Study On The Preparation And Separation Performance Of The Pervaporation Membrane Based On Graphene Oxide For Alcohol Recovery

As a kind of renewable energy,bio-butanol has the potential to replace fossil fuels,so as to solve the global energy crisis.In the process of biobutanol preparation,it is necessary to remove butanol from fermentation broth in time to reduce the inhibition of butanol on microorganisms.The pervaporation membrane separation technology has the characteristics of high selectivity,mild operating conditions,no need to introduce other components and so on.It can be coupled with the fermentation device to realize the in-situ continuous separation of bio-butanol.Therefore,pervaporation membrane separation technology is of great significance in the field of bio fuel purification and concentration.The main factor affecting the development of pervaporation membrane separation technology is the separation performance of membrane.The preparation of high-performance pervaporation membrane can be realized by adjusting membrane material and membrane structure.At present,the preferred pervaporation membrane materials are all organic polymer materials,but their separation performance still can not meet the needs of industrial applications.In order to improve the separation performance of the pervaporation membrane,ultra-thin graphene oxide（GO）nano sheet was used as the film-forming material,which was compounded with organic polymer to form the membrane and construct the priority mass transfer channel of butanol molecules.The metal organic framework material was used to hydrophobically modify GO,to improve the priority adsorption capacity of butanol,and further treatment methods such as sulfurization were used to increase the butanol mass transfer channel inside the membrane.Finally,the priority pervaporation membrane with high separation performance and stability was obtained.Firstly,ZIF-8@GO/PEBA composite membrane was prepared by vacuum assisted assembly on porous ceramic tubular basement membrane.ZIF-8nanoparticles were grown in situ on the go nano sheet,and the ZIF-8 nanoparticles were anchored on the GO nano sheet to form ZIF-8@GO nanocomposites.Due to the strong affinity of ZIF-8 to butanol,the priority adsorption of butanol on go nano tablets was increased.ZIF-8@GO and PEBA were deposited on the surface of ceramic tube by step assembly,which solved the problem of poor dispersion of ZIF-8@GO in PEBA solution.The ultra-thin two-dimensional frame structure formed by ZIF-8@GO nano sheet on the surface of ceramic tube can form an efficient butanol transport channel,and PEBA can make up for the internal defects of the frame,so as to obtain a high selectivity and permeability of the first permeable butanol pervaporation membrane.In this study,the microstructure and chemical properties of ZIF-8@GO/PEBA composite membrane were characterized,and the separation performance of the composite membrane under different preparation and operation conditions was investigated.When the feed temperature was 55^oC,the flux of ZIF-8@GO/PEBA composite membrane was 1001 g·m^-2·h^-1,and the separation factor was 29.3.Compared with the pure PEBA membrane,the permeation flux and separation factor increased by 77%and 88%,respectively.Secondly,in order to further reduce the mass transfer resistance of butanol molecules in the membrane,thioacetamide（TAA）was used to vulcanize ZIF-8@GO to increase the internal transport channel of the composite membrane.TAA can release S^2-to coordinate with Zn²⁺,and form ZnS@GO composite particles with hollow box structure by sacrificing ZIF-8.Therefore,the in-situ vulcanization of ZIF-8@GO two-dimensional framework composite membrane can increase the mass transfer channel of butanol molecules on the premise of ensuring the separation layer structure,thus improving the permeability of the membrane,and further increasing the compactness and stability of the composite membrane through heat treatment.In this study,the structure of ZnS@GO and its composite membrane before and after vulcanization was characterized,and the effects of preparation conditions such as vulcanization time,vulcanizer concentration,decomposition rate of vulcanizer on the separation performance were investigated.The results showed that the flux of ZnS@GO/PEBA composite membrane was 1025 g·m^-2·h^-1and the separation factor was 29.6 at 55^oC.The permeation flux of the composite membrane after vulcanization increased by 2.4%.In this study,ZIF-8@GO/PEBA and ZnS@GO/PEBA composite membranes were successfully prepared by vacuum assisted assembly for pervaporation separation of priority alcohols.By adjusting the structure and properties of the composite membranes,excellent pervaporation membranes with priority butanol permeability were obtained,which provided a new idea for the preparation of priority pervaporation membranes.