Céline Picard

Ozone–water contacting by ceramic membranes

Abstract A common process in water treatment is the wet oxidation for the removal of certain organic and inorganic pollutants. The strongest oxidant technically applied in this process is ozone, which is an unstable gas under normal conditions, and therefore is produced from oxygen on site, usually by electrical discharge. After that the ozone has to be transferred from that gas into the water to be treated. Conventionally ozone transfer is achieved by bringing the gas and water in direct contact by means of bubble columns, injectors or other similar devices. Under unfavorable conditions, however, these methods suffer from excessive formation of foam requiring an extra treatment and a high-energy demand for pumping gas or water. This projects approach was to improve the transfer by better control of gaseous and aqueous phases conditions at the contact surface. This was achieved by means of a membrane both separating the two phases and allowing for an ozone transfer between them. Due to ozones high oxidation potential, chemically inert ceramic membranes were chosen for that purpose. In experiments, it was found that the transfer of the unstable ozone molecules is not obstructed by ceramic membrane material. Transfer rates between gaseous ozone and model water were measured for conventional ceramic membranes, as well as specially designed ones. They are comparable to conventional methods or better on the base of mass transfer per reactor volume. In conventional oxide membranes, water enters the pores because of capillary effects in the hydrophilic material [Burggraaf, A.J. and Cot, L., 1996, Fundamentals of inorganic Membrane Science and Technology Elsevier Science, The Netherlands]. The water in the pores raises the diffusion resistance for the ozone thus decreasing the transfer itself. Consequently, the modification of the hydrophilic material features into a hydrophobic behavior was one promising approach for the optimization of the process. It was achieved through the application of a hydrophobic coating to the membrane surface, which greatly improved the transfer efficiency.

Impact of emollients on the spreading properties of cosmetic products: a combined sensory and instrumental characterization.

This study deals with the impact of emollients on the spreading properties of cosmetic products using a combined sensory-instrumental approach. To that purpose, three esters and one silicone were selected and incorporated separately into an oil phase. Different cosmetic o/w emulsions were then prepared with these different oil phases. Both of them were analyzed by instrumental techniques and in vivo sensory analyses. A significant effect of the emollient used was established in emulsions and in oil phases as well. Concerning emulsions, results reveal a clear correlation between in vivo spreading evaluation and friction coefficient parameters measured by texture analyzer, despite a fairly low correlation coefficient (Pearson coefficient=-0.78). Concerning oil phases, characterization of spreading was done by monitoring the contact angle relaxation of a drop of solution after deposition on a flat PMMA surface whereas sensory procedure was based on spontaneous spreading of oil phases onto the skin. Finally, good correlations between in vivo sensory analysis and instrumental measurements of both oils and emulsions were found, thus promising the possible development of predictive tools to evaluate spreadability.

Flux enhancement in microfiltration by corkscrew vortices formed in helical flow passages

Abstract The performance of helical inserts in existing tubular filters has been investigated by Bellhouse et al. [12] . The insert and filter combination was found to deliver high filtration fluxes at low cross-flow rates over a wide range of applications, covering reverse osmosis to microfiltration. In addition the flow shear stresses were viscous, and fluids containing delicate organisms, such as marine algae, were concentrated without damage. The increased fluxes were attributed to the generation of corkscrew vortices, formed by the interaction of Dean vortices and an axial flow component. If this explanation is correct, it should be possible to generate similar corkscrew vortices in internal helical passages, which surround a central lumen. By coating the internal surface of the helical passages with a suitable membrane, a one-piece filter, capable of emulating the performance of the insert and tubular filter, could be constructed. Ruiz et al. [16] had demonstrated their ability to produce ceramic filters with internal helical grooves, and the Laboratoire des Materiaux et Procedes Membranaires at Montpellier University produced a number of prototype filters to a design derived from the geometries used in [12] . These filters were tested using high concentrations of bakers’ yeast. Similar fluxes to those obtained with the inserts and tubular filters were achieved, over the same range of flow rates. Whilst the mechanism of concentration polarisation reduction by corkscrew vortices works over the whole range of filtration applications, the unique combination of viscous flow, high fluxes, low cross-flow rates and high feed concentrations is particularly suited to microfiltration in bio-processing applications.

Ceramic membranes for ozonation in wastewater treatment

Ozone, due to its high oxidative capacity, is often used in water treatment for the degradation of organic pollutants. Unfortunately, the application of ozone in the form of gas bubbles causes foam problems. To avoid the development and accumulation of foam, the transfer of ozone into the water through gas permeable membranes was investigated. Ceramic membranes were used because of the chemical inertness of the material. The hydrophilic behaviour of ceramic membranes made of metal oxides causes the water to penetrate into the pores. This creates a diffusion resistance for the ozone which decreases the transfer rates. To keep the water out of the porous structure and maintain the gas/water interface at the membrane surface, the surface properties of the membrane were changed. The membrane was soaked in a solution of a fluorinated compound. Water drop measurements and transfer rates were investigated and confirmed the stability of the hydrophobic nature of the membrane surface. The ozone transfer rates thus achieved were in the range of 12 grams of ozone per square meter per hour.

Cosmetics and Personal Care Products

Cosmetic and personal care products are complex mixtures intended to be applied to the external parts of the human body. In the long list of ingredients are included polymers which are either natural or synthetic. This chapter presents the main natural polymers used in cosmetics which are mainly polysaccharides and proteins obtained from vegetable, animal and biotechnology origins. The use of artificial polymers is discussed through the example of cellulose derivatives which are widely used for their physicochemical properties and cosmetic benefits. Natural polymers in cosmetics play many distinct roles; they can be chosen either to improve the stability of colloidal systems, to control the rheological properties from manufacturing to end-user or to achieve the sensory expectation and efficiency of the product during application. Natural polymers are thus multifunctional ingredients used in many different commodities sometimes alone, but more often in combination with synthetic polymers as illustrated through different examples including hair care, skin care or toothpaste products. Natural polymers own a growing place in the cosmetic field and this can be attributed to the ever increasing desire for “naturality”. Their applicability in this field is further enhanced by their processibility and the multiple options possible to control properties through their chemical modifications.

Stretching properties of xanthan and hydroxypropyl guar in aqueous solutions and in cosmetic emulsions

Filament stretchability of xanthan gum (XG) and hydroxypropyl guar (HPG) was investigated in aqueous solutions (0.125, 0.25, 0.5, 1, 1.2 and 1.5% w/w) and in O/W emulsions using a texture analyzer. Additionally, rheological characterizations were carried out on the systems and shear and oscillation parameters were used to interpret stretching properties. XG solutions exhibited a solid-like behavior with rheological parameters much higher than for HPG one whatever the concentration. Filament stretching values of XG solutions were superior to HPG for concentration below 1% w/w and then became comparable for higher concentrations. No meaningful relationship was found between rheological and stretching values. Synergy was observed for all XG/HPG mixtures at 0.125, 0.25 and 0.5% influencing both the rheological and the filament stretching values. The 25/75 XG/HPG ratio showed the maximum synergistic effect at all concentrations while the filament stretchability was enhanced in a wider range of ratios. XG and HPG did not present the same behavior in emulsions. No clear synergistic effect was observed and XG markedly influenced the emulsion filament stretching.

Impact of coated TiO2-nanoparticles used in sunscreens on two representative strains of the human microbiota: Effect of the particle surface nature and aging

The impact of two differently coated TiO2-nanoparticles (NPs) was evaluated on two representative bacteria from the cutaneous microbiota (Staphylococcus aureus and Pseudomonas fluorescens) in conditions of use. Particles were coated in order to exhibit either hydrophilic or hydrophobic behavior. A first exposure scenario within some fresh/aged model emulsions was developed in order to measure both the impact of the NPs presence and their surface nature during the emulsions conservation. Thanks to this protocol, it was demonstrated that, during aging, the hydrophobic NPs modified the physicochemical characteristics of the emulsions, such as the pH or the colloids sizes, and favored the development of potential pathogenic bacteria. A second scenario was then envisaged, aiming to mimic the exposition of the skin, especially of the cutaneous bacteria, to NPs. Tested NPs were extracted from emulsions with different aging, and results highlighted the importance of both the NP coating nature and their history in emulsion. The different NPs impacts on the bacteria growth were discussed and linked to their surface properties modifications during aging, as polarity and charges. Finally, through two exposition scenarios, this work highlights the major impact of the NPs surface properties on bacteria.

Interactions between UV filters and active substances in emulsion: Effect on microstructure, physicochemical and in-vivo properties

&NA; The objective of the present study was to develop, characterize and evaluate the clinical efficacy of topical formulations containing or not active substances and UV‐filters, separate and in combination. To this end a stable formulation was developed to which four aqueous active substances and four lipophilic UV‐filters were added. The formulations were then submitted to microscopic characterization by light microscopy, to particle size measurement, and to macroscopic characterization by rheology and texture analysis. Finally, a clinical efficacy study was conducted to determine the effect of the formulations on the skin after application for 1 h. The formulation containing UV‐filters showed a high polydisperse microstructure and a large amount of liquid crystals. The formulations containing active substances showed higher resistance to deformation, compression and penetration tests. Regarding spreadability, formulations containing UV filters alone or in combination with active substances showed higher resistance to spreading. This behavior was associated with greater clinical efficacy in terms of stratum corneum water content, protection of the skin barrier function and skin surface brightness. It was demonstrated that the efficacy of the formulation is mainly associated with its structure and the way it interacts with the skin surface. Finally, this study showed that the mixture of these ingredients for the development of multifunctional sunscreens improves the performance of the formulations.

Influence of the emollient on emulsions containing lamellar liquid crystals: from molecular organization towards applicative properties

The sensory perception of cosmetic emulsions is complex as it is governed by an important number of parameters like the choice of raw materials, their interactions, the structural organisation of the system, etc. The aim of the present work was to go further in the interpretation of the emollient‐surfactant interactions, towards the emulsions applicative properties. For this purpose, two systems containing liquid crystals of the lamellar type were formulated, differing only in the selected emollient.