The use of composite sorbents based on nickel ferrocyanide in determination of cesium radionuclides in natural water samples

The paper presents results of two inorganic sorbents for the cesium selective concentration in the scheme of 137Cs radio/chemical analysis in natural water samples. Nickel/potassium ferrocyanide dispersed in a zirconium dioxide matrix obtained by the sol/gel method with subsequent drying at 100 ºC (Т-35 sorbent produced by AO “Termoksid”), and nickel/potassium ferrocyanide chemically deposited upon a matrix of hydrated titanium dioxide thermally treated at 400 ºC (NKF-GDT sorbent developed by UrFU). We have shown that in the dynamic conditions NKF-GDT sorbent possesses significantly higher sorption properties in comparison with T-35 in spite of close to similar sorption characteristics in the static conditions. For both sorbents we have shown that the degree of cesium sorption from acidulated sea water (pH = 2) is significantly higher that from neutral or low-alkaline water (pH = 28.2). This can be explained by formation of relatively stable pseudo/radio/colloid forms of cesium at pH = 28.2 that are to be destroyed with the solution acidulation. The authors have stated that NKF-GDT sorbent can be used for 137Cs selective concentration from various types of natural water samples. The radio/chemical analysis scheme has been tested with 7.2 l water sample from the Techa River (ChelyabinskOblast) with addition of 0.1 mg/l of stable cesium for determination of the output with ICP-MS instrument. Total chemical output of cesium in the process of concentration was 91.7 % and specific activity of 137Cs in the sample was 1.36±0.21 Bq/l.