Chemometric assessment and investigation of mechanism involved in photo-Fenton and TiO2 photocatalytic degradation of the artificial sweetener sucralose in aqueous media

Chemometric optimization tools were employed, such as experimental design and response surface methodology (RSM) to assess the efficiency of two advanced oxidation processes (AOPs): homogeneous Fenton (FeII/H2O2) and heterogeneous (TiO2) photocatalysis for the degradation of the artificial sweetener sucralose. The aqueous samples were irradiated under a variety of experimental conditions (pH, light intensity) and with different amounts of H2O2, Fe(II), TiO2. The use of RSM allowed fitting the optimal values of the parameters leading to the degradation of the contaminant. Also, a single polynomial expression modeling the reaction was obtained for both AOPs. The intermediates formed during the photocatalytic and photo-Fenton process were investigated and characterized by means of HPLC/HRMS. The photocatalysed transformation of sucralose proceeds through the formation of few (eight) products, involving four different pathways: hydroxylation of the molecule, oxidation of the alcohol function, dechlorination and the cleavage of glycoside bond. All the identified intermediates were easily degraded and within four hours of irradiation complete mineralization was achieved. A comparison with Photo-Fenton reaction was also reported. In addition Microtox bioassay (Vibrio fischeri) was employed in evaluating the ecotoxicity of solutions treated by heterogeneous photocatalysis. Results clearly demonstrate the efficiency of the photocatalytic process in the detoxification of the irradiated solutions.