Application of Langmuir and Freundlich isotherm, pseudo-first-order, and pseudo-second-order kinetic studies for the adsorption of sunset yellow dye onto Cadmium-based imidazole zeolite nanostructure

Zeolitic-imidazole framework (Cd-ZIF) was synthesised and characterised. Cd-ZIF was accomplished by Fourier transfer infrared (FTIR), field emission scanning electron microscope (FESEM), X-ray powder diffraction (XRD), energy-dispersive spectrum (EDX), and Brunauer–Emmett–Teller (BET). The synthesised zeolite was used in the (SY) adsorption. The impact of different variables on batch method as a function of solution pH, concentration of SY, dose of Cd-ZIF, contact time and temperature were analysed and optimal conditions were determined. The point of the zeolite zero charge (pHPZC) was obtained at 7.0. The optimal conditions were obtained at pH = 5, the initial concentration C0 = 160 mg L−1, 30 mg of Cd-ZIF, t = 60 min, and 40°C. Langmuir and Freundlich models were employed by equilibrium data from SY adsorption process. The results showed that Freundlich model was fitted. Therefore, the adsorbent had a surface heterogeneity. The adsorption capacity increased with increasing the temperature up to 40°C, which showed the endothermic adsorption. Further temperature (at 45°C), the adsorption decreased because of electrostatic attraction between free and adsorbed SY molecules. The kinetics of adsorption indicated that SY adsorption followed a pseudo-second-order model and chemisorption.