Adsorption of transition metal ions from aqueous solutions onto a novel silica gel matrix inorganic–organic composite material

A novel inorganic–organic composite material silica gel microspheres encapsulated by imidazole functionalized polystyrene (SG-PS-azo-IM) has been synthesized and characterized. This composite material was used to investigate the adsorption of Cr(III), Mn(II), Fe(III), Ni(II), Cu(II), Zn(II), Hg(II), Pb(II), Pd(II), Pt(II), Ag(I), and Au(III) from aqueous solutions, and the research results displayed that SG-PS-azo-IM has the highest adsorption capacity for Au(III). Langmuir and Freundlich isotherm models were applied to analyze the experimental data, the best interpretation for the experimental data was given by the Langmuir isotherm equation, and the maximum adsorption capacity for Au(III) is 1.700 mmol/g. The adsorption selectivity, the dynamic adsorption and desorption properties of SG-PS-azo-IM for Au(III) have also been studied. The results showed that SG-PS-azo-IM had excellent adsorption for Au(III) in four binary ions system, especially in the systems of Au(III)–Zn(II) and Au(III)–Cu(II), and almost Au(III) could be desorbed with the eluent solution of 0.5% thiourea in 1 mol/L HCl. Moreover, this novel composite material was used to preconcentrate Au(III) before its determination by flame atomic adsorption spectrometry. In the initial concentration range of 0.10–0.20 μg/mL, multiple of enrichment could reach 5.28. Thus, silica gel encapsulated by polystyrene coupling with imidazole (SG-PS-azo-IM) is favorable and useful for the removal of transition metal ions, and the high adsorption capacity makes it a good promising candidate material for Au(III) removal.