Adsorption and desorption behaviors of Pd(II) on silica-gel functionalized with ester- and amino-terminated dendrimer-like polyamidoamine polymers

The dynamic adsorption and desorption properties of ester- and amino-terminated dendrimer-like polyamidoamine (PAMAM) functionalized silica-gels (SiO(2)-G0 similar to SiO(2)-G4.0) for Pd(II) were investigated. The effect of solution acidity on adsorption was studied. The experimental result indicated that the optimum adsorption pH of above-mentioned functionalized silica-gels for Pd(II) was -0.30 when hydrochloric acid was used as medium. Adsorption kinetics suggested that the adsorption was controlled by film diffusion. The adsorption processes Of SiO(2)-GO and SiO(2)-G0.5 followed a pseudo-second-order model, and those of SiO(2)-G1.0 similar to SiO(2)-G4.0 could be described by pseudo-first-order model. The solution of 5% thiourea in 0.2 mol l(-1) HCl was employed as the eluent to assess the reusability of SiO(2)-GO similar to SiO(2)-G4.0. The results showed that ester-terminated products possessed higher desorption percentage than their corresponding amino-terminated ones. Due to the stronger encapsulation effects of interior cavities, the desorption percentages of higher generation products were lower than those of the low generation ones. (C) 2008 Published by Elsevier Ltd.