Study of microwave‐template initiated copolymerization peculiarity and evaluation on the coal floc distinctive behavior and flocculation performance

Abstract

Cationic polyacrylamide (CPAM) contains a large number of acylamino and positively charged methyl ammonium chloride groups. It has the advantages of good water solubility, strong adsorption bridging ability, enhanced charge neutralization and destabilization performance, excellent flocculation effect, and wide application. Therefore, CPAM can be used in the treatment of coal washing wastewater, and the research and development of a new flocculant with high efficiency is a hot topic in this field. Template copolymer (TPADM) of methacryloyloxyethyl trimethyl ammonium chloride (DMC) and acrylamide (AM) was synthesized by microwave‐template initiated polymerization with sodium polyacrylate (PAAS) as template. The microwave‐template initiated polymerization is abbreviated as MW‐TP. By analyzing FTIR, 1H (13C) NMR and TG/DSC of TPADM, it was found that TPADM had obvious cationic fragment structure. In addition, the association constant (KM) and the kinetics of the template reaction showed that the MW‐TP was confirmed to be free radical initiated polymerization and I Zip‐up (ZIP) polymerization mechanism, which demonstrated the formation of the cationic fragment structure again. This new cationic fragment structure greatly enhanced the ability of charge neutralization, electrical patching and adsorption bridging, thus improving the flocculation performance. Compared with cationic P(AM‐DMC) (CPADM), Commercial cationic polypropanamide (CCPAM‐1 and CCPAM‐2), TPADM had better flocculation effect on coal washing wastewater. Under the optimum flocculation conditions (dosage = 16 mg/L, pH = 7.5), suspended solid (SS) concentration and turbidity of coal washing wastewater treated by TPADM reached 14.3 mg/L and 8.7 NTU, respectively. The floc formation, breakage, and regeneration analyses showed that the cationic fragment structure in TPADM could contribute to the formation of large and high density flocculation structure (d50 ≥ 245 μm, Df ≥ 2.05), and these coal flocs can regenerate rapidly after being broken. Finally, these large and compact flocs help to accelerate the flocs sedimentation and reduce the SS concentration and turbidity of coal washing wastewater, and enhance the effect of solid–liquid separation.

Effect of cationic monomer structure on the aggregation behavior of amphoteric acrylic polymer around isoelectric point

“…The chemical shifts of secondary carbon atoms (C j ), tertiary carbon atoms (C k ) and quaternary carbon atoms (C l ) on the polymer backbone were observed at 35-38 ppm, 42-43 ppm and 44-45 ppm, respectively. These results demonstrated that AAPs were successfully synthesized [26]. Among the cationic monomers used for polymerization, DMC, DAC, and DMAEMA are acryloxy-alkyl cationic monomers with ester group in the side chain.…”