Acid Leaching Solution Research Articles

From waste to material strategy: A closed-loop regeneration process of spent LiFePO4 batteries

A closed-loop regeneration route to recover valuable elements from spent LiFePO4 batteries is proposed. After hot-acid leaching, the leaching rates of Li, Fe and P are above 99.8 %, and the graphite powder retain in the residue with grade of 93.33 %. With iron powder cementation, 99.96 % Cu is removed from acid leaching solution to obtain sponge copper. And then 96.67 %Al and 89.30 %F are precipitated in the form of AlPO4(s) and FeF3(s) at pH = 3.75. Li, Fe and P within the purified solution are prepared as LiFePO4 precursors by co-precipitation method, and finally LiFePO4/C materials are synthesized after two-stage calcination. The recycled LiFePO4/C materials demonstrate excellent electrochemical performance with a discharge capacity of 153.1 mAh·g−1 at 0.1C and a capacity retention of 94.0 % after 500 cycles at 1C. The present recycling process provides a strategy for short and efficient regeneration of spent LiFePO4 batteries.

Thiourea-linked covalent triazine frameworks enable efficient and selective gold recovery from e-waste leachate

The surging electronic waste (e-waste) has been stimulating the unremitting exploration about the advanced gold recycling technology, which is of great significance to alleviate the shortage of metal resources and minimize the negative environmental impact. Herein, the thiourea-linked covalent triazine frameworks (denoted as PbTu-CTFs) have been designed and constructed by the nucleophilic substitution between cyanuric chloride (CC) and 1,4-phenylene bis(thiourea) (named PbTu) for gold recovery from the actual e-waste leachate. Benefiting from the unique structural characteristics, including large surface areas, abundant porosity, excellent chemical stability, and high-density S, N coordinative sites, the fabricated PbTu-CTFs afford ultrahigh gold adsorption capacity up to 2255 mg/g and fast kinetics, as reflected by 99 % of Au recovery efficiency within 5 min. Meanwhile, satisfactory recyclability and regeneration are maintained after six rounds of consecutive adsorption/desorption tests. Furthermore, the resulting adsorbent is well competent for highly efficient and selective gold recovery from the acidic leaching solution of wasted central processing unit (CPU), exemplify its promising actual application potential.

Extraction of molybdenum, cobalt, and nickel from acidic leach solution of molybdenum leach residue of spent hydrodesulfurization catalyst

ABSTRACT After the extraction of molybdenum from the spent HDS catalyst, a residue containing aluminum, nickel, cobalt, and a small amount of molybdenum was obtained. The simultaneous recovery of nickel, cobalt, aluminum, and residual molybdenum from molybdenum leach residue can be achieved through hydrochloric acid leaching. In the work presented herein, the extraction of molybdenum, cobalt, and nickel from the acidic leach solution of molybdenum leach residue was investigated. Trioctyl tertiary amine can selectively extract cobalt and molybdenum from the acidic leach solution, the extraction of both cobalt and molybdenum reached more than 99% after two-stage countercurrent extraction. The combination of pure water and 25% ammonia water can be utilised for the separation and extraction of cobalt and molybdenum from the loaded cobalt-molybdenum organic phase. After the extraction of cobalt and molybdenum, a synergistic extraction system comprising decyl 4-picolinate and dinonylnaphthalene sulfonic acid can be employed for nickel extraction, achieving a nickel extraction exceeding 99.70% while maintaining aluminum extraction at only 0.32% after undergoing four-stage countercurrent extraction. The nickel stripping efficiency can reach 99.50% after four-stage countercurrent stripping, using a stripping agent of 2 mol/L H2SO4.

Synthesis of LiNi0.9Co0.05Mn0.05O2 and modification with co-doping of Zr4+ and W6+ using acid leaching solution from spent lithium-ion batteries

Synthesis of LiNi0.9Co0.05Mn0.05O2 and modification with co-doping of Zr4+ and W6+ using acid leaching solution from spent lithium-ion batteries

Separation of Co(II), Mn(II), and Ni(II) by solvent extraction with Cyanex 272 and D2EHPA from the sulfuric acid leaching solution of spent lithium-ion batteries

Spent lithium-ion batteries contain valuable metals such as cobalt, lithium, manganese and nickel. Smelting reduction of spent LIBs at high temperature results in metallic alloys. Therefore, it is necessary to recover the valuable metal ions present in the sulfuric acid leaching solutions of the metallic alloys. In this work, solvent extraction experiments were performed to separate the three metal ions, Co(II), Mn(II) and Ni(II) present in the leaching solutions of the metallic alloys. Synthetic sulfate solutions were prepared and commercial organophosphorous extractants were employed. First, both Co(II) and Mn(II) were completely extracted in one stage by using 40% saponified 0.3 M Cyanex 272, leaving Ni(II) in the raffinate. The small amount of Ni(II) co-extracted into Cyanex 272 was removed by two stages of cross-current scrubbing using pure CoSO4 solution. The effect of pH and CoSO4 concentration of the scrubbing solution on the scrubbing of Ni(II) was investigated. The Co(II) and Mn(II) present in the scrubbed Cyanex 272 were completely stripped by 0.05 M H2SO4 solution. Batch simulation experiments for the three stage of counter-current extraction with 1 M D2EHPA verified that Mn(II) and Co(II) were completely separated by selective extraction of Mn(II) into D2EHPA, leaving Co(II) in the raffinate. By consecutive extraction with Cyanex 272 and D2EHPA, pure solutions of Co(II), Mn(II) and Ni(II) with purity higher than 99.9% can be recovered from the starting solutions. A process was proposed for the treatment of sulfuric acid leaching solutions of spent LIBs containing Co(II), Mn(II) and Ni(II) by solvent extraction.

Efficient and selective extraction of gold from acidic leaching solutions using novel guanidinium ionic liquid

As gold is a non-renewable resource, it holds both economic and environmental importance to enhance the recycling of precious metal waste from secondary resources. Herein, a guanidine salt ionic liquid ([DIETMG][NTf2]) with low water solubility and viscosity was synthesized by molecular design of guanidine salt ionic liquid with good biocompatibility and biodegradability, and a solvent-free system of [DIETMG][NTf2]-water was constructed to extract Au(Ⅲ). The findings reveal that the extraction efficiency of Au(Ⅲ) can reach 97.57 % under optimal extraction conditions. Further thermodynamic and kinetic studies revealed that the reaction process is spontaneous and exothermic, with the extraction rate being primarily controlled by interfacial chemical reactions. The system demonstrates remarkable selectivity for Au(Ⅲ) in solutions containing a mix of various metal ions. Finally, ascorbic acid (Vc) was employed as a stripping agent to obtain gold at room temperature. After 8 cycles, [DIETMG][NTf2] still achieved a 90% extraction efficiency. This study provides a new idea and method for recovery of gold from secondary resources.

Effect of manganese(II) and magnesiumg(II) in zinc acid leaching solution on iron precipitation via the hematite process

Abstract Iron (Fe) removal is a critical step in the hydrometallurgical zinc (Zn) extraction process. Hematite, a stable Fe precipitate, offers an environmentally friendly option that complies with environmental protection standards. While existing research primarily focuses on hematite process technology, there is a lack of studies on how ions in ZnSO4 leaching solutions affect Fe removal efficiency and hematite particle size distribution. This study investigated the influence of manganese II (Mn(II)) and magnesium II (Mg(II)) concentrations and temperature on both Fe removal efficiency and hematite particle size distribution in ZnSO4 leaching solution. The results indicated that at various temperatures, the highest Fe removal efficiency occurred with an initial Mn(II) concentration of 10 g/L and an Mg(II) concentration of 15 g/L. As the concentrations of Mn(II) and Mg(II) as well as temperature increased, FeSO₄ crystallization also increased, which adversely affected hematite precipitation. The average particle size of hematite decreases from 300 to 100 nm, resulting in a more uniform particle size distribution, which correlated with the homogeneous solution saturation precipitation mechanism. However, the number of rod-shaped, regular small particles decreases, while the number of irregular, blocky particles increased.

Effect of pH neutral on the separation of nickel and cobalt from laterite leaching solution using cyanex 272

Abstract Nickel and cobalt are the most common elements in the earth’s crust that naturally occur in laterite ores. Nickel and cobalt from laterite ores are recovered as products such as mixed hydroxide precipitate (MHP) and mixed sulphide precipitate (MSP). This research focuses on how the nickel laterite leach solution can be processed directly for solvent extraction without going through the precipitation stage. The nitric acid leach solution obtained from the laterite ore is used to extract nickel and cobalt. A cyanex 272 extractant and kerosene mixture will be used as an organic solvent for direct extraction. The raw material used was Indonesian laterite ore from Halmahera Island, which contained Ni (1.72%), Co (0.155%), Fe (26.17%), and other minor elements. The effect of pH in a neutral condition was investigated on the extraction efficiency, distribution coefficient, and separation factor. Nitric acid (1M) was applied as the leaching reagent. The variables include pH variations (6.8; 7.0; 7.2; 7.4; 7.6), 20% cyanex 272, and O/A ratio (1:1/v:v) at 20 minutes with a stirring speed of 500 rpm. Optimum results were obtained at pH 7.4 variation with an extraction efficiency of 69.26% for cobalt and 0% for Ni, respectively. At these optimum conditions, the highest distribution coefficient value is the element cobalt at pH 7.4, and the result is 2.253 with a separation factor (∞). The optimum condition focuses on removing cobalt from the organic phase, not nickel.

Nitrogen recovery from biogas slurry with high ammonia nitrogen concentration through struvite precipitation utilizing acid leaching solution of collophanite tailings

ABSTRACT The high concentration of ammonia nitrogen (NH4+) and chemical oxygen demand (COD) in biogas slurry pose great challenges to the efficiency of traditional wastewater treatment systems. Collophanite tailings are solid waste, characterized by significant concentrations of phosphorus (PO43-) and magnesium (Mg2+), represent a potential resource for the reduction and recovery of NH4+ in biogas slurry via struvite precipitation. This study systematically explored the optimal leaching parameters employing sulfuric acid for the extraction of PO43− and Mg2+ from collophanite tailings. The effect of [PO43-]:[NH4+] molar ratio and pH on the recovery of NH4+ in biogas slurry was investigated. The physicochemical properties of the precipitates were confirmed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and chemical analysis. Results suggested that the highest removal efficiency of NH4+ (88.5%) was achieved when employing a [PO43-]:[NH4+] molar ratio of 1.0 at pH 9.5. Evaluation of effluent quality demonstrates a significant enhancement in the biodegradability of the treated biogas slurry, evidenced by an increase in the COD/TN ratio increased from 2.1 to 10.4. Economic analysis shows that the net income would be approximately 21.33 USD/m3 for proposed produces. These findings underscore the potential of utilizing collophanite tailings for NH4+ recovery from biogas slurry.

Highly effective and selective recovery of germanium from coal acid leaching solution by trihydroxyl functionalized titanium dioxide

In this study, a novel trihydroxyl functionalized titanium dioxide (TiO2-NH2-3OH) was successfully synthesized by the Schiff base reaction method. TiO2-NH2-3OH was characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR), x-ray Photoelectron Spectroscopy (XPS), x-ray diffraction techniques (XRD), and further applied to recover germanium (Ge(IV)) from coal acid leaching solution. TiO2-NH2-3OH exhibited superior capture performance on Ge(IV) at a pH of 3, and the optimal TiO2-NH2-3OH dosages were 0.8 g L−1. The distribution coefficients of germanium for coexisting metal ions (Zn2+, Co2+, Mn2+, Ni2+ and Al3+) were all greater than 1, indicating that TiO2-NH2-3OH had good selective adsorption performance for Ge(IV) in complex solution environments. Compared with other kinetic models, pseudo-second-order model was more suitable to reveal the absorption of Ge(IV). Moreover, the experiment data were fitted better with Langmuir model at 298 K than the other isothermal models, and the maximum adsorption capacity was up to 72.94 mg g−1. Thermodynamic data suggesting that the capture of Ge(IV) on TiO2-NH2-3OH was a spontaneous endothermic process, increasing the temperature was beneficial for the adsorption reaction to proceed. TiO2-NH2-3OH with saturated adsorption still maintained a high removal rate of 80.55 % of Ge(IV) after five cycles, indicating good stability and recyclability of TiO2-NH2-3OH. XPS analysis indicated that the capture of germanium by TiO2-NH2-3OH may be due to the ion exchange interaction between -OH and Ge(OH)4 on the adsorbent surface. This work indicated that TiO2-NH2-3OH had great advantages and potential for the recovery of Ge(IV) from coal acid leaching solution.

Selective removal of iron from sulfuric acid leaching solution of aerospace magnetic material scraps by jarosite process

Aerospace magnetic material scraps are abundant in cobalt and nickel. Sulfuric acid leaching process is an efficient method for extracting them. But it is a non-selective process, a significant amount of iron dissolves in the solution. This study focuses on the selective removal of iron from this solution using the jarosite process. Eh-pH diagram of K-S-Fe-H2O system was established. Based on thermodynamic analysis, H2O2 is used to oxidize Fe2+ into Fe3+, achieving efficient and selective removal of iron from the solution containing cobalt and nickel. The optimal conditions are as follows: temperature 95°C, K2SO4 dosage coefficient 1.5, seed dosage 10 g/L, time 90 min, pH 1.76, and endpoint pH controlled at approximately 3. Under these conditions, the iron removal efficiency is above 99%, while the loss ratios of cobalt and nickel are below 2%. The product is characterized by XRD and SEM-EDS. Results indicate that the product is jarosite ((K,H3O)Fe3(SO4)2(OH)6), exhibiting an ellipsoid structure with the mean particle size in the range of 0.2–5.0 μm. Temperature, pH value and seed dosage significantly affect reaction rate, particle size and crystallinity, and K2SO4 dosage mainly affects reaction rate and the morphology of jarosite. The jarosite crystallization kinetics can be described by the Avrami equation, with an Avrami index (n) of approximately 2.5 and the apparent activation energy of 42.68 kJ/mol.

Recovery of antimony from acidic and alkaline leaching solution of low-grade antimony ore by electrowinning process

With regards to the global continuous growth in consumption of base metals such as antimony (Sb), mining companies are currently looking to improve the productivity and extraction of Sb from low grade ore in order to economically process it. With this aim, in this study, an efficient protocol was developed to recover metallic Sb from the low grade Fe3Si2O5(OH)4. Sb3O6(OH). Sb2O3 ore of the Sefid-Abe mine in Zahedan province, Iran, utilizing selective acidic or alkaline leaching followed by Sb electrowinning. A process was developed to recover antimony from an Sb2O3 ore source, using selective acidic or alkaline leaching followed by antimony electrowinning. Sb could be leached with an efficiency of 85 % using 5 M NaOH and 87 % using 5 M hydrochloric acid/5 M sulfuric acid as the digestion solution at 80 °C for 8 h. The electrowinning process plays a significant role in recovery of highly pure Sb metal. Relying on this approach, a high deposition rate and current efficiency have been generated at a deposition potential 2 V at 30 °C (80 °C for alkaline medium). This was achieved by using anode electrode made of graphite and cathode electrode made of steel (two steel electrodes were used for alkaline electrowinning). Additionally, for acidic electrowinning, exploitation of Sb from the electrolyte solution was achieved by applying a current of 0.1 A, resulting in the highest yield equal to 89 %. On the other hand, for alkaline electrowinning, the highest efficiency corresponds to the current intensity of 0.5 A, which resulted in 97 % Sb extraction from the electrolyte solution. The XRD and ICP analysis performed for samples obtained from the electrolysis confirmed that the resulting antimony ingot has an exceptionally high purity.

Preparation of active zinc oxide from zinc-containing dust and synergistic recovery process of valuable elements

Zinc-containing dust generated from the iron and steel industry is enriched with a large amount of heavy metal substances and rare elements, which is a hazardous waste and a secondary resource. In this study, a new process for the preparation of active zinc oxide and synergistic recovery of valuable elements using zinc-containing dust was proposed. Firstly, a fire process was used to make the valuable components such as Zn, Cd, K, Na, Pb, Bi, In and Sn secondary enriched in the zinc-rich dust. Then the leaching and recovery of K (99.74 %) and Na (98.12 %) were realized by alkaline washing method taking advantage of the solubility difference. Thermodynamic analysis showed that controlling the pH of the leaching system could realize the selective separation of the valuable components. The experimental results showed that the leaching rates of Zn and Cd reached 86.95 % and 92.28 %, respectively, under the optimal experimental conditions, while Pb, Sn, Bi and In were enriched in the neutral leaching slag. Cd sponge (70.3 %) was obtained after the neutral leach solution was treated by Zn powder replacement process. The purified zinc sulfate solution was used to prepare active zinc oxide (97.04 %) by direct precipitation at a molar ratio of CO32–/Zn2+ of 1.15 and a temperature of 50 °C. The average particle size of the product was 21.95 nm, which was in accordance with the industry standard. Neutral leaching slag realized Bi (91.5 %), Sn (71.01 %) and In (94.0 %) in high acid leaching process, and Pb was enriched in slag in the form of PbSO4. The high acid leach solution is hydrolyzed, extracted and replaced to obtain BiOCl, crude tin and crude indium. This process realizes the comprehensive recovery and high-value utilization of various valuable elements in zinc-containing dust sludge, and has significant environmental, economic and social benefits.

Unveiling the Mechanism in Nickel Loss During the Neutralization of Pregnant Acid Leach Solution by Various Alkaline Chemicals Using Electron Imaging, X-Ray Diffraction, and Electron Energy Loss Spectroscopy Analyses

ABSTRACT Removal of iron and aluminum from nickel-bearing pregnant leach solution is imperative prior to recovering nickel. However, the mechanisms into the loss of both nickel and cobalt in precipitate products during the neutralization process remained unclear and debatable. In this study, the precipitation ratios of nickel, as well as other valuable metals in iron precipitate products, were investigated by examining bulk and surface properties of iron precipitates using X-ray diffraction, infrared spectroscopy, scanning electron microscopy, and electron energy loss spectroscopy. Amorphous ferrihydrite was identified as the major phase for iron precipitates. Over 99% precipitation ratio for iron and aluminum was achieved at pH 3. The loss of nickel in iron precipitates was strongly dependent on solution pHs, and the losses of nickel were found to be 3%, 8%, and 28% at pHs of 3, 4, and 5, respectively. The type of alkaline chemicals impacted the mineralogical composition of iron precipitate products and loss of valuable metals but had a minor impact on iron precipitation ratio. This work revealed three major mechanisms for the loss of nickel and cobalt during iron precipitation process: (1) entrainment of nickel-bearing PLS in filtered products, (2) surface adsorption on iron precipitates, and (3) lattice incorporation of nickel in iron precipitates. Additionally, the result of desorption experiments by H+ and Na+ ions showed that approximately 55–85% of lost nickel was incorporated within the lattice structure of iron precipitates, while the degree of nickel incorporation depends on the type of neutralizing reagents, precipitation conditions, and washing media.

Efficient recovery of all valuable metals from spent HDS catalysts: Based on roasting mechanisms for enhanced selective leaching and separation

Recovery of all valuable metals such as Ni, Mo, V and Al from spent hydrodesulfurization (HDS) catalysts is beneficial to environmental protection and resource recycling. The current recycling process mostly considers the recovery of Mo and V than recovery of Ni and Al, and generates a large amount of difficult-to-decompose Ni-Al residue and wastewater. Aiming at the insufficiency of the current recycling process, in this study, a novel pyro-hydrometallurgical process for efficient and complete recovery of metals from spent HDS catalysts was proposed. The mechanisms of phase transformation during roasting and leaching are investigated by XRD, XPS and SEM in depth. The modulation of the phase transformation of the spent HDS catalyst in the oxidative roasting process is the key to the influence on the leaching of Ni and Al. Inhibition of θ-Al2O3 phase and Ni-Al spinel generation by controlled roasting can achieve efficient leaching of Mo, V, Ni and Al. Subsequently, Mo and V were selectively leached with 2 mol/L Na2CO3, and the alkaline leach residue obtained was treated with 6 mol/L HCl. The results showed that alkaline leaching efficiencies of Mo and V reached 99.73 % and 91.86 % while acid leaching efficiencies of Ni and Al reached 99.71 % and 90.27 %, respectively. The metals of acid leach solution were recovered by using N235, HBL110 and NaAlO2 stepwise. This new process has the advantages of high efficiency and comprehensive metal recovery, high product purity, and low amount of slag and wastewater, and has good prospects for industrial application.

Molecular recognition on the surface of concentrated hydrochloric acid: Hydration configuration-driven preferential recognition of Rh (III) anions with inner-coordinated water molecules

Comprehension of selective recognition of anions is confined to a phenomenological list of solvents, hardly surpassing Pedersen’s empirical observations of cationic-crown ether binding. In this work, a novel strategy employing thin-layer oil membrane extraction (TOMX) on the surface of concentrated hydrochloric acid is proposed for controllable recognition and separation of anions with different hydration configurations. Four typical chloric-complexing anions, RhCl63−, PdCl42−, PtCl62− and FeCl4−, usually coexisting in the concentrated hydrochloric acid leaching solutions of precious metal concentrates were focused. A surprising phenomenon was noticed that the octahedral RhCl5(H2O)2− anions with inner-coordinated water molecules were preferentially recognized by 18C6 macrocyclic molecule. However, the planar quadrilateral Pd (II) chloric-complexing anions with a hydration configuration via water molecules attacking the central Pd (II) atoms along the Z-axis direction can be separated subsequently. The Pt (IV) and Fe (III) chloric-complexing anions respectively with an octahedral and tetrahedral outer-coordinated hydration shell configuration were the last to be recognized. Such an order in extracting Rh (III) > Pd (II) > Pt (IV) > Fe (III) anions depends on their hydration capacity and the preferential affinity towards the interface, which is almost impossible during the conventional stirring and oil droplet dispersed extraction. Because of a lower concentration of dissociated hydrogen ions on the surface of concentrated hydrochloric acid compared to its bulk concentrations, the hydration of those chloric-complexing anions was enhanced. The Rh (III) anions with inner-coordinated water molecules exhibit a higher interfacial affinity than other anions. The water molecules entering the inner coordination layer of Rh (III) chloric-complexing anions, cooperating with its outer-coordinated hydration shell, act as a hydrogen bond “water bridge” to interact with 18C6 molecules, which makes it easier to feel the influence from the aqueous laminar shear flow under the thin-layer oil membrane, thereby driving the preferential recognition of easily hydrated Rh (III) anions at the interface. The controllable “water bridge” interactions driven by shear flow can be activated or deactivated on the surface of concentrated hydrochloric acid by adjusting the shear flow rate. This work lays a foundation for the future development of a controllable flexible molecular recognition technology at liquid–liquid interfaces.

Selective separation of rhenium from oxygen-pressure leach solution of molybdenite concentrate using modified D201 resin: Experiments and theoretical calculations

Recovering rhenium from highly acidic rhenium-containing leach solutions is challenging for most resins, particularly in multiplexed systems. Herein, we introduce a scheme for selectively obtaining rhenium from a multielement solution containing high concentrations of sulfuric acid using modified D201 resin. Considering the dosage of resin and parameters such as pH and adsorption temperature, the adsorption efficiencies under optimal conditions for rhenium, molybdenum, iron, and cerium were 97.46 %, 0.38 %, 0.94 %, and 1.10 %, respectively. The selective recovery mechanism of rhenium was investigated by fitting the experimental data to kinetic and adsorption isotherm models. The pseudo-second-order and Langmuir models better fit results corresponding to the experimental data, which indicates monolayer chemisorption of ReO4− formed on the resin surface. Meanwhile, various characterizations such as SEM-EDS, FTIR, XPS, etc., indicate that ReO4− initially combines with the protonated −CHN+H2CH2Cl on the modified resin surface and then undergoes ion exchange reaction with doped Cl−. Furthermore, because of the diverse forms and similar properties of molybdenum and rhenium ions in acidic solutions, a theoretical model based on density functional theory was used to simulate the selective adsorption process in leach solution with a pH of 1.7. The simulation results demonstrate a highest occupied molecular orbital–lowest unoccupied molecular orbital energy gap, observed in the following order: ΔEMoO22+ = ΔEReO4− < ΔEMoO42− < ΔEMo7O246−, which implies that MoO22+ and ReO4− were most likely to transition from their ground states to excited states and react with the electron donor and acceptor groups, respectively. Compared with MoO42−, ReO4− is more likely to react with the electron acceptor group and provides the corresponding methods and a theoretical reference for selective separation of rhenium in multielement solutions.

Comprehensive recovery of arsenic and valuable metals from lead smelting flue dust: Process optimization and mechanism investigation

The comprehensive recovery of arsenic and valuable metals from lead smelting flue dust have received widespread attention due to its extremely high toxicity and economic value. In this research, a clean process which consisted of pressure oxidation leaching, preferential separation of Zn and Cd, reduction of As(Ⅴ) and recovery of indium was proposed. Thermodynamic calculation of leaching process suggested that the increasing of temperature reduces the redox potential required for the oxidation of As3+ to As5+, and the optimal conditions were found to be at acid concentration of 100 g/L, oxygen pressure of 2.0 MPa, temperature of 170 °C, L/S of 10 mL/g, leaching time of 2.5 h and agitating speed of 500 r/min. Under the selected conditions, the leaching extents of As, Cd, In, Sb and Zn are 99.17 %, 98.96 %, 92.68 %, 40.23 % and 96.63 %, respectively, while lead remained in the leaching residue. The separation of arsenic and other valuable metals in leachate is the most difficult and critical section of the process, where As2S3 was particularly added to the acid solution in certain manner to preferentially precipitate Zn and Cd in the forms of ZnS and CdS, subsequently reduce As(Ⅴ) to As(Ⅲ). Experiments by adding arsenic filter cake furtherly confirmed the reducibility of As2S3 and realized simultaneous extraction of arsenic in arsenic cake and acid leaching solution. Eventually, arsenic was recovered as As2O3 with a high purity of 98.56 % and the total extraction extent of indium is 93.76 %.

Simultaneous multi-coordination adsorption of V(IV) and V(V) in highly acidic solution using modified amino phosphate chelating resin

To avoid harmful neutralizing slag containing toxic metals during pH adjustment of acid leaching solution, we proposed an efficient extraction method of vanadium without adjusting the pH of the vanadium-containing acid leaching solution using modified amino phosphate chelating resin DS418. In this paper, the performance of the modified resin was further characterized, the adsorption kinetics, isothermal adsorption model of V(IV) and V(V) were compared and adsorption mechanism were analyzed on the atomic and molecular level. Under the condition of 25℃, the liquid-solid ratio was 1: 20 g/ml, nV(IV): nV(V)=1: 3, the V had the best adsorption effect of 92.65 %, and the cyclic stability of the DS418 resin was good. Through FTIR, XPS, TG-DSC as well as the DFT, it shows that V(IV) interacted with-PO3H2, while V(V) chelated with the-PO3H2 and -N, the most significant interaction was the distance between phosphate group and V with an average distance of 1.8018 Å for V(IV) and an average distance of 1.8376 Å for V(V). Based on the results, it shows the prospect of efficient recovery of multivalent vanadium ions in strongly acidic solutions and has environmental significance.

Sulfuric Acid Baking and Fe(III)-Cl--H2SO4 Leaching Behavior of Ni- and Cu-Containing Sulfide and Silicate Rich Suhanko Concentrate.

Ni- and Cu-rich concentrate from a new site in Suhanko, Finland, was investigated. Mineral phases identified included talc, chalcopyrite, kaolinite, and pyrrhotite with 3.2% Cu and 1.5% Ni, and the latter is associated with pyrrhotite. In addition, the concentrate contained the precious elements Pd (14.9 g/t), Ag (17.1 g/t), Pt (2.1 g/t), and Au (1.1 g/t). This concentrate was baked and leached using a Fe(III)-Cl--H2SO4 system. The results showed that the leaching efficiencies of Ni, Cu, and Si from raw concentrate were 60%, 40%, and 5%; however, those from baked concentrate were 96%, 60%, and below 0.1%, indicating that the baking process enhanced Ni and Cu extraction while simultaneously inhibiting the dissolution of Si, which was due to the baking process liberating the associated Ni and Cu by the oxidation of chalcopyrite and pyrrhotite and converting the acid-soluble silicate into an insoluble form. Sulfuric acid leaching solution with Fe(III) as oxidant and Cl- as lixiviant was shown to be effective at leaching Ni (97%), Cu (62%), and Ag (89%), while simultaneously enriching the PMs Pd, Pt, and Au in the residue.