A novel cobalt-based MOF for simultaneous removal of Pb(ii) and Congo red from real textile wastewater: synergistic adsorption behavior and mechanistic insights.

Currently, the co-removal of heavy metals and anionic dyes from industrial wastewater is quite difficult due to the stability of both pollutants and their combined co-existence. Most previous studies have focused on single-pollutant adsorption, and few reports have investigated the performance of multifunctional MOFs with an effective removal efficiency towards co-existing inorganic and organic pollutants. Herein, a newly developed azo-ligand cobalt-based metal-organic framework (Co-MOF) is developed using a solvothermal method, and its adsorption performance in the simultaneous removal of Pb(ii) and Congo Red (CR) from aqueous solutions and real textile wastewater is examined. Characterization using FTIR, FESEM, EDX, XRD, TGA, and zeta-potential demonstrates the successful creation of a highly stable crystalline framework with abundant active sites that are accessible. Under the optimum conditions of a pH of 5-6, an adsorbent dosage of 0.03 g and room temperature (298 K), very fast adsorption rates were observed (50 min for Pb(ii) and 20 min for CR). The calculated maximum adsorption capacities based on the Langmuir model were 344.8 mg g-1 for Pb(ii) and 476.2 mg g-1 for CR, respectively, with removal of more than 93% for both pollutants. The kinetics and isotherms were fitted to the pseudo-second-order and Langmuir models, and the adsorption process was spontaneous and endothermic. In addition to high reuse capacity (six recovery cycles), the Co-MOF showed remarkable adsorption efficiency toward mixed pollutants in a real textile wastewater sample. The presented reusable Co-MOF is therefore a promising adsorbent for simultaneous remediation of mixed inorganic/organic pollutants.