Typologie physico-chimique et métallique des eaux du fleuve Sénégal au niveau de la ville de Rosso (Mauritanie)

L’étude concerne une analyse de la typologie physico-chimiques et métalliques des eaux du fleuve Sénégal : Cas du delta Mauritanien localisé dans la ville de Rosso. L’évaluation de 19 variables est effectuéepar dosage volumétrique et spectroscopique (spectroscopie d'absorption atomique Flamme et Four, ICP) selon le Rodier au cours de la périoded’étude dans les deux saisons de l'année 2006 : Saison froide ''Septembre'' et saison sèche ''Mars''. Les résultats montrent que :- Parmi 19 variables physicochimiques et métalliques évalués seules 14déterminent la typologie physicochimique du milieu étudié. - Deux groupements de relevées sont différenciés. Le premier rassemble des relevés tous effectués en été et caractérisés par des concertations élevés en Ca2+, Mg2+, Na+, Zn2+ et faibles en NO3- et K+ . Le second  groupement est formé par des relevés hivernaux présentant des caractéristiques physicochimiques opposées à celles des relevés dupremier groupement. L’effet du facteur « saison » est donc bien dégagé.Pour les teneurs en Al 3+ et le Sr2+ le facteur saison n’intervient pas. En outre, l’activité domestique et les rejets des eaux usées favorisent la pollution organique de certaines parties de la zone prospectée alors que les rejets des eaux usées industrielles de la sucrerie sénégalaise C.S.S. polluent en Al2+ et Sr2+ d’autres stations. Mais, d’une manière générale les teneurs des éléments chimiques évalués sont dans les nomes de l’eau d’irrigation.Mots-clés : eau potable, eau usée, pollution, concentration métallique, paramètres physico-chimiques, fleuve Sénégal, Mauritani

Immobilization of bio-macromolecules onto membranes via an adsorbed nanolayer. An insight into the mechanism

We have examined the mechanism of bio-macromolecule immobilization onto membranes via an intermediate adsorbed nanolayer. Unlike the formation of polyelectrolyte complex membranes where two charged polyelectrolytes complex each other in a single shot, the bioactive macromolecule immobilization onto membranes involves first the sorption of a polyelectrolyte nanolayer. This results in a firmly adsorbed hydrophilic layer with an overall charge inversed from that of the membrane surface, onto which bio-macromolecules can be adsorbed by multi-point electrostatic interactions. The formation mechanism of the materials is discussed on the basis of thermodynamical and kinetical analyses. The process of polyelectrolyte sorption would be kinetically blocked in a metastable state due to a large increase in the activation energy at a large extent of chain–surface ion-pairing. A variety of situations is expected according to the conditions of sorption of the successive layers. The implications of this for a better bio-macromolecule immobilization for different applications are discussed

New lives for old reverse osmosis (RO) membranes

The overall objective of the present work was to estimate by membrane autopsy the level of performances degradation of old reverse osmosis (RO) membranes/modules in order to envisage their reuse A mechanistic approach using the Spiegler-Kedem-Karchalsky model helps us to observe that the old RO membrane acquired a convective mass transfer We defined a novel Peclet number (denoted Pe') usable to distinguish between diffusional and convective mass transfer We observed that for the old membrane Pe' numbers are always higher than 1. Furthermore, SEM/AFM and EDX experiments show crystals and bacteria particles as fouling agents, roughness increase for the old membrane (from 73 to 220 nm) due to foulants deposition EDX experiments demonstrated that FexOy crystals are dominant SP measurements help us to observe a displacement of the isoelectric point (IEP) for the virgin membrane from 2.7 +/- 0.3 to 4 6 +/- 0 3 in comparison to the old one showing chemical modifications of the inner active layer suspected due to biofouling residuals In the last part and for the first time. module materials reuse Occurred in the place of their incineration as geotextile in proper home garden. Crown Copyright (C) 2009 Published by Elsevier B V All rights reserved

Electrochemical measurement of endogenously produced nitric oxide in brain slices using Nafion/o-phenylenediamine modified carbon fiber microelectrodes

The role of nitric oxide (NO) as a regulatory diffusible molecule in the brain requires the evaluation of its concentration dynamics. In this work, we have developed microelectrodes suitable for real time electrochemical measurements of NO in vitro. Nafion and o-phenylenediamine were used to modify the surface of carbon fiber microelectrodes (8 [mu]m diameter; [approximate]100 [mu]m tip length). Coating with Nafion was done at 170 °C and the o-phenylenediamine solution was electropolimerized on the carbon surface. NO peak potential (+0.78 ± 0.03 V versus Ag/AgCl) was determined by square wave voltammetry with NO solutions prepared from the-generating compound diethylenetriamine/nitric oxide (DETA/NO). Microelectrodes were calibrated by amperometry at a potential of +0.90 V versus Ag/AgCl. They showed good sensitivity (954 ± 217 pA/[mu]M; n = 6) and linearity to NO in the concentration range of 100-1000 nM. They were also characterized in terms of detection limit (6 ± 2 nM, n = 4), response time at 50% (1 s), and selectivity against interferents, such as nitrite (780 ± 84:1, n = 6), ascorbic acid (750 ± 187:1, n = 6) or dopamine (18 ± 2:1, n = 6). Injections of 1 mM l-glutamate, 1 mM l-arginine, and 0.1 mM N-methyl-d-aspartate did not produce changes in background current. Finally, the microelectrodes were used to measure NO concentration dynamics in rat hippocampal brain slices stimulated with l-glutamate and N-methyl-d-aspartate. Taken together, the data indicate that the microelectrodes exhibit the proper sensitivity and selectivity for studies of NO dynamics in brain slices (in vitro) and possibly in whole brain (in vivo) recordings.http://www.sciencedirect.com/science/article/B6TF4-4F8TK92-1/1/1ce4a8139586df9518963631f704eea

Seawater nanofiltration for the elaboration of usable salty waters

International audienceOur article deals with the possibilities to treat seawater using commercial nanofiltration polyamide membranes, denoted NF70 and NF 200, in order to elaborate usable salty aqueous solutions (from high concentrated solutions with total salinity around 70 g/L to isotonic solutions with total salinity in the range of 4 g/L). A theoretical part concerned a hydrodynamical model of mass transfer. This very simple model based on the permeate salt concentrations (using conductivity measurements) vs. the reverse of the permeate flux has been validated for the first time for seawater. This very interesting approach is able to quantify separately both parts of the mass transfer occurring in NF — convection and hydration-diffusion. This fundamental approach was developed in order to contribute to a better understanding of the selectivities observed between monovalent and divalent ions in NF operation. The experiments were conducted in Biarritz (south-west France) under coal pre-filter seawater, just after the Prestige's oil pollution, in order to elaborate personal body washing solutions using NF permeates. Concerning the concentrates we have contributed to the elaboration of hypertonic salty solutions for thalassotherapy centers or home bath applications. Indeed the possibilities of NF in reducing the overall salinity of seawater leads the way to potential applications in the field of human health (e.g., preparation of nasal sprays, medical dietetics, hot mineral springs). Furthermore our investigations conducted in the holy place of the Biarritz Seawater Museum have contributed to discovery of the possibilities of NF concentrates for coral growth studies

Design of titanium nitride- and wolfram carbide-doped RGO/GC electrodes for determination of gallic acid

In the present paper, the electrochemical behavior and the properties of two modified glassy carbon (GC) electrodes used for quantification of gallic acid in sweet wines were compared. A comparative study was conducted between titanium nitride- or wolfram carbide-doped reduced graphene oxide, labeled as TNrGO and WCrGO, respectively, modified GC electrodes, which are promising composite nanomaterials for electroanalytical applications. For the first time, WCrGO was synthesized and its electroanalytical properties compared with those of TNrGO. Results showed that the proposed materials exhibited enhanced characteristics, e.g., low limits of detection (1.1 mu M and 3.1 mu M for TNrGO and WCrGO, respectively), wide linear ranges (for TNrGO 4.5-76 mu M and for WCrGO 10-100 mu M), low adsorption, and low background current, which make them promising candidates for electrochemical sensing applications.Magbiovin project (FP7-ERAChairs-Pilot Call) [621375]Ministry of Education, Science and Technology, the Republic of Serbia [OI 172030]Grant Agency of the Slovak Republic [1/0489/16]Grant Agency of the Slovak Republic VEGA [2/0128/16]info:eu-repo/semantics/publishedVersio