Electrochemical Remediation of Soil Contaminants Using Conductive Polymer Electrodes

Abstract

Soil contamination by heavy metals and persistent organics remains a pressing environmental challenge. Electrochemical remediation (ECR) provides an in-situ strategy for contaminant removal, but efficiency is often limited by inert electrode materials. Conductive polymers (CPs) such as polyaniline (PANI) offer redox activity, ion-exchange properties, and compatibility with bioelectrochemical processes. A laboratory-scale soil column system was established with sandy loam spiked with Cd²⁺ (100 mg/kg) and phenanthrene (200 mg/kg). Triplicate treatments included (i) PANI-coated carbon felt electrodes, (ii) graphite electrodes, and (iii) no-electric-field control. Electrodes were polarized at 2 V/cm for 30 days. Soil pore water and solid samples were analyzed periodically for contaminant concentrations, pH, and redox potential (Eh). After 30 days, Cd²⁺ concentrations decreased by 82 % with PANI electrodes (to 18 ± 5 mg/kg), compared to 54 % with graphite and 7.7 % in controls. Phenanthrene was reduced by 76 % with PANI, 45 % with graphite, and 14.2 % in controls. PANI electrodes moderated extreme pH gradients (anode pH 4.1; cathode pH 8.3) and facilitated stable redox transitions (Eh 200 → −50 mV near cathode). The PANI electrode system consumed 30% less energy than graphite. In contrast, graphite electrodes suffered greater fouling and activity loss (62% retention). Conductive polymer electrodes substantially improved heavy metal and organic pollutant removal and reduced energy demand compared to conventional electrodes. These findings support conductive polymers as promising functional electrodes for scalable electrochemical soil remediation.