Droplet Size Distribution Analysis Research Articles

Biosynthesis of pectic oligosaccharide-based amphiphiles as novel stabilizers of nanoemulsions by coupling enzymatic depolymerization with alkyl/alkenyl succinylation

Pectic oligosaccharides (POS) are gaining increasing recognition as a novel kind of prebiotics. Here, a new multipurpose amphiphilic POS was synthesized by coupling pectinase-mediated depolymerization of citrus pectin with lipase-catalyzed alkyl succinylation. Structural characterization by thin-layer chromatography, size exclusion chromatography, mass spectrometry, Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance, and transmission electron microscopy showed that POS obtained by enzymatic hydrolysis consisted mainly of octamers and hexamers and was subsequently hydrophobically functionalized by reaction with alkylsuccinic anhydrides of various alkyl chain lengths to develop amphiphilic properties. Emulsions stabilized by pectin and alkylsuccinylated POS were assessed by analysis of droplet size distribution, zeta potential, and confocal fluorescence microscopy. The results showed that POS-derived amphiphiles POS-SA12 and POS-SA22 (alkyl C12 and C22) formed stable nanoemulsions with mean particle size of <200 nm and a narrow polydispersity index of <0.20, compared to pectin-based microemulsions (>1100 nm in size and >0.8 polydispersity index). Differences were largely ascribed to the well-balanced hydrophobicity of the introduced alkyl group and the hydrophilicity of the carboxyl groups in the molecular structure of POS-SA12. Our study introduces a green synthetic approach for the production of a novel POS-derived amphiphile with prebiotic and emulsifying properties showing excellent performance in stabilizing oil/water emulsions and other extensive applications.

Analysis of droplet size distribution and selection of spray parameters based on the fractal theory

Using multiple parameters to represent the droplet size distribution (DSD) always leads to various outcomes that make it hard to decide. The research combined theoretical derivation with experiments to study the random fractal of the DSD. The function of the DSD was deduced, and the fractal dimension (FD) was used as an independent parameter to characterize the DSD. The DSD was measured by the Malvern measuring apparatus under different spray pressure. The results showed that the FD of the five nozzles measured experimentally is between 1.5 and 3. The independent parameter FD has more advantages than multi-parameters (the Sauter mean diameter and the size distribution span). In the air cleaning technology by spray, the FD was used as an evaluation parameter. The optimal distance from the nozzle to the wetting fine wire plate was determined to be 75–85 cm, and the total dust efficiency of the wetting fine wire plate air cleaning device can reach 98.98%.

A study of alkali-silica nanoparticle-polymer (ANP) flooding for enhancing heavy oil recovery

The method of nanofluid flooding to enhance heavy oil recovery has attracted much attention in oilfields. An EOR technology named alkali-silica nanoparticle-polymer (ANP) flooding was designed to enhance heavy oil recovery. The performance of the ANP flood system on reducing interfacial tension (IFT), altering the wettability of rock surface, emulsifying and displacing heavy oil were compared with that of polymer (P), alkali-polymer (AP) and nanoparticle-polymer (NP) flood systems. Visual flooding test was conducted to investigate the displacement mechanisms of different flood systems in porous media. ANP nanofluid could remain stable over 30 days without sedimentation of nanoparticles. The emulsifying ability of the four flood systems for heavy oil followed the order: P < NP < AP < ANP. Based on the analysis of droplet size distribution of emulsion and changes of IFT value with alkali concentration, the best formula of ANP system to emulsify heavy oil was 0.3% [w/v] Na2CO3 + 0.1% [w/v] silica nanoparticle + 1000 mg L−1 polymer. Electrostatic repulsion between silica nanoparticles and oil droplets played a dominated role on stabling ANP emulsion. ANP flood system could change the wettability of rock surface to a more water-wet state (contact angle varied from 85.4° to 35.6°). Core and visual flooding tests proved that ANP flood system had a better sweep and displacement efficiency for heavy oil than other three flood systems (P, AP and NP), which could enhance heavy oil recovery by 21.19% after water flooding in a sandstone core. Emulsification is the main mechanism for ANP flooding to enhance heavy oil recovery.

Quantitative Analysis of Droplet Size Distribution in Plant Protection Spray Based on Machine Learning Method

Spray droplet size is the main factor affecting the deposition uniformity on a target crop. Studying the influence of multiple factors on the droplet size distribution as well as the evaluation method is of great significance for improving the utilization of pesticides. In this paper, volume median diameter (VMD) and relative span (RS) were selected to evaluate the droplet size distribution under different hollow cone nozzles, flow rates and spatial positions, and the quantitative models of VMD and RS were established based on machine learning methods. The results showed that support vector regression (SVR) had excellent results for VMD (Rc = 0.9974, Rp = 0.9929), while multi-layer perceptron (MLP) had the best effect for RS (Rc = 0.9504, Rp = 0.9537). The correlation coefficient of the prediction set is higher than 0.95, showing the excellent ability of machine learning on predicting the droplet size distribution. In addition, the visualization images of the droplet size distribution were obtained based on the optimal models, which provided intuitive guidance for realizing the uniform distribution of pesticide deposition. In conclusion, this study provides a novel and feasible method for quantitative evaluation of droplet size distribution and offers a theoretical basis for further determining appropriate operation parameters according to the optimal droplet size.

Baobab polysaccharides as emulsifiers

Polysaccharides extracted from fruits and leaves of baobab tree (Adansonia digitata) were assessed for their emulsifying capacity. Emulsions were formed at acidic pH (pH 2.0 and ϕ = 0.1) and were investigated by means of droplet size distribution analysis, ζ-potential measurements, and interfacial composition analysis. Despite the macromolecular differences of baobab polysaccharides all emulsions were formulated at concentrations resulting in comparable zero shear viscosity of the continuous phase allowing structure vs. function relationships to be made. Emulsions made with fruit polysaccharides formed finer droplets and exhibited good long term stability than those formulated with leaf polysaccharides. Stability was achieved by formation of thick interfacial layers, as evidenced by the large polysaccharide interfacial loading (Γpolysaccharide 13.8 or 20.7 mg m−2) that created an effective steric barrier against droplet growth, whereas proteins did not seem to play central role. Fruit polysaccharide emulsification performance at acidic pH was attributed to their compact conformation at the interface that is linked to their structure. Conversely, the presence of rhamnogalacturonan segments in leaf polysaccharides resulted in chain desorption and poor emulsion stability. Overall, it has been shown that baobab fruit polysaccharides could be suitable emulsifiers for a range of technological applications that require low pH stability.

Removal of gas condensate from industrial wastewater using low‐cost adsorbents: Optimization by Box–Behnken design method

AbstractIn this study, three effective adsorbents such as Padina sanctae cruces algae (PSC), activated carbon (AC), and bentonite clay were used to remove gas condensates from industrial wastewater generated in the fourth refinery of South Pars Gas Complex in Iran. Physical and surface properties of the adsorbents were characterized using Brunauer–Emmett–Teller (BET), field‐emission scanning electron microscope, Fourier transform‐infrared spectroscopy, and energy dispersive X‐ray spectroscopy (EDAX) analyses. Also, droplet size distribution analysis was used to determine the size distribution of gas condensate droplets in the emulsion and to evaluate the emulsion stability. According to the BET analysis, the specific surface area of AC, PSC, and bentonite were obtained as 900.93, 0.0463, and 40.70 m2/g, respectively. To check the effect of different parameters on the removal efficiency of gas condensates, the Box–Behnken design method was used. Moreover, the optimal conditions for the removal of gas condensates included pH 9, temperature of 65°C, contact time of 120 min, and an adsorbent dosage of 5 g/L. Under such optimal conditions, the adsorption efficiencies using AC, PSC, and bentonite were obtained as 98.90%, 96.35%, and 97.24%, respectively. Furthermore, the maximum adsorption capacities of 1250, 54.95, and 99.01 mg/g were achieved using AC, PSC, and bentonite, respectively, in which AC showed the highest adsorption capacity ever achieved for the removal of gas condensate from wastewater. Besides, the thermodynamic study indicated that the sorption process was exothermic and spontaneous.

Depletion-Induced Flocculation of Concentrated Emulsions Probed by Photon Density Wave Spectroscopy.

Stable, creaming-free oil in water emulsions with high volume fractions of oil (ϕ = 0.05-0.40, density matched to water) and polysorbate 80 as an emulsifier were characterized without dilution by Photon Density Wave spectroscopy measuring light absorption and scattering behavior, the latter serving as the basis for droplet size distribution analysis. The emulsion with ϕ = 0.10 was used to investigate flocculation processes induced by xanthan as a semi-flexible linear nonabsorbing polymer. Different time regimes in the development of the reduced scattering coefficient μs' could be identified. First, a rapid, temperature-dependent change in μs' during the depletion process was observed. Second, the further decrease of μs' follows a power law in analogy to a spinodal demixing behavior, as described by the Cahn-Hilliard theory.

The effect of silanization assisted nanoparticle hydrophobicity on emulsion stability through droplet size distribution analysis

There has been great recent interest in the potential use of Nanoparticles as modifiers or alternatives to surfactants for stabilizing emulsions, among which silica NPs have been commonly used as the most cost effective option. Since silica NPs are hydrophilic with a tendency toward the aqueous phase, their surface should be activated either by the aid of a surfactant or by chemical treatment. The aim of the present work is to assess the effect of two chemically activated silica NPs on stability of dodecane-water emulsions through optical microscopy. Therefore, hydrophilic silica NPs are firstly synthesized with sodium silicate solution and are subsequently silanized with hexamethyldisilazane (HMDS) into different extents to synthesize two different NPs with different wettability states, namely as HSNP1 and HSNP2. The degree of Nanoparticle wettability is quantified by the variation of the silanol group density of bare silica NPs, which has reduced by 49% for HSNP1, resulting in partially hydrophobic silica NPs and by 60% for HSNP2, resulting in hydrophobic silica NPs. The emulsion stability prepared by HSNP1 and HSNP2 has been assessed via both bottle tests and droplet size distribution analysis, which is tracked by fitting proper distribution functions on the experimental data. The log-normal and the bimodal (a mixture of two log-normal distribution) distribution functions are respectively fitted on the droplet size distribution of emulsions stabilized by HSNP1 and HSNP2. This revealed minor changes in the droplet size distribution of emulsions stabilized by partially hydrophobic silica NPs (HSNP1) over a month, while a significant alteration in droplet size distribution of emulsions stabilized by hydrophobic silica NPs (HSNP2) has been observed after a week. Higher emulsion stability stabilized by HSNP1 is also confirmed by higher zeta potential value and higher surface coverage of partially hydrophobic silica NPs (HSNP1) compared to that of hydrophobic silica NPs (HSNP2). The partially hydrophobic silica NPs, wetted to the same extent by both liquid phases has been found to be suitable for stabilizing emulsions for Enhanced Oil Recovery (EOR) applications.

The effect of brine salinity on water-in-oil emulsion stability through droplet size distribution analysis: A case study

ABSTRACTWater-in-oil emulsion usually forms during waterflooding in some heavy oil reservoirs. The composition and salinity of the injected water critically affect the w/o emulsion droplet size distribution, which control the emulsion stability and emulsion flow in porous media. The aim of the present work is to assess the effect of different sea water salinities on w/o emulsion stability through microscopic imaging. Therefore, w/o emulsions were prepared with different sea water samples, which were synthesized to resemble Persian Gulf, Mediterranean, Red Sea, and North Sea water samples. The results showed that log-normal distribution function predicts very well the experimental data to track the emulsion droplet size distribution, and then it was used for the emulsion stability analysis. It was found that among the four emulsion samples, North Sea emulsion with the lowest NaCl and TDS concentration of 24.12 g/L and 34.44 g/L remained stable up to almost 24 hours, while Red sea emulsion with the highest NaCl and TDS concentration of 32.39 g/L and 41 g/L became unstable after 6-hour period. This indicated that as the brine concentration increases, the w/o emulsion droplets would be larger due to the higher rate of aggregation and coalescence, and the emulsion stability decreases.

Emulsification of heavy crude oil in brine and its plugging performance in porous media

In this paper, heavy crude oil and formation brine collected from Xinjiang oilfield were used to prepare crude oil-in-water (O/W) emulsions. Emulsification tests were first conducted to screen suitable emulsifiers. Then stability test, droplet size distribution analysis, and rheological property measurements were carried out to investigate the physicochemical characteristics of the developed O/W emulsions. It was found that surfactants of Span 60 and Tween 80 combined with sodium hydroxide could reduce the oil/water interfacial tension and thereby emulsify the heavy crude oil in formation brine. A series of sandpack flow tests were conducted to evaluate the plugging performance of the heavy O/W emulsions, emulsified using 0.1 wt% Span 60–0.1 wt% Tween 80–0.025 wt% NaOH. The flow test results showed that heavy O/W emulsion can result in more than 99% permeability reductions in sandpacks. The permeability reduction by emulsion plugging increased greatly with an increase in oil quality and injected emulsion slug, but decreased with an increase in sandpack permeability and injection flow rate.

Droplet size and morphology analyses of dry liquid

Dry water is a free-flowing powder consisting of numerous solid particle-stabilized water droplets with typical sizes and volumes of 10−6–10−4m and 10−3–103pL, respectively. We describe the first characterization of dry water stabilized with hydrophobic silica nanoparticles, by using laser diffraction droplet size distribution analysis. The water droplet dimensions were measured to be a few tens of micrometers in air, by using the laser diffraction method. These dimensions correspond well with measurements by both laser diffraction and optical microscopy methods for a Pickering-type water-in-n-dodecane emulsion prepared by dispersing dry water in n-dodecane. Optical microscopy confirmed that the dry water consisted of flocs of non-spherical water droplets, and the flocs ranged in size from a few tens of micrometers to a few millimeters in air. On the basis of these results, the flocs of water droplets were proposed to dissociate into individual water droplets under the air blast during droplet size measurement by the laser diffraction method. It was also confirmed that pressurizing the dry water between two glass slides led to encapsulated water leaking from the silica nanoparticle shells. This on-demand pressure-sensitive water leak phenomenon shows a possible usage of the dry waters as a material delivery carrier.

Engineering of acidic O/W emulsions with pectin

Pectins with distinct molecular design were isolated by aqueous extraction at pH 2.0 or 6.0 and were examined in terms of their formation and stabilisation capacity of model n-alkane–in–water emulsions at acidic pH (pH 2.0). The properties and stability of the resulting emulsions were examined by means of droplet size distribution analysis, Lifshitz-Slyozov-Wagner modelling, bulk rheology, interfacial composition analysis, large-amplitude oscillatory surface dilatational rheology, electrokinetic analysis and fluorescence microscopy. Both pectin preparations were able to emulsify alkanes in water but exhibited distinct ageing characteristics. Emulsions prepared using pectin isolated at pH 6.0 were remarkably stable with respect to droplet growth after thirty days of ageing, while those prepared with pectin isolated at pH 2.0 destabilised rapidly. Examination of chemical composition of interfacial layers indicated multi-layered adsorption of pectins at the oil-water interface. The higher long-term stability of emulsions prepared with pectin isolated at high pH is attributed to mechanically stronger interfaces, the highly branched nature and the low hydrodynamic volume of the chains that result in effective steric stabilisation whereas acetyl and methyl contents do not contribute to the long-term stability. The present work shows that it is possible by tailoring the fine structure of pectin to engineer emulsions that operate in acidic environments.

CFD study of distillation sieve tray flow regimes using the droplet size distribution technique

A good understanding on the characteristics of sieve tray flow regimes is one of the keys to achieve an efficient distillation operation. A 3-D computational fluid dynamics (CFD) model based on the volume-of-fluid (VOF) and the large eddy simulation (LES) has been developed to simulate the complex flow phenomena in a sieve tray. The analysis of droplet size distribution (DSD), which was made possible by the use of VOF model, was then carried out to characterize the prevailing flow regime. The obtained results are in good agreement with the experimental data available in the literature in terms of the prediction of clear liquid height. The results obtained from the DSD analysis reveal that the sphere equivalent droplet diameter, ddrop,eq, is inversely proportional to the gas superficial velocity, and is directly proportional to the liquid volumetric flow rate, QLo. Approaching the froth-to-spray transition regime, ddrop,eq was found to range from 0.008m to 0.0114m. These findings may serve as valuable information in assisting tray designers and process engineers to decide on ranges of operating conditions which allows the attainment of high efficiency distillation operation, and also providing some insights into future development of sieve tray technology.

Rheology and microstructure of gluten and soya-based o/w emulsions

Highly concentrated oil-in-water (o/w) emulsion stabilised by means of gluten and soya protein isolate (SPI) at low pH have been characterized by means of linear dynamic viscoelasticity and droplet size distribution analysis (DSD). The microstructure of these emulsions has been characterized at a colloidal level by using confocal laser scanning microscopy (CLSM) and light microscopy (LM). These emulsions always exhibited a behaviour characteristic of highly flocculated emulsions with a mechanical spectrum showing a well-developed plateau region. DSD results generally showed log normal bimodal profiles. Microstructure images revealed occurrence of a close packing of droplets with a broad distribution of sizes participating in the formation of a three dimensional flocculated network. The Mason model of elasticity of compressed emulsions has been used to correlate viscoelastic and microstructural parameters giving adequate fitting but underestimating the elastic properties obtained for the highest concentration of gluten. These deviations may be explained in terms of an enhancement of the elastic network formed in the aqueous phase in which the glutenin fraction must play an important role.

Percutaneous absorption of 4 organic solvents in the guinea pig (II). Effect of surfactants.

Percutaneous absorption of 4 organic solvents (1,1,1-trichloroethane, 1,1,2-trichloroethane, toluene and butanol) from various colloidal preparations in a surfactant-water-organic solvent system was studied in vivo in guinea pigs. The preparations examined were binary solutions of organic solvents and surfactants, o/w emulsions and microemulsions. Phase diagram, birefringence microscopy and droplet size distribution analysis were used for characterization of the preparations. It was found that skin absorption of the solvents depends on the type of surfactant, type of preparation and also on phase equilibria in the systems studied. The presence of nonionic surfactants in the solvents and in a microemulsion with butanol caused skin absorption to decrease. A reduced uptake of solvents from o/w emulsions was observed. The absorption of butanol from a microemulsion with anionic surfactant was greater than from the pure solvent.

MULTIPLE EMULSIONS STABILIZED BY COLLOIDAL MICROGRYSTALLINE CELLULOSE

ABSTRACT Multiple emulsions stabilized by colloidal microcrystalline cellulose (CMCC, Avicel RC591) at the w/o and o/w interfaces, and by the addition of Span 80 or Span 85 at the w/o interface, were studied by means of brightfield microscopy, freeze-etch electron microscopy, droplet size distribution analysis and rheologic measurements. Stable multiple emulsions were prepared by incorporation of sodium chloride in the innermost aqueous phase, thereby creating an osmotic gradient preventing loss of the inner aqueous phase to the external aqueous phase. Freeze-etch electron microscopy of the multiple emulsions indicated the presence of a network of microcrystalline cellulose at the outer o/w interface. It may be assumed that the surfactant directly stabilized the w/o interface by adsorption at the interface, as well as indirectly by facilitating wetting of the microcrystalline cellulose by the oil. From rheologic measurements, the existence of a three-dimensional network in the external aqueous phase was indicated by the considerable degrees of thlxotropy and significant static yield values of these multiple emulsions.

An Electrostatic Fog Precipitator

Abstract An electrostatic precipitator has been developed which deposits liquid droplets from fog on water-sensitive film for later analysis of droplet size distribution and chloride content. Current design criteria and operating characteristics are presented. The instrument has been used locally in the collection of natural fogs and ocean spray. Partial results of these investigations are presented together with laboratory evaluation of instrument alteration of droplet size.