Removal of transition metal ions from aqueous solutions by adsorption using a novel hybrid material silica gel chemically modified by triethylenetetraminomethylenephosphonic acid

A novel inorganic-organic hybrid material silica gel chemically modified by triethylenetetraminomethylenephosphonic acid (denoted as GH-T-P) has been synthesized and characterized. Its adsorption properties GH-T-P for Au(III), Hg(II), Cu(II), Pb(II), Co(II), Zn(II), Ni(II), Cr(III) and Cd(II) have been investigated, and the research results revealed that GH-T-P has the best adsorption capacity for Au(III). Furthermore, the adsorption selectivity results of GH-T-P for Au(III) displayed that GH-T-P had excellent adsorption for Au(III) in binary ions systems, especially in the systems of Au(III)-Zn(II), Au(III)-Ni(II) and Au(III)-Cr(III). 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. GH-T-P could reach to the saturation adsorption capacity within 2 h, and its excellent adsorption capacity for Au(III) was 266.49 mg/g when the initial solution concentration was 2.0 mmol/L at 35 degrees C. Moreover, the research revealed that its adsorption kinetics can be modeled by pseudo-second-order rate equation wonderfully, and the thermodynamic parameters Delta G, Delta H and Delta S were -20.79 kJ mol(-1), 5.17 kJ mol(-1), and 84.37J K-1 mol(-1), respectively. Thus, this novel hybrid material silica gel chemically modified by triethylenetetraminomethylenephosphonic acid GH-T-P is favorable and useful for the uptake of Au(III), and the high adsorption capacity and good reproducibility make it a good promising candidate material for the precious metal uptake. (C) 2010 Elsevier B.V. All rights reserved.