Investigating the Effect of TiO2 Concentration on the Photocatalytic Degradation of Diphenhydramine in Wastewater

Overview

Many pharmaceutical pollutants, such as diphenhydramine (DPH), commercially sold as Benadryl, can pass through wastewater treatment plants and accumulate in water bodies, where aquatic life, including fish and other organisms, may be affected. The present study deals with photocatalysis, a process in which ultraviolet (UV) light degrades substances with the aid of a catalyst to speed up the reaction. The present study evaluates how the concentration of the catalyst, Titanium Dioxide (TiO2), affects the degradation of DPH, including the effects of the resulting treated water on the behavior of zebrafish (Danio rerio). To evaluate the catalyst, samples of DPH at 8 ppm were exposed to UVA light with concentrations of Titanium Dioxide at 0, 10, 50, and 100 ppm. After degradation, the solution was tested via HPLC (high-performance liquid chromatography), then diluted to 25% and exposed to zebrafish for 24 hours to assess harmful byproducts. Results indicated that TiO2 concentrations were minimally relevant, with all samples exhibiting between 85% and 90% degradation, except the 50 ppm sample, which had roughly 55% degradation. Exposed zebrafish showed minimal abnormalities, except at 50 ppm, where they exhibited irritated gills and erratic movement. These results suggest that under optimal conditions, even low catalyst concentrations will be effective in degrading pharmaceutical pollutants. Further work should be dedicated to identifying optimal catalyst concentrations.

Competition history

• CSEF 2026 Environmental Engineering (Senior Division) · Entry S-11-44

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