Four-stage Countercurrent Extraction Research Articles

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.

Sustainable separation of molybdenum from mixed mineral acids generated as semiconductor industry waste streams using tributyl phosphate (TBP) by effects of hybrid machine learning models

This study explores the separation and optimization of molybdenum (Mo) from mixed mineral acids derived from semiconductor industry waste streams with tributyl phosphate (TBP) by implementing machine learning (ML) models. Considerable experimental tests were performed to evaluate the impact of various operational variables on the effectiveness of Mo extraction and stripping. The support vector regression (SVR) paired with harmony search algorithm (HSA), genetic algorithm (GA), and shuffled frog leaping algorithm (SFLA) were employed for enhancement in the separation process and structural optimization. The SVR-SFLA model yielded the most meticulous predictions, identifying optimal extraction conditions with a TBP concentration, mixing time, temperature, and O/A ratio of 50%, 30 min, 25 °C, and 1, respectively, achieving 77.8% efficiency. The derived results from the SVR-SFLA model, in tandem with the McCabe-Theil diagram, indicated a four-stage counter-current extraction process required to achieve a yield exceeding 99%. For the stripping process, the hybrid model indicated optimal conditions with 3 M NH4OH and an A/O ratio of 0.5 at 50 °C for 20 min, requiring two counter-current stages for nearly complete stripping. Feature importance analysis using a random forest algorithm (RFA) highlighted the NH4OH concentration and phase ratio as the most significant factors, contributing 40.3% and 29.1%, respectively, to the stripping from the loaded TBP phase. The final product, obtained after crystallization and thermal decomposition of the strip solutions, was characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS), revealing 99.74% purity for molybdenum trioxide.

Recovery of lithium from the desorption solutions of salt lakes using β-diketone synergistic extraction system

Lithium has become increasingly important because of its irreplaceable role in lithium-ion batteries. Addressing the complex process and high energy consumption of the current adsorption-membrane integrated process for lithium extraction from high Mg/Li ratio salt lake brine, this study put forward an integrated process of adsorption-solvent extraction. Taking the desorption solution of adsorption method as raw material, the process parameters and extraction mechanism of lithium by the novel extraction system were investigated. A novel process of lithium recovery from the desorption solutions of salt lakes by solvent extraction was proposed for the first time. The composition of the extraction system was studied and determined to be HTTA-P113-kerosene. Compared with the previously reported neutral ligands (TOPO, Cyanex923), P113 not only exhibited excellent synergistic extraction ability but also had good miscibility and a green synthesis process. The effects of saponification degree, extraction time, temperature and phase ratio on lithium extraction and βLi/Na were systematically investigated. Through the four-stage countercurrent extraction, more than 99.2 % of lithium could be extracted by the organic phase consisting of 0.4 mol L−1 HTTA, 0.4 mol L−1 P113, saponification degree of 80 % at O/A ratio of 1:1 and equilibrium pH of 6.78. Furthermore, after the scrubbing and stripping process, the lithium-rich solution containing 21.64 g L−1 Li+ and 0.037 g L−1 Na+ was obtained. The Li2CO3 products with a purity of 99.5 % were successfully prepared from the lithium-rich solution by precipitation method. Finally, the extraction mechanism was studied via the slope analysis method and FT-IR spectra. It was indicated that the extracted lithium species were Li(TTA)(P113).

Selective separation of lithium from the hydrochloric acid leachate of lithium ores via the extraction system containing TBP-FeCl3

The elevation of comprehensive lithium recovery remains a formidable challenge in lithium extraction from lithium bearing ores due to the equilibrium solubility constraints affecting the lithium precipitation reaction. Hence, this work drew inspirations from lithium extraction techniques in salt lakes by characterizing the hydrochloric acid leachate of lithium ores as a distinct brine. The leachate composition was regulated and solvent extraction technology for selective lithium extraction was developed. By employing the loaded organic phase with Fe3+ (2TBP-NaFeCl4) to extract the leachate, and utilizing a four-stage countercurrent extraction process, the extraction efficiency of lithium could be achieved at 99 % at least. Following three-stage scrubbing and two-stage countercurrent stripping experiments, the stabilized stripping efficiency of lithium was 99.24 %. The concentration of Li+ in the stripping solution was enriched up to 16.404 g/L, while the total concentration of impurity ions was only 0.424 g/L. The resulting lithium-enriched solution could be utilized to prepare high-purity lithium chloride. This process has achieved a highly selective and efficient extraction of lithium, thereby enhancing the overall lithium extraction efficiency. The Density Functional Theory results indicate that the loaded organic phase selectively extracted lithium through ion exchange.

ЭКСТРАКЦИОННОЕ ДЕАЗОТИРОВАНИЕ И ОБЕССЕРИВАНИЕ СМЕСИ ГАЗОЙЛЕЙ ВИСБРЕКИНГА И КАТАЛИТИЧЕСКОГО КРЕКИНГА N-МЕТИЛПИРРОЛИДОНОМ

There are presented the results of a single-stage extraction of a mixture of visbreaking and catalytic cracking gas oils in a mass ratio of 70 : 30 N-methylpyrrolidone with 2 % of water by weight and extractant-to-raw material ratios of 0.5 : 1, 1 : 1 and 1.5 : 1, as well as two-stage cross-current extraction and four-stage countercurrent extraction with a mass ratio of the extractant to a mixture of gas oils 1 : 1. With four-stage extraction, the sulfur content is reduced 7.5 times to 0.269 % by weight in refined products, which is significantly lower than the permissible level in marine fuel for open water areas

Clean and cost-efficient preparation of vanadium electrolyte from the vanadium-rich solution of black shale by solvent extraction

This study proposes a clean and cost-efficient preparation process for vanadium electrolytes from the vanadium-rich solution of black shale. The introduction of saponified D2EHPA promoted vanadium recovery and further separation of impurities from vanadium-rich solutions. The preparation of a high-purity vanadium electrolyte was achieved by a four-stage countercurrent extraction at an initial pH as low as 1.0, 8 min, D2EHPA concentration of 30%, saponification degree of 60%, and phase ratio of 1:1, as well as a three-stage countercurrent stripping with 4 mol L−1 H2SO4 at phase ratio (O/A) of 6:1, 30 min. The developed electrolyte showed qualified electrochemical and charge-discharge performance, with coulombic efficiency, voltage efficiency, and energy efficiency reaching 91.07%, 93.44%, and 85.10%, respectively. This method saves 30.28% in preparation costs over the traditional method and produces no ammonia, nitrogen, or harmful gases. The technology is technologically advanced, economically sensible, and ecologically friendly, and is expected to be applied to large-scale production and promote the development of VRFB and new energy.

Preferential extraction of rubidium from high concentration impurity solution by solvent extraction and preparation of high-purity rubidium salts

Rubidium has a wide range of application prospects in high-tech fields, which makes the extraction of rubidium resources of great significance. However, the similar properties among alkali metals render their separation from each other a considerable challenge. This study aims to recover rubidium from high concentration impurity solution via solvent extraction, and further purify and refine rubidium salt products. The organic phase consisted of the acidic extractant [4-tert-butyl-2-(α-methylbenzyl) phenol (t-BAMBP)] and xylene. The affecting parameters, such as contact time, extractant concentration, alkalinity, and phase ratio (O/A) were thoroughly investigated during the separation process. Rubidium could be completely extracted after the four-stage countercurrent extraction, accompanied by 18.84 % of K+ also entered the organic phase. Furthermore, deionized water was employed to remove impurity elements, such as contaminant potassium in the loaded organic phase. The scrubbing findings revealed that the scrubbing rate of K+ reached 99.03 % after five-stage countercurrent scrubbing at a phase ratio of 5:1. Most importantly, rubidium chloride solution was obtained after HCl stripping, which was further used to prepare high-purity rubidium chloride and rubidium carbonate products with a purity of 99.5 %. Eventually, this work provides a complete process for rubidium extraction and product preparation.

Recovery of vanadium from direct acid leaching solutions of weathered crust vanadium‐titanium magnetite via solvent extraction with N235

In this study, we developed a new method for the efficient extraction and separation of V from direct acid leaching solutions of weathered crust VTi magnetite using N235/TBP, sodium sulfate (Na2SO4), and sodium carbonate (Na2CO3) as the extraction system and washing and stripping agents, respectively. The effects of various experimental conditions on the extraction results were investigated, and the extraction efficiency of V was approximately 70% with <4% Fe co-extraction under optimal conditions. A four-stage countercurrent extraction method was used to extract >96% of V and <4.5% of Fe, and the separation factor of V/Fe was 541. Upon washing the V-loaded organic phase with a 0.70 mol/L Na2SO4 solution, >96% of Fe and ~1% of V were removed. Moreover, upon stripping the purified organic phase with a 0.70 mol/L Na2CO3 solution, >98% of V was recovered. The effects of other impurities on the separation of V were negligible. Moreover, the stripped organic phase can be recycled sustainably during extraction. In this study, we selectively separated V and provided a new method for accelerating the purification and enrichment of V, which is present at low concentrations in acid leaching solutions.

ОДНОСТУПЕНЧАТАЯ И МНОГОСТУПЕНЧАТАЯ ЭКСТРАКЦИОННАЯ ОЧИСТКА ЛЁГКОГО ГАЗОЙЛЯ УСТАНОВКИ ЗАМЕДЛЕННОГО КОКСОВАНИЯ ПАО «ГАЗПРОМНЕФТЬ – ОМСКИЙ НПЗ» N,N – ДИМЕТИЛФОРМАМИДОМ

The results of single–stage extraction of light gas oil of delayed coking of Omsk refinery with N,N - dimethylformamide at the mass ratio of extractant to raw materials are presented 0.3:1, 0.4:1, 0.5:1, as well as four-stage countercurrent extraction and cross-current at a mass ratio of N,N - dimethylformamide to raw materials 0.4:1 and a temperature of 40 oC. With four-stage countercurrent extraction, raffinate was obtained with a yield of 75.1% by weight, in which, compared with raw materials, the sulfur content was reduced from 0.733 to 0.452% by weight, nitrogen - from 1912 to 305 ppm, the amount of polycycloarenes - from 18.7 to 11% by weight, the cetane index increased from 41.6 to 53.5 points. Raffinate meets the requirements for marine fuels for ships sailing in open waters

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.

Study on Extraction Separation of Thioarsenite Acid in Alkaline Solution by -Type Tri-n-Octylmethyl-Ammonium Chloride.

To overcome the problem of arsenic separation and enrichment from an alkaline leaching solution in arsenic-containing dust, a -type tri-n-octylmethyl-ammonium chloride (TOMAC) method for extracting thioarsenite is proposed in this paper. Considering an alkaline leaching solution as the research object, after vulcanization pretreatment, TOMAC transformation and organic phase saturated extraction capacity were measured, and the extraction mechanism was preliminarily studied. First, Cl−-type quaternary ammonium salt was effectively transformed to -type by treating organic phase with saturated NaHCO3five times. TOMAC was effectively transformed from to type by alkaline washing with 1.0 mol/l NaOH solution; this washing was repeated thrice. Thereafter, the effects of organic phase composition, phase ratio, extraction time, and temperature on the extraction and separation of arsenic were investigated. The results show that under the conditions of 30% -type TOMAC + 15% sec-octanol + 55% sulfonated kerosene, VO/VA = 1/1, and 5 min extraction at room temperature, the single-stage extraction rate of AsIII is 85.2%. The AsIII concentration in raffinate can be reduced to less than 1.33 × 10−3 mol/l by four-stage countercurrent extraction, and the extraction rate of AsIII can exceed 98.4%.

Separation and recovery of cesium sulfate from the leach solution obtained in the sulfuric acid baking process of lepidolite concentrate

Lepidolite is an important mineral resource of lithium, rubidium and cesium. Lithium, rubidium and cesium were extracted simultaneously from a lepidolite concentrate by sulfuric acid baking and water leaching. A crystallization-roasting-dissolution-solvent extraction process was developed to recover cesium from the leach solution in this study. During crystallization, leach solution was cooled from 85 °C to 35 °C firstly to precipitate most parts of Rb+ with 98.65% and Cs+ with 94.59% in the form of RbAl(SO4)2·xH2O and RbAl(SO4)2·xH2O, respectively. The mixed alums were then roasted at 900 °C to decompose them into Cs2SO4, Rb2SO4, K2SO4 and Al2O3. Next, a mixed sulfates solution with 12.51 g/L Rb+ and 2.4 g/L Cs+ was obtained by water dissolution of the roasted alums. Cesium was then separated from the solution by solvent extraction, scrubbing and stripping. A Cs-loaded organic phase with 4.66 g/L Cs+ and 3.05 g/L Rb+ was obtained after a four-stage countercurrent extraction. Around 99.20% of Cs+ and 10.44% of Rb+ were extracted by using 4-tert-butyl-2-(α-methylbenzyl) phenol (t-BAMBP). After scrubbing and stripping of the Cs-loaded organic phase by diluted H2SO4, a cesium sulfate solution of 16.6 g/L Cs+ was obtained. A cesium sulfate product with a purity of 98.47 wt% was then recovered by evaporation and crystallization of the stripping solution

Solvent extraction of rubidium from a sulfate solution with high concentrations of rubidium and potassium using 4-tert-butyl-2-(α-methylbenzyl)-phenol

Rubidium is a critical mineral due to its important role in the rubidium atomic clock in global positioning systems. In our previous study, lithium, rubidium, cesium were extracted simultaneously from lepidolite by a sulfuric acid baking process; a sulfate solution with 10.26 g/L-Rb+ and 40.74 g/L-K+ was obtained after recovery of lithium and cesium. As the continuity of this research, solvent extraction was used to separate rubidium from the above solution with high concentrations of Rb+ and K+ in this study. An organic phase with 1 mol/L 4-tert-butyl-2-(α-methylbenzyl)-phenol was introduced to extract the rubidium. The Rb+ extraction efficiency reached 97.02%, with 17.28% K+ co-extracted after a four-stage countercurrent extraction. The rubidium-loaded organic phase was then scrubbed with water, and the scrubbing efficiency of the potassium was 96.17%, with 7.25% of rubidium lost. After potassium scrubbing, a potassium-depleted organic phase with 3.2 g/L-Rb+ and 0.093 g/L-K+ was obtained. Almost all the rubidium could be stripped from the organic phase using 0.1 mol/L sulfuric acid. A rubidium sulfate product with a purity of 98.17 wt.% was obtained by evaporation and crystallization of the stripping solution. Finally, an integrated process for recovery of lithium, cesium, and rubidium from lepidolite was proposed.

Simultaneous extraction of Ti(IV) and Fe(III) in HCl solution containing multiple metals and the mechanism research

A new process for simultaneous extraction of Ti(IV) and Fe(III) in HCl solution containing multiple metals was proposed, and the extraction mechanism was studied. The screened synergistic extractant had higher selectivity for Ti(IV) and Fe(III) than that of other metal ions. With four-stage countercurrent extraction in 1.5:1 phase ratio, the extraction efficiencies of Ti(IV) and Fe(III) were 99.76% and 99.99%, respectively. The extraction rates of co-extracted Ca, Al, V, Mg, Mn and Cr were 0, 0, 0, 0.32%, 1.44% and 31.49%, respectively. According to FT-IR spectra, speciation analysis and slope method, the mechanism of Ti(IV) extraction could be ionic association, the form extracted could be TiOCl32[ROHH2]¯. The mechanism of Fe(III) extraction was not only ion association, but also solvation, the forms extracted could be FeCl43C18H37NO3H3¯, FeCl4ROH3.33H¯ and FeCl3ROH3.33¯. Thermodynamic studies had also been conducted. The dilute HCl and deionized water were used as stripping agents, respectively. The Ti(IV) and Fe(III) stripping efficiencies were 99.88% and 99.90%, respectively. The purities of Ti(IV) solution and Fe(III) solution were 98.75 wt% and 99.18 wt%, respectively. The regenerated extractant would not lose activity. The proposed method may promote the industrialization of TiO2 produced by the HCl process.

Separation of H3PO4 from HCl-wet-processing phosphate rocks leach liquor by TBP: Extraction equilibria and mechanism study

Tri-n-butyl phosphate (TBP) with various combinations of extractants was used to extract H3PO4 from a phosphate leach liquor. The results showed that 80 vol% TBP diluted in kerosene was suitable for extraction yielding. The effects of operational parameters and composition on the extraction behavior were investigated by an orthogonal experiment (L16(45)) and relevant analysis. Aiming to yield the concentrated acid extract, the theoretical stages and minimum dosage of extractant was simulated by plotting McCabe-Thiele diagram. A four-stage countercurrent extraction was carried out through a series of cascade experiments, indicating that over 83% H3PO4 and 10% CaCl2 in the actual iron-removed acid were extracted into organic phase. Furthermore, the extraction mechanism between H3PO4 and TBP at the presence of CaCl2 has been discussed. The assumption that the H3PO4 is extracted by TBP as a neutral extraction complex in a form of pH3PO4·qTBP was characterized by FTIR, 1H NMR and 31P NMR analysis. The extraction equilibrium of H3PO4 in the H3PO4-CaCl2-H2O-TBP system showed an extraction of 0.66 mol and 0.74 mol H3PO4 against each mole of TBP could be loaded from the synthetic acid containing 1.0 mol/L and 2.5 mol/L CaCl2, respectively. The results are contributive to design a new and efficient extraction process to separate H3PO4 from the phosphate leach liquor of HCl route.

Recovery of neodymium, dysprosium, and cobalt from NdFeB magnet leachate using an unsymmetrical dialkylphosphinic acid extractant, INET-3

Rare earths (REs) and Co are critical strategic resources. Their recovery is crucial for ensuring that their supplies are adequate and for reducing environmental pollution. End-of-life NdFeB magnets are important secondary RE sources. The separation of Dy, Nd, and Co from NdFeB leachate using a relatively new extractant (2,3-dimethylbutyl) (2,4,4′-trimethylpentyl)phosphinic acid (INET-3), was investigated in this study. The separation parameters, such as equilibrium pH, phase ratio, INET-3 concentration, and number of counter-current extraction stages, were optimised. The results show that INET-3 can separate Dy, Nd, and Co efficiently. For the preferential extraction of Dy from synthetic iron-free NdFeB leachate, the optimum equilibrium pH is 2.60. Under this condition, separation of Dy from the leachate requires four counter-current extraction stages at A/O (volume ratio of aqueous to organic) = 1:2. This is demonstrated by a simulated four-stage counter-current extraction process. At equilibrium pH = 2.52 and A/O = 1:2, 98% of Dy is recovered with 95% purity. As to the subsequent separation of Nd from the leachate, nearly 100% is recovered with 99% purity through a simulated three-stage counter-current extraction process at equilibrium pH = 5.33 and A/O = 1:1. Approximately 95% of Co remains in the raffinate with 99.98% purity.

Selective recovery of Rhenium from industrial leach solutions by synergistic solvent extraction

In our previous work, the selective precipitation of rhenium from an acidic washing solution present in the copper smelting process was studied. The precipitate formed is a polymetallic sulfide that contains rhenium, copper, arsenic, and bismuth. To recover rhenium from the precipitate, the separation of perrhenate ions from industrial leach solutions using synergistic solvent extraction was investigated. For the synergistic extraction system of Alamine 336 and TBP, Alamine 336 is the primary compound that combines with the anions in the leach solution. The solubility of the extraction complex in the organic phase is enhanced by TBP bonding with the neutral complex. For the extraction of perrhenate ion from the chloridizing leach solution, the difference in the distribution coefficient of rhenium and bismuth is small due to the formation of bismuth polychloride complex ion in aqueous solution. For the acidic leach solution using sulfuric acid and ammonia persulfate, the separation percentage of perrhenate ion is more than 99.90 wt% using four-stage countercurrent extraction. This is because the bismuth and arsenic in the leach solution forms an insoluble compound (BiO)2SO4 and arsenic acid. The loaded organic phase is stripped by a 4 mol/L ammonium solution, recovering 98.78% Re. The content of arsenic, copper, bismuth, and lead in the ammonia perrhenate formed from the evaporation and crystallization process using the stripping liquor is less than 0.5 mg/kg and 1.0 mg/kg, respectively.

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.

A novel process on separation of manganese from calcium and magnesium using synergistic solvent extraction system

The synergistic solvent extraction (SSX) system consisting of di-2-ethylhexyl phosphoric acid (P204) and alkyl-4-pyridinecarboxylate ester (4PC) in sulfonated kerosene was used to separate manganese from magnesium and calcium and to prepare pure manganese sulfate solutions with battery grade. In batch tests, over 99.9% of Mn2+ was extracted after a four-stage counter current extraction using an organic solution consisting of 0.25 mol/L P204 and 0.5 mol/L 4PC in sulfonated kerosene and a feed containing 22 g/L Mn2+, 4 g/L Mg2+ and 0.1 g/L Ca2+ with an A/O ratio of 1:6 at 25 °C for 10 min, while extractions of magnesium and calcium were negligible. After scrubbing using 0.025 mol/L H2SO4 at an A/O ratio of 1:8, the loaded organic solution was stripped using 0.7 mol/L H2SO4 at an A/O ratio of 1:8 to prepare pure manganese sulfate solutions with battery grade. The results of continuous operation test indicated that the mass ratios of Ca/Mn and Mg/Mn in strip liquors were below 5.6 × 10−5 and 2.5 × 10−4, respectively, further demonstrating the efficient separation of manganese from magnesium and calcium using the SSX system.

A new recyclable sulfurizing reagent for Mo-S complexes and separation of molybdenum from tungstate solutions

Separation of tungsten and molybdenum has been a key technology in tungsten metallurgy. In this study, a new sulfurizing reagent of thiocyanuric acid (TTCA) was employed to sulfurized trace amount of molybdenum in ammonium tungstate solution. The effects of initial feed pH, reaction temperature and molar ratio of Mo/TTCA on complexing of Mo and S were investigated. The Mo-S complex was also characterized. The organic phase consisting of 50% (v/v) N1923 in kerosene was used to selectively extract molybdenum from a synthetic tungstate solution containing 100 g/L WO3 and 1 g/L Mo. The extraction of molybdenum reached 99.5% after a four-stage counter current extraction, leaving only 5 mg/L Mo in raffinates with a mass ratio of Mo/WO3 less than 3.3 × 10−6. More than 95% of molybdenum can be stripped from loaded organic phases using 2 mol/L NaOH solution in a single stage. The sulfurizing reagent can be recovered for sustainable reuse. Compared to conventional inorganic sulfurizing reagents, the use of organic reagent TTCA avoided the generation of toxic H2S gas.