Sulphate Leach Solutions Research Articles

Enhanced uranium removal from leach liquor using raw and activated sludge as sustainable adsorbents

ABSTRACT To eliminate uranium from sulphate leach solution, this study introduces an economical, environmentally friendly adsorbent derived from dewatered municipal sludge (RS) and activated (AS) using calcium oxide. Various analytical methods, including scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), Brunauer – Emmett – Teller (BET) analysis, and X-ray fluorescence spectroscopy (XRF), were employed in the characterisation of both materials. The efficacy of these adsorbents in removing uranium from sulphate leach fluid was systematically explored resulting in the achievement of a maximum adsorption capacity of 33.0 mg g−1 and 60.2 mg g−1 for RS and AS respectively. These adsorption capacity were detected using the following operational parameters: solution pH equals 2.0, 240 min as a contact time between the adsorbent and U(VI) solution, U(VI) initial concentration of 250 mg L−1, adsorbent dosage of 5.0 g L−1 and room temperature. The pseudo-second order kinetic and Langmuir isotherm models were determined to be the most suitable for the U(VI) adsorption process, showing a chemisorption, monolayer, and uniform process for the uranium adsorption by both materials. Using 1.0 M hydrochloric acid, over 96% of the U(VI) was successfully desorbed from the loaded sorbent, and AS sorbent held its stability for six sorption/desorption cycles in a row. Overall, this study offers a promising solution for sewage sludge disposal while addressing economic and environmental concerns.

Simultaneous extraction of molybdenum and silicon from sulphate leach solution of spent catalyst using trialkylamine (N235) and recovery of pure ammonium molybdate

Spent catalyst of molybdenum with silicon dioxide, commonly used as the carrier, is an important secondary resource for recovery of molybdenum. This work proposes a process to recycle molybdenum and remove silicon simultaneously by solvent extraction. The sulfuric acid leachate of the spent catalyst was contacted with the trialkylamine N235 (R3N, R = C8–C10), to extract molybdenum and silicon. Several vital parameters were investigated to explore the influence on extraction and stripping. The extraction efficiencies of molybdenum and silicon were up to 99.6% and 77.1% after three-stage countercurrent extraction under optimized condition. The extraction reactions were determined by maximum loading capacity and FT-IR. The peak at 802.1 cm−1 was caused by the stretching vibration of Si-O-Si, indicating the co-extraction of silicon. Molybdenum and silicon in the loaded organic phase can be stripped by the mixture of solution containing 7.00 mol/L NH4OH and 0.80 mol/L (NH4)2CO3, and the stripping efficiencies were >99.0%. Ammonium molybdate was prepared by removing silicon and evaporating, and the purity was 99.9%.

Removal of fluoride from the mixed Ni-Co-Mn sulfate leach solution of spent lithium ion batteries using polyaluminum sulfate

The mechanism and application of defluorination in a simulated leaching solution of spent lithium-ion batteries (LIBs) using poly‑aluminum sulfate (PAS) were studied. The experimental results indicated that reaction parameters such as the molar ratio of Al to F, pH of the solution, reaction temperature, initial concentration of fluorine, and concentration of lithium and nickel, significantly affected the reaction efficiency. Under the optimum reaction conditions, the percentage of defluorination was 95.5 (wt%). During the defluorination reaction, Al3+, Al(OH)3 reacted with F−, HF to generate AlF3 and AlF(OH)2. The crystallinity of AlF3, AlF(OH)2, and Al(OH)3 and the chemical stability of the precipitates improved with the increase in temperature and pH. The Li+ concentration in the solution increased the defluorination efficiency by forming LiAlF4. At the same time, high concentrations of NiSO4 inhibited the defluorination effect and were lost in association with the solids, NiSO4·6H2O and Ni(OH)2. According to the study of reaction kinetics, the rate equation of the aluminum‑fluorine reaction was -d[F]/dt = 0.0384exp(−8.59/RT) [F0]1.11[Al]0.31. The activation energy of the precipitation reaction was 8.59 kJ/mol, and the reaction rate was relatively high. In the actual defluorination process of the acid-leaching solution of waste battery powder with Ni-Mn-Co chemistry, the F− concentration reduced from 1205 mg/L to 48 mg/L and the loss of valuable metals was <6%, and the Ni, Co, and Mn in the precipitates were predominantly sulfates and hydroxides.

Extraction and separation of vanadium (IV) by EHEHPA with citric acid complexing iron (III) from sulfate leaching solution

The recovery of vanadium from sulfate leaching solutions is crucial for resource sustainability and environmental protection. However, the leaching solution contains impurities such as Fe (III), which have a significant impact on the separation and enrichment of V because a) the separation of Fe (III) and V (IV) through solvent extraction is problematic, and b) in the presence of oxygen from the air, it is challenging to fully reduce Fe (III) to Fe (II). Citric acid was used as a complexing agent in the aqueous phase to complex the Fe (III), and the effect of V (IV) extraction using 2-Ethylhexylphosphoric acid mono-2-ethylhexyl ester (EHEHPA) after Fe (III) complexation was investigated. To determine the complexation dose necessary for complete Fe (III) complexation, the numbers of ligands in the citric acid and Fe (III) complex were estimated, and the complexation mechanism of citric acid with Fe (III) was further clarified using UV–vis and FT-IR. According to the experimental findings, citric acid exhibits better complexing action than other complexing agents. Citric acid may complex > 96 % of Fe (III) in the liquid phase when the molar ratio of citric acid to Fe (III) is 1.5. When the pH of the solution was 1.2 and the molar ratio of citric acid to Fe (III) was 2, the extraction rates of V (IV) and Fe (III) obtained through EHEHPA were > 80 % and < 1 %, respectively. Additionally, the maximum separation factor βV/Fe was 430, which helped achieve the complete removal of Fe (III).

Application of surfactant for improving leaching process of weathered crust elution-deposited rare earth ores

Weathered crust elution-deposited rare earth ores (WREOs) in China are the main source of medium and heavy rare earths in the world. In order to improve the seepage and the mass transfer of traditional ammonium salt leaching process of WREOs, surfactants were added in the ammonium sulfate leaching solution and the ammonium chloride leaching solution. The leaching kinetics, the mass transfer process, and the adhesion work reduction factor calculated from the interfacial properties were studied to reveal the strengthening mechanism of surfactant. In the presence of the tested five surfactants, cetyl trimethyl ammonium bromide (CTAB), dodecyl trimethyl ammonium bromide (DTAB), sodium dodecyl sulfate (SDS), sodium oleate and oleic acid, the permeability of WREOs is improved, the rare earth (RE) leaching efficiency increase and the impurity aluminum (Al) leaching efficiency decrease, indicating its promotional effect on the leaching process of WREOs. Furthermore, CTAB shows a better leaching enhancement, and the optimal addition dosage is 0.4 g/L for the two ammonium salt leaching agent systems. The kinetics analysis shows the internal diffusion controls model of RE and Al leaching process, and the leaching kinetics equations of RE and Al related to CTAB concentration were obtained for the two ammonium salt leaching systems. According to the chromatographic plate theory, the mass transfer efficiency of RE increases with the CTAB concentration increasing until 0.4 g/L, which confirms that the optimal CTAB addition is 0.4 g/L. Smaller adhesion work and adhesion work reduction factor indicate more favorable permeation as well as the leaching process.

Deep fluoride removal from the sulfate leaching solution of spent LIBs by complexation extraction with Al3+ loaded solvent

Fluoride contained in the leaching solution of spent lithium-ion batteries (LIBs) not only decreased product quality, but also led to severe equipment corrosion and potential environmental hazards. Therefore, a coordination extraction system using di-(2-ethylhexyl) phosphoric acid (D2EHPA) loaded with aluminum ions (Al3+) as extractant was designed to deeply remove fluoride from the sulfate leaching solution of spent LIBs that combined the excellent binding affinity of Al3+ to fluoride and the perfect chemical efficiency of solvent extraction. The effects of D2EHPA concentration, loaded Al3+ concentration, equilibrium pH and shaking time on the extraction efficiency of fluoride were investigated. Experimental results indicated that over 99 % of fluoride was selectively extracted and the fluoride concentration in the leaching solution of spent LIBs was reduced from 210 mg/L to 2 mg/L by single-stage extraction, meeting the requirement of fluoride content in the battery grade Ni/Co/Mn sulfate solution and the wastewater discharge standards. The loaded organic phase was scrubbed and stripped by diluted H2SO4, and fluoride could be fully stripped into the stripping solution. Further characterization studies revealed that Al3+ and D2EHPA may mainly coordinate in the form of AlL3·HL in the Al-loaded organic phase (HL denotes D2EHPA). After the Al-loaded organic phase was contacted with solution containing fluoride, a structure of AlFL2·HL coordinated with F- was formed. This study provides a novel technical approach to improve product quality and reduce fluoride wastewater pollution for the recycling process of spent LIBs.

An Assessment of Parameters for Cementation of Impurities from Zinc Sulphate Leach Solution by a Statistical Design

An Assessment of Parameters for Cementation of Impurities from Zinc Sulphate Leach Solution by a Statistical Design

Recovery of metals from sulfate leach solutions of spent ternary lithium-ion batteries by precipitation with phosphate and solvent extraction with P507

Sulfate leach solutions ofspentternary lithium-ionbatteries (LIBs) contain transition metals (Mn, Co, and Ni) and Li in abundance. Selectively separating them from the sulfate leach solutions is necessary for their recovery. In this study, a novel approach was proposed for the selective separation and comprehensive recovery of these metals. The separation process was performed using stepwise phosphate precipitation and solvent extraction with P507. Firstly, 99.9% Al was selectively removed from the solutions through a phosphate precipitation process by adjusting the solution pH to 3.5 using NaHCO3 and adding 1.1 times the theoretical dosage of Na3PO4 at 80 °C for 30 min. The percentage precipitation of the other metals was 2.34%. Thereafter, the solutions could be directly used for the co-extraction of Mn, Co, and Ni by P507, leaving Li in the raffinate. A total of remaining Mn, Co, and Ni were co-extracted through five-stage counter-current extraction using an organic system consisting of 1 mol/L P507 (saponification degree of 60%) in sulfonated kerosene with an O/A ratio of 1.4:1. The co-extracted Mn, Co, and Ni in the loaded organic system were completely stripped through three-stage counter-current stripping using 1.5 mol/L H2SO4 with an O/A ratio of 5:1. By this process, the obtained solutions of Mn, Co, and Ni can be directly used to prepare ternary material precursors for recovery, while only 3.05% Li was lost. Finally, 98.9% Li left in the raffinate was easily recovered via Na3PO4 precipitation.

A Stepwise Solvent Extraction Process for Recovering Yttrium from Sulphate Leach Solutions of Deep-sea Mud

A novel approach for recovering yttrium from high ferric and strong acidic sulphate leach solutions of deep-sea mud by stepwise extraction and stripping has been developed. The results show that the first step extraction by N235+TBP system can extract H2SO4 well and adjust the raffinates to a desirable pH, while only the iron was selectively co-extracted with negligible loss of yttrium ions. The organic solution can be easily regenerated by using a 50 g/L H2SO4 solution to strip extracted iron followed by using deionized water to strip H2SO4. The raffinate could be directly used for the second step of yttrium extraction by P204+TBP system, while iron was co-extracted. The co-extracted yttrium and iron could be separated well through a sequentially stepwise stripping process using a 50 g/L H2SO4 solution and a 0.6 mol/L H2C2O4 solution. Over the whole process, yttrium was separated well from the sulphate leach solutions and enriched into the strip liquor of yttrium sulfate. The organic extractants could be returned for recycling.

Recovery of gallium from leach solutions of zinc refinery residues by stepwise solvent extraction with N235 and Cyanex 272

A novel approach was proposed for the extraction of gallium from high-ferric and strongly acidic sulfate leach solutions from zinc refinery residue. The stepwise separation was carried out using N235 and Cyanex 272 in the first and second steps, respectively. The results showed that N235 could selectively remove iron and H2SO4 and provide suitable conditions for the subsequent extraction by Cyanex 272. The co-extracted zinc, gallium, and iron were separated by stepwise stripping. In batch tests, 97.9% of iron was selectively extracted from solutions through three-stage cross-current extraction by using an organic system consisting of 30% (v/v) N235 and 10% (v/v) tributyl phosphate in sulfonated kerosene with an aqueous/organic (A/O) ratio of 1:1, while the percentage extractions of other metals were <3% (the separation factors of βFe/Ga, βFe/Zn, βFe/Cu, and βFe/Cd, were determined to be 4.1×103, 1.7×103, 1.8×103, and 2.3×103, respectively). In the loaded organic system, 99.7% of iron was stripped using 0.5 mol/L H2SO4 followed by treatment with a sodium carbonate solution for regeneration. The raffinate with pH = 2.67 could be directly used for the extraction by Cyanex 272. A total of >99.9% gallium, >99.9% remaining iron, and 49.7% zinc were co-extracted through four-stage counter-current extraction by using an organic system consisting of 30% (v/v) Cyanex 272 in sulfonated kerosene with an A/O ratio of 1:1, while the percentage extractions of other metals (copper and cadmium) were negligible (the separation factors of βGa/Zn, βGa/Fe, βGa/Cu, and βGa/Cd, were determined to be 6.1×103, 2.7×10-1, 3.3×106, and ∞, respectively). Furthermore, >99.9% zinc, 99.7% gallium, and 98.9% iron in the loaded organic system were efficiently separated through a stepwise stripping process by using 6 mol/L HCl, 0.5 mol/L H2SO4, and 0.6 mol/L H2C2O4 (the separation factors of βZn/Ga, βZn/Fe, and βGa/Fe, were determined to be 1.1×106, 4.4×104, and 6.4×104, respectively). Overall, 99.7% of gallium was separated and extracted into the strip liquor, resulting in a concentration of 1502 mg/L.

Removal of arsenic from “Dirty acid” wastewater via Waelz slag and the recovery of valuable metals

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 Cu3As and Cu2O, which could be used to remove Co from the zinc sulfate (ZnSO4) 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.

Adsorption of U(VI) from sulfate solution using montmorillonite/polyamide and nano-titanium oxide/polyamide nanocomposites

The polyamide-based nanocomposites were formed via inorganic nanosized (montmorillonite clay MMT, or TiO2) particles that incorporated inside a polyamide 6 (PA6) matrix. Moreover, the MMT/PA6 and TiO2/PA6 nanocomposites were prepared by simple dissolution methods. Morphology of the gained nanocomposites was studied by SEM, EDX, TEM, FTIR, and XRD techniques. Batch adsorption was fulfilled to determine the uptake capacities of U(VI) (93.0, 21.0, 134.0, and 125.0 mg/g) on the MMT, PA6, and MMT/PA6 and TiO2/PA6 nanocomposites, respectively from sulfate solution in the pH 4.5, 30 min contact time at room temperature. The adsorption-desorption recycling was indicated that U(VI) adsorption has excellent stability and selectivity after seven cycles by 0.25 M HNO3 eluant. The kinetic data of uranium adsorption on MMT, PA6, and MMT/PA6 and TiO2/PA6 nanocomposites were suited well to a pseudo-second-order mechanism, and the Langmuir isotherm followed the equilibrium adsorption experiments. The tentative mechanism of the adsorption of U(VI) on adsorbents was proposed. Finally, the optimum adsorption conditions for MMT/PA6, and TiO2/PA6 nanocomposites were applied for U(VI) recovery from the El-Sela sulfate leach solution.

Behavior of rare earth, iron, and phosphorus during purification of rare earth sulfate leach solution using magnesium oxide

The largest rare earth (RE) reserves minerals of China is the bastnaesite (RE[CO3]F) and monazite ((RE, Th)[PO4]) mixed type RE ore in Bayan Obo, and 90% of this concentrate is processed by the sulfuric acid roasting method. However, during purification of RE sulfate leach solution with solid MgO, the RE loss is noticeable and accompanied by a mass of acid and alkali consumption and discharge of radioactive solid waste, which also causes environmental pollution. In this paper, the behavior of RE, Fe, and P during purification were investigated focusing on the effect of pH, concentration ratio of iron and phosphorus, RE concentration, and step-wise purification (based on different pH). The characterization of precipitated impurities by BET specific surface area, XRD, SEM and FTIR reveal the reaction sequence of RE loss and the formation of the precipitate. Two new factors, neglected previously, were found to be the main contributors to the production of large solid-waste:(1) sulfate which exists in the form of Fe(OH)x(SO4)(3-x)/2 accounts for 9 to 12% of the total weight of the precipitate; (2) higher solid content in the purification slurry at a relatively high pH range (pH = 2.5–4.5) significantly promotes the production of precipitate and higher loss of RE during purification. This paper proposes a two-step purification method (based on different middle pH point), step (i): a low pH purification stage in which most P, Fe(III) and H+ were removed with minimum loss of RE followed by filtration; step (ii), high pH purification stage in which the rest of Fe(III) was completely removed with less than 2% RE lost caused by low solid-to-liquid ratio consuming less MgO. Through two-step purification under the most suitable conditions, the RE recovery increased by 6% while MgO consumption and solid residue production decreased by 12% and 16%, respectively. It can greatly alleviate the environmental problems with just a minimal modification of the operation conditions and equipment in the proposed process.

Solvent Extraction of Copper and Zinc from Sulfate Leach Solution Derived from a Porcelain Stone Tailings Sample with Chemorex CP-150 and D2EHPA

This research investigates the extraction behavior of copper and zinc from the sulfate leachate of a porcelain stone tailings sample with Chemorex CP-150 and D2EHPA in detail. The findings demonstrated that Chemorex had greater ability and selectivity in the extraction of copper, while D2EHPA was better in the extraction of zinc. 97.88% copper and 78.2% zinc were extracted, respectively, with Chemorex and D2EHPA within 10 min contact time at an 1:1 aqueous/organic ratio, 10% (v/v) extractant concentration, and ambient temperature. The appropriate solution pH levels for Chemorex and D2EHPA were found to be 2.5 and 2, respectively. Also, a McCabe–Thiele diagram was drawn and one single-step extraction for copper and a two-stage process for zinc were needed to achieve the highest extraction efficiency. Additionally, the mechanism study indicated the association of ~ 1.5 and 1 mol of Chemorex CP-150 and D2EHPA for the extraction of one mole of Cu and Zn from the leach solution. Moreover, thermodynamic parameters, including ΔH, ΔG and ΔS were found to be 65.29 kJ/mol, 9.83 kJ/mol, and 186.14 J/mol K for copper and − 18.71 kJ/mol, 17.80 kJ/mol, and − 122.53 J/mol K for zinc, respectively, indicating that the extraction process was endothermic for copper and exothermic for zinc. The effect of contact time, pH, and extractants concentration on the extraction efficiency of Cu and Zn by Chemorex CP-150 and D2EHPA and also the number moles required for extractants

Intermobility of barium, strontium, and lead in chloride and sulfate leach solutions

Production of radionuclide-free copper concentrates is dependent on understanding and controlling the deportment of daughter radionuclides (RNs) produced from 238U decay, specifically 226Ra, 210Pb, and 210Po. Sulfuric acid leaching is currently employed in the Olympic Dam processing plant (South Australia) to remove U and fluorine from copper concentrates prior to smelting but does not adequately remove the aforementioned RN. Due to chemical similarities between lead and alkaline earth metals (including Ra), two sets of experiments were designed to understand solution interactions between Sr, Ba, and Pb at various conditions. Nanoscale secondary ion mass spectrometry (NanoSIMS) isotopic spatial distribution maps and laser ablation inductively coupled-plasma mass spectrometry transects were performed on laboratory-grown crystals of baryte, celestite, and anglesite which had been exposed to different solutions under different pH and reaction time conditions. Analysis of experimental products reveals three uptake mechanisms: overgrowth of nearly pure SrSO4 and PbSO4 on baryte; incorporation of minor of Pb and Ba into celestite due to diffusion; and extensive replacement of Pb by Sr (and less extensive replacement of Pb by Ba) in anglesite via coupled dissolution-reprecipitation reactions. The presence of H2SO4 either enhanced or inhibited these reactions. Kinetic modelling supports the experimental results, showing potential for extrapolating the (Sr, Ba, Pb)SO4 system to encompass RaSO4. Direct observation of grain-scale element distributions by nanoSIMS aids understanding of the controlling conditions and mechanisms of replacement that may be critical steps for Pb and Ra removal from concentrates by allowing construction of a cationic replacement scenario targeting Pb or Ra, or ideally all insoluble sulfates. Experimental results provide a foundation for further investigation of RN uptake during minerals processing, especially during acid leaching. The new evidence enhances understanding of micro- to nanoscale chemical interactions and not only aids determination of where radionuclides reside during each processing stage but also guides development of flowsheets targeting their removal.

Enrichment of rare earths in magnesium sulfate leach solutions of ion-absorbed ores by extraction-precipitation

Magnesium sulfate (MgSO4), a leaching agent for ion-absorption rare earth (RE) ores, can reduce the production of ammonia nitrogen wastewater and supply magnesium (Mg) for soil. Three novel solid extractants, i.e., 2,2′-(1,4-phenylenebis(oxy))dioctanoic acid (PPBOA), 2,2′-(1,2-phenylenebis(oxy))dioctanoic acid (OPBOA) and 2,2′-(1,3-phenylenebis(oxy))dioctanoic acid (MPBOA) were synthesized and used to enrich RE by extraction-precipitation strategy, which showed better selectivity and faster equilibrium. The precipitation rates of PPBOA, OPBOA and MPBOA on RE could reach 95.1%, 93.5% and 96.7% at the large liquid/solid phase ratio (450/1). Meanwhile, the purities of RE in the stripping solutions reached 96.1 wt%, 94.1 wt% and 96.2 wt%. Chemical oxygen demand (COD) values of raffinates from OPBOA and MPBOA were 56 mg/L and 69 mg/L, being lower than that of China national emission standard (100 mg/L). The concentration of enriched RE solution by MPBOA was 238.0 g/L, solid extractant and MgSO4 raffinate could be recycled.

Recovery of Copper and Nickel from Polymetallic Sulphate Leach Solution of Printed Circuit Boards using Dowex M 4195

Recovery of Copper and Nickel from Polymetallic Sulphate Leach Solution of Printed Circuit Boards using Dowex M 4195

HYDROMETALLURGICAL PROCESSING OF NICKEL LATERITES- A BRIEF OVERVIEW ON THE USE OF SOLVENT EXTRACTION AND NICKEL/COBALT PROJECT FOR THE SEPARATION AND PURIFICATION OF NICKEL AND COBALT

In this study, a brief overview of the solvent extraction (SX) application for the separationand purification of nickel and cobalt in hydrometallurgical processing of laterite nickel ores ispresented. This paper consists of two parts: firstly, the SX of nickel and cobalt from sulphateleach solutions is described; and secondly, the development of hydrometallurgical plants forthe processing of laterite nickel ores that involve solvent extraction technique is discussed. Themost important extractants are shortly given in the first part of the study. It is seen that theextraction and separation of nickel and cobalt from the impure leach solution of laterite nickelores can be performed by either using a single extractant system that is called as a direct solventextraction (DSX) or a mixture of two or more extractant which is known as a synergistic solventextraction system (SSX). Mixed sulphide precipitation (MSP) and mixed hydroxide precipitation(MHP) processes are mentioned. This paper is also addressed advantage and disadvantages ofeach extraction system. It is shown that capital investment expenditure, operational investmentexpenditure and mineralogical content are the most important factors that can affect the selectionof the appropriate hydrometallurgical process for lateritic nickel ore.

Recovery of gallium from strong acidic sulphate leach solutions of zinc refinery residues using a novel phosphate ester extractant

A novel phosphate ester extractant (H2R) was used to extract gallium directly from strong acidic sulphate leach solutions of zinc refinery residues. The results indicated that the application acidity of H2R significantly exceeded those of P507 and P204 (two commonly used phosphate esters), and could directly extract gallium from the solutions with relatively high acidity (20–120 g/L H2SO4). In batch tests, 98.54% of gallium was extracted from solutions containing 0.205 g/L gallium and 107.80 g/L H2SO4 in four-stage counter current extraction, by using an organic system consisting of 40% (v/v) H2R in sulfonated kerosene with an A/O ratio of 1:1 at laboratory temperature (27 ± 1 °C) for 10 min. Meanwhile, extractions of other metals (germanium, zinc, copper, arsenic, and cadmium) were negligible, except for that of iron. After scrubbing using 20 g/L H2SO4 at an A/O ratio of 1:1, 99.13% of gallium in the loaded organic was selectively stripped using 200 g/L H2SO4 solution via five-stage counter current stripping with an A/O ratio of 1:4 at 27 ± 1 °C for 10 min, followed by using 7 mol/L HCl solution to strip co-extracted iron for recycling. Over the whole process, 96.71% of gallium was recovered and enriched in the pure gallium sulphate strip liquor with a concentration of 0.793 g/L. The results of continuous running tests demonstrated that H2R could be used to selectively recover gallium from strong acidic sulphate leach solutions of zinc refinery residues, with high stability and good cycling performance.

Uranium recovery from high-chloride sulphate leach solutions: A cost tradeoff study of using treated water vs. saline water as make-up water

Uranium recovery from high-chloride sulphate leach solutions: A cost tradeoff study of using treated water vs. saline water as make-up water