Degradation of azo dyes using hydrodynamic cavitation and external oxidants

Abstract

Hydrodynamic cavitation (HC) with an orifice as the cavitating device was used to study the degradation of methyl orange dye. The operating parameters of the process, such as pH and inlet pressure, were optimized. The effect of hydroxyl radical promoters like Fenton oxidation and hydrogen peroxide (H2O2) on the extent of degradation was also investigated. It has been observed that acidic conditions (pH 2) favor the degradation of methyl orange. The combined effect of hydrodynamic cavitation with hydrogen peroxide was investigated at the solution’s natural pH and an optimized solution pH 2. Maximum degradation of 99.2% was observed at natural pH, whereas complete degradation of methyl orange dye was observed at pH 2 with 8 ml/L of hydrogen peroxide addition. The hybrid process of HC/Fenton and HC/H2O2 showed the highest efficiency for the degradation of methyl orange with a minimum energy requirement (0.11 kWh) and operational cost (USD $ 0.0062/L).

Keywords

• methyl orange
• hydrodynamic cavitation
• hydrogen peroxide
• fenton oxidation
• degradation