On the use of titration calorimetry to study the association of surfactants in aqueous solutions

Olofsson, Gerd; Loh, Watson

doi:10.1590/s0103-50532009000400002

Cited by 73 publications

(115 citation statements)

References 51 publications

(83 reference statements)

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“…So, the use of calorimetric or microcalorimetric methods to determine enthalpy, entropy or free energy can be insightful to infer the nature and magnitude of forces associated with the phenomenon(a) under investigation. [28][29][30][31][32] Different volumes of asphaltene-in-toluene solutions, resin-in-n-heptane solutions and also pure solvents were mixed in this experimental work. Although, it is indisputable that the changes in the solubility parameter affect the interaction between solutes from different solvents, our aim here was to force the asphaltenes (from the toluene solution) to come out of solution, by adding a bad solvent (resins containing n-heptane), thus generating large specific surface area of asphaltene particles (colloidal ones) with which resins (in n-heptane solution) could promptly interact.…”

Section: Isothermal Microcalorimetrymentioning

confidence: 99%

A study of asphaltene-resin interactions

Marques¹,

Pereira²,

Bueno³

et al. 2012

J. Braz. Chem. Soc.

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Foi realizado um estudo para investigar a interação entre asfaltenos (em soluções de tolueno) e resinas (em soluções de n-heptano). Para entender melhor o tipo de interação entre essas frações, quantificou-se o consumo de resina quando asfaltenos (dissolvidos em tolueno) foram precipitados com uma solução de n-heptano contendo resina. Os resultados indicaram que a precipitação de asfaltenos ocorre juntamente com a redução na concentração de resina. Os perfis das isotermas de ligação indicaram que a saturação ocorreu em um caso, em quanto que o efeito cooperativo com posterior platô inicial foi observado para duas outras amostras. Estes resultados confirmaram a hipótese de que resinas podem adsorver em asfaltenos, mas não podem evitar floculação e precipitação de asfaltenos. Além disso, resultados de microcalorimetria sugeriram que a resina e asfalteno interagem por forças fracas de van der Waals. Estes resultados estão em contraste com a escola de pensamento predominante desde a década de 1940 que advoga que as resinas podem peptizar e estabilizar asfaltenos.A study was carried out to investigate the interaction between asphaltenes (in toluene solutions) and resins (in n-heptane solutions). To better understand the type of interaction between these fractions, it was quantified the resin uptake when asphaltenes (dissolved in toluene) were precipitated by a resin-containing n-heptane solution. These results indicated the asphaltene precipitation occurs together with a reduction in the resin concentration. The binding isotherm profiles indicated that saturation occurred in one case, while collective association following an initial plateau was observed for the other two samples. These results confirmed the hypothesis that resins can adsorb on asphaltenes but cannot prevent asphaltenes from flocculating and precipitating. Furthermore, microcalorimetric results suggested that the resin and asphaltene interact by weak van der Waals forces. These results are in stark contrast with the school of thought prevalent since the 1940s that resins can peptize and stabilize asphaltenes.

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Section: Isothermal Microcalorimetrymentioning

confidence: 99%

A study of asphaltene-resin interactions

Marques¹,

Pereira²,

Bueno³

et al. 2012

J. Braz. Chem. Soc.

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“…Calorimetric curves of SDS dilution in pure water have been extensively studied in the literature, showing a strong dependence on temperature. 27 The addition of AN or DMF made three regions evident in the ΔH obs versus C SDS curves (these regions are highlighted in the inset in Figure 1a). In the first region, corresponding to the first few injections in the sample cell giving final surfactant concentration below the cmc, the ΔH obs values increased slightly as C SDS increased (Figure 1a, inset, region I).…”

Section: Effects Of the Cosolvents On Sds And Dss Micellizationmentioning

confidence: 99%

“…The cmc value can be considered as the concentration at which the start of micelle formation is detected from the calorimetric curve (the concentration in the beginning of region II). However, as recommended by Olofsson and Loh, 27 the cmc was chosen as the inflexion point in the surfactant dilution calorimetric curve. Finally, at higher final surfactant concentrations, where the ΔH obs values decreased slightly (Figure 1a, inset, region III) when C SDS increased, the added micelles were only diluted in the calorimetric cell.…”

Section: Effects Of the Cosolvents On Sds And Dss Micellizationmentioning

confidence: 99%

“…Whereas the determination of binding isotherms for polymer-surfactant systems is difficult to access by ITC, 27 the number of SDS monomers that interacted with the polymer at each injection in the calorimetric cell remained unknown. Therefore, it was not possible to calculate the exact molar enthalpy change for the PEO-SDS interaction, but only an apparent molar enthalpy change, ΔH ap−int .…”

Section: Effects Of the Cosolvents On Sds And Dss Micellizationmentioning

confidence: 99%

“…27 The cac and cmc values used to calculate the ΔΔG agg values were obtained from calorimetric experiments. For PEO-SDS interaction in pure water, ΔΔG agg = −2.1 ± 0.6 kJ mol -1 indicated that the SDS aggregates were stabilized by PEO.…”

Section: Effects Of the Cosolvents On Sds And Dss Micellizationmentioning

confidence: 99%

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Effect of Acetonitrile and N,N-Dimethylformamide on the Formation of Poly(ethylene oxide)-Sodium Alkyl Sulfate Aggregates

Ferreira

Silva

et al. 2017

J. Braz. Chem. Soc.

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The effects of low contents of acetonitrile (AN) or N,N-dimethylformamide (DMF) on the aggregation of sodium alkyl sulfate surfactants, in the absence and presence of poly(ethylene oxide) (PEO), were investigated using conductivity and isothermal titration calorimetry. The cosolvents slightly changed the critical micellar concentrations and did not alter the critical aggregation concentrations of the surfactants sodium decyl sulfate (DSS) and sodium dodecyl sulfate (SDS) with PEO. However, AN and DMF turned the micellization of the surfactants and their binding to the polymer enthalpically more favorable. For instance, for SDS, the micellization enthalpy, , decreased from close to 0 kJ mol -1 in water to −14.3 kJ mol -1 in the presence of 2.50 mol% AN, and the integral enthalpy change for aggregate formation with the polymer, ΔH agg (int), decreased from −1.1 kJ mol -1 in water to −15.5 kJ mol -1 in the same AN concentration. This was attributed to the modification of the solvation shells of both SDS and PEO by the cosolvent molecules, which reduced the entropic contribution to formation of the aggregates. Consequently, when SDS was replaced with DSS, the AN affected to a lesser extent, with a decrease of 9.1 kJ mol -1 , while the ΔH agg (int) values were not altered, highlighting the influence of hydrophobic interactions in the surfactant aggregation process.

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