Thermodynamics and Kinetics of Au(III) Adsorption on Silica Gel Chemically Modified by Diethylenetriamine Bis(methylene phosphonic acid)

Abstract

Silica gel chemically modified by diethylenetriamine bis(methylene phosphonic acid) (denoted as SG-D-P) has been developed. A thermodynamics and kinetics investigation of SG-D-P for the adsorption of Au(III) from aqueous solutions is reported in this work. The Langmuir and Freundlich isotherm models were applied to analyze the experimental data, and the best interpretation for the experimental data was given by the Langmuir isotherm equation; the maximum adsorption capacity for Au(III) is 416.67 mg·g −1 at 35 °C. The research results show that SG-D-P could reach the saturation adsorption capacity within 4 h, and its excellent adsorption capacity for Au(III) was 499.22 mg·g −1 when the initial solution concentration was 2.0 mmol·L −1 at 35 °C. Its adsorption kinetics can be modeled by a pseudo second-order rate equation, and the thermodynamic parameters Δ G, Δ H, and Δ S are −21.18 kJ·mol −1, 16.59 kJ·mol −1, and 122.86 J·K −1 ·mol −1, respectively.