Han Cui,Xuejiao Wu,Yuchen Wang,Yafei Zhang,Juan Luo,Dandan Zhou
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.
Controllable delivery of persulfate (PS) and the enhancement of oxidative availability of pollutants in in-situ oxidative remediation of low-permeability polycyclic aromatic hydrocarbons (PAHs) contaminated soil are crucial. To tackle the above challenges, the coupling of Tween 80 solubilization enhanced oxidation of phenanthrene (PHE) in low-permeability soil under electrokinetic remediation (EKR) was proposed. Firstly, batch degradation experiments showed that the addition of Tween 80 significantly inhibited the degradation of PHE in soil under thermally activated PS, as the dosage of Tween 80 increased from 0 % to 1 % with the corresponding removal rate declining from 99.19 % to 40.90 %. Accordingly, in-situ electrokinetic delivery of Tween 80 and PS was regulated in further EKR, intending to reduce unproductive consumption. PS was more uniformly delivered to the whole remediation regions from the cathode chamber by electromigration , while Tween 80 was transported into the soil from the anode chamber by electroosmosis , which made Tween 80 solubilization and PS oxidation achieve synergistic effect . And the total removal rate of PHE reached 64.90 % under this strategy, which had increased by 415.90 % and 8.76 %− 130.14 % compared with only EKR or EKR coupling single enhanced technology , respectively. After further thermal activation of transported PS at 50 ℃ by electrical resistance heating, the total removal rate of PHE increased to 71.58 %. EPR spectrum indicated that SO 4 . - and OH . were responsible for the degradation of PHE.
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