Abstract
The kinetics of forward extraction [AuCl4]− from aqua regia medium by diethylene glycol dibutyl ether (DBC) have been investigated by the Lewis cell (LC) technique. At first gold extraction has been carried out under different experimental conditions for achieving the stoichiometry coefficients and the value of the extraction equilibrium constant (K=0.1). For kinetic data treatment, flux ‘F’ method has been applied. Reaction order with respect to DBC, pH and [AuCl4]− was determined and then the rate constant was calculated. The rate of gold extraction from 2M chloride medium can be expressed as F=100.88[AuCl4−]1.25 [DBC]0.4 [H+]−0.22. Kinetics data were treated by EVIEWS software and coefficients were obtained. The comparison of manual and software results indicated that the results had good conformity. Influence of temperature was studied and then activation energy, Ea, (11.17kJ/mol), activation enthalpy (11.66kJ/mol) and entropy (−187J/molK) were calculated by using Arrhenius and activation complex theory respectively. Ea value (<20.9kJ/mol) indicates that, the extraction of gold (III) in the investigated system is controlled by diffusion process.
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