Scalable Production Method for Graphene Oxide Water Vapor Separation Membranes
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Scalable Production Method for Graphene Oxide Water Vapor Separation Membranes Leonard S. Fifield, Yongsoon Shin, Wei Liu, David W. Gotthold Pacific Northwest National Laboratory, Richland, WA 99354, U.S.A. ABSTRACT Membranes for selective water vapor separation were assembled from graphene oxide suspension using techniques compatible with high volume industrial production. The largediameter graphene oxide flake suspensions were synthesized from graphite materials via relatively efficient chemical oxidation steps with attention paid to maintaining flake size and achieving high graphene oxide concentrations. Graphene oxide membranes produced using scalable casting methods exhibited water vapor flux and water/nitrogen selectivity performance meeting or exceeding that of membranes produced using vacuum-assisted laboratory techniques. (PNNL-SA-117497) INTRODUCTION Selective and efficient water separation is an increasing technological need. Recovery of water from combustion gas streams, drying of biofuels, and dehydration of refrigerants are just a few examples of applications in which effective moisture separation and recovery could lower energy usage, decrease emission and lower costs. Graphene oxide is a chemically rich twodimensional material [1] that can be assembled into macroscopic membranes with high water vapor permeation and low permeation for other gases [2]. The hierarchical structure of graphene oxide membranes that gives rise to the outstanding water separation behavior must also be preserved in any effective fabrication method. Reports of graphene oxide membranes for effective water vapor separation in the literature have described production methods that facilitate laboratory investigation, but are not easily translated to commercial application [3]. In addition to technology needs such as increased understanding and control of graphene oxide membrane stability, develop of membrane production methods that are compatible with industrial scale processes yet maintain membrane performance has been a key need. We describe herein evaluation of graphene oxide membrane produced by the casting method, an example of a method compatible with enable scaled production of graphene oxide membranes toward commercial application. EXPERIMENTAL DETAILS Graphene oxide synthesis Graphene oxide was produced from graphite using the “improved synthesis” reaction of Marcano et. al. [4], which is reported to produce a greater fraction of hydrophilic oxidized graphene than the standard Hummers’ method. A 9:1 mixture of concentrated H2SO4/H3PO4 (90:10 mL) was slowly added to graphite flakes (Sigma-Aldrich, cat #332461, 150 μm flakes) (1.0g) and KMnO4 (4.0 g), producing an exothermic warming of the mixture to 40 °C. The reaction mixture was then heated to 50 °C and very slowly stirred for 16 h. The mixture was cooled to room temperature and poured into a solution of ice water (100 mL) and 30% H2O2 (1.0
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