title: Influence of ionic strength on the surface charge and interaction of layered silicate particles.
abstract: The surface charge densities and surface potentials of selected phyllosilicate surfaces were calculated from AFM surface force measurements and reported as a function of ionic strength at pH 5.6. The results show that the silica faces of clay minerals follow the constant surface charge model because of isomorphous substitution in the silica tetrahedral layer. A decreasing surface charge density sequence was observed as follows: muscovite silica face>kaolinite silica face>talc silica face, which is expected to be due to the extent of isomorphous substitution. In contrast, at pH 5.6, the alumina face and the edge surface of kaolinite follow the constant surface potential model with increasing ionic strength, and the surface charge density increased with increasing ionic strength. The cluster size of suspended kaolinite particles at pH 5.6 was found to increase with increasing ionic strength due to an increase in the surface charge density for the alumina face and the edge surface. However, the cluster size decreased at 100mM KCl as a result of an unexpected decrease in the surface charge of the alumina face. When the ionic strength continued to increase above 100mM KCl, the van der Waals attraction dominated and larger clusters of micron size were stabilized.
authors.affiliation: Department of Metallurgical Engineering, College of Mines and Earth Sciences, University of Utah, 135 South 1460 East, Room 412, Salt Lake City, UT 84112-0114, USA. Electronic address: liujing.dream@gmail.com.
authors.forename: Jing
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Metallurgical Engineering, College of Mines and Earth Sciences, University of Utah, 135 South 1460 East, Room 412, Salt Lake City, UT 84112-0114, USA. Electronic address: Jan.Miller@utah.edu.
authors.forename: Jan D
authors.initials: JD
authors.lastname: Miller
authors.affiliation: Department of Metallurgical Engineering, College of Mines and Earth Sciences, University of Utah, 135 South 1460 East, Room 412, Salt Lake City, UT 84112-0114, USA. Electronic address: xihui1010@gmail.com.
authors.forename: Xihui
authors.initials: X
authors.lastname: Yin
authors.affiliation: Summit Valley Technologies, FLSmidth USA Inc. - Salt Lake City Operations, 7158 S FLSmidth Drive, Midvale, UT 84047, USA. Electronic address: V.Gupta@flsmidth.com.
authors.forename: Vishal
authors.initials: V
authors.lastname: Gupta
authors.affiliation: Department of Metallurgical Engineering, College of Mines and Earth Sciences, University of Utah, 135 South 1460 East, Room 412, Salt Lake City, UT 84112-0114, USA. Electronic address: X.Wang@utah.edu.
authors.forename: Xuming
authors.initials: X
authors.lastname: Wang
keywords: Cluster size; Ionic strength; Layered silicates; Surface charge; Surface potential