Impact of Biodegradable Polyelectrolytes on Anomalous Pb Migration Performance during Soil EKR

This study investigates the migration of lead (Pb) during soil electrokinetic remediation (EKR) with sodium alginate (SA), providing important data on ion orientation and Pb removal efficiency. A 1   mV/cm voltage was applied to kaolinite contaminated with Pb²⁺, and SA was applied to regulate Pb migration. Pb was detected in both the anolyte and catholyte, with varying molar Pb/C ratios. In the anode and cathode chambers, the molar ratios reached 1:7.79 and 1:2.64, respectively. The addition of Pb 2+ disrupted the stable structure of SA, and density functional theory (DFT) calculations combined with X-ray Absorption Fine Structure (XAFS) analysis showed that Pb²⁺ forms dual-ridentate (positively charged) and quad-/hexaridentate (negatively charged) complexes with SA, thereby influencing Pb migration toward the corresponding electrodes. Additionally, Pb in the soil transformed into immobile particulate states, such as PbO 2 , Pb 3 O 4 , and PbO. The formation of these particulate phases and conversion of mobile Pb phases to the anode reduced the Pb migration ability at the cathode. These findings offer fresh perspectives on EKR’s application for heavy metal soil remediation, particularly six-period metals on the periodic table, improving our understanding of Pb behavior during electrokinetic treatments.