Characterization and sludge dewatering performance evaluation of the photo-initiated cationic flocculant PDD

Abstract

Abstract In this study, a novel flocculant called PDD was synthesized under ultraviolet irradiation using acrylamide (AM), methacryloyloxyethyl trimethylammonium chloride (DMC), and dimethyldiallylammonium chloride (DMDAAC) as monomers. The effects of monomer concentration, cationic degree, cationic monomer ratio, photo-initiation time, photo-initiator concentration, and pH value on the conversion rate and relative molecular mass of PDD were investigated through single-factor and orthogonal experiments. The microstructure of the synthesized product PDD was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetry–differential thermal analysis, and proton nuclear magnetic resonance. The factors that ensure the optimal sludge dewatering performance of PDD obtained under the optimal synthesis conditions were as follows: flocculant dosage = 80 mg/L, pH value = 3, cationic degree = 60%, and relative molecular mass = 9.0 × 106. The solid content of the sludge filter cake, the residual turbidity of the filtrate, and the sludge specific resistance under the optimal synthesis conditions were 31.44%, 11.80 NTU, and 2.11 × 109 m/kg, respectively. Dewatering experimental results showed that PDD had significantly better sludge dewatering efficiency than the commercial flocculants. The main mechanisms for sludge conditioning were adsorption–bridging interaction and electrical neutralization after determining the zeta potential.