Speciation of Fe(III) Radionuclides in Aqueous Solutions

Fe(III) radionuclide speciation in aqueous solutions at pH ranging from 1 to 12 and Fe(III) concentration, from 1 ×10^-7 to 1 ×10^-2 M was studied. At trace Fe(III) concentrations (1 ×10^-7 M), the sorption colloids, so-called pseudocolloids, are formed within pH range 3-12. At pH within 0.7-1.5, Fe(III) exists in the form of hydrated cations Fe(H₂O)₆³⁺, which are hydrolyzed at pH > 1.5 (K_h = 3.7 ×10^-3) to form mononuclear Fe(OH)²⁺ hydroxo complexes. At Fe(III) concentration exceeding 1 ×10^-4 M, Fe₂(OH)5.70.3+ binuclear hydroxo complexes are formed.