Redox stability of neptunium(V) and neptunium(IV) in the presence of humic substances of varying functionality
-
K. Schmeide
Abstract
The reducing properties of humic substances (humic acid (HA) and fulvic acid (FA)) of varying functionality towards Np(V) have been studied under anaerobic conditions between pH 3.5 and pH 9.0 in batch experiments. For Np redox speciation in solution solvent extraction, NIR absorption spectroscopy and ultrafiltration were applied. The reduction rate varied with type of humic substances, solution pH, HA to Np concentration ratio, and equilibration time. In comparison to natural humic substances, synthetic HA with designed redox properties lead to a stronger reduction of Np(V) to Np(IV). The reducing capacities of humic substances towards Np(V) could be correlated to their phenolic/acidic OH group content, which includes both hydroquinone-like moieties and non-quinoid phenols. By applying a synthetic HA with blocked phenolic/acidic OH groups, the dominance of phenolic/acidic OH groups as the redox-active moieties of humic substances was verified.
The Np(IV) formed in the course of the experiments is predominantly humic colloid-bound. Np(IV) oxo/hydroxide colloids, that might be formed in addition, are stabilized by adsorbed humic substances. The remaining Np(V) occurs as NpO2+ ion or Np(V) humate depending on pH. The ability of synthetic HA to effectively maintain Np in the tetravalent state during humate complexation experiments could be shown.
© by Oldenbourg Wissenschaftsverlag, München, Germany
Articles in the same Issue
- Redox stability of neptunium(V) and neptunium(IV) in the presence of humic substances of varying functionality
- Differential pulse cathodic stripping voltammetric determination of uranium with arsenazo-III at the hanging mercury dropping electrode
- Effect of pH and ionic strength on sorption of Eu(III) to MX-80 bentonite: batch and XAFS study
- Determination of 45Ca and γ-emitting radionuclides in concrete from a nuclear power plant
- Extraction of long-lived radionuclides 152,154Eu and 134Cs using environmentally benign aqueous biphasic system
- Determination of major and trace elements in iron-nickel-copper-cobalt ore reference materials using k0-NAA
- Development and implementation of k0-INAA standardization at 10 MW Pakistan research reactor-1
- Radiation chemical study on benzaldehyde–chlorobenzene system: A novel radiation chemical route for benzophenone formation
Articles in the same Issue
- Redox stability of neptunium(V) and neptunium(IV) in the presence of humic substances of varying functionality
- Differential pulse cathodic stripping voltammetric determination of uranium with arsenazo-III at the hanging mercury dropping electrode
- Effect of pH and ionic strength on sorption of Eu(III) to MX-80 bentonite: batch and XAFS study
- Determination of 45Ca and γ-emitting radionuclides in concrete from a nuclear power plant
- Extraction of long-lived radionuclides 152,154Eu and 134Cs using environmentally benign aqueous biphasic system
- Determination of major and trace elements in iron-nickel-copper-cobalt ore reference materials using k0-NAA
- Development and implementation of k0-INAA standardization at 10 MW Pakistan research reactor-1
- Radiation chemical study on benzaldehyde–chlorobenzene system: A novel radiation chemical route for benzophenone formation
