Aggregation and charging of colloidal silica particles: Effect of particle size
Aggregation and charging of colloidal silica particles: Effect of particle size
复制标题
DOI：
10.1021/la046829z
复制
发表时间：
2005-06-21
期刊：
影响因子：
3.9
通讯作者：
Borkovec, M
中科院分区：
文献类型：
--
作者：
Kobayashi, M;Juillerat, F;Borkovec, M
我们通过电位滴定、电泳迁移率和时间分辨光散射系统地研究了特征明确的无定形二氧化硅颗粒的水悬浮液。对于直径约为30、50和80纳米的三种颗粒，我们测量了它们的带电行为和聚集速率常数随KCl电解质中pH值和离子强度的变化。带电行为与基本的斯特恩模型一致；二氧化硅颗粒带负电荷，其电荷量随pH值和离子强度的增加而逐渐增大。另一方面，它们的早期聚集（或凝聚）行为是复杂的。最大颗粒的聚集呈现出类似于德亚金、朗道、维韦和奥弗贝克（DLVO）理论预测的特征。一方面，在低离子强度下，速率常数随pH值的增加而急剧下降，在高离子强度下达到快速聚集条件。另一方面，我们观察到在低pH值和高离子强度下聚集有明显的减缓特征。对于中等颗粒和小颗粒，这一特征非常显著，导致小颗粒在低pH值下完全稳定。在较高pH值下，中等颗粒和小颗粒也观察到稳定现象。从这些聚集测量结果中，我们推断存在一种额外的排斥力。通过假设颗粒表面存在由聚硅酸链组成的毛状层，对其来源进行了初步解释。
We studied systematically aqueous suspensions of amorphous well-characterized silica particles by potentiometric titration, electrophoretic mobility, and time-resolved light scattering. Their charging behavior and aggregation rate constants were measured as a function of pH and ionic strength in KCl electrolytes for three types of particles of approximately 30, 50, and 80 nm in diameter. The charging behavior was consistent with the basic Stern model; the silica particles carry a negative charge, and its magnitude gradually increases with increasing pH and ionic strength. On the other hand, their early-stage aggregation (or coagulation) behavior is complex. The aggregation of the largest particles shows features resembling predictions of the Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory. On one hand, the rate constant decreases sharply with increasing pH at low ionic strengths and attains fast aggregation conditions at high ionic strengths. On the other hand, we observe a characteristic slowing down of the aggregation at low pH and high ionic strengths. This feature becomes very pronounced for the medium and the small particles, leading to a complete stabilization at low pH for the latter. Stabilization is also observed at higher pH for the medium and the small particles. From these aggregation measurements we infer the existence of an additional repulsive force. Its origin is tentatively explained by postulating hairy layers of consisting of poly(silicilic acid) chains on the particle surface.