MINERAL COMPOSITION AND ADSORPTION CAPACITY OF PRECIPITATES FORMED DURING OZONATION OF RADIOACTIVELY CONTAMINATED WATER FROM NUCLEAR POWER PLANTS TOWARDS 137Cs

The mineral composition and sorption properties of precipitates formed during ozonation of a model solution simulating nuclear power plant wastewater (total mineralization 7 g/dm3, pH = 11.5, T = 60°C, t = 2 hours) 137Cs were studied. The precipitate is represented by finely dispersed spherical particles of metal oxides ranging in size from 20 to 30 nm, forming microaggregates and their associates of various shapes. The composition of the precipitates, along with X-ray amorphous phases, includes Fe(II)-Fe(III) layered double hydroxides (Green Rust), as well as LDH of mixed composition, in particular Fe-Co, and iron oxyhydroxides — goethite and lepidocrocite. The precipitates also contain manganese-containing phases represented by manganese (IV) hydroxide and manganese (II) carbonate with an admixture of manganese oxides, such as Mn2O3∙H2O, MnO, Mn3O4 (gaussmanite). In the process of ozonation, organic compounds that are part of the solutions undergo destruction, co-precipitation with other components of the solution, which is accompanied by the sorption of 137Cs radionuclides on the surface of mineral particles. An increase in the concentration of Fe2+ and Mn2+ cations by 10 times (up to 50 and 100 mg/dm3, respectively) in wastewater reduces the concentration of 137Cs in the initial solution by 50.5%.