Study On Preparation And Adsorption Properties Of Attapulgite-based Silk Fibroin Composite Aerogel

Polysaccharides from aquatic animals have attracted wide attention due to their excellent antioxidant,anti-tumor,anti-inflammation and immune-enhancing biological activities.However,protein removal is the technical bottleneck that restricts the extraction of polysaccharides from aquatic animals.At present,the commonly used deproteinization technologies have the disadvantages of high cost,long time consumption,and introduction of organic reagents.In this paper,the natural one-dimensional nanomaterial attapulgite as the main material and silk fibroin as the auxiliary material were used to prepare attapulgite/silk fibroin composite aerogel?ATP/SF-CA?.Silk fibroin endowed the aerogel microenvironment with abundant amino,carboxyl and other organic functional groups,which laid a good material foundation for selective adsorption and separation of proteins.Attapulgite fiber gave aerogel an ideal micro-nano three-dimensional pore structure,which fully guaranteed the efficiency of selective adsorption and separation.The preparation of ATP/SF-CA was discussed,and its selective adsorption performance and adsorption mechanism for proteins in crude polysaccharides from Meretrix meretrix L.were studied in this paper.An environmentally friendly,highly efficient and highly selective method was developed to remove protein impurities from crude polysaccharides by ATP/SF-CA adsorption.The main research contents and conclusions were as follows:1. Preparation and Characterization of Attapulgite/Silk fibroin Composite Aerogel?ATP/SF-CA?ATP/SF-CA was prepared by physical blending and freeze-drying,and a series of characterization methods including SEM,FT-IR,BET,XRD were performed to investigate its macro-microscopic morphology and internal structure characteristics.The experimental results showed that the conformation of silk fibroin gradually changed from?-helix to stable?-sheet morphology,forming silk fibroin with good mechanical properties and the three-dimensional porous network structure with attapulgite as the framework of ATP/SF-CA.Its large specific surface area and the presence of a large number of micropores and mesoporous in the interior laid the foundation for further adsorption.2. Study on Selective Adsorption Performance of Copper ion Chelated Aerogel(ATP/SF-CA-Cu²⁺)ATP/SF-CA-Cu²⁺was prepared by copper ion chelation method,and then applied to the selective adsorption and separation of protein impurities in crude polysaccharide solution based on the principle that copper ions could form the stable covalent bond with proteins.The experimental results showed that the fixation of copper ions on the surface of ATP/SF-CA was verified by EDS.The single factor experiments were designed with the selectivity coefficient as index to evaluate the optimal conditions for protein adsorption by ATP/SF-CA-Cu²⁺:adsorbent dose was 1.4%,adsorption temperature was 30?,p H value was 5.0 and adsorption equilibrium time was 15 min.Under these conditions,the deproteinization rate was 93.5±1.02%,the polysaccharide retention rate was 93.59±0.85%,and the selectivity coefficient was 14.59±0.64.Compared with Sevag deproteinization method,ATP/SF-CA-Cu²⁺adsorption method could greatly reduce the loss of polysaccharides and shorten the deproteinization time without damaging the structure,molecular weight and composition of the original polysaccharides.3. Study on Selective Adsorption Performance of Attapulgite/Silk fibroin Composite Aerogel?ATP/SF-CA?ATP/SF-CA had large specific surface area and rich functional groups.In addition,silk protein was a kind of polyamino acid with amphoterically charged effect.Aquatic animal protein molecular determinants form a complementary configuration with silk fibroin molecule variable region,resulting in a strong specific affinity between the two molecules.ATP/SF-CA was applied to the selective adsorption and separation of protein impurities in crude polysaccharide solution based on its aerogel microenvironment.The experimental results showed that the optimal conditions for ATP/SF-CA adsorption of proteins were evaluated by single factor experiments were:adsorbent dose was 1%and p H value was 7.0.Under these conditions,the deproteinization rate was 77.88±2.02%,the polysaccharide retention rate was 96.83±2.62%and the selectivity coefficient was 18.68±0.42.Quasi-second-order kinetic model and Freundlich thermodynamic model could better fit the adsorption process of ATP/SF-CA on proteins,which was a spontaneous endothermic process driven by entropy.