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Gallium and Vanadium Extraction from Red Mud of Turkish Alumina Refinery Plant: Hydrogarnet Process

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... Numerous studies have focused on the utilization of bauxite residue as a source for the production of major elements (e.g., blast furnace for pig iron production [10][11][12][13][14]) or as a source of rare earth elements (REEs) [15][16][17][18][19] as well as the combination of these [20]. Fewer efforts have been made to use the bauxite residue as a secondary source of other CRMs such as V and Ga [18,21,22]. ...
... Previous studies on extraction of Ga from bauxite residue have been based on mineral acids [18,22] and on alkaline solutions from bauxite residue (hydrogarnet process) [21]. In the latter, the extraction of Ga from bauxite residue was carried out in high modulus alkaline solution (240 g/L Na 2 O; α к = 30) at high temperatures (240-260 °C) in the presence of lime followed by treatment of the leachate by CO 2 -enriched air [21]. ...
... Previous studies on extraction of Ga from bauxite residue have been based on mineral acids [18,22] and on alkaline solutions from bauxite residue (hydrogarnet process) [21]. In the latter, the extraction of Ga from bauxite residue was carried out in high modulus alkaline solution (240 g/L Na 2 O; α к = 30) at high temperatures (240-260 °C) in the presence of lime followed by treatment of the leachate by CO 2 -enriched air [21]. ...
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Bauxite residue, the byproduct of alumina production, may potentially be a valuable source of strategically important metals, e.g. Gallium. Ga is considered critical element for the EU. To ensure adequate supply of Ga for the future, secondary sources such as bauxite residue should be exploited with efficient extraction methods. Therefore, in this study, mineral acids (H 2 SO 4 , HCl, and HNO 3) and an organic acid (H 2 C 2 O 4-oxalic acid), were evaluated for their efficiencies to extract Ga from bauxite residue. Using H 2 C 2 O 4 , the highest Ga leaching efficiencies were achieved, compared to other acids. The achieved leaching experimental results were considered for the construction of a design of experiment (DOE) model to achieve optimal conditions for Ga extraction using H 2 C 2 O 4. These values were validated by experiments which resulted in ~ 94% accuracy. In the second part of the study, using pure Ga solution, the adsorption of Ga onto zeolite HY was studied. The effects of adsorbent dosage, temperature, and contact time on the adsorption of Ga from solution by zeolite HY were studied. The obtained adsorption experimental results were used to construct a DOE model to achieve optimal conditions for Ga adsorption on to zeolite HY. The DOE-achieved optimal conditions were evaluated by experiments in pure Ga solution, which resulted in an efficiency of ~ 99.4 %. In the third stage, the bauxite residue was leached in H 2 C 2 O 4 under the optimal DOE conditions which resulted in 71% efficiency; thus the resulting bauxite residue solution was subjected to adsorption using zeolite HY under the optimal DOE conditions achieved. The Ga adsorption onto the zeolite was only 16% compared to the Ga adsorption of 99.4 % under the pure Ga solution, thus, representing the influences of the other leachates in the solution, which are minimizing the Ga adsorption onto the zeolite HY and providing an opportunity for future studies on the different mechanisms involved.
... The main components of red mud, for example, aluminum [8], sodium [8], iron [9], and titanium [10], were extracted or separated as resources. The leaching behavior of these elements from red mud was investigated [11]. Meanwhile, trace valuable elements in red mud including rare earth elements [12,13], scandium [14], gallium [11,15], vanadium [11,16], and lithium [17], were also reported as potential resources. ...
... The leaching behavior of these elements from red mud was investigated [11]. Meanwhile, trace valuable elements in red mud including rare earth elements [12,13], scandium [14], gallium [11,15], vanadium [11,16], and lithium [17], were also reported as potential resources. Concentrations of lithium in different red mud samples were determined as a trace/minor component with a wide range from several tens to hundreds μg/g [18][19][20] depending on the raw material, bauxite ore [21]. ...
... The leaching behavior of these elements from red mud was investigated [11]. Meanwhile, trace valuable elements in red mud including rare earth elements [12,13], scandium [14], gallium [11,15], vanadium [11,16], and lithium [17], were also reported as potential resources. Concentrations of lithium in different red mud samples were determined as a trace/minor component with a wide range from several tens to hundreds μg/g [18][19][20] depending on the raw material, bauxite ore [21]. ...
Article
Bauxite residue (red mud) is an alkaline waste derived from the industrial process for extraction of alumina from bauxite ore. Some bauxite residues contain considerable concentrations of critical metals, for example, rare earth elements. Lithium in red mud was also reported as a potential resource. In the current study, a Li-rich red mud was leached using acetic acid to investigate the leaching behavior of lithium followed by neutralizing with hydrochloric or oxalic acid. By neutralizing red mud using diluted hydrochloric acid (0.01 mol/L), 58.04–60.27% of lithium was leached using 25% acetic acid at 95 °C for 60 min. In the meantime, more than 95% of sodium and 85% of calcium were also dissolved in the leachate solution. While oxalic acid (0.5 mol/L) was used to neutralize red mud prior to acetic acid leaching, lithium performed lower leaching efficiencies (42.41–46.88%) in comparison of using of hydrochloric acid–neutralized red mud. Nevertheless, these leaching efficiencies of lithium were close to that of calcium and much higher than those of sodium under the condition. In this study, 25% (v/v) of acetic acid, at 85 °C for 60 min, was demonstrated as optimum conditions for lithium extraction from oxalic acid–neutralized red mud using acetic acid. The results would be useful and of interest for lithium recovery and purification from red mud.
... 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.
... [12][13][14][15] Depending on the origin of the residues, they may contain considerable amounts of CRMs, in particular REE and Sc. [16][17][18][19][20][21] Bauxite residues (also known as 'red mud', 'Bayer process tailings' or 'bauxite process tailings') are generated from alumina production where bauxite is digested in hot NaOH solution via the Bayer process. 22 The production of 1 tonne of alumina generates between 1 and 1.5 tonnes of bauxite residue. ...
... Various techniques have been used for the recovery of elemental metal or its suitable compound from the concentrate: metal compounds by crystallization or ionic precipitation, metals/metal compounds by reduction with gas, metals by electrochemical reduction and metals by electrolytic reduction. 112 Reference Wang et al. 55 Qu and Lian 21 Borra et al. 17 Ujaczki et al. 20 Mohapatra et al. 19 Petrakova et al. 82 Abdulvaliyev et al. 16 Alumina production in wileyonlinelibrary.com/jctb ...
Article
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Since the world economy has been confronted with an increasing supply risk of critical raw materials (CRMs), there is a major interest in identifying alternative secondary sources of CRMs. Bauxite residues from alumina production are available at a multi‐million ton scale worldwide. So far, attempts have been made to find alternative re‐use applications for bauxite residues, for instance in cement / pig iron production. However, bauxite residues can also be an untapped secondary source for CRMs. Depending on their geologic origin and processing, bauxite residues can contain considerable amounts of valuable elements. The obvious primary consideration for CRM recovery is the economic value of the materials contained. However, there are further benefits from re‐use of bauxite residues in general, and from CRM recovery in particular. These go beyond monetary values (e.g. reduced investment / operational costs by savings in disposal). For instance, benefits for the environment and health can be achieved by abatement of tailing storage as well as by reduction of emissions from conventional primary mining. Whereas certain tools (e.g. life‐cycle analysis) can be used to quantify the latter, other benefits (in particular sustained social and technological development) are harder to quantify. This review evaluates strategies of bauxite residue re‐use/re‐cycle and identifies associated benefits beyond elemental recovery. Further, methodologies to translate risks and benefits into quantifiable data are discussed. Ultimately, such quantitative data are a prerequisite for facilitating decision making regarding bauxite residue re‐use/re‐cycle and a stepping stone towards developing a zero waste technology.
... It is well known that the aluminium extraction of Bayer process is conducted by the digestion of bauxite with substantial hot sodium hydroxide solution. Given the generation of desilication products (DSP) mainly presented as sodalite or cancrinite with chemical formula of Na 6 [Al 6 Si 6 O 24 ]·Na 2 X·nH 2 O (X = CO 3 2− , SO 4 2− , 2Cl − , 2OH − or 2NO 3 − ), the losing of sodium hydroxide will accumulate in the red mud during the alumina extraction process (Abdulvaliyev et al., 2015;Zhang et al., 2011). Moreover, this behaviour will limit its application, especially using as iron-making materials, since the low melting point alkali metals circulating in the blast furnace and eroding the lining (Liu and Li, 2015). ...
Article
Red mud cannot be directly employed as the raw material of iron-making and construction materials for the existence of sodium element. The effects of cooling methods of furnace, air, water and liquid nitrogen on roasted red mud for recovering Na+ with water leaching were investigated through the analyses of TG-DTA, QXRD, FTIR, SEM, etc. The faster cooling methods we used, the better leaching performance would be obtained. Liquid nitrogen cooling sample therefore displayed the best leaching result with concentration of 1202 mg·L− 1 Na+ at the first leaching stage (~ 25 wt.% total sodium recovery). Part of cancrinite known as desilication products transformed into NaCaHSiO4 and nepheline after the roasting process. In the fast cooling red muds, the new generation of Na2Ca(CO3)2 could dissolve directly into water; the increase of Ca(OH)2 concentration to ~ 4.8 wt.% was beneficial for the dissolution of cancrinite and NaCaHSiO4 during the leaching process; amorphous phase increasing from ~ 4.1 to ~ 13.5 wt.% made sodium be more easily leached out from sodium-containing amorphous phase than the same crystalline phase; fluey flakes or plate-shape particles weakened the aggregation behaviour; the increase of specific surface area from 1.898 to 2.177 m2·cm− 3 leaded to the contact area increasing between particles and leachant, implying that sodium could be more easily leached out from the fast cooling samples.
... The metal concentration was analyzed by inductively coupled plasma-mass spectrometry (ICP-MS 7'500cx, Agilent Technologies, Basel, Switzerland). The following isotopes were analyzed: 27 Al, 45 Sc, 44 Ca, 47 Ti, 51 V, 53 Cr, 56 172 Yb and 175 Lu. The dwell time was set to 0.3 s per isotope and the argon plasma was operated at 1570 W with an argon flow of 15 L min −1 . ...
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BACKGROUND Red mud is a by-product of alumina extraction from bauxite by the Bayer process produced in the billion tons scale worldwide. Typically it is regarded as waste, but may potentially be a valuable resource of critical raw materials (CRM). In the present study both conventional extracting agents (mineral acids) and small molecular weight complexing agents (organic acids) were evaluated regarding their efficiency to extract CRM such as rare earth elements (REEs) from red mud. On a molar base, highest extraction efficiencies for REEs were achieved using HCl compared to the other acids investigated. Consequently, an experimental design approach was used to determine optimal conditions for CRM extraction using HCl. Instead of maximizing the extraction of a number of selected metals, the maximal economic potential as the sum of all metals (total metal extracted × economic value of the respective metal) was chosen as the application relevant response variable. Four explanatory variables (i.e. HCl concentration, contact time, temperature and slurry concentration) were used. RESULTS Optimal conditions maximizing the economic potential were predicted for 5.60 M HCl, 24 h contact time, 73.4 °C, and 100 g L-1 slurry concentration. Indeed, experimentally determined economic potential corresponded well (96 % of predicted) to the predictions, allowing a maximum recovery of 40.95 ± 0.90 US $ t-1. CONCLUSION Though the studied red muds were relatively low in CRM concentrations, the systematic approach developed here allows straightforward transfer to other red muds, harnessing the potential of the latter as important secondary source for CRM.
... Extraction of Al, Si, and Ti was around 30-50%. 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. ...
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
... It is worth mentioning that the Ga-bearing host minerals are quite scarce, consequently a large amount of research has been done on the potential Ga resources. Unfortunately, few efficient investigations have been conducted to extract Ga from the BRM, except a recent report from Abdulvaliyev et al. (2015). The researchers treated red mud by using Bayer-hydrogarnet process. ...
... As a kind of strategic resources, gallium and its compounds are widely used in semiconductors (Kim et al., 2015), photoelectric materials (Kente and Mhlanga, 2016;Liu and Wang, 2018), medicine Maurer et al., 2016), solar cells Xiang et al., 2017), liquid metal alloys (Khondoker and Sameoto, 2016) and catalysts (Iqbal et al., 2016). However, there are no pure gallium ores in nature, and gallium usually exists in sphalerite (Liu et al., 2017b;Liu et al., 2016), bauxite (Abdulvaliyev et al., 2015;Zhao et al., 2016) and coal fly ash (Funari et al., 2017;Qin et al., 2015). Therefore, gallium is generally recovered as a byproduct during the metallurgical process. ...
Article
In the present work, an α-aminophosphonate extractant di(2-ethylhexyl) [N-(2-ethylhexyl)aminomethyl] phosphonate (Cextrant 230, L) was applied for the selective extraction and recovery of Ga(III) from the chloride solutions. The extraction of Ga(III) was compared with that of other metal ions such as Fe³⁺, Fe²⁺, Zn²⁺, Al³⁺, Mg²⁺ and Sn²⁺. The extracted complex of Ga(III) was deduced to be HGaCl4·L. The extraction equilibrium constant and thermodynamic parameters (ΔG, ΔH and ΔS) were calculated. The positive value of ΔH indicates that the extraction reaction of Ga(III) is an endothermic process. The loading capacity of 30% (v/v) Cextrant 230 for Ga(III) was determined to be 0.38 mol/L. The loaded gallium can be complete stripped by distilled water. A process was established for the selective recovery of Ga(III), by which the purity of the gallium product reached 94% with a yield of 89.5%
... As the red mud has high alkalinity, large specific surface area and good absorbability, it can be applied to the solidification of heavy metal contaminated soil (Wansom et al., 2006;Song, Suo, Dong, & Chen, 2018). Moreover, the reactivity of red mud has a great influence on the curing effect (Abdulvaliyev, Akcil, & Gladyshev, 2015). As the red mud produced by the Bayer process after many washing cycles, settling and filtering, most of minerals in its particles have lost their reactivity. ...
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As a static method for testing pollution and strength of soil, the resistivity method has been used by many scholars, whereas few studies have been carried out on dynamic deformation monitoring by this method. To study the pressure sensitive properties of copper contaminated soils solidified by modified red mud, a series of unconfined compression tests were conducted. The compressive stress, strain and electrical resistivity in whole process were determined. Relationship between the resistivity and the parameters including stress, strain, red mud content, copper content, and curing age were analysed. Then the mechanism of electrical resistivity is revealed. Results indicate the stress-resistivity change rate follows the same trend as the stress-strain curve. The resistivity change rate follows the same rule as the strain change, indicating that the electrical resistivity can reflect the strain indirectly. The higher red mud content is, the better pressure sensitive properties of solidified soil is. A proper amount of copper can improve the pressure sensitivity of solidified soil, while excessive copper ions can reduce pressure sensitivity of solidified soil. These changes can be attributed to the pore water, iron oxide in red mud, tunnel conductive effect and conductivity percolation.
... Red mud (RM) is a highly alkaline solid waste generated in the process of alumina extraction from bauxite ores [1]. The total quantity of RM stored in the world has currently reached 4 billion tons, and it is predicted to increase to 150 million tons per annum. ...
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In the present study, using Aspergillus niger and Penicillium tricolor, the influence of the selected parameters, including sucrose concentration, inoculation size of spores, pulp density, and pre-culture time, on the bioleaching efficiency (biomass, organic acids production, and vanadium extraction, respectively) of red mud were studied. The bioleaching kinetics under optimal conditions were also explored. Sucrose concentration showed a positive linear effect on bioleaching efficiency below 143.44 and 141.82 g/L using A. niger and P. tricolor, respectively. However, a higher concentration was unfavorable for vanadium extraction. The inoculation size of spores showed an insignificant effect on both biomass and vanadium extraction if it exceeded the lowest coded levels (0.5 × 107/mL). Red mud pulp density showed a negative effect on the bioleaching efficiency of A. niger but a positive effect on organic acids production and vanadium extraction of P. tricolor. A pre-culture was indispensable for A. niger but not for P. tricolor due to the fact of its isolation from the red mud examined in this study. The kinetics analysis showed that the leaching rate of vanadium followed a two-domain behavior: initially, a rapid leaching period of approximately 10–15 days and, subsequently, a slow leaching period. Considering the change of the particles’ appearance as well as in the elemental composition of the bioleached red mud, it is speculated that the rate of leaching agents through the silicon minerals was the rate-limiting step of dissolution kinetics under the fungal bioleaching process.
... The understanding and control of the transformation of silicon minerals in the extractive metallurgy processes are significant issues (Queneau and Berthold, 1986). As an example, in the Bayer process for Al 2 O 3 production, silicon reacts with alumina and soda to precipitate as insoluble sodium alumina silicate (e.g., sodalite), which is then discharged as red mud causing serious caustic and alumina losses (Abdulvaliyev et al., 2015;Liu and Li, 2015;Smith, 2009). Silicon also causes severe scale formation, which leads to less effective heat transfer (Zheng et al., 1997). ...
... Subsequent purging with CO 2 resulted in complete gallium precipitation. Another study by Abdulvaliyev et al. [20] focused on the treatment of coal fly ash red mud originating from an alumina refinery plant. Prior to CO 2 carbonization, silica was removed by the addition of lime milk (hydrogarnet process). ...
Article
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In this article, we examine the selective hydrometallurgical extraction of gallium from pyrolyzed smartphones. Gallium-enriched pyrolysis residue originating from pyrolyzed smartphones was leached using NaOH and gaseous oxygen at elevated temperatures and pressures. The high content of organic carbon in the material strongly influenced the leaching performance. Oxygen, which is indispensable for the dissolution of gallium, also oxidized the organic carbon in the feed so that CO2 was released, which had a neutralizing effect on the alkaline solution. As a result, the CO2 formation complicated the accurate process control as the leaching temperature increased. The highest gallium yield of 82% was obtained at 180 °C, 5 g/L NaOH and 5 bar oxygen pressure. Decreased temperatures, NaOH concentrations and oxygen pressures resulted in lower leaching yields but with a higher selectivity for Ga. Temperatures higher than 180 °C resulted in extensive carbon oxidation, NaOH consumption and the coextraction of Cu and Ag. We propose that those conditions also facilitated the formation of water-soluble organic compounds, which would also influence the metal dissolution.
... Figure 1(a) and (b), depicts the rate of red mud production as well as cumulative inventory trend for the years 1950years -2000years and 2001years -2018 represents the global red mud management trend Table 2. Summary of global alumina production during 2008-2017 (thousand metric tons), adapted from U.S. Geological Survey (2015,2016,2017,2019) and Bray (2016Bray ( , 2018. Country 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 Australia 19,321 19,948 19,956 19,399 21,357 21,528 20,474 20,097 20,681 20,486 Azerbaijan 165 80 -6 102 -----Bosnia and Herzegovina 294 192 269 262 202 176 171 251 188 180 Brazil 7,822 8,618 9,433 10,306 10,321 9,942 10,404 10,452 10,886 10,900 Canada 1,370 1,125 1,301 1,471 1,498 1,555 1,563 1,561 1,567 1,570 China 22,800 23,800 29,000 34,100 37,700 47,000 51,300 58,978 60,907 69,017 France 630 348 481 524 430 315 300 300 300 300 Germany 1,395 1,154 1,485 2,355 2,331 2,244 1,910 1,910 1,900 1,900 Greece 772 719 725 810 784 812 814 807 821 810 Guinea 593 530 597 574 150 ---- 3. Advantages and weaknesses of the existing red mud disposal/management process (Evans, 2016;Greg Power & Klauber, 2009;Power et al., 2009Power et al., , 2011 (Abdulvaliyev et al., 2015;Evans, 2016;Khairul et al., 2019;Lu et al., 2018;Power et al., 2011;Ujaczki et al., 2019). ...
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Significantly unexploited red mud contains 0.5–1.7 kg/ton of rare earth metals (REMs) and 14–45% Fe, 5–14% Al, 1–9% Si, 1–6% Na, and 2–12% Ti which is currently being stockpiled. Reasonably, the red mud can be a suitable secondary resource of REMs, and other valuable metals, if not for the contained base metals. Stockpiled red mud locks down these technologically important and supply chain critical metals. Though quantitatively minor, the value perspective of REMs in red mud is significant. Global red mud inventory could reach 4 billion tons by 2020 and being generated 120–150 million tons per year worldwide. Analysis indicated that industrial-scale valorization could unlock approximately $4.3 trillion worth of REMs from stockpiled red mud. The current review discusses the valorization of red mud through metal value recovery which is an industrial waste circular economy challenge. Unlike other reported reviews, the current review intensively discusses circular economy challenges and opportunities associated with the red mud valorization. Finally, a suitable conceptual sequential metal recovery process has been proposed based on a comprehensive review of various processes which can technically be a feasible process for sequential recovery of various metal values from the red mud. Comprehensive cutting-edge research, broader risk assessment, and cost and benefit analysis of the proposed process can ensure broader valorization. Broader valorization can address several issues through the proposed process like; (i) metal value recovery, (ii) REMs circular economy, (iii) closed-loop process with the industry, and (iv) lower the futuristic carbon economy, simultaneously.
... Several authors have discussed BR as secondary resources for REM and reported exploitation strategies through research and development. Most of the research reported in the literature is focused on either valorization or selective metal recovery from BR (Abdulvaliyev et al., 2015, Borra et al., 2016. When selective metal recovery is the interest, the motivation is focused on base metal or selective to Sc or La like metals only. ...
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Bauxite residue (BR), simultaneously an environmental challenge as well as known to be a secondary resource for resources various valuable metals like Ti, V, Ga, and rare earth metal (REM). Lack of understanding and technology detects BR to be stockpiled which is counterproductive considering the environment, land scarcity, and management of BR inventories. As BR remains unexploited, significant amounts of REMs in BR remain unlocked, which are critical metals from green energy, environmental sustainability, and supply chain bottleneck perspective. Our current investigation analyses the potential of BR as secondary resources and quantity and worth of REM being remains unlocked. The quantitative content of global bauxite, alumina, and BR production during the last 5 decades have been analyzed. Also, plausible BR generation in the next 3 decades has been estimated. Considering the content of REM in BR amount of REM either stockpiled or to be stockpiled along with BR has been analyzed. Our study indicated about 9.14 million tons of REM remain locked in the stockpiled BR, 31.24 million tons of REM remain locked in the bauxite reserve. The worth of worldwide REM oxide remains unexploited in bauxite reserves and locked in stockpiled BR could be approximately $5000 billion, potentially can meet current and project demand of REM abundantly.
Article
Red mud is generated at a rate of up to 175.5 million tons per year. The global stockpile of red mud is near 4 billion tons. This material is hazardous with pH values from 11 to 13. Reduction of this waste is critical. Current industry practices for disposal of red mud involve different stockpiling techniques on valuable land area or disposing into critical bodies of water. This review studies processes which can reduce the negative environmental impact of red mud in an economic way. For instance, neutralization of red mud with CO2 can decrease the pH from 12.5 to 7. Treatment of red mud by this method lessens the negative environmental impact and prepares it for further processing for utilization. The current utilization rate of red mud is very low, only about 3 million tons per year are used as an additive for cement and construction. Red mud contains a large quantity of valuable minerals that can be extracted to both reduce the amount of red mud and provide value to the waste. This review investigates novel methods for treating red mud and extracting minerals like iron, titanium, and rare earth elements using a variety of smelting, direct reduction, and leaching processes. For example, the iron nugget process is a single step method to reduce iron oxides to metallic iron and separate them from red mud. Iron nuggets produced from red mud have an iron grade above 90%, which is comparable to pig iron generated by the blast furnace.
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Hydrogarnets are vital intermediate products in the calcification- carbonation method, which is designed for Bayer red mud treatment. Their carbonation performance greatly depends on SiO2 substitution. In this study, different SiO2-substituted hydrogarnets were synthesized and characterized. Then, batch experiments were performed to evaluate the potential effects of important parameters such as CO2 pressure, and SiO2 substitution degree (x) on the carbonation process. The SiO2 substitution degrees of the hydrogarnets synthesized at 60, 120, 180, and 240°C were 0.27, 0.36, 0.70, and 0.73, respectively. As the SiO2 substitution degree increased, the hydrogarnet carbonation extents gradually declined. With an increase in CO2 pressure, the hydrogarnet carbonation percentages increased gradually and rose from 80.33% to 98.19% within 120 min. The phases detected in the carbonized products were strip-like aragonite as well as some calcite; the Al-rich and Si-rich phases in the carbonized products were amorphous.
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Gallium (indium)-containing dust as a hazardous waste generated from light-emitting diode (LED) epitaxial wafer manufacturing attracts worldwide attention because of both resources and environmental importance. Oxidative roasting combined with acidic leaching is frequently utilized to recover the corresponding metals from such dust while the recovery rate is usually low due to the rather inert physicochemical properties of gallium compounds. Simultaneously, the selectivity of leaching is low, which results in complex separation or purification is required in order to obtain the required product, e.g. metallic gallium, Ga(OH)3. In this research, it is demonstrated that the selectivity of leaching can be achieved via properly controlling the physicochemical properties of the leaching solution and the leaching conditions. The leaching rate of gallium can reach 90.01 % through optimizing the effects of different parameters, including leaching reagent concentration, solid-to-liquid ratio, reaction temperature, reaction time and rotation rate, which is about 16 % higher than the conventional method. Moreover, the corresponding leaching mechanisms and kinetics were also evaluated and the apparent activation energy of the reaction is determined as 24.33 kJ/mol. Without further purification, 99.8 % of gallium and 99.1 % of indium can be further recovered as Ga(OH)3 and In(OH)3 from the leaching solutions, respectively. In the whole process, the effective recycling rates of gallium and indium are 89.83% and 92.42 %, respectively. This study provides bases for developing an effective recycling process of such waste with high recovery rate, advanced selectivity and low environmental impacts.
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The extraction of Al from Inner Mongolia (China) fly ash by HCl leaching produced a kind of solid waste called red mud (CRM). This red mud contained a great deal of gallium (Ga 2 O 3 , 0.305 wt%) and thus it was a very valuable Ga resource. In this work, an easy hydrothermal alkaline leaching method was developed to extract Ga from CRM. This method mainly solved the separation of Ga and Fe, because they existed in CRM in the form of Ga(OH) 3 and Fe(OH) 3 , and the Fe(OH) 3 in CRM had a strong coating effect on Ga(OH) 3 . In this method, Fe(OH) 3 was converted to Fe 2 O 3 in hydrothermal environment with small specific surface area, which weakened the coating for Ga(OH) 3 and accelerated the leaching reaction between Ga(OH) 3 and NaOH. The influencing factors on the leaching rate of Ga were discussed and the optimal Ga leaching conditions were determined as NaOH concentration of 20 wt%, leaching temperature of 120 °C, leaching time of 12 h, filling degree of 50%, reactor rotating state, and liquid-to-solid ratio of 5 mL/g. The leaching rate of 91.4% was obtained for Ga from CRM at the optimal conditions and the Ga 2 O 3 concentration in leaching solution reached 73.44 mg/L. Fe was not detected in leaching solution using hydrothermal alkaline leaching method and the main component of the leaching residue was α-Fe 2 O 3 with small (average size 3.62 μm) and uniform particle size.
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The article provides the fundamental possibility of the associated extraction of Rare Earth Metals during carbonate conversion of phosphogypsum and red muds. There are the isotherms of solubility of carbonates, phosphates and hydroxides of europium, neodymium, holmium, cerium, and ytterbium obtained in carbonate solutions. By changing the carbonation conditions, Rare Earth Elements are transferred to a carbonate solution in the form of water-soluble complexes. Then they can be recovered by precipitation. Also, there were found the optimum conditions with the maximum degree of recovery into the solution.
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Leaching scandium from red mud using succinic acid as a leaching agent was investigated. The experimentswere carried out by mixing red mud with a solution of succinic acid. To improve scandium extraction rate, various methods of red mud processing were performed: preliminarygrinding, microwave heating, temperaturetreatment. The highest degree of extraction of Sc was 45 %.
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Red mud is an industrial slurry waste that is produced as a byproduct of the Bayer process for alumina. The waste is generated in large quantities, up to a ratio of 2:1 against the valued product alumina. Red mud exhibits many chemical and physical properties that categorize it as a hazardous material. Due to the addition of sodium hydroxide in processing, the pH is typically at values close to 13. Small particle size discourages separation from water for disposal, so drying red mud happens over many years. The pH of red mud can be reduced with inexpensive reagents. Carbon dioxide is a greenhouse gas that is finding a great deal of research into potential sinks to reduce the footprint on the atmosphere. Combining carbon dioxide with red mud can effectively reduce the pH while also providing a sink for the greenhouse gas. Carbon dioxide is able to reduce the pH of red mud from 13 to 10 over long periods of time. Red mud can be utilized to produce a variety of value-added products. Most red muds around the world contain a large quantity of iron, titanium, aluminum, and rare earth elements. One method of removing the iron is through the iron nugget process which reduces iron and removes impurities in a single step. The iron nugget process is able to produce blast furnace quality pig iron (over 90% iron purity) with the addition of a carbonate flux material. Rare earth elements are concentrated in the slags from the iron nugget process and can be removed with acid leaches. The current view of red mud as a waste material is misleading. The proposed work will investigate methods to reduce the hazardous nature of red mud by reducing the pH and also remove valuable minerals. This will effectively give value to the waste product while simultaneously reducing the overall amount of red mud waste that needs to be disposed.
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This study investigates the composition and reactivity of two GBFS-like slags produced from bauxite residue (BR). The composition of the slags was analysed using a multi method approach. The hydraulic reactivity was assessed in Portland composite cement and with the addition of anhydrite, limestone and combinations thereof. The presented approach is further discussed in the context of the full valorisation of BR and the economic as well as environmental implications. Both slags demonstrated a good strength contribution at a 25% substitution rate. Both failed the minimum strength requirements for GBFS according to EN 15167–1, using a 50% substitution rate. Anhydrite and limestone additions improved the early strength development. This work further demonstrated that it is possible to convert 100% BR to valuable products. But the production of slags with a GBFS-like chemistry required the use of high quantities of slag-forming agents. Also, the process will be energy intensive and costly. Still, the approach can be economically viable, as several valuable products can be generated. The possible avoidance of landfilling or even torecovery landfill capacities presents another important economic benefit.
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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.
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Deposits of bauxite ores near aluminum smelters often possess an excessively high percentage of silica. Development of such high-silica ores would be beneficial to alumina producers. Therefore, unique industrial and operational experience in the field of high-silica bauxite processing was gained at the Russian National Aluminium-Magnesium Institute, St. Petersburg, pilot plant with the consecutive extraction of silica and alumina from low-grade ores. This article describes the chemistry, processing-unit operations, and results obtained from this process.
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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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Leach solutions and wastes of Bayer process are important resources for metals such as aluminum and vanadium. Despite the fact that vanadium cake is precipitated and removed in the Seydisehir Eti Aluminum Facility (Turkey), it cannot be used due to low metal content and impurities it contains. Within the scope of this study, research and development of environmentally acceptable, technically sound and low-cost chemical leaching and recovery methods were conducted for the recovery of vanadium from the by-product cake of the Bayer process. In the conducted studies, a sample of vanadium cake was used after its detailed characterization. Roasting tests were performed in order to remove the arsenic in the vanadium cake; however, it was found that roasting was not effective in removing the arsenic from the cake. The performance of different reagents were examined in chemical leaching tests (H2O and H2SO4 leaching, H2SO4 leaching with the addition of NaSO3, and NH4F); in the H2SO4 leaching tests performed with the addition of Na2SO3, the concentration of the reagents and the effect of temperature on the efficiency of vanadium recovery (max. 93.09%) were determined with the full factorial experimental design method, the outcomes were evaluated with ANOVA (variance analysis) method, and empirical models were formed. In lab and semi-pilot scale leaching tests, vanadium recoveries were 96.34% and 94.76% respectively. Vanadium was precipitated with NaOH and FeSO4 and almost all vanadium (95.8%) was obtained as Fe3(VO4)2. Cost analysis and economic evaluation have shown the economic feasibility of the leaching and recovery processes proposed.
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The article reviews the cathodic process of gallium ion reduction in alkaline solutions. The solution composition influence on the gallium anion reduction kinetics was analyzed by measuring the polarization curves on a dropping mercury electrode. Itwas found that the cathodic process rate is proportional to the specific adsorption of background cations in the sequence Na+ b K+ b Li+ b Cs+ b La3+. A higher rate of reduction of gallium anion present in alkaline solution of lithiumcation is a result of participation of thewatermolecules fromthe hydration shell of Li+ as a proton donor. In the presence of polyvalent lanthanum cations in alkaline solution, the gallium anion reduction rate increases sharply. This is related to a shift in the ƒÕ1-potential and participation of hydrated cations La(H2O)3 + n. The presence of surface-active agents,which have no proton.donor properties, in the solution, complicates the reduction reaction. Certain patterns of themechanism of the galliumion discharge reaction in alkaline solutions allowqualifying it as the second group of anions, and the slowstage of the reduction reaction comes down to simultaneous transfer of an electron and proton to the discharging anion. The estimated charge of the discharging gallium anion, which is equal to .0.24 in the transition state of the reaction, is indicative of formation of associates with background electrolyte cations [Me+ c GaO2], [Me+ c GaO(OH)2] by gallate anions in alkaline solutions („‚„N 12).
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World reserves of bauxite include vast quantities of ore which at present are sub-economic due to high levels of reactive silica that cause expensive loss of caustic soda during Bayer processing. As the economic reserves of high grade ores diminish, attention is turning to how these lower grade ores may be processed at reasonable cost. This paper presents a review of existing and potential processes from the open literature that have been proposed for high silica bauxites. The processes have been divided into three strategies for reducing soda loss. These are (i) reduce the input of reactive silica into the process (ii) modify the process to produce a low soda residue and (iii) recover caustic soda by re-processing residue. For each of the processes considered, a description of the principle is given along with the current status and any hurdles (economic, environmental etc) to implementation.For each strategy the review identifies the most promising processes for future consideration.
Red mud processing methods. Republic of Kazakhstan Innovation Patent
  • R A Abdulvaliev
  • S V Gladyshev
  • K O Beisembekovaet
Abdulvaliev, R.A.,Gladyshev, S.V.,Beisembekovaet, K.O., et al. 2012a. Red mud processing methods. Republic of Kazakhstan Innovation Patent, No. 25940.
Aluminate solution processing methods. Republic of Kazakhstan Innovation Patent
  • R A Abdulvaliev
  • S V Gladyshev
  • E A Tastanov
Abdulvaliev, R.A., Gladyshev, S.V.,Tastanov, E.A., et al. 2012b. Aluminate solution processing methods. Republic of Kazakhstan Innovation Patent, No. 25870.
Method of red mud hydrogarnet processing. Republic of Kazakhstan Innovation Patent
  • N S Bekturganov
  • L A Myltykbayeva
  • E A Tastanov
Bekturganov, N. S., Myltykbayeva, L.A.,Tastanov, E.A., et al. 2013c. Method of red mud hydrogarnet processing. Republic of Kazakhstan Innovation Patent, No. 27264.