Superior Adsorption Efficiency of Mil-101 (Cr) and Nano-Mil (Cr) in Anionic and Cationic Dye Removal From Aqueous Solution

Abstract

Metal-organic frameworks (MOFs) as adsorbent have received considerable attention due to their remarkably high porosity, adjustable pore shape/size, and surface functionality. This study focusses on the adsorption performance and mechanism of two different typological and structural MOFs as superior adsorbents for the efficient removal of anionic and cationic dyes in an aqueous solution. MIL-101(Cr) and nano-MIL-101(Cr) were successfully synthesized by the hydrothermal method using two different protocols and both materials were confirmed by XRD, TG-DTA-DTG, FTIR and SEM analyses. The adsorption kinetics and isotherms were determined from the experimental data obtained under optimal conditions. The adsorption kinetics suggests the adsorption process of Congo Red (CR) and Thioflavin T (TFT) onto MIL-101 (Cr) and nano-MIL-101(Cr) conformed to the pseudo-second-order kinetic model. The Langmuir isotherm agrees well with the experimental data, and the adsorption capacities for MIL-101 (Cr) and nano-MIL-101 (Cr) were found to be 986 mg g(-1) (CR) and 863 mg g(-1) (TFT), 1004 mg g(-1) (TFT), respectively. The adsorption mechanism is to be related to pi-pi stacking, hydrogen bonding, pore filling, electrostatic interaction, and partial chemical interaction. This study demonstrates that MIL-101 (Cr) and nano-MIL-101 (Cr) are promising reusable adsorbents with high adsorption capacity for removing dyes from aqueous solutions.