Hybrid treatment strategies for 2,4,6-trichlorophenol degradation based on combination of hydrodynamic cavitation and AOPs

Utilization of hybrid treatment schemes involving advanced oxidation processes and hydrodynamic cavitation in the wastewater treatment forms the prime focus of the present work. The initial phase of the work includes analysis of recent literature relating to the performance of combined approach based on hydrodynamic cavitation (HC) for degradation of different pollutants followed by a detailed investigation into degradation of 2,4,6-trichlorophenol (2,4,6-TCP). The degradation of the priority pollutant, 2,4,6-TCP, using combination of HC based on slit-venturi used as the cavitating device, ozone and H2O2 has been investigated. The effect of operating pressure (2-5 bar) and initial pH (3 −1 1) have been investigated for the degradation using only HC. The degradation using only ozone (100-400 mg/h) and only H2O2 has also been studied. The efficacy of the combined operation of HC + O3 at different ozone flow rates (100-400 mg/h) and the combined operation of HC + H2O2 at different loadings of H2O2 (2,4,6-TCP:H2O2 as 1:1-1:7) have been subsequently investigated. The degradation efficacy has also been established for the combined treatment strategies of O3 + H2O2 and HC + O3+H2O2 at the optimum conditions of temperature as 30 °C, inlet pressure of 4 bar and initial pH of 7. Extent of 2,4,6-TCP degradation, TOC and COD removal obtained for HC + O3 process were 97.1%, 94.4% and 78.5% respectively whereas for O3 + H2O2 process, the values were 95.5%, 94.8% and 76.2% and for HC + O3 + H2O2 process the extent of reduction were 100%, 95.6% and 80.9% in the same order. The combined treatment approach as HC + O3 + H2O2 was established as the most efficient approach for complete removal of 2,4,6-TCP with near complete TOC removal.