给水絮凝处理中壳聚糖的助凝作用和机理

为能高效除浊,又能去除水中有机污染物,将无机絮凝剂聚合氯化铝与天然高分子絮凝剂壳聚糖协同使用,用于自来水厂的给水絮凝处理.考察助凝剂壳聚糖投加量、pH、壳聚糖相对分子质量等因素对浑浊度和有机物去除效果的影响,采用微电泳仪测定了絮凝过程中溶液Zeta电位的变化,通过电子显微镜和im-ageJ图像处理软件,对絮体形态进行分析.结果表明,在以黄河水为水源的自来水厂的给水絮凝处理中,以壳聚糖(CTS)作为聚合氯化铝(PAC)的助凝剂,pH为7.5时,PAC投加35mg/L,CTS投加0.15mg/L时,壳聚糖的助凝效果显著.壳聚糖的絮凝以吸附架桥为主,电性中和为次.显微摄像系统絮体的形态分析表明,单加PAC、PAC/CTS协同絮凝处理水样后絮体的分形维数分别为1.294和1.385.

Effect and mechanism of chitosan coagulation aid in flocculation treatment of water supply

To remove the residual turbidity and organic pollutants in drinking water,the PAC/chitosan coagulation treatment was carried out. The efficiency of coagulation by PAC/chitosan at different chitosan dosages,molecular weights and pH values was investigated. A microelectrophoresis apparatus was used to test the change of Zeta potential and an electron microscope was used to analyze the morphology of flocs. Results of flocculation treatment in a plant taking the surface water of Yellow River as raw water indicate that,efficient coagulation can be obtained by adopting chitosan as coagulation aid of polymeric aluminum chloride (PAC) when pH is 7.5,the addition dosage of PAC is 35 mg/L and that of chitosan is 0.15 mg/L; and the coagulation mechanism is adsorption and inter-particle bridging rather than electrical neutralization. Analysis of flocs morphology shows that fractal dimensions of morphology of PAC and PAC/chitosan are 1.294 and 1.385 respectively.