Study On Synthesis, Characterization And Application Of Cationic Acrylamide Flocculants P(AM-DMC)

With the speeding up of the urbanization and industrialization, the freshwater resources of our country are increasingly tense. To raise the efficiency of wastewater treatment and protect our freshwater resources which we depend upon for survival are extremely urgent. The flocculation is one of the important methods of wastewater treatment. The character and kind of flocculants are key factors which related to the effect of flocculation. Therefore, the study of flocculants is the most important way to achieve the flocculation process optimization. This paper aims to synthesize the anionic and cationic polyacrylamide flocculants with good flocculating performance, and to study the synthetic conditions and flocculating performance.The high molecular weight cationic polyacrylamide flocculants P(AM-DAC) were synthesized by aqueous solution copolymerization using acrylamide(AM) and acryloyloxyethyltrimethyl ammonium chloride(DAC) as monomers. The polymerization was initiated using compound initiator consist of inazo organic initiator Bnd azo organic initiator B. the optimum conditions of polymerization were obtained as follows:The temperature is 30℃, the mass concentration of inazo organic initiator B is 0.15‰, the mass concentration of total initiator A is 0.5‰, the mass concentration of monomers is 30%, the cationic degree is 40%,the mass concentration of solubilizer C is 0.2‰. Under these conditions, The P(AM-DAC) with molecular weight 12 million was synthesized, the mass concentration of residual AM is 1.33%, the dissolution time is 3h. The structure of P(AM-DAC) was proved by IR analysis. P(AM-DAC) could not be decomposed at room temperature proved by DTA-TGA analysis.A analytical method based on ultraviolet spectrophotometry was preliminarily developed for the determination of acrylamide residue in cationic polyacrylamide P(AM-DAC). The standard curve of acrylamide in absolute alcohol and water solution was drawn. The standard curve has good linearrelation, the equation of linear regression at 205nm is as follows: A=0.134 CAM (mg·L-1)+0.025, regression coefficient is 0.9985. The acrylamide residue of P(AM-DAC) which cationic degree is 30%, 40%( solubilizer C was not added),40% (solubilizer C was added) and 50% were determined. The mass concentration of residual AM is 3.15%,1.51%,1.33% and 1.12% respectively.The self-made P(AM-DAC) was used for activated sludge treatment, which is from a certain sewage treatment works of Chongqing. The effect of dosage and cationic degree on sludge dewatering treatment was studied. Considered the sludge dewatering effect and cost, The self-made P(AM-DAC) and four sludge dewatering flocculants used frequently in domestic sewage treatment works were compared. The results of sludge dewatering experiments were obtained as follows: The self-made P(AM-DAC) has high molecular weight and adjustable cationic degree. Good sludge dewatering results were achieved using self-made P(AM-DAC) with 40%~80% cationic degree, the transmittance of filtrate is higher than 92%, the water content ratio of filter cake is lower than 68%. The optimum conditions of flocculation were obtained as follows:the self-made P(AM-DAC) with molecular weight 12 million and cationic degree 40%, the optimum dosage is 1.47kg/t dry sludge. The results Of sludge dewatering contrastive experiments was obtained as follows: The optimum dosage of self-made P(AM-DAC), product 1# from Japan, product 2# from Japan, product from Zhejiang and product from Jiangsu is respectively 1.47kg/t dry sludge, 2.35kg/t dry sludge, 2.94kg/t dry sludge, 2.35kg/t dry sludge and 2.94kg/t dry sludge; The filtrate transmittance is respectively 96.90%, 96.10%, 94.90%, 94.80% and 86.80%; The water ratio of filter cake is respectively 64.50%, 66.63%, 68.18%, 68.50% and 70.5%; The treatment cost is respectively 35.28 yuan/t dry sludge, 88.83 yuan/t dry sludge, 105.84 yuan/t dry sludge, 84.60 yuan/t dry sludge and 94.08 yuan/t dry sludge. Therefore, the sludge dewatering performance of self-made P(AM-DAC) is better than four flocculants used frequently in domestic sewage treatment works.The self-made P(AM-DAC) was used for algae removal treatment, the optimum conditions of flocculation were obtained as follows:the self-made P(AM-DAC) with molecular weight 12 million and cationic degree 40%, the optimum dosage is 3mg/L. Under these conditions, The microphotograph of algae was took, the phenomenon that algae have gathered together to form large floccules was shown. The removal rate of chlorophyll a and turbidity is respectively 99.82%, 96.73%. The algae removal treatment cost is 0.072 yuan/m3.