Development of Ammonia Selectively Permeable Zeolite Membrane for Sensor in Sewer System

Ammonia (NH₃) and hydrogen sulfide (H₂S) are hazardous and odorous gases. A special device that is not affected by other gases is necessary so that it can detect such gases. Zeolite membranes can separate the desired component selectively by molecular sieving and selective adsorption. LTA-, MFI-, and FAU-type zeolite membranes were prepared in this study, and the permeation and separation performances were determined for the ternary mixture of NH₃, H₂S, and N₂ to develop an NH₃ selectively permeable membrane. Although the separation factors of NH₃ were high enough for the LTA-type zeolite membrane, the NH₃ permeance was the lowest among the three membranes. In contrast, the FAU-type zeolite membrane with Si/Al = 1.35 showed a high enough NH₃ permeance and a NH₃/N₂ separation factor. The membrane modification and varying the membrane composition were carried out to reduce the H₂S permeance. As a result, the H₂S permeance could be decreased by modification with silane coupling agents, and a separation factor of NH₃ toward H₂S of over 3000 was achieved.