A Study on the Adsorption Equilibrium and Kinetics of Methylene Blue using Waste Eggshells

Abstract

In this work, waste egg shells were used as a low-cost adsorbent for the removal of methylene blue from an aqueous solution in a batch adsorption procedure. The effects of temperature, pH, initial dye concentration and contact time on the adsorption performance were then investigated. Experimental results indicated that the adsorption was strongly dependent on pH of the solution and the adsorption capacity decreased with an increase in temperature. The Freundlich isotherm model showed the best fit to the equilibrium adsorption data at all temperatures. The kinetic data were found to follow the pseudo second-order kinetic model. The rate constant decreased with the increase in temperature indicating the exothermic nature of adsorption. Gibbs free energy (ΔG0) was spontaneous for all interactions, and the adsorption process exhibited exothermic enthalpy values. Results suggest that the waste egg shell is a potential adsorbent for removal of methylene blue from an aqueous solution.