Enhanced sequestration of an acidic dye on novel bimetallic metal-organic framework

Abstract

Paper reports the improved adsorption efficiency of Fe-based MOF in the dye removal of Eosin using Cu doping. We used the solvothermal route to synthesize the Cu-Fe-BDC MOF and used multiple techniques for its structural and microstructural characterization including FTIR, XRD, SEM, EDS, and TEM. The effect of various process parameters such as pH of the solution, the concentration of adsorbent, temperature, etc., have also been systematically analyzed in dye removal efficiency. Cu doping is found to enhance the adsorption of Eosin from 3.23 mg/g in Fe-BDC to (46.296 ± 1.389) mg/g in Cu-Fe-BDC MOF. The dye uptake varies with pH and is maximized for pH 6. Enhancement in uptake capacity with increased temperature indicates the endothermic nature of the process. Various adsorption isotherm and kinetic models were used to fit the data of the adsorption process. The data efficiently fitted in the Freundlich and pseudo-second-order models, respectively. The adsorption capacity of developed mixed MOF was found higher in column run in comparison to batch capacity. It was successfully regenerated and reused for up to five cycles. Bulk removal of the dye was measured through column operations and the adsorption capacity of developed mixed MOF was found higher in comparison to batch studies. Based on five consecutive adsorption-desorption cycles, it is established that the prepared MOF is a robust material that can act as a highly efficient adsorbent for the removal of the dye Eosin.