Reed James L A, James Andrew, Carey Thomas, Fitzgerald Neelam, Kellet Simon, Nearchou Antony, Farrelly Adele L, Fell Harrison A H, Allan Phoebe K, Hriljac Joseph A
School of Chemistry, University of Birmingham Edgbaston Birmingham B15 2TT UK
Diamond Light Source Ltd, Harwell Science and Innovation Campus Didcot Oxfordshire OX11 0DE UK.
Chem Sci. 2024 Aug 1;15(34):13699-13711. doi: 10.1039/d4sc02664k. eCollection 2024 Aug 28.
Controllable sorption selectivity in zeolites is crucial for their application in catalysis, gas separation and ion-exchange. Whilst existing approaches to achieving sorption selectivity with natural zeolites typically rely on screening for specific geological deposits, here we develop partial interzeolite transformation as a straightforward and highly tuneable method to achieve sorption selectivity forming dual-phase composites with simultaneous control of both phase-ratio and morphology. The dual-cation (strontium and caesium) exchange properties of a series of granular mordenite/zeolite P composites formed from a parent natural mordenite material are demonstrated in complex, industrially relevant multi-ion environments pertinent to nuclear waste management. The relative uptake of caesium and strontium is controlled the extent of transformation: composites exhibit significantly increased ion-exchange affinity for strontium compared to both the parent mordenite and physical mixtures of mordenite/zeolite P phases with similar phase ratios. The composite with a 40 : 60 mordenite : zeolite P ratio composite achieves higher uptake rates than the natural clinoptilolite material currently used to decontaminate nuclear waste streams at the Sellafield site, UK. X-ray image-guided diffraction experiments during caesium exchange demonstrate that the mordenite core retains rapid caesium uptake likely responsible for the unique ion-exchange chemistry achievable through the partial inter-zeolite transformation. These results offer a straightforward and controllable route to optimised zeolite functionality and a strategy to engineer composites from low-grade natural sources at low cost and with formulation advantages for industrial deployment.
沸石中可控的吸附选择性对于其在催化、气体分离和离子交换中的应用至关重要。虽然现有的利用天然沸石实现吸附选择性的方法通常依赖于筛选特定的地质矿床，但在此我们开发了部分沸石间转化法，这是一种直接且高度可调的方法，通过形成双相复合材料来实现吸附选择性，同时控制相比例和形态。由母体天然丝光沸石材料形成的一系列粒状丝光沸石/沸石P复合材料的双阳离子（锶和铯）交换特性，在与核废料管理相关的复杂、工业相关的多离子环境中得到了证明。铯和锶的相对吸收量由转化程度控制：与母体丝光沸石以及具有相似相比例的丝光沸石/沸石P相的物理混合物相比，复合材料对锶表现出显著增强的离子交换亲和力。丝光沸石与沸石P比例为40 : 60的复合材料实现了比目前英国塞拉菲尔德核电站用于净化核废物流的天然斜发沸石材料更高的吸收速率。铯交换过程中的X射线图像引导衍射实验表明，丝光沸石核心保留了快速的铯吸收，这可能是通过部分沸石间转化实现独特离子交换化学的原因。这些结果提供了一条优化沸石功能的直接且可控的途径，以及一种以低成本从低品位天然资源制备复合材料的策略，且该复合材料具有利于工业应用的配方优势。
