Adsorption behavior and mechanism for Pb(II) and Cd(II) by silica anchored salicylaldehyde modified polyamidoamine dendrimers

Background: Water pollution caused by Pb(II) and Cd(II) poses severe threat to human beings. Construction of adsorbent for efficient adsorption of these ions is of vital importance. Polyamidoamine (PAMAM) dendrimers based adsorbents displayed excellent binding ability for metal ion. Methods: Silica anchored salicylaldehyde modified polyamidoamine dendrimer (G0-S, G1-S, and G2-S) have been prepared for removing these ions. The adsorption behavior and mechanism was systematically reveled via batch experiments and theoretical calculation. Significant findings: G1-S is the most efficient adsorbent that exhibits highest adsorption at pH 6.0 for these ions. Kinetic adsorption is dominated by film diffusion and fitted by pseudo-second-order model. The adsorption of these ions can be enhanced by elevating temperature and concentration. Adsorption isotherm process fits Langmuir model and is spontaneous, endothermic and randomness increased in nature. Adsorption mechanism indicates imino and tertiary amine nitrogen, hydroxyl and carbonyl oxygen participate in the adsorption, and imino nitrogen atoms dominate the coordination.