Optimizing extraction of Iron, Copper and Zinc from Cobalt-pregnant electrolyte by ph-based four-stage process

Abstract

Optimization of recovery of iron (Fe), copper (Cu) and zinc (Zn) using di-2-ethylhexyl phosphoric acid (D2EHPA) was accomplished by pH-based four-stage extraction process, where NaOH, HCl, Shell-sol 3525 and H2SO4 were used as solvents. Laboratory tests were carried out on 8 samples collected from solvent-extraction unit at set pH values, feed concentration and flow rate, temperature, purity of cobalt (Co) solution and extractant concentration to optimize removal of Fe, Cu, and Zn from Co-pregnant solution. The samples used were 200 L of 150 g/L H2SO4, 200 L of 180 g/L HCl, 20 L of 30 g/L NaOH and 2 - 3.5 % concentrations of D2EHPA. The extraction of Fe3+ increased from 88 to 99 % when D2EHPA concentration was increased from 2 to 3 % (an increase of 11 %). The extraction of Zn2+ increased from 84 to 96 % in 3 days, and 84 to 100 % in 4 days when concentration of D2EPHA was increased by 1.5 % (increase of 12 % and 16 % respectively). A 1.5 % increase in concentration of D2EPHA produced 44 % increase of Cu2+ extraction efficiency in 3 days. The extraction efficiencies of Zn and Fe were twice that of Cu when D2EPHA in shell-sol 3525 was used as extractant at 3.5 % concentration D2EPHA.