Solar-initiated photocatalytic degradation of carbamazepine on excited-state hexadecachlorophthalocyanine in the presence of peroxymonosulfate

Abstract

In the field of environmental catalysis, the construction of highly efficient and stable catalytic oxidation processes has raised considerable attention. In this study, a novel solar-initiated photocatalytic oxidation system, FePcCl16/PMS/Sunlight, was established by iron hexadecachlorophthalocyanine (FePcCl16) with peroxymonosulfate (PMS) in the presence of sunlight excitation. Under sunlight irradiation, the phthalocyanine ring of the FePcCl16 is motivated to FePcCl16∗ in the excited state, which activates PMS to generate free radicals or high–valent iron(IV)-oxo intermediates (Fe(IV)=O) to oxidize carbamazepine (CBZ). The system could degrade CBZ effectively and total-organic-carbon removal from solution reached nearly 80% within 90min. FePcCl16 catalytic activity was almost without loss and without iron leaching after twenty recycles, indicating that the FePcCl16/PMS/Sunlight was a stable and efficient photocatalytic oxidation system. Electron paramagnetic resonance, gas chromatography-mass spectrometry and photocatalytic-activity-experiment analysis shows that Fe(IV)=O species, singlet oxygen (1O2), hydroxyl and sulfate radicals (OH, SO4−) are the main active species in the catalytic oxidation of CBZ. Density functional theory (DFT) calculations exhibits that the electronic cloud for excited state FePcCl16∗ is transferred from the porphyrazine ring and peripheral substituents to the central Fe atom and its axial position. The main degradation intermediates and possible degradation pathway of CBZ were proposed by ultra-performance liquid chromatography and high-resolution mass spectrometry (UPLC Synapt G2-S HDMS). This study provides efficient catalytic oxidation support for wastewater treatment.