Preferential Crystallization (PC) is a popular process to separate enantiomers, however the nucleation and growth of the counter enantiomer during the process can compromise the enantiopurity of the final crystalline product. This research investigates the use of additives to inhibit the nucleation and growth of the counter enantiomer. In this study, we use Lasparagine monohydrate (L-Asn•H2O) as the preferred enantiomer in crystallization from DLAsn•H2O solutions. Additives include both pure enantiomers of several related amino acid species. This allows investigation of differences in inhibition caused by additives that are of the same chirality and different chirality as the preferred enantiomer. The additives had no discernible effect on the solubility but had a small effect on the metastable limit, with additives tending to slightly widen the metastable zone but also make the zone widths more

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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 (KSP) has been determined for the calcium salt of 4‐octylbenzene sulfonate, and accurate temperature dependent KSP 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 KSP values of the decyl sulfate and dodecyl sulfate salts strongly increase with increasing temperature, with the shorter chain surfactant having significantly higher KSP than its longer chain analogue. At 30 °C the KSP 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.

This work aims to investigate synergy in anionic and zwitterionic surfactant mixtures, as they result in better interfacial properties and micellization behavior. Various mixtures of the pH-insensitive zwitterionic surfactant 3-(decyldimethylammonio) propanesulfonate (Zwittergent 3-10) and sodium dodecylsulfate (SDS) were prepared in aqueous solution at a range of pH values between 2 and 13. The thermodynamic parameters during mixed surfactant adsorption at the air/water interface are obtained and the results show the mixed surfactant systems having superior properties to the constituent surfactants. Experimentally, the mixed surfactant solutions clearly improve the surface activities by lowering the critical micelle concentration (CMC) and lowering the surface tension at the air/water interface. The synergisms are investigated through the interaction parameters estimated from regular solution theory that is used to quantitatively describe the nonideality of surfactant mixtures. High negative interaction parameters are obtained from these surfactant mixtures. Experimental precipitation phase boundaries of SDS in the presence of CaCl 2 were also investigated in mixtures containing pH-insensitive zwitterionic surfactant at & Atthaphon Maneedaeng atthaphon@sut.ac.th

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