Development of hybrid amine-functionalized diatom-based materials for efficient formaldehyde adsorption under dry and humid conditions

Diatomite was functionalized with 3-aminopropyltriethoxysilane (APTES) to develop efficient adsorbents for formaldehyde removal. Two APTES grafting strategies were used to optimize adsorbent performance: APTES grafting on diatomite (N/Dt) and APTES xerogel growth on diatomite (NX/Dt). Specific surface area and pore volume of the functionalized diatomite were determined using surface area and pore size analysis. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) was employed to identify the functional groups on adsorbents surface whereas X-ray photoelectron spectroscopy (XPS) was used to characterize surface chemical composition. The adsorption capacity of NX/Dt adsorbent dried under air at 60°C for formaldehyde initial concentration at 3 ppm considerably reached 53.42 mg of formaldehyde per g of adsorbent under humid air (50% of relative humidity) at 23°C. In the same synthesis conditions, this adsorption capacity was 3000 times and 10 times higher than pure diatomite and xerogel without diatomite template, respectively. Adsorption experiments demonstrated that amine-functionalization significantly enhanced formaldehyde uptake compared to bare diatomite, underlining the critical role of surface amine groups in formaldehyde binding. A comparative analysis of the two-functionalization routes revealed measurable differences in adsorption performance, reflecting the influence of synthesis pathway on adsorbent efficiency. The study establishes APTES-xerogel modified diatomite as a promising bio-sourced candidate for formaldehyde capture, providing insights into the optimization of surface modification strategies for air purification applications.