Abstract:
This work presents the extraction and stripping of mercury from synthetic wastewater by vegetable oils, an environmentally friendly substance, via a hollow fiber supported liquid membrane in accordance with the principle and basis of the solvent extraction method. Results demonstrate that corn oil proved to be the most efficient solvent for mercury extraction, and it can also selectively extract mercury from other metal ions contaminated in synthetic wastewater. The study of the influence of factors affecting the percentage of mercury extraction and recovery using the Box-Behnken experimental design revealed that temperature, pH of the synthetic wastewater, and stripping concentration all significantly. Under optimal conditions, results demonstrate that mercury extraction and stripping percentages reach 96.14% and 40.13%, respectively at temperature 323.15 K, pH 3, 1.2 M of HCl concentration, and 100 ml/min of flow rate. The mechanism of mercury extraction is induced by the formation of halogen bonds between mercury and fatty acids in the carboxylic group, as supported by spectroscopy and density functional theory. The thermodynamic properties of this reaction reveal the calculated standard enthalpy change and the calculated standard Gibbs free energy change: -23.71 kJ∙mol-1 and 24.38 kJ∙mol-1. In addition, extraction and stripping kinetics are found to be of the first order (k = 0.182 min-1) and zero-order (k = 0.9244 L∙mg-1min-1), respectively. It is seen that this method has the ability to successfully remove mercury while still remaining below the standard discharge level.