High-efficiency Energy-saving Desalination Process And Application Of Soluble Silk Fibroin Solution

As core fiber of native silk fibers,fibroin exhibit a unique and useful combination of properties such as being degradable and light-weight with excellent mechanical and thermal properties,widely used in cosmetics,medicine and biology.However,fibroin fibers,which are insoluble in water,can only be dissolved in concentrated acid,or high concentration salt solutions,such as formic acid,LiBr and CaCl2.Taking into account the dissolution effect and cost,CaCl2-EtOH-H2O is commonly used to dissolve fibroin fibers.After the dissolution of fibroin,the presence of high salinity limits its further use,Therefore,among all units,desalination is considered to be the most difficult and important step in the whole process of fibroin treatment.It isn't only one of the key problems to realize the industrialization of silk fibroin in its application field but also a difficult point.Integrated membrane processes of 'diffusion dialysis-electrodialysis(DD-ED)' were used in the removing CaCl2 from silk fibroin solution.This process was well investigated for objectives of high efficiency and energy saving,and the application of self-made silk protein solution was also explored.In this paper,considering energy consumption and desalination time,not only the change of volume of fibroin solution and deionized water but also the desalination efficiency of ED under different current density and initial concentration of silk fibroin were discussed in single factor experiment.At this stage,a better range of experimental parameters was obtained.After that,on the basis of single factor experiment,the main factors affecting the desalination of soluble silk fibroin solution were investigated by orthogonal experiment,and the results of the experiments were analyzed by the integrated balance method and the comprehensive scoring method.The appropriate operation conditions,hence the 5%silk fibroin concentration,the 10:1 volume ratio of deionized water to silk protein solution,the 40%pre-desalination rate of DD and the 23.8 A/m2 of current density are obtained through the experimental results.As for the flow of silk fibroin solution and deionized water,they are 20L/h and 30L/h during DD,and the both are 30L/h during ED,respectively.It is demonstrated that the desalting processes for the production of silk fibroin protein is efficient,the salt rejection maintained above 99.9%is achieved with a recovery of silk fibroin protein of 91.06%under 9h desalination time.Additionally,the energy consumption is reduced by 50%and the water consumption could decrease by about 88%compared with that of the Electrodialysis and the traditional dialysis bag,respectively.The application of self-made fibroin solution in three aspects was discussed in this paper:silk fibroin gel,silk fibroin powder and the effect of silk fibroin on HaCaT cells.Based on the analysis of SEM of the silk fibroin gel and powder,prepared by self-made solution,verified the silk fibroin can meet the requirements of silk fibroin gel and silk fibroin powder from the surface structure.Moreover,the investigation of effects of self-made silk protein solution on HaCaT cells' growth and the protection after UVB radiation show that the proliferation of silk fibroin solution prepared by this process on HaCaT is similar to traditional dialysis bag desalination method.