Aluminate(1-), tetrafluoro-, cesium (1:1), (T-4)-

Endpoint summary

Additional information

Stability/degradation: Due to the fact that cesium tetrafluoroaluminate is an inorganic substance, only abiotic degradation can be considered. A hydrolysis test was performed as part of a solubility study at varying pH values. Although the study was not performed according to GLP criteria or normalised testing guideline, the results are considered adequate for assessment. In native and acidic solution there is no remarkable evidence of hydrolysis, being the mol ration of Cs, Al and F in solution close to the theoretical 1:1:4 of CsAlF4. Cesium tetrafluoroaluminate will most probably mainly dissociate into Cs+ and AlF4 -. In neutral and alkaline environment a gel-like residue is formed which could not be separated from the solution. The XRD results and the mol ration indicate that in alkaline solution AlF₄ ^-, AlF₅^2- and F^- as anions and as cations Cs+ and Al+ appear. The reduced aluminium content in the clear pH 9 solution may probably result from a precipitation of aluminium fluoride or aluminium hydroxyfluoride. Since hydrolyses changes the chemical form but does not decompose cesium tetrafluoroaluminate, the concept of degradation by hydrolysis is not relevant in the consideration of its environmental fate.

Adsorption/desorption:

Adsorption of cesium tetrafluoroaluminate to soil is not to be expected as the substance instantly dissociates into various ions. The following information is available on the adsorption of cesium and fluoride ions. For cesium the lowest Kd value was 0.6 L/kg for a measurement made on a system containing a soil consisting primarily of quartz, kaolinite, and dolomite and an aqueous phase consisting of groundwater with a relatively high ionic strength (I. 0.1 M). The largest cesium Kd values was 52,000 L/kg for a measurement made on a pure vermiculite solid phase . The average cesium Kd value was 2635 ± 530 L/kg. For fluoride a Koc value of 3.16 is calculated based on a log Kow of -1 in EUSES (in the EU-RAR for hydrogen fluoride a log Kow of -1.4 is suggested). From the data available for aluminium, no actual Kd and/or Koc values can be determined.