The removal of iron and cobalt from aqueous solutions by ion exchange with Na-Y zeolite: Batch, semi-batch and continuous operation

The removal of single component and binary mixtures of divalent cobalt and iron from water by ion exchange with synthetic Y zeolite has been studied in batch, semi-batch and continuous modes of operation; the initial metal solution concentration did not exceed 2 mmol dm(-3). Binary Co/Na and Fe/Na ion exchange equilibrium isotherms (294K) are presented wherein exchange site heterogeneity is evident in the case of the iron treatment. Under conditions of stoichiometric ion exchange, removal efficiencies for both cobalt and iron decrease with increasing metal concentration (0.2-2 mmol dm(-3)) and the values were similar for both metals. Removal of cobalt under transient conditions was found to be temperature dependent. In the fixed bed operation, break-through behavior was sensitive to changes in both flow rate and inlet concentration. The break-through profiles for both metals under competitive and non-competitive conditions are presented; iron removal is lower in the presence of cobalt and vice versa. An in situ regeneration of the fully loaded zeolite by back exchange with sodium is considered and the exchange capacity of the regenerated zeolite is reported. The feasibility of employing cycles of heavy metal uptake/zeolite regeneration is addressed. (C) 2002 Society of Chemical Industry.