In situ type study of hydrothermally prepared titanates and silicotitanates

One of the most vexing problems facing the nuclear industry and countries with nuclear weapons is the safe disposal of the generated nuclear waste. Huge quantities of nuclear waste arising from weapons manufacture are stored at the Hanford and Savannah River sites in the USA. The general method of remediation involves the removal of Cs-137, Sr-90 and actinides from a huge quantity of salts, principally NaNO3, organics and complexing agents. It has been found that a sodium silicotitanate is able to remove Cs+ selectively from the waste and certain sodium titanates remove Sr2+ and actinides. These compounds have been prepared by ex-situ hydrothermal methods. We have studied the in situ growth of these materials at the National Synchrotron Light Source, Brookhaven National Laboratory. In addition we will describe the mechanism of ion exchange in the titanosilicate as observed by in situ methods and how the combination of these techniques coupled with an intimate knowledge of the structure of the solids is helping to solve the remediation process. In general, the in situ method allows the investigator to follow the nucleation and crystal growth or phase transformations occurring in hydrothermal reactions.