Speciation of Uranium in Trace Concentrations in Aqueous Solutions of Complex Chemical Composition

Speciation of uranium in trace concentrations in water of complex chemical composition was studied using ultrafiltration and sorption methods in a wide range of solution acidity. As shown by the experiments and computations, uranium in trace concentrations in aqueous solutions identical to wastewater from the facilities occurs at pH 1–3 in the truly dissolved state in the form of UO₂²⁺ and UO₂OH⁺ ions. At pH ≥ 4, uranium(VI) mainly occurs in the pseudocolloidal form due to sorption on hydroxides of iron, aluminum, or other impurity elements. The decrease in the fraction of uranium colloids at pH ≥ 7 is due to the formation of stable, negatively charged uranyl carbonate complexes in the solution.