Heterogeneous catalytic wet peroxide oxidation of simulated phenol wastewater by copper metal–organic frameworks

Abstract

Two different porous copper metal–organic frameworks (Cu-MOFs) named as Cu₃(BTC)₂ and Cu(BDC) were synthesized and applied as heterogeneous catalysts for the catalytic wet peroxide oxidation (CWPO) of simulated phenol wastewater (100 mg L⁻¹). The materials were characterized using X-ray Powder Diffraction (XRD), Fourier Transform Infrared (FT-IR) spectroscopy, Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray (EDX) spectroscopy. By comparison, the Cu(BDC) exhibited a better catalytic degradation performance. and was selected for further experiments. Several parameters including temperature, H₂O₂ dose, catalyst dose and initial pH of the phenol wastewater which could affect the catalytic degradation efficiency by the Cu(BDC) were investigated. Under optimum conditions, a phenol conversion of 99% and a COD (Chemical Oxygen Demand) removal of 93% were achieved. The degradation of phenol solutions of different concentrations (100 to 1000 mg L⁻¹) was also carried out. No matter whether a low or high concentration of the phenol solution was used, satisfactory results with a phenol conversion of 99% and a COD removal of over 90% were obtained. After being reused twice, the Cu(BDC) still maintained a good catalytic performance with a phenol conversion of 99% and a COD removal of over 85%. Like other copper catalysts, the mechanism of the degradation process was a hydroxyl radical mechanism. The leaching of Cu²⁺ was also monitored by Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) and a negligible release of copper (7 ppm) was observed. Overall, Cu-MOFs could be promising heterogeneous catalysts for the catalytic oxidation of phenol with H₂O₂ as the oxidant.