Effect of Humic Acid on the Electrophoretic Mobility of Uranium (VI) in Aqueous Solutions

The speciation of uranium (U) in relation to its bioavailability is reviewed for surface waters (fresh-and seawater) and their sediments. A summary of available analytical and modeling techniques for determining U speciation is also presented. U(VI) is the major form of U in oxic surface waters, while U(IV) is the major form in anoxic waters. The bioavailability of U (i.e., its ability to bind to or traverse the cell surface of an organism) is dependent on its speciation, or physicochemical form. U occurs in surface waters in a variety of physicochemical forms, including the free metal ion (U 4+ or UO 2 2+ ) and complexes with inorganic ligands (e.g., uranyl carbonate or uranyl phosphate), and humic substances (HS) (e.g., uranyl fulvate) in dissolved, colloidal, and/or particulate forms. Although the relationship between U speciation and bioavailability is complex, there is reasonable evidence to indicate that UO 2 2+ and UO 2 OH + are the major forms of U(VI) available to organisms, rather than U in strong complexes (e.g., uranyl fulvate) or adsorbed to colloidal and/or particulate matter. U(VI) complexes with inorganic ligands (e.g., carbonate or phosphate) and HS apparently reduce the bioavailability of U by reducing the activity of UO 2 2+ and UO 2 OH + . The majority of studies have used the results from thermodynamic speciation modeling to support these conclusions. Time-resolved laser-induced fluorescence spectroscopy is the only analytical technique able to directly determine specific U species, but is limited in use to freshwaters of low pH and ionic strength. Nearly all of the available information relating the speciation of U to its bioavailability has been derived using simple, chemically defined experimental freshwaters, rather than natural waters. No data are available for estuarine or seawater. Furthermore, there are no available data on the relationship between U speciation and bioavailability in sediments. An understanding of this relationship has been hindered due to the lack of direct quantitative U speciation techniques for particulate phases. More robust analytical techniques for determining the speciation of U in natural surface waters are needed before the relationship between U speciation and bioavailability can be clarified.

show abstract

“…Oxidation state (U(IV) or U(VI)) in water [28,51] Capillary electrophoresis Uranyl complexation with humic and fulvic acids in water [29,116] …”

Section: Watermentioning

confidence: 99%

Uranium Speciation and Bioavailability in Aquatic Systems: An Overview

Markich

2002

The Scientific World JOURNAL

200

142

View full text Add to dashboard Cite

show abstract

“…Various inorganic and biological systems were studied and interactions between human transferring and U were characterized with the aid of time-resolved LIF detection Ore samples [64] LE, leading electrolyte; TE, terminating electrolyte; HFCCD, high-frequency contactless conductivity detector [41]. Free-liquid electrophoresis was used to study the interactions of U(VI) with humic acids (HA) and to determine the mobility of the U-HA complexes [87]. The electrophoretic mobility measurements were used to characterize U(VI)-carbonato complexes and their interactions with hematite [88].…”

Section: Applicationsmentioning

confidence: 99%

Analytical separations of lanthanides and actinides by capillary electrophoresis

Janoš

2003

Electrophoresis

View full text Add to dashboard Cite

The separation of lanthanide and actinide elements belongs to one of the most challenging tasks of the separation science, due to a great similarity in their physical and chemical properties. The electrophoretic separation can be accomplished in the presence of suitable complex-forming agents, from which alpha-hydroxyisobutyric acid (HIBA) has been used most often. In the most effective capillary electrophoretic mode--capillary zone electrophoresis (CZE)--a complete separation of lanthanide ions can be accomplished within a few minutes. Various electrophoretic methods can be relatively easily adopted for the determinations of individual lanthanide elements in certain kinds of technical materials, concentrates, precursors, etc., where the high speed and low costs of analysis characteristics of capillary electrophoresis (CE) may be advantageously exploited. Electrophoretic techniques may also be employed for speciation studies, especially for examinations of the behavior of actinides in the environment.

show abstract

“…Numerous studies have clearly shown that humic acids (HA) are important ligands, significantly affecting the sorption and mobility behaviour of actinides in the environment. [1][2][3][4][5][6][7][8] Humics, polyelectrolyte organic macromolecules, are ubiquitous in natural aquifers, with concentrations in the groundwater estimated to range from less than 1 mg L À1 to more than 100 mg L À1 . 9 HA bind virtually all metal ions, affect strongly the speciation and transport of radionuclides, including the actinide elements, and are one of the most important environmental ligands, significantly influencing U(VI) speciation in natural aquifer systems.…”

Section: Introductionmentioning

confidence: 99%

The effect of humic acid on uranyl sorption onto bentonite at trace uranium levels

et al. 2012

View full text Add to dashboard Cite

The effect of humic acid (HA) on U(VI) sorption on bentonite was studied in batch experiments at room temperature and ambient atmosphere at a (237)U(VI) concentration of 8.4 × 10(-11) M and HA concentration of 100 mg L(-1). The distribution of U(VI) between the liquid and solid phases was studied as a function of pH and ionic strength both in the absence and presence of HA. It was shown that the uranyl sorption on bentonite is strongly dependent on pH and the presence of humics, and the effect of the addition order was negligible. In the absence of HA an enhancement in the uptake with increasing pH was observed and a sharp sorption edge was found to take place between pH 3.2 and 4.2. The presence of HA slightly increases uranium(VI) sorption at low pH and curtails it at moderate pH, compared to the absence of HA. In the basic pH range for both the presence and absence of HA the sorption of uranium is significantly reduced, which could be attributed to the formation of soluble uranyl carbonate complexes. The influence of ionic strength on U(VI) and HA uptake by bentonite were investigated in the range of 0.01-1.0 M, and while there was an enhancement in the sorption of humic acid with increasing ionic strength, no significant effect of the ionic strength on the U(VI) sorption was observed in both the absence and presence of HA.

show abstract

Effect of Humic Acid on the Electrophoretic Mobility of Uranium (VI) in Aqueous Solutions

Cited by 7 publications

References 20 publications

Uranium Speciation and Bioavailability in Aquatic Systems: An Overview

Uranium Speciation and Bioavailability in Aquatic Systems: An Overview

Analytical separations of lanthanides and actinides by capillary electrophoresis

The effect of humic acid on uranyl sorption onto bentonite at trace uranium levels

Contact Info

Product

Resources

About