Impact of TiO_2–Cation Exchange Resin Composite on the Removal of Ethyl Violet

摘要

Adsorption capacity and photocatalytic performance of a mixture of 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 than with pure . 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 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 ( mg/L) at high resin dosage. A synergistic effect between adsorption and photocatalysis was seen upon combining the . This composite was more efficient for the removal of the dye than the use of alone.