Recovery of Zn(II), Mn(II) and Co(II) from the zinc plant residue using the solvent extraction with CYANEX 302 and D2EHPA/TBP: Stoichiometry and structural studies

Abstract

Zinc plant residues are produced during the zinc cathode production. Impurities such as Co are removed during the “Hot Purification Stage” and the residue from this stage is known as the zinc hot filter cake (HFC) which contains 21.4% (w/w) Zn, 0.55% Co, and 8.3% Mn. A solvent extraction (SX) method was used to extract the metal species from the zinc hot filter cake (HFC) leach solution. First, Zn(II) was extracted up to 96% from the solution by CYANEX 302 diluted in kerosene at 25 °C, the O/A ratio of 1:1 and pH = 2.5. After Zn(II) was effectively removed, the extraction of Mn(II) and Co(II) was investigated using the synergistic effects of TBP with D2EHPA diluted in kerosene. Around 96.6% of Mn(II), at an equilibrium pH of 4, was extracted using the mixture solution of D2EHPA and TBP at the ratio of 1:1. With Zn(II) and Mn(II) separated, a pure Co(II) solution remained. According to the FT-IR measurements and slope analysis method, the reaction between Zn/CYANEX 302 (HA) and Mn/D2EHPA (HB)/TBP was determined. Based on the results, ZnA2(HA) and MnB2.2HB.TBP were determined to be the probable extracted species in the organic phase.