engleski

Influence of the flow rate on lead and zinc removal from a binary solution on the fixed bed of natural zeolite

The removal of heavy metals from wastewaters to concentrations below the permissible limits requires the application of advanced technological treatment processes such as ion exchange and adsorption. Due to their high costs, recent investigations have been directed to finding solutions for making them suitable for wide application. Excellent physical and chemical properties of natural zeolites, high ion exchange capacity, wide distribution of deposits in nature, simple and easy exploitation makes them sustainable ion exchangers and adsorbents. The column performance of ion exchange allows successive repetitions of several service and regeneration cycles and thus treatment of a large quantity of wastewater, which makes natural zeolites even more attractive. The removal of heavy metal ions from multicomponent systems is very complex due to different ion exchange affinity and different selectivity of zeolite. The aim of this study was to examine the influence of the flow rate on Pb and Zn removal from a binary solution on natural zeolite. Laboratory column tests were performed at room temperature in a 50 cm long glass column with an internal diameter of 1.2 cm, filled with zeolite sample up to 8 cm. The equimolar feed solution co(Pb2+ + Zn2+) ≈ 1 mmol / l, flowed from the top to the bottom of the column at the constant flow rates of Q = 1, 2 and 3 ml/min, using a vacuum pump. After each service cycle, the regeneration of exhausted zeolite was performed with NaNO3, c = 176.5 mmol/l, at the flow rate of 1 ml/min. In all experiments the effluent was periodically collected at the bottom of the column and analyzed for Pb and Zn concentrations. With increased flow rate, breakthrough and exhaustion points appear earlier as expected. Capacities in breakthrough and exhaustion, qB and qE, are reduced as well as the removal efficiency, due to shorter contact time between the feeding solution and the zeolite layer. The results have shown greater selectivity of clinoptilolite toward lead ions, and thus the displacement of Zn bound on zeolite with Pb from the feeding solution, but displacement effect is reduced with the increase in the flow rate. That is confirmed by regeneration curves.

column process; binary solution; lead; zinc; displacement effect; flow rate

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