In this study, coupling electrokinetic (EK) with the permeable reactive barriers (PRB) of Fe/Mn/C-LDH composite was applied for the remediation of arsenic-contaminated soils. By using self-made Fe/Mn/C-LDH materials as PRB filler, the effects of pretreatment and polarization shielding on EK-PRB of Fe/Mn/C-LDH for remediation of arsenic contaminated soils were investigated. For the pretreatment, phosphoric acid, phosphoric acid and water washing, and phosphate were adopted to reduce the influence of iron in soil. The addition of phosphate could effectively reduce the soil leaching toxicity concentration. The removal rate of the soil pretreated with phosphoric acid or phosphoric acid and water washing was better than with phosphate pretreatment. For the polarization shielding, circulating electrolyte, electrolyte type, anion and cation membranes, and the exchange of cathode and anode were investigated. The electrolyte circulates from the cathode chamber to the anode chamber through the peristaltic pump to control the pH value of the electrolyte, and the highest arsenic toxicity removal rate in the soil reaches 97.36%. The variation of total arsenic residue in soil using anion and cation membranes is the most regular. The total arsenic residue gradually decreases from cathode to anode. Electrode exchange can neutralize H+ and OH- produced by electrolyte, reduce the accumulation of soil cathode area, shield the reduction of repair efficiency caused by resistance polarization, enhance current, and improve the removal rate of arsenic in soil.
Keywords: arsenic-contaminated soil; electrokinetic remediation; layered double hydroxide; polarization shielding; pretreatment.