Solid -liquid extraction of andrographolide from plants experimental study, kinetic reaction and model

Solid - liquid extraction is performed from leaves and stems of Andrographis paniculata in ethanol - water solvent, in order to obtain andrographolide. The first part of this work concerns the acquisition of the raw plant geometric and physicochemical characteristics. Then batch experiments are done in order to study the influences of the operating parameters (temperature, nature of the solvent and particles size). Furthermore, the destruction of the solute with high temperature is also studied. In the last part, an two-shape extraction model is proposed and compared with experimental data. This model includes the shape factor of the particles population composed of stems and leaves (cylinders and plates)

Synthesis of Multi-Walled Carbon Nanotubes by Fluidized-Bed Chemical Vapor Deposition over Co/Al2O3

Synthesis of multi-walled carbon nanotubes (MWCNTs) was accomplished by catalytic chemical vapor deposition of ethylene over Co/Al2O3 in a fluidized-bed. The reaction temperature and ethylene concentration, as the molar percentage (mol%), were both found to be crucial factors determining the solid carbon conversion level and selectivity of MWCNT formation, but had no significant effect on the size distribution of the obtained MWCNTs. Amorphous carbon and carbon nanofibers (CNFs) were the main products obtained at a reaction temperature of 550°C. Amorphous carbon was also formed when using ethylene at a high concentration (62.5 mol%), which possibly deactivated the catalyst. Increasing the reaction temperature from 550 to 650°C resulted in better graphitized MWCNTs. The average diameters of the synthesized MWCNTs were in the range of 7–8 nm independent of the reaction temperature or ethylene concentration. The selectivity of alkane production decreased considerably at reaction temperatures above 675°C, resulting in a higher productivity of MWCNTs. The activation energy for MWCNT formation was found to be 65.3 kJ/mol, which matched well with that previously reported for carbon diffuusion in liquid cobalt

Regeneration of coked zeolite from PMMA cracking process by ozonation

Regeneration of coked ZSM-5 zeolite was performed by oxidation with ozone at low temperature range (<150°C) so that to restore catalytic activity. Physicochemical properties of the samples were characterized by several techniques: thermogravimetry (nature of coke deposit), elemental analysis (carbon content), porosimetry (surface area and pore size), ammonia temperature-programmed desorption and pyridine adsorption followed by infrared spectroscopy (acidity). Reactions were carried out at various temperatures, gas hourly space velocities and inlet concentrations of ozone. They showed that partially coked samples (containing 3 wt.% of C) can be successfully regenerated by ozone with carbon removal up to 80%. Carbon removal is improved by increasing the inlet ozone concentration in the range 16-50 g/m3, with almost linear trend, and by increasing time on stream until it plateaus after 2 h. Coke oxidation with O₃ starts at low temperature and exhibits an optimum at about 100°C. At higher temperatures, the rate of ozone decomposition becomes much faster than its pore diffusion rate, so that radical species are no longer available for the coke deposit within the particles and the overall oxidation yield decreases. Indeed, catalytic decomposition of ozone is found to occur significantly above 100°C: O₃ decomposition reaches 90% with fresh ZSM-5 catalyst. Thus regeneration of coked zeolite particles involves both complex chemical reactions (coke oxidation and O₃ decomposition to active but unstable species) and transport processes (pore diffusion to the internal coked surface). Ozonation can restore both textural and acidic properties, allowing the catalyst to almost recover its initial activity in poly(methyl metacrylate) cracking. The activity results are well correlated with the carbon removal efficiency

Deposition of tin oxide, iridium and iridium oxide films by metal-organic chemical vapor deposition for electrochemical wastewater treatment

In this research, the specific electrodes were prepared by metal-organic chemical vapor deposition (MOCVD) in a hot-wall CVD reactor with the presence of O2 under reduced pressure. The Ir protective layer was deposited by using (Methylcyclopentadienyl) (1,5-cyclooctadiene) iridium (I), (MeCp)Ir(COD), as precursor. Tetraethyltin (TET) was used as precursor for the deposition of SnO2 active layer. The optimum condition for Ir film deposition was at 300 °C, 125 of O2/(MeCp)Ir(COD) molar ratio and 12 Torr of total pressure. While that of SnO2 active layer was at 380 °C, 1200 of O2/TET molar ratio and 15 Torr of total pressure. The prepared SnO2/Ir/Ti electrodes were tested for anodic oxidation of organic pollutant in a simple three-electrode electrochemical reactor using oxalic acid as model solution. The electrochemical experiments indicate that more than 80% of organic pollutant was removed after 2.1 Ah/L of charge has been applied. The kinetic investigation gives a two-step process for organic pollutant degradation, the kinetic was zero-order and first-order with respect to TOC of model solution for high and low TOC concentrations, respectively

Decolorization of synthetic melanoidins-containing wastewater by a bacterial consortium

The presence of melanoidins in molasses wastewater leads to water pollution both due to its dark brown color and its COD contents. In this study, a bacterial consortium isolated from waterfall sediment was tested for its decolorization. The identification of culturable bacteria by 16S rDNA based approach showed that the consortium composed of Klebsiella oxytoca, Serratia mercescens, Citrobacter sp. and unknown bacterium. In the context of academic study, prevention on the difficulties of providing effluent as well as its variations in compositions, several synthetic media prepared with respect to color and COD contents based on analysis of molasses wastewater, i.e., Viandox sauce (13.5% v/v), caramel (30% w/v), beet molasses wastewater (41.5% v/v) and sugarcane molasses wastewater (20% v/v) were used for decolorization using consortium with color removal 9.5, 1.13, 8.02 and 17.5%, respectively, within 2 days. However, Viandox sauce was retained for further study. The effect of initial pH and Viandox concentration on decolorization and growth of bacterial consortium were further determined. The highest decolorization of 18.3% was achieved at pH 4 after 2 day of incubation. Experiments on fresh or used medium and used or fresh bacterial cells, led to conclusion that the limitation of decolorization was due to nutritional deficiency. The effect of aeration on decolorization was also carried out in 2 L laboratory-scale suspended cell bioreactor. The maximum decolorization was 19.3% with aeration at KLa = 2.5836 h-1 (0.1 vvm)

Decolorization of molasses wastewater from distilleries using bacterial consortium

Les effluents de distillerie de mélasse de canne à sucre génèrent une pollution environnementale due à, d une part de grands volumes et d autres part à la présence de composés de couleur brune foncée, connus sous le nom de mélanoïdines. Dans cette étude, un consortium bactérien CONS8 isolé dans des sédiments de chute d'eau a été choisi comme consortium apte à la décoloration de la mélasse. On a montré que le consortium CONS8 pouvait décolorer, trois eaux usées synthétiques différentes, élaborées respectivement à base de Viandox (13,48% v/v), d eau usée de mélasse de betterave (41,5% v/v) ou d eau usée de mélasse de canne à sucre (20% v/v). Les décolorations obtenues en 2 jours seulement, en fioles d Erlenmeyer sont respectivement de 9,5, à 8,02 et à 17,5%. Quatre bactéries prédominantes ont été identifiées dans le consortium CONS8 par l'analyse de l'rADN 16S. Sur la base de cette identification, et afin de réaliser la décoloration la plus élevée, un consortium bactérien artificiel MMP1 a été reconstruit avec Klebsiella oxytoca, Serratia mercescens (T2) et la bactérie inconnue DQ817737 (T4). Dans des conditions optimisées (aération, pH) le consortium bactérien MMP1 a permis de décolorer l'eau usée synthétique contenant de la mélanoidine à 18,3% en 2 jours. La comparaison de la décoloration par le consortium MMP1 avec un milieu abiotique a démontré que la décoloration était principalement due à l'activité biotique des cellules bactériennes, sans aucun phénomène d'adsorption. Un complément en minéraux et vitamines B n'a pas amélioré la décoloration de mélanoïdines avec le consortium bactérien MMP1. Enfin, les performances d'un bioréacteur à membrane pour traiter les eaux résiduaires synthétiques contenant de la mélanoïdine ont été évaluées à l échelle du laboratoire. L'ensemencement du réacteur a été réalisé avec un inoculum sur la base du consortium MMP1. Le réacteur a fonctionné sous plusieurs conditions de temps de séjour hydrauliques (HRT) de 15, 20, et 40 heures. Les performances ont été analysées en termes de DCO (demande chimique en oxygène), décoloration et croissance de biomasse. Les résultats ont indiqué qu une efficacité accrue d élimination de la DCO et de la couleur ont été obtenues avec le HRT le plus long.Distillery effluent from sugarcane molasses leads to an environmental pollution due to its large volume and the presence of dark brown colored compounds, known as melanoidins. In this study, a bacterial consortium CONS8 isolated from waterfall sediments in Maehongsorn province was selected as a molasses-decolorizing consortium. Consortium CONS8 was able to decolorize, only within 2 days, in Erlenmeyer flasks, three different synthetic wastewaters containing either Viandox sauce (13.5% v/v), beet molasses wastewater (41.5% v/v) or sugarcane molasses wastewater (20% v/v) at 9.5, 8.0 and 17.5%, respectively. Four predominant bacteria present in the consortium CONS8 were identified by the 16S rDNA analysis. To achieve the highest decolorization, the artificial bacterial consortium MMP1 comprising Klebsiella oxytoca, Serratia mercescens (T2) and unknown bacterium DQ817737 (T4), was constructed. Under optimized conditions (aeration, pH), the bacterial consortium MMP1 was able to decolorize the synthetic melanoidins-containing wastewater at 18.3% within 2 days. The comparison of decolorization by the consortium MMP1 with abiotic control proved that the color removal for synthetic melanoidins-containing wastewater medium was mainly due to biotic activity of bacterial cells, without any adsorption phenomena. Supplement of nutrients and vitamin B did not promote melanoidins decolorization by bacterial consortium MMP1. Finally, the performance of a membrane bioreactor (MBR) for synthetic melanoidins-containing wastewater treatment was investigated at laboratory scale, with a mineral membrane. The reactor seeding was made with the MMP1 bacterial consortium inoculum. The reactor was performed with several hydraulic retention times (HRT) of 15, 20, and 40 hours. The performances were analyzed in terms of COD, color removal and biomass in the reactor. The results indicated that the higher COD and color removal efficiency were achieved with the longer HRT.TOULOUSE-INP (315552154) / SudocSudocFranceF

Dégradation par voie microbienne de colorants azoïques par un procédé anaérobie-aérobie

TOULOUSE-ENSIACET (315552325) / SudocSudocFranceThailandFRT

Procédé continu de traitement d'eaux résiduaires de restaurants par oxydation électrochimique

The specific electrode is necessary for destruction of organic pollutant in restaurant wastewater by electrochemical oxidation. In this research, the specific electrode was prepared by metal-organic chemical vapor deposition (MOCVD) in a hot- all CVD reactor with the presence of O2 under reduced pressure. The Ir protective layer was deposited by using (Methylcyclopentadienyl) (1,5-cyclooctadiene) iridium (I), (MeCp)Ir(COD), as precursor. Tetraethyltin (TET) was used as precursor for the deposition of SnO2 active layer. The optimum condition for Ir film deposition was 300 C, 125 of O2/ MeCp)Ir(COD) molar ratio and 12 torr of total pressure. While that of SnO2 active layer was 380 C, 1200 of O2/TET molar ratio and 15 torr of total pressure. The simulation of Ir deposition using FLUENT® shows the good agreement with the experimental data. However, the case of 300 C and titanium substrate, the simulation results have deviated from the experimental data that maybe attributed by the different on surface chemistry of each substrate or the higher surface roughness of titanium substrate. The prepared SnO2/ r/Ti electrodes were tested for anodic oxidation of organic pollutant in a simple three- lectrode electrochemical reactor using oxalic acid as model solution. The electrochemical experiments indicate that more than 80% of organic pollutant was removed in 2 hr. In first 2 hr, the kinetic investigation gives a zero-order respect to TOC of model solution and the destruction of pollutant was limited by the reaction kinetic. Then, it was first-order respect to TOC of model solution that limited by the mass transfer of pollutant to the electrode. Furthermore, the SnO2/Ir/Ti electrodes were used in this restaurant wastewater treatment within Chulalongkorn University. The increase of current density leads to the decrease of TOC and COD removal efficiency as a results of the increases of cell voltage and side reaction. Increasing residence time from 2 to 3 hr had not greatly influenced on TOC and COD removal efficiency due to slower reaction after 2 hr. The SnO2 film thickness had no effect on TOC and COD removal efficiency because the production of adsorbed hydroxyl radicals for pollutant destruction occurred only at the surface of electrode.Cette étude traite de l'élaboration et de la mise en oeuvre d'électrodes spécifiques pour la destruction par oxydation électrochimiques des polluants organiques présents dans les eaux résiduaires de restaurants. Dans ce travail, les électrodes spécifiques sont préparées par dépôt chimique à partir d'une phase vapeur de précurseur organométallique (OMCVD). La sous-couche protectrice d'iridium ou d'oxyde d'iridium est déposée à partir d'iridium methylcyclopentadiene 1-5 cyclooctadiène, (MeCp)Ir(COD) ou d'acetylacétonate d'iridium, Ir(acac)3. La couche catalytique d'oxyde d'étain est quant à elle déposée à partir de tétraéthyl étain (TET). La première partie de l'étude a consisté à déterminer les conditions opératoires optimales pour les différentes couches (iridium, oxyde d'iridium, oxyde d'étain). Un travail de modélisation a également été développé dans le cas du dépôt d'iridium afin d'identifier les paramètres clef du procédé et de faciliter un changement d'échelle du procédé. Les électrodes composites (SnO2/Ir/Ti) ont ensuite été testées lors de la dégradation de solution d'acide oxalique. Les résultats expérimentaux montrent que 80% de la pollution organique est éliminée en 2 heures. Une étude de la cinétique de cette réaction a permis de mettre en évidence que cette dégradation s'opère en deux étapes. La première étape, correspondant aux fortes concentrations de carbone organique total (COT) suit une loi d'ordre zéro alors que pour les faibles valeurs du COT, la cinétique suit une loi d'ordre un qui a été attribuée à une limitation par le transfert de matière. Enfin, ces électrodes ont été mises en oeuvre pour traiter les eaux résiduaires du restaurant universitaire de l'Université Chulalongkorn (Thaïlande). Il a été montré que l'augmentation de la densité de courant conduisait à une diminution de l'efficacité du procédé tant sur la demande chimique en oxygène (DCO) que sur le COT. Il est également apparu que l'augmentation du temps de traitement (de 2 heures à 3 heures) n'avait pas beaucoup d'effet sur l'efficacité du traitement. Il a été montré par ailleurs que l'épaisseur de la couche d'oxyde d'étain n'avait pas d'effet sur l'efficacité de la diminution du COT et de la DCO.TOULOUSE-ENSIACET (315552325) / SudocSudocFranceF

Analyse des distributions de courant dans les réacteurs électrochimiques et modélisation des dépôts d'alliage zinc-nickel

This work is devoted to a multi-scale study of the electrochemical cells met in electrolytic deposits process. The first part interess withe macroscopic modeling of a batch reactor used for copper depolluting. The second part relates to the experimental study of current lines distributions in a rotary. Hull cell and in a modified Mohler cell. The third part deals with the development of a reactional path relating to the zinc-nickel alloy codeposit thus the modeling of this operation. This work led to a set of tools particularly useful and powerful for the development of a new electrolytic deposit plant, so much for the design and the control of the process than for the management of the baths.Ce travail est consacré à une étude multi-échelle des réacteurs électrochimiques rencontrés dans les procédés de dépôts électrolytiques. La première partie s'intéresse à la modélisation macroscopique d'un réacteur batch lors de la dépollution d'un bain de dépôt de cuivre. La seconde partie concerne l'étude expérimentale des distributions des lignes de courant dans une cellule de Hull rotative ainsi que dans une cellule de Mohler modifiée. La troisième partie traite de la mise au point d'un mécanisme réactionnel relatif au co-dépôt d'un alliage zinc-nickel ainsi qu'une modélisation de cette opération. Ces travaux ont conduit à l'élaboration d'un ensemble d'outils particulièrement utiles et performants pour la mise en place de dépôt électrolytique, tant au niveau du design et de la conduite du procédé qu'au niveau de la gestion des bains.TOULOUSE-ENSIACET (315552325) / SudocSudocFranceF