Continuous-Flow Solar-Driven Photocatalysis of Pharmaceuticals in Saline Water Using a Hollow Optical Fiber Reactor: A Process Optimization via a Design of Experiments

Abstract

This study presents the photocatalytic removal of ibuprofen (IBU), one of the most detected pharmaceuticals in aquatic environments over 5% bismuth-doped ceria-titania photocatalyst using solar light. The effects of IBU concentration (5-55 mg/L), pH (3-11), and salinity of the reaction medium (0-10,000mg/L) on the removal percentage of IBU were studied using two-level, full factorial design of experiments to screen for the most influential effects. The degradation of Ibuprofen (IBU) was monitored using a UV/Vis spectrophotometer, and Liquid Chromatography-Mass Spectrometry (LCMS) was used to assess the removal percentage of IBU, while HPLC-DAD was used to screen for intermediates. The ANOVA and the statistical studies gave a linear model with pH as the only significant effect on two responses: 1) removal% by dark adsorption and photocatalysis and 2) removal % by photocatalysis. Therefore, 3-dimensional response surface methodology could not be applied to optimize for the conditions with the obtained linear model. However, the ANOVA proved the validity of the model with a predicted R² of 0.850 for adsorption-photocatalytic removal and predicted R² of 0.805 for photocatalytic removal%. Moreover, the UV absorption spectrophotometry and the HPLC-MS results indicated a slight decrease in degradation by the photocatalyst in saline water compared to deionized water at high initial concentrations, while a slight increase in photocatalytic degradation was observed in saline conditions water compared to deionized water at low initial concentrations. As for the pH, it had the greatest effect on the degradation of IBU. Removals of 99.7-100 % were achieved at low pH conditions. While the studied ranges of the other parameters showed no significant impact on the removal%. Moreover, at low pH conditions and saline conditions, the photocatalysis process was carried in a single capillary reactor. The removal of IBU by the capillary reactor is 9.4% but can be further improved by increasing the residence time and the number of the capillary tubes.

Date of Award	Jul 2021
Original language	American English