Remediation of Water Contaminated with an Azo Dye: An Undergraduate Laboratory Experiment Utilizing an Inexpensive Photocatalytic Reactor

The construction and use of an inexpensive photocatalytic reactor that utilizes titanium dioxide as the photocatalyst for wastewater treatment is described. In these experiments and in supplementary material, students are made aware that a variety of techniques have been developed to treat wastewaters, including those generated by the chemical industry. Water contaminated with the azo dye Congo Red was selected as an example of how one might treat contaminated water from a textile manufacturing facility. These experiments emphasize that, in addition to product development, chemists must also be concerned with waste treatment. A summary of the theory of titanium dioxide-mediated photocatalysis is provided. The phenomenon of photosensitization is also discussed. The usefulness of Congo Red is summarized and a brief history of this dye is given.In addition to being inexpensive, the photocatalytic reactor described is easy to construct and uses a readily available low-wattage fluorescent light. An important feature of this reactor is that the heat generated by the light source is readily dissipated by the water undergoing treatment. Thus no special cooling apparatus is required. One of the most important aspects of this work is that it provides a wide variety of continuing research suggestions that would be suitable and readily accomplished in undergraduate departments and high school laboratories; even those where budgetary priorities are a major concern. Use of this reactor would also enable students to design systems to treat "real-world" wastes, including some that are generated in instructional laboratories.