Preparation of a hydrophobically associated cationic polyacrylamide and its regulation of the sludge dewatering performance.

A hydrophobically associating cationic polyacrylamide (HACPAM) was prepared by using a micellar polymerization method with V-50 (azobisisobutyramidine hydrochloride) as the initiator and acrylamide, acryloyloxyethyl trimethylammonium chloride and butyl methacrylate as substrates under ultraviolet light irradiation. Structural analysis using Fourier transform infrared spectroscopy, proton nuclear magnetic resonance and X-ray photoelectron spectroscopy analyses showed that the substrates were successfully polymerized. HACPAM was used to condition sludge to improve its dewatering performance, and the results showed that as the amount of HACPAM increases, the sludge dewatering performance is significantly improved, and 3.532 kg/t dry solids of HACPAM is regarded as the optimal amount. Compared with the commercially available cationic polyacrylamide (CPAM), HACPAM has a stronger hydrophobic group association effect, with better promotion of the conversion of bound water in sludge flocs into free water, thereby improving the sewage dewatering performance. The 3D spatial structure of dewatered sludge cakes analyzed by computed tomography technology showed that the number of pores of the dewatered sludge cake treated by HACPAM 3 was smaller than that of the cake treated by CPAM, with a reduction in the porosity of 68.8%, resulting in a better hydrophobic effect. In addition, the mechanism of HACPAM improving the dewatering performance is discussed.

Preparation of acrylamide and carboxymethyl cellulose graft copolymers and the effect of molecular weight on the flocculation properties in simulated dyeing wastewater under different pH conditions.

In this study, graft copolymers with different graft ratios (GRs) and molecular weights (MWs) were prepared by water bath polymerization using acrylamide (AM) and carboxymethyl cellulose (CMC) as substrates; additionally, the best preparation parameters were provided. The MW of the copolymer was inversely correlated with the GR (R = -0.82). The obtained graft copolymer was characterized by FTIR, 1H NMR, XPS and DSC. The results showed that CMC and AM were successfully copolymerized and the thermal stability of the product is improved. The graft copolymers with different MWs were used to flocculate a simulated dyeing wastewater at pH values of 3, 5, 7, 9 and 11. The results showed that as the molecular weight of the graft copolymers increased, the average flocculation settling ratio decreased drastically from 61.2% to 19.4% at pH 3, and the higher the MW, the better the flocculation settling performance. But the average settling ratio increased sharply at pH 11, and the increase grew from 21.0% to 50.3%. The larger the MW, the more obvious the decrease in flocculation sedimentation performance. The supernatant turbidity was reduced from 13324 NTU to less than 150 NTU, and the turbidity removal ratio exceeded 99%. The flocculation mechanism was discussed.