Method for Removing Cationic Radionuclides from Milk

Abstract

A new method for the removal of radioactive strontium, barium, and cesium from milk has been developed. Fresh samples of raw whole milk with added Sr ~, Ba 1', or Cs TM were stored at 4 C. for at least 72 hr. The samples were then adjusted to a pI4 of 5.4 or 5.3 with 0.1 or 0.5 M citric acid and passed through a column containing Dowex 50W-X8 cationic resin in the Cal~gKNa cycle. The resin was previously eharged with a mixed salt solution containing Ca, Mg, K, and Na chlorides in approximately the same relative proportions as in the milk, but at five times their usual concentrations, and at the same pH of acidified milk. After treatment, the milk was mixed with Dowex 2-X8 anionic resin in the OH-cycle, by the batch process, and the pH was brought to 6.6. The milk was filtered through a cheese cloth to remove the spent resin. Analysis of treated milk indicated that approximately 90-95% of Sr ~, 85-95% of Ba 1', and 75% of Cs TM were removed by this treatment from 25 resin-bed volumes of milk. The removal of radionuclides did not vary with flow rates of 5-25 ml. per minute and the cationic composition of the milk was essentially unchanged. Although the milk was not coagulable by rennin, addition of 2-3 ml. of 1 M CaCl~ solution per liter of milk yielded coagulum comparable to that obtained with untreated milk. Further treatment of the final product with a CalVIgKNa resin at pl~ 6.6 resalted in an additional removal of approximately 45, 30, and 90% of residual Sr ~, Ba 1~, and Cs TM remaining after the initial treatment without further change in the gross cationic composition of the milk. Results obtained at pH 5.2-5.3 with milk labeled in vivo and in vitro were similar.