Kinetic evaluation of simultaneous waste cooking oil hydrolysis and reactive liquid-liquid Cu extraction from synthetic Cu-containing wastewater: Effect of various co-contaminants

Abstract

Combination of oil hydrolysis reaction and reactive liquid-liquid extraction of Cu²⁺ from wastewater offers economic and environmental advantage than running two processes separately. To give better insight on the application of the proposed process to treat real wastewater, the effects of other pollutants (acid/base, chelating agents, organic solvent, anions) present in the synthetic Cu-containing wastewater were studied. The reaction was carried out in a batch reactor using a water/acylglycerides molar ratio of 30:1 at 225 °C up to 8 h to understand the effect of the studied parameters during the reaction time course. It was found that pH influenced acid/base balance, which governs catalysis and Cu-soap formation in subcritical water. Chelating agents formed strong complexation with Cu²⁺ that changed Cu removal mechanism from cation exchange reaction to that of conventional solvent extraction. The presence of organic solvents affected the dielectric constant of water that shifted the equilibrium of cation exchange reaction towards lipophilic Cu soap formation. Different anion type produced different type of acid by means of the cation exchange mechanism that influenced acid catalysis and Cu-soap formation. Other heavy metal cations expressed the same cation exchange mechanism and catalysis ability as that of Cu²⁺.