ADSORPTION OF RY 125 DYE FROM AQUEOUS SOLUTION ON A SILVER DOPED TiO2 MODIFIED CLINOPTILOLITE

The aim of the present work was to study the dark adsorption of Reactive Yellow 125 (RY 125) using a silver doped TiO2 modified clinoptilolite (Z-TiO2-Ag) envisaging its further application in heterogeneous photocatalytic oxidation. Several kinetic models, i.e., Lagergren, Ho-McKay, Dumwald-Wagner intraparticle models were tested to elucidate some adsorption mechanistic aspects. The pseudo-second order kinetic model proposed by Ho and McKay was the most suitable in describing the adsorption kinetic of RY 125 dye onto Z-TiO2-Ag. The solid-liquid equilibrium experimental data were correlated with four mathematical models, i.e., Langmuir, Freundlich, Dubinin-Radushkevich and Harkin-Jura. The Freundlich isotherm approximated the best the experimental data. A physical nature of adsorption process was found based on the value of the free energy of adsorption, E-DR = 0.796 kJ mol(-1), calculated from Dubinin-Radushkevich, and on the values of Harkin-Jura model parameters, as well as. This aspect was also supported by Zeta potential measurements for Z-TiO2-Ag suspension in RY 125 dye solution.