REGENERATING SOLUTION COMPOSITION FOR SILICON REMOVAL AND ANION-EXCHANGE RESIN RESTORATION IN URANIUM EXTRACTION

Abstract

The effect of the composition of regenerating solutions on the removal of silicon-containing and related impurities from anion exchange resins used for sorption extraction of uranium from productive solutions of in-situ leaching was investigated. The objects were technological solutions and regenerated resins from the Akdala and South Inkai deposits. The elemental composition was determined by atomic emission and X-ray fluorescence methods, and the phase composition of solid residues was determined by X-ray phase analysis. Screening of the NaOH–Na₂SO₄, H₂SO₄–NH₄HF₂ and HNO₃–NH₄HF₂ systems showed silicon removal at 90.2–97.9; 93.3–95.0 and 95.7–97.5%, respectively. The HNO₃–NH₄HF₂ system, despite its effectiveness, is excluded due to the high affinity of nitrate ions for the resin; NaOH–Na₂SO₄ and H₂SO₄–NH₄HF₂ were then studied. Increasing the concentrations of NaOH and Na₂SO₄ to 75 and 100 g/l increased silicon removal to 97.5–98.7% but could reduce the strength of the resin. A solution of 25 g/l of NaOH + 25 g/l of Na₂SO₄ removed 93.1% of Si, retained strength of 76.5%, increased hydrodynamic index by 30% and uranium capacity from 10.75 to 13.89 g/l; a solution of 150 g/l H₂SO₄ + 150 g/l NH₄HF₂ increased the capacity to 16.69 g/l. The choice of regenerating solution should consider not only the removal of silicon, but also the degree of purification, strength, hydrodynamic and sorption properties of the resin.