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Abstract: Diffusion dialysis with a series of anion exchange membranes was used to recover H2SO4 from an acid leach solution produced during the vanadium manufacturing process. The effects of sulfuric acid, FeSO4 and VOSO4 concentration, flow rate and flow rate ratio on the recovery of H2SO4 were investigated. The results showed that sulfuric acid permeated well through the membranes used, while metal ions were efficiently rejected. The recovery of H2SO4 increased as the sulfate concentration of the feed increased and the flow rate ratio of water to feed increased. More than 80% of the H2SO4 could be recovered from the leach solution which contained 61.7g/L free H2SO4, 11.2g/L Fe and 4.60g/L V at a flow rate of 0.19×10−3 m3/hm2. V and Fe ion rejection were within 93–95 and 92–94%, respectively. A preliminary economic evaluation revealed that an investment in this process could be recovered within 27 months. [Copyright &y& Elsevier]

The controlled synthesis of recyclable hematite in the leaching solution of secondary zinc oxide powder is an urgent problem in the chemical industry and metallurgy fields. In this paper, the effects of the temperature, agitation speed, and seed addition on the contents of iron, sulfur, potassium, sodium, and zinc in the iron removal residues, as well as the iron concentration in the supernatant after iron removal were systematically studied. In addition to the temperature control already reported, we found that the agitation speed can also control the transformation between jarosite and hematite phases. The content of jarosite in the residues can be effectively controlled by adjusting the agitation speed, thereby significantly improving the quality of hematite product, as indicated by SEM-EDS and XRD results. Under temperature of 185 °C, an agitation speed of 500 rpm, and a seed addition of 15 g/L, the iron, sulfur and zinc contents in the filter residues and the iron concentration in the supernatant were 59%, 3.22%, 0.92%, and 4.182 g/L, respectively. Kinetic studies show that the rapid oxidation kinetics is not conducive to the formation of high-quality hematite products. These results can directly guide the process of transformation of harmful jarosite into recyclable hematite from the leaching solution of secondary zinc oxide powder, which is of great practical significance for the controlled and waste-free removal of iron from aqueous solutions in the chemical industry and metallurgy fields. [ABSTRACT FROM AUTHOR]

• Scale-forming ions removal and CO 2 fixation by CO 2 purification and PAM flocculation. • Calcite CaCO 3 was obtained during the "CO 2 -NaOH" method brine purification process. • The residual of PAM flocculants less than 0.2 mg/L in the refined brine. • PAM flocculation applied to industrial test and realization deep brine purification. The "CO 2 –NaOH" brine purification method and flocculation performance of polyacrylamide (PAM) flocculants in vacuum salt making brine purification process are reported in this paper. The scale-forming trends of the brine were assessed by the Langlier index (LSI), the Ryznar stability index (RSI) and the Larson-Skold index (LR). The thermodynamic calculation results and PAM flocculant coagulation mechanism show that removal of Ca2+ and Mg2+ ions and suspended solids (SS) from brine by the "CO 2 –NaOH" method and PAM flocculants is feasible. The total concentration of Ca2+ and Mg2+ ions was decreased from 486.1 mg/L to 3.41 mg/L, and SS was decreased from 20 mg/L to 5 mg/L at the optimal experimental condition of CO 2 flow velocity of 0.04 m3/h, injection time of 30 min, equilibrium pH of 11.5, and the dosage of the FL2949 and AN945SH PAM flocculants of 1 mg/L. LSI, RSI and LR show that the scale-forming was slowed down by brine purification. PAM flocculants were not retained in the brine as confirmed by the analysis of total organic carbon and chemical oxygen demand, and the X-ray diffraction, Fourier transform infrared, and scanning electron microscopy electron dispersive spectroscopy measurements for the flocs sludge during the brine purification process, results shown that the flocs sludge is calcite CaCO 3. PAM flocculants purification was applied in industrial testing and achieved deep brine purification to remove scale-forming ions and SS. Additionally, it was found that the "CO 2 –NaOH" brine purification method promotes the utilization of CO 2. [ABSTRACT FROM AUTHOR]

• The dissolution behavior of industrial hematite in H 2 SO 4 solution was studied for the first time. • The shrinking core model with inert reactant layer was employed to describe the dissolution process of industrial hematite. • This research is helpful to the development of low-temperature and short-duration hematite process. Here, the effect of H 2 SO 4 concentration, temperature, liquid to solid ratio and particle size on the dissolution behavior of industrial hematite in H 2 SO 4 solution. Among them, temperature and H 2 SO 4 concentration have significant effects on the dissolution efficiency of Fe from industrial hematite. Below 363.15 K, the dissolution efficiency of Fe increases with the increase of temperature, but the opposite is true above 363.15 K. Increase H 2 SO 4 concentration to promote the dissolution of industrial hematite. Liquid-solid ratio and particle size had little effect on the Fe concentration after dissolving at 180 min, but it has a significant influence on the Fe dissolution efficiency. The Fe dissolution efficiency of hematite with large particle size is significantly higher than that with small. Shrinking core model with inert reactant layer was employed to describe the dissolving kinetics of industrial hematite in H 2 SO 4 solution. In the temperature range of 303.15 − 343.15 K, the interfacial chemical reaction control is the rate-limiting step. Apparent activation energy (E a) is 48.1 kJ·mol−1. Based on this, four methods were recommended to prevent the re-dissolution of hematite in industrial practice: (1) increasing the reaction temperature, (2) extending the residence time of hematite in high temperature autoclave, (3) reducing the acidity of the slurry in autoclave though add neutralizer, (4) separating immediately hematite from slurry discharged from the autoclave. This work is of great practical value in terms of iron removal and recycle from the ZnSO 4 solution though the hematite process with efficient, clean and low temperature at 423.15 K. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Iron in the leaching solution with high K+ and Na+ concentrations was usually precipitated as the typical hazardous and toxic jarosite residues. However, this method of treatment has been greatly restricted by increasingly strict environmental regulations. Here we propose that iron can be precipitated from the solution with high K+ and Na+ concentrations as recyclable hematite products by adjusting the concentration ratio of sodium and potassium ions in the solution. The transformation behavior of jarosite into hematite in high concentration potassium ion and sodium ion solution was explained based on collision theory. The results indicated that in instances where the concentration ratio of Na+/K+ is ≥ 4:1, the iron present in the solution can be effectively precipitated as a recyclable hematite product, as opposed to forming the conventional hazardous jarosite residue, even under conditions where the potassium ion concentration reaches levels as high as 4 g/L. On the other hand, thermodynamic and molecular dynamics simulations indicate that at a temperature of 185 °C, the decomposition transformation of Na-jarosite (32.64 kJ and 7.25 eV) is more energetically advantageous compared to that of K-jarosite (61.07 kJ and 15.31 eV). The results were verified by the leaching solution from smelting industry. The iron content in the residues is above 58%, the sulfur content is below 4%, the zinc content is below 1%, and the total iron concentration in the supernatant is about 4 g/L, reaching the production index of the smelting industry. The green, environmentally friendly, and recyclable separation of iron in a solution with high concentrations of potassium and sodium ions is achieved, which is of great significance for the treatment of iron-containing solution and wastewater in the chemical industry and metallurgy fields. [ABSTRACT FROM AUTHOR]

• High iron recovery efficiency. • Low recovery cost. • The performance of regenerated LFP battery is better. The recovery of valuable metals from used lithium batteries is essential from an environmental and resource management standpoint. However, the most widely used acid leaching method causes significant ecological harm. Here, we proposed a method of recovering Li and Fe selectively from used lithium iron phosphate batteries by using low-concentration organic acid and completing the closed-loop regeneration. Low-concentration oxalic acid is used to carry out PO 4 3− , which is significantly less soluble in aqueous solution than Li, two-stage selective leaching Li, where the leaching rate of Li reaches 99 %, and the leaching rate of Fe is only 2.4 %. The leach solution is then decontaminated. The solubility of Li 3 PO 4 in aqueous solution is much smaller than that of Li 2 C 2 O 4 , which was required to recover Li to change the pH and Li can be recovered as Li 3 PO 4 ; Fe can be retrieved as FeC 2 O 4 ·2H 2 O, and re-prepared into lithium iron phosphate. [ABSTRACT FROM AUTHOR]

Recovering germanium from zinc oxide dust (ZOD) produced from Pb–Zn smelter is an important pathway to extract germanium. However, the leaching efficiency of industrial germanium production is not satisfactory (usually less than 75 %). Therefore, the leaching behavior of Ge in different phases was discovered in this work. Ge in the ZOD mainly occurs in oxide, sulfide, silicate, and solid insoluble. The potential decides the oxidative dissolution of sulfide. The leaching recovery of zinc and germanium were 90 % and 80 % with oxidant, and 78 % and 80 % without oxidant, respectively. The effect sequence of oxidant type on the Zn leaching efficiency was MnO2 > H2O2 ≈ oxygen > air, but the type and addition of oxidant had no obvious effect on the leaching recovery of germanium. The final pH of leaching slurry limits the dissolution of oxide and hydrolysis-polymerization of impurity ions (such as Fe(III) and Si). Decreasing the final pH is beneficial to the leaching reaction of Zn and Ge. The germanium presented in oxide and sulfide is easy to leach, while the leaching of germanium existed in silicate and solid insoluble is relatively difficult. The structure of aluminate can be destroyed effectively using a 40 g/L HF solution. When the leaching percent of SiO2 is 86.82 %, the leaching recovery of Ge is 96.57 %. For the ZOD with higher content of Fe and Si, germanium leaching is negatively correlated with the content of Fe and Si in the ZOD. The results provide a scientific basis for improving the leaching recovery of germanium. [ABSTRACT FROM AUTHOR]

• The feasibility of salt gypsum residue utilization and CO 2 mineralization were verified by thermodynamic calculation. • Efficient converting salt gypsum to portlandite was realized by NaOH leaching without ammonia/ ammonium reagent. • Different CaCO 3 crystal forms were prepared via regulating the CO 2 partial pressure. • Salt gypsum residue is a kind of raw material for preparing CaCO 3 and CO 2 mineralization. Salt gypsum residue, an industrial solid waste, is the by-product of vacuum evaporation in the salt-making industry. This study aimed to recover salt gypsum and prepare CaCO 3 via NaOH leaching and pressure strengthening with CO 2 ; meanwhile, CO 2 mineralization was realized. The method can not only produce CaCO 3 with controllable morphology, but also efficient realize CO 2 solidification using metal cations in the salt gypsum residue and utilization of the industrial solid waste, so as to zero discharge of waste residue in the salt-making industry. The thermodynamic calculation results showed that the method is feasible. The experimental results showed that the phase transformation efficiency of salt gypsum residue was 99.94 % under the optimal experimental conditions at NaOH concentration of 3 mol/L, liquid–solid ratio of 8 mL/g, time of 10 min, temperature of 50 ℃, stirring at 300 rpm, and CO 2 flow rate of 1.0 L/min. The diffusion of CO 2 is the rate-limiting step of carbonation; it was disrupted by CO 2 pressure strengthening, and the conversion efficiency of salt gypsum improved. Moreover, the migration of CaCO 3 molecules to the crystal kink, nucleation, and growth rate of CaCO 3 crystals were improved via increasing CO 2 partial pressure, affecting the morphology of CaCO 3 crystals. Therefore, Calcite and aragonite CaCO 3 crystals were obtained when the CO 2 pressure was 0.0 MPa and 0.2 MPa, respectively. Moreover, the CO 2 mineralization efficiency and CaCO 3 yield were 635.3 kg CO 2 /1000 kg salt gypsum residue and 975.0 kg CaCO 3 /1000 kg salt gypsum residue under optimal experimental conditions. These new observations are expected to provide further understanding and guidance for the clean utilization of salt gypsum residue and CO 2 mineralization in the salt-making industry. [ABSTRACT FROM AUTHOR]

• A LTMNL method for selective extraction of germanium from IBLR was introduced. • The decomposition mechanism of x (SiO 2)·GeO 2 and y (Fe 3 O 4)·GeO 2 was studied. • A germanium leaching yield of above 98% was obtained. • LTMNL residue can be considered as an iron resource. To address the insolubility of x (SiO 2)·GeO 2 and y (Fe 3 O 4)·GeO 2 , this study introduced a two-step leaching (NaOH leaching-NL and low-temperature molten NaOH leaching- LTMNL) method. During the NL process, 51.30 % of germanium (Ge), 84.96 % of aluminum (Al), and 56.45 % of silicon (Si) were leached. Moreover, in the LTMNL process, over 97.43 % of Ge and nearly all amphoteric metals (e.g., Al, Zn, and As) were dissolved under optimized conditions (including a NaNO 3 -to-ore mass ratio of 0.15, leaching temperature of 170 °C, alkali-to-ore mass ratio of 10, agitation speed of 500 rpm, and reaction time of 2 h). The leachate obtained from the LTMNL process was used as a lixiviant in the NL process to facilitate the recyclable utilization of NaOH and enrich Ge in the leachate solution. This approach resulted in an overall germanium recovery efficiency of 98.72 %. The germanium concentration in the NL leachate exceeded 400 mg/L, thereby facilitating subsequent germanium recovery. Additionally, the LTMNL residue, containing an iron concentration of 52.46 wt%, served as an iron resource. Therefore, the two-step leaching process achieved high germanium recovery and efficient separation of Ge and Fe compared with conventional H 2 SO 4 leaching methods. This indicates that the two-step leaching process is a promising and efficient method for treating germanium-bearing material in the form of x (SiO 2)·GeO 2 and y (Fe 3 O 4)·GeO 2). [ABSTRACT FROM AUTHOR]

• Recovery of zinc from BFD using zinc-chloride coordination leaching methodology. • Zinc-chloride cooperation leaching process was analyzed by thermodynamic calculation. • 93.2% of zinc was extracted by HCl-NaCl-H 2 O leaching system from BFD. • Leaching residue of BFD are recycled to iron-making process. Blast furnace dust (BFD) contains ferrous and nonferrous metals and carbon, and is usually categorized as a typical secondary resource and hazardous waste produced by the iron-making process. The thermodynamic calculation and experimental investigation of the selective separation of zinc and iron/carbon from BFD via a NaCl-HCl-H 2 O system were carried out. Quantitative zinc and iron/carbon separation and recovery was achieved via a zinc-chloride (ZnCl i 2-i (i = 0, 1, 2, 3, 4)) cooperative leaching methodology using 3 mol/L NaCl at pH of 4, an L/S ratio of 4:1, a leaching temperature of 70 °C, a HCl concentration of 0.25 mol/L, and a leaching time of 2 h. Moreover, the total Cl– concentration used in for leaching was 2.09 mol (as concluded by the dosages of HCl and NaCl, and material). Results demonstrate that zinc was effectively leached from BFD, while the leaching of iron was hindered, in the acidic region. 93.2% of the zinc was extracted into a leaching solution containing 19.8 g/L zinc under the optimal conditions, and the ratio of the leaching agent to BFD was 300 mL to 75 g. The XRD and SEM-EDS analysis results of the residue reveal that ZnO and ZnS were leached, and the zinc-iron spinel (ZnFe 2 O 4) was not leached and was present together with the iron oxide in the leaching residue. Iron and carbon in the leaching residue was enriched from 49.4% to 60.38%, and the iron and carbon were recovered as secondary resources that can be reused in the iron-making system. [ABSTRACT FROM AUTHOR]

• No impurities are introduced in GBIC low-temperature roasting process. • In-situ water in GBIC can react with willemite to form hemimorphite. • The formation of hemimorphite promotes the leaching efficiency of zinc. • The efficient selective separation of Zn and Ge is achieved in the AAC system. • AAC filtrate can be reused, and leaching residue is employed to extract Ge. Germanium-bearing iron cake (GBIC) produced through the germanium removal process in a zinc smelter is a valuable source of zinc and germanium. However, achieving selective separation of zinc and germanium using pyrometallurgy treatment and sulfuric acid leaching methods is challenging. To address these challenges, this study introduced a novel roasting–leaching process. During roasting, willemite transformed into ammonia-soluble hemimorphite, promoting zinc leaching. This transformation was mainly attributed to the reaction between in situ water in GBIC and willemite within 200–500 °C. Optimal roasting conditions included a particle size range of 49–74 µm, a roasting temperature of 490 °C, and a duration of 4 h. Under optimized leaching conditions—[NH 4 ++NH 3 ] (7 mol/L), NH 4 +/NH 3 molar ratio (2.5), temperature (50 °C), liquid-to-solid ratio (20 mL/g), agitation speed (600 rpm), and time (180 min)—zinc and germanium exhibited leaching yields of 84.92 % and 0.59 %, respectively, in an ammonia–ammonium carbonate system. After three cycles of leaching, the Zn concentration in leachate increased to 20 g/L, facilitating the subsequent recovery of zinc. Moreover, the Ge concentration in the germanium-bearing leaching residue increased by 1.5 times compared with the initial GBIC, making the residue a valuable source of germanium. [ABSTRACT FROM AUTHOR]

In this study, the enhanced extraction of zinc from a blast furnace dust (BFD) ammonia leaching solution via carbon dioxide (CO 2) was investigated. 1-Benzoyl-2-nonyl ketone (commercially known as Mextral54–100) and tri-alkyl phosphine oxide (TRPO) were used as the extractant and synergistic extractant, respectively. The effects of different operational factors, such as the CO 2 pressure, extractant concentration, phase ratio, and extraction temperature, were examined to optimize selective and quantitative zinc extraction. The loaded organic phase was stripped using sulfuric acid and waste electrolyte. Quantitative zinc extraction was achieved in two stages using 1.2 mol/L Mextral54–100 and 0.2 mol/L TRPO at an initial pH of 8.0, CO 2 at 0.2 MPa, and an aqueous:organic (A:O) ratio of 2:1. The loaded organic phase, which contained 0.08 mol/L zinc, could be stripped in a single stage using 1.6 mol/L H 2 SO 4 at a phase flow ratio of A/O = 1:1 to create a loaded strip solution that contained 5.5 g/L zinc. Zinc extraction from BFD with the ammonia leaching solution was enhanced by CO 2 addition. Fourier-transform infrared spectroscopy confirmed that CO 2 could prevent the co-extraction of ammonia into the synergistic system of the Mextral54–100/TRPO mixture. Based on the experimental results, a flowsheet for the recovery of zinc from BFD was developed and tested. The extents of zinc leaching, extraction, and stripping were ~ 91%, 97%, and 99%, respectively. • Extraction of Zn from BFD ammonia leaching solution using CO 2 was developed and Zn extraction was enhanced by CO 2 addition. • A flowsheet for the recovery of Zn from blast furnace dust ammonia leaching solution was tested. • 91% of Zn was leached from BFD by ammonia solution and 97% of Zn were extracted from leaching solution. [ABSTRACT FROM AUTHOR]

• Extraction of In from from hydrochloric acid solution and the indium on the loaded organic phase was stripped by water was developed. • N503, P350 and TBP were used as the extractants for In, respectively. • The extracted complexes with N503 and P350 were determined to be [InCl 4 −[2S·H]+; the complex formed with TBP was [InCl 4 −[3S·H]+, where S represents the neutral extractant species. • It was found that 99% of In were extracted and 100% of the indium on the loaded organic phase was stripped by water. • Indium can be extracted from hydrochloric acid and enriched in a low-acidity strip solution. Solvent extraction of indium from hydrochloric acid solution using N,N-di(1-methyl-eptyl) acetamide (N503), di(l-methylheptyl)methyl phosphate (P350), and tributyl phosphate (TBP) diluted in sulfonated kerosene was investigated. Extraction was studied as a function of hydrochloric acid and chloride ion concentrations, organic-phase composition, initial indium concentration, phase contact time, and aqueous/organic (A/O) volumetric ratio. The extraction stoichiometry was determined by slope analysis and confirmed by Fourier-transform infrared spectroscopy. It was found that indium extraction efficiency decreased in the order: N503 > P350 > TBP. The extracted complexes with N503 and P350 were determined to be [InCl 4 −[2S·H]+; the complex formed with TBP was [InCl 4 −[3S·H]+, where S represents the neutral extractant species. N503 was found to be best extractant of the three with respect to extracting indium from solutions containing a high concentration of hydrochloric acid. Almost quantitative (99%) indium extraction was obtained using 0.5 mol·L−1 N503 in three extraction stages at an A/O ratio of 2/1; 100% of the indium on the loaded organic phase was stripped by water in two stages at an A/O ratio of 1/3. Indium can therefore be extracted from hydrochloric acid and enriched in a low-acidity strip solution. [ABSTRACT FROM AUTHOR]

• A method for BFD recovery by coordination leaching of Cl− and hydrolysis of NH 4 +. • The NH 4 Cl coordination leaching process was analyzed by thermodynamic calculation. • The low-temperature crystallization was adopted to recover zinc from filtrate. • The separation and recovery of zinc from BFD was achieved. Blast furnace dust (BFD) is a by-product of iron-making process, a typical hazardous waste containing abundant recyclable components. In this study, a NH 4 Cl cooperative coordination leaching method was proposed for the selective separation and recovery of zinc from BFD. The thermodynamic analysis results revealed that ZnO and ZnSO 4 from BFD can be converted to zinc-chlorine coordination compounds (ZnCl i 2−i, i = 1,2,3,4) in the cooperative actions of NH 4 + and Cl− ions. The experimental results showed that the leaching efficiency of zinc reached 85.64% while iron and carbon was enriched from 46.76% to 57.96% under the optimal experimental conditions. The leaching residue with a total content 2.53% of Zn, Cl, K and Na can be returned to sintering for the recovery of iron and carbon. Moreover, the XRD, SEM-EDS and chemical phase analysis results of BFD and residue demonstrated that a small amount ZnO, ZnS and ZnFe 2 O 4 were not leached and remained in the leaching residue. Additionally, a novel method of low-temperature crystallization was adopted to recover zinc from filtrate. The crystallization efficiency of zinc reached 80.96% and the obtained crystal was confirmed to be special Zn(NH 3) 2 Cl 2. Thus, this work not only achieved the separation and recovery of zinc from BFD, but also solved the disposal problem of leaching residue and crystallization solution, providing a guidance for the resource utilization of hazardous BFD. [ABSTRACT FROM AUTHOR]

• Germanium was extracted with a new orgnic phase YW100 + D2EHPA + N235. • Compared to the "YW100 + D2EHPA" traditional extraction system, 80% of the water solubility loss of YW100 was reduced and improved the phase separation performance. • The phase separation performance was improved. • The mechanism of germanium extraction and phase separation has been studied. In this study, germanium was selectively extracted using an organic phase containing 3% C7-9 hydroxamic acid (YW100), 15% Di(2-ethylhexyl)phosphoric acid (D2EHPA), 35% Tri(octyl-decyl) amine (N235), and 47% kerosene from the Ge-slag sulfuric acid leaching solution. Then, the solution was stripped by the 1 mol/L NH4F solution to obtain a germanium extraction ratio of 99.4% and a stripping ratio of 96.2% after three extraction and stripping stages. The total organic carbon (TOC) was used to characterize the total organic matter amount in the raffinate. Compared to the "YW100 + D2EHPA" extraction system, the "YW100 + D2EHPA + N235" extraction system reduced 80% of the water solubility loss of YW100 and improved the phase separation performance. In addition, the mechanisms of germanium extraction and phase separation improvement were studied. The coordination number of YW100 and germanium is 3, while the coordination number of D2EHPA is 1. [ABSTRACT FROM AUTHOR]

Existing methods are difficult to directly treat the tailings of Lanping Pb-Zn deposit because of low Pb + Zn content. According to the characteristics of high CaO content (11%) in the flotation products of Lanping low-grade Pb-Zn oxide ore, a carbon thermal reduction method based on rotary hearth furnace (RHF) process was developed. When reaction temperature was above 1000 °C, CaO could realize the transformation of metal sulfides to oxides. Increasing reducing atmosphere was favor of the efficient volatilization of Zn and Pb and the trapping of S. The volatiles in reducing agents could promote the volatilization of zinc. The reduction effect of anthracite and thermal coal was better than that of charcoal. The volatilization rates of Zn and Pb exceeded 98% and 96%, respectively, under the conditions of 1250 °C, 30 min, 20% thermal coal addition and air atmosphere. High quality ZnO dust with a ZnO purity of 83% was obtained. [Display omitted] • Refractory lead‑zinc oxide ore (O-S mixed ore) were treated based on RHF process. • Efficient separation of Zn and Pb from gangue components was realized. • High sulfur fixation efficiency reduced the emission of SO 2 in the environment. • High-quality dust with a ZnO purity of >89% was obtained. [ABSTRACT FROM AUTHOR]

• The separation and recovery of indium and germanium in the coexistence solution of indium and germanium were studied, rather than the recovery of a single element. • The element flow and mechanism of the whole process is clearly explained. • The recovery efficiency of indium and germanium both reached>99%. • A flowsheet can be applied to selectively recover germanium and indium from the investigated solution. Selective extraction of indium and germanium from natural resources due to their important role in high-tech fields is attracting more and more attention. In this paper, indium and germanium were recovered from In-Ge residue leaching solution by the selective solvent extraction of indium with D2EHPA and the precipitation of germanium using tannin. This process included two main stages: indium-selective solvent extraction and germanium-selective precipitation. In the first stage, indium was extracted by using an organic phase containing 15% D2EHPA and 85% kerosene. The indium-loaded organic phase was washed with 0.5 M H 2 SO 4 and then stripped by 4 M HCl solution to obtain an indium extraction ratio of 99% and a stripping ratio of 98.3%. In the second stage, the pH of the raffinate was adjusted to 3.5–4.0 with ZnO dust and then mixed with tannin. Germanium (99%) was selectively precipitated as a tannin-germanium complex. The washed tannin-germanium complex was baked at 500 °C for 3 h to produce a germanium concentrate. By studying the separation coefficients of indium, germanium, and zinc (1994 and 1093, respectively), and controlling the reaction conditions, the maximum separation of indium, germanium, and zinc was obtained. The extraction mechanism of indium from sulfuric acid solution by D2EHPA and element migration during the precipitation of germanium using tannin were also studied. This proposed process flow can be used to selectively recover germanium and indium from In-Ge residue leaching solutions. [ABSTRACT FROM AUTHOR]

Hematite produced by the zinc industry exhibits a high sulfur content, being mainly contaminated by jarosite as the main sulfur-containing phase, and is thus of limited use for the steelmaking industry. Herein, we investigate the effects of parameters such as temperature (170–200 °C) and initial concentrations of sulfuric acid (0–19.6 g/L), sodium sulfate (0–35.5 g/L), hematite seeds (0–30 g/L), and Zn 2+ (80–120 g/L) on the formation and conversion of jarosite during hematite precipitation from a ferrous sulfate solution, obtaining high-quality hematite with a low sulfur content. We reveal that increased temperature not only benefits jarosite conversion but also reduces the sulfur content of precipitates and enriches them in iron. Sulfuric acid concentrations of 4.9–19.6 g/L greatly decrease the fraction of precipitated iron and produce sulfur-rich precipitates containing significant amounts of both hematite and jarosite, whereas sodium sulfate increases the iron removal efficiency and the sodium content in hematite precipitates. Hematite seeds prompt the precipitation of hematite and affect the composition of the obtained precipitates, promoting the precipitation of hematite in preference to jarosite at relatively low temperatures. Finally, zinc sulfate concentrations of 80–120 g/L have a positive effect on iron removal as hematite. [ABSTRACT FROM AUTHOR]

The use of Waelz slag produced during zinc (Zn) hydrometallurgical processes to treat "dirty acid" wastewater was investigated in this study. As(III) in the wastewater was oxidized by performing a pre-oxidation process, after which oxidation leaching, Fe-As co-precipitation, Cu-As cementation, neutralization-hydrolysis, and hematite precipitation processes were performed. The initial As concentration was 8.56 g/L, and the treatment processes decreased the concentration to 0.5 mg/L, which meets the integrated wastewater discharge standard stipulated by the Ministry of Ecology and Environment, P.R China. Most of the As was removed during the Fe-As co-precipitation process as crystalline scorodite at atmospheric pressure, and most of the copper in the Waelz slag was removed during the Cu-As cementation process as Cu 3 As and Cu 2 O, which could be used to remove Co from the zinc sulfate (ZnSO 4) leaching solution used during Zn hydrometallurgical processes. Fe was precipitated as hematite, which could be used as a raw material to make iron at high temperatures and pressures. The proposed treatment process can effectively remove As from "dirty acid: wastewater and allow the recycling of valuable metals in Waelz slag. The treatment process is therefore efficient and inexpensive, and offers promise for industrial use. • An efficient removal and separation method of arsenic from dirty acid wastewater by Waelz slag was developed. • Arsenic concentration in dirty acid wastewater would be reduced to 0.5 mg/L by this method. • The iron in Waelz slag can replace FeSO 4 to remove arsenic by precipitating as crystalline scorodite. • The iron and copper in Waelz slag would be recovered as hematite and Cu-As residue, respectively. [ABSTRACT FROM AUTHOR]