Synthesis and adsorption performance of MIL-101(Cr)/graphite oxide composites with high capacities of n-hexane

Abstract

MIL-101(Cr)/graphite oxide (GO) composites (MIL-101@GO) were synthesized by a solvothermal synthesis method. The synthesized materials were characterized by X-ray diffraction, scanning electron microscopy, adsorption of nitrogen, FT-IR spectroscopy and thermal analysis. The isotherms of n-hexane on the MIL-101@GO composites and the MIL-101 were measured by a gravimetric method separately. Experiments of multiple adsorption–desorption cycles were conducted to estimate reversibility of n-hexane on the MIL-101@GO. Results showed that the Langmuir surface area of the composites was higher than that of the pure MIL-101, and the adsorption capacities of n-hexane on the MIL-101@GO-5 and MIL-101@GO-10 were greatly higher than that on the MIL-101 sample. The isotherms of n-hexane could be fitted favorably by the Langmuir–Freundlich equation. The composite MIL-101@GO-5 exhibited the maximum n-hexane uptake of 1042.1mg/g at 298K, which increased by 93% in comparison with that of the MIL-101, and was much higher than those of the conventional activated carbons and the zeolites. The great improvement of n-hexane adsorption capacity can be attributed not only to an increase in the surface area of the MIL-101@GO, but also to an increase in the surface dispersive forces of the MIL-101@GO due to the introduction of the GO with dense arrays of atoms. Consecutive cycles of adsorption–desorption experiment showed that the desorption efficiency could reach 96.78% for the five cycles, indicating that the MIL-101@GO-10 had excellent reversibility of n-hexane adsorption.