Removal of aspartame by catalytic ozonation with nano-TiO2 coated pumice

Aspartame is widely used as an artificial sweetener and has been ubiquitously detected in various water sources, it is unstable and can produce some harmful degradation products under certain storage conditions. In this study, the degradation of aspartame through adsorption, single ozone, and catalytic ozonation was investigated. In order to create an eco-friendly catalyst, pumice surface was covered with nano-TiO2 and physicochemical surface properties of the catalyst were systematically investigated by SEM, EDX, FT-IR, BET, DLS, and pH(PZC) analysis. It was proved by SEM and EDX analysis that the nanostructures were homogeneously dispersed onto the catalyst surface and the surface of the catalyst was enriched at 5.5% by weight relative to the uncoated state. After coating, the catalyst surface area expanded by about 10 times and the pore diameters from 0.008 to 0.044. After characterization studies, the role of sole adsorption and sole ozonation in catalytic ozonation has been tried to be determined by using different doses of aspartame, catalyst, and ozone. In the catalytic ozonation experiments, reaction kinetics were analyzed in the presence of tert-butyl alcohol (TBA) that is a radical scavenger, and it was confirmed that the activity of (OH)-O-center dot radicals increased after using n-TCP as a catalyst. The results demonstrated that sole ozonation and adsorption of aspartame was not effective for removal. The rate of removal increased significantly with combining adsorption and ozonation. Synergism percentage was calculated to be 91.53. The benefit of surface adsorption, hydroxyl radicals, and sole ozonation to catalytic ozonation was determined as 2.96%, 72.20%, and 24.84%, respectively. Although ozonation of aspartame was initiated by (OH)-O-center dot radical, both (OH-)-O-center dot radical and O-3 might be involved in the aspartame removal.