No abstract

No abstract

No abstract

For the enrichment or the simple recovery of caesium from river and sea waters, selective inorganic exchangers were considered. Ammonium hesacyanocobalt ferrate (NCFC) was chosen because it can be used in strongly acidic solutions (with the exception of concentrated sulphuric acid), Cacsium is fully retained by the NCFC chromatographic column and can then be recovered by dissolution in hot sulphuric acid. The solution is then diluted and analysed, either directly or following caesiuni separation, by atomicabsorption spectrometry.To check the reliability of the analytical procedure, a series of cxperirnents were carried out in which the possible interfering species were added to the aqueous caesium solution prior to analysis. The well known ionic interference in flame atomisation processes caused by magnesium, calcium, strontium and metals was investigated by electrothermal atomisation measurements. The experimental data showed that this effect does not occur even when these elements are present in concentrations of the order of thousands of parts per million. However, strong interferences from iron and cobalt were observed.Keywords: Electvothevmal atomic-absovption spectvometvy; caesiwm detevmination ; cobalt and ivon intevfevemes ; spectval intev fevence ; caesium envichmentNuclear activities, such as electricity production by nuclear power plants, involve the occasional release of small amounts of radionuclides into the environment. Among the possible diffusion paths of such discharges rivers often play a role of paramount importance. Studies on the distribution of radionuclides between river water and the suspended solid materials or sediments can be carried out using radioactive tracer techniques, but they also require analytical methods suitable for the characterisation of the different components of the system. The caesium concentration in these matrices is very low, so that, in addition to a sensitive analytical method, it was necessary to make use of an enrichment technique to bring the caesium concentration within the scope of the analytical method.Atomic-absorption spectrometry was selected as the analytical method because of its sensitivity, speed and ease of operation.For the enrichment or even for the simple recovery of caesium from different solutions, selective inorganic exchangers were considered. Ammonium hexacyanocobalt ferratel (NCFC) was chosen because it can be employed in strongly acidic solutions (with the exception of concentrated sulphuric acid2). The use of NCFC is particularly advantageous for the recovery of caesium from solutions obtained on acid dissolution of mineral or biological materials.Caesium is fully retained by a chromatographic column of NCFC and can then be recovered by dissolution of the NCFC in hot 12 M sulphuric acid. The solution is then evaporated to form a paste, cooled and distilled water is added. When columns of NCFC supported in silica gel are used, the dissolution of the NCFC is made with hot 18 M sulphuric acid with continuous stirring. The solution contains an...

Figure 9. Near-infrared photoacoustic spectrum of praseodymium oxide, Pr,Oll, from 900 t o 2820 nm made with a modulation frequency of 48 Hz, a time constant of 2.5 s, and a bandpass of 26 4 nm The UV-visible spectrum IS saturated well beyond the usual 2500-nm limit.T o illustrate the simplicity of operation, additional rare earth spectra were run. Figures 7 and 8 show the PAS spectrum of neodymium oxide again placed in a sample holder in powder form directly from the original container. Figure 8 illustrates the decrease in signal-to-noise ratio beyond 2500 nm. Similarly, Figure 9 shows the spectrum of praseodymium oxide (Pr60,,) in the near-infrared. The ultraviolet and visible spectra are saturated for this substance.Photoacoustic spectra have been obtained for a wide range of substances including textiles. paint, semiconductors, asbestos, fungi spores, paper, blood smears, and catalysts to name a very few. The number of potential applications is large, and instrumentation is becoming more readily available to make possible the exploration of these essential investigations. LITERATURE CITED(1) M.A method of computation for calibration of photographic emulsion and conversion of microphotometer readings to relative intensities on a digital computer with special application to spectrochemical analysis is descrlbed. A numerical method using cubic spline functions for the treatment of experimental data is discussed. The method extends the operational range of the quantitative determinations from the gross fog level of the emulsion to very high absorbance values approaching saturation. A program is described, that includes an emulsion calibration curve, corrections for the background, and the internal reference ratio calculations. The program provides the automatic selection of the required application through a preliminary analysis of the input data. Various algorithms are described, and some results to test the procedure are given.The use of the photographic plate as a detector has several advantages. A large portion of the spectrum can be recorded simultaneously, and a permanent record is obtained. Since the plate must be exposed for a given time, the radiation intensity is integrated over the exposure time, and random fluctuations typical of discharges are averaged and smoothed out. The outstanding limitation in the use of photographic plates, however, is the complicated relationship between the incident intensity and the consequent plate blackening, which is the information needed for quantitative analysis.The plot of absorbance as a function of the logarithm of the exposure (commonly known as a Hurter-Driffied curve) is linear for a limited region where the intensity calculation is easy so that the possibility of a further extension of this region would be extremely advantageous.In an attempt a t linearizing the calibration curve and thus also at extending the operational range, mathematical transformations of the absorbance values were made by various researchers (1-23). The results, however, were not fully ...