Physical Chemistry of Irregular Mixtures: A Chemical Kinetics Scan over the Collection of Montmorillonite Sorption Sites.

The simultaneous protection of food crops, soil, and water has been an ongoing issue for over 70 years. The technology required for the control of this has been stalled by one key fact. Soil is the ultimate example of physically and chemically irregular mixtures. Soils are also dynamic. Even soil components are irregular mixtures. The voluminous accumulation of related publications is all based on the assumption that the application of the correct physical chemistry is impossible for such mixtures. The research objective reported here is the demonstration that the correct chemical kinetics can be applied to an irregular mixture. The irregular mixture of montmorillonite sorption sites for atrazine is an example. Montmorillonite is one of the many crystalline aluminosilicates found in the Earth's crust. Weathering will add crystal lattice defects in addition to those predicted by the second law of thermodynamics. An irregular mixture of sorption sites for an organic compound was expected. An irregular mixture can be quantitatively characterized by an experimental scan of its components. An atrazine solution was used for two types of scans. A law of mass action scan over the reaction time revealed one set of sorption sites in which sorption equilibrium was established. This was not found for other sorption sites. Second-order chemical kinetics for sorption yielded the kinetic rate coefficients that characterize nonlinear kinetics. The scans of the kinetic rate coefficients over the numbers of filled sorption sites resolved the mixture of sorption sites into separate sets. These scan methods should be applied to environmentally important cases of contaminated agricultural soils.