Graphene Oxide Membrane Via Precision Construction For Pervaporation Process Intensification

Pervaporation is a technique for separating liquid mixtures of similar size and similar properties.It is critical to choose the materials of pervaporation membranes.The special physicochemical properties of graphene oxide（GO）nanosheets and the confined mass transfer mechanism of water molecules in GO membranes have brought great opportunities for the research of GO membranes in pervaporation and preferentially permeable membranes.This thesis strengthens the performance of GO membrane through the following three aspects:（1）fixing the interlayer distance of GO membrane in wet state;（2）improving the hydrophilicity of GO membrane;（3）constructing mass transfer channels with sieving effect for water in the GO membrane interlayer.With n-butanol dehydration and desalination as the separation goals,high permeability,high selectivity and high stability of GO membranes are achieved.The main research results are as follows:（1）Based on the biomimetic mineralization,the GO-PVAm-Silica membrane was made by cross-linking GO nanosheets with polyvinylamine（PVAm）and Silica.GO-PVAm membrane was crosslinked by PVAm to acquire mechanically stable membrane.The amino group of PVAm in GO-PVAm membrane can induce biomimetic mineralization to generate hydrophilic Silica.Based on enhancing the hydrophilicity of the membrane,it acts as a second crosslinker to further fixate the size of 2D channels and improve swelling resistance.Through the coordination of dual crosslinkers,the permeability,selectivity and stability of GO membranes were improved.To be specific,the membrane exhibited a superior pervaporative dehydration performance with separation factor of 1188 and flux of 12.9kg/（m²h）under 80°C for 90wt%butanol/water mixture.And the membrane showed a high Na Cl rejection rate of higher than 99.99%and total permeation flux of 80.2 kg/（m²h）when treating 3.5 wt%Na Cl solution under 70°C.（2）Based on the chelation of phytic acid（PA）,GO-PA-Fe³⁺/PTFE membrane was made by cross-linking GO nanosheets with PA/Fe³⁺complex.Part of the phosphoric acid groups of PA participates in the cross-linking reaction to ensure the stability of the membrane and regulate interlayer spacing of membrane;Part of the phosphoric acid groups chelate with Fe³⁺to form a hydrophilic complex,thereby enhancing the hydrophilicity of the membrane and enhancing the dissolution process of water molecules on the membrane surface process.Water molecules are"pulled"by PA/Fe³⁺complex,and slip rapidly in the non-oxidized area of GO nanosheets,which strengthens the diffusion process of water molecules between the interlayers of membrane membrane.The resultant GO-PA-Fe³⁺/PTFE membrane featured high water permeability as well as selectivity for bio-alcohol molecules.To be specific,the membrane exhibited a superior pervaporative dehydration performance with separation factor of 1059 and flux of 10.57 kg/（m²h）under80°C for 90wt%butanol/water mixture.（3）Based on the host-guest chemistry of supramolecules to form cucurbituril（CB[6]）/metal ion complexes,cross-link GO nanosheets to prepare GO-CB[6]-K⁺/PTFE membrane.Based on the action of charge-dipole and hydrogen bonding,CB[6]with carbonyl groups at the port complexes with metal ions（K⁺）to form a one-dimensional CB[6]-K⁺complex with sub-nanochannels.The GO nanosheets is assembled with CB[6]-K⁺complex through hydrogen bonding,which improves the stability of the membrane,reduces the interlayer spacing in wet state of the membrane and improves the selectivity of the membrane.CB[6]-K⁺complex with hydrophobic channels can promote the rapid transfer of water molecules and enhance the permeability of the membrane.GO-CB[6]-KCl/PTFE membrane featured a superior pervaporative dehydration performance with separation factor of 1689 and flux of 8.059 kg/（m²h）under 80°C for 90wt%butanol/water mixture.