利用小角度激光光散射研究阳离子有机高分子絮凝剂的絮体粒径和絮体结构

Study on the floc size and structure of cationic organic polymers by using small-angle laser light scattering

利用小角度激光光散射在线监测技术研究了不同阳离子有机高分子絮凝剂对带负电荷的高岭土颗粒体系的絮凝动力学和絮体结构.对于高电荷密度的聚二甲基二烯丙基氯化铵(PDADMAC),由于分子量低其初始絮凝反应速度较慢,最终形成的絮体也较小.絮凝过程中,其絮体结构发生重组和排列,分形维数从1.83升高到2.09,所形成的絮体密实.对于低电荷密度的2种阳离子聚丙烯酰胺(CPAM),因其分子量大投药量高,絮凝反应速度较快;但其絮体的分形维数较小且在絮凝反应中基本保持不变,形成的絮体结构开放和松散.基于有机高分子对高岭土体系浊度和zeta电位的影响,结合絮凝动力学和絮体结构分析,结果表明,PDADMAC絮凝机理是电中和作用,而随着分子量的增加和电荷密度的降低,CPAM则主要通过吸附架桥作用产生絮凝.

The flocculation kinetics and floc structure of kaolin particles induced by cationic polymers were studied by small-angle laser light scattering （SALLS）. For the high charge density flocculant polydiaUyldimethylammonium chloride （PDADMAC）, the initial flocculation rates are slow due to its low molecular weight. Restructuring of the flocs occurs in the flocculation process, forming smaller and more compact flocs while the fractal dimension increases from 1.83 to 2.09. For the low charge density cationic polyacrylamides （ PAM ）, which are high molecular weight polymers, the initial flocculation rates are much higher due to their high dosage and molecular weights. High adsorption potentials prevent the particles from entering the interior of the floc structure, which results in a more open floc structure and a lower fractal dimension. Together with the residual turbidity and zeta potential induced by these two types of cationic polymers, the results show that the flocculation mechanism is mainly charge neutralization for the low molecular weight and high charge density polymer PDADMAC, while polymer bridging is suggested to be the dominant mechanism for the high molecular weight polyelectrolyte PAM.