Effect of surfactants on liquid side mass transfer coefficients

In the present paper, the effect of liquid properties (surfactants) on bubble generation phenomenon, interfacial area and liquid side mass transfer coefficient was investigated. The measurements of surface tension (static and dynamic methods), of Critical Micelle Concentration (CMC) and of characteristic adsorption parameters such as the surface coverage ratio at equilibrium (se) were performed to understand the effects of surfactants on the mass transfer efficiency. Tap water and aqueous solutions with surfactants (cationic and anionic) were used as liquid phases and an elastic membrane with a single orifice as gas sparger. The bubbles were generated into a small-scale bubble column. The local liquid side mass transfer coefficient (kL) was obtained from the volumetric mass transfer coefficient (kLa) and the interfacial area (a) was deduced from the bubble diameter (DB), the bubble frequency (fB) and the terminal bubble rising velocity (UB). Only the dynamic bubble regime was considered in this work (ReOR = 150 - 1000 and We = 0.002 - 4). This study has clearly shown that the presence of surfactants affects the bubble generation phenomenon and thus the interfacial area (a) and the different mass transfer parameters, such as the volumetric mass transfer coefficient (kLa) and the liquid-side mass transfer coefficient (kL). Whatever the operating conditions, the new kLa determination method has provided good accuracy without assuming that the liquid phase is perfectly mixed as in the classical method. The surface coverage ratio (se) proves to be crucial for predicting the changes of kL in aqueous solutions with surfactants

Analysis of membrane fouling during cross-flow microfiltration of wine

The aim of this study was to investigate the individual impact on wine molecules as tannins, pectins and mannoproteins on multichannel ceramic membrane fouling during wine cross-flow microfiltration. The characterization of fouling mechanisms involved in the previous filtrations was realized by using the classical fouling models and the analysis of the total resistance curves. It was shown that the obtained initial fluxes are dependant of the nature of the studied molecules and their concentration. According to their increasing effect on permeate flux decline, the studied wine components could be ranked as: mannoproteins < tannins < pectins. During the filtration of wine added with tannins, it was found that the filtrations were governed by the cake layer formation mechanism. The presence of pectins caused the formation of gel-type layer which is found to be compressible under high pressures. For wines added with mannoprotein filtrations, it was shown that there is a threshold concentration above which a plateau value of permeate flux is obtained. Industrial relevance: The cross-flow microfiltration applied to wine filtration has become a legitimate alternative to conventional filtration processes. However, membrane fouling which affects the operating costs and the plant maintenance, limits the widespread application of this technique. To avoid or reduce membrane fouling, it is extremely important to identify the fouling elements and the mechanisms that govern the process. A better understanding of the mechanisms whereby fouling is formed during wine microfiltration may lead to be in position to control fouling or reduce it, to improve cleaning procedures and to adapt the process to the product to be filtered. The results presented in this paper concern the investigation and the understanding of fouling mechanisms by wine colloids (tannins, pectins and mannoproteins). We found that wine colloids had a strong impact on membrane fouling. Independently of their concentrations found in wine, they can be ranked according to their increasing effect on permeate flux as: mannoproteins b tannins b pectins. Such result provides important information and a better vision on the methods which can be used to limit membrane fouling for example the use of pectinolytic enzymes before filtration in order to hydrolyze pectin chains or precipitation of unstable tannins by finning the wine with bentonite. By elucidating fouling mechanisms such as cake layer and gel type layer, we can adapt the hydrodynamic process to control membrane fouling

Cross-flow microfiltration applied to oenology: A review

The cross-flow microfiltration applied to wine filtration has become a legitimate alternative to conventional filtration processes. However, membrane fouling which affects the operating costs and the plant maintenance, limits the widespread application of this technique. The aim of this review is to provide a better understanding of the development of the cross-flow microfiltration in wine industry, as well as the complexity of wine composition and its consequences on membrane fouling. This review covers also the impact of the operating conditions and the membrane characteristics on fouling mechanisms. Strategies to limit fouling as well as the latest innovations and commercial proposal are discussed in this paper

Impact of the physico-chemistry of the wine on membrane filtration performance

During the process of wine making, operation of cross-flow microfiltration allows a one-step clarification and sterilization of wine, with lower waste compared to the conventional processes of clarification and sterilization. Indeed, these processes are sources of voluminous waste (earth, Kieselguhr, additives), when discharges are becoming more and more restricted by environmental and health rules. Nevertheless, cross-flow microfiltration of wine presents a major drawback: membrane fouling causes a significant decrease in the flow rates, due to excessive retention of some wine components which could lead ultimately to the alteration of the quality of wine. The aim of this work was to study the impact of some specific wine components (phenolic compounds and yeast extract), as well as some physico-chemical parameters (pH) in regard to membrane fouling. Studies were performed using one red wine and synthetic wines, using cellulose acetate membranes (0.2 μm) operated in the dead-end mode under 2 bar pressure. The simultaneous presence of the both species of phenolic compounds (anthocyanins and tannins) in the synthetic wine was shown to be the main cause of fouling, whereas the presence of one specie leads only to standard blocking type behavior. An important decrease in the flow rates was also observed when yeast extract was added to the liquid. This yeast extract was shown to contain 300 mg/g of proteins and to be free of mannoproteins. The influence of these proteins on fouling was demonstrated while pre-treating the synthetic wine with bentonite, which was able to adsorb proteins, and in this case, no fouling was observed. It was also shown that, when decreasing the pH, the flow rate was enhanced. For all experiments, a fouling index or cake specific resistance, according to the type of fouling, was calculated in order to be used as a reference to estimate the filterability of a given wine, according to its composition in some targeted molecules. Finally, the experiments of the actual red wine exhibited complete rapid fouling of the membrane, probably due to the presence of high concentration of phenolic compounds

Etude par capteur optique du dépôt formé lors de la filtration d'une suspension de bentonite sur fibre creuse

Lors de la filtration sur fibres creuses de suspensions de bentonite, il a été mis en évidence que le facteur limitant est la formation d'un dépôt à la surface de la fibre.Parlant de ces considérations, un dispositif optique a été mis au point pour suivre l'évolution spatio-temporelle du dépôt en cours de filtration sur fibre creuse à peau externe.Ainsi, il a pu être mis en évidence que l'influence de la vitesse d'écoulement n'est sensible qu'après un certain temps de filtration ou un certain volume filtré.Dans le domaine testé des faibles vitesses d'écoulement, il existe une période initiale où la loi de filtration sur gâteau est applicable.Dans le cas de fibres creuses à peau externe, l'optimum technique (productivité maximale) ou économique (coût minimal du m3 traité) serait donc plus à rechercher dans une optimisation de la séquence filtration-lavage que dans une augmentation de la vitesse d'écoulement.L'efficacité du réentraînement du dépôt lors du lavage peut être suivie grâce à l'équipement et au capteur développés.Use of membranes (MF or UF) for water treatment is now developed at an industrial scale. This approach is considered as a good solution to deal with the periodic strong increases in suspended solids contents which occur in karstic aquifers.Under these conditions, the main contribution to the growth of hydraulic resistance is related to the formation of a deposit on the membrane surface.Thus, an experimental study was performed at the laboratory scale in order to perform on line characterization of deposit formation during the filtration of a bentonite suspension through a hollow fiber.The filtration module is transparent and contains only one hollow fiber with its external skin.An optical device formerly developed was used as a sensor : a horizontal laser beam is focussed at the surface of the hollow fiber which is held perpendicular to the beam and can be moved step by step in the micrometric range.Experiments were performed with a bentonite suspension (concentration 0.375 kg/m3) and under different operating conditions :- dead end filtration and crossflow filtration with velocities up to 0,30 m/s in the annular space (which means Re ≈ 2000, velocity gradient ≈ 1000 S-1, shear stress ≈ 1 Pa) ;-transmembrane pressure between 85 and 185 Kpa.One of the main conclusions of this study is that influence of the velocity appears only after an initial period during which the growth of the deposit and the filtrate flowrate variation with time are in agreement with the equations of dead end filtration at constant pressure.Thus a combination of dead end filtration and periodic backwash for removing the deposit might be the best solution for getting the highest productivity with minimal energy consumption.These optimal conditions may be simulated using the equations of dead end filtration at constant pressure and making the assumption that the backwashing is fully efficicent.The experimental study of backwashing, using the optical sensor for measuring the diameter of the fiber after each backwashing, proves that this assumption is correct and that it is possible to get a steady mean filtrate flux by periodic backwashing.From the theoretical study, the optimal duration of the filtration period is rather short (about 10 minutes) but the decline after the maximum is very malt, which means that the fiitration period may be longer without significative variation of the productivity.Thus the method presented here is able, if applied to actual raw water, to give technical and economical elements of comparison between dead end filtration with periodic backwashing and crossflow filtration

Implicit reconstruction by zooming

This paper presents a new method to infer 3D information using a static camera equipped with a zoom-lens. The modelling algorithm does not required any explicit calibration model and the computations involved are straightforward. This approach uses several images of accurate regular grids placed on a micrometric table, as calibration process . The basic idea is to compute a local transformation that allows to establish a relationship between a distorted grid detected on the CCD matrix and the real one located in front of the camera . This relationship takes automatically into account all distortion phenomena and allows to obtain reconstruction results much more accurate than previous works in the same field . A complete experiment on real data is provided and shows that it is possible to compute 3D information from a zooming image set even if data are close to the optical axis .Cet article présente une nouvelle méthode permettant d'inférer des informations tridimensionnelles à l'aide d'une caméra statique munie d'un zoom. L'algorithme de modélisation ne nécessite aucun modèle explicite de calibrage et met en oeuvre plusieurs images de grilles régulières et précises formant un espace métrique particulier. Une transformation locale permet d'établir une relation entre l'image distordue d'une grille détectée sur la matrice CCD et une grille réelle située devant la caméra. Cette relation prend automatiquement en compte les phénomènes de distorsion optique et permet d'obtenir des résultats de reconstruction bien meilleurs que ceux obtenus jusqu'à présent en reconstruction axiale par zoom. De plus, la méthode présentée permet de calibrer l'objectif sur une gamme importante de distances focales sans changer d'objet de calibrage. Une expérimentation complète sur des données réelles est présentée et montre qu'il est possible de reconstruire des objets 3D à partir d'une séquence d'images de zoom même si ces données sont proches de l'axe optique

A New Test of Filterability for Unprocessed Wines Evaluation of the Enzyme Efficiency

A new Test of Filterability has been developed. Measurements carried out with different types of wines indicate that the new filterability index is a useful tool for understanding and predicting the propensity to fouling of treated or untreated wines, e.g. with or without enzyme addition. The measurement method used in the Test of Filterability, requires only one type of membrane for all types of wine, and uses the same equipment as the traditional Fouling Index. Numerous trials have demonstrated that the filtration of wines is governed by standard blocking law. The definition of the new Test of Filterability, based on this filtration law, is proposed. The choice of membrane and the selection of the optimal pore size were based on the results of the experiments. Current methods used for the determination of fouling properties in wine filtration have been developed for the membrane filtration of small quantities of suspended matter. Enzyme treatment is a process often used in wine clarification. The new Test of Filterability indicates the best conditions for the filtration of all types of wines. The test is easy to implement and has been validated with various wines. This new Test of Filterability is an important tool for winemakers as it constitutes a simplified test of a wine's filterability. The new test may also be used to determine the filtration process that is best adapted to each wine while reducing the number of operations. The same approach may be adopted for the filtration of other liquids.&nbsp

The use of nanofiltration membranes for the fractionation of polyphenols from grape pomace extracts

Filtration experiments in batch concentration mode (with recycling of the retentate stream) of grape pomace extract were performed in laboratory filtration membrane equipment by using nine commercial nanofiltration (NF) membranes with an approximate molecular weight cut-off (MWCO) of 1000‒150 Da. The filtration experiments of the selected pomace extract were performed by modifying the most important operating variables: transmembrane pressure, tangential velocity, temperature, and the nature and MWCO of the membranes. The evolution of the cumulative permeate volumes and permeate fluxes with processing time was analyzed till a volume reduction factor (VRF) of 10 was reached. The effect of the mentioned operating conditions was discussed. The effectiveness of the filtration treatments was determined by the evaluation of the rejection coefficients for several families of polyphenols. Membranes possessing MWCO between 1000 and 500 Da were able to quantitatively recover polymeric proanthocyanidins in the concentrate stream and separate them from phenols that passed through the membrane into the permeate stream. On the other hand, the 600 to 300 Da membranes could also be used for the fractionation of monomeric phenolic families. The membranes were able to partially remove the anthocyanin fragments of phenolic acid derivatives and flavonols in the concentrate stream and at the same time

Guía de Práctica Clínica para el diagnóstico de compromiso orgánico de amiloidosis: Parte 2/3. Año 2020

Métodos: Se generó un listado de preguntas con el formato PICO centradas en la especificidad y sensibilidad de las pruebas diagnósticas en amiloidosis. Se realizó la búsqueda en PubMed durante julio-agosto del 2019, en inglés y español. Los niveles de evidencia y los grados de recomendación se basan en el sistema GRADE (http://www.gradeworkinggroup.org/index.htm). Las recomendaciones se graduaron según su dirección (a favor o en contra) y según fuerza (fuertes y débiles). Las recomendaciones finales fueron evaluadas con la herramienta GLIA para barreras y facilitadores en la implementación de éstas. Interpretación de recomendaciones: Las recomendaciones fuertes indican alta confianza, ya sea a favor o en contra, de una intervención. En esta guía se utiliza el lenguaje “se recomienda” cuando se define una recomendación fuerte. Las recomendaciones débiles indican que los resultados para una intervención, favorable o desfavorable, son dudosos. En este caso, se utiliza el lenguaje “se sugiere”, cuando se define una recomendación débil. Cómo utilizar estas pautas: Las recomendaciones deben ser interpretadas en el contexto de la atención especializada, con estudios diagnósticos validados y realizados por médicos entrenados. Se asume que el médico tratante tiene alto nivel de sospecha de amiloidosis. Asume que los estudios diagnósticos son realizados por médicos entrenados con métodos validados y estandarizados. Esta guía es relevante para los profesionales de la salud y los involucrados en las políticas sanitarias, para ayudar a asegurar que existan los acuerdos necesarios para brindar la atención adecuada. Resumen de recomendaciones En pacientes con sospecha de amiloidosis, se recomienda realizar: ● Un electrocardiograma como evaluación inicial a todo paciente con amiloidosis. ● Ecocardiograma Doppler convencional como imagen inicial de elección para el diagnóstico de amiloidosis cardíaca en pacientes con sospecha de compromiso cardíaco por amiloidosis. ● Ecocardiograma con deformación (strain) para el diagnóstico de amiloidosis cardíaca en pacientes con un ecocardiograma convencional sugestivo o indeterminado de amiloidosis. ● Resonancia magnética cardíaca (RMC) con gadolinio para el diagnóstico de amiloidosis cardíaca en pacientes con estudios previos sugestivos o indeterminados de amiloidosis. ● RMC con técnica de mapeo T1 para el diagnóstico de amiloidosis cardíaca en pacientes con estudios previos sugestivos de amiloidosis y disfunción renal o contraindicación para recibir gadolinio, como alternativa a la RMC con gadolinio. ● RMC con técnica de mapeo T1, medición de volumen extracelular y la cuantificación de la extensión del compromiso cardíaco para el diagnóstico y medición del compromiso cardíaco por amiloidosis en pacientes con estudios previos sugestivos de amiloidosis. Se sugiere realizar: ● RMC con técnica de mapeo T1 y medición del volumen extracelular para el diagnóstico precoz por amiloidosis en pacientes con estudios previos sugestivos de amiloidosis. ● Medición de péptido natriurético tipo B para el rastreo y diagnóstico de amiloidosis cardíaca. ● Centellograma con pirofosfato para el diagnóstico inicial de pacientes con sospecha de amiloidosis cardíaca, diferenciando ATTR (positiva) del resto. Palabras clave: amiloidosis; diagnóstico; amiloidosis de cadenas ligeras de las inmunoglobulinas; amiloidosis familiar.Method: Use the PICO format to generate a series of questions, focusing on the specificity and sensitivity of the amyloidosis diagnostic test. PubMed searches were conducted in English and Spanish from July to August 2019. The level of evidence and recommendation are based on the GRADE system (http://www.gradeworkinggroup.org/index.htm). The recommendations are graded according to their direction (for or against) and strength (strong and weak). Finally, it is recommended to use GLIA tools to evaluate the obstacles and facilitators in implementation. Suggested explanation: A strong suggestion indicates a high degree of trust in support or opposition to the intervention. When defining a strong recommendation, this guide uses the "recommended" language. The weaker recommendations indicate that the outcome of the intervention (favorable or unfavorable) is doubtful. In this case, if a weak recommendation is defined, the "recommendation" language is used. How to use these guidelines: Recommendations must be explained within the scope of special care in validated diagnostic studies conducted by specially trained doctors. Presumably, the attending physician has a high degree of suspicion of amyloidosis. It assumes that diagnostic research is conducted by well-trained doctors using a validated standardized method. This guide is intended for health care professionals and those involved in health care policies to help ensure that the necessary agreements have been reached to provide appropriate care. Summary of recommendations For patients with suspected amyloidosis, it is recommended: ● Electrocardiogram be used as a preliminary assessment for all patients with amyloidosis. ● Doppler echocardiography conventional be used as the initial image of the first choice for cardiac amyloidosis in patients diagnosed with suspected heart involvement due to amyloidosis. ● Echocardiographic strain diagnosis for patients with amyloidosis prompted by conventional echocardiography or uncertain. ● Cardiac magnetic resonance imaging (MRI) be used for the diagnosis of cardiac amyloidosis in patients with previous studies suggesting or uncertain amyloidosis. ● T1 mapping technology for cardiac MRI to diagnose myocardial amyloidosis as an alternative to MRI, for patients with kidney failure or contraindication to other studies ● Cardiac MRI examination with T1 localization technique for patients who have previously studied amyloidosis, and measure the extracellular volume and quantify the degree of cardiac involvement in order to diagnose and measure the cardiac involvement caused by amyloidosis. It is suggested: ● Cardiac MRI with T1 mapping technique and extracellular volume measurement for the early diagnosis of amyloidosis in patients with previous studies suggestive of amyloidosis. ● Measurement of type B-type natriuretic peptide measurement be used for screening and diagnosis of cardiac amyloidosis. ● Pyrophosphate scintigraphy to make a preliminary diagnosis of patients with suspected cardiac amyloidosis, so as to distinguish ATTR (positive) from other patients. Key words: amyloidosis; diagnosis; inmunoglobulin light-chain amyloidosis; amyloidosis, familial.Method: Foi gerada uma lista de questões com o formato PICO focada na especificidade e sensibilidade dos testes diagnósticos em amiloidose. A busca no PubMed foi realizada no período de julho a agosto de 2019, em inglês e espanhol. Os níveis de evidência e graus de recomendação são baseados no sistema GRADE (http://www.gradeworkinggroup.org/index.htm). As recomendações foram graduadas de acordo com sua direção (a favor ou contra) e de acordo com a força (forte e fraca). As recomendações finais foram avaliadas com a ferramenta GLIA para barreiras e facilitadores em sua implementação. Interpretação das recomendações: Recomendações fortes indicam alta confiança, a favor ou contra, de uma intervenção. Este guia usa a linguagem “recomendada” ao definir uma recomendação forte. Recomendações fracas indicam que os resultados para uma intervenção, favorável ou desfavorável, são duvidosos. Nesse caso, a linguagem “é sugerida” é utilizada, quando uma recomendação fraca é definida. Como usar essas diretrizes: As recomendações devem ser explicadas no contexto de cuidados especializados e estudos de diagnóstico validados realizados por médicos treinados. Suponha que o médico assistente suspeite de um alto nível de amiloidose. Ele presumiu que a pesquisa diagnóstica foi conduzida por médicos bem treinados usando métodos padronizados validados. Este guia se aplica a profissionais de saúde e a todos os envolvidos na política de saúde para ajudar a garantir que os arranjos necessários sejam feitos para fornecer cuidados adequados. Resumo das recomendações para diagnóstico Em pacientes com suspeita de amiloidose, é recomendado: ● Um eletrocardiograma como avaliação preliminar. ● Doppler convencional seja usado como primeira escolha para o diagnóstico de amiloidose cardíaca em pacientes com suspeita de amiloidose. ● Ecocardiografia deformada para o diagnóstico de pacientes com amiloidose ou ecocardiografia convencional incerta ● Ressonância magnética cardíaca (RMC) anterior seja usada para o diagnóstico de amiloidose cardíaca em pacientes que realizaram estudos sugestivos ou incertos sobre amiloidose. ● Mapeamento T1 para diagnosticar amiloidose cardíaca com RMC em pacientes com amiloidose e insuficiência renal ou contraindicações de uso. ● Mapamento T1 para pacientes que estudaram previamente a amiloidose para medir o volume extracelular e quantificar o grau de envolvimento cardíaco para diagnosticar e medir o grau de envolvimento cardíaco em pacientes com amiloidose para exame de RMC. Sugere-se: ● Mapamento T1 e medição do volume extracelular para RMC para diagnosticar a amiloidose precocemente. ● Medir o peptídeo natriurético do tipo B para rastrear e diagnosticar a amiloidose cardíaca. ● Cintilografia com pirofosfato para fazer um diagnóstico preliminar de pacientes com suspeita de amiloidose cardíaca, de modo a distinguir ATTR (positivo) de outros pacientes. Palavras chave: amiloidose; diagnóstico; amiloidose de cadeia leve de imunoglobulina; amiloidose familiar.Fil: Posadas Martinez, Maria Lourdes. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Medicina Traslacional e Ingeniería Biomédica - Hospital Italiano. Instituto de Medicina Traslacional e Ingeniería Biomédica.- Instituto Universitario Hospital Italiano de Buenos Aires. Instituto de Medicina Traslacional e Ingeniería Biomédica; ArgentinaFil: Nucifora, Elsa Mercedes. Hospital Italiano. Departamento de Medicina. Servicio de Clínica Médica; ArgentinaFil: Belziti, César. Hospital Italiano. Departamento de Medicina. Servicio de Clínica Médica; ArgentinaFil: Auteri, Miguel Angel. Clínica Giuliani Charata; ArgentinaFil: Aguirre, Maria Adela. Hospital Italiano. Departamento de Medicina. Servicio de Clínica Médica; ArgentinaFil: Pitzus, Ariel Edgardo. Clínica Giuliani Charata; ArgentinaFil: Dragonetti, Laura. Hospital Aleman; ArgentinaFil: Perez de Arenaza, Diego. Hospital Italiano; ArgentinaFil: Peuchot, Verónica. Hospital Italiano. Departamento de Medicina. Servicio de Clínica Médica; Argentin