Equilibrium and kinetic adsorption study of aqueous basic dye solutions using waste foundry sand

Abstract

The aim of this study is to evaluate adsorption kinetics, isotherms and thermodynamic parameters of crystal violet (CV) and methylene blue (MB) dyes from aqueous solution using waste foundry sand. Adsorption studies were carried out at different initial dye concentrations (12.5 - 400 mg l(-1)), contact time (5 - 240 min), pH (3.0 - 9.0), sorbent doses (0.125 - 2 g l(-1)) and adsorption temperature (20 degrees C - 70 degrees C). The equilibrium adsorption data were analysed by Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (DRK) adsorption isotherm models. Of the four adsorption isotherms, the R-2 value of Langmuir isotherm model for MB and CV were 0.969 and 0.926, respectively. Experimental data were analysed using the pseudo-first order, the pseudo-second order, intraparticle diffusion and Elovich models. The characteristic parameters for each model have been determined. In addition, the equilibrium thermodynamic parameters, including changes in Gibbs free energy, entropy and enthalpy are determined for the CV and MB on waste foundry sand.