Optimal amidoximation conditions of acrylonitrile grafted onto polypropylene by photoirradiation-induced graft polymerization

摘要

To prepare amidoxime (AO) adsorbents for uranium recovery from seawater, the optimum conditions for graft polymerization and amidoximation of acrylonitrile (AN) group and alkaline treatment of the AO group have been investigated in terms of the uranium adsorption capacity. AN has been grafted onto polypropylene (PP) fabric by photoirradiation-induced graft polymerization with benzophenone as the photoinitiator. A concentration of AN ≤1.0M, a photoirradiation time of 2 h, and a reaction temperature of 60°C proved to be optimal for the grafting of AN onto PP. The grafted AN groups were effectively converted into AO groups upon reaction with ≥5.0% (w/v) hydroxylamine solution at pH 7.0-9.0 for ≥16 h at 60-80°C. Although widely used for this purpose, we have shown that methanol is not an essential solvent for the amidoximation reaction. Conditioning of the AO group with KOH solution (alkaline treatment) proved to be effective for enhancing the uranium adsorption capacity of amidoximated PP-g-AN-AO fabric, which increased logarithmically with the conditioning time. The AO group density in the PP-g-AN-AO fabric increased linearly with the degree of AN grafting, whereas the uranium adsorption capacity of PP-g-AN-AO fabric conditioned with KOH reached a maximum at a degree of AN grafting of approximately 60%.