu and Li, 2015;Okudan et al., 2015). The rate of generation of red mud tends to increase, concomitant with the rapid depletion of high grade bauxites and increasing demand for aluminium (Abdulvaliyev et al., 2013). ...
... Increasing the sulfate concentration was shown to adversely affect the precipitation of ammonium metavanadate. Conversion of metavanadate into polyvanadate was achieved by repulping in hot distilled water (90-95°C) and in pH 2. Vanadium pentoxide (98.8% V 2 O 5 ) was produced by firing polyvanadate precipitate at 560°C (Gladyshev et al., 2015). ...
Article
Catalysts are used extensively in industry to purify and upgrade various feeds and to improve process efficiency. These catalysts lose their activity with time. Spent catalysts from a sulfuric acid plant (main elemental composition: 5.71% V2O5, 1.89% Al2O3, 1.17% Fe2O3 and 61.04% SiO2; and the rest constituting several other oxides in traces/minute quantities) were used as a secondary source for vanadium recovery. Experimental studies were conducted by using three different leaching systems (citric acid with hydrogen peroxide, oxalic acid with hydrogen peroxide and sulfuric acid with hydrogen peroxide). The effects of leaching time, temperature, concentration of reagents and solid/liquid (S/L) ratio were investigated. Under optimum conditions (1:25 S/L ratio, 0.1M citric acid, 0.1M hydrogen peroxide, 50°C and 120min), 95% V was recovered in the presence of hydrogen peroxide in citric acid leaching.
... After washing, residue was leached by 2.4 mol/L hydrochloric acid solution (200 mL) at temperature of 313 K for 0.5 h. The alkali-leaching temperature was within 363-513 K, which was also the common temperature range for aluminum production by Bayer process (Gladyshev et al., 2015;Hairi et al., 2015;Liu et al., 2015;Okudan et al., 2015). ...
Article
Kaolinite is a typical silicate impurity in microcrystalline graphite ore. Removal of kaolinite from graphite ores is important to achieve high purity graphite product. Alkali-acid leaching is effective to remove silicate impurity in microcrystalline graphite. For in-depth understanding of phase transformation of kaolinite in microcrystalline graphite purification process, dissolution behavior and mechanism in alkali-acid leaching process were studied in this paper. As shown in alkali-acid leaching tests and analyses (FTIR, XRD, and SEM-EDS), silicon extraction of kaolinite was mainly affected by sodium hydroxide concentration, alkali-leaching temperature, and alkali-leaching time. The dissolution mechanism of kaolinite was regarded as a three-stage process: kaolinite firstly dissolved in alkaline solution in form of soluble silicate and aluminate. Dissolved silicate and aluminate in alkaline solution then reacted with each other and aluminosilicate transient phase with Si/Al ≈ 1 precipitated when silicon ion concentration exceeded its equilibrium concentration. Finally, the aluminosilicate precipitate composed of nepheline and sodalite dissolved in hydrochloric acid solution. As a consequence, kaolinite dissolved completely in alkali-acid leaching process.
... Thulium is used to make high power magnets for laptops, lasers, while samarium is utilized for making high-temperature magnets. Lutetium finds its application in X-ray phosphor, dysprosium in highpower magnets, lasers and terbium in phosphors for light and displays (Abhilash et al., 2015;Gladyshev et al., 2013Gladyshev et al., , 2015Massari and Marcello, 2013;Okudan et al., 2015a,b). ...
Article
The paper provides an overview of the methods used for processing of red mud to extract rare earth elements (REEs). Red mud is a toxic and highly alkaline waste. Several methods have been adopted and being practiced all over the world for the processing of red mud. Complex processing of red mud is cost-effective since red mud contains iron, aluminum, titanium, calcium, rare earth metals etc. It has been observed that the acid leaching of red mud can almost completely recover the rare earth elements in the solution with various individual techniques and also a combination of them. Therefore, the choice of extraction method depends on the form in which the element occurs in the solution. However, relatively low concentrations of rare earth in the solution and significant amount of impurities increase the cost of getting the final commercial products. To ensure the cost-effectiveness of the process involving rare earth’s extraction from red mud, it is necessary to increase their content by several times. This article presents the various studies that have been carried out in these aspects and the possibility of making this resource a sustainable one for REE extraction with a special focus on scandium replenishment.
... Abdulvaliyev et al. [16] found that recovery from red mud by autoclave leaching was 98.5% Na 2 O, 65.3% Al 2 O 3 , 55.5% Ga, and 65.8% V 2 O 5 . Gladyshev et al. [17] investigated the recovery of vanadium and gallium from solids waste by-products of the Bayer process. They showed that vanadium pentaoxide was produced (98.8% V 2 O 5 ) by firing polyvanadate precipitate at 5608C. ...
Article
In this study, the statistical optimization of the leaching parameters of aluminum hydroxide extraction from bauxite waste (red mud) was investigated. The extraction parameters were solid-to-liquid ratio, base concentration, reaction temperature, leaching time, and stirring speed. Optimum experimental conditions were carried out by the Taguchi method. A higher dissolution rate was found to give better performance characteristics. The most important parameter was determined using the statistical analysis of variance. © 2017 American Institute of Chemical Engineers Environ Prog, 2017
... After washing, the residues were leached with 2.4 mol/L hydrochloric acid solution (200 mL) at 313 K for 0.5 h. The alkali leaching temperature was within a range of 393 K-513 K, which is the suitable temperature range for aluminum production by the Bayer process [17][18][19][20]. ...
Article
Sericite is a typical silicate impurity in microcrystalline graphite ores, and its removal is important in the preparation of high-purity graphite preparations. Alkali-acid leaching is an effective method used to purify graphite and remove silicate minerals. In this study, the dissolution behavior and mechanism of sericite in alkali-acid leaching were investigated. The dissolution of sericite was mainly affected by alkali leaching temperature, sodium hydroxide concentration, and alkali leaching time. According to the XRD, FTIR, and SEM-EDS analyses, the dissolution mechanism of sericite is a three-stage process: (1) sericite is dissolved in the form of soluble silicate and aluminate; (2) the dissolved silicate and aluminate then react with each other to form aluminosilicate; and (3) finally the aluminosilicate mainly composed of hydroxycancrinite and sodalite is almost completely dissolved in the hydrochloric acid solution.
... The cancrinite-dominated matrix of the same sample was, however, relatively depleted in trace elements (e.g., 140-170 mg/kg V) [77]. Sometimes, enhanced concentrations of V (112 mg/kg) and Ga (28 mg/kg) have been identified in the alumina dust from calciner electrostatic filters, making this material an attractive source of V and Ga [78]. The former examples therefore support the hypothesis that a proportion of trace elements is deposited to minor by-products of the Bayer process. ...
Article
Full-text available
The aim of this work was to achieve an understanding of the distribution of selected bauxite trace elements (gallium (Ga), vanadium (V), arsenic (As), chromium (Cr), rare earth elements (REEs), scandium (Sc)) in the Bayer process. The assessment was designed as a case study in an alumina plant in operation to provide an overview of the trace elements behaviour in an actual industrial setup. A combination of analytical techniques was used, mainly inductively coupled plasma mass spectrometry and optical emission spectroscopy as well as instrumental neutron activation analysis. It was found that Ga, V and As as well as, to a minor extent, Cr are principally accumulated in Bayer process liquors. In addition, Ga is also fractionated to alumina at the end of the Bayer processing cycle. The rest of these elements pass to bauxite residue. REEs and Sc have the tendency to remain practically unaffected in the solid phases of the Bayer process and, therefore, at least 98% of their mass is transferred to bauxite residue. The interest in such a study originates from the fact that many of these trace constituents of bauxite ore could potentially become valuable by-products of the Bayer process; therefore, the understanding of their behaviour needs to be expanded. In fact, Ga and V are already by-products of the Bayer process, but their distribution patterns have not been provided in the existing open literature.
... So far, most processes for treating spent vanadium oxide containing catalysts have been performed toward recovery of vanadium pentoxide by using a 3-step approach, involving acid leaching, oxidation and precipitation [2,[23][24][25]. Drawbacks of this pathway to the situation of spent sulfuric acid catalysts lay in the low content of vanadium to be recovered from the spent catalyst, operation requirement at elevated temperatures with large amount of high concentration acid solution as well as recovery efficiency versus vanadium oxide purity trade-off. ...
Article
In this work, the efficiency of the regeneration process of spent V2O5 catalyst from sulfuric acid plant under different atmospheres (5%O2/N2 or air) was evaluated. Temperature-programmed results showed that the observed reduction profiles of the samples are attributed to the reduction of amorphous V⁺⁵ and low-valence V+5−x species at low temperatures followed by the reduction of their crystalline structures at high temperatures. Significantly low values of SO2 conversion of the spent samples can be explained by the significant drop in quantity of all vanadium species, coupled with their structural change to more thermally stable forms. It was found that the exposure of the spent catalyst to 5%O2/N2 stream at 550 °C for 1 h allowed at first the re-oxidation of amorphous low-valence V species and second the dissolution of crystalline low-valence V species, thus resulted in recovery of their catalytic activity for SO2 oxidation. However, the regeneration in air was less effective than in 5%O2/N2 stream. This is supposedly due to the differential behaviors of the spent sample in different oxidative streams toward re-oxidizing low-valence V species and re-dissolving V precipitates.
... 1−5 The demand for Ga will be increased by 20× in 2030. 6 Therefore, the exploitation of potential resources for Ga production becomes very important to meet the increasing demand for Ga. It has been found that the contents of Ga and Al are high in coal, especially in Jungar coal (Inner Mongolia, China). ...
Article
The direct electrodeposition of Ga from carbonated spent liquor is proposed by membrane electrolysis with the simultaneous production of NaOH and NaHCO3. The effects of electrolysis time, current density and mechanical agitation on current efficiency (CE) are studied. Metallic Ga is successfully electrodeposited from synthetic liquor with very low Ga concentration by using Ga-coating cathode. The current efficiency for NaOH production decreases with the electrolysis time. After 13 h of electrolysis, the concentration of NaOH rose up to 109 g L-1. The current efficiency for NaHCO3 production is almost constant in the first 8 h and the value is about 74%. Then, the current efficiency decreases rapidly due to the accelerated formation of CO2. The largest concentration of NaHCO3 is about 108 g L-1. Ga electrodeposition is affected obviously by additive (FC-95), current density and mechanical agitation. 97.9% of Ga in carbonated spent liquor can be electrochemically extracted.
... Besides, it has been found that the addition of roasting additives can promote oxidation of vanadium while lowering the roasting temperature [27,28]. Moreover, the vanadium slag which is not incompletely roasted can also achieve a higher extraction efficiency under catalytic-oxidation leaching [15,29,30]. Therefore, the combination of low temperature roasting and high-efficiency selective leaching is an effective way to achieve energy saving and emission reduction of vanadium extraction [31]. ...
Article
Long-term high temperature in conventional vanadium extraction process would cause particles to be sintered and wrapped, thus reducing extraction efficiency of vanadium. Based on the purpose of directional conversion and process intensification, this work proposed a combination of low temperature sodium roasting and high efficiency selective oxidation leaching in vanadium extraction. The investigation of the reaction mechanism suggested that the structure of vanadium slag was changed by roasting, which also caused the fracture of spinel. The addition of MnO2 promoted the directional oxidation of low-valent vanadium into high valence. It also found that Na2S2O8 could oxidize low-valent vanadium effectively in leaching. The leaching efficiency of vanadium reached 87.74% under the optimum conditions, including a roasting temperature of 650 °C, a roasting time of 2.0 h, a molar ratio of sodium-to-vanadium of 0.6, a MnO2 (roasting additive) dosage of 5 wt.% and a Na2S2O8 (leaching oxidant) dosage of 5 wt.%. This percentage is 7.18% higher than that of direct roasting-and-leaching under the same conditions.
... This range was different from the precipitation using (NH4)2SO4 which was better at pH 7.2-7.6 (Gladyshev et al., 2015). ...
Article
Full-text available
Utilization of spent catalysts serves to meet the needs of vanadium and to overcome the environmental problem since vanadium is categorized as a hazardous, toxic material. Vanadium from the spent catalysts can be recovered in the form of V2O5 or NH4VO3. However, vanadate compounds (NH4VO3) are considered to be more valuable due to their higher price and easier production process, compared with V2O5. This study aims to find adequate operating conditions to obtain high yields and high purity of NH4VO3 crystals. The results showed that the presence of iron compounds in the extract made the crystals contaminated by brownish colour, so it decreased its purity. Therefore, iron compounds need to be separated first with precipitation. Crystals of NH4VO3 with yield of 60% on spent catalysts and purity of 75% were obtained by extraction using solvent Na2CO3 1.887 M for 60 minutes at room temperature with weight ratio of V2O5 in spent catalyst toward solvent volume (Rvp), 0.006 gram V2O5/mL Na2CO3. It was then continued by precipitation of iron compounds at pH of 12 for 2 hours and crystallization of NH4VO3 using NH4Cl 11.215 M for 4 - 5 hours at 60oC.
... The concentration of scandium in the BRM may be 0.012% (oxide), as X-ray fluorescence analysis showed. Gallium (Ga 2 O 3 -0.015% in BRM) is also considered a critical metal, and it can also be recovered from red mud [58][59][60][61]. Gallium is produced mainly as a by-product of the Bayer process, and it is estimated that more than one million tonnes of gallium is contained in bauxite reserves globally [62]. ...
Article
A new step in the Bayer process has been used to recover NaOH and to reduce its content in red mud. After digestion, the residue is separated fromthe Bayer liquor and goes through press filters, which enables the recovery ofNaOH and decreases the moisture content. It is well known that red mud is one of themost important sources of scandium. For this reason, the goal of this workwas to characterize a Brazilian red mud (BRM) for scandium recovery. The sample was collected after the press filter system process. Analysis of energy-dispersive X-ray fluorescence (EDXRF), scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS), and X-ray diffraction (XRD) was performed. Microwave digestion using an acid mixture was carried out to determine the concentration of the main elements. Fe2O3 represented 40% of the BRM, and the Sc concentration was 43 mg/kg. The SiO2 content was 24%, which is the highest value found in the literature, whereas the sodiumconcentration was the lowest. A literature review was carried out to compare results with BRM, as well as the current studies for recovery of scandium by the leaching/ion-exchange process. Scandium recovery using a leaching/ion exchange process may be possible with efficiency higher than 90%. The greatest challenge is the occurrence of silica gel formation during leaching.
... Vanadium is usually of +4 or +5 valence in solutions. The recovery of V(IV) and V(V) in acidic sulfate media and alkaline media have been studied separately [10][11][12][13][14][15][16][17]. The extraction of Fe(III) using di(2-ethylhexyl) phosphate (D2EHPA) in chloride solutions has also been widely studied [13,[18][19][20][21]. Studies on the solvent extraction of vanadium from chloride solution with trace impurities or the separation of vanadium and iron in acidic sulfate media have also been reported [22][23][24]. ...
Article
Purification of microcrystalline graphite concentrate with alkali-acid leaching process was studied in this paper. The influences of alkali leaching temperature, NaOH concentration, alkali leaching time, HCl consumption, liquid-solid ratio, and acid leaching times were investigated respectively. Final refined products with carbon content in the range of 90.88%–98.36% were prepared from flotation concentrate with carbon content of 84.27%. In addition, the volatile content in the end product was reduced from 2.7% to 1.17%. X-ray diffraction (XRD) and scanning electron microscope equipped with energy-dispersive X-ray spectroscopy (SEM-EDS) analysis revealed that the crystal structure and morphology of graphite had no obvious change when impurities composed of Si, Al, and O were almost completely removed. Alkali-acid leaching process could enhance the carbon content of microcrystalline graphite to a higher level than the traditional method of alkali roasting-acid leaching process.
Article
Global transition towards low-carbon future is threatened by supply risks surrounding critical raw materials, particularly the rare, scarce, and scattered metals (RSSM) with poor mineral endowments. Thus, the metal recycling from various end-of-life products are widely advocated and advanced as a key strategy, but the present understanding of their recycling potentials, limitations and challenges is quite scattered and limited. Here, this paper conducts a literature review, based on the PRISMA analysis of approximately 160 types of relevant studies from 2010 to 2021, to provide sophisticated knowledge related to the recycling status, progress, and future directions of 34 types of RSSM. Results indicate only a part of those metals can be recycled due to the obstacles in metal design as well as societal and economic factors in its usage and recycling, and the corresponding obstacles for each metal are further identified by key factors including complexity of the product design, more complex end-use of metal, and lack of suitable infrastructure for collection. Thus, the jointed efforts from all stakeholders along metal cycle from material design, use, throughout to final recycling are highly suggested and urged to secure metal base for future circular and low-carbon economy.
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Vanadium extraction from titano-magnetite by using hydrofluoric acid was put forward. The process of low intensity magnetic separation, hydrofluoric acid leaching, co-precipitation with NaOH, roasting with Na2CO3, circulating water leaching and precipitation of vanadium has been investigated. The results show that over 85% vanadium could be directly leached under the condition of sulfuric acid concentration of 5 mol/L, CaF2 dosage of 5%, leaching temperature of 95 °C, leaching time of 3 h and liquid to solid ratio of 3 mL/g. With the pH value of 4.5, temperature of 40 °C and time of 30 min, the co-precipitation rate of vanadium in the acid leaching solution was over 99%. The water leaching rate of vanadium of the co-precipitation reached 95% under the condition of roasting temperature of 800 °C, Na2CO3 dosage of 6%, roasting time of 1 h, leaching temperature of 90 °C, leaching time of 40 min, liquid to solid ratio of 2 mL/g and leaching stage of 4. Finally, the total recovery of vanadium could reach 81% and the purity of the product V2O5 was 99.65% meeting the standard specification with precipitation of vanadium and calcination.
Article
Efficient recovery of gallium from aqueous solution remains a problem to be solved in industry. Here a novel crosslinked monolith based on polyacrylonitrile/dimethyl sulfoxide (C‐PAN) was prepared by thermally induced phase separation and supercritical CO2 extraction drying technology. The influences of dissolution temperature and exchange solvents with different solubility parameters on the pore structure of C‐PAN were systematically studied. It was found that the pore diameter decreased with the decrease of dissolution temperature and the increase of Δδ between exchange solvent and PAN. Meanwhile, the C‐PAN with a small and dense pore structure showed better mechanical strength. Thereafter, the Ga3+ adsorption ability of amidoximated monolith (C‐PAO) in simulated Bayer liquor was determined by batch tests. In the case of using methanol as the exchange solvent, the kinetic and equilibrium inspection study illustrated that both physical and chemical adsorption are present due to the multiscale and interconnected structure and the amidoxime groups. The adsorption capacity of C‐PAO monolith toward gallium was 15.8 mg/g, with the equilibrium time as fast as 140 min, which can meet the requirement for the rapid extraction of gallium from Bayer liquor. It is expected that our work can provide some new ideas for fabricating gallium adsorbents. A crosslinked amidoximated polyacrylonitrile monolith with multi‐scale and interconnected macroporous structure was prepared via the thermally induced phase separation and supercritical CO2 drying method. The physical and chemical adsorption in the adsorption process enables it to fully chelate with the gallium ions in the Bayer liquor, thereby achieving efficient adsorption.
Article
The nucleation kinetics of ammonium metavanadate (NH4VO3) was investigated under conditions of the simulated process for precipitation of NH4VO3 from the vanadium-containing solution. Induction periods for the nucleation of NH4VO3 were experimentally determined as a function of supersaturation at temperatures from 30 to 45 °C. Using the classical nucleation theory, the interfacial tension between NH4VO3 and supersaturated solution, the nucleation rate and critical radius of nucleus for the homogeneous nucleation of NH4VO3 were estimated. With temperature increasing, the calculated interfacial tension gradually decreased from 29.78 mJ/m2 at 30 °C to 23.66 mJ/m2 at 45 °C. The nucleation rate was found to proportionally increase but the critical radius of nucleus exponentially decreased, with increase in supersaturation ratio at a constant temperature. The activation energy for NH4VO3 nucleation was obtained from the relationship between temperature and induction period, ranging from 79.17 kJ/mol at S=25 to 115.50 kJ/mol at S=15. FT-IR and Raman spectrum indicated that the crystals obtained in the precipitation process were NH4VO3.
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This study investigated the adsorption of gallium onto chemical and biogenic elemental tellurium nanoparticles. Biogenic elemental tellurium nanoparticles (BioTeNPs) were found to be a good adsorbent for the removal and recovery of gallium from aqueous solution with an adsorption capacity of 74 mg of Ga³⁺ per g BioTeNPs. The adsorption mechanism followed pseudo second order kinetics (R² = 0.999) and the experimental data fitted the monolayer adsorption theory-based Langmuir model. BioTeNPs had a size of 5.30-86.1 nm, a negative zeta potential (-32 mV) and were coated with a layer of extracellular polymeric substances (EPS). Further, a high desorption efficiency of 99% from Ga³⁺ adsorbed onto the BioTeNPs was achieved using oxalic acid (0.1 M) as eluent. This study proposes a novel removal and recovery method for Ga³⁺ by adsorption on BioTeNPs produced in bioreactors treating tellurium oxyanion rich wastewaters.
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Gallium is a silvery blue and soft metallic element that enjoys vast application in optoelectronics (e.g., LED’s), telecommunication, aerospace, and many commercial and household items such as alloys, computers and DVD’s. Albeit that gallium represents a small annual tonnage of material, its important impact as the backbone of the worldwide electronics sector goes unnoticed by the popularity of key base metals such as Cu/Ni/Co and attraction of the platinum group metals. Although gallite is a host mineral, gallium occurrence is associated with aluminosilicates such as bauxite and clays, plus zinc-bearing ores (e.g., sphalerite). Gallium is extracted primarily from the residue obtained during the processing of aluminum and secondly via electrolytic zinc. Other sources include fly ash collected from burning coal. Whilst countries such as Australia, China, Germany, Kazakhstan, Japan and Russia are the main suppliers of primary (i.e., virgin) gallium, France is the largest single source of refined gallium in the world. GEO Chemicals in France accounted for the lion’s share of the world’s annual production of refined gallium in recent years. At present, 60 companies located in 18 countries are actively engaged in the supply of gallium products. The majority of gallium is employed to produce gallium arsenide (GaAS) wafers for the electronics industry. The supply and demand of gallium-bearing products has gradually declined during the past decade. This was mainly attributed to bursting of the technology bubble worldwide while also being subject to swings in market price in relation to purity. The mandate of the paper was to simply pinpoint the salient facts regarding gallium globally and identify applicable sources of information thereby creating an ideal reference document.
Article
Sulphuric acid leaching of electrofilter fines Bayer Plant was investigated at different temperatures, using various particle size fractions and acid concentrations. Results showed that extraction was affected by acid concentration, initial particle size fraction and temperature of leaching. Aluminium dissolution in sulphuric acid increases as temperature does. At 90 °C, the increase in both acid concentration and reaction time has a positive effect on the extraction rate, which is also favoured by the decrease in particle size and solid:liquid ratio.The results of a leaching kinetic study are presented. Heterogeneity of the residue implies the existence of two different kinetics, the first one fundamentally due to the dissolution of the hydrate and the second one, being the case in study, due to the dissolution of transition alumina. The data obtained for the leaching kinetics in this second case, indicated that the dissolution of aluminium is a diffusion controlled reaction.
Article
The extraction of Ga(III) from HCl, HNO3 and H2SO4 media using 0.50 mol/L Cyanex 923 in toluene is investigated. Ga(III) is quantitatively extracted over a wide range of HCl at high concentration while the extraction is poor over the entire concentration range of HNO3 and H2SO4. The extracted Ga(III) is recovered by stripping with 0.10 mol/L HCl. The extracted species is identified as GaCl3.3Cyanex 923. The extraction behaviour of some commonly associated metal ions is also investigated. Based on the partition data, conditions have been identified for attaining some binary and ternary separations involving Ga(III) and V(IV), Al(III), Fe(III), In(III), Ti(IV), Ni(II), Mn(II), Cu(II), Zn(II), and Hg(II). The conditions are extended for the recovery of pure gallium from light emitting diode (LED) waste and bottom ash. The extractant is stable towards prolonged acid contact and there is a negligible loss in its extraction efficiency even after recycling ten times.
Article
A procedure is proposed to recover gallium from flue dust aluminum residues produced in plants by using solid-phase extraction with a commercial polyether-type polyurethane foam (PUF). Gallium can be separated from high concentrations of aluminum, iron, nickel, titanium, vanadium, copper, zinc, sulfate, fluoride, and chloride by extraction with PUF from 3 M sulfuric acid and 3 M sodium chloride concentration medium with at least a 92% efficiency. Gallium backextraction was fast and quantitative with ethanol solution. In all recovery steps commercial-grade reagents could be used, including tap water. The recovered gallium was precipitated with sodium hydroxide solution, purified by dissolution and precipitation, calcinated, and the final oxide was 98.6% pure.
Article
This paper reports on laboratory work for the development of a process flowsheet for the recovery of pure vanadium from sodium vanadate-containing sludge, typically analysing about 20 wt% V2O5. The sludge is generated as a by-product during the production of alumina from some bauxite ores by the Bayer process. The process developed consists essentially of (1) leaching of the sludge in hot water to solubilize the vanadium values, (2) adsorption of vanadium on activated charcoal, (3) desorption of vanadium with a suitable eluent, (4) precipitation of vanadium bearing cake from the strip solution, and (5) calcination of the cake to yield pure V2O5. The influence of various operational parameters on the process of adsorption, desorption and precipitation has been studied in detail. It has been possible to achieve high recovery of a 99.9% purity V2O5 product by allowing the adsorption to take place at a pH of around 2.5, desorption with 10% ammonia solution, and precipitation by acidification, all at temperatures around 85°C. Based on the experimental work, a schematic flow chart for the recovery of vanadium oxide from the vanadium bearing Bayer sludge has been presented.
Article
Vanadium is an important by-product that is used almost exclusively in ferrous and non-ferrous alloys due to its physical properties such as high tensile strength, hardness, and fatique resistance. Vanadium consumption in the iron and steel industry represents about 85% of the vanadium-bearing products produced worldwide. The ubiquitous vanadium is employed in a wide range of alloys in combination with iron, titanium, nickel, aluminum, chromium, and other metals for a diverse range of commercial applications extending from train rails, tool steels, catalysts, to aerospace. The global supply of vanadium originates from primary sources such as ore feedstock, concentrates, metallurgical slags, and petroleum residues. Vanadium-bearing host minerals consist of carnotite, mottramite, patronite, roscoelite, and vanadinite. Deposits of titaniferous magnetite, uraniferous sandstone, bauxite, phosphate rock, crude oils, oil shale and tar sands host vanadium. Apart from titanomagnetite and ilmenite ore deposits containing vanadium, slags from the ferrous industry are a major source of supply. At present, known world reserves are expected to supply the next century’s needs. Vanadium-bearing materials are treated by means of several processes such as calcium reduction, roast/leach, solvent extraction and ion exchange to recover vanadium either as metal, ferrovanadium, vanadium pentoxide, or in the form of various chemicals. The recovery of aluminum and magnesium metal from smelters and refineries generates vanadium and associated compounds. Countries such as China, South Africa, and Russia are the largest world producers of ferrovanadium and its toxic oxides while about 40 other countries contribute smaller quantities in different forms for global consumption. Australia is poised to become a major player for this essential substance during the next decade. The supply and demand of vanadium products during the past 20 years has been relatively stable and subject to a gradual decline in delivered price. The paper describes established industrial processes for recovery of vanadium from sources such as raw ore and process reverts. The comprehensive condensation of pertinent facts is intended to provide a single reference source rather than the reader perusing many articles.
Article
This paper reports the analytical results of lanthanides and other elements in pure elemental gallium. The analyses were performed by instrumental neutron activation analysis (INAA) at the nuclear reactor IEA-R1, IPEN, São Paulo. INAA has the advantage of being a multi-elemental and non-destructive analytical method. After irradiation, the samples were set aside for some days before running high resolution gamma spectrometry with a hyper-pure Ge detector. Gallium was recovered from the Bayer process alkaline leach solution, named by local aluminum industry as ‘weak soda’, (spent liquor) with a concentration of about 150 mg l−1. As a first step, gallium was recovered from the ‘weak soda’ and enriched using a complexing ion-exchanger of the polyamidoxime type specially synthesized in the country for this purpose. After washing the column with water and then with pure sodium hydroxide to remove the interstitial ‘spent liquor’, gallium was eluted from the resin. The eluted gallium solution was made to 4 mol l−1 in NaOH and subject to electrolysis. The metal was then collected from the electrodes and given a final purification step by dilute inorganic acid stripping. The most representative lanthanide elements found and analyzed in the metallic gallium were La, Ce, Nd and Sm. One of the most recent samples exhibited the following results: (μg g−1) La (16.1), Ce (15.5), Nd (11.8) and Sm (3.6). Besides the lanthanides, the following elements were also analyzed: U, Cr, Fe, Co, Zn, Mo, Se, Sb and Ba. The results showed that the metal obtained is highly pure. The purity can be enhanced by stripping the metallic gallium with a dilute mineral acid.
Article
Electrofilter powders, a by-product of the Bayer process for the production of alumina from bauxite, were leached with sulphuric acid to dissolve gibbsite and transition aluminas, thus obtaining a commercial aluminium sulphate solution and a solid residue. This residue is treated again under more drastic conditions with sulphuric acidic in a furnace at a higher temperature, is then leached with water and filtered, a small amount of solid remaining (alpha-alumina). The liquid is a highly acidic aluminium sulphate solution which does not fulfil commercial grade specifications; the liquor is accordingly treated with potassium hydroxide or ammonium hydroxide to obtain potassium or ammonium alum. Experimental tests were conducted to investigate the synthesis of alum by crystallization. The effects on alum formation of various operating conditions, including the amount of potassium or ammonium hydroxide, temperature and seed alum dosage, were examined. The crystallization process was found to be quite effective in obtaining alum.
Article
The Puertollano Integrated Coal Gasification Combined Cycle (IGCC) Power Plant (Spain) fly ash is characterized by a relatively high content of Ga and V, which occurs mainly as Ga2O3 and as Ga3+ and V3+ substituting for Al3+ in the Al-Si fly ash glass matrix. Investigations focused on evaluating the potential recovery of Ga and V from these fly ashes. Several NaOH based extraction tests were performed on the IGCC fly ash, at different temperatures, NaOH/fly ash (NaOH/FA) ratios, NaOH concentrations and extraction times. The optimal Ga extraction conditions was determined as 25 degrees C, NaOH 0.7-1 M, NaOH/FA ratio of 5 L/kg and 6 h, attaining Ga extraction yields of 60-86%, equivalent to 197-275 mg of Ga/kg of fly ash. Re-circulation of leachates increased initial Ga concentrations (25-38 mg/L) to 188-215 mg/L, while reducing both content of impurities and NaOH consumption. Carbonation of concentrated Ga leachate demonstrated that 99% of the bulk Ga content in the leachate precipitates at pH 7.4. At pH 10.5 significant proportions of impurities, mainly Al (91%), co-precipitate while >98% of the bulk Ga remains in solution. A second carbonation of the remaining solution (at pH 7.5) recovers the 98.8% of the bulk Ga. Re-dissolution (at pH 0) of the precipitate increases Ga purity from 7 to 30%, this being a suitable Ga end product for further purification by electrolysis. This method produces higher recovery efficiency than currently applied for Ga on an industrial scale. In contrast, low V extraction yields (<64%) were obtained even when using extreme alkaline extraction conditions, which given the current marked price of this element, limits considerably the feasibility of V recovery from IGCC fly ash.
Article
Supercritical carbon dioxide extraction, which is a feasible "green" alternative, was applied in this study as a sample pretreatment step for the removal of gallium (III) ions from acidic aqueous solution. The effect of various process parameters, including various chelating agents, extraction pressure and temperature, dimensionless CO(2) volume, the concentration of the chelating agent, and the pH of the solution, governing the efficiency and throughput of the procedure were systematically investigated. The performance of the various chelating agents from different studies indicated that the extraction efficiency of supercritical CO(2) was in the order: thiopyridine (PySH)>thenoyltrifluoroacetone (TTAH)>acetylacetone (AcAcH). The optimal extraction pressure and temperature for the supercritical CO(2) extraction of gallium (III) with chelating agent PySH were found to be 70 degrees C and 3000psi, respectively. The optimum concentration of the chelating agent was found to be 50ppm. A value of 7.5 was selected as the optimum dimensionless CO(2) volume. The optimum pH of the solution for supercritical CO(2) extraction should fall in the range of 2.0-3.0.
Recovery of gallium from industrial products of chemical and metallurgical industries
  • Z S Abisheva
  • A N Zagorodnyaya
  • Y G Bochevskaya
  • N S Bekturganov
  • A S Kasymov
  • I A Blaida
Abisheva, Z.S., Zagorodnyaya, A.N., Bochevskaya Y.G., Bekturganov, N.S., Kasymov, A.S., Blaida, I.A., 2012. Recovery of gallium from industrial products of chemical and metallurgical industries. In: XXVI International Mineral Processing Congress (IMPC) Proceedings, New Delphi, India, pp. 48-60.
Rohstoffe für zukunfstechnologien. Frovenhofer-Institut für System und Innovationsforschung ISI
  • G Angerer
  • L Erdmann
  • F Markscheider-Weidemann
  • M Scharp
  • A Lüllman
  • V Handke
  • M Marwede
Angerer, G., Erdmann, L., Markscheider-Weidemann, F., Scharp, M, Lüllman, A., Handke, V., Marwede, M., 2009. Rohstoffe für zukunfstechnologien. Frovenhofer-Institut für System und Innovationsforschung ISI, p. 383.