▎ 摘　　要

NOVELTY - Preparing a hydrogel comprises (i) preparing biomass carbon powder, (ii) adding the biomass carbon powder obtained in the resultant step into a stannous chloride solution with the concentration of 11-18 g/l for sensitization, filtering and cleaning with deionized water after 2-3 minutes, then adding a palladium chloride solution with the concentration of 0.4-0.8 g/l for activation, filtering and cleaning with deionized water after 2-3 minutes, (iii) adding the biomass carbon powder pretreated in the resultant step into a chemical plating solution for chemical plating, where the plating time is 2-40 minutes, the plating temperature is 60-75degrees Celsius and then filtering and drying to obtain magnetic electromagnetic shielding powder. USE - The hydrogel is useful in functional material. ADVANTAGE - The method: catalyse and reduce magnetic metal nano particles to realize attachment on the biomass carbon powder; and the obtained product has excellent electromagnetic, skin-friendly, shielding and self-repairing performance. DETAILED DESCRIPTION - Preparing a hydrogel comprises (i) preparing biomass carbon powder; (a) placing the dried bamboo fungus into a tubular furnace for high-temperature carbonization, cooling, taking out, grinding into powder to obtain solid powder A, where the high-temperature carbonization reaction temperature is 250-350degrees Celsius, the reaction time is 2-3 hours and the reaction is carried out under the protection of inert gas, (b) adding the solid powder A and an activating agent into a solvent, stirring and mixing uniformly to obtain a suspension, drying and grinding to obtain solid powder B, where the activating agent comprises potassium hydroxide, sodium hydroxide, zinc dioxide and/or phosphoric acid. The solvent comprises deionized water and/or ethanol, in the suspension, the concentration of the solid powder A is 0.2-0.3 g/ml and the concentration of the activating agent is 0.2-0.9 g/ml, (c) placing the resultant solid powder B into a tubular furnace for high-temperature pyrolysis, taking out after cooling, soaking with hydrochloric acid, cleaning, drying and grinding to obtain biomass carbon powder, where the high-temperature pyrolysis conditions are as follows: under the protection of inert gas, the reaction temperature is 600-1000degrees Celsius and the reaction time is 3-5 hours, (ii) adding the biomass carbon powder obtained in the resultant step into a stannous chloride solution with the concentration of 11-18 g/l for sensitization, filtering and cleaning with deionized water after 2-3 minutes, then adding a palladium chloride solution with the concentration of 0.4-0.8 g/l for activation, filtering and cleaning with deionized water after 2-3 minutes, (iii) adding the biomass carbon powder pretreated in the resultant step into a chemical plating solution for chemical plating, where the plating time is 2-40 minutes, the plating temperature is 60-75degrees Celsius and then filtering and drying to obtain magnetic electromagnetic shielding powder, (iv. a) adding a dispersing agent and the magnetic electromagnetic shielding powder obtained in the resultant step into deionized water, performing ultrasonic treatment to obtain a mixed solution C, where the mass ratio of the dispersing agent to the magnetic electromagnetic shielding powder is 3:(1-10), the concentration of the magnetic electromagnetic shielding material is 0.002-0.004 g/ml, (b) adding 1-8 wt.% surfactant, 0.02-0.05 wt.% lauryl methacrylate, 0.04-0.13 wt.% graphene oxide and 0.2-0.6 wt.% chitosan into the mixed solution C and performing ultrasonic treatment to obtain a mixed solution D, (c) adding 0.1-1.5 wt.% initiator, 1-20 wt.% organic monomer and 0.1-0.9 wt.% cross-linking agent into the mixed solution D and uniformly stirring to obtain a mixed solution E, and (d) polymerizing the mixed solution E in a vacuum drying oven at the polymerization temperature at 50-70degrees Celsius for 4-8 hours.