Use of Continuous Aeration Respirometry Method for the Prediction of Slightly Saline Waste Water Biodegradation

AbstractThe microorganisms growth kinetics is determined by the physical and chemical characteristics of the environment in which they find themselves and multiply; It is therefore essential to understand the effect of these environmental factors to master cell multiplication and hence the pollution biodegradation. Respirometry has been used in recent years in the laboratory as an assessment technique of microbial activity and an effect detector of the contamination (presence of toxic, stress, increase or decrease in pH, temperature variation .) on bacterial respiration and hence on the biological waste water treatment plant. In this study respirometry has been used as a relatively quick and efficient means to detect the effect of the presence of a salt of up to 5g/l (low salt stress) on the degradation of carbon and nitrogen pollution and on bacterial floc aggregation

Sorption Study of a Basic Dye “Gentian Violet” from Aqueous Solutions Using Activated Bentonite

AbstractVarious industries like textiles, papers, food, plastics, leather, etc are great water and organic colorant users. Hence, the resulting effluents could be an important source of environmental problems, since they may contain stable and non biodegradable contaminants, like organic dyes. The treatment of which is the main scope of the present study. Different ways of dye removal from these effluents do exist, such as flotation, reverse osmosis, chemical flocculation and adsorption etc. Adsorption is used in this work for the removal of a particular basic dye, known as Gentian violet (GV) from an aqueous solution, by means of a natural clay material. The influence of various key parameters like contact time, temperature, ionic strength, etc. on the adsorbed amount of the dye was investigated, for batch conditions. A kinetic study was also carried out, the obtained experimental results were tested against the pseudo first order and the pseudo second order equations. An analysis of the obtained equilibrium data showed that the dye adsorption is best described by the Langmuir model. The obtained results showed that temperature did enhance the Gentian violet dye retention process onto the considered bentonite whereas the obtained thermodynamic parameters indicated that the adsorption process is spontaneous and endothermic. The simultaneous presence of methylene blue, which is another colorant compound, with the Gentian violet was also considered. The clay materials showed a better affinity for the first one i e. methylene blue. In conclusion and according to the obtained results, the clay material may be recommended as an industrial adsorbent for the treatment of effluents containing Gentian violet (GV)

MODELISATION DES SOLUTIONS AQUEUSES D’ELECTROLYTES DU TYPE 3-1 MODELLING OF AQUEOUS ELECTROLYTES SOLUTIONS OF 3-1 TYPE

Pour modéliser les coefficients d’activité des solutions aqueuses d’électrolytes du type 3-1, nous avons repris la théorie originale de Pitzer concernant l’énergie d’excès de Gibbs pour les solutions aqueusesd’électrolyte. Le modèle a été appliquépour 11 systèmes incluant des électrolytes du type 3-1. La performance de ce modèle a été comparée avec d’autres modèles existant dans la littérature. Les résultats montrent que le modèle de Pitzer peut représenter les coefficients d’activité des électrolytes dans des solutions aqueuses avec une déviation standard comparable aux autres modèles et dans la plupart des cas meilleure que les autres. To model the activity coefficients of aqueous solutions of 3-1 electrolytes, we took again the original theory of Pitzer concerning the excess Gibbs energy for the aqueous solutions ofelectrolytes. The model was applied for 11 systems including 3-1 electrolytes. The performance of this model was compared withother models existing in the literature. The results show that the model of Pitzer can represent the mean ionic activitycoefficients of 3-1 electrolytes in aqueous solutions with a standard deviation comparable with the other models and in the majority of the cases better than the others

Modeling of the solubility of Naproxen and Trimethoprim in different solvents at different temperature

The study concerns the prediction of the solubility of pharmaceutical compounds such as Trimethoprim and Naproxen in various solvents like Methanol, Ethanol, 1-Propanol, 2-Propanol, 1-Butanol and 2-Butanol for the first solute and Chloroform, Octanol and Cyclohexane, for the second one. The solubility prediction was performed using thermodynamic models like the UNIFAC, which is a group contribution method, and the semi-predictive model like NRTL. The required interaction parameters for the NRTL are not available and are calculated by optimizing an objective function involving experimental data reported in the literature for the considered systems. Also the obtained results by means of the UNIFAC model for Naproxen showed deviations from the experimental data and therefore new molecular decompositions to generate new groups are proposed and the corresponding interaction parameters are calculated. The influence of the molecular structure on the behavior of the mixture is also discussed. On the other hand a new group representing the Aromatic Nitrogen (AN) present in Trimethoprim is introduced and new interaction parameters concerning these groups are calculated. Finally it may be concluded that the NRTL model led to the best results for the solubility prediction for pharmaceutical compounds

Measurement and Prediction of Binary and Ternary Liquid-Solid Equilibria Of Pharmaceutical and Food Systems

AbstractSolid-liquid equilibria are imperatively required for any design calculations of equipments like crystallizers. Since any experimental measurement is not always easy to carry out, then the modeling of such data can be of a great importance.Consequently the present work deals with measurements by means of the differential scanning calorimetry (DSC) technique, and then predictions of solid-liquid equilibria in order to calculate the necessary interaction parameters for thermodynamic activity coefficient models like the UNIFAC or the NRTL.Binary and ternary systems which may have applications in the food or the pharmaceutical fields, were considered in the present study, with water or formamide as the solvents and D-Sorbitol, D-Glucose and D-Glucose monohydrate, as the solid solute

Experimental and Modelling of liquid –solid equilibria

Solid-liquid equilibria are less considered in inorganic thermochemistry, comparatively to the other two types of phase equilibria involving vapour and/or liquid phases. The great majority of the relevant models, particularly for the calculation of the activity coefficient, concern these last two cases, although their use is extended to handle the solid-liquid equilibria. The first part of the present work concerns an experimental study for the determination of the liquid –solid phase equilibrium diagrams, for various binary systems such as salicylic acid in water, ethanol and chloroform, and naphthalene in phenol, by the means of Differential Scanning Calorimetry. The second part consists of a modeling of these phase equilibria by means of various thermodynamic models such as NRTL, UNIFAC which are also tested for binary systems such as naphthalene in organic solvents. The use of these models requires interaction parameter values which are not always available. Therefore, this work was an opportunity to compute these parameters for the different systems considered. The results obtained experimentally and by modeling, concerning the phase diagrams showed a good agreement, particularly for the NRTL model, compared to UNIFAC which is based on the concept of group contribution and thus is approximate

Supercritical extraction of essential oil from Juniperus communis L. needles: Application of response surface methodology

International audienceThe extraction of oil from Juniperus communis needles was investigated using supercritical CO2. The extraction was carried out varying the pressure in the range of 10–30 MPa, the temperature within 308–328 K, with a solvent flow rate fixed at 0.42 kg h−1, and a mean particle diameter equal to 0.5 mm or less than 0.315 mm. The operating parameters have been optimized using the response surface methodology where a second order polynomial expression was used to express the oil recovery, and the results were satisfactory. The maximum oil recovery relative to the initial mass was 6.55 wt%. It was obtained for an extraction under 328 K, 30 MPa and a particle diameter less than 0.315 mm. Selected samples of extracts were analyzed using gas chromatography–mass spectrometry (GC/MS) and the results show that the most concentrated compounds were germacrene D and 1-octadecene