Removal of Congo Red dye from Wastewater Using Orange Peel as an Adsorbent

Abstract

Present study deals with the utilization of orange peel as an adsorbent for the removal of Congo Red (CR) dye from aqueous solution. The proximate analysis revealed that, the adsorbent has porous structure with volatile matter of about 79.14% and fixed carbon 13.08%. The adsorbent has neutral charge at the pH of 6.37. From the batch adsorption study, the optimum adsorbent dose found 40 g/L, the optimum pH was found to be 6.43 and equilibrium time was found 3 h. The increase in adsorption with temperature shows the endothermic nature of adsorption process. The maximum percent removal of CR was found to be 94.24 at the initial concentration of 100 mg/L at 30 °C. The isotherm analysis shows that the Langmuir adsorption isotherm is best-fitted for Congo Red adsorption on orange peel followed by Freundlich and Temkin isotherm equations. The values of the constants KL and qm are 0.053 L/mg and 11.919 mg/g respectively. Thermodynamic study shows the endothermic nature nature of the adsorption process. The heat of adsorption (∆H) was found to be 21.475 KJ/mol and change in entropy (∆S) was found 0.149 KJ/mol K. Gibbs free energy (∆G) was found -24.633, -26.548 and -28.464 kJ/mol. The adsorption process is found to be feasible and spontaneous. The orange peel can be utilized as an adsorbent for the removal of other pollutants.