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Water quality monitoring throughout the United States has shown that atrazine is ubiquitous in surface and groundwater supplies. Once it is transported to adjacent streams and/or leaches to groundwater, it poses a potential threat to humans and wildlife. A photocatalytic reactor employing a highly pure nano-sized anatase TiO 2  (7 nm) was designed for the photocatalysis of atrazine. Light was delivered to the reactor by an 8 mm corediameter, liquid core optical fiber (LCOF) from a light source. Radiation wavelengths varied from 305 nm to 450 nm. The LCOF was connected to a 40 cm long quartz tube, which was coated with DuraflectⓇ coating material that reflected &gt; 90% of the light between 300 nm and 1,200 nm. Openings, 2 mm wide, were provided by removing the coating around the circumference of the quartz tube every 1.8 cm to allow illumination through the quartz tube into the reactor. A 2 3  factorial design was conducted to determine significant effects of three primary design factors, i.e., pH (6, 7, 10, 12), illumination intensity, and the surface-to-volume (S/V) ratio or diameter (D) of the reactor (5 cm, 7.5 cm, 10 cm, 15 cm), and their interaction on atrazine removal rates. Analysis of variance (ANOVA) of the experimental data indicated that all three factors significantly (α = 0.05) affected the atrazine degradation rate. Increasing the illumination intensity (from 6.5 W/m 2  to 65 W/m 2 ) greatly enhanced the initial degradation rate of the atrazine from 0.2 ppb/min to 10.2 ppb/min. As the reactor surface-tovolume ratio increased from 0.27 cm -1  to 0.8 cm -1 , there was an increase in kinetic rate from 0.23 ppb/min to 10.22 ppb/min. Solution pH influenced the TiO 2  surface charge and the ionic form of atrazine in solution, which resulted in electrostatic repulsion of atrazine from the catalyst surface in the pH range of 5-10. Low initial degradation rates of 0.2-3 ppb/min were obtained at pH levels 10 and above. The adsorption isotherm experiments at pH levels from 5 to 10 indicated that no significant (α = 0.05) adsorption was observed on the TiO 2  surface. The results indicated that atrazine photocatalytic degradation was not a surface phenomenon. Degradation products were also measured by the liquid chromatography/electrospray ionization-mass spectrometry/mass spectrometry (LC/ESI-MS/MS) with time at optimal operating conditions: pH = 7, I = 65 W/m 2 , and D = 5 cm.

Effects of Operational Factors on the Atrazine Degradation in a Fixed Nano-TiO 2 Photocatalytic Reactor