Jacques Yvon

FTIR reflectance vs. EPR studies of structural iron in kaolinites

The substitution of Fe3+ in the kaolinite structure is studied by EPR spectrometry and by FTIR spectrometry on a large set of kaolins from different origins (sedimentary and primary ores, soil kaolins). The IR bands at 3598 and 875 cm−1, observed in the literature only in the case of disordered kaolins or in Fe-rich environments (synthetic, lateritic), are revealed by high-resolution IR analysis, whatever the origin and the total Fe content of the samples. The EPR bands corresponding to Fe3+ substituted in sites II of the octahedral sheet increase when the IR absorbance near 3600 cm−1 increases. Two IR absorption bands near 4465 cm−1 and 7025 cm−1 are observed for the first time, both in transmission and diffuse reflectance on all samples. These bands are assigned to the combination of the 3598 and 875 cm−1 bands and to the first harmonic of the band at 3598 cm−1, respectively. The area of the band at 4465 cm−1 in diffuse reflectance is quantitatively correlated to the abundance of Fe3+ located in centers II as measured by ESR. This directly confirms the assignment of the two IR bands at 3598 and 875 cm−1 to OH stretching and deformation vibration bands in octahedral FE3+ environment in the kaolinite structure, respectively. Effects due to the size of particles and to the main kaolins impurities on the near infrared spectra, are also discussed.

Thermal properties of clay pastes for pelotherapy

Abstract Pelotherapy is the local or generalized application of thermal muds called peloids. Nowadays, the primary reserves of peloids have been exhausted around the thermal springs, so the hydropathic establishments have difficulties in obtaining supplies. Their most important property derives from the fact that muds can maintain a temperature of 50°C and therefore a great number of calories diffuse through the skin. In the present work, this thermal quality was estimated by two tests, (a) the measurement of specific heat (Cp) and (b) the cooling kinetics of artificial mineral pastes. The water content of the pastes, their composition and the nature of their clay mineral phase are the factors which determine their thermal properties; we advise the use of montmorillonites, which have a higher swelling capacity, for pelotherapic practices.

Ferric chloride and lime conditioning of activated sludges: an electron microscopic study on resin-embedded samples.

Ferric chloride and lime conditioning of sewage sludge is usually interpreted in terms of enhanced aggregation of sludge components. In this study, transmission electron microscopy was used to investigate the conditioning mechanism at a submicronic scale. Samples were collected from two municipal wastewater treatment plants at different stages of the process, embedded in an epoxy resin, and sectioned with an ultramicrotome. Transmission electron microscopy examination of thin sections revealed that clumps of crystalloids develop on external surfaces of flocs after the application of both conditioners. This precipitate creates a rigid structure around the flocs which, upon mechanical dewatering, transmits the stresses applied to the inner parts of flocs. The porous structure of the precipitate may also participate to the withdrawal of water as a draining media. Energy dispersive X-ray spectroscopy revealed that Fe, P, and Ca are the dominant elements in the precipitate with Fe/P and Fe/Ca elemental ratios close to 2.8-3 and 1.1-3, respectively.

EVOLUTION OF THE POROUS STRUCTURE AND SURFACE AREA OF PALYGORSKITE UNDER VACUUM THERMAL TREATMENT

The modification of the external surface area and the two types of microporosity of palygorskite (structural and interfiber porosity) were examined as a function of the temperature of a vacuum thermal treatment to 500°C. The methods used included: controlled-transformation-rate thermal analysis, N2 and Ar low-temperature adsorption microcalorimetry, conventional and continuous gas-adsorption volumetry (for N2 and Ar) at 77 K and CO2 at 273 and 293 K, water vapor adsorption gravimetry, and immersion microcalorimetry in water. At temperatures < 100°C only 18% of the structural microporosity was available to N2, 13% to Ar, and 100% to CO2 at 273 K. In both experiments the channels filled at very low relative pressures. At temperatures between 70° and 130°C the structure folded, and the mineral transformed to anhydrous palygorskite, which showed no structural microporosity. The interfiber microporosity was found to be independent of the temperature treatment, and the external surface area decreased slightly from 65 to 54 m2/g. The water adsorption isotherms showed that the folding of the structure was reversible up to final outgassing temperatures >225°C.

Occurrence of eight household micropollutants in urban wastewater and their fate in a wastewater treatment plant. Statistical evaluation

The occurrence in urban wastewater of eight micropollutants (erythromycin, ibuprofen, 4-nonylphenol (4-NP), ofloxacin, sucralose, triclosan, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS)) originating from household activities and their fate in a biological wastewater treatment plant (WWTP) were investigated. Their concentrations were assessed in the liquid and solid phases (sewage particulate matter and wasted activated sludge (WAS)) by liquid chromatography-tandem mass spectrometry. The analysis of sewage from two different urban catchments connected to the WWTP showed a specific use of ofloxacin in the mixed catchment due to the presence of a hospital, and higher concentrations of sucralose in the residential area. The WWTP process removed over 90% of ibuprofen and triclosan from wastewater, while only 25% of ofloxacin was eliminated. Erythromycin, sucralose and PFOA were not removed from wastewater, the influent and effluent concentrations remaining at about 0.7 μg/L, 3 μg/L and 10 ng/L respectively. The behavior of PFOS and 4-nonylphenol was singular, as concentrations were higher at the WWTP outlet than at its inlet. This was probably related to the degradation of some of their precursors (such as alkylphenol ethoxylates and polyfluorinated compounds resulting in 4-NP and PFOS, respectively) during biological treatment. 4-NP, ofloxacin, triclosan and perfluorinated compounds were found adsorbed on WAS (from 5 ng/kg for PFOA to 1.0mg/kg for triclosan). The statistical methods (principal component analysis and multiple linear regressions) were applied to examine relationships among the concentrations of micropollutants and macropollutants (COD, ammonium, turbidity) entering and leaving the WWTP. A strong relationship with ammonium indicated that some micropollutants enter wastewater via human urine. A statistical analysis of WWTP operation gave a model for estimating micropollutant output from the WWTP based on a measurement of macropollution parameters.

Chemical surface modifications of sulphide minerals after comminution

Abstract The superficial chemical heterogeneity of sulphide minerals can be natural or induced. Comminution is one possible way for changing, sometimes drastically, the surface state of sulphides, which, consequently, modifies the reactivity of the divided solid. Using different investigation techniques at the molecular scale, the chemical nature of the surface of galena, pyrite, chalcopyrite and sphalerite after various comminution conditions can be precisely described. Galena and pyrite are partially covered with piles of oxidized sulphates and carbonates species. Elemental sulfur was also revealed in variable amounts. After wet grinding, the chalcopyrite surface is altered by the formation of a continuous 200-nm-thick layer iron oxy-hydroxides. Xanthate molecules can be used as molecular probes for describing the surface of ZnS after wet grinding.

Chapter 11. Static and dynamic studies of the energetic surface heterogeneity of clay minerals

Publisher Summary Clay minerals are typical examples of heterogeneous adsorbents, showing both surface geometric and energy distributions. The heterogeneity of clays is governed by the geochemical crystallisation conditions, generating a strong relationship between the structure, shape and chemical surface properties of these solids. Such complexity obliges to develop the modern experimental techniques and modeling methods for studying solid surfaces. In this way, the high resolution low pressure quasiequilibrium adsorption technique, first developed to characterize geometrical heterogeneity of clay minerals, looks very powerful and promising for studying their energetic heterogeneity. Furthermore, the possibility to detect very high energy surface sites opens new investigation fields as those sites are always involved in interfacial interactions.

DEVELOPMENT OF MICROPOROSITY IN CLINOCHLORE UPON HEATING

The “modified chlorite structure” forms by the dehydroxylation of the interlayer octahedral sheet of magnesian chlorite at around 500°C and results in a structure with a basal spacing near 27 Â (Brindley and Chang 1974). This process involves drastic textural modifications as indicated by gas adsorption experiments which reveal the formation of structural micropores. Infrared spectroscopy as well as thermogravimetry and mass spectrometric analysis show that these micropores are filled with molecular atmospheric water, carbon dioxide, nitrogen, argon and hydrocarbons which condense once the samples cool down. A high temperature treatment is needed in order to release the different phases. A heterogeneous dehydroxylation mechanism is proposed in which micropores are formed in donor regions and magnesium and oxygen are concentrated in acceptor regions. This leads to a 27 Å structure with micropore zones and enriched interlayer oxide zones alternating along the z-axis of the mineral.

A combined approach for a better understanding of wastewater treatment plants operation: Statistical analysis of monitoring database and sludge physico-chemical characterization

Biological wastewater treatment plants (WWTP) are complex systems to assess. Many parameters are recorded daily in WWTP to monitor and control the treatment process, providing huge amounts of registered data. A combined approach of extracting information from the WWTP databases by statistical methods and from the sludge physico-chemical characterization was used here for a better understanding of the WWTP operation. The monitored parameters were analysed by multivariate statistical methods: Principal Components Analysis and multiple partial linear regression. The WWTP operational conditions determine the sludge characteristics. The bacterial activity of the sludge in terms of extra-cellular polymeric substances (EPS) production was assessed using size exclusion chromatography and the internal structure of sludge flocs was observed by confocal laser scanning microscopy. The diagnosis of three paper mill WWTP enabled the identification of an important EPS production, the presence of the nitrification process and the presence of PO(4)(3-) nutrient in WWTP-A. These three main characteristics of WWTP-A were related with a systematically good sludge settling. In WWTP-B and C with bad settling, the bacterial activity was weak.

Surface heterogeneity of kanemite, magadiite and kenyaite: a high-resolution gas adsorption study

Abstract The surface properties of various synthetic layered silicates, Na-kanemite, Nakenyaite and magadiite, exchanged with H, K and Ca, were examined using high-resolution nitrogen and argon adsorption and the data were treated using the Derivative Isotherm Summation method. Using argon as an adsorbate, the aspect ratio of platelets can be determined. In the case of magadiite exchanged with various cations, the stacking of particles is influenced by the nature of the exchangeable cations, thicker platelets being observed for ions with low polarizability. Highresolution argon adsorption data also confirm some structural information previously deduced from Raman spectroscopy experiments concerning the existence of rather open six-membered rings at the surfaces of both magadiite and kenyaite. Furthermore, in the low-energy domain of the isotherms, argon forms a very organized film on basal planes, suggesting a commensurate relationship between silica framework and argon atoms for both magadiite and kenyaite, contrary to what is observed for kanemite. Nitrogen adsorption results reveal the presence of polar sites on the surface of all the investigated minerals but does not allow us to propose an unequivocal assignment for such sites.