Development of a First-Order Kinetics Based Model, Equilibrium Studies, and Thermodynamics for the Adsorption of Methyl Orange onto a Lignocellulosic Anion Exchanger

Abstract

The present article describes the adsorption behavior of methyl orange (MO) on polyacrylamide-grafted aminomethylated tamarind fruit shell anion exchanger. The optimum pH for MO removal was 3.0 and the equilibrium was attained within 2 h. The kinetic and isotherm data obtained at different pH and temperatures, could be fitted with the pseudo-first-order rate equation and the Sips isotherm model, respectively. The adsorption process was exothermic and spontaneous in nature. The decrease in isosteric heat of adsorption with increasing MO uploading on the adsorbent reflects the surface energetic heterogeneity of the adsorbent. The reusability of the adsorbent was demonstrated over 4 cycles using 0.2 M NaOH as the desorbing agent.