Leaching Solution Research Articles

Advance review on occurrence state and leaching of lithium in sedimentary bauxite (aluminum) deposits, China

Bauxite-associated type Li resource is mainly discovered in the sedimentary bauxite (aluminum) deposits forming areas, especially Northern Guizhou-Southern Chongqing, Western Henan and Central Guizhou, China. This paper reviews the enrichment mechanism and occurrence states of Li in sedimentary bauxite (aluminum) deposits. The Li in these deposits is derived from underlying carbonate rock, and the favorable sedimentary environment, e.g., alternation climate of dry and humid, the marine-continental transitional zone with reduction-weak oxidation and low salinity, is conducive to the Li enrichment in these deposits. Li is mainly hosted by independent mineral (i.e., cookeite), partly adsorbed by montmorillonite, and rarely adsorbed by illite/kaolinite. Furthermore, the leaching methods and affecting factors of Li from bauxite-associated type Li resource are summarized. Acid solution is the main leaching solution, but its excessive use can generate abundant acidic residues, which have hazards to the environment. Thereby, leaching solution with little or no acid has been recommended. The affecting factors of Li leaching are the calcination temperature, leaching temperature, leaching time, liquid–solid ration and mineral particle size. The above summary deepens the understanding of the enrichment mechanism and occurrence states of Li in the sedimentary bauxite (aluminum) deposits, and has the potential to promote Li resource, initially considered uneconomical, become an important economic source of Li.

Methylation and bio-accessibility assessment of arsenate in crickets (Gryllusbimaculatus)

The ability of an organism to biomethylate toxic inorganic arsenic (As) determines both, the amount of As available for uptake higher up the food chain and the toxicity of bioavailable As. An exposure study was conducted to determine ability of farmed crickets to metabolize dietary arsenate. Crickets were exposed to 1.3 ± 0.1, 5.1 ± 2.5 and 36.3 ± 5.6 mg kg−1 dietary arsenate and quantitation of total As showed retention of 0.416 ± 0.003, 1.3 ± 0.04 and 2.46 ± 0.09 mg kg−1, respectively. Speciation analysis revealed that crickets have well developed ability to biomethylate dietary arsenate and the most abundant methylated As compound was DMA followed by MMA, TMAO and an unknown compound. Arsenobetaine, although present in all feed, control and As-rich, was measured only in the control crickets. To assess the bio-accessibility of the As species, crickets were subjected to simulated gastrointestinal digestion. The results showed that majority of As was extracted in saliva, followed by gastric and intestinal juice, which mass fraction was equal to residue. Over 78% of total As was shown to be bio-accessible with methylated species reaching 100% and iAs over 79% bio-accessibility. Additionally, arsenite and arsenate have shown different distributions between sequential leachate solutions. Bioaccumulation of As was observed in the studied crickets although it does not seem to occur to the same extent at higher exposure levels.

Gold Recovery from Thiosulfate Leaching Solution Using Silicon Powder and Electrochemical Monitoring of Its Process

Gold recycling from Waste Electrical and Electronic Equipment (WEEE) has been actively conducted. We previously reported a noble metal recovery process using aqua regia and electroless displacement deposition onto silicon powder [1,2]. Using silicon powder has such advantages as that noble metals and copper are selectively recovered, and sawdust silicon, that is, industrial waste silicon powder is available to use. Recently, ammonium thiosulfate solution has attracted attention as a safe and low-cost solution for gold leaching [3-6]. In this study, we successfully recovered gold from an ammonium thiosulfate solution by using silicon powder [7,8], and tried to monitor the recovering behavior electrochemically. Since the ammonium thiosulfate leaching solution includes copper ions as oxidizing agent, copper is recovered by silicon powder. Thus, the monitoring was conducted in order to determine the suitable timing for efficiently obtaining pure gold during the process. For experimentation, an ammonium thiosulfate solution containing gold(I) sulfite and copper(II) sulfate was prepared (pH = 13). We immersed a gold wire in the solution and measured the rest potential during the recovery process using silicon powder. The potential of gold wire shifted stepwise toward negative direction at each start and end of gold and copper recovery. The results suggest that the efficient recovery of high-purity gold can be achieved by monitoring the potential of gold.[1] K. Fukuda, S. Yae, N. Fukumuro, S. Sakamoto, and H. Matsuda, ECS Trans., 53(19), 69 (2013). DOI: 10.1149/05319.0069ecst[2] K. Fukuda, N. Fukumuro, S. Sakamoto, and S. Yae, ECS Trans., 61(10), 1 (2014). DOI: 10.1149/06110.0001ecst[3] M.G. Aylmore and D.M. Muir, Miner. Eng., 14, 135 (2001). DOI: 10.1016/s0892-6875(00)00172-2[4] H. Arima, T. Fujita, and W. Yen, Mater. Trans., 43, 485 (2002). DOI: 10.2320/matertrans.43.485[5] S. Syed, Hydrometallurgy, 115-116, 30 (2012). DOI: 10.1016/j.hydromet.2011.12.012[6] B. Xu, W. Kong, Q. Li, Y. Yang, T. Jiang, and X. Liu, Metals, 7, 222 (2017). DOI: 10.3390/met7060222[7] Y. Iwai, Y. Takashima, A. Matsumoto, and S. Yae, Abst. Interfinish2020 20th world congress, P-E2-001 (2021).[8] Y. Takashima, A. Matsumoto, Y. Iwai, S. Arita, and S. Yae, J. Surf. Finish. Jpn., 73, 98 (2022). DOI: 10.4139/sfj.73.98

Electrodialysis of Lithium Sulfate Solutions from Hydrometallurgical Recycling of Spent Lithium-Ion Batteries

Recycling lithium-ion battery materials is a crucial step to achieving a circular economy. A hydrometallurgical recycling process of spent lithium-ion battery materials involves leaching by acids and precipitation by bases. A large amount of Li2SO4 leachate solution is generated at the end of the recycling process. Such Li2SO4 solution can be separated by electrodialysis (ED) to form H2SO4 and LiOH solutions, which are reused for leaching and precipitation, respectively, making the recycling a closed-loop process. In this study, an ‘electrodialysis stack constructed with bipolar membranes’ (EDBM) is built with repetitive unit cells consisting of a bipolar membrane, anion exchange membrane (AEM), and cation exchange membrane (CEM), see Fig. 1(a). The effective area for each membrane is 121.8 cm2 (70mm×174mm). The gap between these membranes is 0.8mm, with a mesh inserted to allow flow mixing. All experiments were operated at constant current mode. The feed, acid, and base solutions were recirculated through their tanks at initial concentrations of 1.1, 0.1, and 0.1 mol/L. The ion concentrations of the solutions were measured with Inductively coupled plasma mass spectrometry periodically. The weight and the pH value of the solution tanks were also recorded.The trend of concentration variations of the present stack with up to 6 cell pairs is found to be consistent with that observed with a three-compartment configuration in our previous study [1]. The concentration of H2SO4 increases with time linearly, whereas that of LiOH levels off due to a significant electro-osmosis that drags water through the CEM into the concentrate channel. The present setup differs from the three-compartment design in the bipolar membrane, which splits water to produce H+ and OH- at the internal interface, eliminating the formation of bubbly flows in the unit cell. It is found that the voltage loss across the bipolar membrane ca. 1V accounts for a major part of the unit cell of about 1.27V.The effects of current density, number of cell pairs, and flow rates on the overall stack performance are investigated. Increasing the stack current density accelerates the separation process at the cost of higher voltage losses. It is found that increasing the number of cell pairs can improve the overall production efficiency and reduce energy consumption per cell pair. For instance, at 800 A/m2, the specific energy consumption for LiOH production is reduced to 3.40 kWh/kg with five cell pairs versus 5.83 kWh/kg with two cell pairs. It is also found that increasing the solution flow rate can result into the increase of LiOH solution concentration, ion recovery rate, and current efficiency (Fig. 1b), although the impact of flow rate is low.A small EDBM stack is constructed and tested for Li2SO4 separation in the present study. This work demonstrates that EDBM can be a simple and energy-saving alternative to the current chemical precipitation method to produce LiOH from Li2SO4. The present study provides new insights into optimal operation and design for Li2SO4 EDBM. The findings are helpful in determining how the stack can be scaled up for practical application. Furthermore, a 2D multiphysics model is currently under development to elucidate the coupled transport processes within the unit cell. The model will be validated with experimental data of the present setup. Figure 1

Recovery of uranium from conversion production sludge by leaching with nitric acid and subsequent ion-exchange concentration

Physicochemical studies of the sludge of uranium conversion production were carried out to determine the possibility of its processing and return of uranium to the nuclear fuel cycle. It has been established that the sludge was mainly represented by calcium compounds: CaSO4·2H2O (60.1 wt%), CaCO3 (25.1 wt%), CaF2 (13.7 wt%), and silicon dioxide (1.2 wt%). The content of uranium in the sludge was 0.15 wt%. It was shown that it was possible to achieve high degrees of uranium extraction from the sludge using nitric acid as a leaching agent. The use of phosphorus-containing ion-exchanger Tulsion CH93 ensured the effective concentration of uranium from highly acidic pregnant leach solutions. The full dynamic exchange capacity achieved 15.7 kg m−3. The degree of uranium desorption by ACBM (ammonium carbonate/bicarbonate mixture) solutions was 83%. The final product was ammonium uranyl phosphate hydrate NH4UO2PO4∙3H2O with a uranium content of 52.5 wt%.

Liquid membrane coupled electrodialysis system for highly-efficient lithium recovery from fly ash acid leaching solution

Recovering lithium (Li) from high Li-bearing coal fly ash (CFA) is a challenging task due to CFA's complexity and minor content of Li. Acid leaching is a common treatment, but it faces the difficulties of complex leaching solution and selective separation of Li+. This work evaluated a liquid membrane coupled with the electrodialysis (LME) system to separate Li+ from the CFA leach liquor. The liquid membrane (LM) performs as an ion carrier to selectively transport Li+, while the electric field can drive the ion migration. The results show that the LM TBP+[HOEmim][NTf2] (v/v, 5:5) exhibits the best recognition and releasing ability toward Li+. The selective migration of Li+ can be achieved in acidic environment in the presence of concentrated Al3+. The Al/Li ratio decreases from 30 of the feed to 0.55 in the receiving solution after 12 h at 3 V. The practical application in the CFA leach liquor indicates that the system has preferential selectivity for transmembrane transport of Li+, while other multivalent ions were mostly hindered. This work presents a new idea for Li recovery from the solid waste residues, and offers a deep insight into the separation of valuable metal ions from complex solutions.

Solvent extraction of scandium from leaching solution of red mud roasted with ammonium sulfate using D2EHPA/TBP

Red mud is an important secondary resource for scandium production. The red mud leaching solution containing scandium in this study was derived from environmentally friendly ammonium sulfate roasting and water leaching process. A synergistic extraction with a mixture of di(2-ethylhexyl) phosphate acid (D2EHPA) and tributyl phosphate (TBP) for recovery of scandium from red mud leaching solution is proposed. The effects of D2EHPA concentration, H2SO4 concentration, rare earth elements, dosage of TBP, phase ratio (A/O), contact time and H2O2 concentration on scandium extraction were investigated. The results show that more than 99% scandium is extracted under the optimal conditions while Fe, Al, Ti, Ca and rare earth elements (Ce, Y, La, Nd, Er, etc.) are hardly extracted. The stripping efficiency of Sc reaches above 92.37% under the optimal stripping conditions of 5 mol/L NaOH with an A/O of 1 at 90 °C for 30 min. The proposed technology could provide an effective method for extraction of scandium from red mud leaching solution.

The priority leaching of lithium from spent LiFePO4 cathode without the oxidization

Due to the scarcity of Li resources and the environmental burden, comprehensive and efficient recycling of spent LiFePO4 batteries has attracted extensive attention. The existing recycling strategy still has obstacles of low Li recovery efficiency and high consumption of acid and base. The pressure leaching was proposed to extract Li from the spent LiFePO4 cathode selectively without oxidization. The process is mainly to fix the Fe and P in the residue and the Li into the water phase, reducing the reagent consumption and the burden of subsequent removal of Fe and P. More than 99 % of Li could be extracted into the solution under optimal conditions, and it avoided the entrance of the impurities Al and Ca into the leaching solution. The extraction mechanism indicated that the selective extraction of Li and the precipitation of Fe3(PO4)2‧8H2O were carried out stepwise. In addition, the leaching solution was used to prepare high-purity Li2CO3 products and leaching residue could be applied to produce battery-grade FePO4. This process puts forward a new approach to recovering Li from spent LiFePO4 batteries, which has the advantages of high efficiency, reagent cost savings, and easy operation.

Biooxidation of refractory silver minerals as pretreatment for silver recovery

The worldwide demand for silver is increasing due to the technological development in different areas, especially for the requirements in the production of renewable energies; therefore, for the treatment of refractory minerals by conventional processes, it is necessary to study mechanisms to identify the viability of their processing and the feasibility of their recovery, ensuring profitability. Gold and silver present in the matrix of sulfide-based ores are not affordably recovered by the conventional method involving leaching in sodium cyanide solution. Therefore, it must be subjected to oxidation pretreatment or conversion of the sulfides to simple compounds that allow recovery of the precious metals. The methods of oxidation of minerals considered refractory are carried out by hydro and pyrometallurgical methods, seeking the dissolution of sulfur, iron, arsenic and other elements present. It is important to identify and consider the mineralogical structure, microbiological variety, physicochemical characteristics, types of reactors, bacterial interactions, among other factors. The choice of biooxidation as the preferred process in projects for the recovery of gold, silver, copper or other metals, in most cases is based on the economic advantage, compared to the conventional processes of roasting, chemical leaching and pressurized leaching. The biooxidation of refractory argentiferous ores has been extensively studied in recent years, concluding that its application is feasible, mainly because it is environmentally friendly.

TREATMENT OF LEACHATE FROM ERBIL LANDFILL SITE BY ELECTRO- AND CHEM-ICAL COAGULATION METHODS

Landfill leachate is commonly heavily contaminated wastewater. and consists of a high number of organic compounds, inorganic salts, toxic gases and heavy metals that exert a serious threat to the environment and public health. Thus, it requires treatments before direct release into receiving waters. This paper presents the results of electrocoagulation (EC) and chemical coagulation (CC) treatment of leachate from the Erbil landfill site. The removal efficiency of chemical oxygen demand (COD), phosphate (PO43-), total suspended solids (TSS), total organic compound (TOC), and color of leachate was studied using iron and aluminum electrodes. The removal percentages were also compared to those produced by electrochemically generated Fe2+ and Al3+ dosages. The effect of different pH values on the removal efficiency of these parameters was evaluated at optimal conditions. The removal percentages for chemically added coagulants were lower than those for electrochemically generated Fe2+ and Al3+. In EC, the highest COD removal efficiency of 92% and 87% was achieved at the original concentration (C1) for iron and aluminum electrodes, respectively. The iron and aluminum electrodes also showed a maximum color removal of 90% and 95%, respectively, for the original undiluted leachate solution. Both Fe and Al electrocoagulation methods were not effective in removing TOC from the leachate of municipal solid waste. The highest removal efficiency of 78% was achieved at a 1:4 diluted solution (C2) using the Al-electrocoagulation method. The maximum removal percentage for PO43- was 94% at C1 using the Fe-electrocoagulation system. However, both systems were not very effective in removing TSS.

Geopolymerization of MSWI fly ash and coal fly ash for efficient solidification of heavy metals: Insights into stabilization mechanisms and long-term leaching behavior

High levels of heavy metals (HMs) are present in municipal solid waste incineration fly ash (MSWI-FA), which requires proper management before landfilling. The aim of this study is to investigate the feasibility of co-disposal of MSWI-FA and coal fly ash (Coal-FA) using geopolymerization technology to solidify heavy metals and to analyze the long-term leaching behavior of heavy metals (HMs). The active silicon, aluminum, and calcium present in MSWI-FA and Coal-FA are essential for the synthesis of geopolymers. The geopolymer with 20 wt% MSWI-FA (M20) achieved the maximum compressive strength of 25.73 MPa, mainly due to the formation of C-A-S-H gels. Heavy metals were effectively immobilized and met the limits of GB18598–2019. The compressive strength of M20 was decreased by 1.6% in sulphuric acid-nitric acid leaching solution for 64 days, but decreased by 57.4% in the acetic acid leaching solution. The geopolymer was more stable in the acid rain environment, resulting in less leaching of heavy metals. The bulk diffusion model (BDM) and Finite Element Method (FEM) could satisfactorily describe the leaching behavior of HMs. The results provide valuable guidance for future waste management practices and the development of solidification processes for MSWI-FA.

Crystallization kinetics of iron (oxyhydr)oxides from zinc leaching solution at 95–150°C based on the Avrami equation

ABSTRACT Here, the Avrami equation was employed to investigate the crystallisation process of iron (oxyhydr)oxides from the ZnSO4–FeSO4 solution. Hydrothermal conditions were as follows: initial Fe2+ concentration = 5–15 g L−1, Zn2+ concentration = 130 g L−1, temperature = 95–150°C, oxygen partial pressure (PO2) = 0.03–0.73 MPa, agitation speed = 300–600 rpm, seed addition = 5 g L−1. Results showed that increasing temperature, PO2, and agitation speed can increase the crystallisation efficiency. The crystallisation activation energy of iron (oxyhydr)oxides is about 104.2 kJ mol−1. During crystallisation, the goethite phase first transforms to hydro-haematite, then to haematite. In contrast, aggregates (precipitated at PO2 = 0.73 MPa) with high-density acicular crystal have more holes that can adsorb the ZnSO4 solution than spherical crystal aggregates (precipitated at PO2 = 0.03–0.33 MPa). Therefore, to produce high-grade crystallisation products while improving iron removal efficiency, the optimal conditions were controlled as follows: T = 150°C, PO2 = 0.3–0.4 MPa, agitation speed = 500 rpm, t = 180 min and adding seeds of 5 g L−1. The resultant (oxyhydr)oxides products containing > 55% Fe, < 1% Zn and < 3% S. Moreover, adding neutralisers can significantly increase the crystallisation efficiency and thus improve iron removal efficiency.

Selective recovery of gold and silver from electronic wastes through a sequential process of Qalkari and room-temperature hydrometallurgy

This work was focused on the selective recovery of gold and silver from electronic wastes using a sequential process of pyrometallurgy (Qalkari) and room-temperature hydrometallurgy. In the first step, electronic wastes underwent Qalkari recycling, yielding tablets containing precious elements (Qalkari furnace product) and melting slag (Qalkari furnace waste). In the subsequent hydrometallurgy phase, the nitric acid concentration and the input solid amount were optimized for the effective room-temperature recovery of gold. Due to the successful separation of precision elements and disturbing substances in Qalkari, the gold recovery efficiency of 99.99% was obtained at the acid concentration of 50% (v/v) and the solid input of 15% (w/v). Afterwards, HCl, NH4Cl, and NaCl were used for silver recovery from the Qalkari-processed gold-recovered leaching solution, leading to the efficiency of 99.99%. But NH4Cl was recognized as the most effective precipitant as it promises the most enhanced potential for the possible subsequent recovery of palladium. In conclusion, this study draws the effectiveness of Qalkari in recycling electronic wastes, with a significant impact on the efficiency of succeeding room-temperature hydrometallurgical processes for gold and silver recovery within a reasonable leaching time.

Platinum recycling from fuel cell-spent electrocatalysts using oxidative leaching in HCl solution

The recovery of platinum (Pt) from electrocatalysts in spent proton exchange membrane fuel cells is promising and important for the sustainable development of such a noble metal. Conventional leaching of Pt in the aqueous phase typically requires the use of high concentration of mineral acids and the presence of strong oxidants owing to its thermodynamic stability and non-reactive properties. In the present study, the dissolution of Pt from a Pt/C fuel cell electrocatalyst was investigated using a simple and efficient process under moderate conditions in chloride media. Notably, the leachability of Pt was high ∼76% in a solution of low concentration HCl 2.0 M at 90 °C for 120 min in the absence of an oxidant. The enhancement of Pt leaching efficiency can be obtained using various oxidizing agents HNO3, H2O2, NaClO and NaClO3, and NaClO3 shown the most effective improvement from 76% to 88%. The dissolution of Pt in a solution of 2.0 M HCl and 3.0 wt% NaClO3 improved to 98% by the increase in leaching temperature from 50 to 90 °C. Kinetic studies indicated that Pt leaching in HCl in the presence of NaClO3 followed a chemical-controlled mechanism with an activation energy (Ea) of 40.6 kJ/mol. Based on the findings of this study, an efficient process is proposed to recover and reuse Pt from an electrocatalyst sample of spent fuel cells, including oxidative leaching, chemical precipitation and laser reduction.

Precipitation of manganese by ozone from hydrometallurgical recycling process of lithium-ion batteries

The increasing demand for clean transportation facilities has significantly contributed to the rise in electric vehicle sales. However, it needs the development of effective strategies for battery disposal. Regarding the circular economy, the recovery of materials from these batteries is crucial for the supply chain. The current purification methods for manganese separation from lithium nickel manganese cobalt oxide (NMC) battery recycling present some limitations and low selectivity. In this work, a novel approach for manganese recovery from leach solution of NMC battery recycling is presented. The use of ozone permits the recovery of manganese without adding any other element to the system. With the right conditions, settled through simulations, the ozonation technique has proven to be highly effective, enabling the recovery of 100% with manganese 97.6% purity. Optimal conditions for this process were determined, as reaction time of 405 min, oxygen flow rate 1 L/min, and 8.9 g of ozone to oxidize 3.6 g of Mn.

The sustainable recovery of rare earth in the leaching solution of Baotou minerals with extraction-precipitation strategy based on fatty acids

To research and develop sustainable extraction-precipitation strategy, the recovery of rare earth (RE) was studied by using mono and binary carboxylic acids, namely lauric acid (LA), myristic acid (MA), sebacic acid (SA) and dodecanedioic acid (DA). Compared with the other carboxylic acids, LA has better precipitation performance and selectivity for RE. It was successfully used to concentrate the leaching solution of Baotou minerals to 227 g/L. RE sulfate was also transformed into RE chloride with high solubility. Ca and Mg impurities in the leachate can be effectively eliminated. The particle size of formed RE concentrate is obviously larger than that those produced by industrial precipitants, which helps to improve the separation efficiency. Unlike oxalic acid and ammonium bicarbonate, the extraction-precipitant studied in this article can be reused to avoid the generation of oxalic acid wastewater, ammonia nitrogen wastewater, and carbon dioxide. The obtained RE concentrates have good separation performances and low solubilities in aqueous phase. The mechanism of RE extraction-precipitation by LA was examined by slope analysis, XPS and IR spectra. LA showed good stability during the recovery and recycling processes. Based on the above research, the extraction-precipitation of fatty acid (FA) provides a simple, efficient and sustainable separation process for Baotou minerals.

Draft genome sequence of Acidiplasma cupricumulans strain BH2T, isolated from a pregnant leachate solution of heap bioleaching.

We report the draft genome sequence of a type strain Acidiplasma cupricumulans Strain BH2T, isolated from a pregnant leachate solution of industrial-scale chalcocite bioleach heap (Monywa, Myanmar). The genome is 1.7 Mbp long with a GC content of 34.2%.

Fe3+ and Al3+ removal by phosphate and hydroxide precipitation from synthetic NMC Li-ion battery leach solution

The removal of trivalent iron and aluminum was studied from synthetic Li-ion battery leach solution by phosphate and hydroxide precipitation (pH 2.5–4.25, t = 3 h, T = 60 °C). Phosphate precipitation exhibited both crystal nucleation initiation (pH 2 vs. pH 3) as well as complete (~ 99%) Fe and Al removal at lower pH compared to hydroxide precipitation (pH 3 vs. 3.5). The precipitation time of phosphate was shorter (40 min) than that of hydroxide precipitation (80 min). At pH 4 the loss of valuable metals (Li, Ni, Co) in the precipitate was negligible in the phosphate cake, whereas in the hydroxide process the co-precipitation was 4–5% for Li, Ni and Co. The filtration rate of phosphate precipitate was shown to be significantly faster. The presence of fluoride did not have any notable effect on phosphate precipitation, whereas in hydroxide precipitation, it potentially had a negative effect on aluminum extraction.

Integrated Circular Economy Model System for Direct Lithium Extraction: From Minerals to Batteries Utilizing Aluminum Hydroxide.

Aluminum hydroxide, an abundant mineral found in nature, exists in four polymorphs: gibbsite, bayerite, nordstrandite, and doyleite. Among these polymorphs gibbsite, bayerite, and commercially synthesized amorphous aluminum hydroxide have been investigated as sorbent materials for lithium extraction from sulfate solutions. The amorphous form of Al(OH)3 exhibits a reactivity higher than that of the naturally occurring crystalline polymorphs in terms of extracting Li+ ions. This study employed high-temperature oxide melt solution calorimetry to explore the energetics of the sorbent polymorphs. The enthalpic stability order was measured to be gibbsite > bayerite > amorphous Al(OH)3. The least stable form, amorphous Al(OH)3, undergoes a spontaneous reaction with lithium, resulting in the formation of a stable layered double hydroxide phase. Consequently, amorphous Al(OH)3 shows promise as a sorbent material for selectively extracting lithium from clay mineral leachate solutions. This research demonstrates the selective direct extraction of Li+ ions using amorphous aluminum hydroxide through a liquid-solid lithiation reaction, followed by acid-free delithiation and relithiation processes, achieving an extraction efficiency of 86%, and the maximum capacity was 37.86 mg·g-1 in a single step during lithiation. With high selectivity during lithiation and nearly complete recoverability of the sorbent material during delithiation, this method presents a circular economy model. Furthermore, a life cycle analysis was conducted to illustrate the environmental advantages of replacing the conventional soda ash-based precipitation process with this method, along with a simple operational cost analysis to evaluate reagent and fuel expenses.

Selective recovery of lithium from high-aluminum fly ash by using alkali-dissolution-assisted HBTA–TOPO synergistic extraction

The process of recycling lithium (Li) from common coal fly ash using strong acids can release substantial quantities of hazardous low-value residues, and the complex ionic composition of the acidic leaching solution hinders the selective extraction of Li. Accordingly, a green and economical approach was developed for the selective recovery of Li and extraction of valuable Al-rich residues from high-alumina fly ash (HAFA). In HAFA, the glass phase (the main Li-bearing phase) can be selectively dissolved in the mild NaOH solution at 95 °C for 2 h, and valuable mullite phase (the main Al-bearing phase) was retained in the leaching residue (Al2O3 content 49.00 wt%). The leaching efficiencies of Li, Si, and Al were 91.60%, 43.19%, and 3.56%, respectively. Among the primary metallic elements present in HAFA, only Li, Na, K, and Al in the glass phase were readily dissolved in the alkaline solution. Meanwhile, the synergistic extraction system of HBTA and TOPO has good complexing ability with Li + compared to Al3+, K+, and Na+. Therefore, Li+ can be selectively extracted from alkaline leaching solutions using HBTA and TOPO. The Li extraction efficiency reached 99.68% after three consecutive extractions under the optimal conditions. Finally, the used alkali leaching solution and synergistic extractants can be regenerated via Ca(OH)2 precipitation and HCl reverse extraction. These findings can provide new strategies for the green and overall utilization of HAFA.