Evaluation of some starch derivatives containing amide groups as flocculants

Three types of starch derivatives namely poly(acrylamide)-starch graft copo lymer, carbamoylethylated starch, and starch carbamate were prepared and ev aluated as flocculants. Native and hydrolyzed maize starches were used as p arent materials for these derivatives. The flocculation was followed by mon itoring transmission % and weight removal %. The different factors affectin g flocculation were studied. These factors include: (a) flocculant dose, (b ) pH of the flocculation medium and (c) starch derivatives type, molar mass and nitrogen content. The flocculation efficiency of the three starch deri vatives follows the order: poly(acrylamide)-starch graft copolymer > carbam oylethylated starch > starch carbamate. The flocculation efficiency increas es on increasing the nitrogen content and/or decreasing the molar mass of t he flocculant. The flocculation efficiency of various flocculants at pH 6 i s higher than at pH 8. The poly(acrylamide)-starch graft copolymer based on H-3-starch has a higher flocculation efficiency than polyacrylamide.