Highly Efficient Performance of Gamma-Irradiation on the Decolorization and Degradation of Sunset Yellow Dye in Aqueous Solutions

This study aimed to investigate the gamma radiolytic decolorization and degradation of Sunset Yellow (SY), a widely used dye globally. Synset yellow aqueous solutions were subjecting to irradiation using a semi-industrial 60Co gamma-irradiation facility, applying doses between 0.2 and 5 kGy. Various analytical techniques, including UV-visible spectroscopy, colorimetry, Total Organic Carbon (TOC) analysis, and LC/MS, were used to monitor the changes in the irradiated solutions. The impact of various factors, including initial concentration, dose rate, and pH, on the effectiveness of degradation was examined. Obtained results indicated that the degradation process is most effective at lower initial dye concentrations, higher dose rates, and at neutral pH. Indeed, an impressive TOC removal of 98% was reached after applying 5 kGy suggesting quasi total mineralization. Based on spectrophotometric analyses, it was found that the degradation kinetic of SY adhered to a pseudo-first order reaction, assuming a quasi-steady state approximation for hydroxyl radical species. Furthermore, the identification of several SY by-products through liquid chromatography-mass spectrometry (LC/MS) have permitted a depth undersatding of SY degradation mechanism which have allowed a proposal of its degradation mechanistic schema mediated by hydroxyl radicals.