A graphene oxide membrane with self‐regulated nanochannels for the exceptionally stable bio‐oil dehydration

Abstract

The transport behaviors and nanochannel structures of a graphene oxide (GO) membrane were studied for pervaporation dehydration of bio-oil with a high acidity and a complex composition. The GO membrane showed an unprecedentedly stable water flux of approximately 0.43 kg m −2 hr −1 , with a water content of 97 wt% in the permeate throughout 70 hr of pervaporation testing at 30 C. Both the calculated activation energy for water permeation and X-ray diffraction characterization results confirmed that the nanochannel structures of the GO membrane were temperature-and liquid media-responsive. The molecular intercalation-induced selfregulation of the size of laminar nanochannels in the GO membrane was suggested to be primarily responsible for the significantly reduced membrane fouling and the exceptionally stable pervaporation performance for the GO membrane. The mechanistic insights into the nanochannel structures and antifouling properties would provide important inspiration for the design of novel highly fouling-resistant membrane materials for practical applications.

Dehydration of C2–C4 alcohol/water mixtures via electrostatically enhanced graphene oxide laminar membranes

“…Inorganic materials such as zeolites 8 and metal–organic frameworks 9 have shown excellent separation performance for solvent dehydration, and the large‐scale fabrication of defect‐free membranes would further promote the use of inorganic membranes in the chemical industry 10 . As an emerging alternative membrane material, graphene oxide (GO), which has a single‐layer structure offers great potential to minimize the membrane thickness and, thus, maximize the permeance 1,11‐13 . Moreover, the functional groups (e.g., epoxy groups, hydroxyl groups, and carboxyl groups) of GO can be chemically modified 14 during membrane fabrication, thus forming water transport channels between the GO nanosheets 15 …”

“…Despite their great potential for water separation, GO membranes suffer from some practical problems, including relatively low separation performance and structural instability in water 13,16 . Thus, there is much scope for improving the separation performance of GO membranes for practical use 17 .…”

“…18 Thus, precision assembling and tuning of the interlayer structure of GO membranes are critical to improve the membrane stability and separation performance. [19][20][21] Various strategies have been proposed to regulate the interlayer structure of GO membranes to achieve selective water transport 1,12 and improve their structural stability 13 in water. Among them, crosslinking is the most widely studied approach.…”

“…Apparently, the strong covalent bonds endow the GO membranes with enhanced selectivity and stability but reduce the permeance because of the reduction in the size of the interlayer channels. 13 Intuitively, introducing molecular interactions that are weaker than covalent bonds, for example, electrostatic interactions, could enable the formation of selective and stable interlayer channels while preventing the excessive reduction in the number and size of the channels within the GO membranes. In fact, the assembly of polyelectrolytes and GO nanosheets via electrostatic interaction has been demonstrated to be a feasible strategy to improve the separation performance of GO membranes for water filtration processes including nanofiltration and forward osmosis.…”

Effect of Temperature and Branched Crosslinkers on Supported Graphene Oxide Pervaporation Membranes for Ethanol Dehydration

“…When the crosslinker molecules are normal to the GO sheets, they can act as spacers between them and hence can be used to regulate the flux through the membrane [29]. Further, many techniques are being studied for the scalable production of both free-standing as well as supported GO membranes, including filtration [28][29][30], drop casting [32], layer-by-layer deposition [33][34][35], dip coating [36,37], vacuum suction [38], spray coating [39,40] and rod coating [39,41]. We have previously studied the stability of GO membranes obtained by crosslinking GO by molecules with branched structures, as well as the potential of the membranes for the dehydration of ethanol-water mixtures beyond the azeotropic limit using a vapor permeation set-up [41].…”