An-Najah Staff

The photo-catalytic degradation of organic contaminants (such as dyes, insecticides, pesticides, phenols … etc) in water, air and soil using semiconductor oxide photo-catalysts (such as ZnO and TiO2) under direct sunlight are newly emerging practices. This is due to catalyst low costs, use of free sunlight, mild reaction conditions, high photochemical reactivity, low environmental toxicity and catalyst stability to photo-corrosion. In this thesis, photo-degradation of two different organic contaminants in agricultural soil was investigated. Phenazopyridine and phenol were both studied as model contaminants. For this purpose, two different catalyst systems were used namely TiO2 and ZnO powders, commercial and prepared systems. UV-visible spectra, photoluminescence spectra, XRD and SEM imaging were used to characterize both the commercial and prepared catalyst systems. Effects of contaminant concentration, irradiation time, catalytic concentration, pH and soil particle size, on photo-degradation process were studied. Degradation percentage, turnover number, turnover frequency and quantum yield were all calculated to investigate catalyst efficiencies. In case of the phenazopyridine contaminant, the three catalytic systems were used. The TiO2 showed little photo-catalytic efficiency and its efficiency could not be enhanced. Commercial ZnO in phenazopyridine degradation showed higher efficiency. Increasing contaminant concentration lowered the percent degradation. The catalyst amount and irradiation time did not show significant effects on photo-degradation reaction. Using nano-sized ZnO (dry powder and wet spray) did not show significant enhancement compared to the commercial ZnO system. In case of the phenol contaminant, two catalytic systems were used, commercial and nano-sized ZnO. Increasing contaminant concentration, pH value and irradiation time increased the reaction progress until certain limit. Increasing catalyst amount did not significantly affect the photo-degradation process. Nano-sized ZnO particles showed higher catalytic efficiency per gram than the micro-sized counterpart.