Graphene-based membrane and method of preparation thereof

Abstract

A method of preparing a graphene-based membrane is provided. The method may include providing a stacked arrangement of layers of a graphene-based material, wherein the layers of the graphene-based material define one or more nanochannels between neighboring layers, and varying an electrical charge on a surface of the layers of the graphene-based material defining the one or more nanochannels to control size selectivity and/or ionic selectivity of the graphene-based membrane. A graphene-based membrane and a method of separating ions from a fluid stream are also provided.

What is claimed is: 
     
         1 . A method of preparing a graphene-based membrane, the method comprising
 a) providing a stacked arrangement of layers of a graphene-based material, wherein the layers of the graphene-based material define one or more nanochannels between neighboring layers, and   b) varying an electrical charge on a surface of the layers of the graphene-based material defining the one or more nanochannels to control size selectivity and/or ionic selectivity of the graphene-based membrane.   
     
     
         2 . The method according to  claim 1 , wherein providing the stacked arrangement of layers of a graphene-based material comprises
 a) providing a suspension comprising layers of the graphene-based material dispersed therein,   b) filtering the suspension through a porous substrate to dispose the layers of the graphene-based material as a stacked arrangement on the porous substrate, and   c) separating the stacked arrangement of layers of the graphene-based material from the porous substrate.   
     
     
         3 . The method according to  claim 2 , wherein providing the suspension comprising layers of a graphene-based material dispersed therein comprises
 a) sonicating a dispersion comprising the graphene-based material to exfoliate the graphene-based material into layers, and   b) removing graphene-based material which are present as multilayer crystals from the dispersion to obtain the suspension.   
     
     
         4 . The method according to  claim 2 , further comprising arranging the stacked arrangement of layers of the graphene-based material on a supporting substrate. 
     
     
         5 . The method according to  claim 4 , wherein the supporting substrate is a further membrane comprising an array of nanopores. 
     
     
         6 . The method according to  claim 1 , wherein varying an electrical charge on a surface of the layers of the graphene-based material defining the one or more nanochannels comprises at least one of (i) varying polarity of the electrical charge; (ii) varying magnitude of the electrical charge, or (iii) arranging layers of opposite electrical charges in the stacked arrangement. 
     
     
         7 . The method according to  claim 1 , wherein varying an electrical charge on a surface of the layers of the graphene-based material defining the one or more nanochannels comprises carrying out at least one of (i) a chemical substitution process on the graphene-based material, (ii) a reduction process on the graphene-based material, or (iii) contacting the graphene-based material with a liquid reagent and varying molarity and/or pH of the liquid reagent. 
     
     
         8 . The method according to  claim 1 , further comprising applying pressure to a surface of the stacked arrangement of layers of the graphene-based material. 
     
     
         9 . A graphene-based membrane comprising a stacked arrangement of layers of a graphene-based material, the layers of the graphene-based material defining one or more nanochannels between neighboring layers, wherein a surface of the layers of the graphene-based material defining the one or more nanochannels possess an electrical charge, and wherein the layers of the graphene-based material are configured to control size selectivity and/or ionic selectivity of the graphene-based membrane by varying the electrical charge. 
     
     
         10 . The graphene-based membrane according to  claim 9 , wherein the graphene-based material comprises graphene oxide. 
     
     
         11 . The graphene-based membrane according to  claim 9 , wherein the neighboring layers of the graphene-based material are spaced apart by a distance in the range of about 0.5 nm to about 2 nm. 
     
     
         12 . The graphene-based membrane according to  claim 9 , wherein the layers of the graphene-based material has a lateral dimension in the range of about 0.1 μm to about 10 μm. 
     
     
         13 . The graphene-based membrane according to  claim 9 , wherein the stacked arrangement of layers of a graphene-based material is arranged on a supporting substrate. 
     
     
         14 . The graphene-based membrane according to  claim 13 , wherein the supporting substrate is a further membrane comprising an array of nanopores, and wherein the further membrane is formed of a material selected from the group consisting of SiN x , carbon foam, ceramic membrane, and polymeric membrane. 
     
     
         15 . The graphene-based membrane according to  claim 9 , wherein the layers of the graphene-based material are configured to control size and/or ionic selectivity of the graphene-based membrane by varying at least one of (i) polarity of the electrical charge; (ii) magnitude of the electrical charge, or (iii) arranging layers of opposite electrical charges in the stacked arrangement. 
     
     
         16 . The graphene-based membrane according to  claim 9 , wherein the graphene-based membrane is configured to reject ions having a radius of hydration of at least about 4.5 Å. 
     
     
         17 . A method of separating ions from a fluid stream, the method comprising
 a) providing a graphene-based membrane comprising a stacked arrangement of layers of a graphene-based material, the layers of the graphene-based material defining one or more nanochannels between neighboring layers, wherein a surface of the layers of the graphene-based material defining the one or more nanochannels possess an electrical charge, and wherein the layers of the graphene-based material are configured to control size selectivity and/or ionic selectivity of the graphene-based membrane by varying the electrical charge, and   b) directing a fluid stream comprising one or more ions towards a first surface of the graphene-based membrane, wherein ions to be separated from the fluid stream are filtered through the graphene-based membrane.   
     
     
         18 . The method according to  claim 17 , wherein directing the fluid stream comprising one or more ions towards a first surface of the graphene-based membrane is carried out without an electrical field. 
     
     
         19 . The method according to  claim 17 , wherein directing the fluid stream comprising one or more ions towards a first surface of the graphene-based membrane is carried out with an electrical field. 
     
     
         20 . The method according to  claim 19 , wherein the method of separating ions from a fluid stream is applied to electrodialysis.