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

Abstract

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-Na2 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.