2-STAGE SOLUBILIZATION OF POORLY SOLUBLE POLYVALENT METAL FULVATES

The mechanism of solubilization of poorly soluble gel phases of polyva lent metal fulvates is studied by examples of europium(III) and uranyl fulvates in HCl and EDTA solutions, using spectroscopic and physicoch emical methods. Europium fulvate undergoes solubilization by a two-sta ge mechanism. In the first stage, the solubilizing agent displaces Eu( III) from the gel phase, with no degradation of the polymer matrix. In HCl solutions, the gel phase absorbs a considerable excess of HCl rel ative to the amount required for purely ion-exchange mechanism. In the second stage, after about 60% of the initial metal passes into soluti on, the gel phase loses its aggregative stability, and simultaneous so lubilization of the fulvate component starts. Uranyl forms less stable coordination polymers, and their solubilization proceeds by the secon d mechanism only.