Synthesis and characterization of a dewatering reagent: cationic polyacrylamide (P(AM–DMC–DAC)) for activated sludge dewatering treatment

Abstract

ABSTRACT P(AM–DMC–DAC), one kind of ternary copolymerized cationic polyacrylamide, was synthesized using acrylamide (AM), methacryloxyethyltrimethyl ammonium chloride (DMC), and acryloxyethyltrimethyl ammonium chloride (DAC) by photopolymerization technique. The copolymer was characterized by means of Fourier transform infrared spectroscopy, thermal gravimetric analysis, and scanning electron microscopy. The optimum synthesis conditions were as follows: mass percentage of photoinitiator being 0.40%, mass percentage of solubilizer being 0.10%, inducing time being 1 h, pH value being 9.0, and mass ratio of AM/DMC/DAC being 4:3:3. At optimum conditions, the performance parameters of copolymer are as follows: thermal stability was 126.0 J g−1, molecular weight was 1.28 × 107, cationic degree was 30.7%, coagulant dosage being 0.5 g kg−1, and the filter cake moisture content (CMC) and filtrate residual turbidity were 65.7% and 3.73 NTU, respectively. Based on the evaluation of the sludge dewatering process, it was found that when the coagulant dosage was 1 g kg−1, activated sludge initial pH value was 7.0, and rapid agitation speed was 120 rpm, CMC and turbidity were 63.5% and 2.95 NTU, respectively. In addition, charge neutralization and adsorption/bridging coagulation–flocculation mechanisms played an important role in sludge dewatering performance.