GC-MASS detection of methyl orange degradation intermediates by AgBr/g-C3N4: Experimental design, bandgap study, and characterization of the catalyst

Abstract

As synthesized AgBr nanoparticles (NPs) and g-C3N4 nanosheets were synthesized and coupled to obtain the AgBr-g-C3N4 catalyst, It showed a boosted activity in the photodegradation of methyl orange (MO) in aqueous solution (1.6 and 1.3 times greater than just the AgBr and g-C3N4 NPs in the initial degradation experiments without any optimization, respectively). The composite was characterized by X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), cyclic voltammetry (CV), etc. The modified carbon paste electrode by the composite showed a significant increase in peak current, confirming a significant increase in charge transfer between the semiconductors of the coupled system. The bandgap energies of the samples were estimated by both DRS and CV methods. The composite with an AgBr:g-C3N4 mole ratio of 2:1 showed the best photocatalytic activity. The initial pH of the MO solution was changed from 6.5 to 5.5 during the photodegradation process. Experimental design by RSM was used for the study of the interaction effects between the influencing variables. The conditions of the optimized run were: pH: 3.5, Catalyst dosage: 0.9 g/L, Time: 83 min, CMO: 3.2 ppm, while those of the central point were: pH: 6.1, Catalyst dosage: 0.99 g/L, Time: 82.50 min, CMO: 2.9 ppm. Various degradation intermediates such as benzene, phenol, catechol, hydroquinone, aniline, dimethylamine, benzoquinone, p-amino phenol, ethendiol, ethylene glycol, oxalic acid, maleic acid, 1-propenoic acid, sulfate, etc. were detected by GC-Mass. Further attacking of hydroxyl and superoxide radicals can easily mineralize these intermediates to water, carbon dioxide, and other inorganic species.