Ion exchange properties of five different Japanese natural zeolites in seawater were examined. Sodium ions could be reduced by all zeolites, although anions, Cl(-) and SO(4)(2-), in seawater showed barely changes. Natural zeolite desalination treatment mainly depends on the ion exchange between Na(+), K(+) and Mg(2+) in seawater and Ca(2+) in natural zeolite. This study found that mordenite ...