In heterogeneous catalytic
ozonation, surface properties including pHpzc and the density of the
hydroxyl groups on catalyst’s surface have an important function in the ozonation
process. Surface of metal oxides would absorb water molecules due to their
unsaturated electrons which cause the formation of hydroxyl groups on the
surface. Solution pH is one of the most important factors affecting the surface
properties of metal oxides including -Al2O3. The surface hydroxyl groups
showed different charge properties at different solution pH 21,
22. Therefore, pH of solution is one of main effective
factors in metal oxides such as -Al2O3 and ozone decomposition. Fei
et al. 23 studied the influence of -Al2O3 surface properties on
catalyzed ozonation of 2,4,6-trichloroanisole (TCA). They found that the
solution pH was more effective on the rate of catalytic ozonation of TCA in the
presence of -Al2O3. As when solution pH is
closed to pHpzc of the -Al2O3, the oxides revealed the
maximum effect on ozone. Therefore, zero charge surface of -Al2O3 was more active than the electropositive
or electronegative surface in catalytic ozonation of TCA. Hence, based on the
results of our study, according to the pHpzc of alumina (8.6) and
due to the economic problems caused by the increasing pH, the more experiments
were carried out at pH of 8. Also, the effects of different pH (3, 8, and 10)
resulted in drastic changes in the color of PCP solution during ozonation that
is consistent with the result of Hong et al. 19. In their study and within the first 7 min of ozonation,
color of PCP solution was shifted from yellow to red due to the production of
ketones and kinone compounds, and then within 45 min, the color intensity of
the solution was gradually reduced. They also assessed the change in color of
the solution by changes in the optical absorption spectrum and indicated that
optical spectra and changes in its absorption is quite different at various pH
points during ozonation caused by generation of byproducts and balance of
organic acids at different pHs. 

Go Top

I'm Rita!

Would you like to get a custom essay? How about receiving a customized one?

Check it out