Green method for preparing multifunctional biochar from sludge and application of biochar

The invention provides a green method for preparing multifunctional biochar from sludge and application of the biochar, and belongs to the technical field of sludge treatment and resource utilization. According to the method, dried sludge powder with relatively low water content and excessive salt containing oxygen ions are mixed and heated to pyrolyze the sludge, or the dried sludge powder is added into the molten salt to be pyrolyzed, and the pyrolysis product is subjected to acid pickling or/and water washing to remove impurities, so that the biochar is obtained. And compared with the nitrogen protection pyrolysis process, the emission of secondary pollutants in the pyrolysis process is greatly reduced. The specific surface area, the carbon atom content and the heteroatom doping amount of the prepared biochar are higher than those of biochar prepared by a nitrogen protection method, so that the biochar not only has more excellent adsorption performance, but also has Fenton-like reaction catalytic activity