Hydrothermal Synthesis of Cesium and Strontium Bearing Mineral-Like Phases Using Coal Fly Ash Cenospheres

The possibility of hydrothermal synthesis of Cs and Sr bearing framework aluminosilicates in the CsNO3-NaOH-H2O-(SiO2-Al2O3)(glass) and Sr(NO3)(2)-NaOH-H2O-(SiO2-Al2O3)(glass) systems using coal fly ash cenospheres was studied as a low-temperature method to include the water-soluble forms of radionuclides Cs-137 aleph Sr-90 in a mineral-like form. The syntheses were carried out at temperatures in the range of 80-200 degrees C and autogenous pressure. Narrow fractions of cenospheres with the glass phase content of 90-95 mass % were used as aluminosilicate glass, and compounds of stable isotopes of Cs and Sr were used as imitators of radionuclides Cs-137 aleph Sr-90. Based on the data obtained in the studies of solid products and post-synthetic solutions by means of X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray microanalysis (SEM-EDX) and atomic absorption spectroscopy (AAS), it was established that the Cs bearing analcime-pollucite solid solutions (NanCs1-n)AlSi2O6 center dot nH(2)O are crystallized in the Cs-containing system at 120-150 degrees C with 98 % Cs+ removal from solution to the solid product. The Sr bearing phases of tobermorite and plagioclase structural types are formed in the Sr(NO3)(2)-NaOH-H2O-(SiO2-Al2O3)(glass) system. In this case, the effectiveness of Sr2+ extraction from solution is not less than 99.99 %.

Automated summary

Hydrothermal synthesis using coal fly ash cenospheres was studied as a low-temperature method to incorporate water-soluble forms of Cs-137 and Sr-90 in mineral-like aluminosilicates. The Cs-bearing analcime-pollucite solid solutions were crystallized at 120-150 degrees C with 98% Cs+ removal efficiency, while Sr-bearing tobermorite and plagioclase phases were formed in the Sr-containing system with extraction efficiency of Sr2+ not less than 99.99%.