Synthesis and characterization of magnetic metal–organic framework for the adsorptive removal of Rhodamine B from aqueous solution

• Magnetic metal–organic framework (MOF) was prepared and characterized.
• Magnetic MOFs were used for adsorptive removal of Rhodamine B.
• The adsorption isotherm, kinetics and thermodynamics were studied.
• Magnetic MOFs have high adsorption capacity, good stability, excellent reusability.

Adsorptive removal of Rhodamine B (RhB) on a novel kind of magnetic metal–organic framework (MOF) was studied in view of adsorption isotherm, thermodynamics and kinetics. The adsorbent was characterized by physical property measurement system, X-ray diffraction and scanning electron microscopy. The adsorption isotherm of RhB on magnetic MOF followed the Freundlich model. The resultant kinetics data was well described by the pseudo-second-order model. Most of the RhB was removed from the aqueous solution within 30 min. Thermodynamic parameters including Gibbs free energy, enthalpy, and entropy of adsorption were obtained. The result confirmed that the adsorption is controlled by an entropy effect rather than an enthalpy change. The maximum removal has been achieved in the pH range of 4–8 at 150 rpm. The sorbent can be used at least five times after washing with methanol including HCl (0.001 mol L−1). The π−π stacking interaction and electrostatic interaction may play an important role in the adsorption of RhB onto magnetic MOF. Compared with other adsorbents, this kind of magnetic material demonstrated a superior dye adsorption capability.

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