Adsorption modelling of textile dyes by sepiolite

Adsorption of Astrazon Red (Basic Red 46) and Sirius Blue (Direct Blue 85) in aqueous solution by sepiolite was studied using Response Surface Methodology. A Box–Behnken design was performed to evaluate the effect of initial dye concentration, initial solution pH and temperature on the amount of dye adsorbed at equilibrium. Quadratic models were used to fit the experimental data obtained for both dyes and their adequacy was statistically validated. Linear and quadratic effects of initial dye concentration and linear effect of initial pH were shown to be very significant for Astrazon Red adsorption. Initial pH played the most important effect on the adsorbed amount of Sirius Blue dye but the linear effect of initial dye concentration, its interaction effect with initial pH and the quadratic effect of pH were shown to be also very significant.