利用FBRM研究阳离子聚丙烯酰胺对高岭土的动态絮凝过程

Study on the Dynamic Flocculation Process of Kaolin Suspensions Induced by Cationic Polyacrylamide by Using FBRM

关键词:  絮凝剂  FBRM  絮体结构  分形维数  絮凝动力学

Key Words:flocculant  FBRM  floc structure  fractal dimension  flocculation kinetics

摘要:利用聚焦光束反射测量仪（FBRM）研究了阳离子聚丙烯酰胺（CPAM）对高岭土颗粒体系的动态絮凝过程，结合浊度仪、激光衍射粒度仪、显微摄像等表征手段，探讨了絮凝剂用量对絮凝性能和絮体结构的影响。同时基于分形理论对絮凝过程中絮体分形维数的变化进行了考察，基于Smoluchowski模型研究了CPAM作用下高岭土粒子的絮凝动力学。结果表明，随着药品用量的增加，体系中粒子的平均弦长和粒径逐渐增大，体系达到稳定的时间延长，浊度不断下降。在絮凝过程中，随着作用时间的延长，絮体结构发生变化，分形维数增加，形成相对致密的絮体。增加絮凝剂的用量，絮凝作用增强，絮体尺寸变大，絮凝速率较快，需较长的絮凝反应时间才能达到平衡。

Abstract:A real-time methodology has been developed to study the flocculation behavior of kaolin suspensions induced by cationic polymer, by using the focused beam reflectance measurement (FBRM) system. The turbidity, laser diffraction particle size analyzer and light microscopy were used to characterize the properties and morphology of the flocs. The fractal dimension was investigated during the flocculation process based on the fractal theory. Furthermore, the results were analyzed using a model of the flocculation kinetics, based on the Smoluchowski model. Detailed investigations showed that the morphology (size and structure) of the flocs, the turbidity of the supernatant, and the flocculation rates of particle numbers were highly dependent on the CPAM dosage. Records and analysis of FBRM indicated that the mean chord length of the particles increased with CPAM dosage, which was corroborated by laser diffraction particle size analyzer and turbidity decreased. As the extension of time, the floc structure changed during the flocculation process whilst fractal dimension increased, forming relatively tighter and compact structures. The different floc morphology under different CPAM dosages was shown more obviously by the photomicrography. During flocculation, the higher the flocculation rate of particle numbers, the better the flocculation efficiency will be, but it still need more time to reach the equilibrium state.