Reaction Mechanism and Degradation Pathway of Rhodamine 6G by Photocatalytic Treatment

The photocatalytic degradation of a cationic dye, rhodamine 6G (Rh-6G) under UV light irradiation was carried out. Rh-6G was completely decolorized in 180 min of photo-oxidative degradation period. The extent of degradation was confirmed performing total organic carbon (TOC) analysis, and up to 90.14%, TOC removal was achieved. Several critical analytical techniques including UV-Vis spectroscopy, high-performance liquid chromatography (HPLC), and ultra-performance liquid chromatography coupled with electrospray ionization mass spectrometry (UPLC/MS) were employed to scrutinize the mechanistic insights of the dye photodegradation. The degraded N-demethylation intermediates and several small molecular products were qualitatively identified, and a tentative photodegradation pathway was proposed. Toxicological evaluation of the degradation products was carried out three types of cell lines (MTT assay) and Triticum sativum seeds. In conclusion, enhanced biodegradability accompanied by toxicity reduction confirmed the promising efficiency of photocatalysis for Rh-6G degradation and therefore could be used for the remediation of textile effluents.