Degradation of formaldehyde by photo-Fenton process over n-ZVI/TiO₂ catalyst

The degradation of formaldehyde in a photo-Fenton reaction was studied using n-ZVI/TiO₂ as the catalyst. The effects of %n-ZVI loading, catalyst dosage, H₂O₂, and pH on formaldehyde degradation were studied. The n-ZVI/TiO₂ catalysts were prepared by impregnation with chemical reduction, and their catalytic activity was evaluated in a batch reactor under UVC light. Transmission electron microscopy (TEM) was used to determine that the n-ZVI nanoparticle size was 39.41 nm. X-ray photoelectron spectroscopy (XPS) was used to study the oxidation states of 2%n‑ZVI/TiO₂, and the Fe 2p spectrum of 2%n-ZVI/TiO₂ indicated the presence of Fe⁰. The optimal conditions for the complete removal of formaldehyde within 30 min were an n-ZVI loading of 2 wt.%, a catalyst dosage of 0.5 g/L, 30 mM H₂O₂, and an initial pH of 3. After the reaction, the C-H functional group of formaldehyde was not observed due to the ^•OH radicals generated by Fe⁰ and H₂O₂ attacking the formaldehyde molecule. Moreover, no Fe leaching was observed, presenting an advantage compared with homogeneous Fe catalysts. Therefore, 2%n‑ZVI/TiO₂ shows excellent potential as a photo-Fenton catalyst for the environmentally friendly degradation of formaldehyde.