Fixed-bed ion-exchange process performance of Pb2+ removal from a simulated ceramic wastewater by Neapolitan yellow tuff.

A phillipsite-rich Neapolitan yellow tuff bed, pre-exchanged in Na + form, was used to remove Pb 2+ from a simulated wastewater of a ceramic manufacture through cation-exchange in dynamic conditions. The composition of the simulated wastewater was the following: Pb 2+, 22 mg/l; Na +, 1-10 -3 M; K +, 1-10 -4 M; Ca 2+, 1.5-10 -3 M; Mg 2+, 1-10 -3 M. A complete Pb 2+ breakthrough curve, obtained flowing the fixed bed with the simulated wastewater up to exhaustion, showed that the interfering cations present in the water did not result in a substantial reduction of Pb 2+ exchange capacity of the tuff, whmh means that Na-phillipsite shows a very strong selectivity for Pb 2+ in the reported experimental conditions. The optimisation of the regeneration step suggested to flow the bed with about 12 bed volumes of regenerant solution (1 M NaNO 3) which allowed to remove about 53% of Pb 2+ present in the bed. Such partial regeneration allowed to keep outlet Pb 2+ concentration below the limit allowed by law for about 1700 bed volumes of eluate, thus giving rise to a yield of the cation-exchange operations, i.e., the ratio between the volumes collected in the ion-exchange step and in regeneration step, respectively, of about 140.