Application Of SPSf Or SPES Membrane In The Separation Of Amino Acids And Production Of Quaternary Ammonium Base By BMED Process

Amino acids are used widely as food and chemical raw materials due to their important edible and commercial values.The amino acid mother liquor obtained by fermentation,enzyme catalysis or chemical synthesis has complex compositions and needs further separation and purification.As a new membrane separation technology,bipolar membrane electrodialysis(BMED)process has realized the separation of mixed amino acids based on the zwitterionic character of the amino acids.However,the use of a dense commercial ion-exchange membrane in the BMED process would result in low current efficiency and high energy consumption,which should be attributed to the large migration resistance of amino acid molecules.Sulfonated polyether sulfone(SPES)and sulfonated polysulfone(SPSf)porous membranes with different structures were prepared in this work and then used in BMED process to separate mixed amino acids to overcome the defect of commercial ion-exchange membranes.In addition,tetrapropyl ammonium hydroxide(TPAOH)is an irreplaceable alkali source and template agent for synthesizing TS-1 molecular sieve.The traditional production methods in the industry are silver oxide,ion exchange,electrolysis and electrofilm reactor methods,but these methods all have the disadvantage of being inefficient and not environmentally friendly.Therefore,another part of this work was to apply the SPSf porous membranes in the production of TPAOH by BMED process.The main contents of the different chapters are as follows:The shortcomings of traditional chemical methods to separate mixed amino acids are explained.Then,the advantages of BMED are briefly introduced.And the advantages of porous membranes in electrodialysis are also discussed.Finally,the topic,the significance and main contents of this thesis are introduced.The porous SPES and SPSf cation exchange membranes were prepared by phase inversion process,and the characterizations of the porous membranes were presented,such as the area resistance(Rm),the water content(WR),the chemical structure and the morphology.The results indicated that the Rm were in the range of 0.35-18.62 ?cm2 and the WR were 197.9-370.1%.The field emission scanning electron microscopy(SEM)confirmed that the pore structures of membranes prepared under different conditions were very different.The BMED process carried out with the porous membranes could obtain higher recovery ratio and current efficiency in the separation of the mixed amino acids of L-glutamic acid(Glu)and L-lysine(Lys)as compared with the dense commercial membrane(CMX).The SPSf or a mixture of PSf and SPSf were used to prepare four porous membranes by phase inversion process.The results showed that the WR were 320.0-399.0%and the Rm were in the range of 0.21-0.96 ? cm2.The SPSf porous membranes were used to produce TPAOH and HBr by BMED process.Meanwhile,the effects of different membrane structures and feed concentrations on the BMED performance were discussed.The porous membrane has a significant advantage,and it can obtain a much higher yield in the production of TPAOH and HBr as compared with the dense SPSf membrane.Finally,the paper was summarized.By applying the porous membranes to the two application areas,it can be found that the porous membranes are conducive to the migration of macromolecules,leading to the higher yield(TPAOH and HBr)and separation efficiency(Glu and Lys).