Preparation Of Functional Composite Anion Exchange Membrane And Its Application In Soy Sauce Desalination

Modern medicine shows that high salt diet increases the burden of human organs and easily causes hypertension and cardiovascular diseases.Soy sauce,as a kind of high salt food,its desalination has become a research hotspot.In this paper,the method of electrodialysis was used to selectively separate salt ions and organic matter in soy sauce,and the migration mechanism was studied,which provided a theoretical basis for the separation and resource utilization of the co-existing system of industrial high salt and high organic matter.Firstly,the desalination of soy sauce was studied by using commercial ion exchange membrane in electrodialysis.The effects of current density,flow rate and p H value on the separation of salt and organic matter by electrodialysis process were investigated.It was found that the desalination degree was the highest under the conditions of 50 A/m²,30 L/h and p H=5,which reached 64.7%.However,organic matter caused serious membrane fouling,and the total amino acid loss rate was as high as 29.8%.In order to reduce the amino acid loss rate,thin film composite(TFC)ion exchange membrane was prepared by interfacial polymerization using piperazine(PIP)and metal-organic framework material(MOF,UIO-66(Zr)-NH₂)as aqueous monomer and triphenylchloride(TMC)as organic monomer.The physical characterization of the membrane was analyzed.The results showed that the density and roughness of the polyamide layer on the surface of TFC ion exchange membrane after interfacial polymerization were higher than those of commercial ion exchange membrane.Through the monovalent ion selectivity experiment,it can be seen that the MOF TFC ion exchange membrane(CJMA-IP2)has a good permselectivity of 4.02 for chloride ion and sulfate ion,which was much higher than that of commercial ion exchange membrane.Finally,the prepared TFC ion exchange membrane was passed through amino acid mixed salt solution(glycine,valine,aspartic acid)to explore the migration mechanism of amino acids,and applied to the separation of salt and organic matter in soy sauce.It was found that the desalination rate of CJMA-IP2 reached 69%,while the loss rate of total amino acids was 19.1%.In particular,the loss rate of glycine with smaller molecular weight was 17.1%through commercial anion exchange membrane,while the loss rate of CJMA-IP2 was only 4.6%,that is,the small molecular organic matter was effectively intercepted.And the CJMA-IP2 has a good anti-pollution performance.To sum up,this paper proves that electrodialysis technology can be successfully applied to the desalination of soy sauce,and the preparation of TFC ion exchange membrane through interface polymerization can effectively improve the separation coefficient of salt and organic matter,which not only provides a model for the subsequent electrodialysis technology in the food industry,but also provides a system of high salt and high organic matter coexistence.For example,the resource utilization of high salt and high organic matter wastewater in chemical industry provides theoretical guidance.