Influence of the operating conditions on the elimination of zinc ions by nanofiltration

In the present work, we were interested to study the influence of applied pressure, solution concentration and recirculation flow on the zinc retention by nanofiltration. The results have shown that the Zn2+ retention increases with the pressure and reaches a maximum of 90% which varies slightly with the concentration. These observed retention values have been found higher in comparison of other metals retention such as copper or cadmium (40%) as it was be noted in literature. We have attributed this difference in behavior to the electrostatic repulsion charge of the ZnCl3- and ZnCl42- forming complexes present in solution which were calculated and found in dominant proportion. This explication was verified and confirmed by studying the Zn2+ retention when using nitrates co-ions in place of chlorides ions. Otherwise, the recirculation flow was studied and the results have shown that the Zn2+ retention rises when the recirculation flow increases. We have attributed this result to the polarization concentration phenomenon which can be reduced when recirculation flow increases.