Hydroxyl radicals based advanced oxidation processes (AOPs) for remediation of soils contaminated with organic compounds: A review

• The main drawback of conventional Fenton treatment is the reduction in soil pH.
• Modified Fenton treatments can produce OH at a pH near neutral.
• The lack of visible light activity hinders the practical applications of photocatalysis.
• Ozonation is suitable to treat soils with large pore spaces and low moisture.
• Plasma oxidation is able to treat soils with high concentration pollutants.

Advanced oxidation processes (AOPs) constitute a promising technology for the remediation of soils contaminated with non-easily removable organic compounds. This review provides the reader with a general overview on the application of AOPs to pesticides, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and total petroleum hydrocarbons (TPHs) contaminated soils remediation. Four types of AOPs including Fenton processes, TiO2 photocatalysis, plasma oxidation and ozonation were discussed. In particular, this paper focuses on the fundamental principles and governing factors of the two typical techniques – Fenton oxidations and TiO2 photocatalysis. Apart from the effect of chemical’s dosage as a major influencing factor, selected information such as pollutant characteristics, light intensity, soil characteristics and pH are presented. Some innovations (e.g., chelating agents, surfactants) on the traditional AOPs and the combined utilization of AOPs with other techniques (e.g., bioremediation, soil washing) are also documented and discussed. This review also highlights the effects of AOPs treatments on soil properties.

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