Kinetic and thermodynamic behavior study of Co-MOF@Ag efficient adsorption of Congo red in water

In this article, a novel adsorbent [Co(btyp)(ppda)]n (Co-MOF) (where ppda is p-phenylenediacetic acid and btyp is 3,5-bis(triazolyl)pyridine) was synthesized under hydrothermal conditions and a silver-doped composite (Co-MOF@Ag) was prepared. Characterization and performance tests show that the specific surface area of Co-MOF@Ag reaches 54.9 m2/g, which is 36.6 times that of Co-MOF. The maximum adsorption capacity (qm) reached 55 mg/g, which is 1.43 times that of Co-MOF. The enhanced adsorption capacity is attributed to the increased specific surface area and additional active sites. Adsorption kinetics and thermodynamic analysis indicated that the Co-MOF@Ag adsorption data has a good fit with the Langmuir model and quasi-second-order kinetic equation, and the adsorption process is monolayer chemical adsorption. At pH = 7, Co-MOF@Ag exhibites highly efficient adsorption capacity for the anionic dye Congo red (CR). Surface ζ-potential analysis confirms that electrostatic interactions are the primary driving force for adsorption. After five reuse cycles, Co-MOF@Ag maintains CR removal efficiency exceeding 90%, demonstrating excellent reusability. Notably, Co-MOF@Ag exhibits outstanding adsorption performance for CR in real Yanhe River water samples, achieving a removal rate 76.43%. In summary, Co-MOF@Ag, with its high specific surface area and superior adsorption capacity, exhibits promising prospects for dye wastewater treatment.