The removal of Basic Blue 41 textile dye from aqueous solution by adsorption onto natural zeolitic tuff: Kinetics and thermodynamics

Abstract

Abstract The adsorption of Basic Blue 41 textile dye from aqueous solutions on a zeolite tuff (Nereju-Romania) was studied in batch mode. SEM, EDX, FT-IR, N2 gas adsorption–desorption techniques of characterization of tuff samples were applied. The effects of the initial pH solution, dye concentration, contact time between the adsorbent and the dye, the temperature and the particle size of the tuff correlated with their composition were investigated. The kinetic studies show that the adsorption follows the pseudo-second order kinetics. The experimental data were analyzed according to the Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherms. The adsorption equilibrium was best described by the Langmuir isotherm. There was a higher adsorption capacity of particles with a 0.085 mm average diameter containing larger amounts of zeolites (predominant analcite) and a specific surface area than of those with a larger average diameter of 0.9 mm. An increase in the temperature from 8 °C to 50 °C favorably influences the adsorption equilibrium. The maximum adsorption capacity for the investigated basic textile dye (∼40% pure dye) was 192.31 mg g−1 at 50 °C (at pH 5) for the average diameter particles tuff of 0.085 mm. The positive enthalpy change for the adsorption process confirms the endothermic nature of adsorption and a free energy change confirms the spontaneity of the process.