Hybrid Membranes Fabricated By Incorporating Si-skeleton Materials For Pervaporation Dehydration

Organic-inorganic hybrid membranes,which own the advantages of organic membrane and inorganic membrane,have become the hotspot in the membrane separation field.This study focused on incorporating the Si-skeleton materials into sodium alginate(SA)polymer matrix as inorganic phase to fabricate the hybrid membranes for pervaporation dehydration.The as-prepared membranes have the appropriate microstructure,interfacial morphology,hydrophilic-hydrophobic properties and optimum water states.The incorporated Si-skeleton materials construct the continuous channels which benefit the diffusion of water molecules in hybrid membrane.Meanwhile,the separation performance of hybrid membranes was systematically evaluated based on the pervaporation dehydration of ethanol.To investigate the influences of Si-skeleton materials as inorganic phase on solution selectivity,the hydrophilic attapulgite(AT)nanorods were blended with SA matrix to fabricated hybrid membranes.The open-framework structure with free cross section of 0.38nm ×0.63nm in AT nanorods structure,as well as the hydrophilic surface,constructed the channels which are beneficial for water diffusion in hybrid membranes.Meanwhile,due to the special sandwich structure of AT nanorods the content of non-freezable water in hybrid membrane was increased,improving the solution selectivity of water molecules.The microstructure,interfacial morphology,hydrophilic-hydrophobic properties hybrid membranes were systematically characterized.The optimum separation performance with a flux of 1356g/m~2h and a separation factor of 2030 was achieved when the content of AT nanorods was 2wt.%.To optimize the diffusion process,the halloysite nanotubes(HNTs)with a hydrophobic external surface and a hydrophilic internal surface were introduced into SA matrix to fabricated hybrid membranes.The hydrophilic tubular channels with diameter of ~15nm in HNTs facilitated the diffusion of permeate molecules.And the hydrophilic spaces(~0.7nm)between interlayers accelerated water diffusion in membranes.In addition,HNTs disturbed the packing of SA chains and increased the content of freezable water,decreasing the crystallinity degree of SA matrix and optimizing the diffusion selectivity of water molecules.The microstructure and hydrophilic-hydrophobic properties of hybrid membranes were systematically characterized.The optimum separation performance with a flux of 1722g/(m~2h)and a separation factor of 1415 was achieved when the content of HNTs was 4wt.%.To optimize the solution-diffusion process and obtain the hybrid membranes with high separation performance,the novel Si-skeleton PEG@POSS nanoparticles were introduced into SA matrix to fabricated the hybrid membranes with ultrathin active layers(~180nm)and high content of inorganic fillers(50wt.%).The PEG chains in PEG@POSS enhance the interfacial compatibility with SA matrix,improving the ratio of inorganic phase.The cage structure of POSS avoid the washing of PEG chains away,guaranteeing the stability of hybrid membranes.The incorporated PEG@POSS decreased the crystallinity degree and swelling degree of SA matrix,increased the hydrophilicity and factional free volume and cavity size,enhancing the solution-diffusion selectivity of hybrid membranes.The optimum separation performance with a flux of 2500g/m~2h and a separation factor of 1077 was achieved when the content of PEG@POSS was 30wt.%.