PAAO cryogels from amidoximated P(acrylic acid-co-acrylonitrile) for the adsorption of lead ion

Lead ion is a common heavy metal pollutant and extremely harmful to human health. Therefore, the research about the adsorption and removal of lead ion from sewage and the development of lead ion sorbents keeps greatly significant. In this study, poly(acrylic acid-co-acrylonitrile) (PAAN) cryogels were prepared by cryo-polymerization. After the treatment with hydroxylamine, the amidoximated PAAO cryogels were applied to remove lead ion from lead-contaminated water. The porous structure and high water permeability of the cryogel could fully facilitate the exposure of active sites to efficiently adsorb lead ion. PAAO cryogels showed a high adsorption capacity of 450 mg/g for lead ion. After the first adsorption–desorption cycle, the adsorption capacity of PAAO cryogels regenerated with alkali solution increased to 650 mg/g and remained in the next six cycles. The pseudo-second-order kinetic model and the intraparticle diffusion model fit the adsorption kinetics of lead ion well, indicating its chemi-sorption feature of PAAO cryogel sorbent. The FTIR and XPS studies suggested that carboxyl group of acrylic acid unit as well as the amidoxime group of modified AN unit contributed the enhanced adsorption ability for lead ion.