Chimie

Nombre total de résultats : 169
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Tamanrasset’s Clay Characterization and Use as Low Cost, Ecofriendlyand Sustainable Material for Water Treatment: Progress and Challengein Copper Cu (II)

Aicha Kourim1, Moulay Abderrahmane Malouki2, Aicha Ziouche3, Mouna Boulahbal4, d and Madjda Mokhtari5  (2021)
Publication

In this study, the adsorption of copper Cu (II) from aqueous solution, on Tamanrasset’sclay which is low cost adsorbent, was studied using batch experiments. The adsorption study includesboth equilibrium adsorption isotherms and kinetics. The characterization of the adsorbent necessitatedseveral methods such as X-Ray Diffraction, Scanning Electron Microscopy coupled with EnergyDispersive X-ray, BET for specific surface area determination, Fourier transform infraredspectroscopy and thermogravimetric analysis. Indeed, various parameters were investigated such ascontact time, initial metal ion concentration, mass of solid, pH of the solution and temperature. Theadsorption process as batch study was investigated under the previews experimental parameters. Theresults revealed that the adsorption capacity of Cu2+ is maximized at naturel pH of metal 5.5. Removalof copper by the clay of Tamanrasset (kaolinite) achieved equilibrium within 50 minutes; the resultsobtained were found to be fitted by the pseudo-second order kinetics model. The equilibrium processwas well described by the Langmuir model and the maximum adsorption capacity was found to be26.59 mg/g. Voir les détails

Mots clés : adsorption, Clay, copper, kinetic, Isotherms

Investigation of some physical properties of pure and Co-doped MoO3 synthesized on glass substrates by the spray pyrolysis method

N.Benameur, M.A.Chakhoum, A.Boukhachem, M.A.Dahamni, A.ZIOUCHE  (2019)
Publication

Pristine and Cobalt (Co)-doped MoO3 nanofilms were synthesized on glass substrates using the spray pyrolysis method. The nanometric pristine MoO3 films were prepared from the 10−2 M.L-1 solution of ammonium molybdate tetrahydrate [(NH4)6Mo7O24,4H2O] in distilled water. Co-doping at 0.5, 0.75 and 1% was achieved by adding cobalt (II) chloride hexahydrate (Cl2CoH12O6) in the pristine solution. The structure and the morphology of the films were investigated by means of X-ray diffraction and atomic force microscopy: two pronounced (020) and (040) peaks corresponding to the orthorhombic structure phase of α-MoO3 were detected. The AFM observations revealed the formation of micro-plates, parallel to the surface plane, with a roughness ranging from 33?nm to 54?nm. Optical properties were investigated through reflectance, transmittance and photoluminescence measurements. The optical band gap, the Urbach energy and the refractive index were deduced from these measurements. The presence of oxygen vacancies was revealed from the interband transitions in the blue and green domains. Co-doped MoO3 nanofilms showed ferromagnetic behavior. The photocatalytic degradation of an aqueous solution of methylene blue (MB) under UV irradiation, in the presence of Co-MoO3 nanomfilms, has been carried out using UV–vis spectrometery: the intensity of the absorption peak recorded at 660?nm decreased with the increase of the UV-illumination time while the color of the initial MB solution was drastically waned. Voir les détails

Mots clés : Spray pyrolysis method, MoO3 nanofilms, optical properties, Magnetic Properties

Elaboration and characterization of ITO electrode modi?ed bytransition metal dispersed into polyaniline thin ?lms

Oua?a Belgherbi, Dalila Chouder, M.A. Saeed  (2018)
Publication

This work presents the characteristics of composite materials thin ?lms of polyaniline (PAni) andnickel (Ni) particles deposited onto indium tin oxide (ITO) substrate. The electropolymerizationof aniline was performed in acidic medium by potentiodynamic methods. The nickel particleswere electrochemically deposited on the surface of PAni/ITO by reducing metal ions (Ni) usinga potentiostatic method from a separate solution. The e?ect of applied potential as well as immersingtime of complexation on the amount of nickel dispersed was investigated. Di?erentcharacterization techniques were employed to study the electrochemical behavior and surfacecharacteristics of the Ni-PAni/ITO thin ?lms such as Electrochemical Impedance Spectroscopy(EIS), Cyclic Voltammetry, Fourier Transform Infrared Spectroscopy (FTIR), UV–visSpectroscopy, Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM).The morphology of the obtained composites shows a uniform dispersion of nickel particlesonto the polyaniline matrix and reveals that the immersing times of complexation has a signi?cante?ect on the amount of incorporated particles. The impedance spectroscopy study revealsthat the conductivity of the composite ?lm increases with the amount of nickel incorporated.UV–vis and FTIR results con?rm the presence of PAni and Ni particles on theelectrode surface. Voir les détails

Mots clés : polyaniline, Electro-polymerization, Nickel particles, Chronoamperometry, Materials composites

Etude de l'applicabilité de différents procédés électrochimiques et d'oxydation avancée pour le traitement de rejet de la raffinerie d'Alger

GOUSMI Nawel (2019)
Thèse de doctorat

La demande mondiale de produits pétroliers est en constante d’augmentation, et elle entraîne une exposition dangereuse pour l’environnement. Ces produits génèrent des quantités importantes d’eau lors du processus de raffinage, qui posent de sérieux problèmes dans le traitement biologique du fait de leur résistance à la biodégradation et/ou d’effets toxiques sur les processus microbiens. La persistance de certaines molécules non biodégradables présentes dans ces rejets pourrait entraîner une toxicité pour l'être humain et son environnement. Pour cette raison, les eaux usées de raffineries nécessitent l’emploi de traitements avant de les rejeter dans l’environnement. Les procédés électrochimiques ainsi que les procédés d'oxydation avancée sont parmi les procédés appliqués pour traiter ce type de polluant. L’étude paramétrique appliquant le procédé d’électrocoagulation nous a permis d’optimiser les paramètres étudiés. Après 30 minutes d’électrolyse, pour une densité du courant de 60 A/m2, pH de solution de 5.83 (pH original), une concentration de chlorure de sodium de 1.5 g/L et une distance entre les électrodes fixée à 10 mm, les valeurs finales de la DCO et de la turbidité sont respectivement 208 mg d’O2/L et 1.12 NTU, avec une consommation énergétique égale à   0.323 kWh/kg DCO, soit 0.341 kWh/m3. Voir les détails

Mots clés : effluents industriels, DCO, radicaux hydroxyles, procédés électrochimiques

PLASTICIZING OF POLYLACTIC ACID (PLA) BIOPOLYMER WITH CITRATE ESTERS

M. Maiza, M. T. Benaniba, A. HAMAM, M. MESSAOUDI, B. Bouchoul  (2017)
Article de conférence

Triethyl citrate (TEC) and acetyl tributyl citrate (ATBC) were used as plasticizer for Polylactic acid (PLA). The treated and plasticized PLA at various concentrations were analyzed by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), melt ?ow index (MFI) and thermogravimetric analysis (TGA). Differential scanning calorimetry was used to evaluate the crystallinity and thermal property of all the samples. It was found that the glass transition temperature (Tg) and the melting temperature (Tm) decreased as the amount of citrate esters increased. Additionally, the presence of TEC or ATBC tended to increase the crystallinity of PLA. This result was supported by x-ray diffraction. DMA of plasticized PLA indicates that a decrease in Tg is obtained with increasing plasticizer content, Plasticizing effect was also shown by decrease in the dynamic storage modulus and viscosity of plasticized mixtures compared to the treated PLA. The TGA results indicated that ATBC and TEC promoted a decrease in thermal stability of the PLA. Voir les détails

Mots clés : Polylactic acid (PLA), Plasticizer; Citrate esters; Crystallinity, Triethyl Citrate (TEC), Acetyl Tributyl Citrate (ATBC)

ETUDE DE POLYMERE BIOSOURCE A BASSE DE POLY (ACIDE LACTIQUE) (PLA) PLASTIFIE AVEC DES PLASTIFIANTS VEGETAUX (ESTERS CITRIQUE)

M. Maiza, A. HAMAM, M. MESSAOUDI, M. T. Benaniba  (2017)
Article de conférence

Ces dernières années, le polyacide lactique (PLA) a attiré beaucoup d'attention comme un remplacement des plastiques issus du pétrole. Le PLA est fabriqué à partir de la fermentation du sucre ou de l'amidon. Il est de ressources renouvelables, biodégradables, alimentaires et non toxiques. Le PLA est utilisé dans les emballages alimentaires, la vaisselle jetable, mais aussi dans un certain nombre d'applications biomédicales, telles que les sutures, les stents et certains injecteurs de drogues [1,2]. Le polyacide lactique (PLA) est un polyester aliphatique présente une haute résistance, un haut module, cependant sa fragilité limite ses domaines d’application. Des efforts considérables ont été conduits pour modifier les propriétés de PLA [3,4]. L’objectif de ce travail est la plastification du PLA par l’utilisation des bio-plastifiants à base des esters citrique pour augmenter sa flexibilité. Lors de la préparation des différentes formulations nous utilisons le traitement thermique dans le plastographe Brabender. La plastification du PLA par Triéthyle citrique (TEC), Tributyle 2- acétyle citrique (TBAC), est réalisée par malaxage dans le plastographe Brabender à quatre compositions: 5, 10, 15, 20 et 30%. La spectroscopie infrarouge à transformée de Fourier (IRTF) indiquent qu'il y a des interactions moléculaires par liaison hydrogène intermoléculaire entre le PLA et les esters citriques (TEC et TBAC). Les résultats de diffraction des rayons X (DRX) confirment que le PLA n’avait pas de polymorphe de transition cristalline, les spectres UV-visible indiquent que les deux plastifiants (TEC et TBAC) n’ont pas d’effet sur la transparence et la coloration des films. Voir les détails

Mots clés : Polyacide lactique (PLA), Plastification, Triéthyle citrique (TEC), Tributyle 2- acétyle citrique (TBAC), biodégradable.

Formulation et caractérisation des matériaux biodégradables à base de l’acide polylactique-Plastifiants

MAIZA Mounira (2016)
Thèse de doctorat

In this study, the characterization of plasticized PLA with TEC and ATBC by melt blending method wasreported. The value of the melt flow index (MFI) observed for all samples are higher than those of neat PLA.The evaluation of the influence of the type and plasticizer content on the viscoelastic properties of PLA withDMA indicates a decrease in the storage modulus for plasticized PLA, indicating the flexibility and mobility ofthe amorphous phase of PLA caused by TEC and ATBC. UV-Visible spectroscopy shows that the twoplasticizers: TEC and ATBC have no effect on the color change of the films. The opacity values of the PLAfilms plasticized with TEC and ATBC were slightly lower than the value of the treated PLA film. X-raydiffraction shows the appearance of a strong diffraction at 16.7° assigned to the crystalline phase α, whichconfirms that the PLA has no crystalline polymorph transition. FTIR spectra indicate that there are somemolecular interactions by intermolecular hydrogen bonds between PLA and citrate ester. The thermal propertiesof plasticized PLA shows that TEC and ATBC are effective in lowering the glass transition temperature (Tg), themelting temperature (Tm) and the cold crystallization temperature (Tcc) of the PLA. In addition, its crystallinityincreases with increasing content of plasticizer. The TGA results indicated that the TEC and ATBC promote adecrease in thermal stability of the PLA. The weight loss plasticizer with heating time and at 100 °C is lesserthan at 135 °C. Leaching of TEC and ATBC results in cracks and changed color of material. The tensile testshowed that the formulations of the plasticized PLA with citrate ester (TEC and ATBC) give better mechanicalproperties by providing treated PLA. The observation by SEM confirmed there is miscibility between the PLAand plasticizer. Finally it can be said that the higher molecular weight of citrate exhibited a greater plasticizingeffect. Voir les détails

Mots clés : Polylactic acid (PLA), plasticizing, Triethyl Citrate (TEC), Acetyl Tributyl Citrate (ATBC)

Characterization of toughened Poly (lactic acid) PLA/ Polycaprolactone (PCL) with bio-plasticizers (TEC and PEG3)

M. Maiza, A. HAMAM  (2019)
Article de conférence

Triethyl citrate (TEC) and poly (ethylene glycol) (PEG3) were used as plasticizer for Polylactic acid (PLA)/ polycaprolactone (80PLA/20PCL) blends. The treated and plasticized 80PLA/20PCL blends at various concentrations of plasticizers were analyzed were analyzed by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA), Differential scanning calorimetry was used to evaluate the crystallinity and thermal property of all the samples. It was found that the glass transition temperature (Tg) and the melting temperature (Tm) decreased as the amount of plasticizers increased. Additionally, the presence of TEC or PEG3 tended to increase the crystallinity of PLA. DMA of plasticized PLA indicates that a decrease in Tg is obtained with increasing plasticizer content, Plasticizing effect was also shown by decrease in the dynamic storage modulus and viscosity of plasticized mixtures compared to the treated 80PLA/20PCL blends. The TGA results indicated that PEG3 and TEC promoted a decrease in thermal stability of the 80PLA/20PCL. Voir les détails

Mots clés : Poly lactic acid (PLA), Polycaprolactone (PCL), Plasticizers vegetable, Biodegradable

Enhancement of photoelectrochemical and optical characteristics using a TiO2 nanoparticles interlayer in MEH-PPV heterojunction devices

F Habelhames, M Girtan, A Manole, L LAMIRI, W Zerguine, B Nessark  (2012)
Publication

In this work, MEH-PPV+TiO 2 composite material was prepared by incorporation of titanium oxide nonoparticles (TiO 2) into poly[2-methoxy-5-(2′-ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV) polymer matrix and deposited by spin coating on glass and indium thin oxide (ITO) substrates. The absorbance of various MEH-PPV composites incorporating different concentrations of TiO 2 nanoparticles shows that addition of TiO 2 improves absorption of the composites. TiO 2 and the conjugated polymer have absorption in the UV and visible regions, respectively. As a result, the composite has slightly broader absorption. In addition, absorption of the composite shows that the polymer induces a certain structuring, as evidenced by the presence of fine structures. The effect of inserting a TiO 2 nanoparticles interlayer in the MEH-PPV polymer heterojunction device on the photoelectrochemical and optical characteristics of the device has been studied. The modified device (MEH-PPV+TiO 2) shows improved photocurrent density characteristics, and increased with TiO 2 concentration. The study showed that the presence of inorganic semiconductor nonoparticles (TiO 2) in polymer film improves the optical and the photovoltaic properties of MEH-PPV, and was designed to explore new approaches to improve light-collection efficiency in polymer photovoltaic. Voir les détails

Mots clés : Hybrid composite materials, MEH-PPV, morphology, photocurrent

Growth and characterization of electrodeposited Cu2O thin films

S. Laidoudi, A.Y. Bioud, A. Azizi, G. Schmerber, J. Bartringer, S. Barre, A. Dinia  (2013)
Publication

This work demonstrates the electrodeposition of cuprous oxide (Cu2O) thin films onto a fluorine-doped tin oxide (FTO)-coated conducting glass substrates from Cu(II) sulfate solution with C6H8O7 chelating agent. During cyclic voltammetry experiences, the potential interval where the electrodeposition of Cu2O is carried out was established. The thin films were obtained potentiostatically and were characterized through different techniques. From the Mott–Schottky measurements, the flat-band potential and the acceptor density for the Cu2O thin films are determined. All the films showed a p-type semiconductor character with a carrier density varying between 2.41 × 1018 cm−3 and 5.38 × 1018 cm−3. This little difference is attributed to the increase of the stoichiometric defects in the films with the deposition potential. Atomic force microscopy analysis showed that the Cu2O thin films obtained at high potential are more homogenous in appearance and present lower crystallites size. X-ray Voir les détails

Mots clés : Cu2O, electrodeposition, Mott–Schottky, optical properties, Thin films, XRD