Modification of Natural Mordenite by Alkali Hydrothermal Treatments

Natural mordenite from Shimane Prefecture, southwest Japan, was treated at temperatures of 50-200°C and autogeneous pressure for 7 days, changing the NaOH concentration from 1 to 10M (M=mol dm-3) . The several types of zeolites, such as phillipsite, hydroxysodalite and analcime were obtained by the transformation from mordemte after alkali hydrothermal treatments. The formation of hydroxycancrinite was observed for the first time under the hydrothermal treatment of the natural mordenite and the conditions were determined for the transformation. These results indicated that the phases of the zeolite formation from mordenite were clearly dependent on both NaOH concentration and treated temperature. The present results may provide a technology for the improvements of low-grade natural zeolites into high-grade ion exchangers.