Tailoring Fabrication And Pervaporation Desalination Performance Of BTESE-based Organosilica Hybrid Membranes

In the past decades,with the acceleration of urbanization in the world,people’s demand for water is also increasing,and the problem of water shortage is becoming more and more serious.In order to solve the problem of water shortage,seawater desalination is a feasible and beneficial supplement method to obtain fresh water.Due to its unique amorphous structure and pore size,microporous silica membranes have been used by many researchers to obtain fresh water from seawater desalination and desalting.However,there are still widespread problems such as insufficient membrane flux,retention rate and stability at present.Gallium doped 1,2-bis（triethoxysilane）ethane（BTESE）based silicon dioxide hybrid membrane were prepared,and the desalting performance of the hybrid membrane in different acid base or salt solution environments was studied in this thesis.The specific research content and results are as follows:（1）Aiming at the problem that the current membrane materials lack long-term stability in different environments,especially in acidic environments,a Ga-doped BTESE hybrid membrane with high stability was designed and prepared.Using BTESE as the precursor of silane and gallium nitrate as the source of Gallium,the silica hybrid membrane prepared by sol-gel method can not only maintain high flux for a long time,but also achieve high salt retention rate even in highly acidic environment.The physical and chemical properties of sol-gel and membrane microstructure were investigated by various characterization methods.It was proved that Si-O-Ga bonds formed by the hydrolysis and condensation reaction of the metal element gallium were uniformly distributed in the network structure of silica,which regulated the skeleton structure and surface microstructure of the membrane,thus improving the stability of the hybrid membrane.The optimized Ga_0.25-BTESE hybrid membrane showed stable flux of 14kg m^-2 h^-1 and nearly 100%salt retention at 30 ^oC,3.5wt%Na Cl solution.In the highly acidic（p H=1～2）solution of 3.5wt%Na Cl,the salt retention rate was still higher than99%,although the membrane flux increased slightly after 30 days of acid immersion.Therefore,due to its excellent acid-resistant stability,the membrane has great potential in the long-term treatment of acidic high-salt wastewater.（2）BTESE andγ-glycidyl ether oxypropyl trimethoxysilane（KH560）were used as precursors to form a sol system under the catalysis of nitric acid,and the BTESE-KH560 dual-silane precursors hybrid membrane was successfully prepared by sol-gel method.The effects of silane ratio,acid ratio,water ratio and other conditions on the film performance were investigated in detail.Combined with various characterization results,it was shown that the dual-silicon source system could effectively regulate the structure of the silica network and increase the molecular mass transfer rate in the nano water channel,which showed that the membrane flux could be increased while the salt retention rate could be high.The optimized membrane prepared in 30 ^oC,3.5wt%Na Cl solution showed a highest water flux of 40 kg m^-2 h^-1 and nearly 100%salt retention rate.And in the 30-days stability test can withstand a wide range of acid and alkaline（p H=2-12）test,simple cleaning membrane desalination performance can be restored and regeneration.In addition,the membrane showed stable desalting performance in different salt concentrations（1-20 wt%）and solutions containing different salt components,and it still had stable membrane flux(25 kg m^-2 h^-1)and nearly 100%interception rate in the complex environment of real seawater simulated by mixed salt.Therefore,the membrane has a good application prospect in the treatment of wastewater under different p H values,the treatment of high concentration salt wastewater and seawater desalination.