Center des Recherches et Technologies des Eaux

Soliman, Tunisia

Center des Recherches et Technologies des Eaux

Soliman, Tunisia
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Karoui H.,University of Caen Lower Normandy | Karoui H.,Center des Recherches et Technologies des Eaux | Riffault B.,University of Caen Lower Normandy | Jeannin M.,CNRS Study of Materials in Aggressive Environments Laboratory | And 4 more authors.
Desalination | Year: 2013

In seawater, during the application of cathodic protection, a scale layer forms on the metal surface. As function of its chemical composition and compactness, it can improve the metal protection against corrosion by reducing the oxygen diffusion. The present investigation focuses on the electrochemical scaling of stainless steel in artificial seawater. Formed scales were characterized by X-ray diffraction, Raman spectroscopy and scanning electron microscopy. It was found that the formed scales are mainly CaCO3 aragonite. The brucite (Mg(OH)2) was identified, as a component of the scale layer, only for a high temperature and a more cathodic potential. It was also shown that, unlike other substrates, stainless steel promotes the precipitation of brucite. If the experimental conditions favoured its formation, the scaling process starts with brucite deposition. The growth of CaCO3 nucleuses, developed on interstice, recovers after brucite layer. © 2012 Elsevier B.V.

Mansouri L.,Center des Recherches et Technologies des Eaux | Mohammed H.,University of Swansea | Tizaoui C.,University of Swansea | Bousselmi L.,Center des Recherches et Technologies des Eaux
Desalination and Water Treatment | Year: 2013

Diethyl phthalate (DEP) is one of the phthalate esters having wide industrial applications, but its occurrence in the aquatic environment has been linked to disruption of the endocrine system. In this study, the removal of DEP with ozone alone (OA) and heterogeneous catalytic ozonation (HCO) with activated carbon (AC) was investigated. Results show that the addition of AC was effective to achieve almost 100% degradation of DEP in about 30 min using 2.86 g AC/L as compared to over 80 min without AC. It was also found that radical reactions were the main mechanism by which DEP was degraded and adsorption contributed significantly to the removal of DEP by OAC. Indeed, after 60 min, adsorption alone achieved about 75% removal, whilst OA achieved 92% removal. In contrast, as expected molecular ozone reactions were relatively insignificant. The contribution of adsorption and radical reactions to the overall removal of DEP were of similar rates at the beginning of the experiments but the latter declined due to competitive reactions. The notable decrease of DEP removal rate observed in the presence of radical scavenger tert-butanol (tb) indicates that the reaction between DEP and proceeds mainly in the bulk of the aqueous phase. Moreover, the experimental results also revealed that in the absence of tb and after 40 min, almost 100% removal was observed as compared to only 64% when tb was added to the solution. This confirms that radical reactions play an important role in DEP removal by the OAC process. A model taking into account the various reactions in the bulk solution and on the surface of AC was developed and was found to predict well the experimental data. This study proves that HCO was effective to remove DEP and the changes of the contributory mechanisms underpinning the process were determined as function of time. © 2013 © 2013 Balaban Desalination Publications.

Boulahlib-Bendaoud Y.,University of Tébessa | Ghizellaoui S.,University of Mentouri Constantine | Tlili M.,Center des Recherches et Technologies des Eaux
Desalination and Water Treatment | Year: 2012

The present work examines the effect of two mineral inhibitors on the CaCO3 precipitation in two Algerian ground waters. The main objective was to reduce the scaling power and then to prevent the fouling phenomenon met in the equipments supplied by these waters. It was shown that, for a large rang of temperature, Hamma water is more scale-forming water than the one of Negrine because its lower content in foreign ions to the calcocarbonic system, especially magnesium. Chronoamperometry tests show that the antiscale treatment with mineral phosphates is more efficient for the Hamma than Negrine water. Tested inhibitors affect strongly the nucleation-growth kinetics in the case of Hamma water and only the scale compactness in Negrine water. This was attributed to the difference in the chemical composition of the studied waters. Besides, it was shown that polyphosphate is more efficient as scaling inhibitor than the dihydrogenophosphate ions. © 2012 Desalination Publications. All rights reserved.

Hamdi R.,Center des Recherches et Technologies des Eaux | Khawari M.,Center des Recherches et Technologies des Eaux | Hui F.,French National Center for Scientific Research | Tlili M.,Center des Recherches et Technologies des Eaux
Desalination and Water Treatment | Year: 2014

Calcium carbonate is one of the most sparingly soluble salts among those forming the scale. As its solubility is dependent on CO2 and then pH, natural water exploitation equipment such as process, drinking or irrigation systems are often faced with a serious scaling problem. Having as an objective to control the scale formation, this present work aims at studying the CaCO3 precipitation threshold using the classic fast controlled precipitation method. Studied solutions to be used are calco-carbonic waters ([Ca(HCO3)2] = 0.4 g L −1). Obvious results show that CaCO3 precipitation threshold occurs at higher nucleation time and lower supersaturation coefficient with lower temperature, stirring speed and dissolved CO2 degasification rate. The probability of CaCO3 heterogeneous precipitation has increased with low stirring speed, low dissolved CO2 degasification rate and low temperature. © 2014 Balaban Desalination Publications. All rights reserved.

Mejri W.,Center des Recherches et Technologies des Eaux | Korchef A.,Center des Recherches et Technologies des Eaux | Tlili M.,Center des Recherches et Technologies des Eaux | Ben Amor M.,Center des Recherches et Technologies des Eaux
Desalination and Water Treatment | Year: 2014

In the present work, the effects of the temperature on the kinetics and microstructure of CaCO3, precipitated in the presence of magnesium and sulphate ions, were studied using degassing dissolved CO2 method. The precipitates were identified by X-ray diffraction, atomic absorption spectroscopy and scanning electron microscopy. It was shown that at fixed temperature and ionic strength, the presence of sulphate and magnesium ions increased the induction time, decreased the crystal growth rate and reduced the amount of the CaCO3 precipitates obtained. Magnesium induced the formation of aragonite form rather than the calcite and vaterite form. The increase of temperature in presence of magnesium and sulphate ions lead to a change on the effect of magnesium on kinetics of CaCO3 precipitation and caused the Mg2+ ions incorporation in the CaCO3 lattice. The increase of temperature favoured the aragonite phase in magnesium solutions and both aragonite and vaterite in presence of sulphate ions. © 2013 Balaban Desalination Publications. All rights reserved.

Ismail T.,Center des Recherches et Technologies des Eaux | Toshihiko M.,Hokkaido University
Desalination and Water Treatment | Year: 2012

Micro-organisms attached to granular activated carbon (GAC) in a fixed bed reactor were applied to treat synthetic leachate with different ratios of carbon to nitrogen. The leachate treatment reactor used in this study was run in batch operation under control of temperature, circulating flow rate, and oxygen concentration in pore space. The efficiency of a new device was estimated by treating artificial leachate having low levels of C/N ratios (0 to 5) at a temperature of 30°C, flow rate of 40 ml/min and oxygen gas concentration ranging from 1%, 5%, 10%, 15% to 21%. It was found that this device is adequate for the elimination of both dissolved organic carbon and ammoniacal-nitrogen. Even with the absence of external carbon supply, the denitrification process occurred. Partial bio-mass decay is considered the main source that supplies carbon to denitrifying bacteria. The average time needed for the elimination of dissolved organic compound (DOC) and NH4 + - N was 1 and 2 d, respectively. © 2012 Desalination Publications. All rights reserved.

Azizi M.,National Graduate School of Chemistry, Rennes | Azizi M.,European University of Brittany | Azizi M.,Center des Recherches et Technologies des eaux | Biard P.-F.,National Graduate School of Chemistry, Rennes | And 4 more authors.
Chemical Engineering Research and Design | Year: 2014

To design and optimize hydrogen sulfide scrubbers working with chlorine, the knowledge of the kinetics of the hydrogen sulfide oxidation is necessary. In this work, the kinetics of the hydrogen sulfide oxidation by sodium hypochlorite was experimentally investigated using a reactor without headspace (100 mL gas-tight syringe) and the competitive kinetics method. The sulfite ion was selected as the reference compound. First, the apparent stoichiometries of sulfite anion and hydrogen sulfide chlorinations were determined performing single-compound experiments. Then, the kinetics of the hydrogen sulfide chlorination was studied in the pH range 6-12 performing simultaneous sulfite and sulfide chlorinations. The results demonstrated that sulfide and sulfite oxidation kinetic rates have the same order of magnitude, which validates the choice of the sulfite anion as the reference compound. Kinetic simulations emphasized that the kinetic rates of the oxidation of both compounds were limited by acid-base reactions. The sulfide oxidation in the pH range 6-12 is mainly due to the hydrosulfide (HS-) oxidation by the hypochlorous acid (ClOH) with an associated kinetic constant of 1.2 × 109 L mol-1 s-1 at 25 °C. © 2014 The Institution of Chemical Engineers.

Chatti A.,Center des Recherches et Technologies des Eaux | Aloui M.,University of Carthage | Tagourti J.,University of Carthage | Mihoub M.,University of Carthage | Landoulsi A.,University of Carthage
Polish Journal of Microbiology | Year: 2014

This study was carried out to determine the effects of novobiocin, a gyrase inhibitor, on the growth, survival, motility and whole cell proteins of S. Typhimurium dam and/or seqA strains. Our results showed that the dam and seqA/dam mutants are the most sensitive to novobiocin, compared to wild type and seqA strains. Surprisingly, the motility of seqA mutants increased after exposure to novobiocin only in stationary phase cells. All the other strains showed a significant decrease in their motility. The analysis of protein profiles of all strains demonstrated several modifications as manifested by the alteration of the expression levels of certain bands. Our work is therefore of great interest in understanding the effects of novobiocin on S. Typhimurium and the involvement of DNA methylation.

Ben Salah Sayadi I.,Center des Recherches et Technologies des Eaux | Sistat P.,Montpellier University | Tlili M.M.,Center des Recherches et Technologies des Eaux
Chemical Engineering and Processing: Process Intensification | Year: 2015

In electrodialysis (ED) desalination plants, calcium carbonate is the main component of meted scales. To prevent its formation several treatments were proposed. For more efficiency, treatments must be assessed at experimental conditions close to real ones. Thus, this work is a contribution to understand and evaluate three anti-calcareous physical treatments for ED desalination systems simulating real conditions. Magnetic field (MF) and ultrasonic field (UF) were applied to concentrate solution, compartment where scaling is imminent in the used ED pilot unit. The third treatment was a pulsed electric field (PEF) application. Tested solution was a synthetic brackish water. Results show that magnetic and ultrasonic treatments accelerate the precipitation of CaCO3 by reducing the nucleation time and the metastable domain. It is also shown that pulsed electric treatment accelerates CaCO3 precipitation resulting from desalination improvement comparing to stationary mode. However, all these treatments favor the homogeneous precipitation which prevents scale formation on membrane surfaces. It seems that MF improves the desalination only by preventing membrane scaling. However, UF and PEF application improve desalination by preventing membrane scaling and by improving the ions transfer during desalination; UF application acts on ions mobility or diffusion, while PEF application reduces the concentration polarization layer. © 2014 Elsevier B.V.

Ben Salah I.,Center des Recherches et Technologies des Eaux | Mouldi Tlili M.,Center des Recherches et Technologies des Eaux | Ben Amor M.,Center des Recherches et Technologies des Eaux
Journal Europeen d'Hydrologie | Year: 2010

The main purpose of this work was to study the effect of foreign salts, frequently present in natural waters, and inhibitory substances on the scaling of the stainless steel. Scaling tests were made by using the precipitation method based on the dissolved-CO2 degasification coupled with weight method. It was shown that the presence of foreign salts slightly decreases the total precipitate CaCO3 quantity and favoured its incrustation on the walls instead of its formation in the bulk-solution. Nevertheless, this effect is strongly dependent on the salt. In presence of MgCl2, Na 2SO4 and MgSO4, the precipitation ratios on the stainless steel surface passes from 48% (in absence of salts) to ∼100%. For the same ionic strengths, this precipitation ratio does not exceed 66% in presence of NaCl. Analysis results show that Mg2+ and SO 4 2- act by partially inhibiting the homogeneous precipitation and strongly favoring the heterogeneous one. On the other hand, it was shown that inhibitory substances such as Na5P3O 10 and Polyacrylate molecules unexpectedly favored the incrustation of the stainless steel surface. © 2010 ASEES.

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