Sorption of selected radionuclides on different MnO2 phases

After nuclear disasters, there is a need to monitor released radionuclides in aquatic systems. A novel in situ gamma spectrometer deployable on mobile and stationary platforms can detect individual radionuclides, provided concentrations are high enough. Owing to rapid dilution effects, efficient sorbents are needed for preconcentration of radionuclides. Here, we report results of particle-water distribution coefficients, K-D, on three novel MnO2 sorbents mounted in high-capacity cartridges using a set of artificial (Co-57, Ru-106, Sb-125, Ba-133, Cs-137) and natural (Be-7, Pb-210, Pa-233, Th-234) radionuclides in small batch experiments. Compared with conventionally impregnated MnO2 sorbents, novel nanostructured MnO2 sorbents displayed superior sorption for some artificial radionuclides, displaying up to one order of magnitude greater K-D values than traditionally impregnated MnO2. In particular, the log K-D value of Pb-210 was highest (4.48 +/- 0.23) compared with all values using the other MnO2 sorbents, whereas that of Pa-233 was among the lowest (3.24 +/- 0.16). These results promise some improvements for capturing not only artificially produced radionuclides, but also naturally produced Be-7 from seawater using nanostructured MnO2. We also show that colloidal forms of selected radionuclides are not captured by MnO2 phases. If they could be sorbed by another sorbent, K-D values could be considerably higher for Th, Po and other radionuclides. Finally, our results might add further complexities to the discussion of the potential of Th/Pa fractionation by MnO2 phases in seawater.