Preparation of poly (DMAEM)-cross linked pregelled starch graft copolymer and its application in waste water treatments

Pregelled starch (PS) was first cross linked with epichlorohydrin (ECH) to obtain insoluble cross-linked pregelled starch (CPS). The latter was graft co-polymerized with different amounts of dimethylaminoethyl methacrylate (DMAEM) using potassium permanganate/sulphuric acid redox system. This was done to obtain six levels of poly (DMAEM)-cross linked pregelled starch graft copolymers (PDMAEMCPS) having different graft yields (expressed as N%) with increasing order and designated as (PDMAEMCPS 1 to PDMAEMCPS 6). The latter copolymers were dispersed in aqueous solution of heavy metal ions Cu (II) ions and filtered to form polymer–metal ions complex. Different factors affecting the heavy metal ions removal such as pH, extent of grafting, treatment time and starch dose were studied in detail. It was found from the obtained results that; the residual metal ions removal from their aqueous solutions increased with (a) increasing the extent of grafting of PDMAEMCPS i.e. from PDMAEMCPS 1 to PDMAEMCPS 6; (b) increasing the pH of the metal ions solution complex from 1 to 8; (c) increasing the starch dosage from 0.25 to 2.0% (w/v), then leveled off thereafter and (d) increasing the time of the reaction up to 20 min then leveled off after that. On the other hand, Pb, Cd and Hg ions were also removed from their solutions with different extent. Furthermore, the prepared copolymer could be recovered by washing the metal ions from the complex with weak acid 1 N HNO3 (pH 2) and the metal-binding activity of the starch was slightly reduced by this process. Finally, the ability of PDMAEMCPS to remove three types of acid dyes from their solutions was also reported.