shows that with TiO2dosage up to 1.2 g/l, the degrada-tion increases and then decreases gradually with increasingdosage. The similar effect is observed for ZnO. Fig. 6 shows thatwith ZnO dosage up to 0.8 g/l the degradation increases andthen decreases gradually at 35◦C temperature and 120 min ofreaction time. The linear regression shown in both Figs. 5 and 6shows a gradual increase of degradation with an increase incatalyst dosage. This behavior (saturation effect) of the cata-lyst is not surprising and is in agreement with the findings