Degradation of 2,4-dichlorophenol using combined approach based on ultrasound, ozone and catalyst

The present work investigates the application of ultrasound and ozone operated individually and in combination with catalyst (ZnO and CuO) for establishing the possible synergistic effects for the degradation of 2,4-dichlorophenol. The dependency of extent of degradation on the operating parameters like temperature (over the range of 30-36 °C), initial pH (3-9), catalyst as ZnO (loading of 0.025-0.15 g/L) and CuO (loading of 0.02-0.1 g/L) and initial concentration of 2,4-DCP (20-50 ppm) has been established to maximize the efficacy of ultrasound (US) induced degradation. Using only US, the maximum degradation of 2,4-DCP obtained was 28.85% under optimized conditions of initial concentration as 20 ppm, pH of 5 and temperature of 34 °C. Study of effect of ozone flow rate for approach of only ozone revealed that maximum degradation was obtained at 400 mg/h ozone flow rate. The combined approaches such as US + O3, US + ZnO, US + CuO, O3 + ZnO, O3 + CuO, US + O3 + ZnO and US + O3 + CuO have been subsequently investigated under optimized conditions and observed to be more efficient as compared to individual approaches. The maximum extent of degradation for the combined operation of US + O3 (400 mg/h) + ZnO (0.1 g/L) and US + O3 (400 mg/h) + CuO (0.08 g/L) has been obtained as 95.66% and 97.03% respectively. The degradation products of 2,4-DCP have been identified using GC-MS analysis and the toxicity analysis has also been performed based on the anti-microbial activity test (agar-well diffusion method) for the different treatment strategies. The present work has conclusively established that the combined approach of US + O3 + CuO was the most efficient treatment scheme resulting in near complete degradation of 2,4-DCP with production of less toxic intermediates.