Photocatalytic degradation of tetracycline using nanosized titanium dioxide in aqueous solution

Abstract

The aim of the study was to investigate the degradation kinetics of tetracycline antibiotic by nanosized titanium dioxide under ultraviolet irradiation. Enhancement of photocatalysis by addition of Hydrogen peroxide was also evaluated. Various experimental parameters such as initial tetracycline concentrations, initial titanium dioxide concentration, initial pH, reaction times, initial Hydrogen peroxide concentrations, as well as water matrix using ultrapure water, drinking water and secondary effluent were investigated. The initial rate of photocatalytic degradation of tetracycline well fitted the Langmuir–Hinshelwood kinetic model (R 2 = 0.9926) with a reaction rate constant of 1.4 mg/L min. The degradation rate depended on initial tetracycline concentration and initial pH. The degradation rate also increased with higher titanium dioxide density and reached a plateau at titanium dioxide concentration of 1.0 g/L. The tetracycline degradation rate was higher in drinking water compared to ultrapure water. The addition of Hydrogen peroxide to titanium dioxide suspension significantly enhanced the tetracycline degradation rate and substantially reduced the time required to degrade 100 % of tetracycline. Changes of chemical oxygen demand values during photolysis indicated that tetracycline transformed into intermediate products without complete mineralization. The ultraviolet visible spectra obtained before and after ultraviolet irradiation in the presence of titanium dioxide can indicate the formation of 4a,12a-anhydro-4-oxo-4- dimethylaminotetracycline.