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  • Author or Editor: Franco Cataldo x
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Abstract  

A complete analysis of a landfill leachate coming from a landfill site of several years old was performed with a total reflection X-ray fluorescence (TXRF) spectrometer in comparison with an inductively coupled plasma optical emission spectroscopy (ICP-OES). The results of the two analytical techniques are compared and advantages and drawbacks emphasized. The TXRF analytical technique appears a reliable, economic, rapid and simpler technique for the everyday monitoring of the composition of the landfill leachate before the purification treatment and after the treatment to check the quality of the resulting purified water. The TXRF and the ICP-OES analytical techniques were also employed in the analysis of three groundwater samples.

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Abstract  

A landfill leachate sample was radiolyzed with γ-rays at 12.5, 25, 50, 100, 200 and 400 kGy. The radiolyzed solutions were studied by UV–VIS–NIR spectroscopy to measure the color change, by chemical oxygen demand (COD) analysis to check the degree of mineralization of the soluble organic matter present in the leachate and by FT–IR spectroscopy of the humic substance of the leachate. The results have shown that the humic substance present in the landfill leachate is extremely refractory to radiolysis: even at 400 kGy it was detected and recovered only with minor changes. It is shown that the radiolysis followed by ozonolysis is able to cause important improvements of the leachate color and important reduction on the COD. However, the results in terms of bleaching and COD abatement after radiolysis and ozonolysis of the leachate can be achieved directly by a simple exhaustive ozonolysis of the leachate. The structural changes occurring in the humic substances and in the humic acids present in the leachate after radiolysis and ozonolysis were analyzed by FT–IR spectroscopy.

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Abstract  

Fullerene/silica hybrid materials were obtained by radiation grafting on silica surface of toluene or decalin solutions of C60. As determined by thermogravimetric analysis, the amount of C60 grafted on silica surface was dependent from the radiation dose administered and independent from the C60 concentration and the nature of the organic solvent. In absence of air, a dose of 48 kGy was sufficient to ensure a grafting level of 30% by weight of C60 in the hybrid material. The fullerene/silica hybrid material shows a remarkable thermal stability, since the early decomposition starts above 300 °C as measured by DTG and DTA. The chemical structure of the fullerene/silica hybrid material was determined by FT-IR spectroscopy and with solid state 13C CP-MAS NMR. The potential application of such materials has been outlined.

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Abstract  

The sulphur-containing proteinaceous amino acids l-cysteine, l-cystine and l-methionine were irradiated in the solid state to a dose of 3.2 MGy. This dose corresponds to that delivered by radionuclide decay in a timescale of 1.05 × 109 years to the organic matter buried at a depth >20 m in comets and asteroids. The purity of the sulphur-containing amino acids was studied by differential scanning calorimetry (DSC) before and after the solid state radiolysis and the preservation of the chirality after the radiolysis was studied by chirooptical methods (optical rotatory dispersion, ORD) and by FT-IR spectroscopy. Although the high radiation dose of 3.2 MGy delivered, all the amino acids studied show a high radiation resistance. The best radiation resistance was offered by l-cysteine. The radiolysis of l-cysteine leads to the formation of l-cystine. The radiation resistance of l-methionine is not at the level of l-cysteine but also l-methionine is able to survive the dose of 3.2 MGy. Furthermore in all cases examined the preservation of chirality after radiolysis was clearly observed by the ORD spectroscopy although a certain level of radioracemization was measured in all cases. The radioracemization is minimal in the case of l-cysteine and is more pronounced in the case of l-methionine. In conclusion, the study shows that the sulphur-containing amino acids can survive for 1.05 × 109 years and, after extrapolation of the data, even to the age of the Solar System i.e. to 4.6 × 109 years.

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Abstract  

The thermal behaviour of 21 proteinaceous l-amino acids either as pristine samples and also as radiolyzed (3.2 MGy) samples was studied with the differential scanning calorimeter. The onset and peak melting point as well as the melting enthalpy of all samples before and after the radiation treatment was measured and reported. The residual amount of each amino acid survived to the radiation dose of 3.2 MGy (N γ) was measured from the melting enthalpies before and after radiolysis and hence the radiation resistance of each amino acid has been determined. The radiolysis causes a systematic reduction of the melting enthalpy and a shift of the onset and peak melting point to lower values. It is shown that N γ does not correlate with the melting points of the amino acids but shows a correlation with the entity of the shift of the melting point peaks occurred after radiolysis. Such correlation instead does not exist between the N γ parameter and the onset melting points of the amino acids. An explanation of such lack of correlation was given. Furthermore, a general relationship has been found between the amino acids melting point peak measured on pristine samples and the melting point peaks after solid state radiolysis. Such relationship can be used to predict roughly the expected melting point after radiolysis at 3.2 MGy of any given amino acid. The last part of the study was dedicated in the attempt to find a correlation between the N γ parameter and the amount of the amino acids survived the radiolysis R γ as measured by spectropolarimetry (ORD spectroscopy). A general trend was found in the connection between the N γ and R γ parameters but not a very strong correlation.

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