Treatment of ternary dye wastewater by hydrodynamic cavitation combined with other advanced oxidation processes (AOP's)

In this work, the application of hydrodynamic cavitation (HC) and its combination with other advanced processes such as hydrogen peroxide (H2O2), Fenton, photo-Fenton, photolytic (UV irradiation), and photocatalytic process (UV irradiation + TiO2) for the removal of mixed dye (Methylene blue, Methyl orange, Rhodamine-B) from aqueous media was studied. Commercial anatase phase nanosized TiO2 was used as nano-photocatalyst in conjunction with HC process for the decolorization of ternary dye. Effect of different operating conditions such as inlet pressure to the cavitation device (Orifice), initial solution pH, different molar ratio of dye to dosage of H2O2, different molar ratio of FeSO4:H2O2 was studied in combination with HC process. The degradation reaction of ternary dye using HC and HC combined with other AOP's followed a pseudo first order reaction kinetics. HC combined with H2O2 shown 100% decolorization in 40 min for the molar ratio of 1:40 (ternary dye:H2O2), whereas the combined approach of HC + Fenton and HC + photo-Fenton process shown 98% and 98.28% decolorization respectively at the dosage of 1:30 molar ratio of FeSO4:H2O2. HC + Photolytic process shown 74.53% decolorization and HC + photocatalytic process shown 82.13% decolorization in 120 min of operation at optimum conditions of pH 3 and 6 bar inlet pressure. The combined approach of HC + H2O2 process has shown the higher synergetic effect 28.97 compared to other hybrid AOP's such as HC + Fenton (6.285), HC + Photo-Fenton (4.923), HC + Photolytic (1.801), and HC + Photocatalytic process (2.11).