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 (SiO2-G0 ∼ SiO2-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 SiO2-G0 and SiO2-G0.5 followed a pseudo-second-order model, and those of SiO2-G1.0 ∼ SiO2-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 SiO2-G0 ∼ SiO2-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.