SDS Aqueous Solution Research Articles

Copper-catalysed bromine atom transfer cyclisation in SDS micelles.

The atom transfer radical cyclisation (ATRC) of non-activated alkyl bromides was realized under blue light irradiation in carbonate-buffered aqueous SDS solution using a catalytic system of CuBr2, Me6-TREN and ascorbic acid. The beneficial effect of SDS micelles can be accounted for by the activation of the C-Br bond as well as by the suppression of competitive reductive cyclisation.

Synergistic effects between anionic surfactant SDS and hydrophilic silica nanoparticles in improving foam performance for foam flooding

In foam flooding, foams stabilized by conventional anionic surfactants are usually raptured in contacting with crude oil, which behaves as a strong defoamer. In this article the synergistic effects between anionic surfactant SDS and negatively charged hydrophilic silica nanoparticles in stabilization of aqueous foams were examined. The results show that in either deionized (DI) water at 25 °C or Daqing simulated connate (SC) water with a total salinity of 6,778 mg/L at 45 °C, in absence of oil adding low concentration of silica nanoparticles into the SDS aqueous solutions can improve the foam performance of SDS mainly by increasing foam stability, as indicated by a synergistic effect index Se(d/s) (ratio of the composite foaming index of dispersion to that of solution) of 2.7 to 2.8. In presence of oil the foam performance of SDS in SC water at 45 °C can still be improved as indicated by an increased Se(d/s) of 3.7, but the maximum composite forming index is catastrophically reduced from 3222 Ls in absence of oil to 470 Ls in presence of oil. As similarly charged nanoparticles the silica nanoparticles do not adsorb at gas/liquid or oil/water interface to stabilize Pickering foams or Pickering emulsions but can improve emulsification of the oil, and the emulsified oil droplets together with the silica nanoparticles distribute in aqueous lamellae enhancing liquid viscosity and slowing down the liquid drainage in the foams. However, this effect weakens at high surfactant concentration, and addition of silica nanoparticles does not significantly reduce the interfacial tensions involved. The Enter (E), Spreading (S) and Bridging (B) coefficients of the oil in the foam systems are therefore still positive. The defoaming action of the oil in this system is not eliminated by only partially inhibited by addition of silica nanoparticles.

Experimental study and prediction on the thermal management performance of SDS aqueous solution based microchannel flow boiling system

This study reports the flow boiling of SDS aqueous solution in straight and tree-shaped microchannel for thermal management. Under different volume flow rate and heat flux, the effect of SDS on the flow pattern, heat transfer and pressure drop in different channel structures is clarified. The results reflect that unique flow patterns like bubble stacking, bubble cluster and activated bubbles are observed in the flow boiling of SDS aqueous solution. 400 mg/kg and 200 mg/kg SDS aqueous solution has the best overall heat transfer enhancement performance in straight (25% improvement) and tree-shaped (22% improvement) microchannels respectively. The heat transfer enhancing mechanism of SDS can be summarized as suppressing the formation of large volume vapor slug and promote the rewetting of the bottom channel surface. Based on this mechanism, SDS can also advance the ONB and extend the stable nucleate boiling state, 100 mg/kg, and 400 mg/kg SDS aqueous solution show longest stable nucleate boiling state in straight and tree-shaped microchannel respectively. Increasing solute concentration of SDS leads to larger pressure drop and stronger pressure drop fluctuation in both microchannels, but increasing volume flow rate will suppress this extra resistance and instability caused by SDS. Targeted heat transfer and pressure drop correlations are also presented.

Separation of CH4 - CO2 gas mixture by gas hydrate crystallisation: A parametric study

In the present study a comprehensive experimental study of the CO2 gas hydrate recovery from the CH4 (81.70 mol.%) - CO2 (18.30 mol.%) experimental gas mixture was realised. The effect of the mode, temperature, pressure, and promoter on the CO2 gas hydrate recovery efficiency was investigated. The parametric study will optimise the technology of gas hydrate crystallisation to CO2 remove from natural gas. The gas mixture process separation factor and gas hydrate recovery were studied in SDS (0.30 wt%) aqueous solutions with and without THF (3.80 wt%). The separation simulation was performed for the two modes: pressure-dropping and constant pressure in the temperature range 272.15–283.15 К at the driving forces 1.00 and 2.00 MPa 8 h after the start of the gas hydrate formation. The different temperature dependence is shown for the CH4 and CO2 gas hydrate recovery in depending on the aqueous solution. The CO2 gas hydrate recovery maximum, equal to 63.92% (without THF) and 57.19% (with THF), is observed at the constant pressure separation at 272.15 K and 2.00 MPa. However, THF addition makes it possible to decrease the gas hydrate dissociation pressure of the experimental gas mixture in 7.87 times at 272.15 K. Thus, the choice of the aqueous solution was determined by the aim for the gas hydrate separation – high gas hydrate recovery (without THF) or low process pressure (with THF).

Experimental study on subcooled flow boiling heat transfer of water-SDS mixtures in a vertical macrochannel

Flow boiling heat transfer performance of surfactant solutions is studied at a basis of deionized water. The tested fluids are aqueous solutions of SDS at concentrations ranging from 100 to 12500 ppm. Tests are performed at vertical, upward, 3 × 40 mm cross-section channel at 75 °C subcooling, atmospheric pressure, flow rates 200–300 kg/m2s (Re: 1400–2600) and heat fluxes 200–1000 kW/m2. The present experimental data show that the trend of heat transfer enhancement follows the opposite direction of surface tension trend when surfactant concentration increases. At CMC (Critical Micellar Concentration) heat transfer coefficient and bubble density take their maximum value, while bubble diameter takes its minimum value. Concentrations above CMC show minimal or no further effect on flow boiling heat transfer characteristics. The tendency of the heat transfer coefficient experimental data with respect to changes in surfactant concertation allows the development of a modified version of the well-known two phase model heat transfer of Shah, by incorporating a surfactant concentration dependent correction factor that predicts this work’s values at a ±10% margin and a mean absolute percentage error of 3.6%.

ENHANCED ORAL BIOAVAILABILITY OF NANONIZED PROGESTERONE IN HEALTHY AND PREGNANT RABBITS (NPROBIO STUDY)

The aim of this study is to evaluate and compare the oral bioavailability of nanonized progesterone (nano-PG) and micronized progesterone (micro-PG) sustained release tablet formulation in healthy and pregnant rabbits. High pressure compressed gas technology reduces the particle size from 1.72 ± 2.5 µm (micro-PG) to 800 ± 35 nm (nano-PG). DSC and XRD showed that both micro-PG and nano-PG were crystalline and exist as form I. Higher melting enthalpy of nano-PG indicated improved drug stability whereas XRD showed slight reduction in degree of crystallinity following nanonization. Nano-PG demonstrated 2-fold higher solubility in SDS aqueous solution and signicantly higher permeability (p < 0.05) across porcine intestine compared to micro-PG. The pharmacokinetics of nano-PG and micro-PG was conducted in healthy and pregnant rabbits. The Cmax of nano-PG was higher in healthy and pregnant rabbits however the difference was signicant in healthy rabbits only. The nano-PG demonstrated 30% and 18% higher bioavailability compared to micro-PG in healthy and pregnant rabbits, respectively. In conclusion, nanonization improves solubility, dissolution and bioavailability of PG in rabbits without affecting solid state characters

Methane and Carbon Dioxide Hydrate Formation in the Presence of Metal-Based Fluid

Hydrate-based technology has yet to find its way to commercial applications due to several issues, including formation conditions and slow kinetics. Several solid particles were introduced to speed up hydrate formation. However, these solid compounds have given contradictory results. This study investigated the effect of high thermal conductive metallic nanofluids of silver (Ag) and copper (Cu) on CH4 and CO2 hydrates. The solid particles were suspended in a 0.03 wt% SDS aqueous solution, and the results were compared with the 0.03 wt% SDS and deionized water samples. A stirred tank batch reactor was used to conduct the thermodynamic and kinetic experiments. The thermodynamic study revealed that 0.1 wt% of solid particles do not shift the equilibrium curve significantly. The kinetic evaluation, including induction time, the initial rate of gas consumption, half-completion time, t50 and semi-completion time, t95, gas uptake, and storage capacity, have been studied. The results show that the Ag and Cu promote CH4 hydrates while they inhibit or do not significantly influence the CO2 hydrates formation. A predictive correlation was introduced to get the apparent rate constant of hydrate formation in the presence of metal-based fluid at the concentrations range of 0.005-0.1 wt%.

Nanonized progesterone formulation for improved oral bioavailability in healthy and pregnant rabbits

The aim of this study is to evaluate and compare the oral bioavailability of nanonized progesterone (nano-PG) and micronized progesterone (micro-PG) sustained release tablet formulation in healthy and pregnant rabbits. High pressure compressed gas technology reduces the particle size from 1.72 ± 2.5 μm (micro-PG) to 800 ± 35 nm (nano-PG). DSC and XRD showed that both micro-PG and nano-PG were crystalline and exist as form I. Higher melting enthalpy of nano-PG indicated improved drug stability whereas XRD showed slight reduction in degree of crystallanity following nanonization. Nano-PG demonstrated 2-fold higher solubility in SDS aqueous solution and significantly higher permeability (p < 0.05) across porcine intestine compared to micro-PG. The pharmacokinetics of nano-PG and micro-PG was conducted in healthy and pregnant rabbits. The Cmax of nano-PG was higher in healthy and pregnant rabbits however the difference was significant in healthy rabbits only. The nano-PG demonstrated 30% and 18% higher bioavailability compared to micro-PG in healthy and pregnant rabbits, respectively. In conclusion, nanonization improves solubility, dissolution and bioavailability of PG in rabbits without affecting solid state characters.

Microparticulated Mefenamic Acid with High Dispersion Stability for Pediatric Dosage Form.

Mefenamic acid (MFA), a water-insoluble drug, is used as a suspension in the medical field, but it requires shaking before using to disperse MFA content in the suspension. In previous studies, trials to prepare MFA suspension with high dispersion stability by atomizing MFA by the wet-milling method. However, HPC is used for atomizing MFA. Therefore, the optimum concentration and molecular weight for atomizing MFA have not been investigated. In this study, we investigated the optimum molecular weight and concentration of HPC for the micronization of MFA. As a result, MFA particles became fine particles by adding SDS, and the particle size was also smaller than that of HPC alone. In addition, the suspension with the highest dispersion stability can be obtained when a mixed solution of 1.0% HPC-SL and 0.12% SDS aqueous solution is used. Therefore, this study considers that the addition of SDS and 1.0% HPC-SL aqueous solution are optimal for improving the dispersion stability of the MFA suspension.

Combined effect of NaCl and sodium dodecyl sulfate on the mechanism and kinetics of methane hydrate formation in an unstirred system

Interest in studying an effect of the mixed NaCl + SDS additive on gas hydrate formation is associated with the direct use of saline waters and seawater in hydrate-based technologies for the storage and transportation of natural gases. We performed studies of methane hydrate formation without stirring using pressures of 8, 12 and 16 MPa for water, aqueous solutions of NaCl and SDS, and the mixed additive of NaCl + SDS. A 3 wt% NaCl solution, as a model for seawater, and a 0.1 wt% SDS solution were used. The mixed additive was 3 wt% NaCl+0.1 wt% SDS. Data on the methane solubility, induction time of methane hydrate formation, water-to-hydrate conversion and methane hydrate growth rate, as well as data on morphology of methane hydrate formed with and without additives have been presented. It was found that the mechanism of methane hydrate growth in NaCl solution under static conditions was determined by the morphology of hydrate film at the gas-liquid interface and was pressure dependent. A liquid penetrable hydrate film at the gas-liquid interface formed in the presence of NaCl at moderate pressures (8 and 12 MPa) that allowed capillary-driven hydrate growth with a high rate and water-to-hydrate conversion. At high pressures (16 MPa), methane hydrate growth was limited by formation of impenetrable hydrate film at the gas-liquid interface, that restricted hydrate growth. In contrast to the existing concepts that the addition of NaCl to SDS solutions enhances surfactant micellization and accelerate hydrate formation, we found that SDS micelles did not form under the studied methane hydrate-forming conditions with NaCl. Evidence for SDS hydrate formation in the NaCl + SDS solution have been presented. Mechanisms of gas hydrate nucleation and growth in NaCl + SDS solution taking into account SDS hydrate formation and permeability of gas hydrate film at the gas-liquid interface are discussed.

Prediction of Aqueous Solution Surface Tension of Some Surfactant Mixtures and Composition of Their Monolayers at the Solution—Air Interface

Measurements of the surface tension of the aqueous solution of SDDS mixture with fluorocarbon surfactants (FC) were carried out and considered in light of the surface tension of aqueous solutions of individual surfactants. Similar analyses were made for many other aqueous solutions of binary and ternary mixtures, taking into account the literature data of the surface tension of aqueous solutions of TX100, TX114, TX165, SDDS, SDS, CTAB, CPyB and FC. The possibility of predicting the surface tension of the aqueous solution of many surfactant mixtures from that of the mixture components using both the Szyszkowski, Fainerman and Miller and Joos concepts was analyzed. The surface tension of the aqueous solutions of surfactant mixtures was also considered based on the particular mixture component contribution to the water surface tension reduction. As a result, the composition of the mixed surface layer at the solution–air interface was discussed and compared to that which was determined using the Hua and Rosen concept. As follows from considerations, the surface tension of the aqueous solution of binary and ternary surfactant mixtures can be described and/or predicted.

In-situ measurement of interfacial tension: Further insights into effect of interfacial tension on the kinetics of CO2 hydrate formation

Hydrate-based CO2 capture and sequestration has been viewed as one of the most attractive technologies due to its environmental friendliness and relatively moderate temperature and pressure conditions. In current work, the kinetics of CO2 hydrate formation was investigated at pressures of 2.5–3.5 MPa and temperatures of 274.15–279.15 K and the effect of interfacial tension on CO2 hydrate formation rate was discussed. The interfacial tension between CO2 and aqueous solution during the hydrate formation was in-situ measured via an axisymmetric drop shape analysis method. Under the experimental conditions of this study, the interfacial tension decreased significantly with increasing pressure, while it did not vary obviously with temperature. As to SDS aqueous solutions, the interfacial tension at the gas-liquid interface decreased approximately 12% and 42% when the SDS concentration was 100 ppm and 500 ppm, respectively. In addition, CO2 hydrate formation rate ascended by 59% and 102% when the SDS concentration is 100 ppm and 500 ppm, respectively. Furthermore, a good linear relationship was observed between hydrate formation rate and ratio of driving force to interfacial tension (R2 = 0.9211). This work provides a new idea for rapid estimation of hydrate formation rate.

Simple, sensitive technique for α-amylase detection facilitated by liquid crystal-based microcapillary sensors

Here, we describe a novel sensor that uses microcapillary-confined liquid crystals (LC) and a host-guest inclusion complex, β-cyclodextrin/sodium dodecyl sulfate (β-CD/SDS), to detect α-amylase. All LC droplets confined within the microcapillaries were planar-oriented at the LC-aqueous interface where they came into contact with the non-surfactant solution. In contrast, when the LC droplets come into contact with a surfactant solution (SDS aqueous solution), the surfactant molecules anchor the LC droplets and induce a homeotropic orientation. The degradation of β-CD in the host-guest inclusion complex by α-amylase releases free SDS molecules and facilitates a change in LC orientation, from planar to homeotropic, which corresponds with the development of two bright lines and four petal-shaped optical images. This LC-based microcapillary sensor has a limit of detection (LOD) of 100 ng/mL for α-amylase in aqueous solutions and 500 ng/mL in urine samples. Our sensor exhibits good specificity, sensitivity, and long-term stability for α-amylase, and it provides an uncomplicated, cost-competitive, and non-labeled technique for the detection of α-amylase in both aqueous solutions and human urine samples. Furthermore, the results show an effective detection of α-amylase in human urine samples, demonstrating the feasibility of this sensor in practical applications.

The influence of structure of isomolecular dipeptides of α-L-alanyl-α-L-alanine and β-alanyl-β-alanine on their behavior in aqueous micellar solution of SDS

Thermochemical characteristics of α-L-alanyl-α-L-alanine and β-alanyl-β-alanine interactions with SDS micelles at constant surfactant concentration and at various dipeptide contents have been determined. The anion micelles interaction with α-L-alanyl-α-L-alanine is accompanied by endothermic effects, the interaction with β-alanyl-β-alanine being of an exothermic character. The regularities observed may be attributed to different branching of the structure and hydrophobic properties of dipeptides. The tendencies of changing in the average size and ζ-potential of SDS micelles with different additives of dipeptides have also been examined. Additives of zwitterion dipeptides initiate the compensation of a negative charge and the decrease in size of micelles. In range of low concentration of β-alanyl-β-alanine the abrupt increasing of average micelle size is observed, while at high concentration, the micelle size diminishes.

Study on the triplet states of N-phenyl carbazoles. Transient spectra and singlet oxygen generation

Here we report a study on the photophysics of a series of N-phenyl-carbazoles (N-Ph-Czs) in homogenous solvents and micellar media. The compounds investigated were TCz (N-tolyl-carbazole), TCz-TCz (a 3,3´-linked dimer), and CzPh-Ch2-PhCz (a methylene-bridged N-phenyl-carbazole). Absorption and fluorescence measurements were carried out in ethanol, N,N-dimethyl-formamide and n-decane. Aqueous micellar solutions of SDS, CTAB and Tween-80 were also employed to explore the effect of the organized medium on the photophysics of the N-Ph-Czs. The triplet-triplet absorption spectra of the compounds were characterized by transient absorption spectroscopy. The absorption and fluorescence experiments revealed that although the compounds showed little solvent effects, an unexpected twisting out of planarity of the dicarbazolyl one (TCz-TCz) was observed in micelles. Quantum yields of triplet states and singlet oxygen generation were determined. The high values obtained point to the potential use of these compounds as sensitizers in photodynamic processes, which highlights the potential pharmacological role of these carbazoles. The quenching of the triplet states by electron-acceptors was evaluated and rate constants were near to the diffusion limit. The present results might be relevant for future applications of these compounds in diverse fields.

The influence of technological parameters on the efficiency of the hydrate formation reaction in the system methane — SDS aqueous solutions

The article deals with methane hydrate synthesis in the presence of sodium dodecyl sulfate. The search for optimal conditions for this synthesis in a cylindrical continuous stirred tank reactor was provided. The limit after which the increasing of pressure in the reactor does not make a significant contribution to an increase in the gas content of the product was experimentally detected. The analysis of the impact of cooling rate on intensity of the hydrate formation had been carried out. The mode of gas supply to the reactor, cooling rate and working pressure, ensuring the highest efficiency of the methane hydrate synthesis under the specified conditions, are found.

Dielectric relaxation spectroscopy of aqueous micellar electrolyte solutions: A novel application to infer Dukhin number and zeta potential of a micelle.

The complex permittivities of aqueous SDS solutions, with and without the addition of sodium chloride (NaCl), are measured in the frequency range from 200 MHz to 14 GHz. The SDS concentrations are chosen such that the SDS molecules aggregate to micelles. In this frequency range, the measured spectra allow for the identification of two different relaxation processes. That is, the relaxation of the water molecules at frequencies above 1 GHz and the micellar relaxation at frequencies lower than 1 GHz. It is found that the addition of NaCl to the system mostly affects the micellar relaxation process. In detail, the time constant as well as the amplitude of the relaxation decrease by adding NaCl. These effects are attributed to the change in the solution conductivity that changes the properties of the micelle's electrical double layer. We also extract the Dukhin number of the micelles as a function of surfactant and electrolyte content from the measurements. The Dukhin number is a dimensionless group that describes the influence of the surface conductivity on a phenomena. A regression between Dukhin numbers and free sodium ions is found so that all data collapses on a single curve independent of the surfactant concentration. The surface conductivity is a manifestation of the electrical double layer and we use the Bikerman equation to infer the zeta potential of the micelles. Comparison to literature data shows very good agreement and proves that dielectric relaxation spectroscopy can be engaged to infer the zeta potential of micelles. Abbreviations: CMC critical micelle concentration, DRS dielectric relaxation spectroscopy, EDL electrical double layer.

Surfactant Partitioning in Nanoemulsions.

Using a fractionated silicone oil-in-water nanoemulsion (NEM), which has a high ratio of surface area-to-volume, we investigate surfactant partitioning between the bulk continuous phase and the adsorbed interfacial phase. By adjusting the droplet volume fraction of this fractionated NEM and by using gravimetric and electrical conductivity methods, we measure the bulk and the surface concentrations of an ionic surfactant (sodium dodecyl sulfate, SDS), thereby obtaining a raw adsorption isotherm of SDS on the interfaces of the nanodroplets. To overcome significant uncertainties in the total surface area of this nanoemulsion, we have also measured the macroscopic interfacial tension (IFT) of silicone oil in contact with aqueous SDS solutions using the du Noüy ring method. We then scale the surface concentration of this raw isotherm using an appropriate Gibbs derivative based on the IFT measurement, yielding an adjusted isotherm. We show that this adjusted isotherm can be described using a simple Langmuir equation. In addition, we show that a significant and non-negligible percentage of surfactant typically partitions to nanodroplet interfaces after high-flow-rate emulsification (HFRE) has transformed a microscale premix emulsion into a NEM. We develop a model for predicting the final bulk surfactant concentration after HFRE given the initial bulk surfactant concentration before HFRE. We show that this model can be used to predict trends for surfactant partitioning in polydisperse nanoemulsions after HFRE.

Preparation and Pharmacokinetics Evaluation of Solid Self-Microemulsifying Drug Delivery System (S-SMEDDS) of Osthole.

The study was performed aiming to enhance the solubility and oral bioavailability of poorly water-soluble drug osthole by formulating solid self-microemulsifying drug delivery system (S-SMEDDS) via spherical crystallization technique. Firstly, the liquid self-microemulsifying drug delivery system (L-SMEDDS) of osthole was formulated with castor oil, Cremophor RH40, and 1,2-propylene glycol after screening various lipids and emulsifiers. The type and amount of polymeric materials, good solvents, bridging agents, and poor solvents in S-SMEDDS formulations were further determined by single-factor study. The optimal formulation contained 1:2 of ethyl cellulose (EC) and Eudragit S100, which served as matrix forming and enteric coating polymers respectively. Anhydrous ethanol and dichloromethane with a ratio of 5:3 are required to perform as good solvent and bridging agent, respectively, with the addition of 0.08% SDS aqueous solution as poor solvent. The optimized osthole S-SMEDDS had a high yield (83.91 ± 3.31%) and encapsulation efficiency (78.39 ± 2.25%). Secondly, osthole L-SMEDDS was solidified to osthole S-SMEDDS with no significant changes in terms of morphology, particle size, and zeta potential. In vitro release study demonstrated a sustained release of the drug from osthole S-SMEDDS. Moreover, in vivo pharmacokinetic study showed that the Tmax and mean residence time (MRT(0-t)) of osthole were significantly prolonged and further confirmed that osthole S-SMEDDS exhibited sustained release effect in rabbits. Comparing with osthole aqueous suspension and L-SMEDDS, osthole S-SMEDDS increased bioavailability by 205 and 152%, respectively. The results suggested that S-SMEDDS was an effective oral solid dosage form, which can improve the solubility and oral bioavailability of poorly water-soluble drug osthole.

Preparation of Hollow Polystyrene Particles and Microcapsules by Radical Polymerization of Janus Droplets Consisting of Hydrocarbon and Fluorocarbon Oils.

In this article, we have demonstrated a method for producing hollow particles and microcapsules using oil droplets consisting of hydrocarbon oil (styrene) and fluorocarbon oil (perfluoro-n-octane, PFO) in aqueous surfactant (sodium dodecylsulfate, SDS) solutions. Since fluorocarbon oils are immiscible with hydrocarbon oils, the two oils are separated. Emulsions are prepared by stirring styrene/PFO/aqueous SDS solution mixtures at 80 °C. The type of emulsions and the morphology of droplets in the emulsions are observed by light microscope and scanning confocal fluorescence microscope. It is found that oil droplets with Janus-type morphologies consisting of mutually immiscible styrene and PFO are formed in aqueous SDS solutions. Polystyrene particles are fabricated by radical polymerization of the ternary mixtures of styrene/PFO/aqueous SDS solution at 80 °C. The morphologies of the polystyrene are confirmed by scanning electron microscopy and scanning transmission electron microscopy observations. These observations show the preparation of hollow polystyrene particles with a single hole on the surface. To our knowledge, this method is a novel strategy using the immiscibility of hydrocarbon and fluorocarbon oils. The hollow particles can also be applied to the preparation of microcapsules.