Preparation And Adsorption Properties Of Sulfur-modified Chitosan/NCC Airgel

With the rapid development of economy,large quantities of waste water with heavy metal ions was released by various chemical industrie s such as papermaking,printing,electrolytic plating and so on.The heavy metal ions in waste water is less easy to be degraded and more enriched,which would cause serious harm to human and the ecological environment.Therefore,seeking a method of heavy ions removal with the characteristic of efficiency,environmental protection and economic is particularly important.Recently,aerogels and nano-materials,which have large specific surface area and numerous adsorption sites,have attracted more and more attention.Aerogel is a porous three-dimensional network structure with specific surface area,which has more space and is easy to fix microbial and functional particles.NCC with a large specific surface area,high reactivity,and small size,is a good adsorbent of heavy metal ions adsorption.C hitosan has two types of reactive functional groups present in chitosan?amino group and hydroxyl group?.And chitosan can excellently interact with heavy metal ions in solutions through adsorption,such as hydrogen bond,chelate and others.However,it is difficult to directly apply the raw chitosan for removal of metal ions in waste water treatment because of its disadvantage such as swelling and unsatisfying mechanical property.To improve the adsorption capacity,it's necessary to modify the chitosan.Therefore,chitosan was used as the raw material to modifiy it.Then,the aerogel with excellent performance was prepared by NCC for the removal of heavy metal ions.Firstly,in this paper,sulfur-modified chitosan was successfully synthesized by grafting Dimethyl 3,3'-Dithiodipropionate onto chitosan.The structure and properties of chitosan and sulfur-modified chitosan were characterized by FT-IR,1H NMR,XRD,TG and EDS.The FT-IR?1H NMR and EDS showed chitosan molecules has been successfully introduced into Dimethyl 3,3'-Dithiodipropionate.The XRD and TG showed that the crystallinity and thermal stability of sulfur-modified chitosan decreased.Secondly,with chitosan and sulfur-modified chitosan as raw material,chitosan aerogel and sulfur-modified chitosan aerogel were synthesized.The structure and morphology of two adsorbents were characterized by FT-IR,XRD,TG,SEM and BET.The Hg²⁺ adsorption behavior on the two adsorbents had been studied under various conditions such as p H,initial concentration,contact time and amount of adsorbent.Results showed that the maximum adsorption capacities of Hg²⁺ were found at pH 5,adsorbent dosage 30.0 mg,initial concentration of metal ions 100 mg/L.And the adsorption capacity of sulfur-modified chitosan aerogel increased by 34.2% than unmodified chitosan aerogel.The adsorption for Hg²⁺ conformed to the pseudo-second-order kinetics,Langmuir isotherm models,and spontaneous endothermic process.The adsorbent could be recycled with EDTA.Lastly,with NCC and sulfur-modified chitosan as raw material,sulfur-modified chitosan/NCC composite aerogel were synthesized.The structure and morphology of composite aerogel was characterized by SEM and BET.The Hg²⁺adsorption behavior on the two adsorbents had been studied under various conditions such as pH,initial concentration,contact time and amount of adsorbent.Results showed that the maximum adsorption capacities of Hg²⁺ were found at p H 5,adsorbent dosage 30.0 mg,initial concentration of metal ions 100 mg/L.And the adsorption capacity of composite aerogel increased by 2.0 2% than sulfur-modified chitosan aerogel.The adsorption for Hg²⁺ followed the pseudo-second-order kinetics,Langmuir isotherm models,and spontaneous endothermic process.The composite aerogel could be recycled with EDTA.