Presence Of Mixed Surfactants Research Articles

A new technique for removing the accumulated liquids in gas-condensate pipelines and risers by foam generation in the presence of mixed surfactants

In the present work, a new technique for removing the accumulated liquids in gas-condensate pipes and risers by foam generation in the presence of methane gas and binary mixtures of SLES (sodium lauryl ether sulfate) and TX100 (Triton X-100) surfactants is presented for the first time. A new automated foam production system for assessment of liquid removal efficiency and a new set up for evaluation of foam stability at high pressures and temperatures are also developed. It is shown that at a high pressure of 70 bar and in the presence of optimum concentrations of SLES and TX100 binary surfactants, the generated foam is highly stable even after 24 h which is a new impressive result. It is also shown that in the presence of 1.4 CMC SLES and TX100 = 2 SLES, it is possible to obtain a considerable liquid removal efficiency as high 95 % at different operating conditions, suggesting the superior performance of the proposed technique. The suggested low cost foam pigging technique in the present work can have potential application as an alternative to the expensive risky mechanical pigging regarding continuous removal of the accumulated liquids in the gas wellbores, risers and high pressure gas condensate pipelines in oil and gas industries.

Gas hydrate formation in the presence of mixed surfactants and alumina nanoparticles

Hydrate technology is of considerable significance for industrial natural gas storage and transportation. In this paper, the hydrate formation in surfactants with different ratios of alkyl glycosides (APG) and sodium dodecyl sulfate (SDS) was studied at 275.15 K and 7 MPa. The results show that when the APG content was 20%, the gas storage density reached 117.44 mol/mol indicating the best hydrate formation performance, and it can be further improved to 117.72 mol/mol after adding alumina. There was a secondary induction stage in hydrate formation when compounding. SDS accelerated gas by affecting the surface tension, and APG micelles could promote hydrate aggregation. The promotion effects of SDS and APG were superimposed. The hydrate was distributed in the hollow cylinder of the container. The larger the proportion of SDS, the closer the distance between the hydrate and the bottom.

Techno-biofunctionality of mangostin extract-loaded virgin coconut oil nanoemulsion and nanoemulgel.

Techno-biofunctional characteristics of nanoemulsion and (nano)emulgel loaded with mangostin extracts were elucidated. Crude mangostins from mangosteen peels recovered by virgin coconut oil (VCO), mixed VCO and propylene glycol (PG), and pure PG were used. The extracts were loaded in the dispersed phase in the presence of mixed surfactants (Tween20/Span20) with a varying hydrophilic-lipophilic balance (HLB) from 10.2 to 15.1. Results showed that globular and uniformly distributed droplets of the nanoemulsion were observed. The small particle sizes (typically 18-62 nm) with the zeta potential of -39 to -54.5 mV were obtained when mixed emulsifiers with HLB values of 12.6 and 15.1 were employed. With HLB values of 12.6 and 15.1, nanoemulsions loaded with mangostin extracts prepared with mixed VCO-PG and pure PG-based extracts showed approximately a 2 to 3-fold lower droplet size diameter when compared with the VCO-based extract. For the stability test, all nanoemulsions were stable over three freeze-thaw cycles with some changes in pH, zeta potential, and droplet size. The DPPH● scavenging activity, H2O2 scavenging activity, reducing power and antibacterial activities (E. coli and S. aureus) of the nanoemulsions were greater than their corresponding bulk extracts. Nanoemulgels produced by embedding the nanoemulsions in a hydrogel matrix was homogeneous and creamy yellow-white in appearance. The nanoemulgels had a higher mangostin release (87-92%) than their normal emulgels (74-78%). Therefore, this study presented the feasibility of nanoemulsions and nanoemulgels loaded with mangostin extracts as a promising delivery system for bioactive polyphenol in food supplements, pharmaceuticals and cosmetics.

Controllable synthesis of hierarchical Au/PdAg heterostructures consisting of nanosheets on nanorods with plasmon-enhanced electrocatalytic properties

Hierarchical Au/PdAg heterostructures consisting of PdAg nanosheets epitaxially grown on Au nanorods are synthesized in the presence of mixed surfactants and exhibit remarkable plasmon-enhanced electrocatalytic activity toward hydrogen evolution.

Determination of Trace Levels of Nitrite in Beverages Samples Through Micellar Improved Catalytic Kinetic Spectrophotometry

In this study, a simple and sensitive catalytic kinetic spectrophotometry method for determination of nitrite has been described. The method is based on the oxidation of chlorpromazine by nitrite in presence of mixed surfactants in acidic medium, which results in the decrease in absorbance at 520 nm. Various chemical (such as the effect of acidity, reagents concentrations) and instrumental parameters (time, sample volume and temperature) were optimized. The interfering effects of various chemical species were studied. At the optimum conditions, linear calibration graph was linear in the nitrite concentration ranges of 2.5-125 µg L –1 . The detection limit is 0.71 µg L –1 for nitrite. The relative standard deviation for determination of 25 and 75 µg L –1 were 3.40 and 2.35%, for ten replicate measurements, respectively. The micellar improved catalytic kinetic spectrophotometry showed good analytical performance including good sensitivity, reproducibility, stability and selectivity to nitrite. The method has been applied to determine nitrite in beverages samples with a satisfactory recovery in the range of 97.3–103.8%, showing its promising application for food safety monitoring.

Flotation and adsorption of muscovite using mixed cationic–nonionic surfactants as collector

The performance of the mixed dodecylamine chloride (DDA)/octanol (OCT) surfactants on muscovite flotation was investigated using flotation tests, and their adsorption mechanisms on muscovite and air/water interface were clarified using contact angle measurement, surface tension and molecular dynamics (MD) simulations. The flotation results indicate that the recovery of muscovite rapidly decreases when the pH increases in the presence of only DDA, whereas the recovery of muscovite is high (>77%) over a wide range of pH in the presence of the mixed DDA/OCT surfactants with a ratio of 2/1. Contact angle measurements further confirm that the mixture displays a stronger collecting power than DDA and is a superior collector for the muscovite flotation. The surface tensions of DDA, OCT and their mixture indicate that the mixture is more efficient than DDA at decreasing the air–water interfacial tension and exhibits much better surface activities. MD simulations show that the mixture interacts with the muscovite mainly through electrostatic attraction and hydrogen-bonding. DDA ion is dominant in the interaction between the mixture and muscovite. OCT molecules are co-adsorbed onto the muscovite through the hydrogen-bond interaction and hydrophobic association with DDA ions. Compared with DDA, a well-compacted monolayer is formed on the muscovite surface in the presence of mixed surfactants, indicating a much stronger hydrophobic character of muscovite.

Enhanced enzymatic xylose/cellulose fractionation from alkaline liquor-pretreated corn cob by surfactant addition and separate fermentation to bioethanol

Xylanase xylose/cellulose fractionation can efficiently improve the utilization of xylose and cellulose. Improvement of xylanase performance during hemicellulose hydrolysis can increase xylose/cellulose fractionation efficiency. To utilize xylose and cellulose efficiently, an enzymatic xylose/cellulose fractionation and a separate fermentation bioethanol process were performed. Alkaline liquor-pretreated corn cob was subjected to xylose/cellulose fractionation with xylanase in the presence or absence of the following mixed surfactants: polyoxyethylene(20)-sorbitan-monooleate (0.15% v/v), polyethylene glycol 6000 (0.15% w/v), bovine serum albumin (0.15% w/v), and rhamnolipid (0.005% v/v). The hemicellulose hydrolysis yield (HHY) in the presence of mixed surfactants was 70.5%, which was 66% higher than that of the control (no surfactants added). Optimization of other hydrolysis conditions, such as pH, temperature, liquid-to-solid ratio, xylanase loading, and incubation time, increased the HHY to 86.62%. The xylose in the enzymatic hydrolysate was fermented to ethanol by Candida shehatae, and the cellulose remaining in the solid residues was converted to ethanol by simultaneous saccharification and fermentation with Saccharomyces cerevisiae. In total, 40.67% of the hemicellulose and 76.14% of the cellulose in the raw corn cob was converted to ethanol.

Covalent Incorporation of Ethylenediamine Ligands in the Framework of Periodic Mesoporous Organosilica Nanostructure

The covalent incorporation of ethylenediamine ligands in the framework of periodic mesoporous organosilica (PMO) nanostructure via mixed surfactants self-assembly process has been described. Propyl ethylenediamine group was employed to functionalize the pore channels of ethane-bridged PMO by co-condensation of 1,2-Bis(triethoxysilyl)ethane (BTSE) and (trimethoxysilyl)propyl]ethylenediamine (EDA-TES) in the presence of mixed surfactants (cetyltrimethylammonium bromide and fluorosurfactant (FSN100)) under basic conditions. In order to elucidate the effect of EDA-TES concentration on their mesoscopic organization and pore structure of the final PMO structures, the morphology of PMO nanostructures was investigated in detail by using X-ray diffraction (XRD), transmission electron microscopy (TEM), solid-state nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectroscopy, and N2 adsorption. FTIR and NMR results have confirmed that ethane bridging groups in the final framework have not been cleaved and EDA-TES functions have been covalently anchored to the pore wall of PMO. The structural regularity of mesopore decreases with increasing concentration of EDA-TES in the initial mixtures except for the samples with 15 and 30 wt% EDA-TES concentrations, which exhibits a highly ordered two-dimensional hexagonal symmetry, supported by XRD patterns and TEM. Overall, the increase of EDA-TES contents results in the decreased surface area and total pore volume, indicating that the framework of PMO is covalently functionalized with EDA-TES function.

Morphology, structure, and conductivity of polypyrrole prepared in the presence of mixed surfactants in aqueous solutions

AbstractPolypyrrole (PPy) was prepared from different mixed‐surfactant solutions with ammonium persulfate as an oxidant. Three types of combinations were selected, including cationic/anionic, cationic/nonionic, and anionic/nonionic mixed‐surfactant solutions. The surfactants used in the experiments included cetyltrimethylammonium bromide (cationic surfactant), sodium dodecyl sulfate (anionic surfactant), sodium dodecyl sulfonic acid salt (anionic surfactant), poly(vinyl pyrrolidone) (nonionic surfactant), and poly(ethylene glycol) (nonionic surfactant). The morphology, structure, and conductivity of the resulting PPy were investigated in detail with scanning electron microscopy, Fourier transform infrared spectra, and the typical four‐probe method, respectively. The results showed that the interaction between the different surfactants and the interaction between the surfactants and the polymer influenced the morphology, structure, and conductivity of the resulting polymer to different degrees. The cationic surfactant favored the formation of nanofibers, the addition of anionic surfactants produced agglomeration but enhanced the doping level and conductivity, and the presence of a nonionic surfactant weakened the interaction between the other surfactant and the polymer in the system. In comparison with the results for monosurfactant solutions, the polymerization of pyrrole in mixed‐surfactant solutions could modulate the morphologies of PPy, which ranged from nanofibers of different lengths to nanoparticles showing various states of aggregation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1987–1996, 2007

Effects of mixed surfactants on the volatilization of naphthalene from aqueous solutions

The effects of mixed anionic–nonionic surfactants, Tween40–SDS (sodium dodecyl sulfate), Tween40–SDBS (sodium dodecylbenzene sulfonate), Tween20–SDS and Tween20–SDBS, on the solubility and volatilization of naphthalene from static aqueous solutions were investigated. The experiment results indicated that mixed anionic–nonionic surfactants can solubilize naphthalene synergistically, which was resulted from the reduction in critical micelle concentration (CMC) of the mixed surfactant and the increase in micellar partition coefficient ( K mc) of naphthalene between micelles and aqueous phase. The synergistic effects of mixed surfactants resulted in further reduction in volatilization of naphthalene than that induced by single surfactant. A positive linear correlation was found between the synergistic solubilization ratio (Δ S) and the synergistic inhibitory capacity on naphthalene volatilization (Δ C) in the presence of mixed surfactants. Results from this study imply that mixed surfactants can be employed in environmental remediation to formulate the needed solubility and volatilization of volatile and semivolatile compounds in aqueous solutions.

Highly sensitive spectrophotometric determination of cobalt using o-hydroxyhydroquinonephthalein and hydrogen peroxide in the presence of mixed surfactants

The effects of cobalt(II) and surfactants on the decomposition of various xanthene dyes by hydrogen peroxide have been systematically investigated. A simple and highly sensitive spectrophotometric determination of cobalt(II) (0.05 ∼ 1.2 Μg/10 ml) is proposed. The method is based on the catalytic effect of cobalt(II) on the oxidation of o-hydroxyhydroquinonephthalein (Qnph) by hydrogen peroxide. The proposed catalytic spectrophotometric determination was sensitive, selective, reproducible and virtually unaffected by the presence of other ions; the effective molar “desorptivity” was 4.2×108 l/mol per cm, Sandell sensitivity was 0.15 pg/cm2, and the relative standard deviation was 3.2% at 0.6 ng/10 ml (n=5). The selective assays of cobalt(II) in water samples were also investigated with satisfactory results (95% ∼ 101%).

Preparation and surface modification of poly(vinylbenzyl chloride) latices

AbstractMonodisperse stable latices with reactive methyl chloride surface functionalities were prepared in the presence of mixed surfactants using vinylbenzyl chloride in various ways: as a homopolymer, crosslinked with divinylbenzene, copolymerized with styrene, and overpolymerized onto uniform polystyrene latices. In homopolymerization of vinylbenzyl chloride, the effect of monomer content and concntration and type of surfactant are reported. Nucleophilic displacement of the surface chloride by sulfite ions was accomplished by reaction with aqueous sodium sulfite, without change in latex particle size. Also discussed are ways to control the amount of water‐soluble polyelectrolyte produced as a result of the sulfonation reaction.