Complexation Chemistry of Zirconium(IV), Uranium(VI), and Iron(III) with Acetohydroxamic Acid

Abstract

The complexation of zirconium(IV), uranium(VI), and iron(III) with acetohydroxamic acid (AHA) has been analyzed spectrophotometrically in various ionic strengths at 25°C. Arsenazo III (AAIII) was used as an indicator for unbound zirconium. The SQUAD computational program was employed to evaluate the stability constants. Conditional stability constants of four zirconium complexes Zr(AAIII)³⁺, , Zr(AHA)³⁺, and were determined in 1 mol · L⁻¹ HClO₄ as log β′ = 5.09, 10.29, 12.78, and 23.13, respectively. Conditional stability constants of UO₂(AHA)⁺, Fe(AHA)²⁺, , and Fe(AHA)₃, in 0.1 mol · L⁻¹ HNO₃ were calculated as  = 8.32, 11.00, 20.93, and 28.75, respectively.

Keywords:

• arsenazo III
• complexation
• hydroxamic acid
• iron
• SQUAD
• uranium
• zirconium

ACKNOWLEDGEMENTS

We express our gratitude to Lin Kong for his work of the uranium spectroscopy experiments. We thank Peter Sprunger for creating a Java program to align the SQUAD input files. This research was performed under the financial support of the Office of Civilian Radioactive Waste Management Graduate Fellowship Program administered by Oak Ridge Institute for Science and Education and USDOE NERI Program, Award 054657.

Notes

Note: Conditional stability constants for Andrieux el al. (17) at 25°C for 0 ≤ pH ≤ 1.00 and  ≈ 0.1 mol · L⁻¹ were calculated from their published data for comparative purposes using 9.33 (3) as the pK_a for AHA at I = 0.1 mol · L⁻¹.

Note: Koide et al. (10) determined UO₂(AHA)⁺ stability constant using potentiometric titration at 25°C.