Accelerated photocatalytic degradation of iohexol over Co3O4/g-C3N4/Bi2O2CO3 of p-n/n-n dual heterojunction under simulated sunlight by persulfate

A novel Co3O4/g-C3N4/Bi2O2CO3 (BCCN) photocatalyst with p-n/n-n heterojunction was synthesized through a solvent-thermal method. The degradation efficiency of 20 mg/L iohexol reached 94 % in 60 min (k(app) = 0.0417 min(-1)) in BCCN/light/PS system, which was 2.8 and 6.5 times higher than systems of BCCN/light (k(app) = 0.0150 min(-1)) and BCCN/PS (k(app) = 0.0064 min(-1)). The g-C3N4 addition lowered conduction band of the prepared material to produce superoxide radicals, activate persulfate and further prevent the recombination of photoelectrons and holes. Superoxide radicals and singlet oxygens were dominant radicals for iohexol degradation. Besides, persulfate could act as electron acceptor to enhance efficiency of electron transfer. The interaction between sulfate, superoxide and hydroxyl radicals improved singlet oxygens production. Furthermore, theoretical calculation and liquid chromatography mass spectrometry were performed to analyze degradation pathway of iohexol in the system. Ultimately, the BCCN/light/PS system can provide a new method to degrade organic pollutants in aquatic environments.