Heterogeneous Catalytic Oxidation of Methyl Orange Dye by Copper(II)–Benzoic Acid Complex/NaHCO₃/H₂O₂ System

Abstract

Azo dye waste water is a serious problem because of the high yield, the low biodegradability and the high toxicity. In this work, the heterogeneous Fenton process was employed to degrade methyl orange (MO) using Copper(II)–benzoic acid (CuBA) as the catalyst in the HCO₃⁻ solution using H₂O₂ as the oxidant. CuBA was prepared by a complexing reaction. It was analyzed by FTIR and catalytic activity. The effects of different parameters on the degradation efficiency of the process were studied. The results were found that 90.8% MO degradation efficiency was achieved within 30 min under the best conditions of initial pH 7.0, 1.2 mM of CuBA, 25 mg/L of MO, 10 mM of NaHCO₃ and 0.40 g/L (m/V) of H₂O₂ at 40°C. The kinetics of degradation of MO followed first-order reaction kinetics. A possible pathway of MO degradation was also proposed based on the detected intermediate products by UV-Vis, IR, mass spectrometry. MO was effectively degraded by CuBA/NaHCO₃/H₂O₂ under the neutral and alkalic conditions. The CuBA/NaHCO₃/H₂O₂ system overcomes the two problems faced by the homogeneous Fenton process.