OPTIMIZATION OF A PROCESS FOR DISCOLORATION OF LOW-GRADE SYRUP

L'amélioration de la couleur du sirop industriel de qualité inférieure, sur le charbon actif, a été optimisée à l'aide d'une conception composite centrale et d'une méthodologie de surface de réponse. Cette étude vérifie l'effet de trois paramètres expérimentaux : masse d'adsorbant (charbon actif), temps de contact adsorbat-adsorbant (sirop - charbon actif), rapport de masses des farines constituant le gâteau de filtration (m w /m b ) , et leurs interactions sur la réponse : ICUMSA Color. L'exploitation du modèle établi dans l'espace des variables a permis de définir des conditions économiques optimales d'obtention de sirop de classe claire selon la Commission Internationale pour les Méthodes Uniformes d'Analyse du Sucre (ICUMSA)

One-Pot Synthesis of Dihydropyrimidinones/Thiones Catalyzed by White Marble a Metamorphic Rock an Efficient and Reusable Catalyst for the Biginelli Reaction

International audienceIn this work, we report a simple, efficient and green protocol for the synthesis of dihydropyrimidinones/thiones (products of Biginelli reaction) by the use of white marble as an effective heterogeneous catalyst. Short reaction times, high product yields, simple processing procedure and reusability of the catalyst are the superior characteristics of this protocol

Natural Phosphate K09 as a New Reusable Catalyst for the Synthesis of Dihydropyrano[2,3-c]Pyrazole Derivatives at Room Temperature

International audienceIn this study, we report a simple, efficient and green protocol for the synthesis of pyrano[2,3-c]pyrazole derivatives by the use of the natural phosphate K09 as a mild and efficient heterogeneous catalyst. The catalytic efficiency of K09 was compared with other heterogeneous catalysts to determine the best catalyst for said conversion. Easy recovery of the catalyst and its reusability, room temperature reaction conditions, short reaction time, excellent yields, are some of the important features of this protocol

Advanced statistical optimization of parameters of synthesis process of oxygenated carbonated apatite

International audienceThe synthesis process of oxygenated carbonated apatite was optimized by an advanced statistical planning of experiments. Full factorial design of 24 experiments was used to find the effects of five principal parameters: pH of the reaction medium, atomic ratio Ca/P of the reagents, concentration of the calcium solution (Ca2+), temperature of the reaction medium (T) and duration of the reaction (D), with fixing the H2O2 composition at 30% and stirring to 600 turns/min. Studied responses were the atomic ratio Ca/P, % O2, % O2 2− and % CO3 2−. Optimum synthesis parameters were found to be pH = 7.38, Ca/P = 1.647, [Ca2+] = 0.636 M, T = 40°C and D = 1 h. The prediction responses were Ca/P = 1.575, % O2 = 0.76, % O2 2− = 0.50 and % CO3 2−= 1.84. The actual experimental results were in agreement with the prediction

Synthesis, characterization and thermal behaviour of a Phosphocalcic Oxygenated Apatite

A new route for preparing an antiseptic biomaterial has been described. An oxygenated apatite-based calcium phosphate powder that had a Ca/P ratio of 1.55 was synthesized from calcium nitrate and phosphoric acid in oxygenated water via a precipitation method. The X-ray diffraction and FTIR analysis of the as-dried powder reveals that the apatite is poorly crystalline and is converted into a biphasic calcium phosphate (HAP/beta TCP) when calcined at a temperature higher than 600°C. The chemical analysis of oxygenated species shows the disappearance of these species at 400°C

Dissolution kinetic and structural behaviour of natural hydroxyapatite vs. thermal treatment. Comparison to synthetic hydroxyapatite.

International audienceThe dissoln. kinetic and structural behavior of natural hydroxyapatite (N-HA) and synthetic hydroxyapatite (S-HA) was studied vs. sintering temp. and using 'in vitro' expts. Obtained results highlight the chem. stability of N-HA. Any structural modification was obsd. until 1200°C. In the fact S-HA undergoes some modifications. XRD diagrams show the tricalcium phosphate (TCP) phase formation between 800 and 1100°C and tetracalcium phosphate (TetCP) phase formation at 1200°C. The 'in vitro' assay shows that the dissoln. was occurred more in N-HA than in S-HA. The formed TCP activated the dissoln. kinetic and then the pptn. phenomena when a continuous dissoln. of TetCP leaded to slow down the kinetic pptn

Cyanide effluent treatment by electrocoagulation using airlift reactor: Modeling and optimization by response surface methodology

The extraction processes of gold, silver, and various metals from ores consume 13% of 1.1 million metric tons of hydrogen cyanide produced worldwide annually. Therefore, developing efficient processes to treat the issuing effluents before releasing them into the environment is imperative. In this context, the present study aims to evaluate the effect of three factors: inter-electrodes distance (d), current density (J) and electrolysis time (t) on the cyanide removal efficiency by a combination between Electro-Coagulation process and Internal Loop Airlift Reactor. Employing an airlift reactor enables an effective dispersion of the coagulant without the need for additional stirring. The optimization of the process was conducted using Response Surface Methodology in conjunction with Box–Behnken Design. The statistical analysis results reveal that electrolysis time(t)and current density (J) have significant effects on reactor performance to reduce cyanide with a confidence level of 99%, and 97.5%, respectively. The multiple regression analysis method demonstrates the model's overall predictability as the coefficient of determination was 98 % for the cyanide removal efficiency. The investigation inside the RSM 2 and 3-dimensional graphs allowed us to define the optimal domains of the variables to reduce cyanide. At a current density of 68 A.m−2 and an inter-electrodes distance of 13mm during 57.5min of electrolysis time, 98.27% of cyanide removal is achieved. The knowledge obtained through this study using the airlift reactor operating in batch mode and the EC process for the treatment of cyanide effluent confirms EC's ability to successfully remove cyanide and might be useful for the transposition from batch to continuous mode

Synthesis and “in vitro” characterization of melt derived 47S CaO-P2O5-SiO2-NaO bioactive glass

Ceramics - Silikaty, 2008, 3, 121 – 12