JOURNAL of the Tunisian Chemical Society

serving the Research, the Education and the Industry

Characterization of a new organic-cation 1053 monohydrogenmonophosphate dihydrate: C6H16N2HPO4.2H2O

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A new organic phosphate C6H16N2HPO4.2H2O (2,6DMPHP) is prepared by interaction of H3PO4 with the organic molecule 2,6-dimethylpiperazin. This compound crystallizes in the monoclinic system P21/c, Z=8 with the parameters: a=1.3.271(3), b=11.855(4), c=15.748(4)Å, β=105.22(3)°, ρc=1.379, ρm=1.367g/cm3, µ=0.243mm-1. The structural matrix is made up of a three dimensional network of O(W)—H...O, O(P)—H...O and N—H...O hydrogen bonds. The thermal decomposition of 2,6DMPHP shows two large endothermic effects at 127 and 152°C, corresponding to the elimination of water molecules and a set of endotherms, from 170 to 300°C, probably due to the evolution of ammonia from the structure. The overall DDH of the dehydration, deduced from the DSC thermogram, is 82.61 kJ/mol. The IR study, based on theoretical analyses and on in the literature data, allows interpretation of the IR spectrum.

L. Baouab, A. Jouini

Pages 1053-1062

Contribution à l’étude des phénomènes d’entartrage par les eaux géothermales. Partie II: Etude de l’influence des compagnons de cristallisation

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The effect of crystallisation companions (Na+, Cl-, Mg2+, SO42- and Ca2+) of carbonate calcium was been studied by LCGE technique. This study shows that magnesium is the responsible of the aragonitic form of deposit scale in geothermal water. In an other hand, the permanent hardness (Ca2+) is the determinant factor of the abnormal Kinetic behaviour, comparing to pure calco-carbonic system. The sulfate ions slightly delay the CaCO3 germination but the Na+ and Cl- ions are inactive.

H. Elfil, H. Roques

Scaling, Amorphous CaCO3, CaCO3H2O, Calcite, Aragonite, vaterite, geothermal water

Pages 1079-1093

Produits de solubilité apparents des hydroxyapatites calcique, cadmiée et strontique

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The apparent solubility products of calcium, cadmium and strontium hydroxyapatites were determined in dilute solutions of phosphoric acid at 25, 37, 50 and 70°C. The results show that the solubility of the strontium hydroxyapatite is greater than that of the calcium hydroxyapatate which is itself greater than the solubility of the cadmium hydroxyapatite. These apatites show retrograde solubilities. In the case of calcium apatite the infrared spectroscopy and the X ray diffraction patterns don't show any modification of the solid apatitic phase after equilibrium, when in the case of strontium hydroxyapatite the solid phase in equilibrium with the solution at 37°C is a mixture of SrHPO4 and Sr3(PO4)2. The cadmium hydroxyapatite changes also from 50°C to give partially CdHPO4. The appearance of these new phases is assigned to secondary reactions and to the surface effect of the solid particles.

S. Ben Abdelkader, I. Khattech, M. Jemal

Pages 1111-1123

Characterization and thermal behavior of Jebel Ressas clay

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The present study deals with the Jebel Ressas clay thermal behavior related to its mineralogical composition. The mineralogical study of the material consisted on the characterization of the fine fraction by chemical analysis (CA), X-ray diffraction (XRD), infrared spectroscopy (IR) and cation exchange capacity (CEC). The results show that the material is an interstratified illite-smectite mixed with kaolinite. The illite phase in the purified fraction is about 80 %. The CEC and the specific area values of the purified fraction are respectively 39.93 meq/100g of fired clay and 325 m2/g. The thermal behavior of the raw clay is determined by differential thermal analysis (DTA), thermogravimetric analysis (TGA), dilatometry and dry feature. The clay has dehydration, dehydroxylation and carbonate decomposition temperatures respectively at 92°C - 281°C, 503°C and 732°C, a low loss of weight (5.39 %) with a low shrinkage after drying (Rs = 2.39 %) and firing (Rc = 1.8 %) treatments. The temperature of vitrification is about 820°C. This clay sample is suitable for the manufacture of ceramic tiles.

K. Nahdi, N. Gasmi, M. Trabelsi Ayedi, N. Kbir-Ariguib

illite, thermal analysis, thermogravimetric analysis, ceramic, Jebel Ressas clay

Pages 1125-1134

Etude de la solubilité de la silice amorphe dans les solutions salines

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Silica contained in brackish and geothermal waters may cause precipitation and/or fouling problems. Prediction and prevention of these phenomenas need the study of the effect of different parameters on silica solubility. The analytical methods used for determining silica are gravimetry, two absorptiometric determinations using either the yellow rnolybdic acid or the molybdenum blue complex and atomic absorption spectrophotometry. The effect of temperature and pH on amorphous silica solubility are studied. Solubilities are mesured in the following aqueous salts solutions at various concentrations: NaCl, KCl, MgSO4 , CaCl2 MgCl2, LiCl, NaNO3, KNO3 and LiNO3. The experimental values lead to empirical equations for the effect of the studied parameters on amorphous silica solubility. These experimental solubilities allow to deduce the activity coefficients of silica in salt solutions. The results are discussed and compared with those available in literature.

B. Hamrouni, F. El Mannai, M. Dachraoui

amorphous silica, determination, solubility, pH, temperature and salt effect

Pages 1135-1145

Utilisation de la margine comme adjuvant au ciment

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In this work, we studied the incorporated proportion of Olive Mill Waste Water on rheological parameters of cement paste. That showed that spreading of cement paste increases as the amount of Olive Mill Waste Water increased. On another hand, the influence of the amount of this additive on the hydration reaction and on the setting time was investigated. We noticed for a percentage of Olive Mill Waste Water below 0,005%, the additive accelerates the setting of cement, beyond this value, the setting of cement is retarded. Regarding the hydration reaction, a variation of heat flux and of the time of dormant period was studied, which confirm the previous obtained results of the variations of setting time. 

F. Charfi-Fourati, J. Rouis, B. Elleuch

Olive Mill Waste Water, Cement, Setting time, Hydration of cement

Pages 1147-1157

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