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Papers by benoit lefevre

Process for making a solid compound by precipitation, suspensions of solid in liquids and solids obtained by the process and their use as additives

Desalination and Water Treatment, 2015

Membrane fouling is an inherent phenomenon in UF membrane processes, making it necessary to perio... more Membrane fouling is an inherent phenomenon in UF membrane processes, making it necessary to periodically perform backwashes (BW) and chemical "cleanings in place" (CIP) to restore the initial permeability of the membrane. The objective of this study was 1) to explore systematically the effect of distinct BW-related variables (BW transmembrane pressure, duration, frequency, composition) on the reversibility of UF membrane fouling and on the permeate quality (in terms of total organic carbon, turbidity and UV absorbance) over successive filtration/BW cycles; and 2) to identify which organic fractions were most removed by the membrane and, of these, which were most detached after BW, alkaline and oxidant CIP and acid CIP episodes. For this purpose, a bench-scale outside-in hollow fibre module operated under dead-end filtration mode at constant transmembrane pressure and treating settled water from a drinking water treatment plant was employed. Dissolved organic carbon fractionation was performed by high performance size exclusion chromatography (HPSEC). Results showed that in general the more intensive a BW was (in terms of high transmembrane pressure, shortened frequency and prolonged duration) the more effective it was in removing fouling from the membrane. Concerning the composition of the water used for the BW, the addition of NaClO led to maximum fouling reversibility, closely followed by the combination of NaOH+NaClO, while citric acid and NaOH contributed little compared to water alone. However, results also showed that irreversible fouling was never completely avoided whatever the BW regime applied, leading to a gradual increase of the total resistance over time. Larger

Intrusion-extrusion d'eau dans les polym�res m�soporeux hydrophobes

Dissipative forced intrusion of water in hydrophobic porous silica: A new field of applications for MCM-41 type materials

Recently microporous and mesoporous materials were found to be particularly suitable for a new ty... more Recently microporous and mesoporous materials were found to be particularly suitable for a new type of applications in the mechanical field. This paper reports experimental features about the dissipative forced intrusion of water in highly hydrophobic mesoporous materials: this phenomenon can be used to develop a new type of dampers and/or actuators. Silica-based materials behavior was investigated. Among them, MCM-41 exhibit original and interesting properties towards the potential developments of dampers and appear to be of great interest for the comprehension of energy dissipation mechanisms.

Distribution of dissolved organic matter fractions along several stages of a drinking water treatment plant

Journal of Water Process Engineering, 2015

ABSTRACT The present study was conducted to track dissolved organic carbon (DOC) through the diff... more ABSTRACT The present study was conducted to track dissolved organic carbon (DOC) through the different stages of a drinking water treatment plant that includes a conventional treatment CT (coagulation/flocculation, sedimentation and sand filtration) and two parallel advanced treatments consisting of ozonation plus activated carbon filtration (AT1) and ultrafiltration (UF) and reverse osmosis (RO) (AT2), respectively. Fractionation of DOC was performed by high-performance size exclusion chromatography (HPSEC), whereby DOC fractions are separated according to their molecular weight. Results demonstrated that the dominant fraction in the raw feed water was constituted by humic substances (HS) (28–54%), followed by the fractions building blocks (BB) and low molecular weight neutrals (LMWN) (20–25%). The fraction with highest molecular weight constituted by biopolymers (BP) was found in the range 4–8%. These fractions exhibited different treatability along the treatment units. High molecular weight compounds (fractions BP and HS) were more effectively removed by CT than low molecular weight compounds (fractions BB and LMWN), which were better removed by AT1 and AT2 than CT. Differences in DOC fractions removal were also observed between AT1 and AT2. The passage through AT1 led to a decrease of BP and HS during ozonation, in opposition to BB and LMWN, which were removed to a greater extent during GAC filtration. In AT2, BP was removed by UF and RO, while HS, BB and LMWN were marginally removed by UF but largely by RO. Backwash stream water from UF membranes was also analysed to provide insight into the fouling reversibility of DOC fractions.

Intrusion-extrusion d'eau dans les polymères mésoporeux hydrophobes

Revue des composites et des matériaux avancés, 2004

Journal of Water Reuse and Desalination, 2012

Wastewater reclamation contributes to the preservation of conventional water resources and thus h... more Wastewater reclamation contributes to the preservation of conventional water resources and thus helps to ensure appropriate human development for future generations. Wastewater reclamation can be achieved through several technologies. One of the most common technologies is the tertiary treatment of urban municipal wastewater, which is often based on membrane technologies. Reverse osmosis is an effective separation technology for removing dissolved salts and low molecular weight organic compounds. However, membranes suffer from fouling, which directly reduces technical, environmental and economic feasibility of the process and hence of the reclamation plant. One of the strategies helpful to reduce fouling is the optimisation of the membranes' cleaning and maintenance. The aim of this work is to test the impact of the membrane cleaning protocol design on the recovery of the original properties of a reverse osmosis membrane used for several years in a wastewater reclamation plant in Spain. Furthermore, the work is focused on the validation of the adequacy of the most-common indicators used for assessing membranes' cleaning efficiency.

Fractionation and removal of dissolved organic carbon in a full-scale granular activated carbon filter used for drinking water production

Water Research, 2013

The removal of natural organic matter (NOM) and, more particularly, its individual fractions by t... more The removal of natural organic matter (NOM) and, more particularly, its individual fractions by two different GACs was investigated in full-scale filters in a drinking water treatment plant (DWTP). Fractionation of NOM was performed by high performance size exclusion chromatography (HPSEC) into biopolymers, humic substances, building blocks and low molecular weight organics. The sorption capacity of GAC in terms of iodine number (IN) and apparent surface area (SBET), as well as the filling of narrow- and super-microporosity were monitored over the 1-year operation of the filters. Both GACs demonstrated to be effective at removing NOM over a wide range of fractions, especially the low and intermediate molecular weight fractions. TOC removal initially occurred via adsorption, and smaller (lighter) fractions were more removed as they could enter and diffuse more easily through the pores of the adsorbent. As time progressed, biodegradation also played a role in the TOC removal, and lighter fractions continued to be preferentially removed due to their higher biodegradability. The gained knowledge would assist drinking water utilities in selecting a proper GAC for the removal of NOM from water and, therefore, complying more successfully the latest water regulations.

Characterising biofilm development on granular activated carbon used for drinking water production

Water Research, 2013

Under normal operation conditions, granular activated carbon (GAC) employed in drinking water tre... more Under normal operation conditions, granular activated carbon (GAC) employed in drinking water treatment plants (DWTPs) for natural organic matter (NOM) removal can be colonised by microorganisms which can eventually establish active biofilms. The formation of such biofilms can contribute to NOM removal by biodegradation, but also in clogging phenomena that can make necessary more frequent backwashes. Biofilm occurrence and evolution under full-scale-like conditions (i.e. including periodic backwashing) are still uncertain, and GAC filtration is usually operated with a strong empirical component. The aim of the present study was to assess the formation and growth, if any, of biofilm in a periodically backwashed GAC filter. For this purpose, an on-site pilot plant was assembled and operated to closely mimic the GAC filters installed in the DWTP in Sant Joan Despí (Barcelona, Spain). The study comprised a monitoring of both water and GAC cores withdrawn at various depths and times throughout 1 year operation. The biomass parameters assessed were total cell count by confocal laser scanning microscopy (CLSM), DNA and adenosine triphosphate (ATP). Visual examination of GAC particles was also conducted by high-resolution field emission scanning electron microscopy (FESEM). Additionally, water quality and GAC surface properties were monitored. Results provided insight into the extent and spatial distribution of biofilm within the GAC bed. To sum up, it was found that backwashing could physically detach bacteria from the biofilm, which could however build back up to its pre-backwashing concentration before next backwashing cycle.

Journal of Physical Chemistry C, 2008

MCM-41 and SBA-15 micelle-templated silicas are ideal reference materials to study the effect of ... more MCM-41 and SBA-15 micelle-templated silicas are ideal reference materials to study the effect of surface roughness on pore size measurement by mercury intrusion, as the inner surface of the mesoporous channels is much rougher in the case of SBA-15 than MCM-41. In the case of MCM-41, the pressure of mercury intrusion is related to the pore size by the classical Washburn-Laplace law, while in the case of SBA-15, the pressure of intrusion is much higher than expected and classical models underevaluate the size of the channels. Defects on the pore surface of SBA-15 affect the mercury intrusion in a similar way as the deviation from cylindrical geometry does for the pores of spongelike silica glasses. The results vindicate the models of Wenzel and Kloubek on the effect of surface defects on the mercury contact angle, which is significantly larger for a rough surface than for a plane surface. The surface defects of SBA-15 does not affect the evaluation of the mesopore size by nitrogen adsorption, as they are filled at an early stage of the adsorption and do not interfere with capillary condensation.

DESALINATION AND WATER TREATMENT, 2011

Membrane biofouling represents an important drawback in full-scale water reclamation plants as it... more Membrane biofouling represents an important drawback in full-scale water reclamation plants as it affects energy consumption, permeate productivity and even quality. Due to the high number of water-/membrane-/site-specifi c variables affecting membrane fouling and lifetime, cleaning and maintenance procedures need to be specifi cally designed for each application. Cleaning activities cannot directly be optimized onsite due to the necessity of ensuring a constant and safe product water fl ow and quality. For this reason, cleaning optimization needs to be transposed from plant to lab. In this work, a Spanish wastewater reclamation plant was selected to optimize cleaning procedures. For this, a reverse osmosis element was sampled and submitted to several cleaning protocols at lab-scale. The infl uence of the basic cleaning agent nature, pH and presence of additives on cleaning effi ciency was studied. The optimal membrane cleaning conditions were achieved with a NaOH solution at pH 12 containing 0.03% SDS. At these conditions, permeate fl ux after cleaning was two fold greater than fouled membrane permeate fl ux. In this work, lab-scale membrane cleaning tests have shown to be a successful tool to optimize cleaning activities for full-scale plants and understand the infl uence of cleaning variables on membranes restoring effi ciency.

Chemistry of Materials, 2005

The synthesis of large-pore micelle-templated silica (MTS) materials as discrete spheres by pseud... more The synthesis of large-pore micelle-templated silica (MTS) materials as discrete spheres by pseudomorphic synthesis solves the double challenge: enlarging the pore size of MTS beyond the diameter of the micelles and controlling the morphology and the size of the particles. The pseudomorphic transformation of silica beads of the desired size into MTS is one of the more suitable routes to control both nanometric and micrometric scales of MTS synthesis. The most employed method to enlarge pore diameter of MTS synthesized from alkyltrimethylammonium surfactants is to use 1,3,5-trimethylbenzene (TMB) as a swelling agent in the micelles. Unfortunately this method leads to particle aggregation. By means of the pseudomorphic route combining an original set of chemical compositions (C 18 TAB/decane/ TMB/NaI), under mild conditions (low temperature, without autoclaving), we successfully synthesized nonaggregated MTS beads of 10 µm with pore diameter ranging from 7 to 9 nm, 900 m 2 /g specific surface area, and 1.5 mL/g pore volume. To accommodate the large pore volume developed by largepore MTS, highly porous silica beads of 10 µm and 300 m 2 /g specific surface area have previously been synthesized by means of an emulsion/polymerization procedure. The control at nanometric scale, by means of surfactants, leads to improved textural properties compared to optimized silica gels, whereas the control of the micrometric morphology (discrete spheres) makes these supports suitable for column packing and chromatographic evaluation.

Dissipative water intrusion in hydrophobic MCM-41 type materials

Chemical Communications, 2002

Texture-related features of water intrusion in hydrophobised MCM-41 silicas render these material... more Texture-related features of water intrusion in hydrophobised MCM-41 silicas render these materials especially suitable for energy dissipation in mechanical dampers.

MCM-41 silica monoliths with independent control of meso-and macroporosity

New J. Chem., 2007

... a, Julien Iapichellaa, Benoît Lefèvrea, Christine Biolleya, Jean-Pierre Bellatb, François Faj... more ... a, Julien Iapichellaa, Benoît Lefèvrea, Christine Biolleya, Jean-Pierre Bellatb, François Fajulaa and Anne Galarneau*a. a Institut Charles Gerhardt Montpellier-UMR 5253 CNRS/ENSCM/ Matériaux Avancés pour la Catalyse et la Santé, Ecole Nationale Supérieure de Chimie de ...

Understanding of the physics of confined fluids is of major theoretical and practical interest. I... more Understanding of the physics of confined fluids is of major theoretical and practical interest. In the field of materials science, the most popular techniques used to characterise the texture of mesoporous supports are based on the analysis of the properties of a confined fluid:thermoporometry, adsorption technique and mercury intrusion porosimetry. In particular, in the last two techniques the pressure parameter is related to the dimension of the pores. The present study is dedicated to an original analysis of the forced-intrusion of a non-wetting liquid (water) in hydrophobic mesoporous materials presenting different pore topologies. Among these supports, MCM-41 type materials allowed to point out distinct mechanisms for the intrusion and the extrusion of water. Whereas the intrusion process obeys to the Laplace law of capillarity, the extrusion is found to be preferentially governed by the formation of the vapor phase by a mechanism such as nucleation. Therefore, the conventional interpretation given for the hysteresis observed in mercury porosimetry, based on wetting hysteresis and pore-blocking effects is not directly transposable to the case of water intrusion experiments. Data obtained on other supports such as silica gels and Controlled Pore Glass supports are also reported and discussed taking into account the results obtained in MCM-41 type materials. Finally, the mechanisms leading to hysteresis in both phenomena (sorption of a wetting fluid and forced intrusion of a non-wetting liquid) are shown to present strong analogies in model materials as well as in disordered and interconnected porosities.

We present experimental and theoretical results on intrusionextrusion cycles of water in hydropho... more We present experimental and theoretical results on intrusionextrusion cycles of water in hydrophobic mesoporous materials, characterized by independent cylindrical pores. The intrusion, which takes place above the bulk saturation pressure, can be well described using a macroscopic capillary model. Once the material is saturated with water, extrusion takes place upon reduction of the externally applied pressure ; Our results for the extrusion pressure can only be understood by assuming that the limiting extrusion mechanism is the nucleation of a vapour bubble inside the pores. A comparison of calculated and experimental nucleation pressures shows that a proper inclusion of line tension effects is necessary to account for the observed values of nucleation barriers. Negative line tensions of order 10 -11 J.m -1 are found for our system, in reasonable agreement with other experimental estimates of this quantity.

Thermodynamics of wetting: information brought by microcalorimetry

Journal of Petroleum Science and Engineering, 2004

The wetting state of a solid/fluids system depends on the relative value of the surface tensions ... more The wetting state of a solid/fluids system depends on the relative value of the surface tensions acting at the different interfaces. Whereas the free energy of a given solid/fluid interface is not directly measurable, the internal energy part can be relatively easily determined in the case of powders by microcalorimetry. In this paper, the various energy data that can thus

Process for making a solid compound by precipitation, suspensions of solid in liquids and solids obtained by the process and their use as additives

Desalination and Water Treatment, 2015

Membrane fouling is an inherent phenomenon in UF membrane processes, making it necessary to perio... more Membrane fouling is an inherent phenomenon in UF membrane processes, making it necessary to periodically perform backwashes (BW) and chemical "cleanings in place" (CIP) to restore the initial permeability of the membrane. The objective of this study was 1) to explore systematically the effect of distinct BW-related variables (BW transmembrane pressure, duration, frequency, composition) on the reversibility of UF membrane fouling and on the permeate quality (in terms of total organic carbon, turbidity and UV absorbance) over successive filtration/BW cycles; and 2) to identify which organic fractions were most removed by the membrane and, of these, which were most detached after BW, alkaline and oxidant CIP and acid CIP episodes. For this purpose, a bench-scale outside-in hollow fibre module operated under dead-end filtration mode at constant transmembrane pressure and treating settled water from a drinking water treatment plant was employed. Dissolved organic carbon fractionation was performed by high performance size exclusion chromatography (HPSEC). Results showed that in general the more intensive a BW was (in terms of high transmembrane pressure, shortened frequency and prolonged duration) the more effective it was in removing fouling from the membrane. Concerning the composition of the water used for the BW, the addition of NaClO led to maximum fouling reversibility, closely followed by the combination of NaOH+NaClO, while citric acid and NaOH contributed little compared to water alone. However, results also showed that irreversible fouling was never completely avoided whatever the BW regime applied, leading to a gradual increase of the total resistance over time. Larger

Intrusion-extrusion d'eau dans les polym�res m�soporeux hydrophobes

Dissipative forced intrusion of water in hydrophobic porous silica: A new field of applications for MCM-41 type materials

Recently microporous and mesoporous materials were found to be particularly suitable for a new ty... more Recently microporous and mesoporous materials were found to be particularly suitable for a new type of applications in the mechanical field. This paper reports experimental features about the dissipative forced intrusion of water in highly hydrophobic mesoporous materials: this phenomenon can be used to develop a new type of dampers and/or actuators. Silica-based materials behavior was investigated. Among them, MCM-41 exhibit original and interesting properties towards the potential developments of dampers and appear to be of great interest for the comprehension of energy dissipation mechanisms.

Distribution of dissolved organic matter fractions along several stages of a drinking water treatment plant

Journal of Water Process Engineering, 2015

ABSTRACT The present study was conducted to track dissolved organic carbon (DOC) through the diff... more ABSTRACT The present study was conducted to track dissolved organic carbon (DOC) through the different stages of a drinking water treatment plant that includes a conventional treatment CT (coagulation/flocculation, sedimentation and sand filtration) and two parallel advanced treatments consisting of ozonation plus activated carbon filtration (AT1) and ultrafiltration (UF) and reverse osmosis (RO) (AT2), respectively. Fractionation of DOC was performed by high-performance size exclusion chromatography (HPSEC), whereby DOC fractions are separated according to their molecular weight. Results demonstrated that the dominant fraction in the raw feed water was constituted by humic substances (HS) (28–54%), followed by the fractions building blocks (BB) and low molecular weight neutrals (LMWN) (20–25%). The fraction with highest molecular weight constituted by biopolymers (BP) was found in the range 4–8%. These fractions exhibited different treatability along the treatment units. High molecular weight compounds (fractions BP and HS) were more effectively removed by CT than low molecular weight compounds (fractions BB and LMWN), which were better removed by AT1 and AT2 than CT. Differences in DOC fractions removal were also observed between AT1 and AT2. The passage through AT1 led to a decrease of BP and HS during ozonation, in opposition to BB and LMWN, which were removed to a greater extent during GAC filtration. In AT2, BP was removed by UF and RO, while HS, BB and LMWN were marginally removed by UF but largely by RO. Backwash stream water from UF membranes was also analysed to provide insight into the fouling reversibility of DOC fractions.

Intrusion-extrusion d'eau dans les polymères mésoporeux hydrophobes

Revue des composites et des matériaux avancés, 2004

Journal of Water Reuse and Desalination, 2012

Wastewater reclamation contributes to the preservation of conventional water resources and thus h... more Wastewater reclamation contributes to the preservation of conventional water resources and thus helps to ensure appropriate human development for future generations. Wastewater reclamation can be achieved through several technologies. One of the most common technologies is the tertiary treatment of urban municipal wastewater, which is often based on membrane technologies. Reverse osmosis is an effective separation technology for removing dissolved salts and low molecular weight organic compounds. However, membranes suffer from fouling, which directly reduces technical, environmental and economic feasibility of the process and hence of the reclamation plant. One of the strategies helpful to reduce fouling is the optimisation of the membranes' cleaning and maintenance. The aim of this work is to test the impact of the membrane cleaning protocol design on the recovery of the original properties of a reverse osmosis membrane used for several years in a wastewater reclamation plant in Spain. Furthermore, the work is focused on the validation of the adequacy of the most-common indicators used for assessing membranes' cleaning efficiency.

Fractionation and removal of dissolved organic carbon in a full-scale granular activated carbon filter used for drinking water production

Water Research, 2013

The removal of natural organic matter (NOM) and, more particularly, its individual fractions by t... more The removal of natural organic matter (NOM) and, more particularly, its individual fractions by two different GACs was investigated in full-scale filters in a drinking water treatment plant (DWTP). Fractionation of NOM was performed by high performance size exclusion chromatography (HPSEC) into biopolymers, humic substances, building blocks and low molecular weight organics. The sorption capacity of GAC in terms of iodine number (IN) and apparent surface area (SBET), as well as the filling of narrow- and super-microporosity were monitored over the 1-year operation of the filters. Both GACs demonstrated to be effective at removing NOM over a wide range of fractions, especially the low and intermediate molecular weight fractions. TOC removal initially occurred via adsorption, and smaller (lighter) fractions were more removed as they could enter and diffuse more easily through the pores of the adsorbent. As time progressed, biodegradation also played a role in the TOC removal, and lighter fractions continued to be preferentially removed due to their higher biodegradability. The gained knowledge would assist drinking water utilities in selecting a proper GAC for the removal of NOM from water and, therefore, complying more successfully the latest water regulations.

Characterising biofilm development on granular activated carbon used for drinking water production

Water Research, 2013

Under normal operation conditions, granular activated carbon (GAC) employed in drinking water tre... more Under normal operation conditions, granular activated carbon (GAC) employed in drinking water treatment plants (DWTPs) for natural organic matter (NOM) removal can be colonised by microorganisms which can eventually establish active biofilms. The formation of such biofilms can contribute to NOM removal by biodegradation, but also in clogging phenomena that can make necessary more frequent backwashes. Biofilm occurrence and evolution under full-scale-like conditions (i.e. including periodic backwashing) are still uncertain, and GAC filtration is usually operated with a strong empirical component. The aim of the present study was to assess the formation and growth, if any, of biofilm in a periodically backwashed GAC filter. For this purpose, an on-site pilot plant was assembled and operated to closely mimic the GAC filters installed in the DWTP in Sant Joan Despí (Barcelona, Spain). The study comprised a monitoring of both water and GAC cores withdrawn at various depths and times throughout 1 year operation. The biomass parameters assessed were total cell count by confocal laser scanning microscopy (CLSM), DNA and adenosine triphosphate (ATP). Visual examination of GAC particles was also conducted by high-resolution field emission scanning electron microscopy (FESEM). Additionally, water quality and GAC surface properties were monitored. Results provided insight into the extent and spatial distribution of biofilm within the GAC bed. To sum up, it was found that backwashing could physically detach bacteria from the biofilm, which could however build back up to its pre-backwashing concentration before next backwashing cycle.

Journal of Physical Chemistry C, 2008

MCM-41 and SBA-15 micelle-templated silicas are ideal reference materials to study the effect of ... more MCM-41 and SBA-15 micelle-templated silicas are ideal reference materials to study the effect of surface roughness on pore size measurement by mercury intrusion, as the inner surface of the mesoporous channels is much rougher in the case of SBA-15 than MCM-41. In the case of MCM-41, the pressure of mercury intrusion is related to the pore size by the classical Washburn-Laplace law, while in the case of SBA-15, the pressure of intrusion is much higher than expected and classical models underevaluate the size of the channels. Defects on the pore surface of SBA-15 affect the mercury intrusion in a similar way as the deviation from cylindrical geometry does for the pores of spongelike silica glasses. The results vindicate the models of Wenzel and Kloubek on the effect of surface defects on the mercury contact angle, which is significantly larger for a rough surface than for a plane surface. The surface defects of SBA-15 does not affect the evaluation of the mesopore size by nitrogen adsorption, as they are filled at an early stage of the adsorption and do not interfere with capillary condensation.

DESALINATION AND WATER TREATMENT, 2011

Membrane biofouling represents an important drawback in full-scale water reclamation plants as it... more Membrane biofouling represents an important drawback in full-scale water reclamation plants as it affects energy consumption, permeate productivity and even quality. Due to the high number of water-/membrane-/site-specifi c variables affecting membrane fouling and lifetime, cleaning and maintenance procedures need to be specifi cally designed for each application. Cleaning activities cannot directly be optimized onsite due to the necessity of ensuring a constant and safe product water fl ow and quality. For this reason, cleaning optimization needs to be transposed from plant to lab. In this work, a Spanish wastewater reclamation plant was selected to optimize cleaning procedures. For this, a reverse osmosis element was sampled and submitted to several cleaning protocols at lab-scale. The infl uence of the basic cleaning agent nature, pH and presence of additives on cleaning effi ciency was studied. The optimal membrane cleaning conditions were achieved with a NaOH solution at pH 12 containing 0.03% SDS. At these conditions, permeate fl ux after cleaning was two fold greater than fouled membrane permeate fl ux. In this work, lab-scale membrane cleaning tests have shown to be a successful tool to optimize cleaning activities for full-scale plants and understand the infl uence of cleaning variables on membranes restoring effi ciency.

Chemistry of Materials, 2005

The synthesis of large-pore micelle-templated silica (MTS) materials as discrete spheres by pseud... more The synthesis of large-pore micelle-templated silica (MTS) materials as discrete spheres by pseudomorphic synthesis solves the double challenge: enlarging the pore size of MTS beyond the diameter of the micelles and controlling the morphology and the size of the particles. The pseudomorphic transformation of silica beads of the desired size into MTS is one of the more suitable routes to control both nanometric and micrometric scales of MTS synthesis. The most employed method to enlarge pore diameter of MTS synthesized from alkyltrimethylammonium surfactants is to use 1,3,5-trimethylbenzene (TMB) as a swelling agent in the micelles. Unfortunately this method leads to particle aggregation. By means of the pseudomorphic route combining an original set of chemical compositions (C 18 TAB/decane/ TMB/NaI), under mild conditions (low temperature, without autoclaving), we successfully synthesized nonaggregated MTS beads of 10 µm with pore diameter ranging from 7 to 9 nm, 900 m 2 /g specific surface area, and 1.5 mL/g pore volume. To accommodate the large pore volume developed by largepore MTS, highly porous silica beads of 10 µm and 300 m 2 /g specific surface area have previously been synthesized by means of an emulsion/polymerization procedure. The control at nanometric scale, by means of surfactants, leads to improved textural properties compared to optimized silica gels, whereas the control of the micrometric morphology (discrete spheres) makes these supports suitable for column packing and chromatographic evaluation.

Dissipative water intrusion in hydrophobic MCM-41 type materials

Chemical Communications, 2002

Texture-related features of water intrusion in hydrophobised MCM-41 silicas render these material... more Texture-related features of water intrusion in hydrophobised MCM-41 silicas render these materials especially suitable for energy dissipation in mechanical dampers.

MCM-41 silica monoliths with independent control of meso-and macroporosity

New J. Chem., 2007

... a, Julien Iapichellaa, Benoît Lefèvrea, Christine Biolleya, Jean-Pierre Bellatb, François Faj... more ... a, Julien Iapichellaa, Benoît Lefèvrea, Christine Biolleya, Jean-Pierre Bellatb, François Fajulaa and Anne Galarneau*a. a Institut Charles Gerhardt Montpellier-UMR 5253 CNRS/ENSCM/ Matériaux Avancés pour la Catalyse et la Santé, Ecole Nationale Supérieure de Chimie de ...

Understanding of the physics of confined fluids is of major theoretical and practical interest. I... more Understanding of the physics of confined fluids is of major theoretical and practical interest. In the field of materials science, the most popular techniques used to characterise the texture of mesoporous supports are based on the analysis of the properties of a confined fluid:thermoporometry, adsorption technique and mercury intrusion porosimetry. In particular, in the last two techniques the pressure parameter is related to the dimension of the pores. The present study is dedicated to an original analysis of the forced-intrusion of a non-wetting liquid (water) in hydrophobic mesoporous materials presenting different pore topologies. Among these supports, MCM-41 type materials allowed to point out distinct mechanisms for the intrusion and the extrusion of water. Whereas the intrusion process obeys to the Laplace law of capillarity, the extrusion is found to be preferentially governed by the formation of the vapor phase by a mechanism such as nucleation. Therefore, the conventional interpretation given for the hysteresis observed in mercury porosimetry, based on wetting hysteresis and pore-blocking effects is not directly transposable to the case of water intrusion experiments. Data obtained on other supports such as silica gels and Controlled Pore Glass supports are also reported and discussed taking into account the results obtained in MCM-41 type materials. Finally, the mechanisms leading to hysteresis in both phenomena (sorption of a wetting fluid and forced intrusion of a non-wetting liquid) are shown to present strong analogies in model materials as well as in disordered and interconnected porosities.

We present experimental and theoretical results on intrusionextrusion cycles of water in hydropho... more We present experimental and theoretical results on intrusionextrusion cycles of water in hydrophobic mesoporous materials, characterized by independent cylindrical pores. The intrusion, which takes place above the bulk saturation pressure, can be well described using a macroscopic capillary model. Once the material is saturated with water, extrusion takes place upon reduction of the externally applied pressure ; Our results for the extrusion pressure can only be understood by assuming that the limiting extrusion mechanism is the nucleation of a vapour bubble inside the pores. A comparison of calculated and experimental nucleation pressures shows that a proper inclusion of line tension effects is necessary to account for the observed values of nucleation barriers. Negative line tensions of order 10 -11 J.m -1 are found for our system, in reasonable agreement with other experimental estimates of this quantity.

Thermodynamics of wetting: information brought by microcalorimetry

Journal of Petroleum Science and Engineering, 2004

The wetting state of a solid/fluids system depends on the relative value of the surface tensions ... more The wetting state of a solid/fluids system depends on the relative value of the surface tensions acting at the different interfaces. Whereas the free energy of a given solid/fluid interface is not directly measurable, the internal energy part can be relatively easily determined in the case of powders by microcalorimetry. In this paper, the various energy data that can thus