Preparation And Application Of Natural Polysaccharides Crosslinking Modification Materials

In this paper,natural polysaccharides,which have a large number of active groups on the molecular chain(hydroxyl groups,amino groups,etc.),were crosslinked with glutaraldehyde and vanillin to prepare novel adsorbents and self-healing materials.Then,the structural characterizations of these crosslinked materials were investigated by FT-IR,TGA,SEM,BET,AFM and so on.At the same time,the adsorption properties and self-healing properties,the influencing factors,and the intrinsic mechanism were explored.The main conclusions were as follows:(1)The results of FT-IR,TGA and SEM showed that RCSA,PEI-RC,PEI-RCSA were all successfully prepared through glutaraldehyde cross-linking reaction.The three aerogels obtained by the freeze-drying all exhibited a loose porous network structure.The adsorption of heavy metal ions is mainly related to the active groups O-H,N-H,and-COO-.(2)The results of static adsorption experiments showed that the three adsorbent materials can adsorb Cu2+,Zn2+,and Pb2+ in the solution.In particular,the adsorption capacity of the two adsorbent materials that were functionalized with polyethyleneimine was significantly improved.The adsorption of Cu2+,Zn2+,and Pb2+ by the three materials was followed by pseudo-second-order kinetic model,which indicated that the adsorption process was a chemical-based process.The maximum adsorption capacities of RCSA for Cu2+,Zn2+,and Pb2+ in single system by the Langmuir isotherm model were 3.5,3.1,and 8.7 mg·g-1,respectively,the maximum adsorption capacities of PEI-RC were 163.6,90.2 and 208.2 mg.g-1,and the maximum adsorption capacities of PEI-RCSA were 177.1,110.2 and 234.2 mg.g-1.The three adsorbents all showed a dependence on the pH of the aqueous solution due to the fact that the active groups that adsorb heavy metal ions in aqueous solutions with low pH were affected.All the three adsorbents had reproducible properties.The regeneration of PEI-RC and PEI-RCSA will be better using Na2EDTA due to the structure.stability of the Schiff base.(3)Chitosan can be cross-linked with vanillin.The results,of FT-IR and XRD showed that there were both reversible Schiff base and physical hydrogen bond structure in the hydrogel network,and it is necessary to control the amount of cross-linker vanillin to obtain hydrogels with self-healing properties.The experiment found that the gel formed by adding 0.3 g of vanillin to 10 ml of 5%(w/v)chitosan solution had good self-healing ability and had a certain mechanical strength,and the gel time was also suitable for about 6 min:Lower vanillin concentration led to a weak and tacky hydrogel without any practical application value,while higher vanillin concentration resulted in a strong substance without any self-healing behavior.