The present invention relates to a method for preparing a natural or synthetic polymer hydrogel loading graphene oxide or graphene, and to the selective and high-capacity adsorption and loading of the hydrogel with respect to a low-molecular weight material or a high-molecular weight material. More specifically, an alginate or polyacrylamide hydrogel loading graphene and a graphene derivative is prepared, wherein the hydrogel can be controlled to enable selective absorption according to the characteristics of an adsorbate by adjusting the reduction degree of graphene oxide, exhibits high adsorption capacity, and is easy to handle as a hydrate. These characteristics can significantly improve the adsorption efficiency with respect to a material in water or an organic phase material, compared with existing hydrogels.
