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The accident at the Fukushima Daiichi Nuclear Power Plant in 2011 released many radioactive elements into the environment, contaminating a large amount of soil. Currently, 14 million m3 of contamin...

Following identification of radioactive Cs microparticles (CsMPs) in aerosol samples from the Fukushima Daiichi Nuclear Power Plant (FDNPP), numerous reports on CsMPs have been published. This pape...

Microorganisms play an important role in the mineralization of heavy metals in different environments. Previous studies have reported the phosphate mineralization of light (Ce) and heavy (Yb) rare earth elements with yeast. However, little is known about differences in the biomineralization process of middle rare earth elements (including Sm, Eu, Gd, Tb and Dy) by yeast and bacteria. We carried out a series of experiments to compare the sorption process of Sm by Saccharomyces cerevisiae (yeast), Pseudomonas fluorescens (gram-negative bacteria) and Bacillus subtilis (gram-positive bacteria) in initial pH 3, 4 and 5 solutions. The concentrations of Sm in exposure solutions decreased as a function of exposure time in all three systems, which revealed the accumulation of Sm by cells. In both yeast and bacteria systems, Sm(III) was mineralized to monazite(Sm) phase particles on cell surfaces at 5 days of exposure after a short-term adsorption process. In these three systems, nano-sized Sm phosphate formed more quickly on cell surfaces with higher pH exposure solutions. The formation of precipitation on bacterial cell surfaces was faster than in yeast. There were no significant differences in the sorption process of Sm between the two bacteria Pseudomonas fluorescens and Bacillus subtilis.

The uranyl silicate solid uranophane, Ca[(UO2)(SiO3OH)]2·5H2O, is likely an important secondary solid that forms in the alteration of spent nuclear fuel. This 1:1 U(VI)-silicate structure may serve as a host for the incorporation of fission products such as l37Cs or 90Sr by substitution of Ca2+ in interlayer spaces in the solid. We have investigated this possibility by synthesizing 1:1 U(VI)-silicate solids where the Ca2+ is completely or partially replaced by either Sr2+ or Cs+. The solids obtained have been characterized by x-ray powder diffraction (XRD), scanning electron microscopy (SEM), and elemental analysis. We observe that the Sr2+ analog of uranophane yields a diffractogram that resembles the XRD pattern obtained for synthetic uranophane, although the morphology of the solid is different from uranophane. Conversely, substitution of Cs+for Ca2+ in the synthesis of the 1:1 uranyl-silicate solid yields a very different diffractogram but solid phase morphology similar to uranophane. When Ca2+ is par...