Ben Hamed K.,Center de Biotechnologie de la Technopole de Borj-Cedria |
Zorrig W.,Center de Biotechnologie de la Technopole de Borj-Cedria |
Hamzaoui A.H.,National Center for Research in Materials science
Computers and Electronics in Agriculture | Year: 2016
In order to evaluate the reliability and the practical use of the electrical impedance spectroscopy method applied in the area of salt resistance, electrical impedance spectra were compared in the leaves of halophyte plants cultivated under different growth conditions (biotope versus controlled conditions, hydroponic versus sand system cultures) and different salt stress conditions. The kinetic of impedance parameters was also monitored under short term salinity. The spectra of electrical impedance of leaves under biotope and laboratory conditions showed difference in the electrical response of Cakile maritima in the biotope and laboratory conditions. The response of electrical impedance parameters to salinity was also different in the hydroponic system when compared to the soil one, indicating more stressful conditions in solution culture. The amplitude of the curves of impedance spectrometry decreased when plants were stressed comparatively to their controls, with the highest electrical resistance in the presence of 50 and 100 mM while the lowest value was at 400 mM NaCl. The electrical resistance increased at an early stage after the application of salt stress reaching maximal value 180 min later, before it rapidly declined thereafter. The observed peak can translate a signal, that the plant could have received, which triggers a cascade of metabolic reactions allowing the plant to regain its hydro-ionic balance. In conclusion, electrical impedance spectroscopy can be used to quickly compare different growth conditions as well as different salinity treatments. This method can also separate between the osmotic and the ionic phases of the response to salt stress. © 2016 Elsevier B.V.
Hammami R.,Center for Research and Energy Technologies n |
Ahamed Z.,National Center for Research in Materials Science |
Charradi K.,Center for Research and Energy Technologies n |
Beji Z.,Center for Research and Energy Technologies n |
And 5 more authors.
International Journal of Hydrogen Energy | Year: 2013
Nafion hybrid membrane containing titanium dioxide (TiO2) nano-particles were elaborated by in situ sol-gel technique. Micro wave treatment was used during hybrid elaboration to 2 h. The X-ray diffraction (XRD) shows the crystallization of TiO2 in anatase and rutile phases. The Infrared spectroscopy IR spectrum of hybrid membranes Nafion-TiO2 confirm the presence of bonds Ti-O and Ti-OH which proves that the hybridization of the membrane by sol-gel method is successful. Atomic Force Microscopy AFM confirmed the good dispersion of TiO2 nano-particles. The electrochemical impedance spectroscopy (EIS) and solvent uptake measurements suggest the enhancement of the membrane performance. Copyright © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Chaouachi A.,National Center for Research in Materials science |
M'Nif A.,National Center for Research in Materials science |
Hamzaoui A.H.,National Center for Research in Materials science
Materials Letters | Year: 2014
Colloidal multilayer structures of silica microspheres (or silica opals) have been developed on glass slides using vertical deposition technique. Effect of annealing on structural properties of colloidal silica was investigated using FTIR spectroscopy. Morphology of particles was characterized using atomic force microscopy (AFM). AFM micrographs illustrate the uniform size distribution of silica microspheres in colloidal crystal. With the variation of molarities of reactants, sizes of particles are controlled. Photonic band gap calculations are carried out to show pseudo-photonic band gap of silica opals. Optical characterization proves photonic character of colloidal crystals. It is noticed that forbidden photonic band gap depends on size of spheres forming colloidal crystal. Materials with controllable interesting photonic property are realized by easy and non expensive route and modifying position of stop-band allows to improved engineering of colloidal photonic crystals. © 2013 Published by Elsevier B.V.
Ennigrou D.J.,National Center for Research in Materials science |
Ben Sik Ali M.,Desalination and water treatment Research unit |
Dhahbi M.,National Center for Research and technology water
Desalination | Year: 2014
Copper and Zinc removal from aqueous solution by polyelectrolyte enhanced ultrafiltration (PEUF) process was investigated using poly(acrylic acid) (PAA) with average molecular weight 100kDa. The ultrafiltration studies were carried out using a tangential cell system, equipped with 10,000 MWCO regenerated cellulose. Several parameters have been studied such as: transmembrane pressure, PAA concentration, pH and ionic strength to improve the retention of the metal ions. The removal of Zn2+ and Cu2+ is respectively more than 70% and 93%. A better retention was observed at 2·10-3molL-1 PAA concentration and 3bar transmembrane pressure. The pH effect on the Zinc and Copper recovery revealed a maximum retention around 75% and 97%, respectively, for pH=5. The study of the ionic strength effect has shown a retention decrease with the salt concentration increase. Selectivity was studied using a solution containing the two metal ions. Zinc retention decreases compared to single metal solutions, and this is more significant in the case of Copper ions. © 2013 Elsevier B.V.
PubMed | National Center for Research in Materials science and Desalination and Water Treatment Research Unit
Type: Journal Article | Journal: Environmental technology | Year: 2014
The aim of this work is to study the removal of iron from brackish water using electrodialysis (ED). Experiments were carried out on synthetic brackish water solutions using a laboratory-scale ED cell. The influence of several parameters on process efficiency was studied. This efficiency is expressed by the removal rate, transport flux, current efficiency and power consumption. The applied voltage, the feed flow rate, the pH and iron initial concentration ofthe feed solution have a significant effect on the process efficiency and mainly on the iron transfer from dilute to concentrate compartment. Nevertheless, feed ionic strength does not have an effect on the iron removal. However, the effect is only noted on the specific power consumption.
Hammami M.,National Center for Research in Materials science |
Ennigrou D.J.,National Center for Research in Materials science |
Naifer K.H.,National Center for Research in Materials science |
Ferid M.,National Center for Research in Materials science
Environmental Progress and Sustainable Energy | Year: 2016
Polyelectrolyte-assisted ultrafiltration (PAUF) was investigated for the removal of samarium (III) from aqueous solutions by using poly(sodium 4-styrenesulfonate) (PSS) as a complexing agent. The ultrafiltration studies were carried out using a tangential cell system, equipped with a polyethersulfone membrane. Factors affecting the samarium ions retention, such as applied pressure, polyelectrolyte concentration, pH, and ionic strength, were investigated. After optimization, the best operating conditions can be obtained in order to achieve high levels of recovery. Experimental results indicate that the retention of samarium ions increases respectively with applied pressure and polyelectrolyte concentration. A maximum retention was obtained at 2 × 10−4 mol L−1 PSS concentration and 3 bars transmembrane pressure. Samarium retention by PSS assisted ultrafiltration was influenced by the pH varying from 5 to 9. The study of the ionic strength effect has shown a retention decrease with the salt concentration increase. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 1091–1097, 2016. © 2016 American Institute of Chemical Engineers Environ Prog
Chaari I.,National Center for Research in Materials science |
Moussi B.,National Center for Research in Materials science |
Jamoussi F.,National Center for Research in Materials science
Journal of Alloys and Compounds | Year: 2015
Abstract Clay minerals are efficient adsorbent for dyes due to their colloidal properties. Tunisian raw clay collected from mine of Tamra composed of two species of clay minerals (kaolinite and halloysite) has shown efficiency for removal of azo dye "Direct orange 34" (DO34) from aqueous solutions. For this purpose, the adsorption of DO34 was studied in batch mode under various parameters such as: pH, contact time, adsorbent dose and temperature. The results showed that acid pH is favorable for the adsorption of dye and physisorption on broken edges of clay particles seemed to play a major role in the adsorption process. It was found that the rate of adsorption decreases with increasing temperature and the process is exothermic. The adsorption kinetics followed the pseudo-second-order equation. The intraparticle diffusion and film diffusion are the rate limiting steps. The raw halloysite-rich clay sample (HC) plays a major role in anionic dye adsorption due to mainly to its acidic surface sites.
Brichni A.,National Center for Research in Materials science |
Hammi H.,Tunis el Manar University |
Aggoun S.,Cergy-Pontoise University |
Mnif A.,National Center for Research in Materials science
Advances in Cement Research | Year: 2016
The influence of different parameters on magnesium oxychloride cement (MOC) was investigated in this study. The use of experimental design was found to be very beneficial for determining suitable experimental conditions to obtain a better composition of cement. The studied factors used to model and optimise the operating parameters were stirring speed, mixing time, mass ratio of magnesium chloride/magnesium oxide, silica glass powder (SGP) percentage and SGP particle size. The considered responses were compressive strength and setting time. The phase compositions of MOC were evaluated by x-ray diffractograms, the morphological properties were examined by means of scanning electron microscopy and phase decomposition was analysed using differential thermal analysis/thermogravimetric analysis. It was found that the use of SGP can enhance the water resistance of MOC by the formation of forsterite, which can limit the decomposition of phase 5 and prevent the formation of brucite in water.
Bennani C.F.,National Institute of Research and Physico chemical Analysis |
Ousji B.,National Institute of Research and Physico chemical Analysis |
Ennigrou D.J.,National Center for Research in Materials science
Desalination and Water Treatment | Year: 2015
Abstract: Large amounts of water are daily used in dairy industries for different parts of their services such as chilling, cooling, steam production, pasteurizing, etc. This consumption generates a huge quantity of wastewaters which could be reused after performed treatment. In the present work, a real sample of dairy wastewater was treated using ultrafiltration (UF) and process efficiency and permeate quality were improved by operating under optimum conditions of transmembrane pressure (TMP) and volume reduction factor (VRF). More than 99% of retention rate were observed for turbidity and the BDO5, more than 80% for suspended matter, and 95% for proteins with an optimal TMP fixed at 2.5 bar. Moreover, a reduction of 40 and 55% was recorded for conductivity and the total dissolved salts, respectively. Rather important retention rates varying from 95 to 99% for the majority of the analyzed parameters were observed for a VRF range varying from 1.11 to 2.5. A recovery of 58% of the dairy effluent is possible after treatment by UF using the PES-5 membrane. The permeate quality obtained in optimal TMP and VRF allows the industry to reject its effluents into the river without risks of contamination (according to Tunisian standard for wastewater discharge NT106-02) and to reuse or recycle them during the process (according to Tunisian standard for reusing treated wastewater NT106-03). © 2014 Balaban Desalination Publications. All rights reserved.
Zidi R.,National Center for Research in Materials science |
Bekri-Abbes I.,National Center for Research in Materials science |
Srasra E.,National Center for Research in Materials science
Surface Engineering and Applied Electrochemistry | Year: 2016
In this study, intercalated polypyrrole/montmorillonite nanocomposite was synthesized by a facile and simple solution intercalation method. The method is based on the exchanging of pyrrole monomers with sodium interlayer cations followed by polymerization by adding ammonium persulfate as oxidant. To avoid the spontaneous polymerization of pyrrole outside the clay, the proportions of pyrrole to clay and that of monomer to oxidant were varied. Several techniques have been used to study the structure and conductivity of the obtained materials: Fourier transform infrared spectroscopy, X-ray diffraction, Energy-dispersive X-ray spectroscopy analysis, scanning electron microscopy, Brunaner–Emmet–Teller technique, impedance spectroscopy and ultraviolet–visible spectroscopy. It was shown that it is not necessary to subject clay to organophilation with quaternary alkylammonium or to ultrasonic activation, or to treat it thermally to form intercalated nanocomposite. By increasing the amount of clay to that pyrrole, an intercalated polypyrrole clay nanocomposite is formed. Theevidence of the intercalation of polypyrrole is deduced from the X-ray diffraction and the Brunaner–Emmet–Teller technique specific surface. Both the expansion of the basal interlayer distance to 14 Å and the decrease of the specific surface area from 78.2 for the clay to 48 m2 g–1 prove the formation of an intercalated structure. The conductivity has been measured using impedance spectroscopy. The dc conductivity was in the range of 2–10–3 S/cm. © 2016, Allerton Press, Inc.