Heterogeneous photo-Fenton degradation of formaldehyde using MIL-100(Fe) under visible light irradiation

Removal of toxic formaldehyde from environmental waters is crucial to maintain ecosystem sustainability and human health. In this work, MIL-100(Fe) as a heterogeneous Fenton-like photocatalyst was used for the treatment of formaldehyde-contaminated water. The MIL-100(Fe) was synthesized via a facile solvothermal method and fully characterized using different spectroscopic and microscopic techniques. Based on the results, the formation of highly porous, crystalline, and stable visible light-responsive MIL-100(Fe) was confirmed. The Fenton-like photocatalytic efficiency of the MIL-100(Fe) toward the degradation of formaldehyde was then studied under visible light irradiation. For this purpose, the effect of initial concentration of formaldehyde, photocatalyst dose, H2O2 concentration, solution pH, and contact time on the removal efficiency of the MIL-100(Fe) was investigated using central composite design. The obtained results showed that the removal efficiency of the MIL-100(Fe) is significantly affected by the initial concentration of formaldehyde. A second-order model with R2 = 0.93 was developed for the system that was able to adequately predict the percentage removal of formaldehyde by the MIL-100(Fe) under different experimental conditions. According to the numerical optimization results, by using 1.13 g L−1 photocatalyst and 0.055 mol L−1 H2O2, 93% of formaldehyde can be removed after 119 min from an aqueous solution containing 700 mg L−1 of formaldehyde at pH 6.54.