title: UV-initiated template copolymerization of AM and MAPTAC: Microblock structure, copolymerization mechanism, and flocculation performance.
abstract: Flocculation as the core technology of sludge pretreatment can improve the dewatering performance of sludge that enables to reduce the cost of sludge transportation and the subsequent disposal costs. Therefore, synthesis of high-efficiency and economic flocculant is remarkably desired in this field. This study presents a cationic polyacrylamide (CPAM) flocculant with microblock structure synthesized through ultraviolet (UV)-initiated template copolymerization by using acrylamide (AM) and methacrylamido propyl trimethyl ammonium chloride (MAPTAC) as monomers, sodium polyacrylate (PAAS) as template, and 2,2'-azobis [2-(2-imidazolin-2-yl) propane] dihydrochloride (VA-044) as photoinitiator. The microblock structure of the CPAM was observed through nuclear magnetic resonance (1H NMR and13C NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) analyses. Furthermore, thermogravimetric/differential scanning calorimetry (TG/DSC) analysis was used to evaluate its thermal decomposition property. The copolymerization mechanism was investigated through the determination of the binding constant MKand study on polymerization kinetics. Results showed that the copolymerization was conducted in accordance with the I (ZIP) template polymerization mechanism, and revealed the coexistence of bimolecular termination free-radical reaction and mono-radical termination in the polymerization process. Results of sludge dewatering tests indicated the superior flocculation performance of microblock flocculant than random distributed CPAM. The residual turbidity, filter cake moisture content, and specific resistance to filtration reached 9.37 NTU, 68.01%, and 6.24 (1012m kg-1), respectively, at 40 mg L-1of template poly(AM-MAPTAC) and pH 6.0. Furthermore, all flocculant except commercial CPAM showed a wide scope of pH application.
authors.affiliation: Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment, State Ministry of Education, Chongqing University, Chongqing 400045, China; National Centre for International Research of Low-carbon and Green Buildings, Chongqing University, Chongqing 400045, China.
authors.forename: Xiang
authors.initials: X
authors.lastname: Li
authors.affiliation: Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment, State Ministry of Education, Chongqing University, Chongqing 400045, China; National Centre for International Research of Low-carbon and Green Buildings, Chongqing University, Chongqing 400045, China. Electronic address: zhl@cqu.edu.cn.
authors.forename: Huaili
authors.initials: H
authors.lastname: Zheng
authors.affiliation: Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Jinan 250100, China.
authors.forename: Baoyu
authors.initials: B
authors.lastname: Gao
authors.affiliation: Jiangsu Key Laboratory of Industrial Water-Conservation & Emission Reduction, College of Urban Construction, Nanjing Tech University, Nanjing 211800, China.
authors.forename: Yongjun
authors.initials: Y
authors.lastname: Sun
authors.affiliation: Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment, State Ministry of Education, Chongqing University, Chongqing 400045, China; National Centre for International Research of Low-carbon and Green Buildings, Chongqing University, Chongqing 400045, China.
authors.forename: Bingzhi
authors.initials: B
authors.lastname: Liu
authors.affiliation: Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment, State Ministry of Education, Chongqing University, Chongqing 400045, China; National Centre for International Research of Low-carbon and Green Buildings, Chongqing University, Chongqing 400045, China.
authors.forename: Chuanliang
authors.initials: C
authors.lastname: Zhao
mesh_terms: D020106:Acrylamide / Q000737:chemistry*; D000180:Acrylic Resins / Q000737:chemistry*; D000643:Ammonium Chloride / Q000737:chemistry*; D005374:Filtration; D005427:Flocculation; D008689:Methacrylates / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D058105:Polymerization; D012722:Sewage / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D014466:Ultraviolet Rays; D014865:Waste Disposal, Fluid / Q000379:methods; D000099166:Polyacrylamides
chemical_list: D020106:Acrylamide; D000180:Acrylic Resins; D000643:Ammonium Chloride; D008689:Methacrylates; D012722:Sewage; D000099166:Polyacrylamides; C006903:carbopol 940; C400723:MAPTAC
keywords: Cationic polyacrylamide; Copolymerization mechanism; Microblock structure; Polymer flocculant; Sludge dewatering