Investigation on Gas Storage in Methane Hydrate

The effect of additives (anionic surfactant sodium dodecyl sulfate (SDS), nonionic surfactantalkyl polysaccharide glycoside (APG), and liquid hydrocarbon cyclopentane (CP)) on hydrate inductiontime and formation rate, and storage capacity was studied in this work. Micelle surfactant solutions werefound to reduce hydrate induction time, increase methane hydrate formation rate and improve methanestorage capacity in hydrates. In the presence of surfactant, hydrate could form quickly in a quiescentsystem and the energy costs of hydrate formation were reduced. The critical micelle concentrations of SDS and APG water solutions were found to be 300x 10-6 and 500x 10-6 for methane hydrate formation systemrespectively. The effect of anionic surfactant (SDS) on methane storage in hydrates is more pronounced compared to a nonionic surfactant (APG). CP also reduced hydrate induction time and improved hydrateformation rate, but could not improve methane storage in hydrates.     

Microstructure of un-neutralized hydrophobically modified alkali-soluble emulsion latex in different surfactant solutions

At low pH conditions and in the presence of anionic, cationic, and nonionic surfactants, hydrophobically modified alkali-soluble emulsions (HASE) exhibit pronounced interaction that results in the solubilization of the latex. The interaction between HASE latex and surfactant was studied using various techniques, such as light transmittance, isothermal titration calorimetry, laser light scattering, and electrophoresis. For anionic surfactant, noncooperative hydrophobic binding dominates the interaction at concentrations lower than the critical aggregation concentration (CAC) (C < CAC). However, cooperative hydrophobic binding controls the formation of mixed micelles at high surfactant concentrations (C > or = CAC), where the cloudy solution becomes clear. For cross-linked HASE latex, anionic surfactant binds only noncooperatively to the latex and causes it to swell. For cationic surfactant, electrostatic interaction occurs at very low surfactant concentrations, resulting in phase separation. With further increase in surfactant concentration, noncooperative hydrophobic and cooperative hydrophobic interactions dominate the binding at low and high surfactant concentrations, respectively. For anionic and cationic surfactant systems, the CAC is lower than the critical micelle concentration (CMC) of surfactants in water. In addition, counterion condensation plays an important role during the binding interaction between HASE latex and ionic surfactants. In the case of nonionic surfactants, free surfactant micelles are formed in solution due to their relatively low CMC values, and HASE latexes are directly solubilized into the micellar core of nonionic surfactants.     

Anionic-nonionic surfactant interaction by nuclear magnetic resonance

Summary The interaction between anionic (sodium dodecyl benzene sulfonate) surfactant and nonionic (Tri and Tetra propylene glycol monomethyl ether) surfactant was studied using nuclear magnetic resonance measurement. It was observed that the addition of sodium dodecyl benzene sulfonate to the solution of nonionic surfactant (Tri and Tetra propylene glycol mono methyl ether) caused an upfield shift of the central protons of the nonionic surfactants. The aromatic protons of sodium-dodecyl benzene sulfonate undergo a very small, almost negligible, downfield shift. The changes in the chemical shift values and the integration values of the polypropylene protons and benzene protons was interpreted in terms of mixed micelle formation with the simultaneous presence of highly fluid mixed micelles of varying compositions.With 2 figures and 2 tables     

Physicochemical properties of mixed surfacant systems: sodium dodecyl benzene sulfonate with triton X 100

The physicochemical properties of a mixed surfactant system were studied under various conditions. The surfactants were anionic sodium dodecyl benzene sulfonate and nonionic Triton X 100. Variation of specific conductivity with concentration was used to determine the critical micelle concentration of anionic as well as the mixed surfactants. Iodine solubilization method was used to determine the CMC of the nonionic surfactant. The interaction parameter between the surfactant molecules were calculated. The wetting, foaming and detergent properties of mixed surfactant systems were studied. The variation of contact angle of the solution with teflon surface as a function of surfactant concentration was found to be a reasonably good method to determine the critical micelle concentration. Viscosity and cloud points were also determined. All these quantities are discussed. Received: 14 January 1998 Accepted: 11 June 1998     

Effect of Surfactants on the Formation,Morphology, and Surface Property of Synthesized SiO2 Nanoparticles

Abstract

This study investigated the effect of cationic, anionic (saturated and unsaturated), and nonionic surfactants on the formation, morphology, and surface properties of silica nanoparticles synthesized by the ammonium‐catalyzed hydrolysis of tetraethoxysilane in alcoholic media. Results indicate that at a relatively low surfactant concentration (1 × 10^?3–1 × 10^?6 M), cationic surfactants significantly affected the growth of silica particles as measured by dynamic light scattering and transmission electron microscopic analyses. In contrast, the anionic and nonionic surfactants showed relatively minor effects in the low concentration range. The magnitude of negative zeta potential was reduced for silica colloids that were synthesized in the presence of cationic surfactant because of charge neutralization. The presence of anionic surfactants only slightly increased the negative zeta potential while the nonionic surfactant showed no obvious effects. At high surfactant concentrations (>1 × 10^?3 M), cationic and anionic surfactants both induced colloid aggregation, while the nonionic surfactant showed no effect on particle size. Raman spectroscopic analysis suggests that molecules of cationic surfactants adsorb on silica surfaces via head groups, aided by favorable electrostatic attraction, while molecules of anionic and nonionic surfactants adsorb via their hydrophobic tails.     

Rheological properties of the aqueous solution for fluorocarbon‐containing hydrophobically modified sodium polyacrylic acid with various surfactants

The interaction of fluorocarbon‐ containing hydrophobically modified sodium polyacrylic acid (FMPAANa) (0.5 wt%) with various surfactants (anionic, nonionic and cationic) has been investigated by rheological measurements. Different rheological behaviors are displayed for ionic surfactants and nonionic surfactants. Fluorinated surfactants have stronger affinity with polyelectrolyte hydrophobes comparing with hydrogenated surfactants. The hydrophobic association of FMPAANa with a cationic surfactant (CTAB) and a fluorinated nonionic surfactant (FC171) is much stronger than with a nonionic surfactant (NP7. 5) and an anionic surfactant (FC143). Further investigation of the effects of temperature on solution properties shows that the dissociation energy E_m is correlated to the strength of the aggregated junctions.     

A Study of the Solubilization of Polar Oily Materials by Alkyl Polyglucoside and Sodium Dodecyl Sulfate in Mixed Surfactant System

The effects of different alkyl chains of nonionic surfactants and solubilized polar oily material on the solubilizing capacity of binary anionic‐nonionic mixed surfactant systems were studied. This system includes surface tension measurements to determine the critical micelle concentration. Results were analyzed using regular solution theory to obtain the mixed micelle and the interaction parameter β, in order to evaluate the type of interactions of surfactants in the mixed micelle. Solubilizing capacity has been investigated by measuring the optical density of solubilized polar oily materials like octanol, decanol, and dodecanol. The solubilizing phenomenon exhibited by mixed surfactants systems showed better results than that of the individual surfactant system. The amount of solubilization in mixed surfactant increases with increase in carbon chain length of alkyl polyglucoside.     

Evaluation of Different Alkyl Polyglycoside Surfactants and Their Combination with Alpha Olefin Sulphonate for Detergency

Among all sugar‐based surfactants, alkyl polyglycosides (APG) are the most successful, with applications ranging from agricultural, chemicals, laundry detergents, and hard surface cleaners to personal care products. APGs show significant synergistic effects in conjunction with anionic surfactants. Alpha olefin sulphonate (AOS) is one such anionic surfactant that is fast gaining acceptability in detergents for its superior performance characteristics and enhanced biodegradability. The present article evaluates the detergency of APG surfactants with three different chain lengths C8/10, C12/14, and C12/18, against fatty soil, particulate soil, and oily soil. Further the synergistic effects with AOS on detergency performance of APG are studied.     

SOLUBILIZATION IN MIXED REVERSE MICELLAR SYSTEMS OF AOT/NONIONIC SURFACTANTS/n-HEPTANE

Solubilization of water and aqueous NaCl solutions in mixed reverse micellar systems of anionic surfactant AOT and nonionic surfactants in n-heptane was studied. It was found that the maximum solubilization capacity of water was higher in the presence of certain concentrations of NaCl electrolyte, and these concentrations increased with the increase of nonionic surfactant content and their EO chain length. Soluibilization capacity was enhanced by mixing AOT with nonionic surfactants. The observed phenomena were interpreted in terms of the stability of the interfacial film of reverse micellar microdroplet and the packing parameter of the surfactant that formed mixed reverse micelles.     

Water solubilization capacity of mixed reverse micelles: effect of surfactant component, the nature of the oil, and electrolyte concentration

Solubilization of water in mixed reverse micellar systems with anionic surfactant (AOT) and nonionic surfactants (Brijs, Spans, Tweens, Igepal CO 520), cationic surfactant (DDAB)-nonionic surfactants (Brijs, Spans, Igepal CO 520), and nonionic (Igepal CO 520)-nonionics (Brijs, Spans) in oils of different chemical structures and physical properties (isopropyl myristate, isobutyl benzene, cyclohexane) has been studied at 303 K. The enhancement in water solubilization has been evidenced in these systems with some exceptions. The maximum water solubilization capacity (omega(0,max)) in mixed reverse micellar systems occurred at a certain mole fraction of a nonionic surfactant, which is indicated as X(nonionic,max). The addition of electrolyte (NaCl or NaBr) in these systems tends to enhance their solubilization capacities further both at a fixed composition of nonionic (X(nonionic); 0.1) and at X(nonionic,max) at 303 K. The maximum in solubilization capacity of electrolyte (omega(max)) was obtained at an optimal electrolyte concentration (designated as [NaCl](max) or [NaBr](max)). All these parameters, omega(0,max) vis-a-vis X(nonionic,max) and omega(max) vis-a-vis [NaCl](max), have been found to be dependent on the surfactant component (content, EO chains, and configuration of the polar head group, and the hydrocarbon moiety of the nonionic surfactants) and type of oils. The conductance behavior of these systems has also been investigated, focusing on the influences of water content (omega), content of nonionics (X(nonionic)), concentration of electrolyte ([NaCl] or [NaBr]), and oil. Percolation of conductance has been observed in some of these systems and explained by considering the influences of the variables on the rigidity of the oil/water interface and attractive interactions of the surfactant aggregates. Percolation zones have been depicted in the solubilization capacity vs X(nonionic) or [electrolyte] curves in order to correlate with maximum in water or electrolyte solubilization capacity. The overall results, obtained in these studies, have been interpreted in terms of the model proposed by Shah and co-workers for the solubility of water in water-in-oil microemulsions, as their model proposed that the two main effects that determine the solubility of these systems are curvature of the surfactant film separating the oil and water and interactions between water droplets.     

Alkylpolyglycoside: Carbohydrate Based Surfactant

Carbohydrates are growing important renewable raw material for surfactant industry. The development of surfactants based on carbohydrate and vegetable oils is the result of the product concept based on the exclusive use of natural resources. Sugar based surfactants are gaining increased attention due to advantage with regard to performance, health of consumer and environmental compatibility compared to some standard product.

Alkylpolyglycoside (APG) is nonionic surfactant prepared from renewable raw materials namely glucose and fatty alcohol. Such products are expected to exhibit surface‐active properties due to the presence of the hydrophilic sugar moiety and the hydrophobic fatty alcohol residues. This article deals with the synthesis of alkylpolyglycoside and the study their surface active properties.

APG was prepared by using fatty alcohol varying in chain length from C8‐C18.

Effect of alkyl chain length of APG on the basic characteristics such as surface tension, interfacial tension, lime soap dispersing power, detergency, foaming, and wetting were studied.

Alkylpolyglycoside prepared from octanol, decanol, and dodecanol are water soluble and shows good surface active properties where as those prepared from long chain fatty alcohols were water insoluble and, therefore, not evaluated for their surface active properties. Incorporation of APG in toilet soap was studied.     

Micellar-enhanced ultrafiltration of cadmium ions with anionic–nonionic surfactants

Micellar-enhanced ultrafiltration (MEUF), a surfactant-based separation process, is promising in removing multivalent metal ions from aqueous solutions. The micellar-enhanced ultrafiltration of cadmium from aqueous solution was studied in systems of anionic surfactant and mixed anionic/nonionic surfactants. The micelle sizes and zeta potentials were investigated by dynamic light scattering measurements. The effects of feed surfactant concentration, cadmium concentration and the molar ratio of nonionic surfactants to sodium dodecyl sulfate (SDS) on the cadmium removal efficiency, the rejection of SDS and nonionic surfactants and the permeate flux were investigated. The rejection efficiencies of cadmium in the MEUF operation were enhanced with higher SDS concentration and moderate Cd concentration. When SDS concentration was fixed at 3 mM, the optimal ranges of the molar ratios of nonionic surfactants to SDS for the removal of cadmium were 0.4–0.7 for Brij 35 and 0.5–0.7 for Triton X-100, respectively. With the addition of nonionic surfactants, the SDS dosage and the SDS concentration in the permeate were reduced efficiently.     

Surfactant effect on the lower critical solution temperature of poly(organophosphazenes) with methoxy-poly(ethylene glycol) and amino acid esters as side groups

 The surfactant effect on the lower critical solution temperature (LCST) of thermosensitive poly(organophosphazenes) with methoxy-poly(ethylene glycol) and amino acid esters as side groups was examined in terms of molecular interactions between the polyphosphazenes and surfactants including various anionic, cationic, and nonionic surfactants in aqueous solution. Most of the anionic and cationic surfactants increased the LCST of the polymers: the LCST increased more sharply with increasing length and hydrophobicity of the hydrophobic part of the surfactant molecule. The ΔLCSTs (T _0.03M− T _0M), the change in the LCST by addition of 0 and 0.03 M sodium dodecyl sulfate (SDS), were found to be 7.0 and 14.5 °C for the polymers bearing ethyl esters of glycine and aspartic acid, respectively. The LCST increase of poly(organophosphazene) having a more hydrophobic aspartic acid ethyl ester was 2 times larger compared with that of the polymer having glycine ethyl ester as a side group. The binding behavior of SDS to the polymer bearing glycine ethyl ester as a hydrophobic group was explained from the results of titration of the polymer solutions containing SDS with tetrapropylammonium bromide. Graphic models for the molecular interactions of polymer/surfactant and polymer/surfactant/salt in aqueous solutions were proposed. Received: 17 February 2000/Accepted: 25 April 2000     

Influence of Sulfolane on ESI-MS Measurements of Protein–Ligand Affinities

The results of an investigation into the influence of sulfolane, a commonly used supercharging agent, on electrospray ionization mass spectrometry (ESI-MS) measurements of protein–ligand affinities are described. Binding measurements carried out on four protein–carbohydrate complexes, lysozyme with β-d-GlcNAc-(1→4)-β-d-GlcNAc-(1→4)-β-d-GlcNAc-(1→4)-d-GlcNAc, a single chain variable fragment and α-d-Gal-(1→2)-[α-d-Abe-(1→3)]-α-d-Man-OCH₃, cholera toxin B subunit homopentamer with β-d-Gal-(1→3)-β-d-GalNAc-(1→4)[α-d-Neu5Ac-(2→3)]-β-d-Gal-(1→4)-β-d-Glc, and a fragment of galectin 3 and α-l-Fuc-(1→2)-β-d-Gal-(1→3)-β-d-GlcNAc-(1→3)-β-d-Gal-(1→4)-β-d-Glc, revealed that sulfolane generally reduces the apparent (as measured by ESI-MS) protein–ligand affinities. To establish the origin of this effect, a detailed study was undertaken using the lysozyme–tetrasaccharide interaction as a model system. Measurements carried out using isothermal titration calorimetry (ITC), circular dichroism, and nuclear magnetic resonance spectroscopies reveal that sulfolane reduces the binding affinity in solution but does not cause any significant change in the higher order structure of lysozyme or to the intermolecular interactions. These observations confirm that changes to the structure of lysozyme in bulk solution are not responsible for the supercharging effect induced by sulfolane. Moreover, the agreement between the ESI-MS and ITC-derived affinities indicates that there is no dissociation of the complex during ESI or in the gas phase (i.e., in-source dissociation). This finding suggests that supercharging of lysozyme by sulfolane is not related to protein unfolding during the ESI process. Binding measurements performed using liquid sample desorption ESI-MS revealed that protein supercharging with sulfolane can be achieved without a reduction in affinity.

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Graphical Abstract ?

     

Kinetics of alkaline fading of methyl violet in micellar solutions of surfactants: Comparing Piszkiewicz's,Berezin's,and pseudophase ion-exchange models

The micellar effect of surfactants of various types on the rate of the reaction between methyl violet and hydroxide ion is studied. The absorption spectra show that the cation of methyl violet is bound by micelles of all types at proper concentrations of surfactants. The observed rate constant in micellar systems containing nonionic Brij-35, zwitterionic 3-(dimethyldodecylammonio)-propanesulfonate, cationic cetyltrimethylammonium bromide and hydroxide surfactants is higher, whereas in solutions of the anionic surfactant sodium dodecylsulfate is lower than that one in the surfactant-free system. Piszkiewicz's, Berezin's, and pseudophase ion-exchange models of the kinetic micellar effect are used for the treatment of the dependences of the above-mentioned constants on the surfactant concentration. The values of the corresponding kinetic parameters are compared and discussed. The influence of nonionic, zwitterionic, and anionic micelles on the reaction rate is discussed on the basis of medium and concentration kinetic effects. The character of the cationic micelles effect is somewhat paradoxical. Although the observed pseudo–first-order reaction rate constant substantially increases in the presence of such micelles, the second order-rate constant in these micelles is lower than the corresponding value in surfactant-free aqueous solution. As a possible explanation, the decrease in the reactivity of the HO^– ions is proposed, owing to their electrostatic association with the cationic headgroups (“diverting effect”).     

Influence of counterion on the interaction of dodecyl sulfates and cellulose ethers

Fluorescence probe techniques together with microcalorimetry and dye solubilization were used to study the interaction between nonionic polymers and anionic surfactants with different monovalent counterions in order to examine the effects of the counterion. The polymers used were the cellulose ethers hydroxypropyl methyl cellulose (HPMC) and ethyl hydroxyethyl cellulose (EHEC). The surfactants were dodecyl sulfates with potassium, sodium, and lithium as counterions (KDS, NaDS, LiDS). The counterion influenced the interaction start concentration as well as the nature of the mixed aggregates formed. The interaction start, according to surfactant concentration, was found to be in the order KDS < NaDS < LiDS for both polymers as well as in aqueous solution. From fluorescence measurements it was found that the KDS-polymer aggregates shield pyrene from water better than the other surfactants, indicating larger aggregates with a more fluid interior. The microcalorimetry measurements confirm that the adsorption of the surfactants onto the polymer is endothermic and entropy driven at the start and as more clusters are formed on the polymer chains the process converts to being exothermic and driven by both enthalpy and entropy.     

混合表面活性剂微乳状液的形成和相行为研究进展

讨论了单一表面活性剂,混合表面活性剂,助溶剂等对油／水微乳状液的形成和相行为的影响。对混合表面活性剂微乳状液的形成和相行为研究工作进行了归纳和总结,重点分析了正负离子表面活性剂微乳状液的相行为和表面活性剂微乳状液的相行为和表面活性剂效率,讨论了微乳状液形成的影响因素,并提出了这一研究领域可能的发展前景。     

Atmospheric and electrochemical oxidation of ascorbic acid in anionic,nonionic and cationic surfactant systems

It is well known that the antioxidant activity of some species in homogenous solutions may not be the same as that in heterogeneous media. This environment dependence is the reason for investigating ascorbic acid antioxidant activity in surfactant solutions. In our study we have investigated the kinetics of atmospheric oxidation and electrochemical oxidation of ascorbic acid in aqueous solutions of the four surfactants: SDS, AOT (anionic), TRITON-100 (nonionic), and CTAB (cationic). For each surfactant the concentrations below and above CMC were investigated. As expected, a general trend in the atmospheric oxidation rate changes in the following manner: the micellar solution of nonionic surfactant shows a faster oxidation rate than that of the anionic surfactant, and the cationic surfactant an even higher one. The more subtle effects were observed with each surfactant concentration change. The influence of the surfactants on the electrochemical behavior of ascorbic acid was also studied. A general conclusion emerging from our investigation is that surfactants shift the ascorbic acid oxidation potential and change the peak current value. This phenomenon is due mainly to the surfactant film formed at the electrode/solution interface.     

Solubilisation of camptothecin by nonionic surfactants and alkyldimethylamine oxides

The solubilisation of poorly soluble antineoplastic drug camptothecin by nonionic surfactants (polysorbates and octylphenol ethoxylates) and alkyldimethylamine oxide surfactants with the alkyl chain length 8 to 16 carbon atoms was investigated. The hydrophobicity of the solubilising agent turned out to be the primary structural parameter controlling the solubility efficiency of camptothecin in an aqueous solution. The quantitative parameter of solubilisation (drug loading coefficient) provided values in the range of 0.1–1.2% and 0.1–1.0% for alkyldimethylamine oxides and nonionic surfactants, respectively. The decreasing number of oxyethylene units and the extension of the hydrophobic part of nonionic surfactant molecule resulted in the increase of camptothecin solubility. From the dynamic light scattering measurements, the hydrodynamic diameter values of camptothecin-loaded alkyldimethylamine oxide and nonionic micelles were found in the range of 4–42 nm and 5–120 nm, respectively. The experimental values confirmed the increase in micellar size with the increasing alkyl chain length. The values of the packing parameter of camptothecin-loaded dodecyldimethylamine oxide micelles indicate their spherical shape at all the investigated surfactant concentrations. A simple computer model of camptothecin-loaded dodecyldimethylamine oxide micelle provided the diameter of the structure cross section which is consistent with the experimental values.      

Anionic–Nonionic Mixed Surfactant Systems: Micellar Interaction and Thermodynamic Behavior

The interactions between an anionic surfactant, viz., sodium dodecylbenzenesulfonate and nonionic surfactants with different secondary ethoxylated chain length, viz., Tergitol 15-S-12, Tergitol 15-S-9, and Tergitol 15-S-7 have been studied in the present article. An attempt has also been made to investigate the effect of ethoxylated chain length on the micellar and the thermodynamic properties of the mixed surfactant systems. The micellar properties like critical micelle concentration (CMC), micellar composition (X_A), interaction parameter (β), and the activity coefficients (f_A and f_NI) have been evaluated using Rubingh's regular solution theory. In addition to micellar studies, thermodynamic parameters like the surface pressure (Π_CMC), surface excess values (Γ_CMC), average area of the monomers at the air–water interface (A_avg), free energy of micellization (ΔG_m), minimum energy at the air–water interface (G_min), etc., have also been calculated. It has been found that in mixtures of anionic and nonionic secondary ethoxylated surfactants, a surfactant containing a smaller ethoxylated chain is favored thermodynamically. Additionally, the adsorption of nonionic species on air/water interface and micelle increases with decreasing secondary ethoxylated chain length. Dynamic light scattering and viscometric studies have also been performed to study the interactions between anionic and nonionic surfactants used.