Sulfate radical advanced oxidation processes: activation processes and application to industrial wastewater treatment – a review

The industrial wastewaters (IWW) are derived from industrial activities, which comprehend dairy or breweries, paper industry, wine and olive production, among others. The organic content can reach thousands of mg/L, with wide pH, and low biodegradability. Advanced oxidation processes (AOPs) are an efficient process for pollutants degradation, which are based on the generation of hydroxyl radicals (HO^•). These radicals are highly reactive and capable of oxidizing a wide range of contaminants, especially those refractory contaminants. Considering the different AOPs, in this review it will be studied the application of sulfate radical AOPs (SR-AOPs) for the treatment of IWW. The aim of this work is to study the different activation processes of sulfate radicals, evaluate the efficient of SR-AOPs in the treatment of IWW and review the advantages and disadvantages associated with the application of these radicals.

Both persulfate (PS) and peroxymonosulfate (PMS) can be activated by a variety of methods, such as heat, alkaline, radiation and transition metals. These methods have been applied to the treatment of IWW, with results showing an efficient degradation of different contaminants at laboratory and pilot scales. It was also observed that the reagents required in SR-AOPs were lower than the required in HR-AOPs. Despite these advantages, it was also pointed also some disadvantages associated to SR-AOPs, such as the energy required in heat activation, the poor penetration of UV radiation in dark waters and the generation of sludges with activation metals. As a final remark, it can be highlighted that SR-AOPs are feasible technologies for IWW treatment.