Migration of bimolecular reactive solutes considering nonequilibrium sorption

A one-dimensional transport model for bimolecular reactive solutes under nonequilibrium sorption is developed for the characteristics of solute nonequilibrium sorption. The transport process of bimolecular reactive solutes under advection, dispersion, sorption (equilibrium and nonequilibrium) and reaction (oxidation and natural oxygen demand) is considered, and the COMSOL Multiphysics is used to solve the model numerically. The most important results are as follows: (1) The first stage of pollutant removal under nonequilibrium sorption conditions is the rapid remediation dominated by oxidation reactions, and the second stage is the slow remediation dominated by nonequilibrium sorption. (2) Considering nonequilibrium sorption can describe the pollutant tailing more accurately. (3) The chemical reaction rate \tilde k, equilibrium sorption ratio \tilde f and nonequilibrium sorption rate \tilde a significantly influence the removal efficiency of pollutants, and the impact of \tilde a is related to the rate of equilibrium sorption to total sorption f. The effects of the Peclet number are less obvious. (4) In cases of small \tilde k, \tilde a, \tilde f and large Pe, the tailing effects are more serious, and nonequilibrium sorption must be considered.