Comprehensive review of progress made in soil electrokinetic research during 1993–2020, Part I: Process design modifications with brief summaries of main output

Since the early 1990s, soil electrokinetic remediation (SEKR) has been exploited for removing organic, inorganic, and radioactive material from contaminated soil. However, the application of SEKR has been met with multiple obstacles; thus, trials have been introduced to overcome these limitations. The present study provides a comprehensive review of various modifications applied to SEKR process designs. We classified the SEKR designs in horizontal, vertical, and mixed (horizontal and vertical) types as per the movement of contaminants. SEKR is conducted via four mechanisms, namely electromigration, electroosmosis, diffusion, and electrophoresis, when a direct current electrical field is applied among two electrodes to achieve contaminant movement from one location to another. During SEKR operation, the removal rate can be adversely affected by factors such as the formation of a pH jumping zone, very high (low) pH around the cathode (anode), polarization, and reduced current efficiency with increase in time. Accordingly, in a previous research, the regular design of SEKR has been modified to address these and other limitations. Moreover, soil electrokinetic (SEK) has been used for other applications such as land restoration, geophysics, dewatering, and consolidation. This review primarily aims to provide a comprehensive summary of the major design modification made to SEK processes in the past 28 years, (1993–2020) to facilitate research on the major aspects of SEK. As per our extensive literature survey, most relevant studies focused on the horizontal SEK design. This study discusses relevant SEK studies in which process design modification is considered.