Equilibrium, Kinetic and Thermodynamic Parameter Studies on Adsorption of Allura Red from Aqueous Solution by Granular Activated Carbon

Abstract

Allura Red (AR) is a water-soluble harmful tar-based food colorant (FD & C Red 40). Batch adsorption studies were performed for the removal of AR using bituminous coal based granular activated carbon as adsorbent by varying the operation parameters such as adsorbent dosage, initial concentration, contact time and temperature. Experimental equilibrium adsorption data were analyzed by Langmuir, Freundlich and Temkin isotherms. The equilibrium process was described well by Freundlich isotherm. From determined separation factor (RL), adsorption of AR by granular activated carbon could be employed as effective treatment method. Temkin parameter, B was determined to 1.62∼3.288 J/mol indicating a physical adsorption process. By estimation of adsorption rate experimental data, the value of intraparticle diffusion rate constant (km) increased with the increasing adsorption temperature. The adsorption process were found to confirm to the pseudo second order model with good correlation. Thermodynamic parameters like change of free energy, enthalpy, and entropy were also calculated to predict the nature adsorption in the temperature range of 298∼318 K. The negative Gibbs free energy change (ΔG =-2.16∼-6.55 kJ/mol) and the positive enthalpy change (ΔH = + 23.29 kJ/mol) indicated the spontaneous and endothermic nature of the adsorption process, respectively.