The development of zeolite particles for positron imaging applications

The development of particles with diameters between 5 – 50 μm are of interest for application as tracers in the positron imaging technique, positron emission particle tracking (PEPT). Building on previous studies, the influence of ethanol and the intrapore cation content on the size and morphology of mordenite microparticles has been investigated. A method for producing monodisperse microspheres of the zeolite, gmelinite, has also been developed. Moreover, previously reported crystal growth conditions have been tailored to produce zeolite A and X crystals in the desired size range. As fluorine-18 is a widely employed β+-emitting isotope, reactivity between aqueous fluoride and zeolite Y, with different intrapore cations, has been studied. Fluorine environments in the zeolites, and the likely mechanism for the reaction, have been determined by MAS NMR spectroscopy. The essential role of Brønsted acids in mediating the reaction, and the promoting effect of divalent metal cations, have also been established. Finally, the influence of applicable post-synthetic treatments (viz. divalent metal ion exchange, dealumination and iron(III) surface sorption) on fluoride uptake by large crystals, or particles, of mordenite, gmelinite and zeolites A and X has been investigated. Ultimately, the most suitable post synthetic treatment for enhancing fluoride loadings on large particles of each zeolite has been determined.