Removal of Hg2+ ions from aqueous solution by ETS-4 microporous titanosilicate—Kinetic and equilibrium studies

Batch stirred tank experiments were carried out to study the application of ETS-4 microporous titanosilicate for Hg2+ ions removal from aqueous solution. The effect of operational conditions was assessed and it was proved that Hg2+ uptake (%) increases with increasing contact time, increasing ETS-4 mass and decreasing initial Hg2+ concentration. It was confirmed that stirring rate does not affect the Hg2+ removal by ETS-4 as long as it is high enough to break the diffusion resistance.Two simplified models, the pseudo first-order and the pseudo second-order equations, were used to describe the kinetics of the sorption process and better fittings were obtained by the last one. The Bt versus t plots indicated that film diffusion is the rate-limiting step of the removal of Hg2+ by ETS-4. Langmuir, Freundlich and Dubinin–Radushkevich isotherm equations fitted quite well the equilibrium data and the Langmuir maximum capacity of ETS-4 was found to be 246 mg g−1 at 21 °C.