Biological carbon prepared from tobacco stems as well as preparation method and application thereof

The invention discloses a method for preparing biological carbon from tobacco stems. The method for preparing the biological carbon from the tobacco stems comprises the following steps: (1), crushing the tobacco stems, and then enabling the crushed tobacco stems and water to be subjected to a hydrothermal carbonization reaction at 180-260 DEG C; after terminating the reaction, filtering, washing and drying an obtained product in sequence; (2), activating the product, which is dried in Step (1), by an activating agent, afterwards, calcining the activated product at 400-1200 DEG C in an inert atmosphere, and subsequently, washing the calcined product with water, drying the water-washed product, and obtaining the biological carbon. The activating agent is at least one of a lewis acid, a peroxide, an alkali metal hydroxide and an alkali metal carbonate. The invention also discloses the biological carbon prepared by adopting the method and application of the biological carbon to the adsorption of heavy metal. An obtained biological carbon material has advantages of relatively small particle sizes, relatively large specific surface area, relatively strong adsorption capacity and the like, and can be applied to the adsorption and the repair of heavy metal ions in a water body and a soil environment.