Impact of TiO2–Cation Exchange Resin Composite on the Removal of Ethyl Violet

Adsorption capacity and photocatalytic performance of a mixture of TiO 2 and a cation exchange resin were assessed by measuring the removal of the cationic dye ethyl violet (EV) from water. Highest adsorption of EV was achieved at pH 3 due to the increase in number of positive charges of the EV molecule. However, adsorption decreased at higher pH. The adsorption kinetics at pH 3 could be accurately described by means of a pseudo-second order kinetic model. Experimental adsorption equilibrium data at pH 3 fitted the Langmuir model more accurately than the Sips and Freundlich models. Photocatalysis experiments indicated that the EV elimination was higher with the mixture of cation exchange resin and TiO 2 than with pure TiO 2 . The description of experimental photocatalysis data by means of the Langmuir–Hinshelwood model was improved by introducing a power parameter in the original model. From the modified Langmuir–Hinshelwood model, it could be derived that the addition of increasing resin concentrations to a constant TiO 2 concentration enhanced the photocatalytic rate constant; however, UV light penetration in the solution was impeded beyond a given resin amount. Pseudo-first-order kinetics showed poor fit of experimental photocatalysis data except for low EV concentration ( < 35 mg/L) at high resin dosage. A synergistic effect between adsorption and photocatalysis was seen upon combining the TiO 2 . This composite was more efficient for the removal of the dye than the use of TiO 2 alone.