Removal of reactive dye Brilliant Red HE-3B from aqueous solutions by industrial lignin: Equilibrium and kinetics modeling

The lignin, one of the main by-products of the pulp industry, can be used to remove dyes from textile wastewaters. The potential of the lignin for Brilliant Red HE-3B reactive dye removal from aqueous solutions at pH = 1.5 was examined by the batch technique as a function of dye concentration, solution temperature and contact time. The Freundlich, Langmuir, Dubinin-Radushkevich and Tempkin adsorption isotherms were used to describe the data of sorption equilibrium and to determine its corresponding isotherm constants. The thermodynamic parameters ΔG, ΔH and ΔS were also determined; the obtained values show that the sorption of reactive dye on lignin is a spontaneous, endothermic and entropy-driven process. The kinetic of reactive dye sorption was analyzed using the pseudo-first order and pseudo-second order kinetic models; the kinetic data fitted well to the pseudo-second order kinetics, indicating the chemisorption of reactive dye onto lignin. The reactive dye sorption onto lignin was mainly conducted through the ion exchange mechanism, confirmed by FTIR spectroscopy. The results evidenced that the lignin has a viable or real potential to remove the Brilliant Red HE-3B reactive dye from aqueous effluents.