▎ 摘　　要

NOVELTY - Powder mass of multiple individual hollow graphene balls, where one of hollow graphene balls comprises a graphene shell composed of graphene sheets bonded by a carbon material and a hollow core enclosed by graphene shell. USE - Powder mass of multiple individual hollow graphene balls used for an oil-removing or oil-separating device, solvent-removing or solvent-separating device and thermal management device (all claimed). ADVANTAGE - The powder mass of multiple individual hollow graphene balls has thick plate of graphene balls, that can significantly improve the heat transfer between the heat source and the cooling fluid by way of conducting the heat current in an optimal manner, and no additional pumping power and no extra heat transfer surface area are required. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: (1) an oil-removing or oil-separating device comprises hollow graphene balls as an oil-absorbing element; (2) a solvent-removing or solvent-separating device containing hollow graphene balls as a solvent-absorbing or solvent-separating element; (3) a method to separate oil from water, which involves providing an oil-absorbing element comprising hollow graphene balls, hollow graphene balls comprising a graphene shell composed of graphene sheets bonded by a carbon material and a hollow core enclosed by graphene shell; contacting an oil-water mixture with element, which absorbs the oil from the mixture; and retreating the element from the mixture and extracting the oil from the element; (4) a method to separate an organic solvent from a solvent-water mixture or from a multiple-solvent mixture, which involves providing an organic solvent-absorbing or solvent-separating element comprising hollow graphene hollow graphene balls comprising a graphene shell composed of graphene sheets bonded by a carbon material and a hollow core enclosed by graphene shell; bringing element in contact with an organic solvent-water mixture or a multiple-solvent mixture containing a first solvent and at least a second solvent; allowing element to absorb the organic solvent from the mixture or separate first solvent from at least second solvent; and retreating the element from the mixture and extracting the organic solvent or first solvent from the element; and (5) a thermal management device comprises hollow graphene balls as a heat-conducting, heat spreading or heat dissipating element.