approximately 24 hours and analyzed using nitrogen adsorption isotherms. The average

pore size was calculated by dividing the pore volume by the surface area. Pore size

distribution curves were also attained and coincided with the calculated pore size.

 XRD (X-ray diffraction) analysis was performed on cured gels to determine the

phase of titania, anatase or rutile. These gels were cured at temperatures up to 8000 C as

an additional curing step after the regular drying schedule. The analysis was performed

on a APD 3720 from Philips Analytical (Almelo, Netherlands). The reflections of the two

crystalline TiO2 phases, anatase (20 = 25.3) and rutile (20 = 27.4), were taken from

Grieken et al. (2002).

 3.3 Column Performance Studies

 The purpose of these studies was to show the performance of the pellets in a

regenerative system, which places equal significance on the adsorption of a contaminant

as well as the feasibility of the contaminant to be mineralized. A cylindrical column (6

inches in length, 0.5 inch diameter) with a porous frit was filled with 10 mL of pellets.

The column setup is shown in Figure 3-1. A CV dye solution of 2 mg/L was pumped

through the column until the effluent concentration equaled the influent concentration.

Then the CV pump was turned off and the deionized water and UV light was turned on

(flux = 1.1 mW/cm2) for a set time (e.g., one hour). During this regeneration time, the

water was pumped through the column to provide the reactants (02, H20) required for

photocatalysis. After the regeneration time, the CV pump was turned back on. This cycle

was continued several times for separate packed columns of 140 A gels and 30 A pellets,

both loaded with 12% TiO2. The flowrate for both the deionized water and CV dye was 8

mL/min.