Starch as one of the most abundant, renewable, low-cost, and biodegradable carbohydrate polymers worldwide suffers from some drawbacks:The most important one is that it lacks properties of synthetic polymers. So, modification of starch by graft copolymerization will provide a substantial modification route to alter physical and chemical properties of starch, thereby increasing its utilization, by attaching a flexible synthetic polymer onto the rigid Correspondence to: Kh. M. Mostafa;

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Propelled starch (PG) was first crosslinked with epichlorohydrin to obtain insoluble crosslinked pregelled starch (CPS). The latter was graft copolymerized with different amounts of Methacrylic acid using potassium persulphate as initiator. This was done to obtain six levels of poly (MAA)-crosslinked pregelled starch graft copolymers (PMCPS) having different graft yields (expressed as meq COOH/100 g starch) with increasing order and designated as (PMCPS 1 to PMCPS 6). The latter copolymers were dispersed in aqueous solution of heavy metal ions (Cu 2þ , Pb 2þ , Cd 2þ , and Hg 2þ ) 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 PMCPS i.e., from PMCPS 1 to PMCPS 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, (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 1N HNO 3 (pH 2) and the metalbinding activity of the starch was slightly reduced by this process. Finally, the ability of PMCPS to remove three types of basic dyes from their solutions was also reported.

Wastewater from textile industries may contain a variety of dyes that have to be removed before their discharge into waterways. For this purpose, pregelled starch (PG) as one of the most abundant biodegradable carbohydrate polymer was first cross linked with epichlorohydrin to obtain insoluble cross-linked pregelled starch (CPS). The latter was graft copolymerized with different amounts of methacrylic acid (MAA) using potassium persulphate as initiator. This was done to obtain six levels of poly(MAA)-cross linked pregelled starch graft copolymers (PMCPS) having different graft yields (expressed as meq COOH/100 g starch) with increasing order and designated as (PMCPS 1 to PMCPS 6). The latter copolymers were used to remove basic dyes namely (safranine T, methylene blue, crystal violet) from their solution and filtered to form polymer-dyes complex. Major factors affecting the dyes removal such as dye concentration, pH, polymer dose, treatment time, agitation speed, and extent of grafting were studied in detail. It was found from the obtained results that; the % dye removal increased by (a) increasing the dye concentration and pH within the range studied; (b) increasing the agitation speed until ! 40 rpm then leveled off thereafter; (c) increasing the polymer dosage from 0.25 to 3.0 g/L then leveled off thereafter; (c) increasing the time of the reaction up to 60 minute then leveled off after that; and (d) increasing the extent of grafting of PMCPS i.e., from PMCPS 1 to PMCPS 6.