The Mordenite membrane was synthesized onto commercial ceramic tubular support (a-alumina), and surface characterizations were carried out on Mordenite powder. The surface charge density remains stable when Mordenite was in contact with monovalent or divalent salts. Pore diameter was estimated in the range of 8-10 nm, Filtrations tests were performed using the Mordenite membrane with single monovalent halide salt solutions. No rejection was observed. Then, the Mordenite membrane was treated with a divalent anionic salt (Na2CO3). Weak rejections were observed according to the order of hydration energy (NaF > NaCl > NaBr > NaI). After an acid cleaning, the membrane recovered its initial properties. A new estimation of average pore radius proved that steric effects were not responsible for rejection themselves. A new filtration test of mixed monovalent salt solution was carried out. The fluoride ion was retained by a majority. A preferential transfer was observed for chloride, bromide, and iodide ions.