Solvent extraction of copper, zinc, cadmium and nickel from sulfate solution in mixer settler unit (MSU)

The disposal of large quantities of electronic scraps generated globally is causing not only environmental
pollution but also loss of valuable resources. Therefore, R&D efforts have been made to develop a suitable
solvent extraction (SX) process for extraction and separation of various metals viz. copper, zinc, cadmium
and nickel from the solution expected from the leaching of e-scraps. Different process parameters viz. pH,
aqueous to organic ratio, extraction isotherm to establish stage requirement for extraction in continuous
mode, etc. have been studied to optimize the condition for the separation of metals. The studies showed
the selective extraction of copper after iron precipitation from the sulfuric acid leach solution of e-wastes
containing 0.92 g/L Cu and minor impurities with 2-hydroxy-5-nonylacetophenoneoxime (LIX 84) above
pH 2.0 in single stage. Further, extraction of zinc, nickel and cadmium was carried out using Cyanex 302.
It was found that complete extraction of cadmium and zinc was taken place simultaneously using 2.5%
Cyanex at eq. pH 2.1 leaving nickel in the aqueous raffinate, moreover Zn and Cd was selectively stripped
out using 10% H2SO4 and 10% HCl, respectively. Based on the above studies a complete process flow sheet
has been developed for separation/recovery to Cu, Zn, Cd and Ni from the leach liquor of e-waste.