Chemical Engineering Journal, Vol.155, No.3, 728-735, 2009
Effect of pH on cadmium (II) removal from aqueous solution using titanosilicate ETS-4
Cadmium is one of the most toxic contaminants of superficial waters, whose effects are particularly harmful to human health. In 20 years the European Union will impose total elimination of cadmium from industrial discharges. Such facts induce researchers to develop fine separation processes for cadmium removal, especially at the tertiary treatment level. In this work, we studied the applicability of the microporous titanosilicate ETS-4 (Engelhard Titanium Silicates No. 4) to uptake Cd2+ from aqueous solution, in order to evaluate its potential as ion exchanger material. The effect of pH was investigated by performing batch stirred tank experiments. The results obtained shown that Cd2+ removal increases up till pH 6, which is a very important conclusion since this value is commonly found in effluents and other wastewaters. The equilibrium data at pH 6 were accurately represented by the Langmuir-Freundlich isotherm under the experimental conditions studied (average absolute deviation, AAD=1.67%). The amount of Cd2+ removed by ETS-4 at pH 6 clearly surmount results found in literature for the same titanosilicate at pH 4 and for different materials. The kinetic of Cd2+ uptake by ETS-4 was analyzed using a Nernst-Planck based model. The absolute average deviation found point out the reasonable data representation accomplished by Nernst-Planck: AAD=17.2%. (C) 2009 Elsevier B. V. All rights reserved.