Fixed-bed removal of Hg2+ from contaminated water by microporous titanosilicate ETS-4: Experimental and theoretical breakthrough curves

The present study reports the assembly and operation of a fixed bed using the microporous titanosilicate ETS-4 as sorbent. Sorption-desorption cycles were carried out on an ETS-4 fixed-bed, for the removal of Hg2+ from contaminated water. The sorption capacity of the ETS-4 in the column in two consecutive cycles remained constant (33.6 and 33.3 mg g(-1), respectively); however due to certain difficulties encountered during ETS-4 packaging and operation mode, breakthrough curves corresponding to these cycles showed dissimilar patterns. A concentration gradient of an EDTA-Na-2 solution (0.05-0.25 M) was efficient for bed regeneration, achieving an elution efficiency of 98%. The elution curve had an asymmetrical shape, the concentration peak was attained in less than 5 min, and the concentration factor was 920. Four kinetic models, namely Thomas, Bohart-Adams, Clark and Yoon-Nelson, were applied to predict the breakthrough curves and to estimate the characteristic parameters of the column, which are the basis for the process design at a real scale. The operation of an ETS-4 fixed-bed for the treatment of Hg2+. contaminated waters was shown to be feasible, despite some limitations mainly related with its loose packing. (C) 2011 Elsevier Inc. All rights reserved.