| Flocculation sedimentation plays an important role in the field of wastewater treatment.The performance of flocculant is one of the most important factors,affecting the effect of water treatment.Cationic polyacrylamide is a widely used flocculant.Commercial polyacrylamide has some disadvantages,such as low cationic degree and long dissolution time.Facing the increasingly complex problem of water pollution,it is of great significance to develop eco-friendly,efficient and low-cost flocculants.In this paper,the cationic polyacrylamide was synthesized by using free radical polymerization technology according to different technological conditions,and the flocculation effect and antibacterial performance were studied respectively.The main research contents and conclusions of the thesis are as follows:（1）Cationic polyacrylamide（CPAM）was prepared with acrylamide（AM）,2-methacryloyloxyethyl-trimethyl ammonium chloride and dimethyl diallyl ammonium chloride via aqueous solution polymerization,and its properties were studied.The experiment results showed that when the molar ratio of monomers was 6:2:2,the amount of initiator was of 0.3 wt%of the mass of monomers,and,the intrinsic viscosity of CPAM was the highest when the reaction temperature was 70℃,which was 416.14 m L·g-1 and relative molecular weight was 1.39×106g·mol-1.The flocculation experiment showed that the flocculation performance of CPAM under acidic and neutral conditions was better than that under alkaline conditions.When the dosage of CPAM was 20 mg·L-1 under acidic condition,the light transmittance reached 96.36%.The antibacterial experiments indicated that CPAM showed good antibacterial activity against E.coli and S.aureus,and MIC were 35 and 25μg·m L-1,respectively.（2）Cationic polyacrylamide polymers（PAD）were prepared by reverse emulsion polymerization by using AM and 2-acryloxyethyl-trimethyl ammonium chloride（DAC）as raw materials.FT-IR and 1H NMR spectra demonstrated that PAD was successfully synthesized.The optimal reaction conditions for PAD were as follows:HLB of composite emulsifier Span 80-Tween 60 was of 7.51,the molar ratio of AM to DAC was of 6:4,the amount of initiator was of 0.02 wt%of the total mass of monomers,the reaction time was 4 h,and the mass fraction of the monomers was of 35%,under which PAD possessed the highest intrinsic viscosity(1116.32 m L·g-1)and molecular mass(6.05×106 g·mol-1).The flocculation experiments result showed that PAD had better flocculation effect in acidic bentonite suspension,and more PAD dosage was needed to achieve the same flocculation effect in neutral or alkaline environment.The flocculation kinetics indicated that an appropriate amount of PAD was helpful to improve the flocculation effect and enhance the stability of flocs.The flocs were compact and the light transmittance of supernatant reached 98.31%when the dosage of PAD was of 5 mg·L-1.（3）Based on the optimal conditions of reverse phase emulsion polymerization of PAD,pilot experiment was performed with GSH-10 L reactor.The total mass of reaction system was scaled up to 4 kg,and the product was compared with the product of the previous experiments.The method of sectional heating was adopted in polymerization:the jacket temperature T2 was set to 100℃firstly,and then adjusted to 60℃when the temperature in the reactor approached45℃.FT-IR and 1H NMR analysis showed that the product of the pilot experiment was the same as that of the small-scale experiment,both of which was PAD,and the highest intrinsic viscosity was 933 m L·g-1 and the relative molecular mass was 4.61×106 g·mol-1.The dispersibility of the products prepared by the pilot experiment and the small-scale experiment was not different,and the dispersion time spent were 4.68 and 4.21min,respectively.The results of the flocculation experiments showed that the cationic polyacrylamide prepared by the experiment had better flocculation effect than commercial one The highest transmittance of supernatant of PAD prepared was 95.17%when the dosage of PAD was of 6 mg·L-1,while the highest light transmittance of commercial one was 94.96%only when the dosage was of 13 mg·L-1. |
