表面活性剂对MnO_2胶体凝聚动力学的影响

Effect of surfactants on MnO_2 colloid aggregation kinetics

为了增加对Mn O2胶体及有关污染物在水处理过程和天然水体中的迁移与归趋的理解,采用时间分辨动态光散射法研究了Mn O2胶体在表面活性剂中的凝聚动力学,考察了表面活性剂对Mn O2胶体凝聚动力学的影响。研究结果表明,无论表面活性剂存在与否,Mn O2胶体在一价与二价金属阳离子溶液中的凝聚规律均符合经典DLVO理论;但表面活性剂的存在,在一定程度上降低了Mn O2胶体的凝聚特性。工业表面活性剂聚乙二醇(PEG)分子量的大小对Mn O2胶体凝聚动力学具有较大影响,随着分子量的增加,阻碍凝聚的能力越强;生物大分子表面活性剂——表面活性素能大幅度降低Mn O2胶体的凝聚特性。通过胶体表面电荷的测定和吸附实验,进一步证实了表面活性剂减慢Mn O2胶体凝聚速率是由于胶体表面吸附层产生的空间位阻作用。这一研究结论对Mn O2胶体的实际工程应用具有重要的理论指导意义。

To understand the transport and fate of MnO2 colloids and related pollutants during water treatment and in natural waters, the aggregation kinetics of MnO2 colloids in the presence of surfactants were investigated using time?resolved dynamic light scattering. The effects of surfactants on MnO2 colloidal aggregation kinetics were also studied. Results show that, regardless of the presence or absence of surfactants, MnO2 colloid aggregation in monovalent and divalent metal cation solution was consistent with classical DLVO theory. However, surfactants hindered the aggre?gation kinetics of the MnO2 colloids. The molecular weight of polyethylene glycol ( PEG) , an industrial surfactant, had a significant impact on MnO2 colloid aggregation kinetics. The impedance grew as the PEG molecular weight in?creased. PEG 6000 hinders MnO2 colloid aggregation more effectively. Surfactin, a biological macromolecular sur?factant, is capable of dramatically reducing the aggregation of MnO2 colloids. By measuring electric charges on the surface of the colloids and through adsorption experiments, it was further verified that the inhibition effects of sur?factants on the velocity of colloid aggregation can be attributed to steric interactions induced by their adsorption lay?ers on the colloid surface. This research has important theoretical significance for the practical engineering applica?tions of MnO2 colloids.