Carbon-based Materials Incorporated Hybrid Membranes For Pervaporation Dehydration

As a renewable fuel substitute,fuel ethanol can effectively alleviate the current environmental pollution and energy shortage issues.Ethanol dehydration is a key step in the production of high purity fuel ethanol.Pervaporation can effectively break the limits of vapor and liquid equilibrium.Compared with traditional separation process,pervaporation can prevent the contamination of the product as well as conserve energy.The hybrid membrane can effectively synthesize the good film forming property of the polymer matrix and the good permeability of inorganic particles.The introduction of inorganic particles can effectively interfere with the arrangement of polymers and overcome the trade-off effect of polymer membranes.In this study,hydrophilic carbon-based materials were introduced into hybrid membranes for ethanol dehydration.The solution selectivity and diffusion selectivity can be strengthened by controling the physical and chemical properties of inorganic particles,the interaction between inorganic particles and polymer matrix,thus the high-performance pervaporation membrane can be obtained(1)Sulfonated pitch(SP)was introduced into sodium alginate.The effects of SP addition on polymer matrix structure,the optimum separation performance,and the effect of operating conditions on membrane separation performance were investigated.The results show that the SP possess greater affinity with water than of ethanol,therefore effectively increase the solution selectivity.The hydrophilic sulfonic group in SP formed a hydration layer by electrostatic interaction.The hydrophobic pitch part can provide a"transport highway"for the diffusion of water molecules,and the diffusion rate of water molecules was thus increased.When the SP loading was 3 wt%,the optimized separation performance was obtained for separating 90 wt%ethanol aqueous solution at 350K.The permeation flux was 1879±80g/m~2h and the separation factor was 1913±69.The film had good mechanical stability and long-term operability.(2)The graphene oxide quantum dots(GOQDs)were introduced into sodiumalginate.The effects of GOQDs addition on polymer matrix structure,the optimum separation performance,and the effect of operating conditions on membrane separation performance were investigated.GOQDs are highly hydrophilic and can improve the hydrophilicity of the membrane surface.The nano-scale sheet size can reduce the diffusion resistance of water molecules.When the GOQDs loading was 2wt%,the optimized separation performance was obtained for separating 90 wt%ethanol aqueous solution at 350K.The permeation flux was 2432±58 g/m2h and the best separation factor was 1152±48.Compared with other graphene-filled hybrid membranes,the permeation flux of this membrane increases significantly.(3)The effects of GOQDs on the structure of the polymer,the relationship between the membrane structure and the membrane separation performance were investigated by molecular simulation.The mobility of polymer chains and the free volume fraction in the hybrid membrane was reduced.This was mainly attributed to the interaction between GOQDs and polymer chains.The simulation results were consistent with experimental data.The diffusion coefficients of water and ethanol in the membranes and GOQDs were calculated by Einstein formula.The diffusion coefficient of water molecules in GOQDs was the largest,and the diffusion selectivity of hybrid membranes increased.