Enhanced adsorption of dyes on microwave-assisted synthesized magnetic zeolite-hydroxyapatite nanocomposite

In the present study, magnetic zeolite/hydroxyapatite (MZeo-HAP) nanocomposite was successfully synthesized using microwave-assisted method for the removal of Reactive Orange 5 (RO5), Reactive orange 16 (RO16), and Congo red (CR) anionic dyes from aqueous solutions through batch adsorption. Thorough characterization of the synthesized adsorbent was done by SEM, EDAX, XRD, TEM, FTIR, VSM, and BET. The MZeo-HAP was found to have a high surface area of 103.56 m2/g, which provided a large number of active sites for dye molecules. The effect of initial pH, contact time, adsorbent dosage, and initial dye concentration was investigated. The maximum dye removal was attained at pH 2 and the equilibrium contact time of 30 min. At dye concentration of 80 ppm, the highest adsorption capacity of RO5, RO16, and CR was 92.45, 88.31, and 104.05 mg/g, respectively. Thermodynamic parameters such as ΔG°,ΔS°andΔH° were estimated for the adsorption study and suggested that the adsorption was endothermic and maximum dye adsorption occurred at 40 °C. Adsorption equilibrium data obeys Freundlich model with correlation coefficient ranging from 0.9632 to 0.9903, indicating the chemisorption nature of adsorption. Similarly, pseudo second order model is the most appropriate model to describe adsorption kinetic.