Intensifying Orange G decolorization through hydrodynamic cavitation with a swirling jet-induced reactor and sodium persulfate process: Kinetics, optimization, and synergistic effects

Dye removal from wastewater is critical due to the adverse effects on aquatic ecosystems and the environment. This study investigated hydrodynamic cavitation (HC) in a swirling jet-induced reactor, both alone and coupled with sodium persulfate (PS), for the decolorization of Orange G. A Design-Expert-based design of experiments was used to evaluate the effects of initial pH, inlet pressure, and initial dye concentration on HC performance. According to the results, initial pH was the most influential factor. Under optimal HC conditions (10 mg/L dye, 4 bar, and pH 3), the maximum decolorization efficiency was 9.78%. In the combined HC–PS process, the effects of pH and PS concentration were examined. Coupling HC with PS substantially enhanced dye decolorization, achieving 93.67% at 10 mg/L dye, 4 bar, pH 5, and 500 mg/L PS. At the optimal operating conditions of each process, the cavitation number, cavitational yield, and energy consumption for HC were 0.28, 0.0173 mg/kJ, and 6331.92 kWh/m 3 .order, respectively. For HC–PS, the cavitational yield increased to 0.166 mg/kJ, a factor of about 9.6, while energy consumption decreased to 236.13 kWh/m 3 .order, corresponding to a 96.3% decrease in energy demand. Under the same operating conditions, the corresponding values are: a 9.4-fold increase in cavitational yield and a 95.9% decrease in energy demand. The decolorization kinetics followed a modified pseudo-first-order model, with rate constants of 0.051 and 0.197 (min -1 ) for HC and HC–PS under their respective optimal conditions. A synergistic index of 5.03 confirmed a strong positive interaction between HC and PS.