Authors:Y. Li, G. Fei, Z. Honglin, L. Zhen, Z. Liqiang, and L. Ganzuo
The power–time curves of micellar formation of two anionic surfactants, sodium laurate (SLA) and sodium dodecyl sulfate (SDS),
in N,N-dimethyl acetamide (DMA) in the presence of various long-chain alcohols (1-heptanol, 1-octanol, 1-nonanol and 1-decanol)
were measured by titration microcalorimetry at 298 K. The critical micelle concentrations (CMCs) of SLA and SDS under various
conditions at 298 K were obtained based on the power–time curves. Thermodynamic parameters (
) for micellar systems at 298 K were evaluated according to the power–time curves and the mass action model. The influences
of the number of carbon-atom and the concentration of alcohol were investigated. Moreover, combined the thermodynamic parameters
at 303, 308 and 313 K in our previous work and those of 298 K in the present work for SLA and SDS in DMA in the presence of
long-chain alcohols, an enthalpy–entropy compensation effect was observed. The values of the enthalpy of micellization calculated
by direct and indirect methods were made a comparison.
The composition of mixed micelles and mixed micelle — solution interfaces changes with the concentration and molar ratio of the cationic and anionic surfactants present. The micelle — solution interface includes besides the headgroups of both surfactants, the counterions of the surfactant in excess. The finding of an enhanced binding of counterions to mixed micelles may be of some practical importance in decontamination.
Authors:Elena Blanco, J. Ruso, J. Sabín, G. Prieto, and F. Sarmiento
The interactions of lysozyme and myoglobin with anionic surfactants
(hydrogenated and fluorinated), at surfactant concentrations below the critical
micelle concentration, in aqueous solution were studied using spectroscopic
techniques. The temperature conformational transition of globular proteins
by anionic surfactants was analysed as a function of denaturant concentration
through absorbance measurements at 280 nm. Changes in absorbance of protein-surfactant
system with temperature were used to determine the unfolding thermodynamics
parameters, melting temperature, Tm,
and the heat capacity change, ΔCp,
between the native and denatured states.
The paper describes a radiometric variant of the two-phase titration method for the determination of anionic surfactants of nonsoapy type. The method is based on the titration of an anionic surfactant with Septonex in alkaline medium in the presence of131I-Rose Bengal /abbreviated131I-RB/. The ion associates are extracted into chloroform. The equivalence point is determined graphically from the activity of131I-RB-Septonex associate, which is formed after the consumption of the anionic surfactant and which passes into the organic phase. The influence of131I-RB amount, pH of the titrated medium and of soap presence on the precision of anionic surfactants determination was studied. The detection limit is 2.88 g sodium n-dodecylsulphate in 10 ml of sample.
Authors:Qi Tao, Hongping He, Ray Frost, Peng Yuan, and Jianxi Zhu
Anionic surfactant and silane modified layered double hydroxides (LDHs) were synthesized through an in situ coprecipitation
method. The structure and morphology were characterized by XRD and TEM techniques, and their thermal decomposition processes
were investigated using infrared emission spectroscopy (IES) combined with thermogravimetry (TG). The surfactant modified
LDHs (H-DS) shows three diffractions located at 1–7° (2θ), while there is only one broad reflection for silane grafted LDHs
(H–Si) in this region. The morphologies of the H-DS and H–Si show fibrous exfoliated layers and curved sheets, respectively.
The IES spectra and TG curves indicate that alkyl chain combustion and dehydroxylation are overlapped with each other during
heating from 373 to 723 K in H-DS and to 873 K in H–Si. Sulfate anion transformation process occurs at 473 K in H-DS and 523 K
in H–Si. The derivant of sulfate can exist even above 1073 K. After further decomposition, the metal oxides and the new type
of Si–O compounds are formed beginning at around 923 K in silane modified sample.
Authors:Luiz Carlos Machado, Marcos Tadeu D’Orlando de Azeredo, Hamilton Perez Soares Corrêa, Jivaldo do Rosário Matos, and Ítalo Odone Mazali
La 3+ and Fe 3+ ions and the anionicsurfactant diphenyl-4-amine sulfonate (DAS) has already been studied [ 9 , 10 ]. In these reactions, the metallic ions interact directly with the negative and partial charges formed by the electronic
Authors:Emma Jakab, Erika Mészáros, and Mária Omastová
The thermal stability of polypyrrole
(PPy) samples has been studied by thermogravimetry/mass spectrometry and pyrolysis-gas
chromatography/mass spectrometry in inert atmospheres. PPy has been prepared
by chemical oxidative polymerization using ferric sulfate as an oxidant and
anionic surfactants, such as dodecylbenzenesulfonic acid and sodium dodecylbenzenesulfonate
as co-dopants. For comparison we have studied polypyrrole (PPy-SO4)
prepared without any additive. It was found that the presence of anionic surfactants
improved the thermal stability of PPy. The decomposition of PPy doped with
ferric sulfate and anionic surfactants occurs at relatively high temperature
indicating that chemical interactions exist between the polymer and the surfactants.
The effect of pH on the removal of Co(II) by kaolinite both in the absence and presence of phosphate, citrate, oxalate and EDTA anions, and cationic and anionic surfactants have been investigated and the results obtained are compared with the precipitate formation curve of Co(II) calculated theoretically from published hydrolysis data of the metal ion. In general, the results indicate that the percent adsoprtion of Co(II) increases with the pH and that kaolinite has little affinity for anionic metal complexes. Both strong cationic and anionic surfactants decrease the percent removal of Co(II) by kaolinite but the reasons are different. On the other hand, the weakly ionized anionic surfactant, potassium stearate, enhances the adsorption of Co(II) by kaolinite. The results are discussed in terms of the hydrolysis of Co(II), the properties of kaolinite, and the possible interaction between the ligands tested and both Co(II) and the clay mineral.
Authors:L. Machado, A. Marins, E. Muri, A. Biondo, J. Matos, and I. Mazali
Reactions in aqueous-alcoholic solution between diphenyl-4-amine barium sulphonate (Ba-DAS—anionic surfactant) and the hydrated
sulphates of Fe(III) and Fe(II) ions and their use to ovtain iron oxides are described here. The formation of Fe(II) complexes
was reached by using an excess of Ba-DAS, in absence of light under inert atmosphere. The complexes achieved Fe2[(C12H10NO3S)4]·9H2O and Fe3[(C12H10NO3S)6]·12H2O were characterized by TG/DTG and IR, UV-VIS and 57Fe-Mössbauer analyses.
Interactions of anionic surfactant sodium dodecyl sulphate (SDS) with vesicles formed by synthetic dialkyldimethylammonium
bromides i.e. didodecyldimethylammonium bromide (DDAB), ditetradecyldimethylammonium bromide (DTAB), dihexadecyldimethylammonium
bromide (DHAB) have been examined by using differential scanning microcalorimetry and electron transmission microscopy. The
temperatures and standard enthalpies characterising gel to liquid-crystal transitions increase significantly with increase
of SDS concentration for all investigated systems. It means that incorporation of SDS monomers in these vesicular bilayers
significantly stabilises their gel states. Moreover, in case of DDAB and DTAB vesicle systems added SDS limits kinetic features
of recorded isobaric heat capacity dependencies on temperature observed earlier for the pure vesicular solutions.