In order to study the coherence of thermodynamic data of the ternary system CsNO3-NaNO3-LiNO3, the CsNO3-NaNO3 phase diagram has been redetermined using direct and differential thermal analysis between 323 and 723 K. This binary system is characterized by an eutectic equilibrium at 467 K. The eutectic point is pointed out at 0.558 mol of NaNO3. A phase transition of NaNO3 appears at 549K and an other due to the soliod-solid phase transition of CsNO3 at 428 K. These results associated with some other literature data have been used to calculate the activities of the constituents along the liquidus curve and the excess thermodynamic functions at 723 K. The binary liquid (Cs-Na)NO3 exhibits a negative deviation from the ideal behavior.
N. Belaid-Drira, H. Zamall, M. Jemal
Cesium nitrate, Sodium nitrate, Binary system, Phase diagram, Activities
Pages 1269-1278
Geochemical analyze of sediments of lake Fouarat level in Morocco reveal the existence of mineralogical associations, particularly Zn and Cu within lithochemicals substrates. The results obtained by the dosage of total metal show that the maximum contents of Zn and Cu is recorded at the station number 4. Analyze of chemical fraction shows that the Zinc was associated preferentially with iron and manganese oxides and carbonates-exchangeables cations phase. However the copper show a strong asoociation with the organic phase. The phases discussed above are easily dissociables with the slightest changes in physicochemical conditions (pH, organic matters content, ...)
H. Benbouih, H. Nassali, A. El Abdellaoui, A. Srhiri
Lake Fouarat, heavy metals, sediment, chemical speciation, metal-lithochemicals subsuates
Pages 1279-1286
Water samples and suspended matter were collected the long of the Sebou river and its tributaries. These samples were analysed for two metals : Cu and Zn to the level of dissolved and particulate. The analysis of the spatio-temporal variation show a maximal pollution zone: oued Fes. The comparison of results obtained with Moroccan norms has allowed to determine the quality of surface waters of this drainage basin, notably in usage: drinkability and irrigation. Sources of contribution are various but, in majority, anthropiques: industry, agriculture and solid wastes.
S. Azzaoui, M. El Hanbali
Cu and Zn, Sebou drainage basin, pollution, water, particulate matters, sources of pollution, water quality
Pages 1287-1292
Polyethylene glycol-bridged polysiloxane-derived gels were synthesized by hydrosilylation reaction between polymethylhydrosiloxane and polyethylene glycols of different chain lengths. The obtained polymers have been characterized by elemental analysis, by FTIR, 29Si CP-MAS NMR and 13C CP-MAS NMR. 29Si and 13C solid-state analysis allowed to show the presence of unreacted hydroxyl ether groups, the occurrence of side reactions and to calculate the degree of cross-linking in the polymers.
S. Moalla, R. Kalfat, P. Tougne, H. Zarrouk, A. P. Legrand
polymethylhydrosiloxane, polyethylene glycol, hybrid gel
Pages 1293-1302
In this work we experimentally studied the variation of partial molal volumes and partial molal enthalpies of mixture of water and dioxane with the molar fraction. XD of dioxane at T = 298°K and P = 1 atm. We also studied the liquid-vapor diagram in order to determine the variation of activity coefficients of water and dioxane with XD. It has been found that : i) Partial molal volumes remain constant at low XD ; ii) The enthalpy of mixture varies in «S» and is equal to zero for XD = 0.46; iii) The liquid-vapor diagram presents an azeotrope for T = 385.5°K and XD = 0.5; iv) Activity coefficients are linear to T-1 . These results are interpreted as follows : A molecule of dioxane locks into the hexagonal hydrogen bond network of water so that the volume effects remain weak. At low XD each dioxane molecule is surrounded by 8 water molecules. The water-dioxane interaction has a H bound character. For XD < 0.5 the solution is quasi-regular and the deviation from the regularity is due to the dioxane-dioxane interaction. Note that our conclusions concerning water-dioxane mixtures agree with some recent structural studies.
J. M’Halla, R. Besbes, S. M’Halla
1,4 dioxane, water, enthalpy, density, azeotrope, regular, structure
Pages 1303-1315
The structure of solid solutions of Cs2HgBr2(SCN)2 (a = 5.9324(4), b = 6.0363(3), c = 16.6701(9)Å; V = 596.95(6)Å3; R = 5.7%) and [Cs0.96(NH4)0.04]2HgBr2(SCN)2 (a = 5.9400(5), b = 6.0150(4), c = 16.6560(14)Å; V = 595.10(7)Å3; R = 4.1%) have been determined by X-ray diffraction to be in the Pnmm centrosymmetric group. The mixed complexes have a chain-based structure. Chains are stacked along the b axis. Within the stacks, bipyramidal trigonal anions are bridged by Br- ions. The Cs+ (Cs+/NH4+) cations are intercalated between chains in a distorted monocapped-triangular prism geometry. The mixed complexes present a new type of structural arrangement from this of pure Cs2HgBr4.
S. Walha, A. Ben Salah, M. Rzaìgui, J. M. Savariault
mixed compounds, crystal structure, bipyramidal trigonal arrangement
Pages 1327-1336
In Tunisia, 22 out of 60 registered thermomineral springs are being used either for therapeutic purposes or commercial waters. This study identifies and quantifies natural radioelements in thermal and mineral waters in Tunisia, using analytical methods which include γ-ray spectrometry, α-particle spectrometry and 226Ra by the emanation method, Radioactivity is essentially due to potassium, radium, uranium and thorium. The results show that the activities of these waters are lower than the maximum concentrations allowed by the International Commission of Radiological Protection (ICRP) for drinking water, and seem to satisfy the recommendations of the World Health Organization (WHO). Consumption of these waters does not represent any hazard to public health.
S. Labidi, M. Dachraoui, H. Mahjoubi, N. Lemaitre, N. Chahed, S. Mtimet
Radioactivity, mineral water, thermal water, radioisotopes
Pages 1337-1343
Copper exchanged ZSM-5 zeolites have been prepared between separate phases of copper chlorides (CuCl, CuCl2.2H2O) and NH4+-ZSM-5 by a solid ion exchange procedure. The ground mixture of the zeolite and the copper precursors has been heat-treated in a flow of dry air or in static conditions (without a flow of dry air). It has been shown that the solid ion exchange proceeds at high temperatures with consumption of the acidic OH groups and evolution of hydrochloric acid under the preservation of the zeolite structure. In contrast, in the case of samples prepared by static condition, we note the destruction of the zeolite structure and formation of amorphous materials when high loading of copper chlorides was used. Nature of copper species in the zeolite matrix has been also discussed.
H. Tounsi, S. Mseddi, S. Djemel, J. F. Lambert
solid-state ion exchange, Cu-ZS M-5, zeolite structure destruction
Pages 1345-1355
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