Joël Suptil

Use of diffuse reflectance spectrometry in spot test reactions for quantitative determination of cations in water

Diffuse reflectance spectroscopy can be successfully used for the quantitative determination of small amounts of pollutants like metals. The remission function was found to be linearly proportional to the concentration, when we applied the Kubelka-Munk equation. The color reactions of Cu(II), Co(II), and Ni(II) with dithiooxamide, were realised on filter paper. Reaction between Fe(III) and ammonium thiocyanate was realized on filter paper and gelatine matrix. All measurements were accomplished with a laboratory-constructed reflectometer. We have obtained a calibration curve by plotting the optical density of reflectance A(R) vs log of the mol l(-1) concentration. Limits of detection at the 10(-4) M level were estimated for all the compounds. Linear dynamic range extend over one order of magnitude and shows the potential of device for the quantitative analysis of environmental pollutants.

Ultrasound and ionic liquid: An efficient combination to tune the mechanism of alkenes epoxidation

In this proof of concept study, the advantageous properties of both H(2)O(2)/NaHCO(3)/imidazole/Mn(TPP)OAc oxidation system and MOPyrroNTf(2) ionic liquid have been combined under ultrasonic irradiation to give an exceptionally favorable environment for Mn(TPP)OAc catalyzed olefin oxidations. The results reveal the crucial role played by the ultrasonic irradiations that influence drastically the oxidation process. In MOPyrroNTf(2) and under ultrasonic irradiation, the mechanism probably involves an oxo-manganyl intermediate at the expense of the classical bicarbonate-activated peroxide route.

Sonochemical efficiency dependence on liquid height and frequency in an improved sonochemical reactor

The aim of this study was to evaluate the effects of liquid height and frequency on sonochemical efficiency of a cup-horn sonoreactor. The selected frequencies (22, 371, 504 kHz) and liquid height (29-348 mm) were applied while measuring acoustic yield, I(3)(-) formation rate and the resulting sonochemical efficiency. The frequency effect was shown to be coupled to liquid height effect. Indeed, acoustic zones (i.e. Fresnel and Fraunhöfer zones), which limits depends on both transducer diameter and frequency, significantly determine the production of radicalar species quantified by I(3)(-) formation rate. An increase of ultrasonic frequency results in lower acoustic yield and higher sonochemical efficiency. Theoretical physical and chemical effects attributed to collapsing bubbles were considered. Sonochemical efficiencies obtained at 500 kHz were similar or higher than those at 371 kHz, depending on liquid height. The effect of reactor configuration was further investigated as an hypothesis to explain unsignificant effect of standing waves in our study. Therefore, the dependence of sonochemical efficiency with liquid height might be firstly attributed to reactor configuration prior to frequency effects.

Sonochemical and sonocatalytic degradation of monolinuron in water.

The degradation of the phenylurea monolinuron (MLN) by ultrasound irradiation alone and in the presence of TiO(2) was investigated in aqueous solution. The experiments were carried out at low and high frequency (20 and 800 kHz) in complete darkness. The degradation of MLN by ultrasounds occurred mainly by a radical pathway, as shown the inhibitory effect of adding tert-butanol and bicarbonate ions to scavenge hydroxyl radicals. However, CO(3)(-) radicals were formed with bicarbonate and reacted in turn with MLN. In this study, the degradation rate of MLN and the rate constant of H(2)O(2) formation were used to evaluate the oxidative sonochemical efficiency. It was shown that ultrasound efficiency was improved in the presence of nanoparticles of TiO(2) and SiO(2) only at 20 kHz. These particles provide nucleation sites for cavitation bubbles at their surface, leading to an increase in the number of bubbles when the liquid is irradiated by ultrasound, thereby enhancing sonochemical reaction yield. In the case of TiO(2), sonochemical efficiency was found to be greater than with SiO(2) for the same mass introduced. In addition to the increase in the number of cavitation bubbles, activated species may be formed at the TiO(2) surface that promote the formation of H(2)O(2) and the decomposition of MLN.

Realisation d'un dispositif experimental pour le dosage des hydrocarbures aromatiques polycycliques par spectrofluorimetrie shpol'skii a 10 K

Abstract (An experimental device for determination of polynuclear aromatic hydrocarbons by Shpolskii spectrofluorimetry at 10 K.) An experimental device is described comprising a triple-stage cell and a fast heat excharger, so as to optimise the spectrofluorimetric determination of polynuclear aromatic hydrocarbons in polycrystalline octane matrices at 10 K. The temperature difference between the two end compartments of the cell, 0.8 K, is not sufficient to change the Shpolskii spectra. The fast heat exchanger allows quick crystallisation and reheating of the samples. This device is used for the identification and determination of the limits of detection for ten such compounds, including the compounds defined by the European Economic Community for drinking water standards. An example of direct assay for each substance in a mixture is given.

Diode-array ultraviolet detector for continuous monitoring of water quality

Abstract UV spectrometry was applied to the continuous monitoring of water quality, allowing the direct determination of specific components in natural waters and treated waste waters and the determination of oxidizable material in natural and waste waters. A diode-array UV detector with an auto-cleaning cell and sample line was developed. The processing of the absorption spectrum and the control of the whole system ae performed with a computer. A description and the characteristics and performance of the device are presented. Results are given for an automatic survey of waste-water quality (oxidizable material concentration) of a 300 000 eq. inhab. treatment plant.

Bicarbonate Effect in the Ozone-UV Process in the Presence of Nitrate

Ozonation and advanced oxidation processes (AOP) are very efficient methods for the destruction of refractory organic matters. These virtues have always been related to the production of hydroxyl radicals HO•, which are extremely powerful and non-selective oxidants. In this study, the O3-UV process is used as an AOP, where hydroxyl radicals are generated from the photodecomposition of ozone by short wavelength ultraviolet radiation. The obtained results indicated a weak scavenging effect of tert-butanol proving that hydroxyl radicals and ozone are not the only oxidants existing in the medium. Moreover, bicarbonate, known for a long time as effective HO• radical scavengers, does not slow down the oxidation of benzoic acid, but surprisingly increases it. Chlorides significantly decrease the degradation of organic compounds through their reaction with HO• radicals to produce chlorine. Carbonate radicals, nitrate and nitrogenated species as peroxynitrite/ peroxynitrous acid are involved in the oxidative mechanisms.

A Data Acquisition and Processing Software for High-Resolution Shpol'Skii Spectrofluorometry

Abstract This study describes a software called “HAP”, realized in our laboratory for rapid data acquisition and processing on a high-resolution low-temperature spectrofluorometer. The main characteristics of the setup developed and the utilities offered by “HAP” will contribute to a routine analysis of hydrocarbon traces and prove the great analytical capability of this luminescence method. Using this new computerized system six parent priority PAHs in sediment and natural water samples from an alpine river near Annecy (France) have been determined.