Comparison of adsorption performances of vermiculite and clinoptilolite for the removal of pyronine Y dyestuff

In this study, the adsorption of pyronine Y (PyY) from aqueous solution on two adsorbents, vermiculite and clinoptilolite, was investigated with respect to contact time, initial dye concentration, pH, adsorbate concentration and solution temperature. Moreover, the dye removal performance of vermiculite was compared with that of clinoptilolite under the same experimental conditions. The adsorption of dye on adsorbents reached equilibrium in 15-25 min. The dye removal performance of vermiculite was comparable with that of clinoptilolite at high adsorbent concentrations above 5.0 g/L resulting in nearly 91 % dye removal with 10 mg/L initial dye concentration. The equilibrium experiments were analyzed by the Langmuir and Freundlich isotherms. As a result, the adsorption of PyY by clinoptilolite fitted the Freundlich isotherm well, while that by vermiculite fitted the Langmuir isotherm well. The first order kinetic, pseudo-second order kinetic and intra-particle diffusion models were used to investigate the kinetic data. The adsorption kinetics of PyY on adsorbents was described by the pseudo-second order kinetic equation. Moreover, the activation parameters were also calculated. It was found that the reaction for dye uptake by vermiculite and clinoptilolite is the presence of an energy barrier.