Peroxymonosulfate enhanced electrokinetic remediation of PAHs-contaminated soil: Effects of periodic electric field

Power consumption is a key factor that affects the cost of electrokinetic (EK) remediation technology. However, the impact of a periodic electric field on organic pollutant removal and energy saving when using EK enhanced chemical oxidation technology has been unclear. In this study, one experiment with a continuous current and five experiments with periodic electric fields of different periodic frequencies (1:1, 2:1, and 3:1) and power-off times (0.5, 8, and 24 h) combined with peroxymonosulfate (PMS) were performed to remove polycyclic aromatic hydrocarbons (PAHs) from soil. The results showed that the average current decreased along with an increase in the periodic frequencies (from 1:1 to 3:1). However, under the same periodic frequency (2:1) with different power-off times (0.5, 8, and 24 h), the currents were relatively close. Compared to the continuous current treatment, different periodic frequencies and power-off times all improved the PAHs removal rates, particularly those PAHs with high ring numbers. Among them, the treatment with the 2:1 periodic frequency and 1 day power-off time achieved the highest removal efficiency (36.1 % of total PAHs) and successfully enhanced PAHs removal in the anode area. Except for the treatment with the 1:1 periodic frequency and 1 day power-off time, the unit energy consumptions of the other periodic electric field treatments were lower than that of the continuous current treatment. This study demonstrates that a periodic electric field could reduce unit energy consumption and improve the PAHs removal efficiency, and the periodic frequency was a crucial factor. This study provides a new technical option for PMS-enhanced EK remediation of organic polluted soil and promotes the application and development of EK remediation technology.