Photocatalytic degradation of the antiviral drug Tamiflu by UV-A/TiO2: Kinetics and mechanisms

The photocatalytic degradation of the antiviral drug Tamiflu (oseltamivir phosphate, OP) by TiO2 - P25, ST-01 and ATO was investigated in aqueous solution under ultraviolet (UV-A) irradiation. The photocatalysis of OP is well described by pseudo-first-order kinetics with r2 > 98.0% for all cases. The kinetic constant of P25 with 80% anatase and 20% rutile (0.040 min−1) is 4 and 10 times higher than that of ATO and ST-01 with 100% purity of anatase, respectively. We examined the effects of the catalyst loading and initial OP concentration on the photodegradation of OP, and used potassium iodine, isopropanol, and calcium fluorine as radical quenchers to evaluate the contributions of the hydroxyl radical (OH) and photo hole (h+) in the photodegradation. Results confirmed that 80% of the contribution came from the OH species. Although more than 95% of the OP (21 μM) was removed after 80 min of UV-A irradiation with 20 and 100 mg L−1 P25, the removal efficiencies of total organic carbon (TOC) were only 45.6% and 67.0%, respectively, after 360 min UV-A irradiation. Based on an intermediate analysis by HPLC coupled with a triple quadrupole spectrometer and an ion trap mass spectrometer, typical intermediate species such as hydration derivatives, hydroxyl substitutes and keto-derivatives were identified and possible degradation pathways of OP by P25 were proposed.