Enhanced bio-recalcitrant organics removal by combined adsorption and ozonation

Removal of bio-recalcitrant and toxic compounds from wastewaters has been a major objective of industrial manufacturers for a few years. Due to the potential risk toward public health,regulations are becoming increasingly strict and classical treatments like biological treatments are not efficient. Other techniques such as incineration, oxidation or adsorption provide higher levels of removal but with a high energy and capital cost. A coupled process involving adsorption and oxidation is studied. Four adsorbents are tested and compared according to two objectives,their adsorption capacity and their capability to decompose ozone into powerful hydroxyl radicals. Two model compounds were chosen: 2,4-dichlorophenol and nitrobenzene.Experimental results allow comparing coupled process with results obtained during ozonation alone. Zeolite (Faujasite Y) gave disappointing results in term of both adsorption kinetics and ozone decomposition. On the contrary, activated carbons showed fast adsorptions and important capabilites to decompose ozone into radicals, almost in nitrobenzene experiments. S-23 activated carbon proved to be the most interesting adsorbent for better mechanical and chemical stabilities over time. Sequential adsorption/ozonation experiments were conducted,showing a strong loss of adsorption efficiency after the first operation, but the positive point is that the adsorption capacity remains almost constant during further cycles

The use of ozone and high silica zeolites to enhance refractory compounds removal

This work investigates the removal of organic pollutants from water through a three-phase process combining adsorption onto hydrophobic zeolites and in situ oxidation by ozone gas. Zeolites are aluminosilicates with various crystalline structures – and especially different pore sizes - which offer a great selectivity, profitable to organic pollutants separation in a complex matrix like natural water. They are highly resistant to chemical agents as acids, bases or oxidising agents such as ozone. Moreover, high silica zeolites have a high adsorption capacity for organics. Ozone is known to be a powerful oxidising agent able to react with various organic compounds. Its action – either direct or indirect - leads to the decomposition of organics into smaller molecules that are generally biodegradable. Previous studies have shown that organics adsorbed onto zeolites could be oxidised by ozonated water faster than in bulk water because of a micropore concentration effect (Fujita et al, 2004 and Sagehashi et al, 2005). In the gas phase, Monneyron et al (2003) showed that high silica zeolites could catalyse ozone decomposition into radical species and that adsorption properties were not significantly modified after exposition to ozone. Hence it is expected that zeolites saturated with organics could undergo regeneration by ozone without degradation of their structures or decrease of their adsorption capacities. The present work showed that high silica zeolites could efficiently adsorb nitrobenzene from water although their capacity stayed beyond that of activated carbon, except at low concentrations. The adsorption capacity depended on the zeolite structure and the Si/Al ratio. Adsorption isotherms could be well described by Langmuir or Freundlich models. As regards the three phase coupled process, the adsorbent could be efficiently regenerated during an ozonation step consisting in bubbling ozone through a suspension of saturated zeolite in a nitrobenzene solution at equilibrium. The initial adsorption capacity was quickly recovered and, continuing the treatment, the adsorption capacity of the zeolite was even increased. This may be due to the cleaning of zeolites pores by ozone (Pic et al, 2005). Yet traces of template molecules could probably remain from the zeolite synthesis process. Until now the catalytic effect of the zeolites has not been evidenced in the liquid phase. Therefore future work will focus on the conditions in which the oxidation kinetics can be enhanced in the presence of zeolites through a concentration effect, and to what extent

Fluid phase equilibria of the reacting mixture in the dimethyl carbonate synthesis from supercritical CO2

In order to investigate the dimethyl carbonate synthesis from methanol and supercritical CO2, the thermodynamic behaviour of the reacting mixture, i.e. the quaternary methanol/CO2/DMC/water mixture, has to be known. The SRK equation of state with MHV2 mixing rules has been chosen to predict fluid phase equilibria in the reactor. The first part of this work is dedicated to the determination of binary interaction parameters, needed in the use of this model. These parameters are deduced from the fitting of experimental data concerning binary or ternary sub-systems existing in the quaternary mixture. Literature data was used for most of the binary sub-systems, but for the DMC/CO2 and DMC/water mixtures, specific experiments were carried out. The agreement between experimental and predicted fluid phase equilibria was found to be satisfactory. With a view to studying of the operating conditions for the reaction, the thermodynamic model was used to predict fluid phase equilibria in the reactor, by considering several hypothetical feed ratios and conversions. This work shows that CO2 has to be used in large excess in order to be sure of running the reaction in a homogeneous fluid medium

Influence of activated carbons on the kinetics and mechanisms of aromatic molecules ozonation

Companies have been looking for new methods for treating toxic or refractory wastewaters; which can mainly be used prior to or after or in connexion with biological treatment processes.This paper compares conventional ozone oxidation with activatedcarbon (AC) promoted ozone oxidation, which helps developing a mechanism involving HOradical dot radical. For a compound which is quite easy to oxidise, like 2,4-dichlorophenol (2,4-DCP) conventional ozonation is efficient enough to remove the initial molecule. The mechanism involved mainly consists of an electrophilic attack on the aromatic ring, which is activated by the donor effect of the –OH group, then followed by a 1,3 dipolar cycloaddition (Criegee mechanism) that leads to aliphatic species, mainly carboxylic acids. Yet, the addition of AC, through the presence of HOradical dot radical, enhances the removal of these species which are more refractory.For a refractory compound like nitrobenzene (NB), with a de-activatedaromatic ring because of the attractive effect of –NO2, conventional ozonation is inefficient. On the contrary, this molecule can be quite easily removed with AC promoted oxidation and it is found that the mechanism (electrophilic attack followed by a 1,3 dipolar cycloaddition) is quite similar to the one corresponding to conventional ozonation, but with less selectivity.For both molecules, a mass balance has established that the by-products accounting for more than 75% of the remaining COD can be quantified. A significant part is composed of carboxylic acids (acetic, oxalic, etc.), which could afterwards be easily removed in an industrial wastewater treatment process followed by a final biological treatment step

Adsorption of Nitrobenzene from Water onto High Silica Zeolites and Regeneration by Ozone

This work investigates the removal of nitrobenzene (NB), a model pollutant from water, by combining adsorption onto zeolites and regeneration with ozone. The adsorption equilibrium isotherms of NB onto zeolites enabled the best adsorbent to be selected and zeolites with a high Si/Al ratio were the most efficient. The adsorption capacity depended on the Si/Al ratio and on the pore size. In a sequential process coupling adsorption and oxidation by ozone, NB was completely removed from water and the initial adsorption capacity of the zeolite was totally restored. Although no catalytic effect was noticed, the adsorption produced locally high concentrations, thus enhancing the oxidation rate for NB

Regulando la coalianza en un juego motor de tríada

The ambivalence of the motor triad provides a social relationship which challenges the established games order. We start from the principle that the practice of the few existing triad motor games not always make the students experience the paradox from a decision-taking point of view. This is so because of the activity speed and the fact that players are aware of their co-alliance actions. The ‘allied ball’ game regulates this paradoxical situation and makes it clear for all players. In addition, it rebalances the antagonism with respect to solidarity, acting in favour of the latter. Communication in the proposed motor games is analyzed and a justification for the lack of focus on the problem of ambivalence is also given, together with solutions to that problem. The ‘allied ball’ game offers pedagogical advantages, such as helping to perceive in a clear way the paradoxical situation and the symbolic value of the ambivalence during its practice; from a curricular point of view, it shows a distinct contribution in comparison to other games and sports.La ambivalencia de la tríada motriz aporta un patrón de relación social que pone en entredicho el orden establecido en los juegos. Se parte del problema de que la práctica de los pocos juegos motores de tríada no siempre consigue en el alumnado vivenciar la paradoja desde el punto de vista decisional, debido a la rapidez de las acciones y a ser consciente el jugador de su acción de coalianza. El juego ‘pelota aliada’ regula la situación paradójica y la hace evidente para los jugadores; además, lo hace reequilibrando el antagonismo respecto a la solidaridad a favor de esta última. Se analiza la comunicación motriz del juego propuesto, y se justifica por qué hay una falta de enfoque respecto al problema de la ambivalencia, señalando soluciones. La aportación del juego ‘pelota aliada’ guarda ventajas pedagógicas, como ayudar a hacer consciente en la práctica la situación paradójica mediante la regla; desde el punto de vista curricular, muestra su aportación diferencial respecto a otros juegos y deportes

Triad communication and specificity of motor games

Se estudian las tríadas desde la comunicación motriz, con el propósito de a) identificar los distintos tipos a que da lugar la tríada; b) medir las diferencias entre los tipos de tríadas estudiados; y c) mostrar con juegos concretos la viabilidad de los juegos de tríada trasladables a programas. Se justifican 13 tipos susceptibles de ser viables como juegos motores, que corresponden a tríadas completas y a tríadas con ausencia de una conexión entre dos de sus nodos. Se comparan cuatro juegos por medio de cinco indicadores: roles, interacción intragrupo, interacción intergrupos, emisiones o recepciones, y valencia positiva o negativa. La comparación evidencia el comportamiento específico de las tríadas motrices. Los resultados confirman la viabilidad de los juegos estudiados, y las diferencias relativas entre antagonismo y solidaridad. Los juegos motores de tríada son una fuente singular de comunicación motriz y una alternativa pedagógica para los programas de juegosTriads are studied from a motor communication point of view. Our study is aimed at a) identifying the various type that triads originate; b) measuring the differences among the type of the studied triads; and c) showing with specific examples the feasibility of triad games transferred to programs. 13 types are justified as being likely feasible as motor games. They correspond to complete triads and to triads with one missing connection between two of its nodes. Four games are compared through five different proxies: roles, intra-group interaction, interaction among groups, emissions and receptions, and positive or negative valence. The comparison demonstrates the specific behavior of motor triads. The results confirm the feasibility of the studied games and the relative differences between rivalry and solidarity. Motor games with a triad structure are a singular source of communication and a pedagogic alternative for game program

La observación de diferencias de género en balonmano

Superar una mirada superficial en relación al género en balonmano, mediante la identificación de diferencias entre chicas y chicos en competiciones de alto nivel es objetivo del presente trabajo. Sobre qué variables o criterios (lanzamientos, efectividad, espacio y señalizaciones arbitrales) y categorías observacionales descansan estas diferencias resulta esencial para poder identificar comportamientos estratégicos. Se recurrió a una metodología observacional para registrar los eventos del juego. Fueron seleccionados dos partidos de balonmano femenino y dos partidos masculinos, pertenecientes a las fases finales de los juegos olímpicos de Londres 2012. El diseño observacional fue nomotético, puntual y multidimensional. Se diseñó una herramienta ‘ad hoc’, puesta en práctica por dos evaluadores. Una vez fueron registrados los datos mediante el software Lince, fueron analizados mediante la técnica de reducción de datos Theme. Los resultados evidenciaron la existencia T-patterns en función del género.Overcoming a superficial view regarding the gender in handball, through the identification of differences between women and men in high level competitions is the objective of this work. Knowing on which observational variables or criteria (throwing, effectiveness, zone and referee signs) and categories these differences rely is essential for identifying strategic behaviors. An observational methodology was used to record the events of the game. Two women's and two men's handball matches were selected, belonging to the final phases of the London 2012 Olympic Games. The observational design was nomothetic, punctual and multidimensional. An ‘ad hoc’ tool was designed, and it was implemented by two evaluators. Once the data were recorded using the Lince software, they were analyzed through the data reduction technique Theme. The results evidenced the existence of T-patterns based on gender.peerReviewe

Oxidation of nitrobenzene by ozone in the presence of faujasite zeolite in a continuous flow gas–liquid–solid reactor

This work investigates the oxidation of nitrobenzene (NB) by ozone in the presence of faujasite zeolite. Experiments were carried out in a gas–liquid–solid reactor were ozone transfer and NB oxidation took place at the same time. Three configurations of the reactor were compared: empty, filled with inert glass beads and filled with faujasite pellets. First, ozone transfer coefficient (kLa) and decomposition rate constant (kC) were determined for each configuration. In presence of solid, kLa was 2.0 to 2.6 times higher and kC was 5.0 to 6.4 times higher compared to the empty reactor. Then, the various configurations were evaluated in terms of NB removal and chemical oxygen demand (COD) decrease. The faujasite reactor showed higher removal of NB and decrease of COD compared to other configurations under the same conditions suggesting that the faujasite increases the oxidation rate of NB. Oxidation of NB in presence of faujasite also proved to be limited by the transfer of ozone from the gas to the liquid phase

Role of Lewis acid sites of ZSM-5 zeolite on gaseous ozone abatement

In this work, chemical interactions between ozone and zeolite surface active sites are studied in order to propose a process for gaseous ozone removal. Synthetic ZSM-5 zeolites with three different Si/Al2 ratios and similar specific surface areas and microporous volumes were used in this study. Zeolite samples were characterised using Fourier Transform InfraRed spectroscopy (FTIR) and pyridine sorption IR studies in order to determine acidic site concentrations and strength. Ozone removal experiments were conducted in a quartz fixed-bed flow reactor, at 20°C and 101 kPa. Experiments using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) were conducted in order to identify adsorbed ozone and/or adsorbed oxygen species on zeolite surface. Pyridine IR measurements evidence two kinds of Lewis acid sites induced by extra-framework aluminium species and electronic aluminium defaults inside zeolite structure. Results obtained here evidence the important role of acidic surface sites of ZSM-5 zeolite on gaseous ozone removal. The total amount of removed ozone is found to be directly proportional to the total content of Lewis acid sites. DRIFTS experiments exhibit two bands around 800 and 1400 cm-1 that could correspond to adsorbed oxygen species linked to zeolite surface. DRIFTS experiments also exhibit a band around 1100 cm-1 that correspond to adsorbed ozone on the zeolite surface. Gaseous ozone removal using ZSM-5 zeolite could be largely attributed to ozone decomposition on Lewis acid sites and also to ozone adsorption on the surface of the zeolites