Murielle Rabiller-Baudry

Treatment of dairy process waters by membrane operations for water reuse and milk constituents concentration

Abstract In the dairy industry non-accidental losses of milk or dairy products to sewer amount to 1–3% of the total milk processed. These significantly contribute to the 0.5–6.0 g COD/L of end-of-pipe wastewater. The major part of this polluting charge originates from starting, interrupting, and stopping dairy plant procedures, where milk-products are diluted with water and discharged to a purification station or collected to be spread on land. The very few works, that have been dedicated to the treatment of the so-called process waters (flushing waters, first rinse waters or “white waters”), show that nanofiltration (NF) or reverse osmosis (RO) is adequate for the concentration of milk components. The present work reports NF and RO performances (permeate flux, milk components rejection) of an effluent model solution (diluted skimmed milk). Performances of eight NF and RO membranes were compared by dead-end filtration. Crossflow experiments with NF and RO spiral-wound membranes confirm the results obtained by dead-end filtration. The results showed that one single membrane operation allowed the milk constituents to be concentrated in the retentate but reusable water of composition complying with the standard of purified water from process water was not reached. A finishing step (RO membrane, other) is needed for the production of reusable water.

Physico-chemical characterization of proteins by capillary electrophoresis

The electrophoretic mobility of proteins was successfully determined by means of capillary electrophoresis (CE) with various background electrolytes (BGEs). The objective was focused on the variation in BGE physico-chemical composition and the consequential impact on the observed protein charge. Experimental and calculated mobilities, according to Henrys equation, versus ionic strength have been compared. For positively-charged lysozyme, a good agreement between observed and calculated mobilities was observed using triethanolamine chloride at pH 7.0 as the BGE. Mobility close to zero was shown using borate (pH 8.0) and phosphate (pH 7.0) at a low ionic strength of about 20 mmol l(-1), and as a consequence, specific adsorption of oxyanions was evidenced. Lysozyme retention in the case of reversed-phase high-performance liquid chromatography (RP-HPLC) was decreased by the presence of phosphate ions. CE and HPLC are complementary tools for characterizing the behaviour of lysozyme. On the other hand, the mobility of the negatively-charged alpha-lactalbumin remained constant as regards phosphate at pH 7.0 in the 20-200 mmol l(-1) range, contrary to the decrease that had been expected with the increasing ionic strength. beta-Lactoglobulin exhibited increasingly lower mobilities than those expected of boric acid/borate at pH 7.0 and 8.0 (I=20 mmol l(-1)).

Degradation of Poly(Ether Sulfone)/Polyvinylpyrrolidone Membranes by Sodium Hypochlorite: Insight from Advanced Electrokinetic Characterizations

Poly(ether sulfone) (PES)/polyvinylpyrrolidone (PVP) membranes are widely used in various industrial fields such as drinking water production and in the dairy industry. However, the use of oxidants to sanitize the processing equipment is known to impair the integrity and lifespan of polymer membranes. In this work we showed how thorough electrokinetic measurements can provide essential information regarding the mechanism of degradation of PES/PVP membranes by sodium hypochlorite. Tangential streaming current measurements were performed with ultrafiltration and nanofiltration PES/PVP membranes for various aging times. The electrokinetic characterization of membranes was complemented by FTIR-ATR spectroscopy. Results confirmed that sodium hypochlorite induces the degradation of both PES and PVP. This latter is easily oxidized by sodium hypochlorite, which leads to an increase in the negative charge density of the membrane due to the formation of carboxylic acid groups. The PVP was also found to be partly released from the membrane with aging time. Thanks to the advanced electrokinetic characterization implemented in this work it was possible for the first time to demonstrate that two different mechanisms are involved in the degradation of PES. Phenol groups were first formed as a result of the oxidation of PES aromatic rings by substitution of hydrogen by hydroxyl radicals. For more severe aging conditions, this membrane degradation mechanism was followed by the formation of sulfonic acid functions, thus indicating a second degradation process through scission of PES chains.

Recent progress in Chevrel phase syntheses: A new low temperature synthesis of the superconducting lead compound

This paper reviews recent progress in the synthesis of Chevrel phases. The objective was to produce better microscopic homogeneity of the elements and/or precursors required to form the phase. Among these new processes, the one dealing with insertion of lead into the binary Mo6S8 compound is particularly attractive for the development of Chevrel phase wire since the phase formation occurs at temperature as low as 440°C. To achieve good microscopic homogeneity of PbMo6S8 (PMS), PbS is used and the extra sulfur is removed under a hydrogen gas flow. Basic superconducting properties, like a.c. susceptibility transition and specific heat anomaly at Tc, demonstrate extremely fine super-conducting particles. Further annealing at the moderate temperature of 600°C improves the homogeneity and/or the crystallinity of the powder.

Convenient syntheses of chevrel phase compounds from soluble sulfide precursors under flowing hydrogen atmosphere

Abstract New methods to synthesize Chevrel phases compounds have been performed. The starting materials can be mixture of polythiomolybdates and salts of metal (copper, lead). In all cases, the intermediate of the reaction is a mixture of molybdenum disulfide and the appropriate metal. Then, these bulky syntheses are used as model in order to synthesize Chevrel phases supported on alumina. So, for the first time, we prepare such supported compounds, that will probably find application in heterogeneous catalysis reactions.

Capillary electrophoretic analysis of anions in a multi-anion background electrolyte: Interference of system peaks

SummaryThis study deals with the simultaneous analysis of UV-transparent anions by capillary electrophoresis with indirect UV-detection. With a background electrolyte (BGE) based on UV-absorbing chromate and UV-transparent borate, the interference of system peaks with those of sample anions (chloride, sulfate, citrate, phosphate) is shown. The existence of such system peaks, and their position in relation to the peaks of the sample anions, are explained on the basis of the eigenpeak theory proposed by Poppe [1]. With this BGE the system peaks were manifested as a negative peak followed by a positive peak. Their shapes depended on the relative mobilities of the analyte and BGE anions and their areas depended on the amount of sample. The mobility of the system peak depends on the borate/boric acid mobility, which was adjusted by slight variation of the pH close to its pKa-pH is the key factor governing system-peak mobility. When the locations of the system peaks are optimized, the quantification of citrate can be achieved; this was successfully used for determination of anions in milk.

Syntheses of bulk and supported Chevrel phases

Abstract Bulk Chevrel phases exhibit interesting performances as catalysts in hydrotreating reactions. However, in such catalysis reactions, supported materials are commonly used. Thus, for the first time a copper Chevrel phase supported on alumina has been prepared. The paper is divided into two parts. The first part deals with new bulk syntheses that had to be developed in order to serve as model for the supported material preparation. The second part explains the process used to synthesize the supported material. The EXAFS technique allows identification of this material.