The selective functionalization on the primary face of β-cyclodextrin with amino groups is described. The inclusion complexation of griseofuvin (GSV) molecules by b-cyclodextrin and its synthesized amino derivatives has been elucidated. The stability constants of the complexes of 1:1 stoichiometry (K11) have been evaluated from 1H chemical shift changes of griseofuvin protons. Mono- and per-amino substuted β‑cyclodextrin showed an increase of inclusion binding ability for griseofulvin guest. The fully amino substituted β-cyclodextrin at the primary face shows the strongest complexation ability towards griseofulvin molecules. A simple thermodynamic theory of the electrostatic contribution to the complexation is presented.
I. Béjaoui, M. Baâzaoui, Y. Chevalier, N. Amdouni, R. Kalfat, S. Hbaieb
Amino-β-cyclodextrins; griseofulvin, inclusion complexes, stability constant
The modified Stöber silica particles were used as support for the development of molecular imprinted polymer matrix for extraction of patulin. γ-MPTS was covalently attached to the surface of Stöber silica particles by means of condensation reaction between surface silanol groups of silica and methoxy groups of γ-MPTS. The prepared silica SiO2‑γ‑MPTS was polymerized through a non-covalent approach using patulin (PAT) as a template, maleic acid (MA) as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as a cross linker, 2,2-azobis- (2- methylpropionitrile) (AIBN) as a precursor and acetonitrile (MeCN) as a porogen solvent to prepare SiO2MA@MIP. The non-imprinted polymer SiO2MA@NIP was prepared following the same synthetic scheme, but in the absence of the template. Molecular imprinted material was used to selective solid phase extraction (SPE) of patulin in apple matrix. The best conditions for PAT extraction using the novel MIP@SPE were: 50 mg mass of SiO2MA@MIP packing in solid phase extraction cartridges, solution of sodium bicarbonate with (1%) acetic acid as washing solvent and 5 mL MeCN as eluting solvent. The developed MIP@SPE has the advantages of MIPs and SPE and could have potential applications for high selective enrichment and determination of PAT in apple juices with a major impact on quality control in food processing, improving product quality and safety with minimal investment.
A. Anene, K. Hosni, Y. Chevalier, R. Kalfat, S. Hbaieb
Patulin, molecularly imprinted polymer, solid phase extraction, MIP@SPE cartridge
The inhibition of corrosion of mild steel in an aerated 0.5 M NaCl solution was studied by using potentiodynamic polarisation in the presence of different concentrations of extract of Nigella Sativa seeds. The presence of this mixture in the solution decreases the corrosion current density. Nigella extract presents an efficient inhibitor of corrosion. It acts as a mixed-type inhibitor and adsorbs on the metal surface according to the Langmuir isotherm model. The values of thermodynamic parameters suggest that the adsorption of inhibitor molecules on the metal surface is chemical.
R. Souli, D. Leila, P. Berçot, E.M. Rezrazi, E. Triki
corrosion, Nigella sativa, mild steel, inhibition, NaCl
The present study investigated the effect of pressure variation during squeeze casting on the microstructural properties of recycled aluminum alloy. Our aim was to find a compromise between the microstructural and mechanical experimental results taking into account the effect of cooling rate. The results of microstructural observations by optical and scanning electron microscopy (SEM), showed a steady increase in the microstructural characteristics of the samples with the application of a 100MPa external pressure evidenced by a significant refinement of the grain size of the alloy. The mechanical analysis involved hardness (HV) and tensile tests showed an improvement with application of pressure under 100MPa. However, a sharp decrease observed with higher applied pressures up to about 150MPa, in that the grain growth and the high concentration of the linear and intrinsic defects on the alloy during molding caused the damage of the sample.
A. Chérif, S. Souissi, M. Ben Amar, C. Bradai, M. khitouni
squeeze casting, cooling rate, microstructure, mechanical proprieties
Lattice energies and Gibbs energies of formation are determined for a series of alkaline diphosphate (pyrophosphate) of formula M4P2O7(s) where M = Li, Na, K, Rb and Cs. The lattice energy, UPOT, is calculated according to two schema of decomposition using the standard Born-Haber-Fajans (BHF) thermochemical cycle and Glasser equation. The results led to the standard molar enthalpy of formation of potassium diphosphate (K4P2O7) as equals -3212 kJ mol-1. This value differs only by 0.6% from literature data. Free Gibbs energy of formation of these compounds was estimated by the determination of their absolute entropy according to Jenkins and Glasser procedure.
H. Gmati-Ben Khaled, I. Khattech, M. Jemal
Lattice Energy, Enthalpy of formation, Entropy of formation, Gibbs Energy of formation, Alkaline Diphosphate (pyrophosphate)
β-MnO2-TiO2, birnessite-TiO2 and todorokite-TiO2 systems were prepared in the aim to be used as catalysts in the removal of Ethanol from air. First, prepared solids were characterized by X-ray diffraction, N2-physisorption, Raman spectroscopy, Scanning Electron Microscopy, H2-Temperature-programmed reduction and photoluminescence. Second, they were tested in the Ethanol oxidation reaction (at low concentration) under ultraviolet light and under nonthermal plasma. The combination of those both technologies was also tested. A comparative study of different catalysts shows that the Mn oxidation state, the structure of Mn oxides, VOCs adsorption capacity and mobility of oxygen could play a key role in the Ethanol oxidation and in the minimization of the undesirable by-products. Besides, the combination of photocatalysis with NTP increased significantly the conversion of Ethanol and decreased the ozone residual concentration.
I. Aouadi, S. Ben Chaabene, J.M. Tatibouët, L. Bergaoui
Non-thermal plasma, Photocatalysis, Birnessite, Todorokite, VOCs.
We report on the elaboration of a new melamine molecularly imprinted silica (MIP). It was synthesized by surface molecular imprinting technique using silica gel as rigid support. Melamine was used as template molecule, 3‑mercaptopropyl trimethoxysilane immobilized onto the silica gel surface was used as a functional monomer and tetraethoxysilane (TEOS) as crosslinker. A non imprinted polymer was used (NIP) for comparison. The prepared materials were characterized by FT-IR, ATG and BET. The batch binding tests were carried out to evaluate the adsorption kinetics and adsorption isotherms either for MIP and NIP. Results show that the imprinted sorbent exhibits higher binding capacity toward Melamine (Qmax = 912 µg.g-1) compared to the non-imprinted one (Qmax = 338 µg.g-1). Two binding isotherm models (Langmuir and Freundlich) were used to check the adsorption mode. The Freundlich model appears as the most suitable model for both imprinted and non-imprinted materials.The adsorption kinetic data were modeled using the pseudo-first and pseudo-second order equations. The results indicated that the adsorption of MEL on MIP follows a pseudo‑second‑order kinetic. Differentiation between adsorption phenomena onto each of the two substrates has been proposed and compared to the theoretical classification of adsorption isotherms. The application of intraparticle diffusion kinetics model has indicated that intraparticle diffusion was not the only rate limiting mechanism in the adsorption process.
F. Arfaoui, N. Jaoued-Grayaa, A. Riani Khlifi, R. Kalfat
Melamine, Molecularly Imprinted Polymer, silica gel
An efficient synthesis of new thioether compounds through the thia-Michael protocol under mild condition is described. The reaction of thiols and dithiols with β-carbonylethoxyallylic sulfones and sulfides, leads to the formation of di- and tetra-thioethers respectively. The methodology could be extended to the synthesis of new cyclic thioethers in high yields.
A. Hafedh, A. Abdelli, M.L. Efrit, H. Mrabet
Michael acceptor, thiols, allylicsulfure, thioethers
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