Application of novel polypyrrole/melamine foam auxiliary electrode in promoting electrokinetic remediation of Cr(VI)-contaminated soil

There is an urgent need for an effective remediation method for soil that has been heavily polluted by heavy metals. The application of polypyrrole/melamine foam (PPy-MF) auxiliary electrode in the traditional electrokinetic remediation (EKR) system greatly increased the removal efficiency of Cr(VI) by enhancing electrical conductivity in soil, current strength of the system, and optimized the distribution of the electric field. Because of the strong Lewis acid property of PPy, it can inhibit the development of an alkali front in the EKR process in addition to buffering the polarization of the catholyte's pH. Application of PPy-MF auxiliary electrode increased the removal rates of both total Cr and Cr(VI) by 34.5 % and 11.5 %, 26.1 % and 10.1 %, and 25.2 % and 9.9 % at 30 V, 45 V, and 60 V voltage conditions, respectively, compared with traditional EKR, and improved the overall soil Cr(VI) reduction rate. Additionally, due to the effective Cr(VI) adsorption reduction of PPy-MF, the total Cr concentration in the anolyte was significantly decreased. This study provides a facile and effective way in remediation of Cr(VI)-contaminated soils. [Display omitted] •PPy-MF had a positive effect on both the current intensity and electric field distribution of EKR.•PPy-MF could prevent the development of an alkali front in EKR.•The use of PPy-MF improved the removal rate of total chromium and Cr(VI).•The combination of PPy-MF enhanced electromigration and its adsorption reduction of Cr(VI) is the key mechanism.