Emulsification Results Research Articles

Development and characterization of a continuous ultrasound emulsification and nano-emulsion polymerization process

Typically, nano-emulsions are prepared in batch high-speed homogenization or ultrasound processes and polymerized afterwards in batch reactors. However, fully continuous processes have the potential to decrease production costs and energy consumption compared to batch processes. This research thus focuses on implementing ultrasound into a fully continuous emulsification and nano-emulsion polymerization process to obtain latex nano-particles from butylmethacrylate and ethylene glycol dimethacrylate. The goal of this research is to produce nano-emulsions and nano-particles with the smallest obtainable size and polydispersity in a fully continuous two-stage process. In the first stage or emulsification stage, parameters like flowrate, residence time and acoustic power are varied to influence and determine the optimal energy density. In second stage or reaction stage, residence time and reaction temperature are studied to obtain particles of monodisperse sizes. Samples produced in both stages are analysed with Dynamic Light Scattering to measure the average size and polydispersity (PdI) of the emulsion droplets and particles. Emulsification results indicate that droplet size and PdI decreases at increasing energy densities (J/ml) until 60 J/ml after which a constant droplet size of 150 nm and PdI of 0.230 are reached. Furthermore, a particle size of 50 nm and PdI of 0.080 were achieved in both batch and continuous polymerization reactors after 5 min at 85 °C. By implementing the most optimal process parameters, small emulsion droplets and particles were obtained more energy efficient in a shorter emulsification and reaction time compared to literature ultrasound assisted nano-emulsion polymerization processes.

Arabinan side-chains strongly affect the emulsifying properties of acid-extracted sugar beet pectins

Pectins extracted from sugar beet pulp are promising additives for the food and beverage industry due to their good emulsifying properties. However, the relationship between molecular structure and emulsifying properties is still not fully understood; thus, systematic optimization of pectin extraction for a better emulsifying activity is not possible. In this study, we assess the underlying relationship between molecular structure and emulsifying properties by linking relevant structural parameters of 43 acid-extracted sugar beet pectins to their emulsifying properties.Sugar beet pectins with distinct structural characteristics were produced by acid extraction using varying conditions. The extracted polysaccharides were used as emulsifying agents in oil-in-water emulsions. Resulting droplet sizes were measured to correlate molecular characteristics with emulsifying properties. Analyses of protein content, degree of methylation, degree of acetylation, mean molecular weights, and trans-ferulic acid contents showed that these parameters affect the emulsifying properties to some degree, but cannot fully explain the differences observed among all pectins. However, a linear correlation between the proportion of neutral sugar side chains and droplet sizes was observed. The influence of galactose (18–30 mol%) was negligible, but increasing amounts of branched arabinans (up to 57 mol% arabinose) positively affected the emulsification result. Based on these results, it can be concluded that particularly branched arabinan side chains play an important role in the sugar beet pectin-based stabilization of emulsions. Thus, the arabinose content appears to be a suitable indicator to estimate the emulsifying properties of acid-extracted sugar beet pectins.

Premix membrane emulsification using flat microfiltration inorganic membranes with tailored structure and composition

Uniform oil-in-water emulsions were prepared using MCT (medium-chain fatty acid triglyceride, 10 wt%) as the oily dispersed phase and polysorbate 80 as the surfactant (1 wt%). The emulsification process was performed via premix membrane emulsification (PME) using 3 flat microfiltration ceramic membranes with different mean pore sizes (dm): borosilicate (symmetric, commercial, dm: 1.39 μm); SiOC (symmetric, manufactured, dm: 1.76 μm); and mullite (asymmetric, manufactured, dm: 1.18 μm). The droplets size and their distribution varied according to the membrane type and number of permeation cycles (up to a limit of 2 passes). All prepared emulsions presented a tendency to monomodal droplet distribution with span values in the range of 0.82–0.97. The coarse emulsion (premix) droplets were reduced from 6.30 to 4.50–2.17 μm. The asymmetric membrane (mullite) exhibited the highest permeation fluxes at constant relative pressure for both water (43.1 × 10−3 m3 m−2 s−1) and premix (Pass 1: 4.6 × 10−3 m3 m−2 s−1; Pass 2: 5.3 × 10−3 m3 m−2 s−1), still maintaining satisfactory emulsification results.

Modelagem e simulação de derrames de dois tipos de petróleo baseado na experiência de Tramandaí/RS

Tendo em vista a dependência global do petróleo e os riscos ambientais iminentes do manuseio e transporte de óleo no mar, o presente trabalho tem como objetivo reproduzir o incidente de vazamento de óleo na monoboia de Tramandaí – RS do dia 26 de Janeiro de 2012, e analisar a ação do intemperismo em dois tipos diferentes de óleo sujeitos às condições ambientais no dia do acidente. Este trabalho utilizou de dois diferentes softwares, o modelo de derrame de óleo ECOS acoplado ao modelo hidrodinâmico TELEMAC-3D. Devido ao histórico de vazamentos na região de Tramandaí, delimitou-se essa área como área de estudo a fim de estudar o comportamento do óleo. Com a pesquisa foi possível reproduzir as condições hidrodinâmicas do dia do incidente utilizando o TELEMAC-3D. Os processos de intemperismo implementados não influenciaram no tamanho da mancha de óleo. A influência do processo de emulsificação se mostrou importante na massa específica do óleo. O coeficiente implementado no modelo tende a estabilizar a emulsificação em 70 % para óleos crus e óleos pesados, mas que na realidade deveria variar de acordo com a massa específica de cada óleo. Assim, o resultado de emulsificação foi o mesmo para as duas simulações, não condizendo com o que poderia acontecer em condições reais. A evaporação se mostrou bem implementada no modelo, variando de acordo com cada massa específica do óleo. Os valores obtidos foram de 4 % de evaporação para a simulação A, 19,5 % para a simulação B.

Investigations on the influence of osmotic active substances on the structure of water in oil emulsions for the application as inner phase in double emulsions

Water in oil in water (WOW) double emulsions have a great potential as encapsulation systems in different industrial sections. Nevertheless, there are only few double emulsion based products available on market. An important limitation, regarding the product launch, is the insufficient stability of these products. Many instability mechanisms have to be taken into account: coalescence between inner water droplets, coalescence between outer oil droplets, coalescence between inner and outer water phase, and diffusion between the dispersed water droplets and the continuous outer water phase. In the present study, we focus on structural changes and stabilization mechanisms of inner water in oil (WO) emulsions. Osmotic active substances (OAS) have to be used in the inner water droplets to limit the diffusion processes between the water phases in double emulsions. We therefore investigated the influence of different OAS on the structural changes in WO emulsions. We focused on three subprocesses influencing the emulsification result: droplet breakup, stabilization directly after breakup and diffusional processes after droplet stabilization. For this, we prepared WO emulsions using sodium chloride, calcium chloride and glucose as OAS and polyglycerine-polyricinoleate as lipophilic emulsifier. The droplet size distribution was determined to evaluate structural changes. Furthermore, we measured interfacial properties and emulsion viscosities to evaluate stabilizing effects. Kinetic stabilization effects were evaluated by applying high pressure homogenization, known as a process with high requirements on the stabilization efficiency. The osmolality of the inner water phases was determined as parameter for the likelihood of diffusional processes. This characteristic value strongly depends on OAS type and concentration. Adsorption kinetics and diffusional processes turned out as the main factors influencing inner emulsion structure.

High-pressure emulsion formation in cylindrical coaxial orifices: Influence of cavitation induced pattern on oil drop size

This work investigates cavitation patterns after a cylindrical coaxial orifice at different orifice to outlet channel diameter ratios β<0.1. Further the influence of cavitation pattern on emulsion formation efficiency in high pressure homogenization is shown. At constant pressure loss (Δp) and varying β, three characteristic cavitation patterns (jet cavitation, choked cavitation and hydraulic flip) were detected via high speed imaging and acoustical measurement. The study shows that a surfactant concentration up to 10−4mol·L−1 and disperse phase content up to 10wt.% do not influence cavitation pattern transition in the investigated fluid. Emulsification results indicate decreasing emulsification efficiency with increasing β and thereby a strong correlation to the detected cavitation patterns.

Emulsification of particle loaded drops in simple shear flow

Abstract We investigated the influence of a particle load of disperse phase drops on their emulsification. Newtonian liquids were chosen for this investigation and a surfactant was present in all cases. A Couette-like shear cell was used enabling us to apply simple shear flow. The drop size distribution and drop morphology of the resulting oil-in-water emulsion were characterized. The influence of the wetting characteristics of the particles and the influence of the volume fraction of solids were investigated by comparing the breakup of silicone oil drops containing two types of particles, which showed different wetting behavior with that of pure silicone oils. One type of particles was situated in the liquid-liquid interface, the other type remained mainly wetted in the oil drops. With increasing volume fraction both suspension types showed shear rate dependent rheological behavior due to particle-particle interactions. Emulsification results were interpreted by means of apparent critical capillary numbers and correlated with the measured drop-to-matrix viscosity ratio. To calculate the viscosity ratio, the viscosities of the disperse phases were measured for each applied shear stress. Depending on the wetting characteristics, the particle load of the disperse phase showed different influence on the emulsification result. Particles situated in the liquid-liquid interface did not affect the apparent critical capillary number and therefore the drop breakup in the investigated volume fraction range. This result was explained by the reduction of particle loading during drop deformation and breakup due to the shearing-off of highly filled drops. Therefore the matrix fluid of the disperse phase governs the overall emulsification result. In contrast, particles located inside the disperse phase hindered the drop breakup. In comparison to Newtonian liquids with comparable bulk viscosities, the apparent critical capillary number was higher. It increased with increasing particle volume fraction. Additionally the apparent critical capillary number showed a dependence on the applied stress in case of the particle containing drops. This behavior is assumed to be due to an inhomogeneous viscosity inside the particle-loaded drop. We suggest using an effective drop viscosity to calculate the viscosity ratio in case of this type of system.

Assessing Bacillus subtilis biosurfactant effects on the biodegradation of petroleum products

Microbial pollutant removal capabilities can be determined and exploited to accomplish bioremediation of hydrocarbon-polluted environments. Thus, increasing knowledge on environmental behavior of different petroleum products can lead to better bioremediation strategies. Biodegradation can be enhanced by adding biosurfactants to hydrocarbon-degrading microorganism consortia. This work aimed to improve petroleum products biodegradation by using a biosurfactant produced by Bacillus subtilis. The produced biosurfactant was added to biodegradation assays containing crude oil, diesel, and kerosene. Biodegradation was monitored by a respirometric technique capable of evaluating CO₂ production in an aerobic simulated wastewater environment. The biosurfactant yielded optimal surface tension reduction (30.9 mN m(-1)) and emulsification results (46.90% with kerosene). Biodegradation successfully occurred and different profiles were observed for each substance. Precise mathematical modeling of biosurfactant effects on petroleum degradation profile was designed, hence allowing long-term kinetics prediction. Assays containing biosurfactant yielded a higher overall CO₂ output. Higher emulsification and an enhanced CO2 production dataset on assays containing biosurfactants was observed, especially in crude oil and kerosene.

Study on Microcrystalline Chitin Cinnamon Nanoemulsion

To improve the miscibility of cinnamon oil with water, this study uses microcrystalline chitin as the surfactant to prepare cinnamon oil nanoemulsion. Firstly, use isopropyl alcohol and concentrated phosphoric to act with chitin, disperse molecular crystal structure of chitin, and then use hydrochloric acid for decalcification, and prepare microcrystalline chitin through centrifugation, washing, freezing and drying. Dissolve it in acetic acid solution as emulsification, and dissolve cinnamon oil in anhydrous ethanol, and mix both of which to obtain emulsion by drops. Judge the emulsification process and results of microcrystalline chitin on cinnamon oil through conductivity data. The conductivity decreases gradually to 0 from 1.4μS·cm-1. At room temperature, the solution is aqueous liquid without stratification and precipitation, but has good stability.

Drop Detachment from a Micro‐Engineered Membrane Surface in a Dynamic Membrane Emulsification Process

AbstractDrop size distribution is an important characteristic of emulsions, probably the most crucial one for their use in various applications. Here, a pilot‐scale apparatus with a cone‐shaped flow geometry is introduced. The plate contains a micro‐engineered membrane manufactured from silicon allowing for the production of emulsions with narrow drop size distributions. The process is characterized by producing model emulsions of the oil‐in‐water type under laminar rheometric flow conditions and by accessing the regime of drop detachment as a function of the wall shear stress applied, by means of high‐speed imaging in a separate flow cell. Furthermore, clear evidence is given of the crucial influence of the membrane wetting properties on the emulsification results, by comparing the performance of micro‐engineered membranes composed either of silicon, silicon nitride, or nickel, for pore diameters from 1 to 12 μm, in the flow cell.

A high-pressure homogenization emulsification model—Improved emulsifier transport and hydrodynamic coupling

The high-pressure homogenizer emulsification modelling framework by Håkansson et al. (2009a, Chemical Engineering Science 64, 2915–2925; 2009b. Food Hydrocolloids 23, 1177–1183), is further developed in this study. The model, including the simultaneous fragmentation of drops, coalescence of drops and kinetic adsorption of macromolecular emulsifiers, is improved with regard to two points. First, the transport of adsorbed emulsifier between drops of different sizes due to the fragmentation and coalescence of drops, is included using bivariate population balances. Second, the coupling of hydrodynamics to the emulsification model is improved using information from recent hydrodynamic investigations. The proposed framework is exemplified using a set of physically reasonable kernels and a production scale high-pressure homogenizer geometry, showing realistic emulsification results.

Development of Piezoelectric Ultrasonic Thrombolysis Device for Blood Clot Emulsification

Ultrasonic thrombolysis is an effective method to treat blood clot thrombus in a blood vessel. This paper reports an OD 5 mm and an OD 10 mm piezoelectric thrombolysis transducers that vibrate longitudinally and generate a pressure field at the distal vibration tip. Studies of vibration mode, pressure field pattern, and cavitation effect were carried out. The transducers were also tested for blood clot emulsification. The results indicate both transducers are effective. The OD 10 mm transducer with a long transmission wire has shown to provide a strong cavitation effect and work effectively at low frequency, high amplitude, and high power conditions. The OD 5 mm transducer was found to operate effectively under higher frequency, low amplitude, and lower power conditions. The cavitation effect is moderate, which facilitates precision and controls over obtaining a more uniform emulsification result.

Effect of Microchannel Geometry on High‐Pressure Dispersion and Emulsification

AbstractExperimental investigations of the effect of microchannel geometry on high‐pressure dispersion and emulsification were carried out. Customized microchannels of varying geometric principles were fabricated in silicon and steel. In order to characterize the process efficiency of microchannel geometries, the effects of the process parameters (mean velocity, Reynolds number, and local pressure drop) were examined and correlated to the dispersion and emulsification results. It is demonstrated that high pressure losses focused at a small channel length and high velocity gradients lead to high stress intensities and, in consequence, to low particle or droplet sizes. Thus, 2D orifices were successfully further improved regarding their process efficiency by adding a third‐dimension constriction.

Effect of membrane parameters on the size and uniformity in preparing agarose beads by premix membrane emulsification

Agarose microbeads were prepared by premix membrane emulsification with Shirasu-Porous Glass (SPG) membrane and Polyethylene (PE) membrane. The effects of membrane parameters, including pore size, pore size distribution, contact angle between membrane surface and the water phase, shape of pore opening and membrane thickness on size and uniformity of agarose beads were investigated in this study. The results showed that pore size distribution and shape of pore opening did not affect the emulsification results apparently within a wide range in premix membrane emulsification, not as the result in general emulsification. The contact angle between the water phase and the membrane surface must be large enough to obtain uniform-sized agarose beads in both direct membrane emulsification and premix membrane emulsification. The results also showed that the membrane pore size and thickness affected the size distribution of emulsion. Thicker membrane resulted in more uniform and smaller emulsion when the number of pass through membrane is controlled. There was a linear relationship between the number average diameter of agarose beads and membranes pores size in premix membrane emulsification. Agarose beads with diameters from 3.06 to 9.02 μm were prepared by controlling membranes pore size. The ratio of the number average diameter of agarose beads to membrane pore diameters was found to be 0.486.

Multi-stage premix membrane emulsification for preparation of agarose microbeads with uniform size

Uniform-sized agarose beads with diameters less than 10 μm and agarose content as high as 14 wt% were prepared by premix membrane emulsification. Agarose aqueous solution was used as the water phase. A mixture of liquid paraffin and petroleum ether containing hexaglycerin penta ester (PO-500) was used as the oil phase. The water phase was mixed with the oil phase at 60 °C and a coarse W/O emulsion was produced in a homogenizer. Then, the coarse emulsion was extruded through a hydrophobic membrane under high pressure to form an emulsion, which was slowly cooled under gentle agitation to form gel beads. The effects of preparation conditions on emulsification results were investigated and it showed that the pressure, number of passes, petroleum ether/liquid paraffin (v/v) in the oil phase, the concentration of PO-500 and concentration of agarose in the water phase, all affected the size and uniformity; coarse emulsion did not affect the emulsification results. The coefficient variation (C.V.) of agarose beads under optimal preparation conditions was 9.8%. This method realized microbeads with both uniform sizes and high agarose contents that are difficult to be prepared by conventional emulsion methods.

Preparation of W/O emulsions by membrane emulsification with a mullite ceramic membrane

Monodispersed W/O emulsions were prepared by using submerged membrane emulsification apparatus with a mullite ceramic membrane. Kerosene was used as the continuous phase and water was used as the dispersed phase. The effects of stirring speed and transmembrane pressure on droplet size and dispersed flux were studied. The droplet size of the emulsions decreased with increased stirring speed but increased with increasing transmembrane pressure. The flux of the dispersed phase was proportional to transmembrane pressure, decreased with increasing stirring speed at a low transmembrane pressure and increased slightly at a high transmembrane pressure. The effect of pre-soaking time on the emulsification result was also investigated.

The impact of mass transfer and interfacial expansion rate on droplet size in membrane emulsification processes

In membrane emulsification, especially under conditions where droplets are forming with a narrow droplet size distribution, it is conjectured that the interfacial phenomena are determining the emulsification result. The process parameters of continuous phase flow and dispersed phase flux were analysed from the perspective of how they could be affecting the interfacial tension of the growing droplet. This work first reviews the applicability of current droplet formation models (force balance and spontaneous transformation based (STB)), describes the interfacial transport of surfactant molecules to an expanding oil–water interface, and models the flow of dispersed phase through a pore using MATLAB. The data from these calculations are then applied in a model to predict the final size of the droplets, which includes dynamic effects of mass transfer and expansion rate. The droplet detachment mechanism in membrane emulsification was modelled from the point of view of Gibbs free energy. An interactive finite element program called the surface evolver was used to test the model. A program was written and run in the surface evolver, which allows the user to track the droplet shape as it grows, to identify the point of instability due to free energy, and thus predict the maximum stable volume (MSV) attached to the pore. The final droplet size was found by applying a pressure pinch constraint (PPC), which is based on the division of the surface into two volumes, a droplet and a segment, which remains attached to the pore mouth. The relative size of these two volumes is such that the resulting radii of curvature of the droplet will maintain an equal Laplace pressure across the surface of both volumes. Predicted droplet sizes were compared to experimental data from the literature. It was found that changes in surfactant coverage caused by mass transfer coupled to the expansion rate of the oil–water interface have a significant and predictable effect on the final droplet size in membrane emulsification. The extent of the influence of the dispersed phase flux on dynamic interfacial tension was quantified using a dimensionless parameter, the mass transfer expansion ratio (MER). The MER can be used to predict the effect of increasing the depletion of surfactant on the relative final droplet size in membrane emulsification. This new insight into the role mass transfer and surface expansion play in membrane emulsification allows us to now predict à priori the final droplet size that would form for a particular set of conditions, and can lead to better process design methods in the future.

Stabilization of emulsions by OSA starches

In continuous mechanical emulsification, droplets of a coarse premix are first deformed and disrupted. Secondly, the newly formed interface has to be stabilized. Emulsions are thermodynamically unstable, as droplets tend to coalesce. To avoid coalescence of droplets, different effects have to be taken into account. The objective of this paper is to investigate the possibility of producing finely dispersed emulsions by using OSA starches as additive. Experiments were carried out using two commercially available OSA starches that differ mainly in viscosity of their aqueous solutions. In the experiments, the dispersed phase content, starch concentration as well as pH value and the influence of dissolved salts of different ion strength have been investigated. By droplet size analysis directly after production of oil-in-water emulsions the emulsifying properties of such starches were determined. Measurements of interfacial tension prove that OSA starches are surface active substances. It was shown by emulsification experiments that the stabilization of droplets by OSA starches is very efficient. The emulsification results achieved with OSA starches have been found to be independent from the type of starch and the starch concentration above the lower limit of starch needed for stabilization. The emulsification results are independent of pH value and ion valence. Therefore it can be concluded that steric hindrance is the main stabilizing mechanism of OSA starches. As proteins stabilize emulsion droplets mainly by electrostatic repulsive forces, the emulsification result depends strongly on pH, which leads to poor emulsification at pH values near the iso-electric point. The results of the work presented here suggest that whey proteins can be substituted by OSA starches with a specific advantage at low pH values near the iso-electric point of the protein.

Influence of hydrostatic pressure and gas content on continuous ultrasound emulsification

Ultrasound is one means among others of producing emulsions mechanically. Droplet disruption in sonicated liquid–liquid systems is considered to be controlled by cavitation. Both hydrostatic pressure and gas content of the liquids influence the probability and intensity of cavitation. Continuous ultrasound emulsification experiments were carried out to elucidate the effect of these parameters on the result of droplet disruption. Maximum energy density in the apparatus decreases with increasing hydrostatic pressure, probably due to partial suppression of cavitation which is the main mechanism of power dissipation. At constant energy density there is no significant influence of hydrostatic pressure on the emulsification result, however. Corresponding results were obtained for the influence of the gas content. Gas saturation or partial degassing prior to emulsification lead to a shift in maximum energy density. But, again, at constant energy density no clear effect on the droplet size of the emulsion is observed.

Adsorption kinetics of emulsifiers at oil—water interfaces and their effect on mechanical emulsification

The bursting membrane method of measuring the adsorption of emulsifier molecules at oil—water interfaces is presented. For the emulsifiers dodecyl alcohol-10-glycol ether, a whey protein concentrate and egg yolk the adsorption kinetics are measured. It is shown that this method is applicable to determine the adsorption kinetics. Oil—water emulsions have been prepared with the above-mentioned emulsifiers. The influence of the adsorption kinetics of these emulsifiers on the emulsification result is shown.