Preparation And Adsorption Evaluation Of Pullulan Gel Carrier For Composite Adsorbents

With the development of industry,more and more toxic sewage has been produced,among which the sewage containing heavy metal ions and dyes are two kinds of representative pollutants.Before discharge into the environment,toxic sewage must be treated innocuously to protect the ecological environment and human health.Because of the advantages of low cost,low requirements for instruments,strong maneuverability and good environmental compatibility,adsorption method has become the most practical and effective method for the treatment of toxic sewage.In this paper,in order to solve the above problems,the composite adsorbent with excellent properties was synthesized and its physicochemical properties,adsorption properties and adsorption mechanism were analyzed in detail.The content of the study is divided into two parts:(1)Polydopamine-doped pullulan gel for adsorption of copper ionsIn this study,polydopamine-doped pullulan polysaccharide gel was constructed to remove heavy metal copper ions from aqueous solution,to solve the defects that the use of polydopamine adsorbent alone will produce a large amount of sludge.In this paper,the adsorption mechanism,material advantages were carefully analyzed,then the physical and chemical properties of the material were characterized,and finally the adsorption capacity and adsorption mechanism were measured and analyzed.The results show that the pore size,mechanical strength,swelling and adsorption properties of hydrogel composite adsorbents can be precisely controlled by adjusting the concentration of polydopamine in the hydrogel.The synthesized adsorbent has a large adsorption capacity for heavy metal copper ions with a maximum adsorption capacity of 100.9 mg/g,and the adsorption mechanism analysis shows that the adsorption is more in line with the second order kinetic model and the Freundlich isotherm model.(2)Polydopamine/montmorillonite doped pullulan gel for adsorption of crystalline violetIn this study,a polydopamine/montmorillonite double adsorbent doped renewable pullulan polysaccharide hydrogel was constructed to remove crystalline purple dye in aqueous solution.The mechanical strength of the synthesized composite adsorbent can be effectively regulated by the co-doping of polydopamine and montmorillonite double adsorbent to enhance its practicability.The experimental contents are mainly divided into the synthesis of adsorbents,the characterization of physicochemical properties,the characterization of adsorption properties and the analysis of adsorption mechanism.We noticed that the physicochemical properties(swelling properties,microarchitecture and mechanical strength)of prepared composite hydrogel absorbents were strongly related to the PDA/MMT mass ratio in pullulan-gels.Meanwhile,the data of CV adsorption onto PM hydrogels well described by Freundlich model(R~2=0.98503)and PSO kinetic model(R~2=0.99844),and the maximum adsorption capacity was 113.99 mg/g.