Rapid degradation of the anionic surfactant sodium dodecyl benzene sulfonate via a hybrid UV/hydrodynamic cavitation system with H2O2 and persulfate.

Removing organic pollutants like the anionic surfactant sodium dodecyl benzene sulfonate (SDBS) from wastewater is challenging due to its environmental persistence and toxicity. This study employed a hybrid system combining hydrodynamic cavitation, ultraviolet (UV) radiation, and the oxidants hydrogen peroxide (H2O2) and sodium persulfate (PS) to degrade the surfactant. Experiments were conducted with an initial SDBS concentration of 10 mg·L⁻1, wastewater volume of 4 L, pressure of 3 bar, temperature of 30 ± 2 °C, and reaction time of 40 min. A Box‑Behnken design was used to optimize parameters including UV radiation power (0-32 W), H2O2 concentration (100-300 mg·L⁻1), and PS concentration (100-300 mg·L⁻1). Optimal conditions (210 mg·L⁻1H2O2, 182 mg·L⁻1 PS, 16 W UV) resulted in 98.2% pollutant degradation and a pseudo‑first‑order rate constant of 100.5 × 10⁻3 min⁻1. The combined process (HC/UV/H2O2/PS) showed the highest efficiency, the lowest electrical energy per order (EE/O = 31.9 kWh·m⁻3), and an energy consumption ratio (ECR) of 593.0. Increasing the initial SDBS concentration from 10 to 40 mg·L⁻1 reduced degradation to 66.92% and the rate constant to 62.3 × 10⁻3 min⁻1. Radical scavenger tests indicated that 83.5% of the degradation was attributed to radical oxidation; of this fraction, hydroxyl radicals contributed 81.33% and persulfate radicals contributed 18.67%, while the remaining 16.5% was due to direct cavitation and UV radiation effects.