Comparative study of the physicochemical properties of metal organic frameworks in the adsorption of textile dyes

The main objective of this study was to evaluate the adsorption properties of three different Metal Organic Frameworks (MOFs), a class of highly porous materials composed of metal ions and organic linkers, for the removal of acid, basic, and reactive textile dyes from aqueous solutions. Specifically, the removal of acid blue 25 (AB25), basic blue 3 (BB3), and reactive blue 4 (RB4) from aqueous solutions was evaluated using MIL-101(Fe), MIL-100(Fe), and HKUST-1 MOFs. Each MOF was synthesized and physicochemically characterized prior to the experimental quantification of adsorption isotherms and kinetic profiles. The adsorption isotherms were analyzed using Langmuir, Freundlich, and Sips models and the thermodynamic parameters were calculated. Kinetic results were correlated with different models to complement the analysis of adsorption mechanism. The highest adsorption capacities were 425.05 mg·g⁻¹ for RB4 on MIL-100(Fe), 287.18 and 63.92 mg·g⁻¹ for AB25 on MIL-101(Fe) and HKUST-1, respectively. The most effective adsorbent for BB3 adsorption was MIL-100(Fe), with an adsorption capacity of 132.74 mg·g⁻¹. All equilibrium data were correlated satisfactorily with the Sips model (R² > 0.90). The adsorption kinetics of AB25 and RB4 were fitted with the pseudo-second order model, while the BB3 adsorption kinetic was better described using the pseudo-first order model. The modeling and characterization results suggest that BB3 adsorption mainly involved electrostatic attraction (physisorption), whereas RB4 and AB25 involved chemical interactions between the sulfonate group and the metal ion. These results highlight the potential of MIL-101(Fe) and MIL-100(Fe) MOFs as adsorbents for the removal of dyes from textile effluents.