Ultraviolet-initiated Synthesis Of P(AM-DAC-BA) And Its Sludge Dewatering Properties

With development of industry, urbanization, and emphasis and improvement ofenvironmental protection and environmental requirements by environmental protectiondepartment, water treatment had made great progress. But consequently large amountsof excess sludge were generated in the in the sewage treatment process, more and moreconcern and attention had been drawn. Flocculation was an important treatment step andcore foundation for sludge dewatering, and could improve sludge dewateringperformance, reduce the moisture content of the sludge, and decrease transportationcosts. Therefore, the research and development of efficient, economical flocculants hadimportant theoretical significance and economic value. In this paper, the novel andefficient cationic polyacrylamide sludge dewatering agents were synthesized accordingto the problems above.Due to cationic polyacrylamide with a positively charged cationic group and highmolecular weight, Cationic polyacrylamides (CPAMs) had a strong ability of chargeneutralization and adsorption bridging effect, so that the negatively charged colloidparticles could be destabilized, aggregated, and precipitated. CPAMs were widely usedin the treatment of industrial wastewater, sludge dewatering and other fields. But in thesludge dewatering areas, due to the current commercially available cationicpolyacrylamides had poor solubility, high residual monomer content, the complexprocesses of production technology, long polymerization time, high costs, and othershortcomings. It was largely related to the current initiation technologies. Meanwhilethere were many studies about sludge dewatering applications, few researches on sludgeflocculation and sludge dewatering mechanism were reported. This paper focuses on thestudy of UV-initiated polymerization system, highly efficient and novel cationicpolyacrylamides with short polymerization time and dissolve time, high intrinsicviscosity, and less residual acrylamide monomer were synthesized. Through the sludgedewatering experiments of dye sludge, municipal activated sludge, and alum sludge,sludge flocculation mechanism was further investigated. The research findings in thispaper contributed to the improvement of practical engineering applications with certainguidance.The main contents in this research are as follows:①synthsis of P(AM-DAC-BA) A new cationic flocculant P(AM-DAC-BA) was synthesized by thecopolymerization of acrylamide (AM), acryloyloxyethyltrimethyl ammonium chloride(DAC), and butylacrylate (BA) under ultraviolet (UV) radiation with2,2’-azobis(2-methylpropionamide) dihydrochloride (V-50) as photo-initiator.Parameters affecting the intrinsic viscosity ([η]) and conversion of P(AM-DAC-BA),such as monomer concentration, photo-initiator concentration, pH, illumination time,and incident light intensity in a quartz and glass reactor were examined. Meanwhile thesynthesis process of P(AM-DAC-BA) optimize by using response surface methodology(RSM).②characterization of P(AM-DAC-BA)First, UV spectra of the monomers AM, DAC, BA, and P (AM-DAC-BA) wasanalyzed. The functional structure, surface morphological structure, and thermalstability of P(AM-DAC-BA) in quarts reactor and glass reactor were studied andcompared by Nuclear Magnetic Resonance Hydrogen Spectroscopy (1H NMR),Scanning Electron Microscope (SEM), and Thermal Gravimetric Analysis (TGA). Thepossible formation condition of the surface porous structure of P(AM-DAC-BA) wasobtained by comparative analysis. Finally, Through the V-50UV absorptionspectroscopy, as well as chain initiator, chain transfer, chain termination, and chaintransfer process, possible UV initiated polymerization process and polymerizationmechanism was discussed. This effort made a useful contribution to further optimize thesynthesis of high-performance P (AM-DAC-BA).③infrared spectroscopy of P(AM-DAC-BA)Cationic Polyacrylamides P(AM-DAC-BA) synthesized in the quartz reactor andglass reactor were characterized by infrared spectroscopy. Attributions of typicalinfrared vibrational frequencies were analyzed by comparing with infrared spectroscopyof the monomers and P(AM-DAC-BA). The groups of-CONH2、-COOCH2(C=O)、-COOCH2-(C-O-C)、-CH2-N(CH3)3group in AM, DAC, BA were selected ascharacteristic absorption peaks for studying. The effect of synthesis condition on theposition of characteristic peaks and the peak area were discussed.④Application of P(AM-DAC-BA) in sludge dewateringThe dewatering performance of textile sewage sludge by P(AM-DAC-BA) wasevaluated through the investigation of dosage and pH. The difference of dewateringperformance by P(AM-DAC-BA) synthesized in the quartz reactor and glass reactorwas analyzes and compared. The municipal activated sludge from municipal wastewater treatment plant wasadopted as research object. The optimum conditioning process of the waste sludge byP(AM-DAC-BA) was obtained. The dewatering abilities of waste sludge treated byvarious flocculants, including P(AM-DAC-BA), P(AM-DAC), and commerciallyavailable CPAM, were compared. The understanding of sludge flocculation mechanismwas also improved by investigating flocs size and zeta potential.The dewatering performance of alum sludge from a drinking-water treatment plantwas investigated in this study. The optimal sludge dewatering condition was achievedthrough the optimization of flocculation process. The mechanism of improvement ofalum sludge dewatering performance was investigated by fractal dimension, floc size,and zeta potential analysis at different flocculation condition. The correlation betweenfractal dimension and floc size (floc size and zeta potential) after flocculation wasanalyzed, which provided new idea and method for discussing the main mechanism offlocculation.Finally, through the comparison of dewatering performance with P(AM-DAC) andthe commercially available CPAM, and P(AM-DAC-BA) cost analysis, P(AM-DAC-BA) environmental and economic benefits were discussed.