Liquid–Liquid Extraction Studies of Heavy Metals (Cd, Cr and Zn) from Phosphoric Acid Solutions Using C₁₁H₁₈N₂O as a Synthetic Agent

Abstract

Many researches have investigated the removal of cadmium as an impurity from phosphoric acid using various commercial and synthetic extracting agents. In this paper, the reaction mechanism of liquid-liquid extraction process of heavy metals like cadmium from the commercial phosphoric acid was studied. The extraction is carried out using the synthetic extracting agent hexahydrotrimethylquinazoline-2one (C₁₁H₁₈N₂O) diluted in benzene. Afterwards, a feasibility test of this synthesized extracting agent has been done to extract other metals like zinc and chromium from industrial phosphoric acid produced by hydrometallurgical way (wet process). The results showed that the reaction of liquid-liquid extraction process of cadmium from phosphoric acid solution by using C₁₁H₁₈N₂O as a extracting agent can be describe at equilibrium by: ${\text{Cd}}\left( {{\text{H}}_{2} {\text{PO}}_{4} } \right)_{{2{\text{aq}}}} + \left( {{\text{HA}}} \right)_{{2{\text{org}}}} \rightleftharpoons {\text{Cd}}\left( {{\text{H}}_{2} {\text{PO}}_{4} } \right)_{2} \left( {{\text{HA}}} \right)_{{2{\text{org}}}}$. The equilibrium constants were found to be log(K) = 1.38. By using industrial phosphoric acid, the extracting agent revealed its ability to extract cadmium, chromium and zinc with the extraction percentages of 77.6, 66.5 and 42.7% respectively.