Recent Advances in Oxidation and Reduction Processes for Treatment of PFAS in Water

Treating PFAS in water and wastewater is extremely challenging, as these contaminants resist most conventional treatment technologies. Advanced treatments such as activated carbon, high-pressure membranes and ion exchange show greater success; however, these technologies only concentrate the contaminants, and the concentrated waste stream needs further treatment. Oxidation/reduction (redox) processes are considered highly attractive alternatives, primarily due to their destructive nature. However, the high chemical stability of PFAS (specifically the stability of the carbon–fluorine bonds) makes most conventional redox processes ineffective. Nevertheless, some specific processes have been successfully applied recently. For example, activated persulfate, which is based on the reactive sulfate radical, showed effective degradation of PFAS, notably when combined with a mechanical ball milling. Other advanced oxidations such as electrochemical oxidation and ultrasonication also showed some degree of success; however, scalability problems still limit their wide application. Advanced reductions, although effective in reducing and defluorinating PFAS, require extreme conditions such as high pH and the lack of oxygen, which rarely exist in natural water. In general, redox processes can be competitive PFAS treatment options in cases involving concentrated low-volume waste streams, such as waste from sorbent regeneration and treatment of membrane brine.