The elaboration of gels in the system SiO2 – Na2O was realised by destabilization of sols obtained by alkaline attack of a Tunisia sand. The influence of the sol concentration, pH and nature of the destabilization acid on the gelation time was studied. The porous volume and the specific surface of the aerogels, obtained by hypercritical drying, is influenced by the variation of the concentration, pH and aging time of gels.
S. Marzouk, J. Bouaziz, B. Elleuch, M. Fourati
gels, aerogels, specific viscosity, porous volume, specific surface
Pages 851-860
The use of a physical process for water treatment (electochemical softening) permits to reduce the hardness of the water which is distributed either as drinking water or for industrial uses (heaters, process that requires soft water). The electrochemical softening of the geothermal water in the south of Tunisia solves the problems of scale training in pipelines.
K. Walha, M. Ben Amor, S. Douville, R. Rosset
Scaling power, Calcium carbonate, Hardness, Geothermical Water, Electrochemical Softening
Pages 861-871
The distribution data for phosphoric acid (PA) and the major impurities (MgO, Al2O3, Fe2O3, CaO, SO42- and F-) during purification of wet process phosphoric acid (WPA) with tributyl phosphate (TBP) at 25°C are reported. TBP presents a good extraction power, extracting PA even from low concentrated phosphoric medium. The selectivity of TBP for PA against each impurity has been studied as a function of the PA concentration (wt %) in the organic phase. Our results are compared to those obtained with other solvating solvents (dibutyl ether, methyl isobutyl ketone, diethyl ketone and isoamyl alcohol) described in the literature. With regard to metallic impurities, TBP selectivity is always intermediate between those of isoamyl alcohol and dibutyl ether.
R. Dhouib-Sahnoun, M. Feki, H. F. Ayedi
Pages 873-885
Chemical preparation, structural, thermal behavior and IR studies are reported for a monoclinic new organic sulfate, (CH3)2C(NH3)CH2OH]2SO4, having the following parameters: a=10.141(1), b=6.147(1), c=22.548(4) Å, β=97.170(8)°, Z=4, P21/n. The atomic arrangement of the 2-ammonium-2-methyl propanol sulfate denoted AMPS is organized as a layer in the (101) plane. The asymmetric unit of the crystal consists of two independent organic cations and one SO4 anion. These entities are assembled by two types of hydrogen bonds, O–H...O and N–H...O. The stability between successive layers is performed by van der Walls interactions C–H...O originating from the organic cations. Thermal behavior exhibits two reversible phase transitions. IR bands are attributed by comparison with spectra of similar other compounds.
T. Guerfel, A. Jouini
Pages 887-899