Optimizing a quad-oxidant hybrid process based on hydrodynamic cavitation and UV radiation for Allura red degradation

This research investigated Allura Red (AR) degradation using a quad-oxidant hybrid process with hydrodynamic cavitation (HC) promoted by ultraviolet radiation (UV) in combination with sodium peroxydisulfate (PS) and hydrogen peroxide (H₂O₂) as chemical agents. The experiments were carried out for 4 L synthetic AR-polluted wastewater containing 25 ppm AR. Optimization was performed using a Box-Behnken design (BBD) with H₂O₂ (0–70 ppm), PS (0–200 ppm), and UV radiation (0–32 W). Response surface methodology (RSM) analysis revealed optimal conditions for the HC/H₂O₂/PS/UV process as 41.3 ppm H₂O₂, 197 ppm PS, and 31.7 W UV power. Under these conditions, 99.23 % decolorization efficiency with a kinetic rate constant (k) of 80.53 × 10⁻³ min⁻¹ and yield efficiency of 9.90 × 10⁻³ mg kJ⁻¹ was achieved. The optimum configuration also resulted in remarkable 74.33 % reduction of Chemical Oxygen Demand (COD) within 120 min. Techno-economic analysis, based on the efficiency-cost ratio (ECR) was conducted on all processes revealed that the ECR of the optimized HC/H₂O₂/PS/UV process was attained at 398.40. To clarify the role of reactive species, the influence of radical scavengers was investigated under the optimized conditions. Decolorization efficiency was reduced to 74.53 % and 53.10 % with the addition of tert-butanol and ethanol, respectively, with corresponding rate constants of 22.8 × 10⁻³ min⁻¹ and 12.62 × 10⁻³ min⁻¹.