Curium / Actinides / Carbonate complexation / Fluorescence spectroscopy SummaryThe carbonate complexation of Cm(III) is investigated by means of time resolved laser fluorescence spectroscopy (TRLFS) at 25°C in 1 m NaCl as a function of the carbonate concentration. In the first set of experiments, the carbonate concentration is controlled by the C0 2 equilibrium partial pressure, (pC0 2 = 10-1000 mbar) and pH whereas the second set of batch experiments is performed at higher carbonate concentrations ([CO §~] > 10 4 molal). Both data sets overlap in the intermediate range and fit well together. The carbonate complexes CmCOJ, Cm(C0 3 ) 2 and Cm(C0 3 ) 3~ are quantified spectroscopically in the trace concentration range by peak deconvolution of fluorescence emission spectra. At pC0 2 = 500 or 1000 mbar and pH < 6.5, there is evidence for the formation of a Cm(III) bicarbonate complex to a small extent. Up to pH 9.5 there is no indication for the formation of mixed hydroxo carbonate complexes. At high carbonate concentrations (> 0.1 molal), the formation of an additional complex, Cm(C0 3 )4~, is indicated. The stability constants determined in 1 molal NaCl solution are found to be: logy?(CmHCO! + ) = 1.9; logy?(CmC0 3 + ) = 5.90; log0(Cm(CO 3 ) 2 ) = 10.27; log^(Cm(C0 3 )D = 13.18; log/? (Cm(C0 3 )D = 14.18.

Trivalent actinides / Curium / Fluoride complexation / Pitzer model SummaryThe fluoride complexation of Cm(III) is investigated by means of time-resolved laser fluorescence spectroscopy (TRLFS) at 25°C. In the first set of experiments, the speciation of Cm(III) is investigated in 1 m NaCl as function of the fluoride concentration (m F < 8 · 10 1 m). The monofluoride complex CmF 2+ is identified and its formation constant is determined to be log^(CmF 2+ ) = 2.46 ± 0.05. At the highest fluoride concentration there is evidence for the formation of a Cm(III) difluoride complex to a small extent. However, as the fluoride concentration interval is limited by the precipitation of CmF,(s), the stability constant of CmP + can not be quantified. In the second set of experiments the formation of CmF 2+ is studied in 0-5 m NaCl. The ionic strength dependence of the formation constant is described by modeling the activity coefficients with the ion interaction approach (Pitzer equations). The formation constant at / = 0 is calculated to be log^°(CmP + ) = 3.44 ± 0.05.

Aqueous solutions of higher homologues of tetraalkylammonium salts exhibit liquid-liquid phase separation. A model study of the pressure-temperatureomposition (p,T,x) surface of immiscibility of tetraisopentylammonium bromide + H20 up to 370 K and 200 MPa yielded a closed miscibility gap at atmospheric pressure with its lower part suppressed by crystallization, and a very unusual hyperbolic shape of the p,T,x surface. The results reflect a very peculiar behavior of the thermodynamic excess functions of aqueous solutions of hydrophobic ions which is discussed in relation to known regularities in the thermodynamic properties of the lower homologues which are completely miscible with water. IntroductionSymmetrical quarternary ammonium salts (R4N+X-, where R stands for alkyl chains) form an interesting class of 1 : 1 electrolytes which are capable of subtle and nearly continuous structure variations. Thermodynamic aspects of their hydration and mutual

Performances of four related techniques i.e., photoacoustic spectroscopy, photothermal deflection, thermal lensing, and photothermal phase shift spectroscopy have been compared to the conventional beam transmittance spectrophotometry. This concerns to the analytical potential in studies of environmental pollutants. Solutions of pesticides in water are used as specimens in this study. Spectrophotometric, photoacoustic and thermal lensing techniques are also used as detector behind HPLC loaded with a mixture of methanol and water. Thermal lensing and photothermal deflection spectroscopy appear superior in determination of environmental pollutants. The detection limit obtained for pesticides is 0.1 pglkg.

No abstract