Enhanced electrokinetic technologies with oxidization–reduction for organically-contaminated soil remediation

• Physical enhancement approaches for EK technologies were analyzed.
• Various additives-aided Redox-EK technologies were reviewed and compared.
• Advanced Redox-EK systems were presented.
• Comprehensive comparison among enhanced EK technologies was made.
• Future directions were provided for the related researchers.

EK remediation has been extensively studied over the last two decades and widely recognized as a promising method to treat different types of organically-contaminated soil (especially low-permeability soil). After EK remediation, however, the pollutants mainly concentrate in a small area or change to liquid phase in its original form and still need more efforts for complete removal. Through combining EK with other remediation technologies, not only can the reaction time be saved effectively, but also organic pollutants are decomposed within the soil and thus do not need extra treatment. This review focuses on the enhanced EK technologies with oxidization–reduction, aiming to interpret useful information to the researchers and practitioners in this field and provide promising research directions for future studies. Firstly, implications of many common oxidizing–reducing agents on the performance of EK technologies for soil remediation are analyzed, which include Fenton reagent, permanganate and persulfate. Various applications of oxidization–reduction technologies in configurations (i.e. zero-valent iron and Lasagna™) integrated with EK are then discussed, with respect to the treatment efficiency and limitation. The potentials and challenges of developing new enhanced/integrated EK technologies are finally discussed, providing many demanding areas for the future research, such as photoelectro-Fenton, EK-Fenton with ultrasound, EK-nano-ZVI, bimetallic systems with EK, EK-hypochlorite, EK-percarbonate and EK-ozone, and EK-redox-thermal desorption.