Author

Zhong Pan

Date of Award

8-2014

Level of Access

Campus-Only Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Civil Engineering

Advisor

Aria Amirbahman

Second Committee Member

Howard H. Patterson

Third Committee Member

Scott Collins

Abstract

This dissertation consists of two main sections, where the kinetics and mechanisms for the photodegradation of three relevant pharmaceutical compounds in the presence of a novel TiO2-doped low silica X zeolite catalyst are studied.

The first section is a study of the removal efficiency of 17α-ethinylestradiol (EE2) using the novel catalyst. The catalyst was synthesized and characterized using XRD, BET surface analysis, SEM-EDAX, and ICP-OES. The effects of UV light intensities, initial EE2 concentrations, and catalyst dosages on the EE2 removal efficiency were studied. UV-TiO2-LSX system is more efficient to eliminate EE2 in comparison to UV-TiO2 or UV alone. The EE2 photodegradation follows pseudo-first- order kinetics. An empirical kinetic model was used to study the EE2 degradation under various conditions using multiple linear regression analysis. Molecular calculations, HPLC-MS/MS, and the measurement of reactive oxygen species using quenching experiments were applied to undetstand the EE2 degradation mechanism. The results from this study showed that the novel TiO2-doped zeolite catalyst developed here provides a promising application for the UV disinfection process in wastewater treatment plants.

The second section is a study of photodegradation kinetics of three representative pharmaceutical compounds, EE2, atenolol (ATL), and sulfamethoxazole (SMX), in the presence of the TiO2-LSX catalyst in the pH range of 3-10. A kinetic model was developed for the catalytic photodegradation via direct UV photolysis, hydroxyl radicals ( •OH), and carbonate radicals (•CO3-). UV direct photolysis rate constants were obtained by quantum yield and specific light absorption of each compound, the pH dependence of rate constants was attributed to structural variations, acid-base equilibria, the molar absorbance and the quantum yield of each compound. The steady-state •OH and •CO3- concentrations were used to evaluate the role of indirect photodegradation by •OH and •CO3-. The pH dependence of •OH and •CO3- production rates was related to the catalyst’s surface charge as determined by surface complexation modeling and considering electrostatic corrections. The proposed kinetic model successfully predicted the pH dependence of the photocatalytic degradation of the compounds used here; the modeling framework may be extended to evaluate catalytic photodegradation rates in engineered systems involving other catalysts and organic compounds.

Share