Generation of oxidative radicals by advanced oxidation processes (AOPs) in wastewater treatment: a mechanistic, environmental and economic review

In light of the rising presence of contaminants of emerging concern in water streams, in recent decades, advanced oxidation processes have received significant research interest, as the generation of oxidative radicals allows for the effective degradation of recalcitrant compounds. This review paper provides insights into the most relevant generation methods of several oxidative species, with a main emphasis on hydroxyl, sulfate, chlorine and iodine radicals. Understanding the strengths and pitfalls of each generation route is essential to set the baseline for future industrial applications. To this end, this review presents a comprehensive summary of how different techniques result in distinct radical types, and in addition to the principles and mechanisms of formation, the environmental and economic aspects behind the different methods are discussed.