Fabrication of copper-terephthalate MOF/ferric xanthan gum nanocomposites for methylene blue adsorption.

The increasing contamination of water resources by toxic dyes, particularly methylene blue (MB), presents a critical environmental challenge. This study introduces a novel copper-terephthalate metal-organic framework (Cu-BDC) integrated with ferric xanthan gum (X) to form a Cu-BDC/X composite for effective dye adsorption. The composite was synthesized and characterized using physicochemical analysis to confirm structural integration and enhanced surface features. The material exhibited improved thermal stability, mesoporosity (pore radius, r¯ = 2.42 nm), specific surface area (13.9 m/g), and an anionic surface (pH at point of zero charge, pH = 3.075), with a particle size of 84 nm. Batch adsorption studies showed a maximum MB adsorption capacity of 164.33 mg/g under optimal conditions (2.0 g/L dosage, pH 7, 20 °C, 6 h). Kinetic modeling followed a pseudo-second order model, and equilibrium data fit both Langmuir and Freundlich isotherms, indicating mixed monolayer-multilayer adsorption behavior. Thermodynamic analysis showed spontaneous MB adsorption (ΔG°, -1.255 to -7.673 kJ/mol); Cu-BDC was exothermic (ΔH°, -22.91), while X and Cu-BDC/X were endothermic (8.12 and 25.53 kJ/mol). Notably, the Cu-BDC/X composite retained 94 % of its adsorption capacity after eight regeneration cycles, confirming excellent reusability and structural stability. This work highlights the potential of Cu-BDC/X as a sustainable and efficient adsorbent for wastewater treatment applications.