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An efficient flotation process was developed to selectively recover elemental sulfur from a high-sulfur pressure acid leaching residue of zinc sulfide concentrate. The process mineralogy analysis showed that the sulfur content reached 46.21%, and 81.97% of the sulfur existed as elemental sulfur which was the major mineral in the residue and primarily existed as pellet aggregate and biconical euhedral crystal. An elemental sulfur concentrate product with 99.9% of recovery and 83.46% of purity was obtained using the flotation process of one-time blank rougher, two-time agent-added roughers, and two-time cleaners with Z-200 as collector and Na2S + ZnSO4 + Na2SO3 as depressant. The flotation experiment using return water indicated that the cycle use of return water had no adverse effect on the flotation performance of elemental sulfur. The process mineralogy analysis manifested that main minerals in the residue directionally went into the flotation products. Most of elemental sulfur entered the concentrate while other minerals almost completely went into the tailing. Main valuable elements lead, zinc, and silver entered the tailing with sulfides and could be recovered by lead smelting. The proposed process can realize the comprehensive recovery of valuable components in the high-sulfur residue and thus it has wide industrial application prospect.

In this research, an integrated hydrometallurgical process for comprehensive recovery of valued metals and safe disposal of arsenic from copper smelting open-circuit (CSO) dust was developed. By sulfuric acid leaching, Cu, As, Zn and Cd can be selectively extracted into leachate while Pb and Bi were remained in the residue. Then, iron powder cementation, iron salt precipitation and Na2CO3 neutralization precipitation were adopt to successively recover Cu as sponge copper, remove As mainly as thermodynamically stable ferric arsenate and recover Zn and Cd as basic sulfate. Afterwards, the obtained ferric arsenate residue was solidified by cement with additive fulvic acid (FA). FA had an excellent performance and it can reduce arsenic leachability to 1.5 mg/L. The zeta potential, FTIR and SEM analyses indicated that FA chemically adsorbed onto the surfaces of ferric arsenate residue and cement hydrates through carboxylate groups. FA promoted the deposition of cement or cement hydrates on the surface of ferric arsenate residue, thereby enhancing the physical encapsulation of arsenic residue. This research demonstrates the possibility of comprehensively recovering metals and safely disposing arsenic from hazardous waste CSO dust by the developed integrated hydrometallurgical process, and thus it has good industrial application prospect.

In this paper, a typical zinc sulfide concentrate has been studied in detail by process mineralogy. Its main mineral composition and occurrence state of elements were identified. In addition, the effects of technological conditions such as temperature and acidity on the pressure leaching were investigated. The phase transformation of iron was analyzed and the related mechanism was explained. At the same time, the latest experimental progress in the field of zinc pressure leaching, such as leaching process, leaching kinetics, elemental behavior, and phase transformation in the process of pressure leaching, is also introduced.

A clean and efficient hydrometallurgical process was developed to recover Cu, Zn, Cd, Bi and Pb from the hazardous solid waste of copper smelting open-circuit (CSO) dust using the hazardous effluent of waste acid as leaching agent. By waste acid leaching-iron powder cementation, Cu was recovered as sponge copper. After As in the barren solution was removed mainly as thermodynamically stable ferric arsenate by iron salt precipitation, the Zn and Cd were simultaneously precipitated into zinc and cadmium residue through Na2CO3 neutralization. Bi in the waste acid leaching residue was recovered as bismuth oxychloride via chloride leaching-hydrolysis precipitation, and Pb was enriched in the form of PbSO4 in the chloride leaching reside (i.e. lead concentrate). 99.0% of total Cu, 86.8% of total Zn, 81.7% of total Cd, 90.4% of total Bi and 98.9% of total Pb in the CSO dust and waste acid entered their separate products. The input–output analysis demonstrates that a high revenue of 3803.4 CNY is gained for treating one ton of the CSO dust by the developed process. This process can realize waste treatment by waste and comprehensively recover valued metals from both of hazardous wastes simultaneously, and thus has good industrial application prospect.

A systematic and comparative research was performed using copper, nickel and cobalt-ammonia catalyzed thiosulfate processes for environmentally friendly and efficient gold extraction from an oxide gold concentrate. 88.3% of gold was leached by thiosulfate with conventional copper-ammonia catalysis while its thiosulfate consumption was as high as 53.6 kg/t-concentrate. Thiosulfate consumption was reduced to 26.5 and 30.6 kg/t-concentrate, and 81.2% and 90.2% of gold leaching percentages were obtained with nickel-ammonia and cobalt-ammonia catalyses. The electrochemical leaching mechanism combined with XPS and SEM-EDS analyses illustrated the essential reason for the differences of three catalyses in gold leaching percentage and thiosulfate consumption. For copper-ammonia catalysis, two-stage desorption was required to desorb gold from the gold-loaded resin due to the co-adsorption of copper with gold while one-stage desorption was feasible for nickel-ammonia and cobalt-ammonia catalyses because nickel and cobalt did not co-adsorb with gold, and their gold recovery percentages were 82.4%, 98.5%, 97.7%, respectively. After 6-time cycles of barren leachate, the gold leaching and recovery percentages of copper-ammonia catalysis considerably decreased while those of nickel-ammonia and cobalt-ammonia catalyses only declined slightly. Thiosulfate leaching with cobalt-ammonia catalysis has the advantages of high gold leaching percentage, low thiosulfate consumption, simple desorption process, good leachate stability and recycle performance of barren leachate, and therefore it has a bright industrial application prospect.

The electronic structure of tetrahedrite and effect of four typical natural impurities including zinc, arsenic, iron and silver on its flotation property were systematically studied through density functional theory. The band structure and surface energy calculation show that tetrahedrite is a p-type semiconductor and has no cleavage plane. The frontier orbital energy analysis indicates that compared with chalcopyrite, the flotation separation of tetrahedrite from commonly associated galena, sphalerite and pyrite is more difficult. The Hirshfeld population analysis shows that in comparison with tetrahedrite, chalcopyrite and pyrite, galena and sphalerite have stronger electrostatic attraction to flotation agents, and galena has an obviously better natural floatability than the four other sulfides. The band structure and frontier orbital energy analyses for impurity-bearing tetrahedrites show that they are all p-type semiconductors with better electrical conductivity than pure tetrahedrite, and iron impurity increases the difficulty of tetrahedrite’s flotation separation from galena, sphalerite and pyrite. The Hirshfeld population analysis manifests that zinc and silver impurities enhance tetrahedrite’s electrostatic attraction to flotation reagents while arsenic and iron work in the opposite. Moreover, silver impurity lowers tetrahedrite’s natural floatability while zinc, arsenic and iron have no obvious effects.

O-isopropyl-N-ethyl thionocarbamate (IPETC) collector was used to selectively recover elemental sulfur from a high-sulfur residue, and its flotation performance, structure–property relationship and adsorption mechanism to elemental sulfur were studied. The raw ore flotation test showed that IPETC displayed superior flotation performance to the elemental sulfur compared with sodium ethyl xanthate (SEX) and ammonium dibutyl dithiophosphate (ADDTP) collectors. Pure mineral flotation and adsorption experiments further demonstrated that among the three collectors, IPETC had the strongest collecting power and the optimum selectivity towards elemental sulfur. The structure–property relationship research based on density functional theory (DFT) calculation supported the above conclusion. The adsorption mechanism analysis manifested that IPETC adsorption on elemental sulfur surface was a chemical process by separately generating normal covalent bond between carbonyl S atom and S atom and a backdonation covalent bond between O atom and S atom, which was confirmed by the FTIR spectrum analysis result. IPETC exhibits excellent collecting ability and selectivity for elemental sulfur and therefore it has bright application prospects.

Dissolved iron exerts significant effects on mineral leaching, impurity removal, and solution purification in the zinc hydrometallurgy process. To date, iron oxidation and migration behaviors are yet to be fully understood and further research on effective regulation mechanisms of iron is required. In this paper, zinc sulfide concentrate was used as the research object. The behaviors of both Zn and Fe during pressure leaching were investigated for varying temperature, acid addition, and leaching time. At temperature of 100~160 &deg, C, H2SO4/Zn ratio of 0.9:1&ndash, 1.25:1, and leaching time of 0.5&ndash, 2.5 h, the zinc extraction increased with temperature, acidity and leaching time. The iron extraction, however, varied differently with increasing temperature, acidity and leaching time: (A) it increased with temperature to 150 &deg, C and then decreased at higher temperature, and (B) displayed an initial increase followed by a decrease with respect to the leaching time. Based on the characteristics of the residue phase, chemical phase analysis was used to analyze the residue in detail. The extent of dissolution of iron-containing minerals and the extent of precipitation of ferric ions during the leaching process were quantitatively calculated.