Zinc Refinery Residues Research Articles

Microanalytical investigations of gallium occurrence and distribution in zinc refinery residue

Microanalytical investigations of gallium occurrence and distribution in zinc refinery residue

Dissolution behavior and improvement approach for gallium extraction from zinc refinery residues

Aiming at solving low Ga leaching efficiency during actual industrial production in Danxia Smelter, chemical composition, phases and morphologies of various zinc refinery residues were characterized using ICP−AES, XRD and SEM−EDS. Compared with the normal material, Ga was embedded in the jarosite phase from the special zinc refinery residue, causing difficulty in Ga leaching. During the oxidation pressure leaching, the dissolution behaviors of Ga, As and Fe presented similar variation tendency. Namely, a sufficient H2SO4 concentration and liquid-to-solid ratio promoted the dissolution of Ga, Fe and As, whereas higher reaction temperature and oxygen partial pressure weakened the leaching. Based on the results, leaching parameters were optimized for enhancing Ga recovery. Through weakening the 1st oxidation pressure leaching (by decreasing reaction temperature and total pressure to 90 °C and 0.2 MPa, respectively) and strengthening the 3rd atmospheric leaching (by increasing H2SO4 concentration and reaction temperature to 160 g/L and 85 °C, respectively), the leaching efficiency of Ga increased from 77.83% to 96.46%.

Highly selective separation of germanium from sulfuric solution using an anion exchange D201 × 7 resin with tartaric acid

Germanium (Ge) exhibits excellent optical and electrical properties. Due to the low reserves of Ge and lack of independent mineral resources, zinc refinery residues have become an important source of Ge. In this work, a D201 × 7 resin has been employed in the selective separation of Ge from a sulfuric solution using tartaric acid as a complexing agent. In the sulfuric acid system, Ge(OH)4 was converted to an anionic complex [GeO2(OH)2C4H4O4]2− at a 1:1 tartaric acid to Ge molar ratio. The anion exchange D201 × 7 resin adsorbed the Ge tartrate anionic complex. The adsorption process exhibited pseudo-second-order kinetic behavior and adhered to the Langmuir isothermal adsorption model. The maximum adsorption capacity of D201 × 7 resin for Ge was 214 mg g−1. Selective Ge uptake and purification could proceed by column separation The results showed that enrichment factor was 74.7, and the desorption concentration of Ge was increased from 500 mg L−1 to 36.6 g L−1. The D201 × 7 resin exhibited high selectivity, excellent adsorption performance and good stability, making it a viable candidate in industrial applications.

Selective removal and recovery of gallium and germanium from synthetic zinc refinery residues using biosorption and bioprecipitation.

The depletion of primary ores, the environmental concerns related to mining activities, and the need to promote circular economy has drawn attention to the recycling of metallic compounds. Bio-based technologies are suitable for metal recovery, as they operate under mild conditions (ambient temperature and pressure) and are ideal for treating low-concentration waters. This study compared the effectiveness of adsorption and precipitation for the removal and recovery of gallium, germanium and zinc. Adsorption of the metallic ions on elemental forms of sulfur (S0), selenium (Se0) and tellurium (Te0), both of chemical and biological sources, was tested. Biosorption onto elemental forms of S0bio, Se0bio and Te0bio effectively removed Ga and Zn. The highest removal efficiency (ղ) was obtained for Ga onto the adsorbent Te0bio (69±0.4%), with an adsorption capacity (q) of 74mgGa (g Te0bio)-1, followed by Zn (ղ=40±0.7%) with 43mg Zn (g Te0bio)-1. Precipitation with chemical and biogenic sulfide at different metal to sulfide (Me/S) ratios was also assessed. Biologically produced sulfide was more efficient for Ga and Zn compared to chemical sulfide. Precipitation with biogenic sulfide was efficient for the removal of Ga (ղ=59.9±2.6%) and Zn (ղ=44.2±3.0%). The lowest ratio between metal to sulfide (Me/S=0.2) achieved higher zinc removal efficiencies, whereas gallium removal was more efficient at Me/S=1.5. None of the tested methods allowed for recovery of Ge. Biosorption and bioprecipitation gave nevertheless high removal and recovery of Ga and Zn.

Effect of dilution on the performance of ionic liquids in milliflow solvent extraction applications: Towards integration of extraction, scrubbing and stripping operations with in-line membrane-based phase separation

The combination of ionic liquids (ILs) and millifluidic reactors is often suggested as a form of process intensification. The high viscosity of ILs has, however, raised concerns about hydrodynamics, mass-transfer enhancement and the ability to integrate several millifluidic operations. In the present study the performance of a quaternary ammonium hydrogensulfate IL, [A336][HSO4], in a millifluidic solvent extraction (SX) process was evaluated and compared with various, lower viscosity solutions of the IL in a diluent. Dilution of [A336][HSO4] significantly improved the slug flow hydrodynamics by reducing the film thickness, avoiding the loss of secondary recirculations inside the plugs and improving stability at elevated flow rates. The overall mass-transfer performance of the system was also improved upon dilution by a balancing of mass-transfer and reaction limitations. It was also observed that dilution reduced reagent consumption and improved the extraction selectivity. In addition, the decrease of the viscosity of the IL upon dilution facilitated the use of an in-line membrane-based phase separator. An integrated millifluidic set-up containing an extraction, scrubbing and stripping reactor was built using these in-line phase separators and applied to the SX purification of germanium from a synthetic zinc refinery residue leachate. The integrated reactor system was operated using a 30 vol% [A336][HSO4] dilution in p-cymene and successfully run for 4 h without any loss in separation performance or stability.

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.

Application of zinc ferrite reduction in the extraction of Zn, Ga and In from zinc refinery residue

Extraction of gallium and indium from zinc refinery residue (ZRR) has continued to attract attention because of different mineralogy of residues and occurrences of trace elements in ZRR. About 90% of gallium is currently extracted from Bayer liquor, whereas, ZRR has been a primary source for indium recovery. The primary production of gallium and indium in USA is currently zero. However, zinc residues are a promising resource for the extraction of critical metals such as gallium, germanium and indium. The major problem in ZRR is the concentration of zinc ferrite (ZF) which is refractory to leaching. The current study introduces a method to enhance the leaching kinetics of ZRR having ZF as major constituent. In this study, ZF was partially reduced with reducing gas containing 10% H2 and the roasting product was then leached under different conditions. The effect of reduction roasting was found to have a significant impact on the leaching kinetics of ZRR. The decomposition of ZF eased the leaching of zinc, gallium and indium. More than 90% extraction of the target elements was achieved with this process. The manuscript also discusses the characterization of ZRR using laser ablation inductively coupled plasma-mass spectrometry (LA ICP-MS), scanning electron microscopy (SEM), x-ray diffraction (XRD) and automated mineralogy.

Need of Gallium Recovery from Waste Samples: A Review

Gallium is an vital rare metal mainly because of its growing demand in different domain of life. It has wide applications. Gallium is considered as the backbone of the electronics industry. The supply and demand of gallium-bearing products has gradually increased during the past decade. Therefore, from the environmental stand point the need for sensitive and reliable methods for determining trace concentrations of gallium has become apparent in various fields. Gallium has become increasingly popular as a substrate material for electronic devices. Aside from ore, gallium can be obtained from such industrial sources as the Bayer process caustic liquor that is a byproduct of bauxite processing, flue dust removed from the fume-collection system in plants that produce aluminum by the electrolytic process, zinc refinery residues, gallium scrap materials, and coal fly ash. The purification process for gallium can start with solvent-extraction processes where the concentrations of impurities, especially metals, are reduced to the ppm range. The main aim of this paper is to simply put up the salient facts regarding gallium and identify applicable sources of information thereby one may create a suitable environment for the development of methods for the production of gallium via leaching through various waste samples.

Hydrometallurgical process for recovery of Zn, Pb, Ga and Ge from Zn refinery residues

Zn, Pb, Ga and Ge were separated and recovered from zinc refinery residues by stepwise leaching. In the first stage, by leaching with H 2 SO 4 media, more than 90% of Zn and 99% of Ga were dissolved, leaving 92% of Ge in the leaching residue. In the second stage, by leaching with HCl media, approximately 99% of Pb and less than 2% of Ge were selectively dissolved. Finally, the remaining 90% of Ge was extracted in 1 mol/L NaOH solution by destroying the correlation between SiO 2 and Ge. XRD pattern of the leaching residue demonstrated that ZnSO 4 ·H 2 O, PbSO 4 and SiO 2 were removed sequentially through the stepwise leaching. The proposed process achieved high recoveries of Zn, Pb, Ga and Ge, thus presenting a potential industrial application.

Selective Extraction of Zinc from Zinc Ferrite

The presence of iron in sphalerite induces the formation of zinc ferrite (ZF) during roasting. Zinc refinery residues (ZRR) and electric arc furnace dust (EAFD) contain a significant amount of zinc ferrite and are difficult to treat. According to the literature, up to 71% ZF has been found to be present in ZRR. The dissolution of zinc ferrite is inefficient even in aqua regia. The Waelz process is an existing process to recover zinc from electric arc furnace dust by reduction using carbon monoxide followed by the volatilization of zinc. In this study, zinc was selectively extracted from zinc ferrite by partial reduction of zinc ferrite at relatively low temperature followed by leaching in dilute sulfuric acid (20 g/L). Pure zinc ferrite samples were partially reduced to zinc oxide and magnetite by using H2 gas as a reductant. The presence of magnetite and zinc oxide was confirmed by X-ray diffraction (XRD) technique. A maximum of 95% zinc extraction was achieved after leaching with sulfuric acid on the reacted samples. The paper also discusses the effect of time, temperature, and concentration of H2 in the reducing gas on the extraction of zinc and iron from ZF.

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.

Recovery and separation of silver and mercury from hazardous zinc refinery residues produced by zinc oxygen pressure leaching

Hazardous zinc refinery residues that contain Ag and Hg are a typical complex material obtained from zinc oxygen pressure leaching and currently there are few economically viable methods for disposal or reuse. The research presented here offers an effective approach for the comprehensive recovery of Zn, Fe, Cu, Ag and Hg from this highly toxic waste. During the initial hot-acid leaching stage, leaching efficiencies of 96.3% Zn, 96.0% Fe and 97.5% Cu were obtained, whereas the leaching of Ag and Hg were <0.2%. This resulted in the simultaneous separation of Zn, Fe and Cu and the enrichment of Ag and Hg ca. 300%. Subsequently, the leaching residues obtained from hot-acid leaching was further leached using acidic thiourea solution (pH = 1). The results of this second leaching step showed the almost 93% of Ag and 98% of Hg could be extracted using 20 g/L thiourea and 4 g/L Fe3+, with a L/S ratio of 8 and a temperature of 40 °C for 2 h. The residue after thiourea leaching could be used as raw material in lead smelting. In the next step based on zinc powder cementation, the recovery of Ag and Hg both reached 99.0% and the cementation residue comprised of 53.1 wt% Ag and 11.7 wt% Hg. The main phases present included Ag, Hg3Ag2 and Ag2S and these can be further treated by vacuum distillation in order to separate Hg from Ag. These findings demonstrate that high recoveries of Zn, Fe, Cu, Ag and Hg from the toxic waste could be achieved with stepwise leaching followed by zinc powder cementation. This treatment protocol for toxic zinc refinery residues not only avoids the potential harm to the environment but also significantly improves the economics of the process.

Leaching behavior of zinc and copper from zinc refinery residue and filtration performance of pulp under the hydrothermal process

This study aims to investigate the leaching behavior and filtration performance of zinc refinery residue under hydrothermal conditions. The relationships between the structure and morphology of silicon in the leaching residue and the pulp filtration performance were explored by determining the pulp filtration speed, analyzing quantitatively the silicon content in the leachate, and characterizing the leaching residue structure. The results show that hydrothermal leaching induces the coagulation–hydrolysis of the silicon in solution, consequently altering the microstructure of the leaching residue, and that silicon oxygen tetrahedra ([SiO4]4−) form the main skeleton structure of the residue. The results obtained also show that the leaching rates of zinc and copper are 98.1% and 98.7%, respectively, and that the filtration speed is 526.32 L/(m2·h) under the conditions of sulfuric acid concentration of 140 g/L, leaching temperature of 160°C, leaching time of 3.0 h, oxygen partial pressure of 0.75 MPa, stirring speed of 600 r/min, and a liquid-to-solid ratio of 10 mL/g.

Selective extraction of zinc, gallium, and germanium from zinc refinery residue using two stage acid and alkaline leaching

In this research, zinc, gallium, and germanium were selectively dissolved from zinc refinery residue by stepwise leaching. The thermodynamic study demonstrated that Zn, Ga, and Ge could be selectively leached by controlling a suitable pH condition. In the first stage of leaching with sulfuric acid media, >93% of the Zn content, approximately 100% of the Ga content, and <8% of the Ge content were leached using 2 Mol/L H2SO4 with a liquid-solid ratio of 10 mL/g at 80 °C for 4 h. in the second stage of leaching with sodium hydroxide media, about 90% of the Ge content and 33% of the lead content were extracted using 1 Mol/L NaOH with a liquid-solid ratio of 20 mL/g at 80 °C for 4 h.

Recovery of germanium from acid leach solutions of zinc refinery residue using an oxime extractant of HBL101

An oxime extractant of HBL101 was used to extract germanium from acid leach solutions of zinc refinary residues. The effect of acidity on extraction was investigated. Germanium was extracted from a sulphate acid solution with not too high acidity (1.0∼1.2 mol/L H2SO4), while zinc, cadmium, iron, gallium and arsenic were not extracted. Only small amount of copper was co-extracted. The germanium was readily stripped from the loaded organic solution with NaOH solutions. After germanium stripping, the co-extracted copper can be stripped using 2 mol/L H2SO4 while the extractant regenerated for recycling. The system was optimised in terms of organic composition and conditions of extraction and stripping and further characterised in terms of extraction and stripping kinetics and distribution isotherms. More than 98.5% of germanium was extracted in five-stage counter current extraction using an organic system of 30% HBL101 and 70% sulphonated kerosene and a feed containing 0.25 g/L Ge and 113 g/L H2SO4 with an A/O ratio of 4:1 at 25 °C for 20 min. The loaded organic containing 0.905 g/L Ge was stripped using 3.75 mol/L NaOH solution in five-stage counter current stripping with an A/O ratio of 1:4 at 25 °C for 25 min to selectively strip germanium followed by using 2 mol/L H2SO4 to strip co-extracted copper for recycling. The concentration of Ge in strip liquor reached 3.56 g/L.

Recovery and separation of gallium(III) and germanium(IV) from zinc refinery residues : Part II: Solvent extraction

The extraction of both Ga(III) and Ge(IV) was achieved using an organic system consisting of tri(octyl-decyl) amine (N235), tributyl phosphate (TBP) in sulfonated kerosene from iron-removed leach solution. The extraction equilibria of both metals were obtained within 10min at 30°C. More than 99.0% Ga(III) and 99.8% Ge(IV) were extracted in a three-stage counter current extraction using an organic system consisting of 20% (v/v) N235, 10% (v/v) TBP and 70% (v/v) sulfonated kerosene at an A/O ratio of 3:1 and 30°C for 10min. Over 99.0% Ga(III) was selectively stripped from the loaded organic solution by three-stage counter current stripping using 2.5mol/L H2SO4 at an A/O ratio of 1:2 and 30°C for 15min, resulting in a loaded strip liquor containing 3.8g/L Ga(III). After Ga(III) stripping, 99.8% Ge(IV) was stripped by two-stage counter current stripping using 4mol/L NaOH at an A/O ratio of 1:3 and 40°C for 15min, resulting in a final loaded strip liquor containing 8.3g/L Ge(IV). A conceptual flowsheet has been developed to recover Ga(III) and Ge(IV) from zinc refinery residues using two-stage leaching with H2SO4 and oxalic acid, subsequently, iron removal with iron powder and solvent extraction with N235 and TBP.

Extraction of Ga and Ge from zinc refinery residues in H2C2O4 solutions containing H2O2

A new oxalic acid (H2C2O4) and hydrogen peroxide (H2O2) based extraction process was developed to recover valuable metals - in particular Ga and Ge - from the zinc refinery residues. H2C2O4 and H2O2 leaching studies indicated that the selective leaching of metals in the residues, that primarily contain Zn, Cu, Fe, SiO2, Ga and Ge, can be achieved. Under the optimal leaching conditions ([H2C2O4]=110g/L, [H2O2]=0.12mol/L, L/S ratio=8, T=40°C and t=30min), 99.32% of the Ga, 98.86% of the Ge and 30.25% of the Fe were leached out, whereas the leaching of Zn, Cu and Si only reached 0.30%, 0.82% and 0.43%, respectively. Concerning leachate purification, 98.31% of the iron could be removed in the form of FeC2O4·2H2O with minor losses of Ga and Ge (1.08% and 0.68%) using an ultrasound-assisted iron powder replacement method under optimal conditions. The Ga (99.36%) and Ge (99.89%) were subsequently extracted by tri(octyl-decyl)amine (N235). After extraction, the loaded organic phase was stripped of Ga (98.91%) and Ge (99.21%) into separate solutions using sequential treatments of 2mol/L H2SO4 and 4mol/L NaOH respectively. Based on these results, a process flow sheet of efficient separation and recovery of Ga and Ge is presented.

Recovery and separation of gallium(III) and germanium(IV) from zinc refinery residues: Part I: Leaching and iron(III) removal

In this research, gallium and germanium were separated and recovered from zinc refinery residues by a two-stage leaching. In the first leaching stage with sulfuric acid media, 92% of zinc and 94% of copper were leached resulting in significant gallium and germanium enrichment up to ca. 300%. In the second leaching stage with oxalic acid media, the effects of H2C2O4 concentration, leaching time, liquid-to-solid (L/S) ratio and temperature on the recovery of gallium and germanium were investigated. More than 96% of gallium and 99% of germanium were leached out using 70g/L H2C2O4 with a L/S ratio of 10 at 90°C for 2h. The removal of iron in the H2C2O4 leach solution was carried out using an ultrasound-assisted ferrous iron precipitation method in which >96% of Fe(III) was removed in the form of FeC2O4·2H2O with minor losses of Ga(III) and Ge(IV) (1.4% and 1.3%). The results indicated that high recoveries of gallium and germanium from the zinc refinery residues could be achieved with two-stage leaching method.

Extraction of gallium and germanium from zinc refinery residues by pressure acid leaching

Pressure acid leaching of zinc refinery residues containing 0.266wt.% Ga and 0.363wt.% Ge was performed. The effects of the experimental parameters on the leaching of gallium and germanium and the filtration performance of the leach slurry were systematically investigated. The results show that the losses of Ge and Ga rapidly decreased because of the aggregation of amorphous silica under the pressure leaching conditions. Furthermore, the Ge leaching and filtration performance of the leach slurry were improved by adding calcium nitrate, which can be attributed to the oxidation of metallic Ge and its sulfides and the formation of calcium sulfate. The optimal leaching conditions are as follows: temperature of 150°C sulfuric acid concentration of 156gL−1, liquid-to-solid ratio (mL/g) of 8, total pressure of 0.40MPa, calcium nitrate addition of 20gL−1, stirring rate of 300rmin−1, and leaching time of 3h. Under the optimal conditions, more than 98% of the Ga and 94% of the Ge were leached. Moreover, the filtration rate of the studied leach slurry was 20 times faster than that of the leach slurry that was obtained under atmospheric pressure acid leaching conditions.

Recovery of indium and gallium from synthetic leach solution of zinc refinery residues using synergistic solvent extraction with LIX 63 and Versatic 10 acid

A synergistic solvent extraction (SSX) system consisting LIX 63 and Versatic 10, which are both commercially available, was selected to recover both Ga(III) and In(III) from synthetic sulfate leach solutions of zinc refinery cementation residues in one circuit. With the optimum composition of the SSX system, 86% In(III) and 92% Ga(III) were extracted in a single contact at pH3.0. The extraction and stripping kinetics of In(III) and Ga(III) were fast at 40°C. In(III) and Ga(III) were stripped readily using solution with low acidity of 0.05M H2SO4. Based on the McCabe–Thiele diagrams constructed, 4 stages of extraction at an A/O ratio of 1.2 and 3 stages of stripping at an O/A ratio of 5 are required for the extraction and stripping of both In(III) and Ga(III). The synergistic effect on In(III) extraction was significant while that on Ga(III), extraction was insignificant. A conceptual flowsheet is proposed including the SSX system consisting of reagents that are all commercially available and offers the advantages of recovering both In(III) and Ga(III) in one circuit and stripping with low acidity solutions.