▎ 摘　　要

NOVELTY - A magnetic nanomaterial comprises graphene oxide, alpha -manganese dioxide nanowire grown on graphene oxide by deposition method, and introduces magnetic ferroferric oxide, and a layer of polypyrrole coated on the surface of alpha -manganese dioxide nanowire by redox reaction. USE - Magnetic nanomaterial is used for degrading hexavalent chromium ions in sewage. ADVANTAGE - The magnetic nanomaterial efficiently degrades hexavalent chromium ion in sewage, with chromium adsorption capacity of 374.53 mg/g, and is prepared efficiently and economically by simple method. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for preparation of magnetic nanomaterial. 1 g Graphite flakes and 1 g sodium nitrate are mixed, and 48 mL concentrated sulfuric acid and 6 g potassium permanganate are added in an ice water bath. The temperature is controlled at 5 degrees C or less, and continuously reacted in ice water bath for 4 hours. Then, the reaction system is transferred to an oil bath, and stirred at 35 degrees C for 2 hours. At the end of the reaction, 40 mL deionized water is gradually added, and the temperature is adjusted to 95 degrees C for 30 min. To the resultant mixture, 100 mL deionized water and 8 mL 30% hydrogen peroxide are added to remove unreacted potassium permanganate. The obtained product is centrifuged, washed, and vacuum dried to obtain solid graphene oxide. 0.75 g Potassium permanganate, 0.1 g graphene oxide and 1.3 g potassium persulfate are added to 15 mL deionized water, ultrasonically processed for 40 minutes, transferred to 50 mL reactor, reacted at 140 degrees C for 24 hours. The obtained product is washed successively using deionized water and absolute ethanol, and finally dried under vacuum to obtain composite material of graphene oxide and alpha -manganese dioxide nanowire. 5 mL 1,6-Hexanediamine, 2 g anhydrous sodium acetate and 1 g ferric chloride hexahydrate are added to 30 mL ethylene glycol solution, and stirred at 50 degrees C until the mixture is transparent. The resultant mixture is then transferred to 50 mL reactor, and the reaction is carried out at 200 degrees C for 6 hours. The obtained product is then washed by centrifugation and dried under vacuum to obtain magnetic ferroferric oxide. 150 mg composite material of graphene oxide and alpha -manganese dioxide nanowire is added to 125 mL deionized water, and ultrasonically processed for 30 minutes. To the resultant mixture, 30 mg ferroferric oxide is added and the temperature is controlled at 30 degrees C for 3 hours. The obtained product is then washed with suction and dried under vacuum to obtain composite material of graphene oxide/manganese oxide/ferric oxide. 150 mg Obtained product is then mixed with 60 mL 0.1 M sulfuric acid solution, ultrasonically processed for 30 minutes, and stirred under an ice water bath condition to obtain reaction liquid (I). 40 mL 0.1 M Sulfuric acid solution is mixed with 100 mu L pyrrole monomer solution to obtain reaction solution (II). The obtained reaction liquid (II) is quickly added to reaction liquid (I), stirred under ice water bath for 3 hours. The obtained product is then washed with suction and dried under vacuum to obtain magnetic nanomaterial.