Preparation And Separation Performance Of Hierarchical Graphene Oxide-based Membranes

Graphene oxide?GO?membrane with well-defined laminate nanostructure and controlled nanochannels exhibits high adsorption or filtration performace for some ions,molecules and charged particles such as dye molecules and heavy metal ions.It can be widely used in oil/water and heavy metal filtration and desalination fields.However,the GO membrane shows low permeation flux and weak stability.Herein,we adopt hybrid membranes by combing GO and inorganic nanoparticles?SiO₂ and MOF?.The formed hierarchical pore structure of GO-based hybrid membrane could resulted in high permeation flux,high chemical stability and excellent filtration performance and the hybrid membrane can be used in oil/water,dye molecule and heavy metal ion filtration fields.We mainly studied the formation process,microstructure and filtration performance of the memrbanes.The following researches are carried out:?1?Methyl modified silica?Me-SiO₂?aerogels are prepared using tetraethylorthosilicate?TEOS?and methyltriethoxysilane?MTES?as co-precursor through a two-step sol-gel reaction.The prepared Me-SiO₂ aerogels exhibit high surface area?1068 m²/g?and expanded pore volume?4.26 cm³/g?.The MTES addition endows Me-SiO₂ aerogels dual modal pore structure with two different micropore sizes.The replacement of hydrophilic–OH with hydrophobic–CH₃ endows Me-SiO₂aerogels high hydrophobic with contact angle showing an increase up to 148°.Furthermore,Me-SiO₂ aerogel exhibits outstanding adsorbing capability with quality factor?Q?up to 23 g/g,which is almost 2-3 times higher than commercial adsorbents.?2?SiO₂/GO membrane is fabricated using a vacuum-assisted filtration self-assembly process.The stacking of GO nanosheets and SiO₂ nanoparticles endows SiO₂/GO membrane a hierarchical nanostructure consisted of nanopores and micron pores which resulted in high water permeation flux up to 964 L·m^-2·h^-1 and water/oil emulsion flux up to 507 L·m^-2·h^-1.The outstanding hydrophilicity and underwater superoleophobicity endow SiO₂/GO memrbanes high oil/water filtration stability which leading to a high oil rejection rate of over 98.4%after 8 cycles or after 14 min filtration.In addition,the SiO₂/GO hybrid membranes also exhibit excellent dye removal.A rejection rate up to 100%can be achieved for methyl blue?MB?dye.?3?MOF/GO membrane is fabricated using a vacuum-assisted filtration self-assembly process by combing GO and metal-organic frameworks?MOF?.The MOF/GO membrane shows high water permeation flux of up to 221 L·m^-2·h^-11 which is 12 times higher than that of pure GO membrane.MOF/GO membrane exhibits excellent heavy metal ion removal performance with the rejection of 99%for Pb²⁺and68.2%for Cu²⁺.MOF/GO membrane also exhibits high rejection for heavy metal ion after a long-term usage.The hybrid membrane can keep a high filtration recovery of Pb²⁺for 86%after 10 min and 81%for Cu²⁺.