Uranyl hydrogel leaching as one of technological nodes of sol-gel process. Part 3

The process of leaching is described of the fine fraction of uranyl hydrogel prepared by internal gelation from aqueous solutions of uranyl nitrate under the action of urea and urotropin. For preparing the dispersion a two-liquid jet was used which provided a polydispersion mixture with mean particle size of around 300 μm. Leaching took place in a 0.5 to 2 molar aqueous solution of ammonia at the solid:liquid phase ratio in the range of 1:10 to 1:2 with the addition of a wetting agent in extraction containers for a period of 5 to 60 mins. The effect of the said parameters was studied on the uranium content - the residual content of nitrate ions, carbon and the content of adsorbed NH4OH in the solid phase and the content of leached nitrate ions and uranium in the leaching solution. The leaching process was so rapid that after 5 mins steady state was achieved and further leaching for over 60 mins affected the composition of neither the solid nor the liquid phase. Under the conditions the optimal arrangement of the experiment appears to be leaching with ca. 1 M agueous solution of ammonia at a s:l ratio of 1:5 over 10 mins. The kinetics of leaching carbonaceous substances was evaluated by previously verified equations and the diffusion mechanism of the formation of a stabilized skeleton of ammonium polyuranate was confirmed. (author)