Preparation of Cu-BTC@Fe3O4 Composites for the Thermodynamics and Kinetics Performance on Xylene Isomers Adsorption

Magnetic Cu-BTC@Fe3O4 materials were synthesized as core-shell nanocomposites through a secondary growth technique by the combination of magnetic Fe3O4 and Cu-BTC, which effectively improved the thermal stability of the materials. The interaction energy of Cu-BTC and Cu-BTC@Fe3O4 with the xylene isomers, o-xylene (OX), m-xylene (MX) and p-xylene (PX), was calculated by DFT method, which were consistent with the results of the experimental adsorption separation results. In order to study the adsorption performance of xylene isomers on Cu-BTC@Fe3O4 composite materials, the thermodynamics and kinetics were systematically studied. The adsorption equilibrium curves were obtained by collecting the gas phase adsorption equilibrium data at different temperatures (298, 318 and 338 K) and being fitted with Langmuir and Freundlich isothermal models, respectively, in which the Langmuir isotherm equation was fitted well. Further thermodynamic calculations indicated that the affinity of xylene on Cu-BTC@Fe3O4 is spontaneous physical adsorption combining exothermic process, while kinetic studies showed the adsorption of xylene isomers on Cu-BTC@Fe3O4 a pseudo-second-order kinetic model. In breakthrough experiments, Cu-BTC@Fe3O4 has a high adsorption capacity and selectivity (3.3 for OX/MX) at 453 K, 1.0 MPa.