Probing Uranium(IV) Hydrolyzed Colloids and Polymers by Light Scattering

Tetravalent uranium readily undergoes hydrolysis even in highly acidic aqueous solutions. In the present work, solutions ranging from 0.4 to 19 mM (total U) concentration ( 1 < pH < 4 ) are carefully investigated by light scattering technique with special emphasis on polymerization leading to colloid formation. The results clearly indicate that the concentration has significant effect on particle size as well as stability of colloids. With increasing concentration the size of colloids formed is smaller due to more crystalline nature of the colloids. Stability of colloids formed at lower concentration is greater than that of colloids formed at higher concentration. Weight average molecular weight of the freshly prepared and colloidal polymers aged for 3 days is determined from the Debye plot. It increases from 1,800 to 13,000 Da. 40–50 atoms of U are considered to be present in the polymer. Positive value of second virial coefficient shows that solute-solvent interaction is high leading to stable suspension. The results of this work are a clear indication that U(IV) hydrolysis does not differ from hydrolysis of Pu(IV).