Study On Preparation And Adsorption Performances Of Chitosan/Gum Tragacanth Hydrogels

The problem of water environment pollution with the rapid development of industry is becoming more and more serious.The adsorption method is one of the commonly used methods of water treatment due to its low cost,high efficiency and simple operation.Among them,hydrogels have become widely studied adsorbents,with the advantages of large specific surface area,high water absorption,and good biocompatibility.Hydrogel adsorbents were low-cost,environmentally compatible and more easily degradable which prepared from natural macromolecular materials.Chitosan and gum tragacanth are non-toxic and renewable natural polysaccharide products,which are easy to be chemically modified and have certain applications in waste water treatment.And the modification and organic combination of the two will play an efficient role in environmental pollution control and have broad application prospects.Based on the above background,in this thesis,chitosan and gum tragacanth were used as main raw materials to prepare three kinds of composite hydrogels,and the adsorption performances under different conditions were studied as adsorbents for removing different metal ions.Firstly,the poly（gum tragacanth-N,N-dimethylacrylamide）hydrogel（p（GT-DM AA））,chitosan/poly（gum tragacanth-N,N-dimethylacrylamide）composite hydrogel（CS/p（GT-DMAA））,and the poly（gum tragacanth-carboxymethyl chitosan）double network composite hydrogel（p（GT-CMCS））were prepared,its chemical and morphological structures were characterized by FTIR,SEM and XRD.In addition,the swelling properties under different conditions were tested and the optimum synthesis conditions were explored.Meanwhile,the adsorption capacity of iron,nickel,manganese chromium and cadmium ions were studied by ultraviolet visible spectrophotometry,and the adsorption process,adsorption mechanism and recycling times were also discussed.The results showed that the CS/p（GT-DMAA）hydrogel has better adsorption effect on Mn²⁺and Cd²⁺ion,the adsorption amounts were 50.15 mg/g and 51.81 mg/g respectively.The p（GT-CMCS）hydrogel has better adsorption effect on Fe³⁺,Ni²⁺and Cr⁶⁺ion,the adsorption amounts were 62.61 mg/g,68.17 mg/g and 98.31 mg/g respectively.The adsorption processes of Cr⁶⁺ions with three hydrogels were in accord with the pseudo-second-order kinetic model and Langmuir isotherm adsorption model.After 7 cycles of recycling,the adsorption rate of Cr⁶⁺with p（GT-CMCS）hydrogel can still reach more than 90%.The adsorption properties of the five heavy metal ions with the three kinds of hydrogels were excellent,which had the prospects in future research for the treatment of heavy metal water.