Adsorption of Congo Red a Basic Dye by Zn/Fe-CO3

Abstract

Adsorption of Congo Red dye from aqueous solution by Zn/Fe-CO₃ layered double hydroxide was accomplished under the optimized conditions of variable temperature, initial concentration and contact time. The layered double hydroxide was synthesized by co-precipitation method and characterized by X-ray diffraction (XRD), Fourier Transform Infrared spectroscopic (FTIR) and Energy-Dispersive X-ray Spectroscopic (EDX) to give it a signature print before and after adsorption studies. The kinetics of interactions were tested with Zero-order kinetic model, first-order kinetic model, second-order kinetic model and pseudo-second-order kinetic model respectively with the best fits been first-order kinetic model (R² = 0.9999)  and pseudo-second-order kinetic model (R² = 0.9993). The applicability of Langmuir, Freundlich and Temkin adsorption isotherm equations for the present system was also tested. The experimental data are fitted Langmuir, Freundlich and Temkin isotherm equations with correlation coefficient values of 0.9925, 0.9936 and 1 respectively. The kinetics of interactions were tested with Zero-order kinetic model, first-order kinetic model, second-order kinetic model and pseudo-second-order kinetic model respectively with the best fits been first-order kinetic model (R² = 0.9999)  and pseudo-second-order kinetic model (R² = 0.9993). Thermodynamic parameters like ΔG^o, ΔH^o, ΔS^o and ΔH_x were calculated. The results shows an endothermic, favourable and feasible adsorption system.