Walter J. Farmer, 1994. "The Movement of Neutral Particles in Charged Media", Layer Charge Characteristics of 2:1 Silicate Clay Minerals, A. R. Mermut, S. A. Boyd, W. J. Farmer, W. F. Jaynes, G. Lagaly, D. A. Laird, A. R. Mermut
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The fate and behavior of toxic organic compounds in the soil environment has become a worldwide concern and has led to considerable research on the transport of trace organic chemicals through porous media. The transport of trace organic chemicals in soil is generally described in predictive models based on a distribution of a chemical between an immobile sorbed phase, a solution phase and an air phase. The distribution of the solute in the various phases is assumed to be determined by a soil/water distribution coefficient and a Henry's constant. This approach assumes the solution phase concentration is given by the aqueous solubility relationships of the organic compound. Recent attention has been given to consideration of a multicomponent solution phase that would include associations of organic solutes with particulates and dissolved organic matter (DOM). The presence in the soil solution of compounds associated with particulates or with soluble humic substances would influence the behavior of the compound in a manner that would be expected to differ from that based on solubility relationships alone and has led to speculations of a carrier mechanism operating to influence movement in the soil solution. Current transport models are inadequate to account for a carrier mechanism.
The notion of neutral particles being transported in porous media was invoked in the tittle of this chapter to imply that if a particle was charged it is more likely to interact with the porous media structure and thereby removed from suspension. At the same time, a neutral particle, depending
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Layer charge is recognized as the single most important characteristic of 2:1 phyllosilicates. It indicates a mineral's capacity to retain cations and to adsorb water and various polar organic molecules. The affinity of organic-clays for sorption of organic contaminants in aqueous systems is now attracting considerable attention. The layer charge is also considered an important criterion for the classification of 2:1 silicate clay minerals. It is generally agreed that the magnitude of the layer charge can be taken into account to resolve the classification problem. Studies on structural chemistry also confirm the importance of layer charge for characterization of silicate clays.”