Facile fabrication of iron-modified biochar as a renewable adsorbent for efficient siloxane (L2) removal

Abstract

The volatile methylsiloxanes (VMS) in biogas significantly hinders the application. Thus it is vital to identify new materials for achieving the effective removal of VMS from biogas. In this study, iron-modified biochar (FeMBC) materials have been prepared via an impregnation and calcination approach using biochar and Fe (III)-ethanol solution for effective removal of hexamethyldisiloxane (L2). The developed FeMBC materials have been characterized by N2-adsorption/desorption, FTIR, SEM-EDS, XRD and XPS. The results revealed that the as-prepared FeMBC materials possessed a well-developed microporous structure. Among these materials, FeMBC-3 exhibited the highest specific surface area (1068.43 m2 g−1) and micropore volume (0.51 cm3 g−1), leading to an adsorption capacity of 356.4 mg g−1 using 83.82 mg L−1 of L2 with dry N2 as the carrier gas. It was concluded that L2 adsorption capacities were strongly related to the texture of FeMBC materials, especially the pore volume and surface area of micropores. In addition, the influence of temperature and inlet concentration was investigated using dynamic adsorption experiments, and the data were fitted by applying Yoon-Nelson model, Langmuir-Freundlich thermodynamic model and kinetics models, obtaining the thermodynamic and kinetic parameters. The results revealed that the adsorption of L2 on FeMBC-3 was a spontaneous and exothermic process. Finally, regeneration of FeMBC-3 could be swiftly achieved by heating at 100 °C, with the adsorption capacity for L2 remaining stable in the subsequent continuous dynamic adsorption experiments. Thus, the as-prepared FeMBC material represents a promising siloxane adsorbent for biogas up-gradation.