Forces between Colloid Particles in Natural Waters
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- 作者：Luke M. Mosley ; Keith A. Hunter ; and William A. Ducker
- 刊名：Environmental Science & Technology
- 出版年：2003
- 出版时间：August 1, 2003
- 年：2003
- 卷：37
- 期：15
- 页码：3303 - 3308
- 全文大小：235K
- 年卷期：v.37,no.15(August 1, 2003)
- ISSN：1520-5851
文摘
The origin and nature of interparticle forces acting oncolloid surfaces in natural waters has been examined usingan atomic force microscope. Natural colloids wererepresented by a surface film of iron oxide precipitatedonto spherical SiO2 particles, and the effects of adsorbednatural organic matter (NOM), solution pH, and ioniccomposition on the force-separation curves wereinvestigated. NOM from both riverine and marine environmentswas strongly adsorbed to the iron oxide surface. Underconditions of low ionic strength, the interparticle forces weredominated by electrostatic repulsion arising from negativefunctional groups on the NOM, except at very smallseparations (<10 nm) where repulsive forces arising fromsteric interference of the NOM molecules were alsopresent. At high ionic strength (e.g., seawater) or low pH,the electrostatic forces were largely absent, allowingsteric repulsion forces to dominate. In addition, adhesivebridging between surfaces by adsorbed NOM was observed,creating a strong energy barrier to spontaneous disaggregation of colloid aggregates. Our results demonstratethat adsorbed NOM dominates the surface forces and thusstability with respect to aggregation of natural watercolloids.