Effects of electrode geometry on electrokinetic removal of heavy metals and salt ions from co-contaminated soils

This study evaluated the performance of electrokinetic remediation on multi-metal-contaminated soil based on three electrode configurations: linear (1 anode-2 cathodes), trigonal (1 anode-2 cathodes), and square (1 anode-4 cathodes). The effects of co-contaminants and inter-ionic interferences on metal migration and removal were critically assessed. The findings revealed that the square configuration exhibited better removal efficiencies due to its improved electric field distribution and higher cathode coverage. With the same number of electrodes, the linear arrangement exhibited slightly better removal than the trigonal design, suggesting that spatial arrangement is a key factor in EK performance. The maximum removal was achieved for hexavalent chromium (Cr (VI)), followed by cadmium and lead, mainly because of the high complexation affinity of Cr (VI) for EDTA. Speciation analysis by Visual MINTEQ showed evidence of stable Cr-EDTA complexes being formed, allowing their mobilization. Introduction of EDTA not only enhanced the transport and solubility of target metals but also favoured the migration of natural cations (Na+, K+, Mg2+, Ca2+). In addition, harmful anions, SO4 2-and Cl-were reduced by 90 % and 80 %, respectively. The economic analysis confirmed the square configuration as the most cost-effective, with specific energy consumption (50 kWh/m3/g) and specific cost (701.5 US$/g). The study highlights the critical role of electrode arrangement in optimizing EKR processes and the mobilization and removal of heavy metals from polluted soils.