Kinetic Study of Photocatalytic Degradation of Several Pharmaceuticals Assisted by SiO2/ TiO2 Catalyst in Solar Bath System

The photo-catalytic degradation of five pharmaceuticals using TiO2 modified with SiO2, and sun light was monitored. The initial concentrations used in the solar bath system were100 µg/L for caffeine, diclofenac, glimepiride and ibuprofen, and 25 µg/L for methotrexate. Kinetic disappearance of caffeine, diclofenac, glimepiride and ibuprofen shows pseudo- first order kinetics, while methotrexate shows a zero order kinetic degradation which was monitored using HPLC/UV at λ = 225 nm, F = 1ml/min and on a C8 reversed phase column. The rate constants for diclofenac (wastewater 0.3238 sec-1, distilled water 0.4057 sec-1), glimepiride (wastewater 0.2203 sec-1, distilled water 0.2771 sec-1), ibuprofen (wastewater 0.2802 sec-1, distilled water 0.2411 sec-1), caffeine (distilled water 0.416 sec-1) and methotrexate (distilled water 3.1407 mole L-1 sec-1). The removal efficiency for the drugs was ranged between 79% and 96%.