The invention relates to a method for preparing modified
biomass charcoal for passivating lead and
cadmium in soil. The method comprises the following steps: A,
grinding and screening
biomass raw materials; B, respectively dissolving FeSO4.7H2O and KMnO4 in water, uniformly mixing, regulating the pH value to 7, thus obtaining iron and
manganese oxide suspension; C, adding the ground
biomass raw materials into the iron and
manganese oxide suspension, uniformly stirring, soaking,
drying at the temperature of 105 DEG C for 6 hours, thus obtaining a biomass material loaded with iron and
manganese oxides; and D, adding the biomass material loaded with iron and manganese oxides into a reactor, raising the temperature to 450-650 DEG C under
oxygen-limited conditions, carrying out a
pyrolysis carbonization reaction, thus obtaining the modified biomass
charcoal. According to the method disclosed by the invention, the iron and manganese oxides are distributed in the surface and pores of the biomass
charcoal, a
passivation effect of the biomass charcoal on
heavy metals lead and
cadmium can be obviously improved, the environmental benefits of the biomass charcoal for treating contaminated soil are effectively improved, and the remediation cost of heavy
metal contaminated soil also can be effectively reduced.