Low Grade Limonite Tailings Combined Catalyst for Formaldehyde Purification at Room Temperature

The application and performance of low-grade limonite tailings (LT) from Yeshan Iron Mine (Tongling, China) were investigated for the formaldehyde purification at ambient temperature. According to the composition analysis of the tailings, the presence of minerals like nanoneedle hematite and quartz with a great specific surface area is suitable as a catalyst carrier. In this paper, birnessite (Bir) was loaded onto the surface of LT particles via chemical reduction to prepare a catalyst for formaldehyde removal with different manganese loads (x-Bir/LT). The results show that the catalyst has a good formaldehyde degradation ability. The removal efficiency of 27.3-Bir/LT is still 97.2% after 600 min at an initial formaldehyde concentration of 1.2 mg/m³ and a gas hourly space velocity of 41.6 m³/s, thus having a long-term stability and a water resistance. According to the analysis by in-situ infrared spectroscopy, formaldehyde reacts on the catalyst surface via being adsorbed by surface hydroxyl groups and then oxidized to H⁺ and HCOO^–, which further decomposes into CO₂ and H₂O through hydroxyl and surface reactive oxygen species oxidation. Also, LT provides a large number of L-acid sites for the catalyst, improving the catalytic oxidation performance of the composite catalyst. Using limonite tailings as a catalyst carrier can enhance the catalytic oxidation performance of the composite catalyst. This work provides a technical reference for its application in indoor formaldehyde pollution control.