| The domestic metallurgical industry plays an important role in the world.With the continuous development of industrial technology,metallurgical enterprises are facing a large number of sewage disposal problems.In the recent years,the country has issued a series of policies to rectify wastewater treatment and discharge pollution in the iron and steel industry.Among of them,metal ions have many damages to human cells,therefore,it is an urgent task to efficiently dispose metal ions from the wastewater for the enterprises.The adsorption method has become a research hotspot on the removal of heavy metal ions,due to its simple operation and the large adsorption capacity.The development of the excellent adsorbents is the hot topic.In this work,a variety of porous materials were shown on the removal of heavy metal ions from water,and the details were as follows:(1)Adsorption performance of commercial zeolites for metal ionsUsing 5A and 13X zeolites as the adsorbents,the adsorption of Zn2+,Fe3+and Cr6+from aqueous solution was studied.The adsorbents were characterized by XRD,FTIR,SEM and gas adsorption apparatus.Kinetic adsorption,isothermal adsorption and optimization of adsorption conditions were studied.It was found that when the p H value was 5 and the original concentration of metal ions was 300 mg·L-1,the adsorption capacities of 13X-2 for Cr6+,Fe3+and Zn2+were 53.32,141.7 and 327.9 mg·g-1,respectively.Subsequently,the adsorption selectivity of 13X-2 was tested in a mixed solution containing a variety of metal ions.The selectivity order of the zeolites was Zn2+>Fe3+>Cu2+>Al3+>Cr6+>Ca2+?Ni2+?Co2+?Mg2+.However,the adsorption removal rate of Cr6+by 13X-2 was only 14.9%.The harmfulness of Cr6+was much higher than that of Zn2+and Fe3+,so it was necessary to further develop novel porous materials for the Cr6+adsorption.(2)Adsorption performance of rare earth metal organic framework for metal ionsRare earth-metal organic frameworks(RE-MOFs)are an important branch of the metal-organic frameworks.The extremely strong water stability of RE-MOFs makes them have the application prospects in the field of metal ions adsorption.In this chapter,Sm-ATC and Sm-DOBDC were synthesized by the hydrothermal method,using samarium nitrate as the metal node,2-aminoterephthalic acid(ATC)and 2,5-dihydroxyterephthalic acid(DOBDC)as the ligands.The crystal structure,surface functional groups,appearance morphology and specific surface area of RE-MOFs was estimated.At the same time,the Cr6+adsorption performance of Sm-ATC and Sm-DOBDC from the solution under the different p H value and initial concentration was studied.Under the p H value of 2 and the metal ion concentration of 10 mg·L-1,Sm-DOBDC has the highest adsorption performance,and the removal rate of Cr6+attained 96.26%.The results showed that Sm-DOBDC has a good application for the removal of Cr6+from the wastewater.(3)Adsorption performance of UiO-66 series MOFs for metal ionsSo far,UiO-66 was one of the stable MOFs,and the ligand has a variety of modifiable properties.In this chapter,UiO-66 was functionalized with-NH2 and-OH groups,and the adsorption process of these MOFs adsorbents on Ni2+,Fe3+and Cr6+in aqueous solution was studied.Among of them,UiO-66-(OH)2 has the highest adsorption capacity,that is 50.4mg·g-1.Subsequently,the influence of the dosage of MOF,the concentration of metal ions and the p H value on the adsorption performance was discussed.At the p H value of 3,the removal rate of Cr6+was 95%,and the adsorption selectivity of Cr6+/Ni2+was 21.7.This might be due to the electrostatic attraction between the protonated hydroxyl on the surface of UiO-66-(OH)2 and the hexavalent chromium anion,namely Cr2O72-,HCr2O7-and HCr O4-ions.The adsorption behavior was more agreeable with the quasi-second-order kinetic model,and the adsorption isotherm was in good agreement with the Langmuir model.The results showed that the UiO-66-(OH)2 adsorbent has a great potential for the selective removal of Cr6+from the aqueous solution. |
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