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Controlling the concentration of free radicals in polymerization systems is advantageous for preparing cationic polyacrylamide (CPAM) with a high molecular weight and acceptable dissolvability. In this study, a novel ultraviolet (UVA)-initiated system characterized by an adjustable light intensity and a redox-azo complex initiator was used to synthesize a CPAM flocculant named NP. Comparatively, another CPAM flocculant named SP with a stable UVA light intensity and a single initiator was prepared. Their chemical structure, morphology, and thermal stability were analyzed through instrumental analysis. 1H NMR indicated that NP was successfully prepared, and a small fraction of a cationic homopolymer was mixed in the product. Polymerization conditions of NP were optimized, and polymerization mechanism was determined by investigating the effects of various parameters on intrinsic viscosity, conversion, and dissolvability. Results showed that the best performance was obtained at indices of 0.45 wt‰ redox initiator concentration, 0.2 wt‰ azo initiator concentration, 40.0 wt% cationic monomer, 3 wt‰ urea, and first- and second-stage light intensities of 8.5 and 13 mW/cm2, respectively. The sludge conditioning performances of NP and SP were comparatively evaluated, and the mechanism was determined by examining sedimentation behavior and floc size distribution. High intrinsic viscosity, porous morphology structure, and mixed NP cationic homopolymer contributed to the improvement of sludge conditioning performance.

Preparation, Characterization, and Sludge Conditioning of Cationic Polyacrylamide Synthesized by a Novel UVA-Initiated System