Optimized Congo Red Dye Adsorption Using ZnCuCr-Based MOF for Sustainable Wastewater Treatment

This study presents the synthesis of a novel trimetallic ZnCuCr-TpIm metal-organic framework (MOF) via a solvothermal method, yielding cubic crystals of 300-500 nm. The integration of Zn, Cu, and Cr metal centers enhances the MOF's adsorption efficiency and structural stability, distinguishing it from conventional MOFs. The material achieves a high Congo red dye removal efficiency (96.5%) under optimal conditions: 40 mg adsorbent dosage, 55 °C, pH 6-7, and a 60 min contact time. Kinetic analysis reveals that the adsorption follows a pseudo-second-order model (<i>R</i>² > 0.999), indicating chemisorption as the rate-limiting step, while equilibrium data align with the Langmuir isotherm model (<i>R</i>² = 0.998), confirming a maximum adsorption capacity of 325 mg/g. FTIR and XRD analyses confirm strong interactions between the dye molecules and the MOF framework while preserving its crystalline structure. The ZnCuCr-TpIm MOF demonstrated exceptional stability, retaining 95% of its surface area after 72 h and maintaining over 90% adsorption efficiency after five reuse cycles, with minimal metal ion leaching (<1.2 ppm). The material also exhibited high resilience under varying pH, salinity, and simulated wastewater conditions, underscoring its potential for long-term and sustainable dye removal applications. These findings highlight the synergistic advantages of the trimetallic MOF, making it a promising candidate for efficient and stable wastewater treatment.