Singlet oxygen as a selective oxidant in advanced oxidation processes for water treatment

Singlet oxygen (¹O₂), a highly reactive yet non-radical oxidant, has become a key species in advanced oxidation processes (AOPs) for sustainable water and wastewater treatment. Unlike hydroxyl (•OH) and sulfate (SO₄•⁻) radicals, ¹O₂ exhibits strong electrophilic selectivity toward electron-rich pollutants, enabling efficient degradation with reduced scavenging by background ions and natural organic matter. This review summarizes the physicochemical fundamentals of ¹O₂, including its generation, lifetime, and reaction mechanisms in aqueous media. Various generation pathways—photochemical photosensitization, catalytic activation of oxidants such as peroxymonosulfate, and emerging electrochemical systems—are discussed, emphasizing design strategies that enhance quantum yield, stability, and energy efficiency. Comparative assessment with conventional reactive oxygen species highlights the distinctive advantages of ¹O₂ in selectivity, matrix tolerance, and solar compatibility. Furthermore, the review explores its dual role in contaminant oxidation and microbial disinfection, underlining its environmental relevance. Despite significant progress, limitations persist regarding its short lifetime, detection accuracy, and catalyst deactivation in complex waters. Addressing these challenges through material innovation, hybrid process coupling, and real-time monitoring can advance ¹O₂-mediated AOPs from laboratory research toward scalable, low-energy technologies for selective and sustainable water purification.

کلیدواژه ها:

Singlet oxygen ، Advanced oxidation processes ، Water and wastewater treatment ، Selective oxidation ، Photochemical generation ، Non-radical pathways