Permeability of zinc ions across ion-exchange membrane of ion-exchange electrodialyzer

To evaluate the permeability of heavy-metal ions that exist as cation and anion species in seawater, we proposed a model equation that expresses the permeation rates of monovalent and divalent anions across an anion-exchange membrane using the permeation rates of Br− and SO42−. The permeability of zinc across a cation- and an anion-exchange membrane was evaluated using the cation- and anion-model equations.We analyzed the permeation rates of zinc species (EZn2+EZn2+, EZnCl+EZnCl+, EZnCl3−EZnCl3−, EZnCl42−EZnCl42−). We found that EZnCl+EZnCl+ and EZn2+EZn2+ decreased with an increase in the concentration of chloride ions in the feed solution, indicating that EZn(C) decreases with an increase in the concentration of chloride ions. Moreover, EZnCl3−EZnCl3− and EZnCl42−EZnCl42− increase with the concentration of chloride ions in the feed solution, indicating that EZn(A) increases with the concentration of chloride ions.