Decolorization of Congo red via hydrodynamic cavitation in combination with Fenton’s reagent

[Display omitted] •HC in combination with Fenton’s reagent results in 70 % decolorization of Congo red.•Effects of parameters and interactions are investigated using RSM.•Synergistic coefficient and yield efficiency of the combined process are determined.•Tank-in-series model with two tanks almost fits the HC reactor. Congo red is a highly toxic diazoic dye used in textile industries. In this work, the decolorization of Congo red was performed using hydrodynamic cavitation (HC) individually and in combination with H2O2, FeSO4, and Fenton process. Response surface methodology (RSM) was used to design experiments and model the influence of parameters and interactions. Solution initial pH (3–10), H2O2 concentration (0−1000 mg L−1), and FeSO4 concentration (0−50 mg L -1) were selected as the parameters of the experimental investigation. A maximum decolorization of 70 % was achieved using HC in combination with Fenton’s reagent at a H2O2 concentration of 1000 mg L−1, a FeSO4 concentration of 25 mg L−1, and an initial pH of 3 within 60 min. A synergistic coefficient of 3.22 and a yield efficiency of 8.3 × 10-3 mg kJ-1 were obtained for the combined process of HC and Fenton’s reagent. The flow behavior of the HC reactor was investigated using the residence time distribution (RTD) analysis for the first time, and the results demonstrate that the tank-in-series model with two tanks almost fits the HC reactor.