CHARACTERIZATION OF Cr(II) AND Cr(III) ACETATE AQUEOUS SOLUTIONS USING UV-vis SPECTROPHOTOMETRY AND ¹H NMR

Abstract

Aqueous solutions of Cr(II) acetate monohydrate dimer, Cr(III) acetate hydroxide, and commercial Cr(III) acetate 50% active were monitored for 720 h using UV-vis spectrophotometry,¹H nuclear magnetic resonance (¹H NMR), and chromium speciation. The chromium solutions experienced changes in the UV-vis spectra and ¹H NMR behavior with time that can be used to study their kinetics. These changes are governed by temperature and concentration. Cr(III) acetate hydroxide and Cr(III) acetate 50% active solutions exhibit similar spectra and ¹H NMR behavior. Cr(II) acetate solutions have comparatively stable spectra, but experience the most significant ¹H NMR changes. At the experimental conditions of this work, aging of solutions in bulk did not favor the oxidation of Cr(II) or Cr(III) to Cr(VI).

Keywords:

• Cr(II) acetate
• Cr(III) acetate
• ¹H NMR
• UV-vis spectrophotometry

Acknowledgments

The authors thank Dr. Singh and Dr. Connor from the Civil Engineering Department at UNB for allowing us to use the UV spectrophotometer, the UNB MRI Centre (supported by an NSERC MFA award) for allowing us to use the Minispec and for all the technical support, and Mr. Robert Sydansk, from Sydansk Consulting Services, LLC, for his review and comments. The authors are also grateful to NSERC for the Discovery Grant to support project.