Transformation pathway and degradation mechanism of methylene blue through β-FeOOH@GO catalyzed photo-Fenton-like system

To enhance the catalytic and separation properties of akaganeite nanoparticles, rice spike-like akaganeite impregnated graphene oxide (beta-FeOOH@GO) nanocomposite was fabricated through facile hydrolysis. The apparent first-order decolorization rate of methylene blue (MB) in beta-FeOOH@GO catalyzed photo Fenton-like system was 0.6322 min(-1) about 3 folds that of prinstine beta-FeOOH nanoparticles. The degradation intermediates of MB adsorbed on the solid surface of beta-FeOOH@GO were comprehensively identified with time of flight-secondary ion mass spectroscopy (TOF-SIMS) for the first time. Newly identified sulfoxide intermediates, sulphone intermediates and desulfurization intermediates and N-demethylaton or dedimethamine intermediates were reported for the first time. The proposed degradation pathway of MB predominantly proceeded with the rupture of phenothiazine rings oxided with (OH)-O-center dot, HO2 center dot- and singlet oxygen (O-1(2)) radicals, which fully extending the reaction pathways proposed in previous work in literature. The enhanced catalytic activity of beta-FeOOH@GO was ascribed to the formation of heterojunctions confirmed by the presence of Fe-O-C chemical bonds through X-ray photoelectron spectroscopy (XPS). The complete elimination of MB and its acute toxicity to Luminous bacteria showed that beta-FeOOH@GO would be served as a highly efficient Fenton-like catalyst for treatment of high concentration refractory organic contaminant. (C) 2018 Elsevier Ltd. All rights reserved.