Etude des mécanismes de précipitation du carbonate de calcium. Application à l'entartrage.

The scale deposit observed in industrial and domestic installations is formed mainly by calcium carbonate. The struggle against the formation of scale is therefore tributary of of a better understanding and of the control of the precipitation mechanism of this alt. In this work we have used the chemical and electro-chemical rtechniques to induce the scaling process and associated MEB analyses to Raman spectrometry insuring a good control of the parameters influencing the process.Les dépôts de tartre observés dans les installations industrielles et domestiques sont formés principalement de carbonate de calcium. La lutte contre la formation du tartre est donc tributaire d'une meilleure compréhension et de la maîtrise des mécanismes de précipitation de ce sel. Dans ce travail nous avons utilisé les techniques d'entartrage chimique et électrochimique associées à des analyses MEB et Raman assurant ainsi la maîtrise des paramètres qui influencent le processus

Étude des mécanismes de précipitation du carbonate de calcium (application à l'entartrage)

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Influence of foreign salts to the CaCO

The main purpose of this work was to study the effect of foreign salts, frequently present in natural waters, and inhibitory substances on the scaling of the stainless steel. Scaling tests were made by using the precipitation method based on the dissolved-CO2 degasification coupled with weight method. It was shown that the presence of foreign salts slightly decreases the total precipitate CaCO3 quantity and favoured its incrustation on the walls instead of its formation in the bulk-solution. Nevertheless, this effect is strongly dependent on the salt. In presence of MgCl2, Na2SO4 and MgSO4, the precipitation ratios on the stainless steel surface passes from 48% (in absence of salts) to ∼100%. For the same ionic strengths, this precipitation ratio does not exceed 66% in presence of NaCl. Analysis results show that Mg2+ and SO42− act by partially inhibiting the homogeneous precipitation and strongly favoring the heterogeneous one. On the other hand, it was shown that inhibitory substances such as Na5P3O10 and Polyacrylate molecules unexpectedly favored the incrustation of the stainless steel surface

Assess of physical antiscale-treatments on conventional electrodialysis pilot unit during brackish water desalination

International audienc

Intensification of phosphate removal using electrocoagulation treatment by continuous pH adjustment and optimal electrode connection mode

International audienceThis paper discusses two possible ways of intensifying the electrocoagulation treatment of water contg. phosphate. The first one consists of controlling the chem. compn. of the water by continuous adjustment of the pH. The second aspect focuses on electrode connection modes, and the four different modes were tested monopolar in series, in parallels and independents, and finally bipolar. Expts. were conducted in a small batch reactor contg. water with 100 mg P​/L using electrodes of aluminum. Several elec. connections were used for the water treatment under favorable operating conditions detd. by a study and presented in a previous paper. The influence of pH adjustment was conducted using different adjustment step times (no adjustment, every 30, 10 and 5 min)​. The kinetics of the treatment was found to be accelerated by continuous adjustment of the pH. The choice of the electrode connection modes was found to strongly affect the efficiency of the treatment, the Faradic yield, and the consumption of energy. The monopolar in parallels connection mode was found to be the most economic, whereas bipolar in parallels was found to favor a higher kinetic rate of treatment

Être notable au Maghreb

Le discours dominant dans les pays du Maghreb continue de stigmatiser les figures de notables dits traditionnels au nom de la modernité. L’usage scientifique de la notion de notable n’est pas pour autant disqualifié. Le présent ouvrage s’intéresse au système élitaire au Maghreb sur la longue durée, de l’Antiquité à nos jours. Il en étudie la dynamique en rapport avec les formes historiques du pouvoir et montre comment la notabilité a pris avec le temps des figures changeantes et des nominations successives. Loin d’avoir disparu avec le renforcement de l’État au Maghreb aujourd’hui, la notabilité a su s’adapter, voire infléchir le pouvoir centralisateur, selon des modalités variables, du local au national