Reductive acid leaching of cadmium fromzinc neutral leaching residue using hydrazine sulfate
(1. School of Metallurgy and Environment, Central South University, Changsha 410083, China;
2. School of Municipal and Mapping Engineering, Hunan City University, Yiyang 413000, China;
3. Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution,
Central South University, Changsha 410083, China)
2. School of Municipal and Mapping Engineering, Hunan City University, Yiyang 413000, China;
3. Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution,
Central South University, Changsha 410083, China)
Abstract: Zinc neutral leaching residue (ZNLR) from hydrometallurgical zinc smelting processing can be determined as hazardous intermediate containing considerable amounts of Cd and Zn which have great threats to the environment. The ZNLR contained approximately 35.99% Zn, 15.93% Fe and 0.26% Cd, and Cd mainly existed as ferrites in the ZNLR in this research. Reductive acid leaching of ZNLR was investigated. The effects of hydrazine sulfate concentration, initial sulfuric acid concentration, temperature, duration and liquid-to-solid ratio on the extraction of Cd, Zn and Fe were examined. The extraction efficiencies of Cd, Zn and Fe reached 90.81%, 95.83% and 94.19%, respectively when the leaching parameters were fixed as follows: hydrazine sulfate concentration, 33.3 g/L; sulfuric acid concentration, 80 g/L; temperature, 95 °C; duration of leaching, 120 min; liquid-to-solid ratio, 10 mL/g and agitation, 400 r/min. XRD and SEM-EDS analyses of the leaching residue confirmed that lead sulfate (PbSO4) and hydrazinium zinc sulfate((N2H5)2Zn(SO4)2) were the main phases remaining in the reductive leaching residue.
Key words: reductive acid leaching; zinc neutral leaching residue; hydrazine sulfate; cadmium