Effects of biomass pre-pyrolysis and pyrolysis temperature on magnetic biochar properties

•Rattan was used as a biomass feedstock for production of magnetic biochar (MB).•Pre-pyrolysis and pyrolysis temperature affects the physicochemical properties of MB.•Rattan sawdust (RS) as carbon source has a lower MB yield.•The magnetic media dispersed more uniform on the surface of MB from RS.

To evaluate the effects of biomass pre-pyrolysis and pyrolysis temperature on magnetic biochar (MB) properties, MB composites were fabricated from rattan sawdust (RS) and rattan charcoal (RC) through simple iron salt impregnation and subsequent pyrolysis under different temperatures (600-900 °C). Characterization analysis revealed that pyrolysis procedure greatly affects the physicochemical properties of final products. Magnetite dominates the crystal phases of the MB pyrolyzed at 600-800 °C and the Fe (III) species in MBS (MB from RS) are easier to be reduced into wüstite. Raising the pyrolysis temperature to 900 °C or increasing the molar ratio of Fe2+-Fe3+ are effective ways to promote the formation of α-iron for both MBS and MBC (MB from RC). Although the MBS yield is lower than that of MBC, the magnetic media in MBS dispersed more uniform on the surface of the biochar matrix. The saturation magnetization decreased from 600 to 800 °C and increased afterward from 800 to 900 °C for MBS, which raised continuously for MBC.