Preparation And Properties Of Modified Graphene Oxide/Sodium Alginate Composite Hybrid Membranes For Pervaporation

In this paper,hydrophilic sodium alginate was been used as the main membrane-forming substrate,and graphene oxide was the basic modification unit.The modification methods of sulfonation grafting and graphene oxide quantum dots were designed respectively.The modified graphene oxide/sodium alginate hybrid membranes for pervaporation had been prepared by optimizing membrane-forming conditions and adjusting the construction of hybrid membranes.The ethanol-water mixture and isopropanol-water mixture were used as research objects for dehydration by pervaporation.The characterize the microstructure of the membranes were confirmed by FT-IR,XRD,AFM,SEM.The main work included:（1）Benzenesulfonic acid modified graphene oxide（BS@GO）was prepared by sulfonating graphene oxide with 4-aminobenzenesulfonic acid as a sulfonation modifier,which was compounded with sodium alginate SA matrix membrane to prepare sulfonated oxidation Graphene/sodium alginate pervaporation hybrid membrane was used for dehydration of ethanol-water system with ethanol content of90 wt%.The sulfonated modified BS@GO layer had more selective structural defects than GO layer;The effective separation layer of the hybrid membrane was supported by a porous nylon membrane,and the BS@GO in the effective layer tended to be arranged in parallel within the SA matrix;Hydrogen bonding occurred between the benzenesulfonic acid group of BS@GO and the oxygen-containing group of SA,which reduced the glass transition temperature（Tg）of the hybrid membrane.（2）The prepared sulfonated graphene oxide/sodium alginate composite pervaporation hybrid membrane had the best separation performance when the BS@GO content was 1.5 wt%.The permeation flux of SA-BS@GO-1.5 membrane was 703±89 g m^-2 h^-1,which was 1.4 times and 1.3 times of pure SA membrane and SA-GO-1.5 hybrid membrane,respectively.The separation factor of SA-BS@GO-1.5 membrane was 5480±94,which was 5.6 times and 1.2 times of pure SA membrane and SA-GO-1.5 hybrid membrane,respectively.Compared with GO filler,BS@GO could provide higher water permeability than GO,and the hybrid membrane showed good stability and separation performance.（3）Graphene oxide quantum dots（GOQDs）were synthesized by the"bottom-up"method,and composited with sodium alginate SA matrix membrane to prepare graphene oxide quantum dot/sodium alginate pervaporation hybrid membrane for isopropyl Dehydration of an isopropyl alcohol-water system with isopropyl alcohol content of 90 wt%.GOQDs had chemical structures like sp²carbon atoms and hydrophilic groups similar to graphene oxide,and had a small lateral size（<100 nm）,which could be evenly dispersed in SA;Hydrogen bonding occurred between-OH on the SA molecular chain and oxygen-containing groups in the GOQDs structure,which improved the composite effect of graphene oxide quantum dots and sodium alginate.（4）The prepared graphene oxide quantum dot/sodium alginate composite pervaporation hybrid membrane had the best separation performance when the graphene oxide quantum dot content was 2 wt%:permeation flux and separation factor were 1130±51 g m^-2 h^-1,2241±73,respectively 1.41 times and 5.9 times of pure SA membrane;the pervaporation separation index（PSI）of composite hybrid membrane was 2.53×106,which was 8 times that of pure SA membrane.Unlike GO-filled hybrid membranes,zero-dimensional GOQDs could effectively prevent water molecules from penetrating and blocking due to packing.