M.Sc Thesis

M.Sc StudentBaransi Karkaby Katie
SubjectEffect of Photocatalytic Degration and Adsorption Processes
on the Removal of Phenolic Compounds
DepartmentDepartment of Civil and Environmental Engineering
Supervisors ASSOCIATE PROF. Yael Dubowski


Olive mill wastewater (OMW) represents one of the more challenging effluents demanding treatment, and is also representative of other refractory agro-Industrial effluents. OMW poses a serious environmental problem due to its high chemical oxygen demand, its resistance to biodegradation (incurred mainly by its high content of phenolic compounds), and its seasonal production.

The present study examined the degradation of phenolic compounds by heterogeneous photocatalysis, focusing on OMW. The process is based on photoactivation of TiO2 by UV radiation, which initiates series of reactions that result in production of hydroxyl radicals. These radicals can react with organic compounds adsorbed on or present near the TiO2 surface.

High adsorption of the pollutants and their derivatives on the TiO2 surface might decrease the efficiency of TiO2 excitation. In order to resolve this problem while working with high pollutant levels, activated carbon was added as a co-adsorbent to TiO2. Activated carbon absorbs the pollutants and their intermediate products in close vicinity to the TiO2 surface thus enabling their transfer to the photocatalytic sites where they are decomposed.

The results of the present study indicate that removal rates of phenolic compounds by either adsorption or photodegradation are higher at lower concentrations. In addition, the pH of the solution was found to significantly impact adsorption capacity, with higher adsorption capacity (and higher photodegradation rate) at low pH (<4.5).  Solar light was shown to be very effective, which might reduce the cost of the treatment. The addition of powdered activated carbon has shown to increase removal efficiency, and therefore, the combination of adsorption processes along with TiO2 photocatalysis has improved photodegradation at low to medium phenolic concentration.

Photodegradation of anaerobicly treated & diluted (1:10) OMW yielded higher removal efficiency of phenolic compounds in comparison to COD removal. Furthermore, a level of 87% removal of total polyphenols from this wastewater was observed after 24 hours of exposure to 365nm UV light (at about 7.5 W m-2).

The results of the study emphasize the potential for combining photocatalysis with TiO2 and adsorption by activated carbon, as a physicochemical process employed for pre or post-biological treatment. Providing such a combination could be a step towards the development of sustainable, reliable and cost-effective technology for the treatment of wastewaters, demonstrating an innately high resistance to biodegradation.