Peculiarities of the Diffusion Transfer of Hydrophobic Organic Pollutants in Natural Disperse Systems

Abstract

The release of various pollutants into the environment necessitates monitoring their spreading in soils, developing strategies to prevent their transfer into water bodies, as well as identifying and conducting priority detoxification of those local contaminants that, due to their chemical and physical properties and the structure of polluted soils, pose the greatest risks. This article develops a theoretical theoretical basis and methodology for studying the diffusion transport of toxicants. Using a model dispersion of kaolin contaminated with o-chlorotoluene, the study investigates the diffusion rates of hydrophobic organic compounds in natural concentrated disperse systems. The experiments were conducted at various temperatures of the dispersion medium, both in the absence and presence of surfactant Triton X-100. A comparison was made between the temporal concentration distribution profiles of o-chlorotoluene in areas adjacent to the localized pollution zone and the results of theoretical calculations based on the Fick equation. Diffusion coefficients of the contaminant in the concentrated disperse system were calculated under the considered conditions of its spread. The obtained diffusion coefficients of o-chlorotoluene in the kaolin dispersion are significantly lower than the diffusion coefficients of organic hydrophobic compounds in aqueous media. This is attributed to the fine porosity of the model system used, the tortuosity of pores, and the interaction of o-chlorotoluene molecules with the dispersion surface. The structural factor and the presence of contact surface also contribute to a more pronounced reduction in the diffusion coefficient with decreasing temperature than would be expected due to the decrease in the energy of particle thermal motion and the increase in viscosity of the pore solution. The decrease in diffusion rate due to the formation of micellar aggregates of o-chlorotoluene with Triton X-100, caused by their larger sizes compared to individual molecules, is compensated by hydrophilization and the conversion of pollutants into a mobile state.