Complexes of americium

Americium sorption was decreased significantly when HEDTA or EDTA were present. Complexation of americium by these strong chelating agents was responsible for this behavior. Sodium hydroxide increased americium sorption but, again, its effect on americium was probably a manifestation of its effect on the sediment minerals. 

Relatively few complexes of americium have been characterized those that have tend to resemble the corresponding compounds of the three previous metals. Many are halide complexes, such as (NH4)4 [AmFg], which resembles the U analogue, Cs2NaAmCl6, and (Ph3PH)3AmX6 (X = Cl, Br). 

Nearly all of the formation constants listed in Table 8.8 are for complexes formed by Am(iii), as little work has been done on complexes of americium with oxidation states higher than iii. Color changes indicate existence of Am(vi) nitrate, sulfate, and fluoride complexes. There is also spectrophotometric evidence [299] for the existence in 1 m NaOH solution of a peroxide complex of... 

Table 8.8 Complexes of americium(III) with inorganic ligands. ... 

Moskvin AI, Khalturin GV, Gel man AD (1962) Determination of the composition and instability constants of citrate and tartrate complexes of americium(III) by the ion-exchange method. Radiokhim 4 162-166... 

The metabolism of americium consists of binding interactions with proteins and probably complex formation with various inorganic anions such as carbonate and phosphate, and carboxylic acids such as citrate and lactate (Durbin 1973 Taylor 1973 Webb et al. 1998). These types of interactions would be expected for all routes of exposure. 

Methods for reducing peak absorption of americium after inhalation or oral exposure have not been described. Topical applications of saline containing DTP A, tartaric acid, or citric acid (e.g., Schubert s solution) have been used to remove americium from the skin and wounds after accidental dermal exposures (Breitenstein 1983). These agents form stable, water soluble complexes with americium. 

Calcium or zinc complexes of polycarboxylate compounds such as DTPA or ethylenediaminetetratacetic acid (EDTA) have been used as chelating agents to accelerate the urinary excretion of americium in humans who were accidentally exposed to americium (Breitenstein 1983 Doerfel and Oliveira 1989 ... 

Fuger, J. (1958). Ion exchange behavior and dissociation constants of americium, curium and californium complexes with ethylenediaminetetraacetic acid, J. Inorg. Nucl. Chem. 5, 332. 

In solution Am4+ ion is not so stable, slowly reducing to trivalent Am3+. However, simple and also complex tetravalent compounds of americium are known. Some examples are Am(OH)4, AmF4, LiAmFs, andK2AmF4. Am(OEf)4 is stable in basic solution and results from the oxidation of Am(OH)3 by hypochlorite ion. 

The nitratocomplexes MIAm02(N03)3 (M1 = Rb or Cs424) are precipitated from nitric acid solutions of americium(VI). The IR spectrum of RbAm02(N03)3 has been reported.249 Hydrated phosphato, arsenato and sulfato complex salts are included under Aqua species in the preceding section. 

Partition behaviour of americium(III) chelates with cupferron and other bidentate reagents was studied spectrophotometrically between a number of inert solvents and dilute HC104 solutions.98 Of special interest may be the data on their extractability and colours of chloroform extracts, collected in a tabular form for cupferronate derivatives of 58 metals. The pH ranges for the formation of cupferronates of 39 metal ions have been shown graphically in this publication.99 Solvent extraction and polarographic techniques were employed to study the possible adducts between technetium and cupferron.100 Evidence indicates a Tcm cupferronate and possibly a pertechnitate adduct, but no indication of a technetium(IV) complex was obtained. 

Rizkalla, E.N., Sullivan, J.C., Choppin, G.R. 1989. Calorimetric studies of americium(IH) complexation by amino carboxylates. Inorganic Chemistry 28 909-911. 

Zhu, Y., Xu, J., Chen, J., Chen, Y. 1998. Extraction of americium and lanthanides by dialkyldithiophosphinic acid and /-/ absorption spectra of the extraction complexes. Journal of Alloys and Compounds 271-273 742-745. 

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