Alexander Redkin

Experimental Cs and Sr sorption on analcime in rock-buffered systems at 250–300°C and Psat and the thermodynamic evaluation of mineral solubilities and phase relations

Experimental studies on replacement of Na by Cs and Sr in analcime-albite bearing buffered assemblages were carried out at 250–300°C and P sat = 39.7-85.8 bars in pure water and in chloride solution. This investigation shows that such ion exchange of Na for Cs and Sr in analcime changes the Si/Al ratio. The compositions of end members for Cs and Sr analcimes at 250°C are shown to be Cs 0.95 Al 0.79 Si 2.17 O6 and Sr 0.645 Al 1.41 Si 1.62 O 6 . Continuous solid solutions between Cs and Na and Sr and Na do not appear to exist. Based on the composition of the aqueous chloride solutions, the thermodynamic properties of Cs, Sr and Na analcimes were determined and used in thermodynamic simulations in Cs and Sr leaching from albite-(Cs, Sr, Na) analcime assemblages at 250°C. In line with the above, the minimum leachability of Cs and Sr from Cs- and Sr-bearing analcimes occurs at pH values above 8 with an analcime-albite-paragonite buffer. The analcime-albite-paragonite assemblage can, therefore, act as a potential sorption barrier to the migration of Cs and Sr from radionuclide contaminated materials owing to the insolubility of Cs and Sr bearing analcimes. These findings have implications for underground High Level Waste storage facilities designed for maximum safety at moderately elevated temperatures.

Reduction of the Operating Temperature of Aluminum Electrolysis: Low Temperature Electrolyte

Potassium Aluminum Fluoride obtained as a byproduct in the aluminum grain refiners and master alloys production may be used as an additive to the aluminum reduction process. The component leads to a considerable reduction in the liquidus temperature, and maintains other important parameters such as electrolyte conductivity and solubility of alumina. Both, laboratory tests and semi industrial trials in a 100A cell have been conducted in order to test the suitability of this new additive to the electrolytic process, with positive results. Potassium Aluminum Fluoride can be also used as a basic component of the low-temperature electrolyte for aluminum electrolysis.