Research On Selective Extraction And Separation Of Indium From Leaching Solution Of Indium-rich Slag In Zinc Hydrometallurgy

Bis(2-ethylhexyl)phosphate(abbreviation P204)is the most common and effective extractant for extraction,separation and enrichment of indium at present.However,the structure of the extracted compound is relatively stable and needs to be stripped with high-concentration hydrochloric acid.The residual chlorine ion and high-concentration chlorine wastewater bring harm to the environment and enterprise production.And there are many impurity ions in the loaded organic phase,which is easy to cause organic phase poisoning and aging.In this paper,on the basis of P204extractant,neutral phosphorus(phosphine)extractant was added to form a composite extraction system to weaken the stability of P204 combined with indium and improve the extraction and stripping properties.Sulfuric acid was used as the stripping agent to solve the environmental and production problems caused by hydrochloric acid as the stripping agent in the P204 system.And the sulfate solution obtained after the replacement of the stripping solution can be returned to the zinc hydrometallurgy.At the same time,the mechanism of extraction and stripping of indium from the leaching solution of indium-rich residue in zinc hydrometallurgy by P204 system,P204-TRPO system and P204-TOPO system,as well as the behavior of impurity ions zinc,iron,calcium and arsenic were studied.The main works and results as follows:(1)The behavior of P204 single extraction system for extracting and stripping indium from indium-rich residue leaching solution was studied.It was found that the extraction efficiency of indium was proportional to P204 concentration,time,temperature and phase ratio,and inversely proportional to sulfuric acid concentration.Under the optimized process conditions,the three-stage countercurrent extraction was performed,and the three-stage countercurrent stripping was performed with 6 mol/L hydrochloric acid.The extraction efficiency of indium was 99.41%,and the extraction rates of zinc,iron,calcium and arsenic were 1.81%,1.72%,2.08%and<0.1%,respectively.The stripping efficiency of indium reached 99.22%,and the stripping efficiency of zinc,iron and calcium were 88.12%,89.23%and 84.12%,respectively.(2)For P204-TRPO and P204-TOPO composite extraction system,the interaction between extractants,extraction mechanism and behavior of indium were investigated.It was found that TRPO and TOPO was associated with P204,which reduced the concentration of free P204,and the extraction efficiency of indium was slightly lower than that of P204 system(the degree of reduction depended on the amount of neutral phosphine added).Since TRPO and TOPO were not involved in the extraction reaction,so the extraction mechanism of indium by composite system belongs to cation exchange,and the extraction process can be expressed as a TRPO/TOPO molecule associated with a P204 dimer molecule.An In³⁺reacts with three P204 dimer molecules to form an In R₃·3(HR)structure extract,and releases three H⁺to the aqueous phase(P204 dimer molecules are represented by H₂R₂).(3)Using 10%P204-2%TRPO-88%sulfonated kerosene as the extraction system,three-stage countercurrent extraction and two-stage countercurrent stripping with sulfuric acid were carried out under optimized conditions.The extraction efficiency of indium were 99.10%,and the extraction efficiency of zinc,iron,calcium and arsenic were 1.21%,1.32%,0.8%and<0.1%,respectively.The stripping efficiency of indium is 98.60%,the stripping efficiency of zinc,iron and calcium is 91.42%,92.61% and90.31%,respectively.(4)Using 10%P204-4%TRPO-86%sulfonated kerosene as the extraction system,three-stage countercurrent extraction and one-stage countercurrent stripping with sulfuric acid were carried out under optimized conditions.The extraction efficiency of indium were 99.04%,and the extraction efficiency of zinc,iron,calcium and arsenic were 0.84%,1.03%,1.28%and<0.1%,respectively.The stripping efficiency of indium is 99.61%,the stripping efficiency of zinc,iron and calcium is 94.15%,95.05% and93.11%,respectively.