Utilizing the approaching/movement electrodes for optimizing the soil electrokinetic remediation: A comprehensive review

Applying soil electrokinetic remediation (SEKR) is considered a valuable technique to remediate contaminants-containing low permeability soils with the advantage of integration with other remediation approaches (e.g., chemical, physical, and biological). The basics and principles of electrokinetic remediation (EKR) were utilized in different fields of interest; for example, sedimentation, seed germination, consolidation, dewatering, etc. The present review is focused on the role of the electrode approaching/movement technique (EAMT) in improving the effectiveness of the SEKR. Based on our search in the collected literature, the influence of the EAMT on soil electrokinetic efficiency yielded no pertinent reviews. We looked for articles relevant to the EAMT in six search engines, and articles collected for the present review were chosen based on the data mentioned in the materials and methods section. Our objective was to illustrate the proper applicability of the EAMT from different perspectives to overcome some obstacles reported with the traditional SEKR. The effect of the EAMT is discussed/illustrated from four perspectives including a) the approaching/moving anode technique (AMAT), b) the approaching/moving cathode technique (AMCT), c) electrodes placement/gap, and d) continuously reoriented/rotating, reciprocating, and rotational electric fields. Several advantages could be gained from the EAMT application including a) improving the current passing, b) soil pH reduction, c) increasing heavy metals desorption, d) elevating the redox potential, e) reducing the energy consumption, f) increasing the removal percentages of contaminants, g) reducing extra chemical additives or pH modifications, h) enhancing electroosmotic flow, i) installing auxiliary electrodes presents a more stable current and uniform electric field, and j) ultimately reducing the environmental risks of heavy metals. Two methods were proposed for the practical applications of the EAMT (in-situ and ex-situ). Although there are various advantages were achieved from the application of the EMAT, the published research during the past 31 years (1993–2023) is few compared to other enhancement approaches.