SYNTHESIS, CHARACTERIZATION, AND APPLICATION OF Ca-MOFs IN THE REMOVAL OF METHYLENE BLUE VIA ADSORPTION

Abstract

Metal-organic frameworks (MOFs) based on Calcium-terephthalate(Ca-MOFs) were synthesized by the sonochemical method and applied to remove methylene blue (MB) from an aqueous solution via adsorption. The samples were prepared and characterized by X-ray Powder Diffraction (PXRD), Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), Thermal Analysis (TGA-DTA), and Scanning Electron Microscopy (SEM). The studied of the effect of the synthesis temperature on the crystallization of MOFs indicated two different crystal structures were identified, Ca(BDC) and Ca(BDC)(H2O)3. Observed that samples with a higher proportion of the Ca(BDC) phase showed greater dye adsorption capacity. The experimental data fit the pseudo-second-order kinetic model. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms, and the isotherm constants were also determined. The adsorption equilibrium data preferably fit the Freundlich model. The samples were applied to methylene blue adsorption at pH 5.6, with maximum adsorption of 60.241 μmol.g-1 and high reuse efficiency, reaching 97% of the initial adsorption capacity in the second reuse cycle.