Single Step Synthesis of Magnetic Materials Derived from Biomass Residues

Agro-industrial biomass residues (peanut shells, cocoa husks, sugarcane bagasse and coconut mesocarp) were converted into magnetic adsorbents by deposition of maghemite (γ-Fe2O3), employing the combustion synthesis method as a single step route. The resultant magnetic materials were characterized by XRD, TEM, nitrogen adsorption, and magnetization measurements. The magnetic composites are formed by maghemite (γ-Fe2O3), as the major phase, and hematite (α-Fe2O3), as a minor contaminant, both dispersed in carbonaceous matrices, depending on the parent biomass residue. The crystallite size of γ-Fe2O3 was estimated by the Scherrer equation and ranged from 6 to 58 nm, depending on the starting biomass residue. The BET surface areas were relatively low (12 to 58 m2 g−1). The magnetization measurements indicated a decrease in the saturation magnetization with decreasing maghemite crystallite size and with the increase of the carbon content.