Removal of Pyronin B from aqueous solutions using raw and modified vermiculite

Abstract

The raw vermiculite was chemically modified with phosphoric acid and applied as a potential adsorbent for the removal of Pyronin B, a xanthene derivative dye, from aqueous solution. The raw VMT and phosphoric acid-modified vermiculite (P-VMT) samples were examined by XRD, FTIR, TGA, and SEM. The initial raw vermiculite (VMT) has impurities such as calcite, which is completely eliminated after modification. The results showed that the adsorption capacity of P-VMT was found to be higher than VMT. The adsorption equilibrium data were tested by the Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models. The results showed that the adsorption of Pyronin B by vermiculite fitted the Freundlich isotherm well, while that exhibited by P-VMT fitted the Langmuir isotherm well. The adsorption kinetic of Pyronin B onto VMT and P-VMT was described by the pseudo-second-order model. The intra-particle diffusion model indicated that the adsorption may also be followed by multiple adsorption processes. Moreover, the thermodynamic parameters were also calculated. It was determined that the adsorption of Pyronin B on VMT and P-VMT was an endothermic and spontaneous process. The desorption of the dye on VMT and P-VMT using ethanol and methanol was also investigated primarily. © 2014 Springer Science+Business Media Dordrecht.