Star type polymer grafted and polyamidoxime modified silica coated-magnetic particles for adsorption of U(VI) ions from solution

Abstract

Polyamidoxime groups functionalized magnetic adsorbent was prepared by sequential grafting of SiO2, poly(glycidylmethacrylate) p(GMA), and diaminomelanonitrile (DAMN) on the Fe3O4 nanoparticles (MP). Firstly, the MP was synthesized by thermal co-precipitation reaction and then grafted with 3-aminopropyltriethoxysilane (APTES) to obtain amine group ended silica layer (i.e., MP/SiO2-NH2). For grafting of star type fibril polymer, atom transfer radical polymerization (ATRP) initiator was attached on the MP/SiO2-NH2 to obtain Br-ended MP/SiO2-NH-Br. Then, DAMN ligand was immobilized on the MP/SiO2/p(GMA) via epoxy ring opening reaction. The nitrile group of the DAMN ligand was converted in to amidoxime group (AO) by the reaction with hydroxylamine. The MP/SiO2/p(GMA)-AO nanoparticles were characterized by analytical methods, ATR-FTIR, SEM, X-ray diffraction (XRD), differential thermal analysis (DTA), and BET surface area analyzer. The maximum adsorption capacities as prepared adsorbents (i.e., MP, MP/SiO2-NH2, MP/SiO2/p(GMA)-OH, MP/SiO2/p(GMA)-DAMN and MP/SiO2/p(GMA)-AO for U(VI) ions were determined. The maximum adsorption pH was 6.0 for MP/SiO2/p(GMA)-AO, and the maximum amount adsorbed U(VI) ions was 760.3 mg g−1. The equilibrium time was 30 min, and the experimental data was described with the Langmuir and Temkin models. The second-order kinetic best fitted the experimental data. The MP/SiO2/p(GMA)-AO showed good reusability for ten cycles of adsorption–desorption with negligible changes in the adsorption performance and stability. The selectivity of the MP/SiO2/p(GMA)-AO was also tested using artificial water after spiking with various amount of U(VI) ions. The experimental result indicated that MP/SiO2/p(GMA)-AO has high selectivity for U(VI) ions in the presence of other metals.