Uranium in natural waters

Anderson RE. 1984. A method for determining the oxidation state of uranium in natural waters. Nucl Instrum Methods Phys Res, Sect A 223 213- 217. 

Brits, R. J. N., Smit, M. C. B. Determination of uranium in natural water by preconcentration On anion-exchange resins and delayedneutron counting. Anal. Chem. 49, 67 (1977)... 

Arsenazo III has been used for determining, in strongly acid media, uranium in natural waters [ 142], and in ores and rocks [66], after reduction of U(VI) to U(IV). 

Uranium was determined in phosphoric acid [156] and in ores [157,158] with the use of PAN. The PAR method was applied for determining uranium in natural waters [92,94], sewage [94], rocks and waters [159], geological samples and biological materials [22,36], monazite sands [160], tin [161], and phosphoric acid [96]. 

Another SPE procedure for preconcentration of uranium in natural waters used octadecyl silica membrane disks modified by tri-n-octylphosphine oxide (TOPO) (Shamsipur et al. 1999). The high extractive properties of organic phosphorus compounds for uranyl ions are well known (e.g., TBP in the nuclear fuel cycle). 

Sandino, A. (1991) Processes affecting the mobility of uranium in natural waters. 

Considering the anion concentration ranges in natural waters (Table II) and the magnitude of the corresponding plutonium stability constants (Table III), the chemistry of plutonium, as well as that of uranium and neptunium, is almost entirely dominated by hydroxide and carbonate complexation, considering inorganic complexes only (41, 48, 49). ... 

Langmuir D (1978) Uranium solution-mineral equilibria at low temperatures with applications to sedimentary ore deposits. Geochim Cosmochim Acta 42 547-569 Langmuir D, Herman JS (1980) The mobility of thorium in natural waters at low temperatures. Geochim Cosmochim Acta 44 1753-1766... 

Silver is usually found in extremely low concentrations in natural waters because of its low crustal abundance and low mobility in water (USEPA 1980). One of the highest silver concentrations recorded in freshwater (38 pg/L) occurred in the Colorado River at Loma, Colorado, downstream of an abandoned gold-copper-silver mine, an oil shale extraction plant, a gasoline and coke refinery, and a uranium processing facility (USEPA 1980). The maximum recorded value of silver in tapwater in the United States was 26 pg/L — significantly higher than finished water from the treatment plant (maximum of 5.0 pg/L) — because of the use of tin-silver solders for joining copper pipes in the home, office, or factory (USEPA 1980). 

The bicarbonate ion, HC03, is a prevalent species in natural waters, ranging in concentrations up to 0.8 X 10 3. As was indicated previously, carbonate ions have the ability to form complexes with plutonium. Starik (39) mentions that, in an investigation of the adsorption of uranium, there was a decrease in the adsorption after reaching a maximum, which was explained by the formation of negative carbonate complexes. Kurbatov and co-workers (20) found that increasing the bicarbonate ion concentration in a UXi (thorium) solution decreased the amount of thorium which formed a colloid and became filterable. This again was believed to be caused by the formation of a soluble complex with the bicarbonate. 

Numerous applications of stripping analysis to many relevant environmental, clinical, and industrial problems have been reported. Some typical examples include the determination of uranium or titanium in natural waters [34,62], flow... 

Subramanian and coworkers developed polymeric sorbents using different support materials (such as Merrifield chloromethylated resin, Amberlite XAD 16) and complexing ligands (amides, phosphonic acids, TTA), and evaluated their binding affinity for U(VI) over other diverse ions, even under high acidities. The practical utility of these sorbents was demonstrated using simulated waste solutions (220-222). Shamsipur et al. reported the solid-phase extraction of ultra trace U(VI) in natural waters using octadecyl silica membrane disks modified by TOPO (223). The method was found satisfactory for the extraction and determination of uranium from different water samples. 

Shamsipur, M. Ghiasvand, A.R. Yamini, Y. Solid-phase extraction of ultratrace uranium(VI) in natural waters using octadecyl silica membrane disks modified by tri-N-octylphosphine oxide and its spectrophotometric determination with dibenzoylmethane, Anal. Chem. 65 (1999)4892 1895. 

Unsworth, E. R., Cook, J. M., and Hill, S. J., Determination of uranium and thorium in natural waters with a high matrix concentration using solid-phase extraction inductively coupled plasma mass spectrometry, Anal. Chim. Acta, 442, 141-146, 2001. 

Coprecipitation of Polonium, Radiolead, Uranium, and Plutonium with Manganese Dioxide in Natural Waters... 

Uranium in nature may be measured either radiometrically or chemically because the main isotope - 238U - has a very long half life (i.e., relatively few of its radioactive atoms decay in a year). Its isotopes in water and urine samples usually are at low concentrations, for which popular analytical methods are (1) radiochemical purification plus alpha-particle spectral analysis, (2) neutron activation analysis, (3) fluorimetry, and (4) mass spectrometry. The radiochemical analysis method is similar in principle to that of the measurement of plutonium isotopes in water samples (Experiments 15 and 16). Mass spectrometric measurement involves ionization of the individual atoms of the uranium analyte, separation of the ions by isotopic mass, and measurement of the number of separated isotopic ions (see Chapter 17 of Radioanalytical Chemistry text). 

Other examples of redox-sensitive elements include heavy elements such as uranium, plutonium, and neptunium, all of which can exist in multiple oxidation states in natural waters. Redox conditions in natural waters are also indirectly important for solute species associated with redox-sensitive elements. For example, dissolution of iron (hydr)oxides under reducing conditions may lead to the solubilization and hence mobilization of associated solid phase species, e.g. arsenate, phosphate (see Sections 3.3.2.1, 3.3.3.2, and 3.3.4.1). 

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