Calcite buffer effects in electrokinetic remediation of clopyralid-polluted soils

Abstract

This work presents a study of the dissolution-precipitation processes of calcite in soil undergoing electrokinetic remediation processes. For this purpose, a numerical inspection of one of these processes in a calcareous soil (10% calcite content) contaminated with an of the organochlorine acid herbicide (3,6-dichloro-2-pyridinecarboxylic acid) was carried out. The numerical tool used to perform this analysis was the Multiphysics for EKR (M4EKR), a module programmed by the authors in the COMSOL Multiphysics platform. A detailed analysis of the pH, the distribution of species that have a significant influence on soil buffering capacity (carbonates and calcite), as well as the pollutant, has been performed. In this way, the kinetics of the calcite dissolution-precipitation processes have been analysed in order to determine the pH of the water in the pores and, therefore, how it directly affects the effectiveness of the treatment. Additionally, a sensitivity analysis of the selected EKR process has been carried out at different values of the rate of calcite dissolution due to the uncertainty associated with the reactive surface area parameter.