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

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.