Adsorptive removal of cationic (BY2) dye from aqueous solutions onto Turkish clay: Isotherm, kinetic, and thermodynamic analysis

Abstract

The removal of Basic Yellow 2 (BY2), a cationic dye, from aqueous solution by using montmorillonite as adsorbent was studied in batch experiments. The effect of pH, agitation speed, adsorbent dosage, initial dye concentration ionic strength, and temperature on the removal of BY2 was also investigated. Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherms were applied to fit the adsorption data of BY2 dye. Equilibrium data were well described by the typical Langmuir adsorption isotherm. The maximum monolayer adsorption capacity was calculated as 434.196 mg g(-1) from the Langmuir isotherm model. The adsorption data was fitted to both the pseudo-first-order, pseudo-second-order, Elovich, and intraparticle kinetic models, and the calculated values of the amount adsorbed at equilibrium (q(e)) by pseudo-second-order equations were found to be in good agreement with the experimental values. The thermodynamic factors were also evaluated. The entropy change (Delta S*) was negative, suggesting that the adsorption process decreases in entropy and enthalpy change (Delta H*) was positive which indicates endothermic nature. The positive Delta G* value confirms the un-spontaneity of the process. In addition, a semiempirical model was calculated from kinetic data.