Preparation of PAMAM dendrimer modified amidoxime chelating resin and its adsorption for U(VI) in aqueous

Uranium adsorption materials need to consider both adsorption capacity and selectivity. Based on the high adsorption capacity of polyamidoamine (PAMAM) dendrimer and the high selectivity of amidoximated (AO) resin for U(VI), a novel PAMAM modifed AO chelating resin (PS-PAMAM-AO) was prepared and used for U(VI) adsorption in aqueous. For comparison, a common AO resin (PS-AO) was prepared based on ammoniated poly (styrene-co-divinylbenzene) bead (PS-NH2). The synthesized resins were characterized by Fourier transform infrared spectra (FT-IR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The factors affecting adsorption such as solution pH and temperature, contact time and initial U(VI) concentration were investigated. PS-PAMAM-AO had the largest adsorption capacity (167.8 mg/g, at pH 5.0 and 313 K with initial U(VI) concentration 300 mg/L) compared with its precursor (PS-NH2 and PS-PAMAM) and PS-AO. Kinetic and thermodynamic studies showed its U(VI) adsorption was a chemical and rate-limiting process and conformed to the Langmuir isothermal model. The adsorbed U(VI) can be desorbed with 10 % NaCl + 1 mol/L HCl, and the desorption rate reached 94.1 %. When the concentration of coexisting NaCl increased from 0.0 to 1.0 mol/l, the U(VI) adsorption capacity of PS-PAMAM-AO decreased to 69.9 %, similar to that of PS-AO (77.4 %), PAMAM modification did not significantly affect the adsorption selectivity of amidoximated resin.