Comparison of performances of hydrodynamic cavitation in combined treatments based on hybrid induced advanced Fenton process for degradation of azo-dyes

In the present work, the degradation of azo-dyes in aqueous solutions by using hydrodynamic cavitation is performed. Methyl orange was chosen as colorant model pollutant. During the experimental tests, the effect of various operating parameters on the decolourization efficiency was investigated. In the first series of experiments, the hydrodynamic cavitation was optimized in terms of operating inlet pressure and cavitation number to get the maximum decolorization yields of the dye, at the constant temperature of 20 degrees C and with an initial methyl orange concentration equal to 5 ppm. It was observed that there was an optimum inlet pressure value (4 bar) to get the best decolourization efficiency (about 32%). For the optimal configuration, in correspondence of 4 bar, a first order kinetic equal to 0.0054 min(-1) and a value of electrical energy per order E-EO of 3793.81 kW h m(-3) were calculated. Subsequently, the combined effect of hydrodynamic cavitation and hydrogen peroxide on dye degradation has been studied. The efficiency of the HC-H2O2 system, under optimal conditions, was more than 50% in terms of dye decolourization. Finally, a series of experiments have been performed by combining hydrodynamic cavitation with the addition of hydrogen peroxide and metal ions (iron and nickel) in solution. The dye degradation became greater than 90%; this increase was explained by supposing that an induced advanced Fenton process has been generate thus improving the performance of the entire cavitation system.