Speciation of Cr(III) radionuclides in solutions

The speciation of Cr(III) radionuclides in solutions within the concentration range 10−6–10−2 M at pH 1–12 was studied. Adsorption on the glass surface, ion exchange, migration in the electric field, centrifugation, dialysis, and ultrafiltration were used. It was found that, at a concentration of 10−6 M at pH 1.0–4.4, Cr(III) exists in the solution as a monomeric species, and at pH > 4 it exhibits colloidal properties. At pH 1.0–3.4, Cr(III) exists in form of hydrated cations Cr(H2O)3+6. At pH > 3.4, they are hydrolysed with formation of mononuclear hydroxo complexes Cr(OH)2+ [Kh (3.35 ⊥ 0.15) × 10−5]. At the Cr(III) concentration exceeding 1 × 10−4 M, binuclear hydroxo complexes Cr2(OH)q are formed.