Solubilization of selected polycyclic aromatic compounds by nonionic surfactants

Solubilization of selected polycyclic aromatic compounds (PAC) by biodegradable nonionic surfactants, Tergitol 15-S-X (X=7 or 9) and Neodol 25–7, was investigated and correlated with micellar properties of these surfactants. These PAC include dibenzofuran, phenanthrene, acenaphthene, fluoranthene, and 9-chloroanthracene. Tergitol surfactants are mixtures of secondary ethoxylated alcohols, and Neodol 25–7 is a mixture of similar species but has the alcohol group in the primary position. These surfactants have the same chain length of hydrophobic tails and similar numbers of ethylene oxides. The results show that the Neodol surfactant yields micelles having larger hydrophobic core volume and renders a higher solubilization capacity for the PAC solubilizates in comparison with Tergitol surfactants. In general, aggregation numbers and micellar sizes both increase at elevated temperatures still below the cloud point. The micellewater partition coefficients of these PAC by the nonionic surfactants were well correlated to their octanol-water partition coefficients. Moreover, an estimated log K _ow value of 9-chloanthracene is 4.78.     

Recovering phenanthrene from spiked sand by a combined remediation process of micellar solubilization and cloud-point extraction

A remediation process, which combines the micellar solubilization and the cloud-point extraction technique by a nonionic surfactant Tergitol 15-S-7, was used to decontaminate phenanthrene, as a model hydrophobic pollutant, from spiked sand samples. A first-order kinetics model was employed to describe the solubilization behavior of phenanthrene well. It was observed that presence of surfactant decreased the mass-transfer coefficient of phenanthrene from sand surface to surfactant solutions, however, higher solubilization rate was obtained due to enhanced aqueous solubility and, thus, the larger driving force resulted from solublization. Cloud-point extraction was used to concentrate the phenanthrene solubilized in the washing solutions in an attempt to minimize the amount of wastewater. The extraction was carried out, subsequently, at room temperature by adding sodium sulfate to suppress the cloud-point low enough to induce phase-separation of the surfactant-rich phase with a minimal phase volume from the coexisting water phase. Recoveries higher than 93% were achieved in the combined process of micellar solubilization and cloud-point extraction on ultimate removal of immobilized phenanthrene sorbed on sands. The results showed that this combined process is efficient in recovering phenanthrene sorbed and immobilized on sands from contaminated sites, and produces only minimal amount of wastewater, i.e. less than 3% of its original volume.     

Electrochemically Reversible Solubilization of Polycyclic Aromatic Hydrocarbons by Mixed Micelles Composed of Redox-active Cationic Surfactant and Conventional Nonionic Surfactant

Reduplicate utilization of surfactants is a key factor for Surfactant-Enhanced Remediation (SER) technology to reduce its high operation costs. In order to achieve the reuse of surfactants, this study attempted to construct a novel reversible solubilization system for SER. Three typical polycyclic aromatic hydrocarbons (PAHs) pyrene, phenanthrene, and acenaphthene were controllably solubilized and released by the mixed micelles composed of redox-active cationic surfactant (11-Ferrocenylundecyl) trimethylammoniunm bromide (FTMA) and conventional nonionic surfactant Tween80. Solubilization of PAHs is assumed to be controlled by changing the redox states of FTMA. Cyclic voltammograms tests of FTMA showed the oxidation and reduction potential were 0.4570 and 0.4068 V, respectively, and the peak currents ratio of FTMA and FTMA⁺ was 1.26, verified that FTMA possesses electrochemically reversible property. In FTMA-Tween80 mixed solutions, CMC values demonstrated the nonideal interaction between the two surfactants and the interaction parameters (β) was -5.5296 when the mass ratio was FTMA:Tween80 = 2:8. Due to the synergistic solubilization effect, the apparent water solubilities of PAHs were significantly enhanced by the mixed surfactant, and they were much higher than those in single surfactant. After oxidation, more than 50% of the PAHs in mixed micelles could be released, the cumulative release efficiency of selected PAHs followed the order of pyrene > pherantherene > acenaphthene. Briefly, such results in this article provide a facile method to meliorate the SER technology.     

Osmometric study of commercial surfactants

The micellar weights of Tergitol 15-S-9 (Union Carbide) and of Neodol 25-9 (Shell Chemical Co.) were determined by membrane osmometry in water as 98,000 and 82,000, respectively (36.5 C). Both surfactants contained a small amount of a nonassociating component. The micelles were found to be extremely stable. The micellar weight of Aerosol OT (American Cyanamid) was determined as <5,900 (toluene, 34 C). The results of this investigation indicate the usefulness of membrane osmometry in the determination of micellar weights of surfactants. Information with respect to the stability of the micelles and the dialytic behavior of surfactants in general can be obtained from the osmotic pressure-time curve.     

Partition Coefficients for Continuous Micellar Reaction Processes

The micelle‐water partition coefficients of reactants, products, and catalyst ligands are predicted using UNIFAC‐IF and COSMO‐RS. It is demonstrated that both models represent a reasonable tool for preliminary screening of the micellar systems for a specific continuous reaction process supported by micellar enhanced ultrafiltration (MEUF). The model reaction is the hydrogenation of itaconic acid and its derivatives (dialkyl esters) in the presence of a rhodium‐based catalyst. The effect of the size and nature of the surfactant head group and tail is explored for nonionic and ionic surfactants. The high partition coefficients of the catalyst ligands indicate that no catalyst leakage is expected in MEUF. Based on the concentration dependence of the calculated partition coefficients, the solubilization capacity of micelles is estimated.     

Synthesis and Surface Active Properties of Gemini Cationic Surfactants and Interaction with Anionic Azo Dye (AR52)

A homologous series of new gemini cationic surfactants were synthesized and characterized using micro elemental analysis, FTIR, ¹H-NMR and mass spectra. The surface activities of these amphiphiles were determined based on the data of surface tension. Critical micelle concentration, effectiveness of the surface tension reduction, efficiency of adsorption, maximum surface excess, minimum surface area and critical packing parameter were evaluated. The effect of cationic micelles on solubilization of anionic azo dye, sulforhodamine B (Acid Red 52) in aqueous micellar solution of the synthesized gemini cationic surfactants was studied at pH 6.9 ± 0.5 and 25 °C. The results showed that the solubility of dye rose with increasing surfactant concentration as a consequence of some association between the dye and the micelles. It was also observed that the aggregation of surfactant and dye takes place at a surfactant concentration below the CMC of the individual surfactant. The partition coefficients between the bulk water and surfactant micelles as well as the Gibbs energies of distribution of dye between the bulk water and surfactant micelles were calculated using a pseudo-phase model. The effect of the hydrophobic chain length of Gemini cationic surfactants on the distribution parameters was also reported. The results show favorable solubilization of dye in cationic micelles.     

添加剂对罗丹明B和吖啶黄在SDS溶液中能量转移的影响

罗丹明B(RB)和吖啶黄(AY)在十二烷基硫酸钠(SDS)水溶液中浓度小于临界胶团浓度时,就能发生有效的能量转移,能够反映出SDS形成预胶团的聚集状况。非离子表面活性剂Tween 60,使两种染料分子之间的能量转移受到抑制,分析表明,加入Tween 60后聚集体变小,由于Tween 60的极性头基较大,所以其预胶团结构较紧密,不利于能量转移的发生。在溶液中加入无机盐NaCl和Na2SO4后,虽然聚集体变小,但体系中染料分子仍可以发生有效的能量转移,表明体系中预胶团内部结构较疏松,而且盐的浓度越高,能量转移效率越低,加入无机盐种类不同,能量转移效率也不同,说明无机盐的种类对聚集体的形态有一定影响。     

Surface Properties and Solubility Enhancement of Anionic/Nonionic Surfactant Mixtures Based on Sulfonate Gemini Surfactants

As a class of novel surfactants, Gemini surfactants usually exhibit fairly excellent interfacial properties in aqueous solutions on account of the unique structure. They have significant application and development potential for industrial production. However, the mixing properties of Gemini surfactants with conventional surfactants are the key to their application. The equilibrium surface tension curves of anionic/nonionic surfactant mixtures based on the sulfonate Gemini surfactant (SGS-12) were measured using the Wilhelmy Plate method. The parameters of surface adsorption, the interaction parameters between anionic and nonionic surfactants, and the thermodynamic parameters of micelle formation were calculated from the corresponding equations. In addition, the dynamic surface tension (DST) curves of anionic/nonionic surfactant mixtures were examined through bubble profile analysis, and the diffusion performance parameters were acquired from empirical formulas. The solubilization of pyrene in micelle solutions was studied using UV–vis absorption spectroscopy. The results show that the interaction parameters of all anionic/nonionic surfactants are negative, indicating that there is a synergistic effect on reducing the surface tension. For the SGS-12/OP-10, SGS-12/Tween 80, SGS-12/AEO9, and SGS-12/APG0810 mixtures, the optimum mixing ratios are 6:4, 7:3, 7:3, and 8:2, respectively. The thermodynamic data of micelles show that the formation of mixed micelles for SGS-12/APG0810 mixtures is an enthalpy-driven process. The tendency of DST curves of the SGS-12/APG0810 mixture is similar to that of SGS-12. In comparison with single-surfactant solutions, the anionic/nonionic surfactant mixtures show stronger solubilization capacity toward pyrene.     

Study of the Interaction Between Methyl Orange and Mono and Bis-Quaternary Ammonium Surfactants

The solubilization and interaction of an azo-dye (methyl orange) with dodecyl trimethyl ammonium bromide and cationic gemini surfactants in the series of alkanediyl α,ω-bis[(dimethyl alkyl ammonium)bromide)] referred to as (m-s-m), m = 10, 12, 14 and s = 2, 3, 4 were investigated by means of UV–Vis spectroscopy. Aggregation with the anionic dye was reflected by a hypsochromic shift with a decrease in the intensity of the absorption band. The results also show a bathochromic shift followed by a sharp increase in the intensity of the maximum absorption band λ_max after the critical micellar concentration (CMC). This indicates that the dye solubility increased with increasing surfactant concentration. It was also observed that the aggregation of surfactant and dye takes place at a surfactant concentration far below the CMC of the individual surfactant. The effects of the chain length as well as the spacer length of gemini surfactants on the critical aggregation concentration and CMC were also examined. Moreover, the partition coefficients between the bulk water and surfactant micelles K _S and K _X as well as the Gibbs energies of distribution of dye between the bulk water and surfactant micelles were determined using the pseudo-phase model. The effect of the hydrophobic chain length and spacer of gemini surfactants on the distribution parameters is also reported.     

反胶团酶催化研究新进展

评述了近年来反胶团酶催化研究的新进展。在AOT/异辛烷反胶团中加入非离子型表面活性剂如Tween 85、小相对分子质量聚乙二醇等可有效降低酶与表面活性剂间的静电和疏水作用 ,显著提高酶的活性。对AOT进行化学修饰及合成结构与磷脂类似的新表面活性剂以用其构建新的反胶团体系 ,酶的活性较常用的AOT/异辛烷反胶团体系有显著提高。在反胶团酶反应动力学研究中考虑水含量或底物在反胶团表面吸附的影响等 ,提出了进一步研究的设想 ,包括开发新型表面活性剂以进一步提高酶的活性和稳定性及有利于产物分离     

苯酚在浊点萃取中凝聚层相的增溶规律

采用分光光度法测定了苯酚在非离子表面活性剂单相胶束溶液中和在非离子表面活性剂两相浊点萃取时凝聚层相中的增溶结果.实验表明：溶质在凝聚层相的增溶与表面活性剂形成胶束的结构有关.当凝聚层相的表面活性剂形成正相胶束时,溶质在凝聚层相的增溶规律和在表面活性剂胶束溶液中的增溶规律一致;当凝聚层相的表面活性剂形成反相胶束时,溶质在凝聚层相和在溶液相的浓度关系可理解为在这两种溶剂之间的分配随着凝聚层相的含水率逐渐降低趋近于一定值,溶质的分配系数也趋近于一定值.     

Solubilization of fatty soils by a radiotracer technique

A technique for measurement of solubilized radiotagged triolein and tristearin fatty soils is described. By using surfactant solutions under standardized conditions of temperature and agitation, the solubilized soils are removed from emulsified materials by filtration through 0.1 and 0.01 micron-pore size of filters. The radiotagged fat is recovered by solvent extraction from the clear filtrate by salting-out under centrifugal force and is measured by conventional counting technique. The nonionic alkanol- and alkylphenol-ethylene oxide (EO) adducts solubilized up to 0.058% triolein (weight percentage at 75°C.) while anionic surfactant and sodium tripolyphosphate solubilization was negligible. These findings suggest for these nonionics that solubilization is one of the main, if not the controlling factor in the mechanism of soil removal. Nonionic solubilization was at a maximum for 10 molar EO adducts and at near cloud-point temperatures. For the same surfactant more triolein than tristearin was solubilized, possibly on account of spatial considerations. For tridecanol-10 EO at 0.25% the heat of solubilization of triolein, ΔH_s, was 15 kcal/mole while the heat of micellization of the adduct was 1.3 kcal/mole of adduct. Differences in the colloidal ion lengths of the micelles and their aggregation numbers may explain the differences in solubilization between the anionic and nonionic surfactants tested.     

Styrene Solubilization and Adsolubilization on an Aluminum Oxide Surface Using Linker Molecules and Extended Surfactants

The impact of lipophilic linker and extended surfactant properties on admicelle formation and styrene adsolubilization were evaluated through adsorption and adsolubilization studies on aluminum oxide. While linker-based systems achieved a higher maximum adsorption than extended surfactants, the extended surfactants reached maximum adsorption at a lower aqueous surfactant concentration. Results of solubilization and adsolubilization studies are summarized by the extent of solute solubilization into micelles and admicelles, as captured through the micellar partition coefficient, K _mic, and the admicellar partition coefficient, K _adm. The extended-surfactant-based micelles showed greater solubilization capacity than linker-based micelles. Relative to the effect of the number of propoxy groups for extended surfactants with the same alkyl chain length, the results show that the solubilization capacity increases when the PO number increases for both C12,13- and C14,15-based surfactant series. Thus, adsolubilization using extended-surfactant-based admicelles showed adsolubilization enhancement but required lower amounts of surfactants to form admicelles. These results thus provide insights into external and internal linker-based and extended-surfactant-based admicellar systems and highlight the differences observed between them and admicelles based on conventional surfactant systems.

The temperature dependence of micellar solubilization

The temperature dependence of micellar solubilization was determined in the 180°–140°F. temperature range by using a dye solubilization technique with built and unbuilt solutions of three high-eloud point, commereial surfactants, one anionic of the alkylaryl sulphonate type and two types of nonionic agents. It was found that the logarithm of solubilization in both built and unbuilt solutions was directly proportional to temperature (solubilization was an exponential function of temperature) and that the log solubilization-temperature slopes of the built and unbuilt solutions of each surfactant were approximately parallel.     

Small angle neutron scattering study of structural aspects of nonionic surfactants (Tween 20 and Tween 80) in the presence of polyethylene glycols and triblock polymers

Small angle neutron scattering (SANS) technique has been used to study the micellar behavior of nonionic surfactants, Tween 20 and Tween 80 with additives like polyethylene glycols (PEG with molecular mass 400, 6000, and 15,000) and triblock polymers (TBPs) of varying composition. Surfactant‐additive interactions have been explained on the basis of parameters like aggregation number (N_agg), core radius (R_c), hard sphere radius (R_hs), volume fraction (ϕ) and axial ratio (b/a). The SANS analysis indicate the reduction in values of N_agg of Tween on addition of PEG additive. Shape of Tweens (3 wt %) micelles in the presence of PEG (10 wt %) is found to oblate ellipsoidal. Similarly, the shape of Tween (3 wt %) micelles is oblate ellipsoidal at low concentration of TBPs (1 wt %); however, they become spherical as the concentration of TBP increases to 10 wt %. The shape of micelles of pure TBPs also comes out to be spherical. Results reflects that at low concentration of TBP shape is controlled by surfactant (Tween 20 and Tween 80) while at high concentration of TBP shape of mixed micelle is controlled by TBP. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Importance of micellar relaxation time on detergent properties

As we enter the new millennium, manufacturers of laundry detergents would like to provide new products for the twenty-first century. With the goal of achieving new and better performance characteristics, design strategies for research and development should be defined. This paper highlights the importance of micellar relaxation kinetics in processes involved in detergency. Earlier Shah and coworkers showed that the stability of sodium dodecyl sulfate (SDS) micelles plays an important role in various technological processes. The slow relaxation time (τ₂) of SDS micelles, as measured by the pressure-jump technique, was in the range of 10⁻⁴ to 10¹ s, depending on the surfactant concentration. A maximal relaxation time and thus a maximal micellar stability was found at 200 mM SDS (5 s), corresponding to the least-foaming, largest bubble size, longest wetting time of textile, largest emulsion droplet size, and the most rapid solubilization of oil. These results are explained in terms of the flux of surfactant monomers from the bulk to the interface, which determines the dynamic surface tension. More stable micelles lead to less monomer flux and hence to a higher dynamic surface tension. The relaxation time for nonionic surfactants (as measured by the stopped-flow technique) was much longer than for ionic surfactants because of the absence of ionic repulsion between the head groups. The τ₂ was related to dynamic surface-tension experiments. Stability of SDS micelles can be greatly enhanced by the addition of long-chain alcohols or cationic surfactants. In summary, relaxation time data of surfactant solutions enable us to predict the performance of a given surfactant solution. Moreover, results suggest that one can design appropriate micelles with specific stability, or τ₂, by controlling surfactant structure, concentration, and physicochemical conditions, as well as by mixing anionic/cationic or ionic/nonionic surfactants for a desired technological application, e.g., detergency.     

Spectroscopic and conductometric studies on the interactions of thionine with anionic and nonionic surfactants

In this study, the interaction of thionine, a cationic dye, with anionic [sodium dodecyl sulphate (SDS), lithium dodecyl sulphate (LiDS), and sodium dodecylbenzene sulphonate (SDBS)], nonionic (Tween 20 and Triton X‐100), and binary mixtures of anionic and nonionic surfactants was studied by conductometric and spectrophotometric measurements. The degree of ionisation, the counterion binding parameters, and the equilibrium constants in the premicellar region were obtained from conductivity data. Binding constants of thionine to anionic, nonionic, and mixtures of anionic and nonionic micelles were determined by spectrophotometric measurements. The binding tendency of thionine to anionic micelles followed the order SDBS > SDS > LiDS. The presence of nonionic surfactants increased significantly the binding affinity of thionine to anionic micelles, and the highest binding constant was calculated in the presence of Tween 20. The results obtained from conductometric studies correlated with those obtained from spectroscopic studies. Data concerning dye–surfactant interaction are important for a fundamental understanding of the performance of single and mixed surfactants and for their industrial application.     

Solubilization of octafluoronaphthalene by mixed micelles of fluorocarbon and hydrocarbon surfactants in aqueous solutions

Solubilization of octafluoronaphthalene (OFN) by fluorocarbon and hydrocarbon surfactants in aqueous solutions has been examined to investigate the effects of mixing surfactants and added salt. Diethylammonium perfluoronanoate (DEAPFN) micelles have the most solubilization power toward OFN. The difference in micellar solubilization power will be caused by the hydrophobicity of ionic groups and micellar size. Large positive synergistic effects on solubilization behavior were observed in the DEAPFN-diethylammonium tetradecyl sulfate mixed micellar systems. Solubilization of OFN depended on the concentrations of added salt and the aggregation number, that is, the micellar size.     

Experimental Study of CMC Evaluation in Single and Mixed Surfactant Systems, Using the UV–Vis Spectroscopic Method

In this study, the critical micellar concentration (CMC) of anionic, cationic and nonionic surfactants was determined using the UV–Vis spectroscopic method. Sodium lauryl sulfate (SDS) as anionic, hexadecyl-trimethyl-ammonium bromide as cationic, tert-octylphenol ethoxylates TOPEON (with N = 9.5, 7.5 and 35) and lauryl alcohol ethoxylate (23EO) as nonionic surfactants have been used. Concentration of surfactants varies both from below and above the CMC value in the pyrene solution. In addition, the amount of the CMC was determined using the values from the data obtained from the graph of absorbance versus concentration of surfactants. A comparative study was conducted between the results of the present study and the literature which shows a good agreement, in particular for TOPEO9.5 and LAEO23. Furthermore, the CMC value of SDS (as an ionic surfactant) in the presence of nonionic surfactants was also examined. The result reveals that with addition of small amount of nonionic surfactant to the anionic SDS surfactant, a decline in the CMC value of the anionic–nonionic system relative to the CMC of pure anionic surfactant was observed. In addition and for the first time, the effect of UV irradiation on the size of the micelle formations was studied. It was found that UV irradiation causes the formation of smaller micelles which is of prime concern in membrane technology.     

Nonionic surfactants induced cloud point extraction of Polyhydroxyalkanoate from Cupriavidus necator

Polyhydroxyalkanoate synthesized by Cupriavidus necator DSM 428 was purified from the crude fermentation broth as such by performing nonionic surfactants (Triton X100, Triton X114 & Tergitol 6) induced cloud point extraction. Polyhydroxyalkanoate was extracted into the micelle-rich bottom phase (coacervate phase), while most of the cellular impurities partitioned into the aqueous phase. Cloud point temperatures and the extraction efficiency of different cloud point systems were studied at different pH value and in the presence of additives. Maximum extraction of biopolymer was achieved (recovery of 84.4%) with a purity of 92.49% at 3 pH with the addition of 0.1 M ammonium chloride in the mixed surfactant system at a reduced cloud point temperature of 33°C.