Review of characteristics, generation pathways and detection methods of singlet oxygen generated in advanced oxidation processes (AOPs)

•The 1O2-mediated advanced oxidation processes (AOPs) have significant potential in wastewater treatment.•The physical and chemical properties, and reaction characteristics of 1O2 are summarized.•1O2 can be produced by many pathways including direct catalytic and energy-assisted activation.•Multiple mature detection methods of 1O2 are collected in this review.•The existing deficiencies and improvements of 1O2 -mediated AOPs are discussed.