Combined hydrodynamic cavitation and advanced oxidation process for the degradation of hexamethyl pararosaniline...

Wastewater produced by the Textile industry contains dyes, aromatic, phenolic and various complex compounds which seriously harm the environment due to their high toxicity and carcinogenicity. The dyes found in wastewater are the ones frequently used to add colour to various industrial processes. The present study investigates the degradation of hexamethyl pararosaniline chloride (HPC) dye using hydrodynamic cavitation (HC) along with other oxidants. In an HC reactor, the effect of two different cavitating devices venturi and orifice and its combined effect with ZnO, H₂O₂, KPS, ZnO + H₂O₂ for the degradation of HPC have been investigated in detail. The effect of several operating parameters such as inlet pressure (3-7 bar), temperature (25-55 °C), initial concentration (50-300 mg/L) and initial pH (2-7) with respect to cavitation time has been analysed based on the removal of colour, TOC and TN. At the optimum initial dye concentration of 100 ppm, a pH of 5, a temperature of 35 °C and a pressure of 4 bar the maximum removal of TOC was found to be 46.4% and 28.4% for the venturi and orifice plate, respectively, for 120 min of treatment time. The study also focused on the combined oxidation approaches and compared that with the individual process. The extent of HPC mineralization rose from 46.4% for only HC to 67.3% and 43.6% for the combined HC + H₂O₂+ ZnO and H₂O₂ + ZnO, respectively. Overall, it can be concluded that hydrodynamic cavitation-based combined treatment methods are very effective for the degradation of hexamethyl pararosaniline chloride dye.