Synthesis of starch-g-p(DMDAAC) using HRP initiation and the correlation of its structure and sludge dewaterability

A new cationic starch used as a sludge dewatering agent was prepared by grafting copolymerization of degradation starch and dimethyldiallylammonium chloride (DMDAAC) using horseradish peroxidase/H2O2 initiation. Its chemical structure was characterized by FTIR, 1H NMR, 13C NMR, gel permeation chromatography, graft percent, and graft efficiency. The results indicated that its structure was built by grafting the DMDAAC oligomer onto the starch backbone as branched chains, with stronger hydrophobic regions and higher cationic degree. The specific resistance of the filtration and capillary suction time of the sludge conditioned with the cationic starch decreased distinctly, and the sludge water content could be reduced to 50.6% from 97.85%. The dewatering mechanism is proposed based on the surface tension, zeta potential, and microstructure of sludge, which involves stronger hydrophobic regions and cationic groups producing a porous structure within the sludge. The research results may provide valuable ideas for developing high-performance sludge dewatering agents.