6 research outputs found
Editorial
Editorial Revista ION 34(2) - 202
Editorial
Editorial Revista ION 34(1) - 202
Alternatives de rupture d'une émulsion cationique par hétérofloculation ou par changement de pH
Two cationic model emulsions are contacted with a solid having a negative-charged surface and with a caustic soda solution. In one hand, emulsions stabilized by a quaternary ammonium are contacted with Fontainebleau sandstone, as a consequence, a viscosity reduction of the remaining emulsion is observed, as well as the emulsion break-up through a heteroflocculation mechanism provided the solid surface is large enough. Results show that the dispersed oil fraction decreases after addition of sandstone aliquots, and this depends on the concentration of surfactant in the continuous phase of the emulsion. As the droplet size and distribution remain constant during the process, it is assumed that the emulsion heteroflocculation is the result of direct oil droplets adhesion on the sand surface, followed by their coalescence around the sand particles. On the other hand, when an alkali solution is added to a model cationic oil-in-water emulsion, chemical equilibrium is rapidly affected. The effective droplets volume decreases and rheological behavior which firstly exhibits a shear-thinning behavior becomes gradually Newtonian. The abrupt emulsion destabilization by pH increase is the result of droplets coalescence as a consequence of electrostatic repulsions disappearance among droplets. The surfactant adsorption at the liquid-liquid interface changes, the optimal formulation is reached and emulsion becomes unstable. After all, the emulsion morphology, stability and even emulsion inversion are all controlled by pH. Emulsion destabilization can be studied by a rheological monitoring process but it is hardly recommended keep in mind all physicochemical phenomena if this method is not strictly controlledDeux émulsions cationiques modèles sont mises au contact avec un solide présentant une charge superficielle négative et avec une solution alcaline. Premièrement, lorsque des quantités déterminées de sable de Fontainebleau sont ajoutées sur une émulsion stabilisée par un ammonium quaternaire, la viscosité des émulsions résiduelles diminue avec l'addition de sable et l'hétérofloculation a lieu si nous ajoutons suffisamment de sable. Les résultats montrent que la concentration de la phase dispersée diminue et le processus dépends de la concentration de tensioactif dans la phase continue de l'émulsion. Etant donné que ni la taille des gouttes ni la distribution ne changent pendant l'addition des solides, nous proposons l'adsorption directe des gouttes sur la surface minérale, suivie par leur coalescence sur les particules de sable. Par ailleurs, lorsqu'une solution alcaline est rajoutée sur une émulsion stabilisée par une amine, l'équilibre chimique est rapidement perturbé. L'addition de NaOH implique la production d'amine, le volume effectif des gouttes diminue et le comportement rhéologique des émulsions évolue de rhéofluidifiant à Newtonien. La déstabilisation résultant de la remontée de pH est due à la coalescence des gouttes à cause de la déprotonation du tensioactif. La formulation interfaciale évolue à chaque addition de la solution alcaline et le système bascule vers la production d'une microémulsion très instable. Les conditions pour la déstabilisation des émulsions peuvent être optimisées par un suivi rhéologique, mais il est fondamental de tenir compte des diverses possibilités pouvant se présenter si le processus n'est pas contrôlé strictemen
Cationic emulsions breaking alternatives by heteroflocculation or by pH increase
Deux émulsions cationiques modèles sont mises au contact avec un solide présentant une charge superficielle négative et avec une solution alcaline. Premièrement, lorsque des quantités déterminées de sable de Fontainebleau sont ajoutées sur une émulsion stabilisée par un ammonium quaternaire, la viscosité des émulsions résiduelles diminue avec l'addition de sable et l'hétérofloculation a lieu si nous ajoutons suffisamment de sable. Les résultats montrent que la concentration de la phase dispersée diminue et le processus dépends de la concentration de tensioactif dans la phase continue de l'émulsion. Etant donné que ni la taille des gouttes ni la distribution ne changent pendant l'addition des solides, nous proposons l'adsorption directe des gouttes sur la surface minérale, suivie par leur coalescence sur les particules de sable. Par ailleurs, lorsqu'une solution alcaline est rajoutée sur une émulsion stabilisée par une amine, l'équilibre chimique est rapidement perturbé. L'addition de NaOH implique la production d'amine, le volume effectif des gouttes diminue et le comportement rhéologique des émulsions évolue de rhéofluidifiant à Newtonien. La déstabilisation résultant de la remontée de pH est due à la coalescence des gouttes à cause de la déprotonation du tensioactif. La formulation interfaciale évolue à chaque addition de la solution alcaline et le système bascule vers la production d'une microémulsion très instable. Les conditions pour la déstabilisation des émulsions peuvent être optimisées par un suivi rhéologique, mais il est fondamental de tenir compte des diverses possibilités pouvant se présenter si le processus n'est pas contrôlé strictementTwo cationic model emulsions are contacted with a solid having a negative-charged surface and with a caustic soda solution. In one hand, emulsions stabilized by a quaternary ammonium are contacted with Fontainebleau sandstone, as a consequence, a viscosity reduction of the remaining emulsion is observed, as well as the emulsion break-up through a heteroflocculation mechanism provided the solid surface is large enough. Results show that the dispersed oil fraction decreases after addition of sandstone aliquots, and this depends on the concentration of surfactant in the continuous phase of the emulsion. As the droplet size and distribution remain constant during the process, it is assumed that the emulsion heteroflocculation is the result of direct oil droplets adhesion on the sand surface, followed by their coalescence around the sand particles. On the other hand, when an alkali solution is added to a model cationic oil-in-water emulsion, chemical equilibrium is rapidly affected. The effective droplets volume decreases and rheological behavior which firstly exhibits a shear-thinning behavior becomes gradually Newtonian. The abrupt emulsion destabilization by pH increase is the result of droplets coalescence as a consequence of electrostatic repulsions disappearance among droplets. The surfactant adsorption at the liquid-liquid interface changes, the optimal formulation is reached and emulsion becomes unstable. After all, the emulsion morphology, stability and even emulsion inversion are all controlled by pH. Emulsion destabilization can be studied by a rheological monitoring process but it is hardly recommended keep in mind all physicochemical phenomena if this method is not strictly controlle
Alternatives de rupture d'une émulsion cationique par hétérofloculation ou par changement de pH
Deux émulsions cationiques modèles sont mises au contact avec un solide présentant une charge superficielle négative et avec une solution alcaline. Premièrement, lorsque des quantités déterminées de sable de Fontainebleau sont ajoutées sur une émulsion stabilisée par un ammonium quaternaire, la viscosité des émulsions résiduelles diminue avec l'addition de sable et l'hétérofloculation a lieu si nous ajoutons suffisamment de sable. Les résultats montrent que la concentration de la phase dispersée diminue et le processus dépends de la concentration de tensioactif dans la phase continue de l'émulsion. Etant donné que ni la taille des gouttes ni la distribution ne changent pendant l'addition des solides, nous proposons l'adsorption directe des gouttes sur la surface minérale, suivie par leur coalescence sur les particules de sable. Par ailleurs, lorsqu'une solution alcaline est rajoutée sur une émulsion stabilisée par une amine, l'équilibre chimique est rapidement perturbé. L'addition de NaOH implique la production d'amine, le volume effectif des gouttes diminue et le comportement rhéologique des émulsions évolue de rhéofluidifiant à Newtonien. La déstabilisation résultant de la remontée de pH est due à la coalescence des gouttes à cause de la déprotonation du tensioactif. La formulation interfaciale évolue à chaque addition de la solution alcaline et le système bascule vers la production d'une microémulsion très instable. Les conditions pour la déstabilisation des émulsions peuvent être optimisées par un suivi rhéologique, mais il est fondamental de tenir compte des diverses possibilités pouvant se présenter si le processus n'est pas contrôlé strictementTwo cationic model emulsions are contacted with a solid having a negative-charged surface and with a caustic soda solution. In one hand, emulsions stabilized by a quaternary ammonium are contacted with Fontainebleau sandstone, as a consequence, a viscosity reduction of the remaining emulsion is observed, as well as the emulsion break-up through a heteroflocculation mechanism provided the solid surface is large enough. Results show that the dispersed oil fraction decreases after addition of sandstone aliquots, and this depends on the concentration of surfactant in the continuous phase of the emulsion. As the droplet size and distribution remain constant during the process, it is assumed that the emulsion heteroflocculation is the result of direct oil droplets adhesion on the sand surface, followed by their coalescence around the sand particles. On the other hand, when an alkali solution is added to a model cationic oil-in-water emulsion, chemical equilibrium is rapidly affected. The effective droplets volume decreases and rheological behavior which firstly exhibits a shear-thinning behavior becomes gradually Newtonian. The abrupt emulsion destabilization by pH increase is the result of droplets coalescence as a consequence of electrostatic repulsions disappearance among droplets. The surfactant adsorption at the liquid-liquid interface changes, the optimal formulation is reached and emulsion becomes unstable. After all, the emulsion morphology, stability and even emulsion inversion are all controlled by pH. Emulsion destabilization can be studied by a rheological monitoring process but it is hardly recommended keep in mind all physicochemical phenomena if this method is not strictly controlledMETZ-SCD (574632105) / SudocNANCY1-Bib. numérique (543959902) / SudocNANCY2-Bibliotheque electronique (543959901) / SudocNANCY-INPL-Bib. électronique (545479901) / SudocSudocFranceF
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Effects of pre-operative isolation on postoperative pulmonary complications after elective surgery: an international prospective cohort study an international prospective cohort study
We aimed to determine the impact of pre-operative isolation on postoperative pulmonary complications after elective surgery during the global SARS-CoV-2 pandemic. We performed an international prospective cohort study including patients undergoing elective surgery in October 2020. Isolation was defined as the period before surgery during which patients did not leave their house or receive visitors from outside their household. The primary outcome was postoperative pulmonary complications, adjusted in multivariable models for measured confounders. Pre-defined sub-group analyses were performed for the primary outcome. A total of 96,454 patients from 114 countries were included and overall, 26,948 (27.9%) patients isolated before surgery. Postoperative pulmonary complications were recorded in 1947 (2.0%) patients of which 227 (11.7%) were associated with SARS-CoV-2 infection. Patients who isolated pre-operatively were older, had more respiratory comorbidities and were more commonly from areas of high SARS-CoV-2 incidence and high-income countries. Although the overall rates of postoperative pulmonary complications were similar in those that isolated and those that did not (2.1% vs 2.0%, respectively), isolation was associated with higher rates of postoperative pulmonary complications after adjustment (adjusted OR 1.20, 95%CI 1.05–1.36, p = 0.005). Sensitivity analyses revealed no further differences when patients were categorised by: pre-operative testing; use of COVID-19-free pathways; or community SARS-CoV-2 prevalence. The rate of postoperative pulmonary complications increased with periods of isolation longer than 3 days, with an OR (95%CI) at 4–7 days or ≥ 8 days of 1.25 (1.04–1.48), p = 0.015 and 1.31 (1.11–1.55), p = 0.001, respectively. Isolation before elective surgery might be associated with a small but clinically important increased risk of postoperative pulmonary complications. Longer periods of isolation showed no reduction in the risk of postoperative pulmonary complications. These findings have significant implications for global provision of elective surgical care. We aimed to determine the impact of pre-operative isolation on postoperative pulmonary complications after elective surgery during the global SARS-CoV-2 pandemic. We performed an international prospective cohort study including patients undergoing elective surgery in October 2020. Isolation was defined as the period before surgery during which patients did not leave their house or receive visitors from outside their household. The primary outcome was postoperative pulmonary complications, adjusted in multivariable models for measured confounders. Pre-defined sub-group analyses were performed for the primary outcome. A total of 96,454 patients from 114 countries were included and overall, 26,948 (27.9%) patients isolated before surgery. Postoperative pulmonary complications were recorded in 1947 (2.0%) patients of which 227 (11.7%) were associated with SARS-CoV-2 infection. Patients who isolated pre-operatively were older, had more respiratory comorbidities and were more commonly from areas of high SARS-CoV-2 incidence and high-income countries. Although the overall rates of postoperative pulmonary complications were similar in those that isolated and those that did not (2.1% vs 2.0%, respectively), isolation was associated with higher rates of postoperative pulmonary complications after adjustment (adjusted OR 1.20, 95%CI 1.05–1.36, p = 0.005). Sensitivity analyses revealed no further differences when patients were categorised by: pre-operative testing; use of COVID-19-free pathways; or community SARS-CoV-2 prevalence. The rate of postoperative pulmonary complications increased with periods of isolation longer than 3 days, with an OR (95%CI) at 4–7 days or ≥ 8 days of 1.25 (1.04–1.48), p = 0.015 and 1.31 (1.11–1.55), p = 0.001, respectively. Isolation before elective surgery might be associated with a small but clinically important increased risk of postoperative pulmonary complications. Longer periods of isolation showed no reduction in the risk of postoperative pulmonary complications. These findings have significant implications for global provision of elective surgical care