REMOVAL OF CO2 AND SEQUESTRATION OF CARBONATE USING A RECYCLABLE URANYL TRIPEROXIDE SYSTEM

Uranyl peroxides already have uses in the nuclear fuel cycle such as uranium precipitation after mine leeching but applications of this class of materials is not well understood. Uranyl triperoxide, [UO2(O2)3]4-, was synthesized as the lithium, sodium, and potassium salts. These solids were found to significantly increase the rate of conversion of CO₂ into carbonate in surface adsorbed water. The uranyl triperoxide salts were studied under a continuous flow of nitrogen with 300 ppm CO2 at a relative humidity ranging from 40-85%. The lithium salt was found to adsorb water to the surface and likely alters to a carbonate phase through a solid-state transformation. The sodium and potassium salts adsorb water until they dissolve and convert to a series of carbonate species before recrystallizing. The sodium salt produced crystals of tri-sodium hydrogen (bis)carbonate dihydrate separating the carbonate and uranium phases. Higher relative humidity led to more complex speciation and structures. Samples were analyzed using single crystal and powder X-ray diffraction, Raman and IR spectroscopy, and electrospray ionization mass spectrometry.