"Adsorptive removal of Congo Red dye from its aqueous solution by Ag-Cu-CeO nanocomposites: Adsorption kinetics, isotherms, and thermodynamics".

Eliminating synthetic dyes and organic contaminants from water is crucial for safeguarding human health and preserving the environment. In this study, we explored the effectiveness of Ag-Cu-CeO nanocomposites as adsorbents to remove Congo Red dye from water. Three compositions of Ag-Cu-CeO nanocomposites (10:20:70, 15:15:70, and 20:10:70) have been synthesized by the aqueous coprecipitation method. A comprehensive analysis was performed by different techniques including X-ray diffraction, Fourier transform infrared spectroscopy, BET surface area determination, Thermogravimetric analysis, Scanning electron microscopy, and TEM. The synthesized nanocomposites have a dimension of 5 ± 1 nm and a high surface area (51.832-78.361 mg). Among these, the nanocomposite with composition 15:15:70 showed the highest adsorption capacity of 4.71 mg/g adsorption (96.83 % removal) from the 0.8 × 10 M (55.6 mg/l) Congo Red solution at pH values of 2 at 20 °C with contact time of 3h. The adsorption data is best fitted in the Freundlich adsorption isotherm and pseudo-second-order kinetic model. The negative values of enthalpy variation (-27.57, -26.43, and -16.73 kJ/mol) demonstrated that the adsorption was spontaneous and exothermic. The cycling run showed a mere 12 % deactivation after five cycles of use thus indicating that Ag-Cu-CeO nanocomposites hold great potential as effective and eco-friendly adsorbents to remove Congo Red from water.