Effect of process parameters on nanoemulsion droplet size and distribution in SPG membrane emulsification (original) (raw)
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Desalination, 2002
Shirasu-porous-glass (SPG) membranes with a mean pore size from 0.4-6.6 pm were used to produce O/W emulsions consisting of vegetable (rape seed) oil as the dispersed phase and Span 80 dissolved in demineralized water as the continuous phase. The emulsion droplets with a mean droplet size 3.5 times larger than the mean pore size and the span of the droplet size distribution between 0.26 and 0.45 were produced using 2% emulsifier at a transmembrane pressure slightly exceeding the capillary pressure. Under these conditions the dispersed phase flux through the membrane was in the range of 0.7-7 l.m-'.h-' and only about 2% of the pores were active. However, if the transmembrane pressure was considerably higher than the capillary pressure, the dispersed phase flux strongly increased and droplets with a broad droplet size distribution were produced. The hydraulic resistance of the SPG membrane was inversely proportional to the square of the mean pore size, which is in agreement with the Hagen-Poiseuille law. The membrane porosity is independent on the pore size and ranged from 53-60%.
Chemical Engineering Research and Design, 2018
Oil-in-water and water-in-oil nanoemulsions are interesting carriers for respectively oil soluble and water soluble actives. In this study, oil-in-water (O/W) and water-in-oil (W/O) nanoemulsions were prepared by premix membrane emulsification. A coarse emulsion (premix) was injected thanks to a high pressure pump through a Shirasu Porous Glass (SPG) membrane with pore size of 0.5 µm in order to reduce and homogenize the droplet size. The effect of viscosities on the pressure and droplet size was investigated: the water phase viscosity by increasing glycerol concentration, the oil phase viscosity with mineral oils of different viscosities and the overall emulsion viscosity by increasing the dispersed phase content of the emulsion. The pressure required to break up the droplets inside the membrane pores ∆P dis did not depend on viscosities, while the pressures generated by the flows through the pipe ∆P pipe and the membrane ∆P f low were proportional to the viscosity of the overall emulsion. W/O nanoemulsions were more difficult to produce and to characterize but thanks to the original setup working at pressures up to 65 bar and high flowrates, W/O mineral oil nanoemulsions were produced with mean droplets size around 600 nm and flow rate of 50 mL/min.
JOURNAL OF CHEMICAL ENGINEERING OF JAPAN
A novel method of emulsion preparation by intramembrane premix membrane emulsi cation without preliminary emulsi cation was developed for the preparation of monodispersed oil-in-water (O/W) and water-in-oil-in-water (W/O/W) emulsions with small droplet size and high disperse phase content at high productivity. The dispersed phase and the continuous phases were simultaneously permeated through Shirasu Porous Glass (SPG) membranes with mean pore sizes of 5, 10, and 20 µm at a membrane permeation rate over 50 m 3 /m 2 h. Monodispersed emulsions with disperse phase content of 25 to 95% by volume, mean droplet size to the mean pore size ratio of 1.2 to 0.26, and with droplet size distribution (span) of 0.4 to 0.6 were prepared. The emulsion droplet size decreased with membrane permeation rate, continuous phase viscosity and the number of membrane permeation cycles. A composite W/O/W emulsion with an average droplet size of 10.4 µm, a span of 0.5 and of disperse phase content of 50% by volume was also prepared in a sequence of consecutive steps without integrating the preliminary emulsi cation step by high-shear homogenization.
Parameter Selection of Emulsification Processes: Conditions for Nano- and Macroemulsions
Chemical Engineering & Technology, 2012
Beside factors like nature of the emulsifier as well as rheology of the interface and continuous phase, the droplet size distribution of an emulsion governs emulsion properties such as long-term stability over months or years, texture, and optical appearance. Consequently, emulsions with droplets in nano-scale are of interest when well-defined emulsion properties are needed. The formation of emulsions consisting of water, corn oil, and nonionic surfactants using disc systems and high-pressure homogenizers was studied. The emulsion droplet size distributions were obtained by means of a laser diffraction method. The influence of parameters affecting the emulsion formation, such as emulsification time, viscosity for the disc system, pressure, and homogenizing steps for high-pressure homogenization, was investigated. Data to determine the effect of the surfactant type and concentration were collected for both systems. The emulsification process using a disc system was evaluated in order to highlight its advantages and limits in comparison to high-pressure homogenization.
Journal of Membrane Science, 2014
Membrane emulsification is a promising technology for the production of micro-nano particles, which is able to compete with the conventional mechanical emulsification processes. The production of emulsions with narrow droplet size distribution at dispersed phase fluxes (productivity) sufficiently high to make the process suitable for industrial application is still a considerable challenge. The interfacial tension between the dispersed phase and the membrane pore wall is a crucial parameter to maintain droplets shape while enhancing productivity. In the present paper, a membrane thickness with asymmetric properties in terms of wettability between external and internal sides has been tested in the preparation of W/O emulsions. The membrane surface wettability modification was obtained by adsorption of hydrophobic macromolecules on the lumen side of hydrophilic membrane. Lipase was used as a model macromolecule. W/O emulsion droplets with smaller droplets size have been produced with lipaseloaded membrane compared with the unmodified hydrophilic membrane. High dispersed phase flux of 30 L h À 1 m À 2 was also obtained with a significant increase of process productivity compared to the use of hydrophobic membranes. These results show that membrane-protein interaction can be used to functionalize opportunely the membrane for membrane emulsification application reducing emulsification time and increasing dispersed phase flux without modifying the control on droplets properties in terms of size and size distribution.
Food emulsions using membrane emulsification: conditions for producing small droplets
Journal of Food Engineering, 1999
Ceramic membranes were used to produce oil-in-water (O/W) emulsions consisting of vegetable oil as the dispersed phase and skim milk as the dispersion medium. The purpose of the work was to ®nd operating conditions suitable for producing small emulsion droplets, a small size being important for emulsion stability. The main parameters investigated were the eect of wall shear stress, emulsi®er concentration and membrane pore size. Formation of small droplets was favoured at higher emulsi®er concentrations and for a high wall shear stress using a membrane with a small nominal pore size. Submicron particles were produced at an 8% emulsi®er concentration for a wall shear stress of 135 Pa using a 0.1 lm pore size membrane. Under these conditions the¯ux was >100 kg m À2 h À1 . A high¯ux is important for industrial-scale production of food emulsions using membrane emulsi®cation. Ó
Production of uniform O/W emulsions through a porous medium of micron-sized glass beads
Premix membrane emulsification, along with other latest emulsification techniques, has established itself as a promising technique for the production of small sized and relatively monodisperse emulsions at comparatively low energy inputs. A drawback of premix emulsification is membrane fouling that may become serious depending on the formulation components, and related to that their interaction with the membrane and their ease of removal. In this research, an alternative system consisting of a packed bed of glass beads, which is intrinsically easier to clean, was investigated. The process parameters, especially, particle size and bed height, were studied. A coarse O/W emulsion, of 5% hexadecane in water having 0.5% (v/v) Tween-20 as surfactant, was prepared with an Ultraturrax homogenizer operated at 3500 rpm for 10 minutes. The droplet size was typically around 25-30 µm with a span of 0.9-1.0 (span is defined as δ = (d 90 −d 10)/d 50). Premix emulsification was carried out by passi...
Langmuir, 2008
Here, we investigate experimentally and theoretically the factors that determine the size of the emulsion droplets produced by membrane emulsification in "batch regime" (without applied crossflow). Hydrophilic glass membranes of pore diameters between 1 and 10 µm have been used to obtain oil-in-water emulsions. The working surfactant concentrations are high enough to prevent drop coalescence. Under such conditions, the size of the formed drops does not depend on the surfactant type and concentration, on the interfacial tension, or on the increase of viscosity of the inner (oil) phase. The drops are monodisperse when the working transmembrane pressure is slightly above the critical pressure for drop breakup. At higher pressures, the size distribution becomes bimodal: a superposition of a "normal" peak of monodisperse drops and an "anomalous" peak of polydisperse drops is observed. The theoretical model assumes that, at the moment of breakup, the hydrodynamic ejection force acting on the drop is equal to the critical capillary force that corresponds to the stability-instability transition in the drop shape. The derived equations are applied to predict the mean size of the obtained drops in regimes of constant flow rate and constant transmembrane pressure. Agreement between theory and experiment is established for the latter regime, which corresponds to our experimental conditions. The transition from unimodal to bimodal drop size distribution upon increase of the transmembrane pressure can be interpreted in terms of the transition from "dripping" to "jetting" mechanisms of drop detachment.
Enhancing the Throughput of Membrane Emulsification Techniques To Manufacture Functional Particles
Industrial & Engineering Chemistry Research, 2009
Formulation technologies increasingly demand the manufacture of droplets with user-controlled size and size distributions for applications in emulsions, capsules, and semisolid particulates. These are used in various functional consumer products. This paper introduces methods to enhance throughput for two types of membrane emulsification system, using cross-flow and rotating membrane technology. Modification of the interaction between the dispersed phase and the surface of the membrane, the inner wall of the pores (through control of hydrophobicity), pore orientation, and pore shape is demonstrated to increase emulsion droplet productivity. Such methods can also be deployed in the production of capsule materials using emulsion precursors. The possible mechanisms underlying the enhancements are discussed. It is concluded that noncircular pores can offer significant process benefits for the production of uniform droplets and semisolid particulates. It is demonstrated that the droplet formation rate can be doubled through optimization of the orientation of noncircular pores in a rotating membrane process.
Journal of Membrane Science, 2008
During membrane emulsification it is shown that the size of the drops formed at the membrane surface may increase with increasing dispersed phase injection rate through the membrane, or it may decrease, depending on the prevailing conditions. This is illustrated using a stirrer positioned above a flat disc membrane with a regular array of pores of 20 μm diameter and a spacing between the pores of 80 μm and another membrane of 200 μm pore spacing. In the former case an additional mechanism for drop detachment is the push-off force, which is determined by the geometry of the drops as they deform at the membrane surface. In the force balance, the push-off force may be added to the shear-drag force to cause drop detachment. In the case of the 200 μm pore spaced membrane this force is much less prominent. The capillary-shear model has been modified to include this push-off force. The study required the use of very low dispersed phase injection rates and very high rates.