Method for preparing hexavalent chromium adsorbing agent from lychee exocarp

The invention relates to a method for preparing hexavalent chromium adsorbing agent from lychee exocarp. The method comprises the steps that 1, fresh lychee exocarp is cleaned thoroughly and dried in air; 2, the lychee exocarp is sheared into small pieces through a pair of shears; 3, the lychee exocarp and a strong phosphoric acid are mixed and added into phosphoric acid for soaking and drying; 4, after drying, a lychee exocarp sample is placed into a quartz tube furnace, preheating is performed under nitrogen shielding, then, the temperature is kept constant, and then cooling is performed under nitrogen shielding to obtain a black solid; 5, the black solid is cleaned with distilled water until the solid is colorless; 6, after cleaning is ended, the solid is dried; 7, grinding and smashing are performed, the solid is placed into the quartz tube furnace again to be heated, activated and cooled under the nitrogen shielding; 8, then, distilled water is used for cleaning the solid till the solid is colorless, the