An Overview of Chemical Oxidation Based Remediation technologies for Non-Aqueous Phase Liquids Removal from Soil

This review provides a general overview of the application of chemical oxidation to hydrophobic contaminants in the form of non-aqueous phase liquids (NAPLs). Three types of chemical oxidation processes, conventional activated persulfate, permanganate, and ozonation, along with three advanced oxidation processes (AOPs), the Fenton process, photocatalysis, and plasma oxidation are presented discussed. In addition, this paper provides a brief insight into the combination of chemical oxidation with other remediation technologies for the efficient removal of NAPLs. The common and wide use of activated persulfate for soil remediation is hindered by the fact that it needs heat activation, whereas the main drawback of using permanganate is the precipitation of manganese oxide at the NAPLs face. In addition, the high cost of equipment at the site restricts the ozone application for in-suit soil remediation. The application of AOPs processes such as Fenton and plasma oxidation has received great attention due to its high removal efficiency. However, photocatalysis technology in the field is difficult because it needs photo energy to run the oxidation process. Although plasma oxidation can degrade contaminants in minutes, some active species have short-lived time that could disappear before entering the soil layer. Ozonation is efficient in treat soils with low moisture and large pore spaces. Nevertheless, the optimal pH for ozonation oxidation is 3, which is hard to achieve in real-world applications. Combining chemical oxidation with other remediation technology is a valuable technique of soil remediation as the synergetic effects may increase the sustainability of the applied process towards green technology for soil remediation.