Preparation of AC/Cu-BTC composite and its adsorption mechanisms

The copper-based metal organic framework Cu-BTC (Copper Benzene-1,3,5-tricarboxylate) was synthesized by the solvothermal method, and AC/Cu-BTC composites were prepared by introducing different proportions of activated carbon (AC) into the reaction process by in situ synthesis. Various measures, including the use of an X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FT-IR), scanning electron microscope (SEM), and N2 adsorption apparatus were applied to characterize the structure, morphology, and surface area of Cu-BTC and AC/Cu-BTC. The adsorption properties and mechanism of methylene blue (MB) and methylene orange (MO) onto Cu-BTC and AC/Cu-BTC were studied. The results showed that Cu-BTC and AC/Cu-BTC have the same octahedral structure. The adsorption amount of MB onto AC/Cu-BTC composites was higher than that of Cu-BTC. The adsorption of MB onto Cu-BTC and AC/Cu-BTC was much higher than MO. The adsorption isotherms of MB and MO onto Cu-BTC and AC/Cu-BTC could be described by the Langmuir model, while the adsorption kinetics of the two adsorbents followed the pseudo second-order model. The negative values ΔH and ΔG illustrate the spontaneity and exothermicity of the process. The adsorption amount of MB on AC/Cu-BTC decreased from 49.39 to 32.45 mg/g after 3 cycles of reuse.