Optimization of photocatalytic degradation of meloxicam using titanium dioxide nanoparticles: application to pharmaceutical wastewater analysis, treatment, and cleaning validation.

Abstract

Meloxicam is a commonly prescribed nonsteroidal anti-inflammatory drug with analgesic and fever-reducing effects. In this study, photocatalytic degradation of meloxicam in the presence of TiO2 nanoparticles (TiO2NP) was optimized and applied for pharmaceutical wastewater treatment. A validated stability-indicating orthogonal testing protocol (reversed-phase (RP)-HPLC and capillary zone electrophoresis) was developed and validated for monitoring of meloxicam concentration in the presence of its photodegradation products. Fractional factorial design was employed in order to investigate the effects of pH, irradiation time, UV light intensity, TiO2NP loading, and initial meloxicam concentration on the efficiency of the process. The light intensity was found as the most significant parameter followed by irradiation time and concentration, respectively. The most influencing interactions were noted between irradiation time-concentration and irradiation time-light intensity. The kinetics of meloxicam degradation was investigated at the optimum set of experimental conditions. The protocol was successfully applied for treatment of incurred water samples collected during various cleaning validation cycles. A percentage degradation of 77.34 ± 0.02 % was achieved upon irradiation of samples containing 64.57 ± 0.09 μg/mL with UV light (1012 μW/cm(2), 8 h) in the presence of 0.4 mg/mL TiO2NP at pH 9.0 ± 0.05. Treatment of wastewaters collected during the cleaning validation of each product separately rather than the combined waste should result in a significant improvement in the economics of pharmaceutical wastewater treatment. This could be attributed to the relatively small waste volumes and the ability to tailor the experimental conditions to achieve maximum efficiency.