Characterization and sludge dewaterability evaluation of a chitosan-based flocculant CMCTS-g-CPAM

In this work, a new cationic flocculant, CMCTS-g-CPAM was synthesized by acrylamide (AM), methacryloyloxyethyltrimethylammonium chloride (DMC) and carboxymethyl chitosan (CMCTS) through UV initiated graft polymerization techniques. The structure of CMCTS-g-CPAM was analysed by infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy (¹H NMR) and X-ray diffraction (XRD) techniques which indicates that AM and DMC are grafted successfully onto CMCTS to obtain CMCTS-g-CPAM. The potential of CMCTS-g-CPAM for the sludge dewatering was investigated. The effects of cationic degree, intrinsic viscosity, dosage and pH on the sludge dewatering performance were studied. The results indicate that the optimal dewatering performance with minimum supernatant turbidity of 5.40 NTU, the moisture content of the filter cake of 79.28% and the specific resistance of the sludge of 1.96 × 10¹³ m/kg was obtained at 30 mg/L CMCTS-g-CPAM at pH 9–10. Finally, from the microscopic and electron micrographs investigation, it was confirmed that the particle size of the CMCTS-g-CPAM treated sludge was significantly large to enhance hydrophobicity and improve dewatering performance.