Preparation Of Soy Protein Aerogel And Its Adsorption Application

The aerogel has shown great potential application in many high-tech fields for its special properties.The development of aerogel from renewable biomass,as a promising alternative to petro-based aerogel,has therefore attracted considerable attention in recent years.Soy protein,a form of renewable biomass derived from defatted soybean residue,is characterized by its low cost and better gel properties.Soy protein could be an ideal raw material for preparation the aerogel.The sol-gel process was employed to prepare aerogel.Adehydes were used as crosslinking agent of soy protein to prepare soybean protein gel,then the aerogels were achieved after freeze-drying vacuum.The influence of preparation parameters(cross-linking agents and techniques)on pore structure(BET specific surface area,pore volume,pore pattern,pore size distribution,etc.),adsorption properties of nitrophenol,Cr(VI),H2 of soy protein aerogel were investigated.The results could provide the references for the further research and industrial application of the similar aerogel which use vegetable protein as raw material.The results showed that:1.The gel time decreased with the increase of adding amount of cross-linking agents(formaldehyde,glyoxal,and glutaraldehyde).When adding amount of cross-linking agents exceeded 0.0125 mol,the gel time of add glutaraldehyde was the shortest.The cross-linking agent was hardly dispersion when the gel time lower than 2 min.With the increase in the amount of crosslinking agent,the bulk density of aerogel powder showed increased at first,then decrease;but the BET specific surface area presented a rising trend,when dosage exceeded 0.0125 mol,some changed.The aerogel powder can not reach the structure standard of traditional aerogel,its pore structure may be destroyed by making aerogel into tiny particles2.Formaldehyde,glyoxal,glutaraldehyde could be use as cross-linking agents to form gel structure.The gel was then treated by freezing in refrigerator or liquid nitrogen to obtain aerogel which contains a lot of micron grade circular pore and small amounts of nanoscale slit after dry vacuum.The freezing treatment had a greater influence on the pore structure than aldehydes did.The sample freezing in liquid nitrogen had a greater adsorption quantity,a more uniform pore structure,more mesoporous and more narrow pore size distribution.The optimal technology to prepare soy protein aerogel was using glutaraldehyde as crosslinking agent to form gel then freezing in liquid nitrogen.Aerogel prepared by this technology had a higher stability in high temperature and the potential to further improvement.3.Nanoscale porous materials---soy protein aerogel,which pore size distribution mainly in 15～25 nm and BET specific surface area in 106～128 m2/g,could be obtained by aging and solvent replacing glutaraldehyde-crosslinked gel after dry vacuum.The ageing agent,glutaraldehyde,changed the structure of the gel.With the increase of aging agent’s mass fraction,both BET specific surface area and pore volume rising at first then go down.The effect on the surface groups by different mass fraction ageing agent to treat is not obvious.But compared with aerogel without glutaraldehyde aging,the aerogel via glutaraldehyde to aging had higher thermal stability at temperature over 400 C.SEM images showed that soy protein gel structure is mainly composed of particles accumulate,the network structure is not very transparent in aerogel,there is further room for improvement.4.All kinds of soybean protein aerogel had a adsorption effect on H2,n itrophenol,and Cr(VI)in water.The bigger of pore volume and BET specific surface area,the greater of adsorption quantity.The mass fraction of ageing agent to obtain aerogel that have the the maximum adsorption was 0%.The maximum adsorption of aerogel on H2 at atmospheric pressure was 10.85 cm3/g,and it had a removal rate of 15.27%,5.81%on nitrophenol and Cr(Ⅵ)in water,respectively.