Ph. de Donato

Spatial distribution of iron and sulphur species on the surface of pyrite

Abstract XPS, DRIFTS, UV spectroscopy and HPLC were used to investigate the nature and spatial distribution of oxidized superficial phases present on pyrite surfaces. Two pure pyrites with different arsenic contents were used. The surface of the first sample (As=0.018%) is covered with an important three-dimensional heterogeneous oxidized phase (Fe2(SO4)3, Fe(OH)3, FeO) in equilibrium with two two-dimensional phases (metastable polysulphide (S5S2-) and elemental sulphur (S8)). The superficial phases present at the surface of the second pyrite (As=0.309%) have the same composition. However, their extension is mainly two-dimensional with lower amounts of polysulphide (S5S2-) and elemental sulphur.

Separation of hydrocarbons and lipid from water using treated bark

This paper explores the possibility of using treated bark to remove oily compounds from water. Bark was first biologically or chemically treated and saturated with transition metal ions (TMI) to avoid the release of soluble organic compounds from the bark in the treated effluents. Several experimental parameters affecting the oil removal efficiency (RE) were studied (initial oil concentration, temperature, time, etc.). Saturated bark was characterized using Fourier transform infrared (FTIR) spectroscopy and bark wetting index was determined. Results of the retention of lipids suggested that their removal could exceed 95% of initial oil concentration. The uptake of lipid by treated bark varied from 0.2 to 2.0 g of organic oil/g of dry sorbent. No significant chemical modifications of saturated bark were observed in infrared spectroscopy after the sorption of oleic acid on bark treated with transition metal ions. The structure of adsorbed tridimensional layer of oleic acid molecules seemed to take place through the double bond. The hydrocarbon RE exceeded 95% using oil-water mixture with a hydrocarbon/bark ratio of one. The sorption reaction of hydrocarbons and lipids was quasi-instantaneous and seemed to be influenced by the temperature. This indicated that the retention mechanism was related to the capillary action. Results of FTIR spectroscopy suggested that no chemical bonds between barks and oily compounds were established.

Interpretation of the luminescence quenching in chemically etched porous silicon by the desorption of SiH3 species

The effect of thermal annealing on chemically etched porous silicon was studied by combined photoluminescence, infrared spectrometry, and thermal‐desorption spectrometry experiments. The results show that the release of SiH3 and SiF3 entities is a first step in the photoluminescence degradation in porous silicon. These entities desorb before molecular hydrogen.

Effect of cytostatic drug presence on extracellular polymeric substances formation in municipal wastewater treated by membrane bioreactor

The effect of the cyclophosphamide and its mean metabolites on extracellular polymeric substances (EPS) formation was investigated. Two lab-scale membrane bioreactors were followed in parallel (one with the cytostatic drugs, the second without). Chromatographic and spectroscopic studies (UV-Vis spectroscopy and IR spectroscopy) showed that the presence of CPs induced an increase in EPS concentration in the biological sludge, especially of soluble substances, mainly polysaccharides and proteins. Size exclusion chromatography analysis revealed that in the presence of CPs, macromolecular EPS were formed (polysaccharides corresponding to about 6 KDa and proteins to about 18 KDa). The formation of EPS seemed to be a protection mechanism. More important membrane fouling in reactor with CPs seemed to be related to the retention of an increased amount of soluble substances.

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.

Natural oxidation of annealed chemically etched porous silicon

Abstract Thermal annealing of porous silicon at 400 and 450 °C leads to the desorption of hydrogen from the SiH 2 sites and to the quenching of the photoluminescence. After exposure for 2 months to ambient air at 300 K, the photoluminescence is restored and becomes more intense than that of the as-etched sample. IR spectrometry and thermal desorption spectrometry show that it is the result of the passivation of the porous silicon surfaces by oxygen and water vapor.

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.

Activated sludge behaviour in a batch reactor in the presence of antibiotics: study of extracellular polymeric substances

The influence of Erythromycin, Roxithromycin, Amoxicillin, Tetracycline and Sulfamethoxazole on municipal sludge in batch reactors was investigated. The study was focused on extracellular polymeric substances (EPS) as indicator of bacteria sensitivity to toxic agents. The EPS were analysed by UV-Vis and FT-IR spectroscopies and by size exclusion chromatography. It was found that Erythromycin and Roxithromycin induced a significant increase of bound EPS in flocs. This was attributed to a protection mechanism of the bacteria. Erythromycin was the only antibiotic which inhibited COD and nitrogen removal.

The pitfalls of protein quantification in wastewater treatment studies.

Proteins, as one of the principal components of organic matter in wastewater, require adequate quantification to determine their concentration in the different stages of wastewater treatment process. Recent studies have used the corrected Lowry Method for protein quantification arguing that this method can differentiate proteins from interfering humic substances. In this study, the classic Lowry Method, the corrected Lowry Method and a commercial assay kit were assessed for the protein quantification in the presence of humic acid.

Physicochemical characterisation of the lactoperoxidase system powders: comparison of two drying techniques

A good knowledge of powder flow properties is necessary to consider industrial application of a system. Flowability is a complex combination of different parameters like size, shape or surface properties of particles. The goal of this study is to compare the impact of two drying techniques (freeze-drying and spray drying) on powder flowability in order to choose the most appropriate device. Powder is first studied at the particle level with size measurements and shape description. Then, the global behaviour is characterised by water content, water up-take and physicochemical analysis. Finally, the influences of two additives and of coating on powder flow properties have been investigated. The two powders obtained by spray and freeze-drying vary principally by the shape of the particles. Residual water content, moisturising capacity and surface properties are similar. In both cases, powder flowability is bad. Results obtained with the two additives show no improvement of powder flow properties. However, coating reduces the number of fine particles and, as a consequence, improves powder flowability with furthering particle motion.