Chemical Modification Of Chitosan Oligosaccharide And Its Ammonia And Phenol Adsorption Porperties

According to the "Cigarette Harm Reduction Technology" reports of National Tobacco Monopoly Bureau,ammonia and phenol are the main harmful components in cigarette mainstream smoke and may damage the health of human body.Reducing ammonia and phenol in cigarette smoke has received extensive attention.Chitosan oligosaccharide,the degradation product of chitosan,has varies of excellent properties such as non-toxic,biocompatible,biodegradable and antibacterial.It is an efficient and safe sorbent.In this thesis,we used chitosan oligosaccharide as raw material,and studied its chemical modification,properties and adsorption of ammonia and phenol in cigarette mainstream smoke.(1)Study on synthesis of poly(acrylic acid)grafted chitosan oligosaccharide(OCS-g-PAA)and its adsorption properties.By controlling the molar ratio of chitosan oligosaccharide unit to acrylic acid monomer and the reaction time,four OCS-g-PAA sorbents with different degree of carboxyl substitution(DS)were synthesized through graft copolymerization,using potassium persulfate as initiator.The chemical structure of OCS-g-PAA was characterized by 1H-NMR and FT-IR,and the DS of each sample was also determined.The thermal stability of OCS-g-PAA was studied by TGA.The crystallinity of chitosan oligosaccharide before and after graft copolymerization was compared by XRD.The results of adsorption test showed that both the ammonia adsorption property and the phenol adsorption property of OCS-g-PAA increased with the increase of DS.When DS was 0.531,30 mg of OCS-g-PAA were able to adsorb 9.14%of ammonia and 7.51%of phenol in mainstream smoke.(2)Study on synthesis of maleic acid grafted N-phthaloylated chitosan oligosaccharide(POCS-g-MA)and its adsorption properties.The intermediate product,N-phthaloylated chitosan oligosaccharide(POCS),was synthesized through the amidation between chitosan oligosaccharide and phthalic anhydride.Then maleic acid was grafted onto POCS via O-acylation reaction.By controlling the molar ratio of chitosan oligosaccharide unit to maleic anhydride,three POCS-g-MA sorbents with different degree of maleic acid substitution(MDS)were synthesized.The chemical structure of POCS and POCS-g-MA were characterized by 1H-NMR and FT-IR,and the MDS of each sample was also determined.The thermal stability of POCS and POCS-g-MA were studied by TGA.The crystallinity of chitosan oligosaccharide before and after N-amidation and O-acylation were compared by XRD.According to the results of adsorption test,the the ammonia adsorption property of POCS decreased while the phenol adsorption property increased compared to chitosan oligosaccharide.And both the ammonia adsorption property and the phenol adsorption property of POCS-g-MA increased with the increase of MDS.When MDS was 0.392,30 mg of POCS-g-MA were able to adsorb 27.98%of ammonia and 17.00%of phenol in mainstream smoke.(3)Study on preparation of multi-porous epichlorohydrin crosslinked chitosan oligo-saccharide and its adsorption properties.The multi-porous epichlorohydrin crosslinked chitosan oligosaccharide was prepared by emulsion solidification and freeze-drying method by using epichlorohydrin as crosslinker and the polyethylene glycol as porogen.By controlling the reaction temperature,the amount of epichlorohydrin and the amount of polyethylene glycol,series of multi-porous epichlorohydrin crosslinked chitosan oligosaccharide sobents were prepared.The chemical structure,thermal stability and crystallinity of the sorbents were characterized by FT-IR,TGA and XRD.The effect of different preparation conditions on surface morphology and specific surface area of the sorbents was also studied.The results of adsorption test showed that both the ammonia adsorption property and the phenol adsorption property of multi-porous epichlorohydrin crosslinked chitosan oligosaccharide increased with the increase of specific surface area.When the specific surface area was 0.4647 m2/g,30 mg of multi-porous epichlorohydrin crosslinked chitosan oligosaccharide were able to adsorb 31.76%of ammonia and 28.07%of phenol in mainstream smoke.