Adsorption behavior of PAMAM dendrimers functionalized silica for Cd(II) from aqueous solution: Experimental and theoretical calculation

Abstract

Abstract The adsorption behavior of polyamidoamine (PAMAM) dendrimers functionalized silica (SG-G0∼SG-G4.0) for Cd(II) from aqueous solution was investigated by combining experimental and theoretical method. The influences of dendrimer generation, terminal functional group, solution pH, contact time, temperature, as well as the initial concentration of Cd(II) on the adsorption behavior were explored. Static adsorption indicates that the adsorption capacity increases first and then decreases with the increase of dendrimer generation, SG-G2.0 and SG-G2.5 possess the highest adsorption capacity for amino- and ester-terminated PAMAM functionalized silica, respectively. The optimal adsorption pH value is 6 for all the adsorbents. Kinetic adsorption implicates that the adsorption can approach equilibrium at about 200 min. The kinetic adsorption follows pseudo-second-order kinetic model and is dominated by film diffusion. The isotherm adsorption demonstrates that the adsorption favors high concentration and the adsorption capacity first increases and then decreases with the increase of temperature. Adsorption isotherm process can be well described by Langmuir model. FTIR technique and DFT calculation reveal that the involvement primary and secondary nitrogen atoms, as well as carbonyl oxygen atoms dominate the adsorption. As SG-G0∼SG-G4.0 displays excellent adsorption performance for Cd(II), they could be potentially used as effective adsorbents for the decontamination of aqueous Cd(II).