Study and design of an optode for pH measurement

International audienceThe GraftFast® process is a simple ant quick method to covalently graft a chemical on a substrate, provided that the chemical has an aromatic primary amine. Thus, this method is studied for an application in pH measurement via an optode. The aim of this PhD work, which started in October 2012, is to covalently graft a dye sensible to pH variations on an optical fiber, so as to be able to solve the stability issues encountered with other techniques used to assemble the dye and the optical fiber – like physical entrapment or electrostatic interactions. The work presented here explains the concept of an optode and the GraftFast® process. The first results obtained show the two dyes that will be studied, and that one ot those potential dyes, the neutral red, can be quite efficiently grafted on a gold substrate

Study of the grafting of dyes for the design of a pH optode

International audienceSo as to covalently graft a chemical on a substrate, the GraftFastTM process can be used; the only requirement is that the chemical has at least one aromatic primary amine. In this work, this simple and fast process is presently used to graft dyes that are pH sensitive on an optical fiber, thus creating a pH sensor called optode. The major asset of this grafting process is that the dye is covalently grafted on the fiber, resolving stability issues encountered with other techniques – like physical entrapment or electrostatic interactions. Two different dyes have been successfully grafted on gold lamellas (which are the reference substrates for the GraftFastTM process), and an innovative experimental method to increase the thickness of the dye layer has been developed

Development of an optical pH probe for monitoring the Cigeo storage site.

International audienceIn France, the reversible deep geological repository, which would be located on the border of the Haute-Marne and de la Meuse aims to provide a definitive solution to the problem posed by the most radioactive waste produced mainly by the nuclear industries. This storage center called Cigeo (Industrial Center for geological storage of waste), will be operated over a secular period, it is important to enrich knowledge on the environmental monitoring of this storage center. The objective of the work is to develop a robust optical probe dedicated to the measurement of the pH of the poral water from the clay rock at the alveoli intended to receive packages of nuclear waste. The idea is to develop a robust optical probe to measure pH in situ, online and especially offset measurement. The experimental device of this probe consists of a light source, a spectrometer, a data processing software, a mirror and optical fibers that carry the light information to the detector. According to the principle of this probe, a light source is connected to a multimode emission optical fiber that injects the light into it. The emission fiber carries the light to the place where the measurement is to be made. A mirror, constitutive of the optical chain returns the light in a multimode reception optical fiber to a spectrometer for analysis and then the computer is used to process spectral responses. To achieve this objective, electrografting by reducing the diazonium aryl salts of a coloured pH indicator is carried out either on the metallized optical fiber or on the metal mirror of the optical chain. The efficiency of this chemistry is based on the high reactivity of aryl radicals produced in situ under polarization of the surface of the metal substrate to be functionalized. As a result of grafting, covalent bonds are generated at the interface of the conductive substrate and the organic multilayer formed. For reasons of optimization of experimental parameters and characterization of functionalized surfaces, a glass slide was used to simulate the conductive substrate. After grafting, the glass slide is characterized by various spectrometric methods such as visible UV, ATR Infra-Red, XPS, profilometry

Rétention d’espèces Volatiles d'iode Par Les Charbons Actifs Imprégnés

International audienceThe efficient capture of volatile iodine species (I2, CH3I) potentially released from nuclear facilities is a major issue to improve the nuclear safety. In that respect, activated carbons (AC) have been used for the removal of iodine within ventilation networks of nuclear facilities. More particularly, the commonly used nuclear grade AC are co-impregnated with potassium iodide (KI, 1 wt%) and triethylenediamine (TEDA, < 5 wt%) [1]. However, uncertainties remain about the contribution of the involved retention mechanisms (more particularly, the isotopic exchange for KI-impregnated AC). Hence, the present study aims to gain insights into the importance of this reaction as a comparison with other adsorption mechanisms (physisorption and chemisorption). A specific methodology has been implemented (Fig. 1 (A)). In a first part, the behavior of characterized AC towards the retention of methyl iodide under a large panel of configurations (Fig. 1 (A)) was explored. Preliminary experiments using standardized test methodologies for nuclear grade AC have shown the importance of isotopic exchange phenomenon for the capture of γ-labeled CH3I under humid conditions (T = 20°C, R.H. = 90%, Fig. 1 (B)). The quantification of this reaction has to be assessed by comparing the breakthrough curves obtained in both cases (radioactive and not-radioactive CH3I). Accordingly, a test bench is under development and validation. This talk will describe the used strategies to obtain the first data relevant to the quantification of isotopic exchange phenomena. More precisely, the methodologies, the different test benches as well as the first results showing the importance of this phenomena in the retention of radioactive iodine will be presented

Rétention d’espèces Volatiles d'iode Par Les Charbons Actifs Imprégnés

International audienceThe efficient capture of volatile iodine species (I2, CH3I) potentially released from nuclear facilities is a major issue to improve the nuclear safety. In that respect, activated carbons (AC) have been used for the removal of iodine within ventilation networks of nuclear facilities. More particularly, the commonly used nuclear grade AC are co-impregnated with potassium iodide (KI, 1 wt%) and triethylenediamine (TEDA, < 5 wt%) [1]. However, uncertainties remain about the contribution of the involved retention mechanisms (more particularly, the isotopic exchange for KI-impregnated AC). Hence, the present study aims to gain insights into the importance of this reaction as a comparison with other adsorption mechanisms (physisorption and chemisorption). A specific methodology has been implemented (Fig. 1 (A)). In a first part, the behavior of characterized AC towards the retention of methyl iodide under a large panel of configurations (Fig. 1 (A)) was explored. Preliminary experiments using standardized test methodologies for nuclear grade AC have shown the importance of isotopic exchange phenomenon for the capture of γ-labeled CH3I under humid conditions (T = 20°C, R.H. = 90%, Fig. 1 (B)). The quantification of this reaction has to be assessed by comparing the breakthrough curves obtained in both cases (radioactive and not-radioactive CH3I). Accordingly, a test bench is under development and validation. This talk will describe the used strategies to obtain the first data relevant to the quantification of isotopic exchange phenomena. More precisely, the methodologies, the different test benches as well as the first results showing the importance of this phenomena in the retention of radioactive iodine will be presented

Rétention d’espèces Volatiles d'iode Par Les Charbons Actifs Imprégnés

International audienceThe efficient capture of volatile iodine species (I2, CH3I) potentially released from nuclear facilities is a major issue to improve the nuclear safety. In that respect, activated carbons (AC) have been used for the removal of iodine within ventilation networks of nuclear facilities. More particularly, the commonly used nuclear grade AC are co-impregnated with potassium iodide (KI, 1 wt%) and triethylenediamine (TEDA, < 5 wt%) [1]. However, uncertainties remain about the contribution of the involved retention mechanisms (more particularly, the isotopic exchange for KI-impregnated AC). Hence, the present study aims to gain insights into the importance of this reaction as a comparison with other adsorption mechanisms (physisorption and chemisorption). A specific methodology has been implemented (Fig. 1 (A)). In a first part, the behavior of characterized AC towards the retention of methyl iodide under a large panel of configurations (Fig. 1 (A)) was explored. Preliminary experiments using standardized test methodologies for nuclear grade AC have shown the importance of isotopic exchange phenomenon for the capture of γ-labeled CH3I under humid conditions (T = 20°C, R.H. = 90%, Fig. 1 (B)). The quantification of this reaction has to be assessed by comparing the breakthrough curves obtained in both cases (radioactive and not-radioactive CH3I). Accordingly, a test bench is under development and validation. This talk will describe the used strategies to obtain the first data relevant to the quantification of isotopic exchange phenomena. More precisely, the methodologies, the different test benches as well as the first results showing the importance of this phenomena in the retention of radioactive iodine will be presented

Recent patents and industrial applications

International audienceIn this chapter, we will show how it is possible to modify the properties of material surfaces, thanks to the chemistry of aromatic diazonium salts applied to their functionalization. Overall, it is sufficient to play with the fragility of the C–N bond between the aromatic and the diazonium (–N2+ ) group. This bond breaks during a reduction reaction and leads to the formation of an extremely reactive aryl radical, which can react with a surface and form a covalently grafted coating by successive additions or initiate a radical polymerization reaction. This diazonium salt chemistry is simple, inexpensive, works in water and does not require energy input. It can be adapted to many substrates and is thus particularly suitable for industrial developments. We will see through the three following examples how to take advantage of these reactions to confer new properties to the surface of materials as varied as those encountered to biocompatibilize surgical implants (example 1), to make a robust optical sensor (example 2) or to treat light alloys for aeronautics (example 3)

Effect of activated carbons properties towards the capture of methyl iodide: first insights about the isotopic exchange contribution

International audienceTEDA and KI co-impregnated activated carbons (ACs) are widely used in the nuclear facilities to prevent volatile iodine species (namely CH3I) dissemination into the environment. However, some uncertainties still remain namely about the most influencing adsorbent parameters, as well as the involved adsorption mechanisms. In this talk, a specific attention will be devoted to better assess the influence of KI progressive impregnation on the obtained retention performances through different test methodologies and using various characterization techniques (XPS, SEM/EDS, N2 porosimetry, H2O porosimetry…). Different trends were obtained depending on the studied condition when considering CH3I retention efficiency as deduced from standardized protocols. A decrease of decontamination factors (DF) was observed as a function of KI content at R.H. = 40 % (Fig.1 (A)). This decrease was attributed to the enhancement of H2O interaction with activated carbons after KI impregnation. Therefore, the available microporosity for CH3I physisorption is reduced (Fig.1 (A)). At R.H. = 90%, the adsorption mechanism was found to be governed by isotopic exchange reaction, leading therefore to a slight DF increase after progressive KI incorporation. Better performances were nevertheless obtained after TEDA impregnation due to its high affinity with methyl iodide [1]. The beneficial effect of KI for CH3I removal was highlighted namely through breakthrough experiments performed towards γ-labelled and stable CH3I. Indeed, a progressive gain in adsorption capacities after KI incorporation until about 70% for 5%KI/AC, was evidenced (Fig. 1 (B))

Effect of activated carbons properties towards the capture of methyl iodide: first insights about the isotopic exchange contribution

International audienceTEDA and KI co-impregnated activated carbons (ACs) are widely used in the nuclear facilities to prevent volatile iodine species (namely CH3I) dissemination into the environment. However, some uncertainties still remain namely about the most influencing adsorbent parameters, as well as the involved adsorption mechanisms. In this talk, a specific attention will be devoted to better assess the influence of KI progressive impregnation on the obtained retention performances through different test methodologies and using various characterization techniques (XPS, SEM/EDS, N2 porosimetry, H2O porosimetry…). Different trends were obtained depending on the studied condition when considering CH3I retention efficiency as deduced from standardized protocols. A decrease of decontamination factors (DF) was observed as a function of KI content at R.H. = 40 % (Fig.1 (A)). This decrease was attributed to the enhancement of H2O interaction with activated carbons after KI impregnation. Therefore, the available microporosity for CH3I physisorption is reduced (Fig.1 (A)). At R.H. = 90%, the adsorption mechanism was found to be governed by isotopic exchange reaction, leading therefore to a slight DF increase after progressive KI incorporation. Better performances were nevertheless obtained after TEDA impregnation due to its high affinity with methyl iodide [1]. The beneficial effect of KI for CH3I removal was highlighted namely through breakthrough experiments performed towards γ-labelled and stable CH3I. Indeed, a progressive gain in adsorption capacities after KI incorporation until about 70% for 5%KI/AC, was evidenced (Fig. 1 (B))

Effect of activated carbons properties towards the capture of methyl iodide: first insights about the isotopic exchange contribution

International audienceTEDA and KI co-impregnated activated carbons (ACs) are widely used in the nuclear facilities to prevent volatile iodine species (namely CH3I) dissemination into the environment. However, some uncertainties still remain namely about the most influencing adsorbent parameters, as well as the involved adsorption mechanisms. In this talk, a specific attention will be devoted to better assess the influence of KI progressive impregnation on the obtained retention performances through different test methodologies and using various characterization techniques (XPS, SEM/EDS, N2 porosimetry, H2O porosimetry…). Different trends were obtained depending on the studied condition when considering CH3I retention efficiency as deduced from standardized protocols. A decrease of decontamination factors (DF) was observed as a function of KI content at R.H. = 40 % (Fig.1 (A)). This decrease was attributed to the enhancement of H2O interaction with activated carbons after KI impregnation. Therefore, the available microporosity for CH3I physisorption is reduced (Fig.1 (A)). At R.H. = 90%, the adsorption mechanism was found to be governed by isotopic exchange reaction, leading therefore to a slight DF increase after progressive KI incorporation. Better performances were nevertheless obtained after TEDA impregnation due to its high affinity with methyl iodide [1]. The beneficial effect of KI for CH3I removal was highlighted namely through breakthrough experiments performed towards γ-labelled and stable CH3I. Indeed, a progressive gain in adsorption capacities after KI incorporation until about 70% for 5%KI/AC, was evidenced (Fig. 1 (B))