Adsorption Kinetics of Au(III) Ions on a Novel Chelating Resin Silica-Gel Functionalized by an Amino Organophosphonic Acid

The adsorption kinetics of Au(III) on a novel chelating resin namely silica gel functionalized by an amino phosphonic acid (denoted as SiO₂–EDA–APA) were studied. The results showed that SiO₂–EDA–APA could reach its saturation adsorption capacity within 4 h, and its excellent adsorption capacity for Au(III) was 234.61 mg g ⁻¹ when the initial solution concentration was 2.0 mmol L ⁻¹ at 35°C. The adsorption kinetics of the as-synthesized hybrid adsorbent for Au(III) at different temperatures can be modelled closely by a pseudo second-order rate equation. The thermodynamic parameters of adsorption, ΔG, ΔH and ΔS were – 18.89 kJ mol ⁻¹, 19.82 kJ mol ⁻¹, and 125.74 J K⁻¹ mol ⁻¹, respectively. It can be concluded that the adsorption of Au(III) on SiO₂–EDA–APA is a spontaneous, endotherminc process controlled by film diffusion, which results in its higher adsorption capacity at higher temperatures.