Impact Of Surfactant Concentration Research Articles

Comprehensive Evaluation of Tilted Fiber Bragg Grating (TFBG) Sensors for Characterizing Oil–Water Emulsions: A Study on the Impact of Surfactant Concentration and Mixing Speed

Comprehensive Evaluation of Tilted Fiber Bragg Grating (TFBG) Sensors for Characterizing Oil–Water Emulsions: A Study on the Impact of Surfactant Concentration and Mixing Speed

Complexation between Dendritic Polyelectrolytes and Amphiphilic Surfactants: The Impact of Surfactant Concentration and Hydrophobicity

The solution structure of complexes composed of the cationic dendrimer, anionic surfactants, and their counterions is studied by molecular dynamics simulations using the bead–spring coarse-grained model. We identify that depending on the surfactant concentration and hydrophobicity the system exists in three structural regimes. In the first regime surfactant molecules are noncooperatively absorbed by the dendrimer. Here, the pervaded volume of the dendrimer and the bulk solution contain loosely distributed unimeric surfactants and counterions. In the second regime hydrophobic attractions between surfactant tails give rise to cooperative binding. The absorbed surfactants self-assembly into multichain micellar-like aggregates, whereas the bulk solution consists of separate unimers. In the third regime the surfactants form multichain aggregates both within the interior of the dendrimer and in the bulk. Our data indicate that self-assembly of the absorbed surfactants affects the dendrimer conformations as compared to its neutral counterpart. In the case of noncooperative binding the dendritic polyelectrolyte swells due to the osmotic pressure exerted by the absorbed unimers and counterions. In the regimes characterized by cooperative binding and pronounced self-aggregation of the encapsulated surfactants swelling of the dendrimer is suppressed. This is attributed to a reduction of the osmotic pressure inside the macromolecule due to the ion exchange phenomenon appearing as a result of strong Coulomb attractions between charged monomers of the dendrimer and the encapsulated micellar aggregates. We also find that aggregate formation affects the overall charge accumulated in the dendrimer. In particular, for the dendrimer loaded with massive aggregates, we report the charge inversion effect which transforms the cationic dendrimer into an anionic dendrimer–surfactant complex. Our results provide molecular insights into self-assembly of supramolecular complexes and controlled absorption of guest surfactant molecules in dendrimer-based host–guest systems.

Intrinsic lipolysis rate for systematic design of lipid-based formulations

Lipid-based formulations (LBFs) are used by the pharmaceutical industry in oral delivery systems for both poorly water-soluble drugs and biologics. Digestibility is key for the performance of LBFs and in vitro lipolysis is commonly used to compare the digestibility of LBFs. Results from in vitro lipolysis experiments depend highly on the experimental conditions and formulation characteristics, such as droplet size (which defines the surface area available for digestion) and interfacial structure. This study introduced the intrinsic lipolysis rate (ILR) as a surface area-independent approach to compare lipid digestibility. Pure acylglycerol nanoemulsions, stabilized with polysorbate 80 at low concentration, were formulated and digested according to a standardized pH–stat lipolysis protocol. A methodology originally developed to calculate the intrinsic dissolution rate of poorly water-soluble drugs was adapted for the rapid calculation of ILR from lipolysis data. The impact of surfactant concentration on the apparent lipolysis rate and lipid structure on ILR was systematically investigated. The surfactant polysorbate 80 inhibited lipolysis of tricaprylin nanoemulsions in a concentration-dependent manner. Coarse-grained molecular dynamics simulations supported these experimental observations. In the absence of bile and phospholipids, tricaprylin was shielded from lipase at 0.25% polysorbate 80. In contrast, the inclusion of bile salt and phospholipid increased the surfactant-free area and improved the colloidal presentation of the lipids to the enzyme, especially at 0.125% polysorbate 80. At a constant and low surfactant content, acylglycerol digestibility increased with decreasing acyl chain length, decreased esterification, and increasing unsaturation. The calculated ILR of pure acylglycerols was successfully used to accurately predict the IRL of binary lipid mixtures. The ILR measurements hold great promise as an efficient method supporting pharmaceutical formulation scientists in the design of LBFs with specific digestion profiles.Graphical abstract

Shale core wettability alteration, foam and emulsion stabilization by surfactant: Impact of surfactant concentration, rock surface roughness and nanoparticles

Hexadecyltrimethyl ammonium bromide (HCTAB) and sodium dodecyl sulfate (SDS) are popular conventional surfactants with versatile industrial and oilfield applications. Knowledge of the optimum conditions for their applications for shale rock wettability modification, as well as foam and emulsion stabilization is relevant for hydrocarbon recovery process optimization. Influence of surfactant concentration, rock surface roughness and presence of nanoparticles in surfactant solutions on contact angles, oil-water interfacial tension (IFT), as well as foam and emulsion stabilization by HCTAB and SDS was investigated in this study. The interfacial properties measurements were conducted with Drop Shape Analyser (DSA 25), whereas the foam generation and stability properties were investigated via dynamic foam analyzer (DFA100). The emulsion stabilization and demulsification processes were investigated in Formulaction Turbiscan. Results showed an existence of optimum concentration of surfactant for obtaining the lowest contact angles, oil-water IFT reduction, as well as attaining maximum foam stability. The contact angle measured on rough core surfaces were smaller than the contact angle measured on smooth surfaces. Contact angles increased with increasing salnity concentration, but decreased with the increasing rock saturation time. Oil was more detrimental to foam stability when the generated foam was brought into contact with the resident oil, compared to when oil was added to the foaming solutions before foam generation. Lower contact angles, durable foam, and stable emulsion were produced in presence of oil and at high temperature via the synergy of nanoparticles and surfactants. Almost 66% decreased in contact angle was achieved with carbon nanotubes-SDS solutions, whereas Al 2 O 3 nanoparticles-HCTAB foam attained a viscosity of 99 mPa-s at 60 °C. The foam demonstrated shear thinning Newtonian fluids behaviors but attained a plateau after sometimes. The study suggests the conditions for optimization of conventional surfactants applications in conventional and unconventional reservoir. • Synergy of nanoparticles and surfactants on shale core wettability was studied. • Foams are less stable when they suddenly contacts the resident oil. • There is optimum surfactant concentration for maximizing interfacial activities. • Contact angle decreased by 66% in presence of carbon nanotubes-SDS solutions. • Al 2 O 3 -HCTAB foam attained a viscosity of 99 mPa-s at 60 °C.

Impact of surfactant concentration and antioxidant mode of incorporation on the oxidative stability of oil-in-water nanoemulsions

The effect of the presence of surfactant micelles and of the mode of incorporation (pre-homogenization or post-homogenization) on the antioxidant efficiency of a homologous series of n-alkyl gallates phenolipids (G0, G3, G8, G12 or G16) was investigated in oil-in-water nanoemulsions. In both absence and presence of surfactant micelles, G12 and G16 were the best antioxidants. The effect of the mode of incorporation was modulated by the presence of surfactant micelles. In absence of surfactant micelles, G8 and G16 had higher efficiency when incorporated pre-homogenization, suggesting that the mode of incorporation promoted a distinct initial distribution of these compounds. In contrast, in presence of surfactant micelles, the antioxidants could be incorporated in any phases without efficiency loss. These results demonstrate the important role of surfactant micelles in modulating the antioxidant efficiency and could be used by the food industry to optimize emulsion formulations.

Impact of Spacer Nature and Counter Ions on Rheological Behavior of Novel Polymer-Cationic Gemini Surfactant Systems at High Temperature.

Compatible surfactant-polymer (SP) hybrid systems at high temperature are in great demand due to the necessity of chemical flooding in high-temperature oil reservoirs. The rheological properties of novel SP systems were studied. The SP system used in this study consists of a commercial polymer and four in-house synthesized polyoxyethylene cationic gemini surfactants with various spacers (mono phenyl and biphenyl ring) and different counterions (bromide and chloride). The impact of surfactant concentration, spacer nature, counterions, and temperature on the rheological features of SP solutions was examined using oscillation and shear measurements. The results were compared with a pure commercial polymer. All surfactants exhibited good thermal stability in seawater with no precipitation. Shear viscosity and storage modulus were measured as a function of shear rate and angular frequency, respectively. The experimental results revealed that the novel SP solution with a mono phenyl and chloride counterions produces a better performance in comparison with the SP solution, which contains mono phenyl and bromide counterions. Moreover, the effect is enhanced when the mono phenyl ring is replaced with a biphenyl ring. Shear viscosity and storage modulus decrease by increasing surfactant concentration at the same temperature, due to the charge screening effect. Storage modulus and complex viscosity reduce by increasing the temperature at a constant angular frequency of 10 rad/s. Among all studied SP systems, a surfactant containing a biphenyl ring in the spacer with chloride as a counterion has the least effect on the shear viscosity of the polymer. This study improves the understanding of tuning the surfactant composition in making SP solutions with better rheological properties.

Antimicrobial activity of PIT-fabricated cinnamon oil nanoemulsions: Effect of surfactant concentration on morphology of foodborne pathogens

The impact of surfactant concentration (10 to 20 wt%) on the antimicrobial activity of cinnamon oil nanoemulsions formed by the phase inversion temperature (PIT) method was studied against a number of foodborne pathogens: Escherichia coli, Salmonella Typhimurium, Staphylococcus aureus and Vibrio parahaemolyticus. Minimum inhibitory concentration (MIC), dynamic time kill, and changes in bacteria morphology were determined. Increasing non-ionic surfactant (Tween®80) concentration from 10 to 20 wt% increased the MIC values of the nanoemulsions. However, dynamic time kill plots revealed that nanoemulsions with higher surfactant concentrations (15 and 20 wt%) led to faster or more prolonged inhibition of bacteria compared to those with lower concentration (10 wt%) or with bulk cinnamon oil. Morphological changes of the bacteria were more promoted for nanoemulsions containing higher surfactant concentrations as shown by field emission scanning electron microscopy (FE-SEM). The antimicrobial activity of the cinnamon oil nanoemulsions was attributed to their ability to disrupt bacterial cell wall structures and promote expulsion of internal cellular material.

Effect of Tween 80 on Bubble Size and Mass Transfer in a Bubble Contactor

AbstractGas absorption in aqueous solutions with Tween 80 and absorption processes based on hydrodynamics and mass transfer is determined. The impact of surfactant concentration on gas holdup and gas‐liquid interfacial area is analyzed, observing an increase of these parameters with surfactant concentration. The influence of liquid‐phase contamination on the absorption process is investigated on the basis of the liquid‐film mass transfer coefficient, removing the effect caused by the presence of a surfactant and the gas flow rate on the interfacial area and, thereby, on the volumetric mass transfer coefficient. The opposite effect on the mass transfer coefficient can be observed which decreases in the presence of the surfactant.