Adsorption Performances Of Anionic Dyes With Metal-organic-framework-based Composites

Microporous MOFs could easily hydrolyze and collapse in presence of the moisture,which would restrict its adsorptive separation performances of anionic dye molecules from aqueous.Based on the issues above,mesoporous activated carbon,carbon nanotubes,13X zeolite combined with MOFs were designed and assembled into composites in this paper.In comparison with MOFs,both water-resistant and adsorption performances of the composites were improved,showing the adsorption advantage towards large-size anionic dyes.It opens up a perspective for MOFs application.Three sections of this study are following as below:1.The Zn/Cu-BTC@MC composite was synthesized with the mesoporous activated carbon,the Zn?NO3?2·6H2O,the Cu?NO3?2·3H2O,and the H3BTC through in situ hydrothermal one-pot method.The Zn/Cu-BTC@MC was characterized in detail by N₂ adsorption-desorption,X-ray diffraction?XRD?,Scanning electron microscope?SEM?,Fourier transform infrared spectroscopy?FT-IR?,and Thermogravimetric analysis?TGA?,etc.Due to the bimetal synergistic ability of Zn²⁺and Cu²⁺,the selectivity and uptake capacity of Congo red?CR?dye molecules were enhanced than Zn/Cu-BTC.The maximum CR adsorption capacity of Zn/Cu-BTC@MC?1064 mg/g?has an increase of 20%,the diffusion rate increased by 10 times.The structure morphology of Zn/Cu-BTC@MC remained good at 500?,and the structure began to collapse at 300?compared with that of Zn/Cu-BTC,which improved the thermal stability by 40%.In addition,the Zn/Cu-BTC@MC exhibited a good reusability,and the regeneration efficiency could reached more than 90%of the initial value.Langmuir and pseudo-second-order kinetic models could better describe the adsorption process of CR dye molecules.2.The UiO-67@CNTs mesoporous composite was prepared with Ui O-67 and carbon nanotubes?CNTs?by in-situ hydrothermal synthesis method.The morphology,structure,and main functional groups before and after combination were characterized in detail by N2 adsorption-desorption,SEM,XRD and FT-IR,etc.Because existence of mesoporous,the adsorption diffusion coefficient of CR molecules was increased by10 times than UiO-67,and the maximum adsorption capacity of UiO-67@CNTs was1025 mg/g.In addition,the good water-resistant of UiO-67@CNTs exhibited that the adsorption capacity maintained about 90%after impregnation in water for 7 days.However,the maximum adsorption of UiO-67@CNTs on CR was 30%higher than that of UiO-67 after soaking for 32 days.Langmuir and pseudo-second-order kinetic models could better describe the adsorption process of CR dye molecules.3.Spherical 13X zeolite as the base material,micron-size MOFs coated on the surface of 13X zeolite,four types of core-shell composites?Zn/Cu-BTC@13X,MOF-5@13X,ZIF-8@13X and Ui O-66@13X?were prepared by a in-situ hydrothermal synthesis method.The prepared materials were systematically characterized by SEM,FT-IR,XRD and N2 adsorption-desorption,etc.The MOFs in the composites still maintained their initial properties such as good morphology,crystal structure and functional groups.The tests of batch and dynamic adsorption showed that the order of adsorption capacity of the four materials for methyl orange is Zn/Cu-BTC@13X>MOF-5@13X>ZIF-8@13X>UiO-66@13X.The adsorption capacities were 331,322,160 and 155 mg/g,respectively.The dynamic adsorption experiment shows that the penetration time of UiO-66@13X is 3 times that of 13X and the saturation capacity is 6.7 times.The millimeter-scale feature of MOFs composite opens up a novel perspective for the industrial application of adsorption column.