Performance de la nanofiltration pour l'élimination de la matière organique naturelle: essais sur l'usine de Méry/Oise

L'intérêt croissant que les traiteurs d'eaux portent à l'élimination de la matière organique naturelle (MON) a abouti au développement de nouvelles technologies de traitement. Dans ce but, un prototype de nanofiltration à l'échelle industrielle (2 x 1400 m 3 j-¹) est installé à l'usine de Méry sur Oise depuis juillet 1992. Utilisé en traitement de finition après clarification et filtration sur sable, il alimente depuis février 1993 un réseau test de la commune d'Auvers sur Oise (6 000 hbts) en région parisienne.L'objectif de cette publication est de présenter quelques uns des résultats de caractérisation de la MON obtenus pendant 9 mois d'expérimentation (octobre 1992 à juillet 1993), et en particulier ceux concernant les rendements d'élimination de la matière organique naturelle et par voie de conséquence de la demande en chlore.Ces rendements sont généralement supérieurs à 90 % en termes de COD,CODB et d'absorbance UV à 254 et 270 nm éliminés. L'analyse des potentiels de réactivité avec le chlore (taux de chloration: 2,5 mg Cl2/mg C, temps de réaction: 72 heures, pH = 7,5, 20 °C) montre que le perméat est peu consommateur de chlore (demande en chlore < 0,2 mg l-¹ Cl2) et peu précurseur de chloroforme et de trihalométhanes (PFCHC13 < 3 µg l-¹, PFTHM < 11 µg l-¹). Les rendements d'élimination des PFTHM et PFTOX sont généralement supérieurs à 90 %.L'analyse spécifique des constituants majoritaires du perméat montre que les acides aminés totaux (hydrolyse acide puis dérivation à l'OPA/HPLC) constituent une proportion importante du COD (25 à 60 % selon les saisons). Ces composés représentent la quasi totalité de la demande en chlore du perméat si l'on se réfère aux données bibliographiques.Compte tenu de ces résultats, la nanofiltration apparaît comme un excellent procédé de traitement de finition des eaux à potabiliser. En effet, bien qu'elle constitue une barrière de sécurité contre les germes pathogènes, la très faible charge organique du perméat obtenu par nanofiltration (COD~0,15 à 0,3 mg l-¹ C, CODB<0,1 mg l-¹ C) rend plus aisée la maîtrise du résiduel de chlore (lorsqu'une chloration est nécessaire pour maintenir la qualité de l'eau dans les réseaux) et constitue une limitation importante de la formation des sous-produits de chloration.Increasing interest in removing natural organic matter (NOM) has lead to the development of new drinking water treatment technologies. Since July 1992, a nanofiltration demonstration plant (2 x 1400 m3 d-1) has been used to treat sandfiltered water from the Oise river. The permeate has been distributed since February 1993 to the 6000 inhabitants of Auvers/Oise in the Paris suburb. The purpose of this paper is to present and discuss some ofthe results obtained over nine months of operation of this full scale plant, particularly yields of NOM removal and consequently the decreasing of chlorine reactivity (chlorine demand, TTIM and TOX formation potentials).Dissolved organic carbon (DOC) and UV-absorbance were determined using DOC analyser and a spectrophotometer. Biodegradable dissolved organic carbon (BDOC), which represents the biologically assimilable portion of DOC, was determined using the method of JORET et LEVI (1986). Chlorine demand, trihalomethane and total organohalide formation potentials (THMFP and TOXFP) were carried out under the following experimental conditions: applied chlorine dose of 2.5 mg Cl2/mg DOC, pH = 7,5 72 h-contact time and 20°C. Ultrafiltration experiments involved the use ofa laboratory ultrafiltration cell, Total amino-acids were analysed by HPLC after hydrolysis and orthophtaldialdehyde (OPA) derivatization. Aldehyde and ketone determination was based on the method developedby GLAZE et al. (1989) involving pentafluorobenzyl hydroxyl amine (PFBHA) derivatization.Characterization of sand-filtered water (SFW): The sand-frltered water (SFW) upstream of the nanofiItraton membranes has a DOC between 2.4 and 4.l mg l-1, depending on the season (table 1). Its BDOC ranges from 0.7 to l.l mg l-1 C. In fact, a BDOC value higher than 0.3 mg l-1 C has been mentioned by several authors as the limit above which possible bacterial regrowth can take place in the distribution network.The chlorine consumption curves, shown in figure 2 for five sampling campaigns, indicate that the chlorine demand of the SFW can reach 3.4 to 5.2 mg l-1 depending on the season (table 2). The THMFP and the TOXFP are 108-149 ug l-1 and 344-446 ug l-1 Cl- respectively. Note that the ratio of chlorine demand over DOC varies from 1.0 to 1.7 mg Cl2/mg DOC while the THMFP/DOC and TOXFP/DOC ratios present average values of 47.5 ug/mg DOC and 160 ugCl-/mg DOC respectively.The distribution of the SFW (table 3) indicates that the fraction with apparent mo lecular weight Iess than 3 kilodatons contains the major compounds at this stage of the water treatment. This fraction presents the highest chlorine consumption. Specific total amino acids (TAA) analyses demonstrate that TAA represent 3 to 8% of the DOC of the sand-filtered water. The most abundant arnino acids are glycine, aspartic acid, glutamic acid, serine and alanine. The chlorine consumption attributed to these amino acids is evaluated as 1 mg l-1 Cl2, that is to say 1/5 to 1/3 of the SFW chlorine demand. Formaldehyde and acetaldehyde seem to be the major aldehydes present in the SFW with a level of 7 ug l-1 and 20 ug l-1 of formaldehyde and acetaldehyde respectively. They represent only about 0.5 to 0.6 % of the SFW DOC.Characterization of the permeate: The nanofiltration permeate presents a very low NOM level in terms of DOC, BDOC and UV absorbance at 270 nm, that is to say 0.14 to 0.34 mg l-1 C, < 0.1 mg l-1 C and < 0.006 cm-1-l respectively (table 6).The chlorine consumption curves, showt in figure 4 for five sampling campaigns, demonstrate the low permeate reactivity with chlorine. The chlorine demands (table 7) after 72 hours are between 0.12 and 0.32 mg l-1. Moreover chlorine demand/DOC ratios have a value from 0.46 to 0.93 mg Cl2/mg DOC, i.e. half the values measured for SFW. The THMFP and TOXFP (72hours) range from 7 to 11 ug l-1 and 26 to 31 ug l-1 Cl- respectively.Total amino acid (TAA) analyses showed that TAA represent 35 to 60% of the permeate DOC and can account almost entirely for the chlorine consumption. Formaldehyde and acetaldehyde (the major aldehydes analysed) represent 7 to 8% of the permeate DOC.According to the results presented in this paper, nanofiltration appears to be an excellent technolory as a polishing step in surface water treatment. Whereas the level of sand-fïltered water (SFW) DOC varies from 2.4 to 4.1 mg l-1 C (depending on the season), the permeate DOC is consistently lower than 0.3 mg l-1 C. The efficiency of nanofiltration is about 90% for DOC, BDOC and consequently for chlorine demand, THMFP and TOXFP. The high retention of NOM is probably in relation with the percentage (75%) of compounds with apparent molecular weight above 500 daltons in the SFW. In fact the low values of BDOC and chlorine demand justify the use of nanofiltration for the production of a water which represents a very low risk of bacterial regrowth and a low risk of formation of disinfection by product in the network when distributed with a low concentration of residual chlorine

Investigation of nanodispersion in polystyrene-montmorillonite nanocomposites by solid state NMR

Nanocomposites result from combinations of materials with vastly different properties in the nanometer scale. These materials exhibit many unique properties such as improved thermal stability, reduced flammability, and improved mechanical properties. Many of the properties associated with polymer–clay nanocomposites are a function of the extent of exfoliation of the individual clay sheets or the quality of the nanodispersion. This work demonstrates that solid-state NMR can be used to characterize, quantitatively, the nanodispersion of variously modified montmorillonite (MMT) clays in polystyrene (PS) matrices. The direct influence of the paramagnetic Fe3, embedded in the aluminosilicate layers of MMT, on polymer protons within about 1 nm from the clay surfaces creates relaxation sources, which, via spin diffusion, significantly shorten the overall proton longitudinal relaxation time (T1 H). Deoxygenated samples were used to avoid the particularly strong contribution to the T1 H of PS from paramagnetic molecular oxygen. We used T1 H as an indicator of the nanodispersion of the clay in PS. This approach correlated reasonably well with X-ray diffraction and transmission electron microscopy (TEM) data. A model for interpreting the saturation-recovery data is proposed such that two parameters relating to the dispersion can be extracted. The first parameter, f, is the fraction of the potentially available clay surface that has been transformed into polymer–clay interfaces. The second parameter is a relative measure of the homogeneity of the dispersion of these actual polymer–clay interfaces. Finally, a quick assay of T1 H is reported for samples equilibrated with atmospheric oxygen. Included are these samples as well as 28 PS/MMT nanocomposite samples prepared by extrusion. These measurements are related to the development of highthroughput characterization techniques. This approach gives qualitative indications about dispersion; however, the more time-consuming analysis, of a few deoxygenated samples from this latter set, offers significantly greater insight into the clay dispersion. A second, probably superior, rapid-analysis method, applicable to oxygen-containing samples, is also demonstrated that should yield a reasonable estimate of the f parameter. Thus, for PS/MMT nanocomposites, one has the choice of a less complete NMR assay of dispersion that is significantly faster than TEM analysis, versus a slower and more complete NMR analysis with sample times comparable to TEM, information rivaling that of TEM, and a substantial advantage that this is a bulk characterization method. © 2003 Wiley Periodicals, Inc.* J Polym Sci Part B: Polym Phys 41: 3188–3213, 200

Nucleic Acids Res

Site-directed spin labeling is emerging as an essential tool to investigate the structural and dynamical features of RNA. We propose here an enzymatic method, which allows the insertion of a paramagnetic center at a specific position in an RNA molecule. The technique is based on a segmental approach using a ligation protocol with T4 RNA ligase 2. One transcribed acceptor RNA is ligated to a donor RNA in which a thio-modified nucleotide is introduced at its 5'-end by in vitro transcription with T7 RNA polymerase. The paramagnetic thiol-specific reagent is subsequently attached to the RNA ligation product. This novel strategy is demonstrated by introducing a paramagnetic probe into the 55 nucleotides long RNA corresponding to K-turn and Specifier Loop domains from the Bacillus subtilis tyrS T-Box leader RNA. The efficiency of the coupling reaction and the quality of the resulting spin-labeled RNA were assessed by Mass Spectrometry, Electron Paramagnetic Resonance (EPR) and Nuclear Magnetic Resonance (NMR). This method enables various combinations of isotopic segmental labeling and spin labeling schemes, a strategy that will be of particular interest to investigate the structural and dynamical properties of large RNA complexes by NMR and EPR spectroscopies

The influence of textile materials on flame resistance ratings of professional uniforms

This study compares the flame speed of different textile materials employed in professional uniforms. Five different garments of aeronauts’ uniforms were analyzed (totaling 200 specimens submitted to flammability tests). Plain weaves and twill weaves composed by 100% CO; 100% PES; 67% PES/33% CO; 50% PES/50% WO; and 55% PES/45%WO were analyzed in the warp and filling directions. The flame speed of each material was determined, and differences in the flame propagation of the fabrics were identified. The lowest flame speed occurred for the material 50% PES/50% WO plain weave and weft direction (0.742 ± 0.140 m/s). The highest flame speed was 3.698 ± 1.806 cm/s for the material 67%PES/33%CO, plain weave and filling direction. Future experiments for reducing the fabric flammability of the uniforms could be related to more closed fabric constructions; mixtures with synthetic fibers to add functionality; changing the direction of the fabric; and changing the weight and torsion of its constituent yarns.São Paulo Research Foundation—FAPESP (“Fundação de Amparo à Pesquisa do Estado de São Paulo”) Grant Number 2016/01331-

Synthesis of Zinc Phosphonated Poly(ethylene imine) and Its Fire-Retardant Effect in Low-Density Polyethylene

A novel oligomeric intumescent fire-retardant chelate, zinc phosphonated poly(ethylene imine) (Zn-PEIP), with a variable Zn2+ loading, was synthesized. The chemical structure of Zn-PEIP was confirmed by FTIR, 13C NMR, and 31P NMR spectroscopies. The thermal behavior and fire retardancy of low-density polyethylene (LDPE) containing 25 wt % Zn-PEIPs with different amounts of Zn2+ were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI) measurements, and cone calorimetry. The TGA results showed that higher concentrations of Zn2+ improved the thermal stability and increased the residue yield of LDPE. However, the data from the LOI and cone calorimetry tests showed that there is an optimum concentration of Zn2+ for the best fire-retardancy performance of LDPE. This behavior is ascribed to the high cross-link density resulting from zinc bridges, preventing normal swelling of the intumescent system. The surface morphology of the char was characterized by digital photography and scanning electron microscopy (SEM). This confirmed the optimum intumescence and coherent and strong barrier layer formation at an intermediate Zn2+ loading

Effect of binder on performance of intumescent coatings

This study investigates the role of the polymeric binder on the properties and performance of an intumescent coating. Waterborne resins of different types (vinylic, acrylic, and styrene-acrylic) were incorporated in an intumescent paint formulation, and characterized extensively in terms of thermal degradation behavior, intumescence thickness, and thermal insulation. Thermal microscopy images of charred foam development provided further information on the particular performance of each type of coating upon heating. The best foam expansion and heat protection results were obtained with the vinyl binders. Rheological measurements showed a complex evolution of the viscoelastic characteristics of the materials with temperature. As an example, the vinyl binders unexpectedly hardened significantly after thermal degradation. The values of storage moduli obtained at the onset of foam blowing (melamine decomposition) were used to explain different intumescence expansion behaviors.Funding for this work was provided by FCT-Fundacao para a Ciencia e Tecnologia (Project PTDC/EQU-EQU/65300/2006), and by FEDER/QREN (project RHED) in the - framework of Programa Operacional Factor de Competitividade-COMPETE. Joana Pimenta thanks FCT for PhD Grant SFRH/BDE/33431/2008

Isoconversional kinetic analysis applied to five phosphoniumcation-based ionic liquids

Thermal degradation of five phosphonium cation-based ionic liquids ([P66614][BEHP], [P66614][(iC8)2PO2],[P66614][NTf2], [P44414][DBS] and [P4442][DEP]) was studied using dynamic methodology (25–600◦C at 5,10 and 20◦C/min) in both inert (nitrogen) and reactive (oxygen) atmospheres. In addition, isothermalexperiments (90 min at 200, 225 and 250◦C) were carried out with [P66614][(iC8)2PO2]. Results indicatethat thermal stability is clearly dominated by the coordination ability of the anion, with [P66614][NTf2] out-performing the other ones in both pyrolytic and oxidising conditions. Although the thermal degradationmechanism is affected by atmospheric conditions, the degradation trend remains practically constant.As the dynamic methodology usually overestimates the long-term thermal stability, an isoconversionalmethodology is better for predicting the long-term thermal stability of these ionic liquids in order to beused as base oil or additive in lubricants formulation. Finally, the model-free methodology can predict atlower costs the ILs performance in isothermal conditions