CHAPTER 5
 SUMMARY AND CONCLUSIONS

 Silica-titania composites were made using a sol-gel method that allows the doping

of titania during gelation. The gelation rate was increased by use of acid catalysts and

allowed the composites to be made into pellets with sufficient dispersion of TiO2 within

the silica matrix. Varying the concentration of hydrofluoric acid allowed the

manipulation of pore size.

 Three variables (TiO2 loading, curing temperature, and pore size) were

investigated to determine the best silica-titania composites for a packed column system.

These variables were optimized based upon destruction and adsorption studies and the

gels were characterized by surface area and XRD analysis. Reactive red dye (RR) was

chosen for its non-photolytic behavior in the analysis of photocatalytic ability for the

destruction studies and crystal violet dye was chosen because of its cationic nature for the

adsorption studies.

 An optimal loading of 12% TiO2 was chosen based upon the results of studies

involving the destruction of RR and adsorption of CV. At higher loadings, it was

observed that the titania is agglomerating during mixing, limiting the effective surface

area available for reactions on its surface. Also, there was no trend with BET surface area

on a volume basis versus titania loading. In addition, the adsorption studies revealed a

plateau in uptake beginning at 12% TiO2.

 A curing temperature of 800C showed the largest effects (a decrease of over 80%

destruction) on photocatalytic ability. At this temperature, the surface area decreased and