Regulating the electrokinetic delivery of Tween 80 and persulfate for remediating low-permeability phenanthrene contaminated soil: Importance of reducing unproductive consumption

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 phen-anthrene (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 trans-ported 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 celcius by electrical resistance heating, the total removal rate of PHE increased to 71.58 %. EPR spectrum indicated that SO4.- and OH. were responsible for the degradation of PHE.