Mechanistic study on adsorption of methylene blue on tea seed powder

In order to investigate the dye adsorption properties of tea seed powder,methylene blue was chose as the sorbate.The data obtained at different temperatures(298,303,308,313,318 K) were fitted with Langmuir,Freundlich and Dubinin-Radushkevish models to describe the equilibrium isotherms.The kinetics rates were modeled using pseudo-first-order and pseudo-second-order kinetic equations.The Gibbs free energy(ΔGθ) 、enthalpy change(ΔHθ) and entropy change(ΔSθ) were calculated.The results revealed that the equilibrium adsorption amount decreased with the increase of temperature.The adsorption could be well depicted by the Langmuir adsorption isotherm.The Gibbs free energy(ΔGθ) 、enthalpy change(ΔHθ) and entropy change(ΔSθ) were negative,indicating that the adsorption was a spontaneous,exothermic and decreasing entropy process.The adsorption kinetics followed pseudo-second-order kinetic equation.