Abstract
A series of amine-terminated polyamidoamine (PAMAM) dendrimer/silica gel hybrids (SiO2-G1.0, SiO2-G2.0 and SiO2-G3.0) were synthesized and used for the adsorption of Fe(III) and Ag(I) from N,N‑dimethylformamide. The effects of time, temperature, initial metal ion concentration, and adsorbent dosage on the adsorption were determined. Results show that the adsorption capacity for both Fe(III) and Ag(I) followed the order of SiO2-G2.0 > SiO2-G1.0 > SiO2-G3.0. Adsorption kinetic shows that the adsorption process follows the pseudo-second-order kinetic model and is controlled by film diffusion process. Isotherm adsorption indicates the adsorption favors high temperature and metal ion concentration. The isotherm adsorption can be fitted well by Langmuir model and carries out by monolayer adsorption behavior. The calculated mean free energy E suggests the adsorption proceeds by chemical mechanism. The removal rate increases and adsorption capacity decreases with the increase of adsorbent dosage. DFT calculation demonstrates the formation of tetra- and penta-dentate chelates with the involvement of primary amine N, secondary amine N, carbonyl O atoms dominate the coordination of G1.0 with Ag(I).
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