Effects of Inorganic Anions and Humic Acid on the Photocatalytic and Ozone Oxidation of Oxytetracycline in Aqueous Solution

Oxytetracycline (OTC), a widely used tetracycline group antibiotic, was treated by TiO2 mediated photocatalytic and ozone oxidation processes in the aqueous medium. While the ozone oxidation process was able to remove antibiotics completely from the synthetically contaminated water within a 2-minute treatment period with an applied ozone dose of 36 mg L-1, for the photocatalytic oxidation process about a one-hour treatment period was necessary to obtain the same treatment efficiency. As well as the process parameters the effects of various anions, chloride (Cl-), sulphate (SO42-), nitrate (NO3-), bicarbonate (HCO3-), dihydrogenphosphate (H2PO4-), and humic acid on the degradation of OTC by these oxidation processes have been investigated. It was found that the nature and concentrations of these inorganic anions significantly affect the performance of photocatalytic and ozone oxidation processes. The strongest inhibition effect on OTC degradation by ozonation process was observed in the presence of humic acid at a concentration found in natural water systems.