The study of radium and polonium sorption by a thin-layer MnO 2 -CTA sorbent

The work focuses on sorption of radium-223 and polonium-210 by a thin-layer MnO2-CTA sorbent. The maximal sorption of Ra (≈ 80%) and Po (≈ 12%) was achieved after 1 day of sorption. For Ra, decrease of quality of alpha spectrum was observed during sorption that can be explained by its diffusion into MnO2 and support layers. The average thickness of the sorption layer was determined to be 456 nm, whereas the energy loss of 5 MeV α-particles in MnO2 is approximately 270 keV μm−1. Scanning electronic microscopy and optical microphotographs confirmed flat morphology of the sorbent’s surface and no morphology changes as a result of sorption. In contrast to radium, the values of full width at half maximum (FWHM) of the 210Po alpha peak just slightly increased from ≈ 40 to ≈ 80 keV after 2 weeks of sorption that can be explained by larger ionic radius of polonium and another sorption mechanism, which is probably a partial replacement of manganese by polonium in the manganese dioxide crystal lattice. The observed phenomenon of increasing FWHM of alpha peaks from flat sorbents was suggested as an instrument for study the diffusion of alpha emitters in flat sorption-active layers.