A novel magnetic biochar from spent shiitake substrate: characterization and analysis of pyrolysis process

A novel magnetic biochar was obtained via pyrolysis of Fe(NO 3 ) 3 -impregnated spent shiitake substrate (SSS). The product was characterized by X-ray diffraction (XRD), vibrating sample magnetometer (VSM), N 2 -adsorption, scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) analysis. The pyrolysis process was investigated by thermogravimetric analysis (TGA) and XRD, and the pyrolysis kinetic was analyzed via Coats-Redfern method. Experimental results demonstrated that the magnetic FeO·Fe 2 O 3 crystals and porous char structure were effectively formed via pyrolysis, and the magnetic biochar had a saturation magnetization value of 20.83 emu/g. The product had a surface area of 177 m 2 /g and a total pore volume of 0.188 cm 3 /g, respectively, and it consisted basically of micropores with diameter of 1.5 nm and mesopores with diameter between 2 and 10 nm. Moreover, Fe can decrease the thermal stability of SSS, and the magnetic crystals were mainly formed between the temperature region of 420 and 530 °C. In addition, the activation energy needed to break down the structure of SSS was lowered by 12.12 kJ/mol with the presence of Fe.