Enhancement of textile-dyeing sludge dewaterability using a novel cationic polyacrylamide: role of cationic block structures

Abstract

In this study, a novel cationic polyacrylamide (CPAM) with a microblock structure was successfully synthesized through ultrasonic-initiated template copolymerization (UTP) using allyltrimethylammonium chloride (TM) and acrylamide (AM) as monomers, and sodium polyacrylate (NaPAA) as a template. Fourier transform infrared spectroscopy (FT-IR), ¹H (¹³C) nuclear magnetic resonance spectroscopy (¹H (¹³C) NMR), and thermogravimetric analysis (TGA) were employed to characterize the properties of the polymers. The results showed that the novel cationic microblock structure was formed in the template copolymer of TM and AM (TPTA). Besides, the copolymerization was demonstrated to follow an I zip-up (ZIP) template polymerization mechanism through the analysis of association constant (M_K) and polymerization kinetics. The flocculation results of textile-dyeing sludge dewatering revealed that the polymer with the novel microblock structure showed an excellent flocculation performance. When the optimal conditions at pH of 7.0, dosage of 40 mg L⁻¹ and the intrinsic viscosity of 2.3 dL g⁻¹, the minimum SRF of 4.9 × 10¹² m kg⁻¹ and FCMC of 72.1% were observed. During the flocculation process, the cationic microblocks in TPTA extremely enhanced the ability of charge neutralization and bridging, and contributed much to the excellent flocculation performance in textile-dyeing sludge dewatering.