Mechanistic limits and characteristic time-scale matching in electrokinetic remediation: A critical review of pulsed and continuous electric fields

Electrokinetic remediation (EKR) is an established technique for treating contaminated soils; however, its field-scale deployment remains constrained by inconsistent performance and high energy demand. While the debate between continuous and pulsed electric field operations persists, performance comparisons remain inconclusive due to the absence of a unified mechanistic framework. This review demonstrates that the apparent divergence in reported performance reflects a fundamental kinetic ceiling imposed by coupled electrochemical transport, interfacial polarization, and concentration-gradient evolution. Progressive electric double-layer polarization and the development of pH and ionic concentration gradients increasingly decouple the applied electric field from effective mass transport, thereby suppressing remediation efficiency and redirecting input energy toward parasitic losses such as Joule heating. We show that remediation outcomes are governed by a hierarchy of characteristic physicochemical relaxation time-scales spanning interfacial, transport, and electrochemical buffering domains. Building on this insight, a characteristic relaxation time-scale matching (CRTM) framework is proposed, reframing EKR operation from a binary choice between field modes into a mechanism-conditioned and state-aware control problem. By aligning external field modulation with the system’s intrinsic dynamics, the CRTM framework provides a chemically informed and predictive pathway for process intensification, improved energy efficiency, and enhanced scalability, advancing EKR toward rational engineering design and field-relevant implementation.