Regulating the ion migration pathways to enhance Joule heating effect and dense nonaqueous phase liquid removal using pulsed direct current

Electrical resistance heating (ERH) based on pulsed direct current (PDC) is a novel and promising in-situ technology for the remediation of dense nonaqueous phase liquid (DNAPL) contaminated sites. However, the uniformity and stability of heating still require further improvement. In this study, we proposed an effective strategy for optimizing the PDC heating process by regulating the ion behavior within porous media. Hydraulic circulation (flow field control) and intermittent polarity reversal (electric field control) were introduced as regulation measures for ion behavior, leading to overall improvements in average temperature, heating uniformity, EC and ion distribution uniformity, DNAPL removal, and energy efficiency. Compared to the unregulated system, heating uniformity improved significantly, with approximately a 40 % reduction in the coefficient of variation and a 15–30 °C increase in the average temperature. The uniformity of ion and EC distribution was significantly enhanced, while severe local ion depletion was effectively prevented, demonstrating the importance of regulating ion migration pathways. Following these regulatory measures, chlorobenzene DNAPL removal efficiency increased by 19.8 %–37.8 %, while energy consumption decreased by 12.8 %–47.5 %. These findings suggest that regulating the ion migration pathways was a promising approach for optimizating thermal remediation using PDC. • Regulating ion migration pathways effectively improved the PDC heating process. • Hydraulic circulation and polarity reversal were effective ion control measures. • Average temperature and uniformity greatly improved compared to unregulated system. • DNAPL removal efficiency increased by 19.8 %∼37.8 %, with lower energy consumption.