No description available.

No description available.

No description available.

No description available.

In many applications employing particles, the distribution of particle sizes has significant influence on the properties of the resultant material. Membrane emulsification (ME) is a method for manufacturing uniformly sized emulsion droplets where a dispersed phase is forced through a membrane into the continuous phase. It is the shear applied on the membrane surface that detaches the droplets thereby generating an emulsion. Formulation of the dispersed and the continuous phase influences the final droplet size of the emulsion. Therefore one of the aims of this research is to broaden the existing knowledge on particle production by membrane emulsification using nickel microengeneered disk membrane with cylindrical pores and the Dispersion Cell. The Dispersion Cell was successfully used to produce W/O/W emulsions (the oil phase was pumpkin seed oil). Also W/O emulsions (the water phase was acidified sodium silicate) were produced and additionally solidified in order to manufacture solid silica particles with high surface area and internal porosity. The particles were additionally functionalized using 3-aminopropyltrimethoxysilane and turned into ion exchange material capable to sorb copper. Since the silica particles do not swell such ion exchange material might be interesting for applications in nuclear industry. Having in mind an industrial application of membrane emulsification the Dispersion Cell cannot be used due to the problems with the scaling up. Therefore two novel systems: Oscillating and Pulsating were developed and reported for continuous production of the particles. Both systems were commissioned using sunflower oil for production of O/W emulsions. Additionally the Pulsating system was successfully used for production of complex coacervates. In the Oscillating system the nickel membrane was in the shape of a candle and the shear on the membrane surface was induced by vertical oscillations of the membrane. In the Pulsating system a tubular nickel membrane was used and the shear on the membrane surface was applied by oscillations of the continuous phase. The scaling up of both Oscillating and Pulsating system can be achieved by providing a larger membrane area (elongating the membrane) as well as connecting the membranes in parallel. It was successfully shown that a simple force balance can be used to model the size of emulsion droplets as a function of the shear stress. The average shear stress worked better when modelling the droplet sizes in the Dispersion Cell, but the correction for the droplet neck had to be taken into consideration when higher dispersed phase flow rates were used. In the Oscillating and Pulsating systems it was the maximal shear stress that gave the better prediction, but in both systems it was clear that additional forces were present which influenced the final droplet size. An alternative field of application for the Dispersion Cell, relevant to the tests of functionalized silica particles, was investigated. The Dispersion Cell was modified into a continuous flow stirred cell with a slotted nickel membrane on the bottom. The continuous flow stirred cell is shown to be an effective technique for both mass transfer kinetics as well as equilibrium data acquisition combining both into a single step, and simplifying ion exchange analysis. To commission the system the commercial ion exchange resin (Dowex 50W-X8) was used. Once determined, the design parameters can readily be used to model ion exchange contacting in a well mixed system, column operations or any process that requires ion exchange material. Using the continuous flow stirred cell it was shown that the silica particles produced using the Dispersion Cell and functionalized using 3-aminopropyltrimethoxysilane were capable to sorb copper. As a part of the collaboration within the DIAMOND (Decommissioning, Immobilisation And Management Of Nuclear wastes for Disposal) project a novel ion exchange material (copper hydroxide acetate suitable for iodide sorption) produced in the Department of Chemistry (Loughborough University) was successfully tested using the continuous flow stirred cell and equilibrium and mass transfer parameters were determined. The continuous flow stirred cell is particularly relevant to instances when the mass of ion exchange material available for the testing is low (less than 1g) and when dealing with hazardous or expensive materials. It is a technique employing microfiltration and ion exchange (or sorption), of the engineered particles that could be produced by membrane emulsification described in this thesis.

No description available.

Our knowledge of the behaviour of emulsions and the oil-water interface at the molecular level is relatively sparse when compared to the huge importance of these systems in everyday life. This thesis describes the development of several techniques that have the potential to extend this knowledge further. Ellipsometry is exquisitely sensitive to density variations across a fluid-fluid interface, but the interpretation of the ellipsometric response from the oil-water interface, both in the absence and presence of adsorbed species, is nontrivial. The responses from the interface between simple linear alkanes and water suggest that these interfaces are more complex than the air-water interface. The results are indicative of a "drying layer" and a model based on the hard sphere repulsion of a hydrocarbon surface is developed to explain these results. The conclusions from this study on the pristine oil-water interface are used as a basis for the interpretation of the ellipsometric response of a surfactant monolayer at the oil-water interface. The results suggest that the nonionic hydrocarbon surfactant C(_10)E(_8) forms a disordered monolayer with partially-hydrated headgroups. The structure of this film is largely independent of the nature of the superphase; whether air, hexadecane or triolein. The competitive adsorption of the milk proteins ß-casein and ß -lactoglobulin with C(_10)E(_8) at the hexadecane-water interface is also studied. At low and high concentrations of C(_10)E(_8), the measured ellipticity is indicative of an unperturbed protein and surfactant film, respectively. At intermediate concentrations, the measured ellipticity suggests a mixed surfactant/protein film. Raman spectroscopies deliver considerably more data than ellipsometry, but the difficulties of delivering and collecting light from a buried interface require more sophisticated experimental engineering. An attempt is made to sandwich a 100-nm- thick oil film between water and silica in order to probe the oil-water interface by evanescent wave Raman scattering employing a visible excitation source. Unfortunately this procedure has proved unsuccessful to date. The requirement for a thin oil film can be bypassed if the signal from the adsorbed species is enhanced. The design and construction of an ultra-violet resonance Raman microspectrometer is described to achieve this aim. This instrument also has the potential to probe proteins and peptides adsorbed in lipid bilayers. The commissioning and development of a combined in-situ confocal Raman- tribometer is also presented. This instrument is capable of determining the composition of emulsions under shear within a soft elastohydrodynamic contact, as well as the morphology of the soft, deformed surface and the thickness of the lubricating film.

No description available.

This thesis is concerned with the evaporation rates of emulsions stabilised by either surfactant molecules or nm-size solid particles. Understanding of the mechanisms of the evaporation process plus the control of the rate limiting step of each mechanism involved in such processes is important for a number of practical applications which include cosmetics, paints and agrochemicals. The work of this thesis deals with three main aspects. Firstly the evaporation rates of pure liquids have been determined. Secondly, evaporation rates of surfactant-stabilised creamed, gelled and high internal phase emulsions have been investigated. Lastly, evaporation rates of emulsions stabilised by solid particles will be discussed. The study concerned with the pure liquids was mainly to verify the set-up of the evaporation rig, to compare our results with those obtained by K. J. Beverley (Thesis in preparation, University of Hull) and determine the diffusion coefficients of different liquids in the vapour phase. For creamed emulsions stabilised by surfactants it was found that the evaporation rate of the continuous phase is as that of bulk phase and the evaporation rate of the dispersed phase is slowed down up to 20 times. The retardation in the evaporation rate of the dispersed droplets depends mainly on the solubility of the dispersed phase in the continuous phase. In the case of gelled emulsions, the mass loss of the emulsions gelled by different gelling agents (colloidal particles and water-soluble polymers) show that the evaporation rates depend on the gelling agent. For high internal phase emulsions, evaporation rates of water from emulsions containing involatile oils have been studied. Depending on the geometrical properties of the initial conditions, the mass loss rate is controlled by either diffusion of the liquid in the vapour (large emulsion/sample tube volume ratio) or diffusion of the liquid in the nm-thin films which separate the close-packed oil drops (small emulsion/sample tube volume ratio). The nature of the colloidal forces acting between the dispersed droplets also plays an important role during the evaporation. For emulsions stabilised solely by nm-size silica particles (Pickering emulsions), the evaporation rate is slower compared with that stabilised by surfactants under the same conditions. Moreover, we have found that the solid residues left behind after the total evaporation of the volatile species (oil and water) from Pickering emulsions show macroporous structures. The type of the microstructure is related to that of the parent emulsion and the vapour pressure of the oil. These results may lead to the production of novel macroporous inorganic materials.

Ultrasonic spectrometry has potential for monitoring chemical processes on line; an important application is the detection of the suspended particle size distribution (PSD) in emulsions. Measured ultrasonic wave attenuation as a function of frequency is compared to the predictions of an adaptive wave propagation model to obtain an estimate of the PSD. Current models are based either on scattering physics, heat transfer, or hydrodynamics, or on a combination of these. Most models give good prediction of attenuation for dilute and semi-dilute systems, but they are known to break down at high dispersed phase concentrations and for very small (10s of nm) particles. The limits of applicability are not known in a formal sense. The principal aim and contribution to knowledge of this research is to formally determine the limits of existing theory and to set out which model or models are appropriate for use with emulsions with large or very small particles (nano-emulsion), and at small and large concentrations of dispersed phase. The second aim is to answer the same question for the case of encapsulated emulsions in which the droplets are encapsulated in a thin polymer shell. The project combines computational methods based on analytic theories of wave propagation with a comprehensive experimental programme.