Hybrid photocatalytic/photochemical degradation of 1,2-dichlorobenzene: kinetic, thermodynamic, operating cost, synergism and mineralization study.

This study investigates the combined effects of UV/TiO2 and UV/H2O2 processes on the degradation of 1,2-dichlorobenzene in aqueous media, employing a recycled current photo-reactor equipped with a water jacket. Evaluation of various factors—initial pH, TiO2 dosage, initial H2O2 concentration, pollutant concentration, and temperature—contributed to the optimization of degradation rates and operational costs for both processes. For the degradation of 50 mg/L of DCB, the optimal operating conditions were found to be for UV/TiO2: pH = 3, [TiO2] = 30 mg/L and T = 25 °C, and for UV/H2O2: pH = 3, [H2O2]0 = 350 mg/L and T = 25 °C. After 60 min of irradiation time, the degradation efficiency, pseudo first order rate constant and operational cost value for the UV/TiO2 and UV/H2O2 processes were as 98.9%, 0.0771 min−1, 11.6 $/m3 and 96.3%, 0.0573 min−1, 11.8 $/m3 respectively. Also, thermodynamic parameters of activation energy, enthalpy change, entropy change and standard Gibbs free energy were calculated as 21.78 (kJ/mol), 19.37 (kJ/mol), − 0.20 (kJ/mol K) and 73.34 (kJ/mol at 25 °C) for UV/TiO2 process and 7.62 (kJ/mol), 5.18 (kJ/mol), − 0.25 (kJ/mol K) and 80.14 (kJ/mol at 25 °C) for UV/H2O2 process. The investigation also encompassed the exploration of 13 hybridization scenarios, including UV/TiO2/H2O2 and UV/H2O2/TiO2, revealing notable findings. Notably, a specific hybridization scenario, namely UV/TiO2 (30 mg/L)/H2O2(250 mg/L), demonstrated a significant synergistic effect (29.5%). Evaluating pollutant mineralization unveiled compelling results, with approximately 85% mineralization achieved after 90 min for the UV/TiO2(30 mg/L)/H2O2(250 mg/L) scenario, showcasing a remarkable synergism (44%) in the mineralization process. [ABSTRACT FROM AUTHOR]