Separation of indium from lead smelting hazardous dust via leaching and solvent extraction

A separation and extraction of indium from lead smelting hazardous dust (LSHD) was studied systematically. The novel technological keys included the pressure sulfuric acid leaching of LSHD, precipitation and enrichment of indium, atmosphere sulfuric acid leaching of indium-enriched residues and solvent extraction of indium. The optimum parameters of each procedure were obtained. More than 99% zinc and 95% indium were leached from LSHD by two-stage countercurrent pressure sulfuric acid leaching using the initial CH2SO4 of the 1st stage 30-50 g/L, the initial CH2SO4 of the 2nd stage 120-150 g/L, temperature 413-433 K, total pressure 0.6-1.0 Mpa, time 1-1.5 h, L/S ratio 3-5/1 and agitation speed 400 r/min respectively. More than 97% indium was precipitated from the 1st pressure sulfuric acid leaching solution under the terminal neutralization pH 4.0, temperature 343-353 K and time 1 h. More than 96% indium was re-leached by two-stage countercurrent atmosphere sulfuric acid leaching from the indium-enrichment residues using L/S ratio 3-5/1, temperature 363-368 K, agitation speed 500 r/min, time 0.75-1.5 h, the initial CH2SO4 of the first stage and the second stage atmosphere sulfuric acid leaching with 40-50 g/L and 90-110 g/L, respectively. More than 98% indium was extracted by three-stage solvent extraction using 30% (v/v) di(2-ethylhexyl)phosphoric acid (D2EHPA), phase ratio 1/6, time 1 min and temperature 298 K.