Characterization and Evaluation of Dewatering Properties of PADB, a Highly Efficient Cationic Flocculant

PADB was a highly efficient cationic flocculant, which was synthesized through the copolymerization of acrylamide (AM), acryloyloxyethyl trimethyl ammonium chloride (DAC), and butylacrylate (BA) with ultraviolet initiation by micellar polymerization technology. The PADB was the terpolymer of AM, DAC, and BA. In order to observe this flocculant’s structural characteristics, nuclear magnetic resonance hydrogen spectroscopy (1H NMR), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA) were used. The most important study was to analyze its physicochemical parameters during dewatering of activated sludge. These tested parameters included residual turbidity of supernatant, dry solid content (DS), extracellular polymeric substances (EPS), specific resistance to filtration (SRF), ζ-potential, floc size, and settling rate. Results demonstrated that the PADB have a superiority over both poly(acrylamide-acryloyloxyethyl trimethyl ammonium chloride) (PAD) and commercially available cationic polyacrylamide (CPAM). However, it was dependent on pH and dosage. A favorable pH was in the neutral range while the appropriate dosage (20 mg·L–1-60 mg·L–1) was crucial to the conditioning process. For the PADB at40 mg·L–1 and pH at 7, the residual turbidity of supernatant, DS, SRF, and settling rate could reach 5.5 NTU, 32.2%, 5.51 × 1012 m·kg–1, and 3.318 cm·min–1, respectively. During the sludge flocculation process, the charge neutralization mechanism and bridging flocculation played an important role in floc’s formation and settlement.