Adsorption properties of amidoxime resins for separation of metal ions from aqueous systems

In this study, the acrylonitrile (AN)-divinylbenzene (DVB)-methylacrylate (MA) resin was synthesized via suspension polymerization in the presence of toluene as diluent, and benzoylperoxide (BPO) as initiator. The effects of MA as a hydrophilic agent and toluene as a diluent on the anion and cation exchange capacity of the synthesized amidoxime resins were investigated before and after alkaline treatment. The results showed that the anion exchange capacity decreased with an increase in the amount of MA while alkaline treatment had no significant effect. Also, the cation exchange capacity increased with an increase in the amount of hydrophilic agent and reached a maximum point. The sorption equilibrium was achieved relatively fast within 40 min, and the resin exhibited affinity towards lead (II), copper (II) and in particular U(VI), and the order of adsorption affinity were UO22+ > Pb2+ ≫ Co2+ > Cu2+ ≫ Cd2+. The adsorption of uranium was directly depended up on the pH value. Furthermore, the macroreticular chelating resin, containing amidoxime group had higher adsorption of uranium (VI) than other metal ions studied. Finally, the alkaline treatment enhanced the potential for much faster adsorption and the highly porous chelating resin provided a more favorable pore structure for the rapid rate of diffusion of metal ions.