Separation of water using a membrane

Abstract

This invention relates to uses of graphene oxide, and in particular graphene oxide on a porous support, and a membrane comprising these materials. This invention also relates to methods of dehydration, which include vapour phase separation and pervaporation. Pervaporation is a method of separating mixtures of liquids using a membrane. Pervaporation consists of two basic steps: permeation of the permeate through the membrane and evaporation of the permeate from the other side of the membrane. Pervaporation is a mild which can be used to separate components which would not survive the comparatively harsh conditions needed for distillation (high temp, and/or low pressure).

1 . A composite semi-permeable membrane in the form of a laminar structure comprising at least a layer of graphene oxide and a layer of porous support; wherein the layer of graphene oxide comprises a stack of a plurality of randomly oriented single molecular graphene oxide layers; and
 wherein the support is a polymeric material.   
     
     
         2 . The composite semi-permeable membrane as claimed in  claim 1 , wherein the support is a polymeric material selected from PTFE, PVDF and cyclopore polycarbonate, polysulfones, polyethersulfones, polypropylene, acrylic polymers, polyamide, polyvinyl alcohol, polytetrafluoroethylene, cellulose esters, cellulose nitrate, cellulose acetate and regenerated cellulose. 
     
     
         3 . The composite semi-permeable membrane as claimed in  claim 1 , wherein the graphene oxide layer has a thickness of less than about 100 μm. 
     
     
         4 . The composite semi-permeable membrane as claimed in  claim 3 , wherein the graphene oxide layer has a thickness of less than about 5 μm. 
     
     
         5 . The composite semi-permeable membrane as claimed  claim 1 , wherein the porous support has a surface roughness which is the same as or smoother than as PTFE. 
     
     
         6 . The composite semi-permeable membrane as claimed in  claim 1 , wherein the porous support layer has a thickness of less than about 100 μm. 
     
     
         7 . The composite semi-permeable membrane as claimed in  claim 1 , wherein the porous support layer has a thickness of more than about 1 μm. 
     
     
         8 . The composite semi-permeable membrane as claimed in  claim 1 , wherein the ratio of the thickness of the graphene oxide layer to the thickness of the porous support layer is in the range from 10:1 to 1:10. 
     
     
         9 . The composite semi-permeable membrane as claimed in  claim 8 , wherein the ratio of the thickness of the graphene oxide layer to the thickness of the porous support layer is in the range from 1:2 to 1:10. 
     
     
         10 . The composite semi-permeable membrane as claimed in  claim 1 , wherein the porous support is no more hydrophobic than PTFE. 
     
     
         11 . The composite semi-permeable membrane as claimed in  claim 1 , wherein the porous support has a pore size in the range 0.1 to 300 nm. 
     
     
         12 . The composite semi-permeable membrane as claimed in  claim 11 , wherein the pore size is in the range 0.1 to 200 nm. 
     
     
         13 . The composite semi-permeable membrane as claimed in  claim 1 , wherein the inter-layer distance between single molecular graphene oxide layers is from 0.7 nm to 1.3 nm. 
     
     
         14 . The composite semi-permeable membrane as claimed in  claim 1 , wherein the GO is intercalated with other atoms or molecules.