Fabrication of magnetic biochar as a treatment medium for As(V) via pyrolysis of FeCl3-pretreated spent coffee ground

Abstract

This study investigated the preparation of magnetic biochar from N₂- and CO₂-assisted pyrolysis of spent coffee ground (SCG) for use as an adsorption medium for As(V), and the effects of FeCl₃ pretreatment of SCG on the material properties and adsorption capability of the produced biochar. Pyrolysis of FeCl₃-pretreated SCG in CO₂ atmosphere produced highly porous biochar with its surface area ∼70 times greater than that produced in N₂ condition. However, despite the small surface area, biochar produced in N₂ showed greater As(V) adsorption capability. X-ray diffraction and X-ray photoelectron spectrometer analyses identified Fe₃C and Fe₃O₄ as dominant mineral phases in N₂ and CO₂ conditions, with the former being much more adsorptive toward As(V). The overall results suggest functional biochar can be facilely fabricated by necessary pretreatment to expand the applicability of biochar for specific purposes.

Keywords: Adsorption; As(V); Magnetic biochar; Mineral phase change; Reactive gas.