Temperature-driven coupled transport of pollutants and suspended particles established by granular thermodynamics

Abstract

The temperature-driven effects on pollutant transport are significant, including thermal diffusion of pollutants, thermal osmosis of solutions, thermal motion of suspended particles, and other deformation and transformation processes. The pollutant seepage field equation was derived based on granular thermodynamics, and the motion equation of suspended particles was derived from Newton's second law. A comprehensive coupled transport model for the two-phase flow of pollutants and suspended particles in saturated porous media was established, which can effectively consider the impact of temperature driving. The model accurately described the coupled transport process of pollutants and suspended particles under different temperatures and particle sizes during single-pulse injection. Furthermore, the application of this model in natural clay layers under varying temperature gradients was discussed. The results indicated that, for the same time, an increase in temperature at the high-temperature end led to a 36.5 % decrease in the peak concentration of pollutant transport. When the temperature difference was significant, thermal osmosis and thermal motion were the main mechanisms for the coupled transport of pollutants and suspended particles, with the diffusion mechanism induced by concentration and temperature gradients not dominating. Thermal diffusion positively drove the transport of pollutants, while thermal osmosis and thermal motion under temperature gradients had a reverse inhibitory effect on pollutant transport.