Electrochemical processing of soils: Theory of pH gradient development by diffusion, migration, and linear convection

Abstract

A theory, based on the Nernst‐Planck equations, is presented for pH gradient development during the electrochemical processing of soils. Its premises and consequences are discussed in terms of using electrochemical techniques for the decontamination of polluted media. Formation of an acidic front at the anode from water electrolysis and the induced electro‐osmotic flow of pore fluid contribute to facilitate removal of contaminants. The model provides a first‐order, mathematical framework to examine the flow patterns and chemistry generated in electro‐osmosis. Analytical solutions are compared with the numerical results obtained by the finite element method (FEM) and with some preliminary experimental results. Upstream‐downstream effects are included but consolidation effects, neutralization, and ion exchange reactions need to be quantified and incorporated into the model. The physical basis of electro‐osmosis phenomenon needs to be better established. Modelling approaches of this type should assist scale‐up of this technology for common inorganic toxic pollutants removal.