Degradation of Methyl Orange Using Hydrodynamic Cavitation and Advanced Oxidation Processes | ||
| Egyptian Journal of Chemistry | ||
| Articles in Press, Accepted Manuscript, Available Online from 18 November 2025 | ||
| Document Type: Original Article | ||
| DOI: 10.21608/ejchem.2025.419996.12282 | ||
| Authors | ||
| Ghada E. Heikal; Mohamed Hani* ; Ahmed Abdo | ||
| Environmental Engineering Department, Faculty of Engineering, Zagazig University, Zagazig, Egypt | ||
| Abstract | ||
| This study systematically evaluated the efficiency of hydrodynamic cavitation (HC) as an advanced oxidation process for degrading synthetic dye wastewater. Methyl Orange (MO), a representative azo dye known for its toxicity, stability, and resistance to conventional biological treatment methods, was selected as the target pollutant. A custom-designed hydrodynamic cavitation reactor equipped with modular orifice plates of varying geometries was used as the cavitation device. Two sets of geometrically distinct orifice plates (circular and square) were used. Each set consisted of five plates with varying orifice areas and perimeters to assess the influence of geometry on cavitation performance. The influence of key operational parameters was also investigated, including an inlet pressure, pH, an initial dye concentration, and a treatment duration on the overall degradation efficiency. Of the tested conditions, the square orifice plates consistently demonstrated a superior performance in comparison with their circular counterparts, with the highest dye removal efficiency of 91.08% under the optimal conditions. This improvement is attributed to the increased turbulence and the intensified bubble collapse dynamics. The optimal dye removal was achieved at an inlet pressure of 5 bar and pH of 3, with efficacy decreasing at higher dye concentrations and improving with longer treatment durations. In order to enhance the hydroxyl or sulfate radical generation, the HC process was investigated with three commonly used advanced oxidation processes (AOPs): hydrogen peroxide (H2O2), sodium persulfate (Na2S2O8), and zero-valent iron (Fe0). The results demonstrated clearly that combining hydrodynamic cavitation with advanced oxidation processes significantly improved the Methyl Orange removal, especially when the hydrogen peroxide was used. Of the all tested additives, H2O2 showed the highest degradation efficiency of 98.95% at H2O2 loading of 250 mg/L, far outperforming sodium persulfate and zero-valent iron. This improvement is attributed to the synergistic action between HC and H2O2, which led to faster and more comprehensive dye breakdown. For HC combined with H2O2, Na2S2O8, and Fe0, cavitation yield, energy consumption, and treatment cost estimation were investigated. The results confirmed that HC combined with H2O2 had the highest cavitation yield of 7.5 × 10-5 mg/J at H2O2 loading of 250 mg/L and optimum operational conditions, including an inlet pressure of 5 bar, an initial MO concentration of 40 mg/L, pH of 3, and a treatment time of 60 minutes. Also, the combination of HC and H2O2 had the lowest treatment cost of 8.4 × 10-3 EGP/mg at H2O2 loading of 150 mg/L in comparison with other combinations with Na2S2O8 or Fe0 at the optimum operational conditions. Overall, the findings suggest that hybrid systems based on HC and AOPs (particularly those involving hydrogen peroxide) offer a promising approach for treating industrial wastewater containing synthetic dyes. | ||
| Keywords | ||
| Cavitation yield; Energy consumption and cost estimation; Hydrogen peroxide; Methyl Orange; Orifice plate; Sodium Persulfate; Zero-valent iron | ||
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