Effects of Cold Sintering on the Performance of Zeolite 13X as a Consolidated Adsorbent for Cesium

Cold sintering, a novel low-temperature consolidation technique, has shown promising results in various inorganic materials. However, the application of this technique to nanoporous materials for energy and environmental fields is not yet fully understood. This study investigates the effects of cold sintering on the relative densities, compressive strengths, chemical durabilities, crystal structures, specific surface areas, and adsorption capacities of zeolites. Cold sintering at 200 °C achieved 10 to 20% greater densification than conventional high temperature (700 °C) sintering; however, the original nanoporous structure of dry cold sintered zeolite was not maintained. Introducing liquid agents during the cold sintering process resulted in reduced degradation of the SSA and increased densification. Using NaOH as the liquid agent increased the solubility of elements in zeolite, which promoted chemical mobility and achieved the highest relative density (96.7 ± 2.8%). However, soluble layers between the particles led to fragmentation, making it unsuitable for aqueous applications. Using H₂O as the liquid agent resulted in a relative density of 90.4 ± 4.1% while maintaining the nanoporous properties and structural integrity of zeolite under water. The cesium adsorption capacity (19.0 ± 0.1 mg·g^-1) was similar to that of conventional zeolite ion exchangers, indicating that cold sintering with H₂O was an efficient, economical, and safer alternative to conventional high-temperature consolidation method. Our findings suggest that this cold sintering can be applied to other nanoporous materials, such as metal-organic frameworks and covalent organic frameworks, in separation, catalysis, and adsorption applications.