Nickel and iron-based metal-organic frameworks for removal of organic and inorganic model contaminants

Metal-organic frameworks (MOFs) are a promising class of porous nanomaterials in the field of environmental remediation. Ni-MOF and Fe-MOF were chosen for their advantages such as structural robustness and ease of synthesis route. The structure of prepared MOFs was characterized using FE-SEM, XRD, FTIR, and N2 adsorption-desorption. The efficiency of MOFs to remove organic model contaminants (anionic Alizarin Red S (ARS) and cationic malachite green (MG) and inorganic fluoride was studied. Fe-MOF and Ni-MOF adsorbed 67, 88, 6% and 32, 5, and 9% of fluoride, ARS, and MG, respectively. Further study on ARS adsorption by Fe-MOF showed that the removal efficiency was high in a wide range of pH from 3 to 9. Moreover, dye removal was directly increased by adsorbent mass (0.1-0.75 g/L) and decreased by ARS concentration (25-100 mg/L). The pseudo-first-order kinetic model and Langmuir isotherm model with a qmax of 176.68 mg/g described the experimental data well. The separation factor, KL, was in the range of 0-1, which means the adsorption process was favorable. In conclusion, Fe-MOF showed remarkable adsorption of organic and inorganic model contaminants.