高分子絮凝剂质量浓度对泥沙絮体分形结构的影响

The Effect of Concentration of High Molecular Weight Flocculantson Fractal Structures of Bridging Flocculated Aggregates for Sediments

在黄河泥沙高质量浓度悬浊液中投加阳离子高分子聚合物,采用沉降技术与图像分析技术,探讨了聚合物的架桥絮凝机理以及不同质量浓度聚合物下架桥絮体粒径发展变化趋势,利用分形特性表征参数“分维”定量分析了不同质量浓度对絮体分形结构的影响,得出:①阳离子聚合物对泥沙颗粒的絮凝作用以架桥絮凝机理为主,电性中和机理为辅;②不同高分子质量浓度下泥沙架桥絮体粒径分布均呈广义的正态分布,不同絮凝阶段絮体存在3个粒径分布区域;③高分子质量浓度存在一个最佳值.合适浓度下的高分子架桥絮体结构密实、沉速快,静沉实验中上清液余浊低,分维值高,絮凝效果好.

By adding high molecular weight flocculants intohigh turbid concentration suspensions with Yellow- River sediments, and by using settling technique and image analysis technology. The paper discusses bridging flocculation mechanism and development trends of aggregate sizes under different concentration of high molecular weight polymer. Meanwhile, the effects of various concentrations on fractal structure of the sediments aggregates are analyzed, quantitatively, by using the parameter ＂fractal dimension＂ characterizing fractal properties. Conclusions are drawn as follows： ①Bridging flocculation mechanism is dominant and charge neutralization mechanism is secondary for flocculation functions of cationic polymers to sediments particles; ②Sizes distributions of bridging flocculated silts aggregates present generalized normal distribution under different concentrations of the polymer. There are three regions for sizes distributions of silts aggregates at different flocculation stages ; ③There is an optimum value about the concentration of a high molecular weight polymer. Under the proper concentration, flocculation efficiencies are ideal： the structures of bridging flocculated aggregates are compact, their settling velocities are great, the residual turbidity of the supernatant is low under the quiescent settling experiment and the fractal dimension value is high.