Decolorization of reactive Red 120 by a novel hybrid hydrodynamic cavitation and non-thermal plasma reactor

• Hybrid hydrodynamic cavitation non-thermal plasma reactor successfully developed. • Water matrix plays an important role in the production of hydrogen peroxide. • Rotor’s frequency and plasma voltage discharge increase oxidation potential. • Reactive Red 120 removal follows pseudo first-order kinetics. • Under optimal experimental conditions, the energy yield is 787 mg/kWh. The treatment of dye-contaminated wastewater remains a significant challenge for environmental management due to the high stability and persistence of many azo dyes. The purpose of this study was to develop and evaluate a novel hybrid rotor–stator hydrodynamic cavitation non-thermal plasma device designed to enhance the decolorization of Reactive Red 120. The configuration integrates atmospheric-pressure plasma directly into a cavitating flow field, attempting to increase gas–liquid interfacial contact and promote mass transfer of reactive species into the liquid. The device performance was investigated by assessing the effects of various parameters on H 2 O 2 production, pH, conductivity, and energy consumption. The results show generation of reactive species at all tested parameters, with higher H 2 O 2 production in deionized compared to tap water. Rotational speed, discharge voltage and air flow rate all influenced H 2 O 2 production and the highest concentration achieved was 9.9 mg/L in 15 min. Decolorization was evaluated at three initial concentrations and followed apparent pseudo first-order kinetics, with higher degradation rates observed at lower initial dye concentrations (0.0273, 0.0234 and 0.0168/min at 25, 50 and 100 mg/L, respectively). The study demonstrates that coupling of hydrodynamic cavitation with non-thermal plasma produces synergistic effects and has potential to treat complex wastewaters.