Fig. 7. Degradation of VB and DR dye treated with different process (a) 10 × 10−5 M dye solution, ZrO2 NPs is 30 mg, US irradiation (b) 10 × 10−5 M dye solution, ZrO2 NPs is 30 mg, UV–visible irradiation.Figure optionsDownload full-size imageDownload as PowerPoint slide
3.3. Effect of pH
Fig. 8. Effect of Tubastatin A on degradation of VB (a) under UV–visible irradiation (b). Under US irradiation.Figure optionsDownload full-size imageDownload as PowerPoint slide
Fig. 9. Effect of pH on degradation of DR (a) UV–visible irradiation. (b) Under US irradiation.Figure optionsDownload full-size imageDownload as PowerPoint slide
3.4. Effect of catalyst amount
Fig.10. Effect of catalyst dose on (a) degradation of VB (b) degradation of DR.Figure optionsDownload full-size imageDownload as PowerPoint slide
3.5. Effect of initial concentration of dye solution
The sonocatalytic or photocatalytic degradation of VB and DR were carried out at various initial concentrations ranging from 10 × 10−5 M to 15 × 10−5 M using catalyst dosage (ZrO2 NPs) of 30 mg at initial pH of 8 (VB) and 4 (DR) with ultrasonic frequency of 50 KHz or UV–visible irradiation. It was found that the degradation ratio was inversely proportional to the initial concentration of dyes, irrespective of the energy source used. As it can be seen in Fig. 11 and Fig. 12, the efficiency of ZrO2 NPs was found to decrease with an increase in the initial dye concentration of the VB and DR. This behavior can be explained on the basis that when the initial concentration of dye increases, the OH radical ion concentration is reduced correspondingly, so the steady-state concentration of OH radicals in US-ZrO2 NPs causes the degradation efficiency of VB and DR to reduce  and .