Utilization of electromigration in civil and environmental engineering - Processes, transport rates and matrix changes

Electromigration (movement of ions in an applied electric field) is utilized for supply or extraction of ions from various porous materials within both civil and environmental engineering. In civil engineering, most research has been conducted on the removal of chlorides from concrete to hinder reinforcement corrosion while in environmental engineering remediation of heavy metal polluted soil is the issue most studied.

Never the less, experiments have been conducted with utilization for several other materials and purposes within both engineering fields. Even though there are many topics of common interest in the use of electromigration for the two fields, there is no tradition for collaboration. The present paper is a review with the aim of pointing out areas of shared interest.

Focus is laid on the purposes of the different processes, transport rates of various ions in different materials and on changes in the matrix itself. Desorption and dissolution of the target elements into ionic form is a key issue to most of the processes, and can be the limiting step. The removal rate is generally below 1 cm day(-1), but it can be much less than 1 mm day(-1) when desorption is slow and insufficient.

Matrix changes occurs under the action of the applied electric field and it includes both physico-chemical and hydrological changes. Some of the solid phases is weathered and new can be formed. Increased fundamental understanding of the effects and side effects, when applying the electric field to a porous material, can lead to improvement of the known technologies and possibly to new applications.