| With the economical globalization and the rapid development of science and technology,the problem of water pollution with organic pollutants such as dyes and phenols is more and more serious.How to remove the harmful pollutants from the waste water effectively has become an important issue in the field of biology and environment.Adsorption is one of the most efficient technologies as it has the advantages of high processing speed,economic feasibility and recyclability.However,the traditional porous adsorbents,such as activated carbon and zeolite,have poor selectivity and adsorption capacity.Therefore,the development of porous materials with good performance in adsorption is of great significance to the protection of water resources.Metal-organic frameworks(MOFs)are one kind of crystalline porous materials which can be formed self-assembly by interaction between the organic ligands and metal centers.Compared with other traditional inorganic porous materials,MOFs have better performance in adsorption because of large surface area,high porosity,structural and functional diversity and special metal center et.al.Therefore,MOFs have attracted great attention and had great application prospects in the field of adsorption and removal organic pollutants in water to date.In this paper,two kinds of amino-functioned MOFs with excellent properties were prepared and applied to the adsorption of dyes and phenols,respectively,and the possible mechanisms in the process of adsorption were investigated.The main research contents in this paper are as follows:(1)NH2-MIL-101(Fe)was synthesized by solvothermal method,and characterized by FT-IR,XRD,SEM and N2 adsorption desorption tests.NH2-MIL-101(Fe)was used as adsorbent to adsorb cationic and anioic dyes(congo red(CR)and malachite green(MG))from contaminated aqueous solutions in view of the adsorption kinetics,isotherms,thermodynamics.The adsorption follows the pseudo-second-order kinetics and the intraparticle diffusion modle,indicating the existence of chemical adsorption at the initial stage of adsorption,and there are internal particle diffusion and membrane diffusion in the process.The adsorption isotherm was achieved with the Langmuir model.The max equilibrium adsorption amounts of CR and MG on NH2-MIL-101(Fe)are 1386.96 mg·g-1 and 1146.14 mg·g-1,respectively,which are much higher than those of activated carbon.The mechanism in adsorption probably mainly due to the electrostatic interaction;however,hydrogen bonding,?-? stacking interaction and Lewis acid-base reaction cannot be ruled out.The thermodynamic datas of CR or MG on NH2-MIL-101(Fe)show that the process is spontaneous,exothermic and entropy decreasing.(2)NH2-UiO-66(Zr)was synthesized by solvothermal method and characterized by FT-IR,XRD,SEM and N2 adsorption desorption tests.NH2-UiO-66(Zr)was used as adsorbent to adsorb chlorophenols(2-chlorophenol,2,4-dichlorophenol and 2,4,6-trichlorophenol)from wasted water.The adsorption properties and mechanisms were discussed.The sorption kinetics data of chlorophenols were found to be in agreement with the pseudo-second-order modle and intraparticle diffusion modle,indicating the existence of chemical adsorption at the initial stage of adsorption.The mechanism in adsorption may be explained with hydrophobic effect,hydrogen bonding,?-? stacking interaction between chlorophenols and adsorbent.The adsorption isotherm was achieved with the Freundlich model,which means the process was multilayer adsorption.The equilibrium adsorption amounts of 2-chlorophenol,2,4-dichlorophenol and 2,4,6-trichlorophenol on NH2-UiO-66(Zr)are 248.27 mg·g-1,372.11 mg·g-1 and 517.62 mg·g-1,respectively.Thermodynamic data analysis shows that the adsorption process is spontaneous,endothermic and entropy increasing. |
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