Removal of methylene blue from aqueous solution by nano LaFeO 3 particles

Abstract

LaFeO₃ was prepared by the sol-gel method and characterized by XRD, SEM and FT-IR. The XRD results showed that LaFeO₃ is a perovskite oxide with an orthorhombic unit cell. The average crystalline size for nano crystalline LaFeO₃ is 32–65 nm. Methylene blue adsorption experiments were carried out under different conditions of contact time, solution pH from 2–12 and LaFeO₃ dose. The equilibrium data were fitted to Langmuir and Freundlich isotherms and the equilibrium adsorption was best described by the Langmuir isotherm model. Adsorption data were modeled using pseudo-first-order and pseudo-second order kinetics equations. The pseudo-second-order kinetic equation best described the adsorption kinetics. Thermodynamic activation parameters such as Gibbs free energy, enthalpy and entropy were calculated. The adsorption process of methylene blue on LaFeO₃ was found to be spontaneous and endothermic.