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Modeling of Precipitation Phase Boundaries in Mixed Surfactant Systems Using an Improved Counterion Binding Model
Author(s) -
Maneedaeng Atthaphon,
Flood Adrian E.,
Haller Kenneth J.,
Grady Brian P.
Publication year - 2012
Publication title -
journal of surfactants and detergents
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.349
H-Index - 48
eISSN - 1558-9293
pISSN - 1097-3958
DOI - 10.1007/s11743-012-1353-0
Subject(s) - counterion , chemistry , pulmonary surfactant , precipitation , solubility , phase (matter) , salt (chemistry) , solubility equilibrium , phase boundary , inorganic chemistry , sulfonate , thermodynamics , chemical engineering , organic chemistry , ion , sodium , biochemistry , physics , meteorology , engineering
Anionic surfactants, commonly used in household products and the detergency industry, tend to precipitate with divalent counterions in hard water. The unsightly soap scum thus formed also removes the surfactant from the cleaning action. The current research has improved prediction of the precipitation phase boundary for mixtures of surfactants in hard water in two ways: firstly, an accurate value of the solubility product ( K SP ) has been determined for the calcium salt of 4‐octylbenzene sulfonate, and accurate temperature dependent K SP values have been determined for the calcium salts of dodecyl sulfate and decyl sulfate; secondly, improvements in prediction of the precipitation phase boundary have been achieved using an improved model. The K SP values of the decyl sulfate and dodecyl sulfate salts strongly increase with increasing temperature, with the shorter chain surfactant having significantly higher K SP than its longer chain analogue. At 30 °C the K SP of the 4‐octylbenzenesulfonate salt is similar to that of the dodecyl sulfate salt, perhaps due to the similarity in the length of their hydrocarbon tails. A recent counterion binding model proposed by our research group and micellization models have been used to model the precipitation phase boundaries for both single anionic surfactant and binary mixed anionic surfactant systems, improving thermodynamic modeling of the precipitation phase boundary of single and binary mixed anionic surfactant systems. In particular, the improved model of counterion binding has allowed the model to predict the phase boundary accurately over a range of temperatures.