Adsorption effect of nitrogen, sulfur or phosphorus surface functional group on formaldehyde at ambient temperature: Experiments associated with calculations

Abstract

Abstract The objectives of this study were to assess the formaldehyde (HCHO) adsorption capacity of doped porous carbon by experiments and theoretical calculations. Nitrogen, sulfur or phosphorus containing porous carbons were prepared with different precursors by activation with KOH at 700 °C and compared with commercial activated carbon (CAC), and used as the low HCHO concentration adsorbents in dry (dynamic) and wet (static) conditions. Results showed that the HCHO adsorption capacity of AC-N (2418.20 m2 g−1) for dynamic (13.60 mg g−1) and static (1.43 mg g−1) was greater than that of AC-S, CAC and AC-P. The specific surface area and the micropores volume were expected to markedly influence the adsorption capacity of HCHO. According to the DFT calculation, the adsorption energy of surface functional groups of phosphorus (−0.53296 eV) was the highest, followed by sulfur (−0.52646 eV) and nitrogen (−0.41246 eV), which indicated hydrogen bond interaction played an important role in the adsorption. In the GCMC slit model, the size of slit pores was positively correlated with the adsorption amount of HCHO. With the increase of the adsorption pressure, the surface functional groups had little effect on the adsorption of HCHO under the same size of the slit pores. Accordingly, for the high HCHO adsorption capacity, specific surface area and pore volume are the primary determinant, while surface functional group is the secondary determinant. This would provide a useful theoretical reference for the doping of polarized activated carbon to adsorb polar gases.