Enhanced in-situ zero-valent iron activated persulfate oxidation with electrokinetics for the remediation of petroleum hydrocarbon contaminated soil

In the process of in-situ chemical oxidation (In Situ Chemical Oxidation) remediation of soil contaminated with petroleum, there is a region where the delivery of oxidant is limited, there are low permeability areas in the heterogeneous soil medium where the delivery of oxidant is limited, which affects the effectiveness of remediation. To overcome this issue, a combination of in-situ oxidation with zero-valent iron (ZVI)-activated sodium persulfate (PS), electrokinetic (EK) remediation, and additional humic acid (HA) enhancement was proposed. This combination was used to promote the oxidation of total petroleum hydrocarbons (TPH) in the contaminated soil. After 7 days of treatment, electrokinetic-enhanced oxidation by PS resulted in better TPH removal (23.72 %) than EK/PS (17.02 %) or In Situ Chemical Oxidation alone (12.21 %). The addition of 5% HA further increased the removal rate of the combined remediation by 4.63 %. Analysis of the enhancement mechanism revealed that the application of EK significantly enhanced the migration of the oxidant to the contaminated soil mainly through electromigration. However, it also resulted in uneven distribution of PS in the soil. The introduction of ZVI improved the remediation effect at locations with low PS Gas chromatography-mass spectrometry (GC-MS) analysis showed that the degradation difficulty of each component of TPH was different. The soil residue after the seven-day reaction revealed that the particularly recalcitrant constituents were the straight-chain alkanes (ranging from C16 similar to C19) and 2,2 '-methylenebis[6-(1,1-dimethylethyl)-4-methyl-phenol from the phenolic compounds.