Synthesis Of Metal-organic Framework (MIL-96) With Different Facets Exposed And Its Adsorption Property On Naphthalene

Polycyclic aromatic hydrocarbons(PAHs),an organic pollutants which is difficult to degrade and can seriously make the water environmernt polluted.Because of serious harm,their presence in the water cycle can make a risk to human health and environmental quality.Therefore,people have a lot of interest in finding an effective adsorbent to remove PAHs.Compared to traditional adsorbents,the advantages of MOFs as adsorbents are their various compositions and structure categories,high specific surface area,and unsaturated or saturated sites to adjust the ability of adsorption.The features make MOFs very promising candidates for removal of PAHs from water.In this paper,we explored the preparation of the aluminum-MIL-96 with different facets exposed and their adsorption property on naphthalene in wastewater.The main contents are as follows:1.A1-MIL-96 materials with different exposed facets(the hexagonal prism with the[001]and[100]facets,the icosahedrons with the[001],[100]and[102]facets as well as the double cone dodecahedron with[102]facet)have been synthesized by changing the molar ratio of metal salt and organic ligand.We described the shape features of the product MJIL-96 in detail,and the influence of stirring rate,reaction time and other factors on the morphology of the product MIL-96 were explored.Otherwise,we used XRD,SEM and JR methods to prove.that we have prepared MIL-96 with different facets exposed successfully.2.We mainly studied the adsorption of naphthalene on MIL-96 with mixed facets exposed(icosahedrons named MIL-96-B)in aqueous solution.The maximal removal efficiency of naphthalene by MIL-96-B with the dosage of 0.5 g/L reached up to 98%at 298K.Adsorption kinetics of naphthalene onto MIL-96-B followed the pseudo-second-order equation for two different initial concentrations of naphthalene.The Temkin and D-R equations can describe the adsorption of naphthalene by MIL-96-B better.The parameter bT in the Temkin equation showed that the adsorption of naphthalene onto MIL-96-B is an endothermic proces,and the positive?H0 in the thermodynamic also proved that the adsorption process is endothermic.The pH ranging from 4 to 10 of solution had no significant effect on the adsorption of naphthalene onto MIL-96-B.Therefore,the efficient removal of naphthalene from aqueous solutions may be attributed to the ?-? interaction between the benzene ring in the organic ligand(trimesic acid)of the MIL-96-B and the benzene ring in naphthalene and the strong hydrophobic environment.Therefore,MIL-96 should be a promising adsorbent that can remove PAHs in aqueous solution efficiently for the future studies.3.We compared the adsorption of naphthalene in aqueous solution onto the MIL-96-A with metal facets exposed and MIL-96-C with ligands facets exposed effectively.By analyzing the results of kinetic equations,adsorption isotherms and thermodynamic parameters,and comparing the rate constant k2 of pseudo-second order equation,we found that the k2 of MIL-96-C is larger than that of MIL-96-A.It indicated that the adsorption rate of naphthalene onto MIL-96-C with ligand facets exposed is faster than that of MIL-96-A with metal facets exposed.Moreover,through the D-R model,we can get the results that maximum adsorption capacity of naphthalene onto MIL-96-A and MIL-96-C was 142.6 mg/g and 502.8 mg/g,respectively.The adsorption process of naphthalene onto MIL-96-A and MIL-96-C were both spontaneous and endothermic.The pH ranging from 4 to 10 had no significant effects on the adsorption of naphthalene onto MIL-96-A and MIL-96-C.Therefore,the differences of the rate constant k2 and the maximum adsorption capacity of naphthalene onto MIL-96 with two different facets exposed,may be attributed to the presence of an excess of ligands on the surface of MIL-96-C.The main mechanism may be that the excessive ligand(trimesic acid)has a strong ?-?interaction with benzene ring in naphthalene and the presence of a strong hydrophobic environment,whereas there are unsaturated metal ions(aluminum ions)on the surface of MIL-96-A,only the organic ligands in the framework forms ?-? interaction with benzene ring in naphthalene.