Isotherm, kinetic and thermodynamic studies of methylene blue adsorption using Leucaena leucocephala

Abstract

In recent years, great focused has been placed on the development of low-cost adsorbents to be used for applications regarding treatment of wastewater. In this study, Leucaena leucocephala peel (LLP) was used for adsorption of methylene blue from aqueous solutions. The experiments were conducted at seven concentrations (15, 30, 45, 60, 75, 90, 105 mg L-1) and three temperatures (298, 308, 318 K). The obtained data were applied to adsorption isotherm, kinetic and thermodynamic calculations. The results showed that Freundlich isotherm was more appropriate compared to Langmuir and Temkin isotherms. The kinetic results indicated that the process fitted pseudo second order model with higher R2 values compared to pseudo first order and intra-particle diffusion models. Gibbs free energy, enthalpy and entropy values were calculated for 298 K as 2.776 kJ mol-1, 6.262 kJ mol-1 and 11.699 J mol-1, respectively.