Preparation Of Enhanced Flocculation Cationic Polyacrylamide And Related Application

It is the focus of the government and the public to improve the quality of water environment and protect the safety of water environment.The key to achieve the goal of water pollution control depends on the development of water treatment agent and water treatment technology.In the face of the current severe water pollution situation,it also puts forward the rigid requirements for the high performance,safety and environmental protection performance of flocculants.In this paper,under the current situation of severe water pollution and more stringent environmental protection policy,in view of the shortcomings(worse acid/alkali stability,dispersed distribution of the cationic unit in the molecular chain and single processing object)of the existing cationic polyacrylamide flocculants,three kinds of enhanced flocculation cationic polyacrylamide were synthesized.Firstly,P(AM-MAPTAC)(PAMA)with enhanced acid/alkali stability was synthesized taking amide quaternary ammonium salt(MAPTAC)as cationic monomer.Then,based on the good acid / alkali stability of PAMA,Template-P(AM-MAPTAC)(TPAMA)with enhanced flocculation neutralization performance was synthesized by UV induced template polymerization.Finally,based on the research of PAMA and TPAMA,in order to expand the application scope and enhance the flocculation application safety of this kind of CPAM,CTS-g-PAMA with flocculation-bactericidal dual-functional and environmental protection performance was synthesized by introducing chitosan(CTS).Based on the successful synthesis of the three kinds of flocculants,the following aspects were studied in this paper: 1)a series of comparative instrumental characterizations of the synthetic flocculants and commercial CPAM were performed to demonstrate the improvement of the structure of the synthesized polymers;2)the synthetic conditions of flocculants were optimized to obtain the optimum synthetic conditions of the flocculants with the highest intrinsic viscosity;3)the reaction mechanism of the template polymerization was studied to guide and control the reaction in favor of the formation of cationic micro block;4)the flocculation and bactericidal properties of the three kinds of flocculants were studied and compared with that of commercial products to prove the enhancement of actual flocculation and bactericidal performance;5)related application mechanisms of the three flocculants were studied to guide the preparation and application of flocculants.So far,the preparation of amide quaternary ammonium salts cationic flocculants,study on the reaction mechanism of template copolymerization and the preparation of flocculation-bactericidal dual-functional CPAM,related researches are rare or no reported.The main conclusions of this paper are as follows:(1)The results of fourier transforms infrared spectroscopy(FTIR),magnetic resonance spectrometer(1H NMR),scanning electron microscope(SEM)and thermogravimetric/ differential scanning calorimetry(TG/DSC)analyses indicated that AM and MAPTAC were successfully polymerized and the target PAMA were obtained;compared with commercial products(PAM and PDA),the surface of obtained PAMA had a higher degree of irregularity with some pore structure,this surface microstructure would be beneficial to the adsorption and bridging in flocculation process;PAMA had good thermal stability at the conventional application and storage temperature of CPAM;the results of UV analysis showed that PAMA had strong acid/ alkali stability,which proved the correctness of the PAMA molecular design.single factor method and response surface methodology(RSM)were used to investigate the effects of several main synthetic conditions(such as total monomer concentration,monomer molar ratio,initiator concentration,UV irradiation time et al.)on the intrinsic viscosity and conversion of polymers,and the optimum synthesis conditions of PAMA with the highest intrinsic viscosity were obtained.The application results of PAMA in municipal sludge dewatering showed that the adsorption neutralization and bridging net trapping both played an important role in the flocculation process;PAMA had strong acid / alkali stability,and thus had wider pH application range(pH=4~10).(2)FTIR,1H(13C)NMR,SEM and TG/DSC analysis indicated that compared with the non-template polymer PAMA,the rate of cationic micro block junction in the TPAMA molecular chain had been significantly improved,indicating that the template polymerization technology was conducive to the formation of cationic micro block structure;also compared with PAMA,TPAMA exhibited a regular,chain like and porous structure with larger surface area,which would further improve the flocculation performance in flocculation process;TPAMA also had good thermal stability at the conventional application and storage temperature;in order to enhance the adsorption bridging performance of TPAMA,based on the improvement of the cationic micro block ratio of TPAMA,the optimal preparation conditions were optimized by response surface methodology,the optimum synthesis conditions for obtaining the highest intrinsic viscosity TPAMA were obtained.The determination of association constant KM and the results of polymerization kinetics all showed that there was a strong adhesion between the template molecule and the cationic monomer,the reaction was typical ?type template polymerization mechanism;the complex interactions between the monomers and the precipitation of the product during polymerization made the concentration index of total monomer slightly higher than 1.0;the concentration index of initiator was higher than 1.0,which indicated that both single and double ended reactions were present in this reaction.Both the application experimental results of TPAMA in municipal sludge dewatering and dyeing sludge dewatering showed that the enhancement of the adsorption neutralization effect by the high ratio of cationic micro block structure and the enhancement of adsorption bridging by the large specific surface area and porous structure made TPAMA have better flocculation performance than that of PAMA;the small amount of template molecules in the product would affect the flocculation performance of TPAMA to some extent;the results of pH effect experiment again confirmed the excellent acid / alkali stability of amide quaternary ammonium salt CPAM and also showed that this stability did not change with the change of the processing object.(3)FTIR,1H NMR,SEM,TG/DSC,et al.analyses indicated that PAMA was successfully grafted into the CTS molecular chain,and the structure of CTS was not changed,and thus UV initiated polymerization was suitable for CTS modification;after grafting PAMA,not only the water solubility of CTS was improved significantly,but also its surface structure had changed dramatically,the surface showed different layers of folds,and distributed different sizes of holes,overall fluffy,and thus had larger specific surface area;CTS-g-PAMA also had good thermal stability at the conventional application and storage temperature.The results of flocculation and sterilization experiments of CTS-g-PAMA in kaolin suspension or Escherichia coli suspension showed that CTS-g-PAMA had excellent flocculation and sterilization performance;the excessive CTS-g-PAMA was involved in the sterilization of Escherichia coli,which avoided the typical phenomenon of "re stabilization deterioration" in flocculation.Both the beta galactosidase activity assay test and the three dimensional fluorescence analysis showed that CTS-g-PAMA had bactericidal effect on Escherichia coli and not only antibacterial activity.