Effects of water vapour and temperature on the retention of radiotoxic CH3I by silver faujasite zeolites.

In this work, Ag/X and Ag/Y faujasite zeolites were evaluated as candidate sorbents for the retention of methyl iodide under conditions close to those expected in a severe nuclear accident. Different categories of tests were conducted from laboratory to semi-pilot scales. First, the effects of temperature and water vapour on the CH3I retention/decomposition mechanism were investigated under lab-scale conditions. More specifically, the CH3I adsorption capacities and the fate of its main decomposition products (oxygenated compounds and alkanes) were measured under dynamic conditions at different temperatures (35, 100 and 250 °C). Then, the decontamination factors of Ag/X and Ag/Y silver faujasites exchanged with different silver contents were monitored according to the time on stream using a very low CH3I concentration (1 ppmv). Finally, a parametric study was conducted at semi-pilot scale using realistic [CH3I]/[H2O] molar ratio ≈ 10-6 and temperatures in the range 20-90 °C. Those experiments were helpful in order to assess the effects of some important parameters relevant to the adsorbents or operating conditions.

Optimization of some instrumental factors in diffuse reflectance infrared Fourier transform spectroscopy.

The effects of some instrumental factors on infrared spectroscopy analysis were investigated in the case of diffuse reflectance infrared Fourier transform (DRIFT) mode. It is usually said that quantitative analysis is possible only if both particle size distribution and sample density are perfectly controlled. However, even if these conditions are checked, instrumental factors are of great interest for the goodness of a curve fitting procedure, which is often necessary in solid sample studies. A factorial design achieved on anthron made it possible to obtain major trends concerning the required values for one instrumental parameter (resolution) and two mathematical treatments (zero filling and Savitsky-Golay (S-G) smoothing). Resolution was found to have the greatest effect on measured responses. A value of 2 cm(-1) according to the corresponding aperture is sufficient to approach the real width of bands for powdered samples. The use of a zero filling factor (ZFF) improves the apparent resolution by data interpolation. The best values found for instrumental parameters were applied to an anthron-anthracen mixture. The optimization of spectral features made it possible to obtain semi-quantitative results quite easily, in good agreement with the data corresponding to each pure compound.