| Heavy metals and dyes are two common types of pollutants that are seriously harmful to the ecological environment and human health.The application of adsorption method to remove pollutants in aqueous solution has the advantages of high efficiency,simple operation,low cost and reusability.Therefore,the development of various new adsorbents has become one of the research hotspots of adsorption methods.Diethyltriamine pentaacetic acid?DTPA?is not only a highly efficient heavy metal chelating agent,but also a crosslinking agent for chitosan molecules.In order to further improve the adsorption performance and stability of chitosan/graphene oxide composite adsorbent,DTPA-chitosan/graphene oxide composite adsorbent?DC/GO?was synthesized by“one-pot method”.It is also used for the removal of heavy metal copper and cationic dye methylene blue in aqueous solution.The specific research results are as follows:1)Several DTPA-chitosan/graphene oxide composites synthesized are DC/GO-1,DC/GO-2,DC/GO-3,DC/GO-4,respectively.The ratio of chitosan to graphene oxide decreases in turn,while DPCS is DTPA-chitosan which does not contain graphene oxide.The composition and structure of the materials were characterized by FTIR,BET,SEM and XRD,and the effects of the ratio of chitosan to graphene oxide on the adsorption of copper ions and methylene blue on the composites were investigated.The results show that the adsorption properties of the composite adsorbents DC/GO-1 and DC/GO-2 are improved compared with DPCS.2)The adsorption properties of DPCS,DC/GO-1 and DC/GO-2 on copper???ions in aqueous solution were studied.The maximum adsorption capacities of DPCS,DC/GO-1 and DC/GO-2 for copper???ions in aqueous solution are 80.9 mg·g-1,105.5 mg·g-1 and 88.3mg·g-1,respectively.The adsorption kinetics of the materials followed the pseudo-second-order kinetic model.The isothermal adsorption data of DPCS accorded with the Langmuir isotherm model,while DC/GO-1 and DC/GO-2 conformed to the Freundlich model.3)The adsorption properties of DPCS,DC/GO-1 and DC/GO-2 on methylene blue in aqueous solution were investigated.The maximum adsorption capacities of DPCS,DC/GO-1 and DC/GO-2 for methylene blue in aqueous solution were 749.3 mg·g-1,924.8 mg·g-1 and799.2 mg·g-1,respectively.The kinetics followed the pseudo-second-order kinetic model,while the isothermal adsorption data were consistent with the Langmuir isotherm model.4)The re-use performance of DC/GO-1 was studied.The removal rate of copper ions and dye methylene blue was still more than 82%after repeated five times.5)Observe the sedimentation effect of DC/GO series adsorbent in dye and copper ion system.The sedimentation effect of DC/GO composite is better than DPCS or pure GO.6)The adsorption of DPCS,DC/GO-1,DC/GO-2,DC/GO-3 and DC/GO-4 on the two-component system of copper ion and methylene blue was investigated.The adsorption of copper ion by composite materials was mainly based on the chelation of DTPA with carboxylic acid groups on GO,and the adsorption of dyes was mainly based on electrostatic attraction.Copper ion is preferentially adsorbed by composite materials,and the change of copper concentration will affect the adsorption of methylene blue,while the change of methylene blue concentration will not affect the adsorption of copper ion. |
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