Doctor of Philosophy
Chemical and Biochemical Engineering
Dr. Ajay K Ray
Diclofenac (DCF), a widely used non-steroidal anti-inflammatory drug (NSAID), is a commonly detected substance that readily accumulates in tissues of aquatic fish and poses a threat to wildlife and freshwater quality. Advanced Oxidation Processes (AOPs) have been explored as an alternative method for complete mineralization of DCF as conventional treatment methods are inadequate for treatment of trace contaminants.
This study employs a semi-batch, swirl-flow, monolithic type photocatalytic reactor to determine intrinsic kinetic parameters of DCF mineralization, in an immobilized system under both UV and visible radiation. The goal of this work to determine true kinetics of DCF, after correcting for external mass transfer resistance that exists when catalysts is immobilized, as a function of various operating parameters such as flow rate, catalyst loading, pH, light intensity, initial concentration, and photocatalyst type.
This study also utilized an innovative method of solar-activation of TiO2 using Eosin-Y dye for the degradation of DCF. Furthermore, the study incorporated a central composite design (CCD) to optimize the dye concentration and estimated the cost for the present process. Optimized parameters for light intensity (750 mW/cm2), Eosin-Y dye concentration (2 mg/L), TiO2 loading (37.5 mg/cm2) and DCF concentration (25 mg/L) were determined by means of a CCD study. A cost estimation for the materials used for the current process was also performed. It was determined that the additional cost of using 4 ppm instead of 2 ppm to achieve only 10% more DCF degradation is not warranted and would require additional treatment to remove subsequently formed halogenated compounds.
In the last part of this thesis, in order to determine mechanism of degradation of DCF, intermediate products were identified. 22 different intermediate products were found during the visible light photocatalytic degradation of DCF using EY-sensitized TiO2 at the optimized conditions. Out of the 22 intermediates, 19 of the transformed products were identified. Toxicity analysis of the treated and untreated samples of DCF were also assessed. The treated samples indicated an increase in toxic effect to Daphnia magna compared to the untreated DCF solution.
The objective and significant contribution of this study lies in (1) obtaining true kinetic data independent of reactor types, (2) incorporation CCD to optimize the reaction operating parameters, (3) cost estimation of the present process, and (4) identification and toxicity analysis of DCF intermediates formed during the optimized process.
Hashim, Noshin, "Visible Light Driven Photocatalysis for Degradation of Diclofenac" (2016). Electronic Thesis and Dissertation Repository. 3736.