Evaluation of MOF-5 as an adsorbent material for the removal of cadmium from aqueous solution

The presence of cadmium (Cd(II)) in the environment is one of the most important concerns worldwide due to its high toxicity to human health. In this work, an adsorbent material called metal-organic framework-5 (MOF-5) was synthesized by solvothermal route for its use in removing Cd(II) from water. This material was characterized by scanning electron microscopy (SEM), Energy Dispersive X-ray spectroscopy, Fourier Transform Infrared Spectroscopy and X-ray diffraction techniques before and after adsorption tests. SEM analysis showed that MOF-5 presents needle-shaped crystalline clusters associated with the synthesis method. After the adsorption process, changes in morphology and composition were detected, confirming the presence of Cd(II) in the material and the possible dissolution of the MOF-5 constituents. The Cd(II) adsorption experimental data on MOF-5 at pH 7 and 25 °C were fitted to the Langmuir isotherm model and the pseudo-second order kinetic model. The proposed adsorption mechanisms correspond to ion exchange, chemisorption and cation-π interactions.