An investigation of the reaction kinetics of photocatalytic wastewater treatment using suspended titanium dioxide catalyst

Abstract

The goal of wastewater treatment is to remove compounds that may be harmful to the natural ecosystem or to humans. Although traditional treatment is fairly effective in meeting water quality standards, current technologies face the challenge of balancing a high removal of these damaging compounds with the addition of chemicals as a part of the very same removal process. In addition, new types of pollutants resistant to conventional treatment techniques are being found in wastewater streams at increasing concentrations. Moreover, traditional treatment technologies, require a large input of energy, emit greenhouse gases, and thus have a detrimental impact on the ecosystems that they intend to preserve. In response to this dilemma, over the past few decades, the scientific community has devoted a special effort in the development of a new technology that harnesses natural sunlight to trigger the water treatment process. Photocatalytic oxidation, as this form of advanced oxidation process (AOP) is known, is characterized by the generation of hydroxyl radicals - one of the most oxidizing agents known in environmental chemistry - which easily attack all types of organic pollutants found in wastewater. However, while this process seems very promising, there are no standard design parameters to accurately model and predict the behavior of a photocatalytic reactor, a situation that prevents its use in full-scale treatment plants. The photocatalytic oxidation of Escherichia coli, methanol, cinnamic acid, and sulfamethoxazole was tested on a laboratory-scale for dependence upon three initial variables. Based on experimental data, a direct dependence was found between the oxidation rate constants and the initial conditions of catalyst concentration and radiation intensity. Experimental results also show that the dependency upon initial pollutant concentration is highly related to the structure of the contaminant. This thesis studies a photocatalytic process using suspended titanium dioxide (TiO2) catalyst. This document reviews the methodology followed to create the experimental framework and conduct the data analysis.