Magnetic biochar nanocomposites can be obtained by in-situ co-precipitation of magnetite nanoparticles into carbon-based matrixes prepared by three different procedures:

1. Pyrolysis of sunflower husk (MBCSFH);

2. Hydrothermal carbonization (HTC) of sunflower husk (MHCSFH) and

3. HTC of orange juice residue (MHCOR).

Two biochar materials, namely, sewage sludge biochar and woodchips biochar, can be prepared at two different temperatures, viz., 450 and 700 °C. These biochars is further modified with magnetic nanoparticles (Fe3O4). The modified biochar nanocomposites are characterized using field emission–scanning electron microscopy (FE-SEM), X-ray diffraction (XRD),

4. The co-precipitation of iron oxide (magnetite) on the surface of a biochar or porous carbon material; and

5. The pyrolysis of lignocellulosic or carbonaceous material, impregnated with iron salt

https://www.researchgate.net/figure/Magnetic-biochar-synthesis-methods_fig2_355545416

https://www.researchgate.net/figure/Method-of-preparing-magnetic-biochar-The-liquid-precipitation-method-a-Mohan-et-al_fig1_353088704

Thank you so much Prem Baboo