Reproducible Crystallization of Sodium Dodecyl Sulfate·1/8 Hydrate by Evaporation, Antisolvent Addition, and Cooling

Abstract

Sodium dodecyl sulfate (SDS)·1/8 hydrate (NaC12H25SO4·1/8H2O) crystals were successfully produced by evaporation, antisolvent addition, cooling crystallization, and isothermal aging in a common stirred tank. A clear 33.3 wt % SDS aqueous solution was concentrated by evaporation to a 60 wt % coagel consisting of numerous SDS hydrates and water. The coagel was transformed to a clear solution when two times the volume of acetone relative to the water remaining were added. By this fluid property, a controlled crystallization was made possible in a homogeneous solution. Moreover, acetone with a water-to-acetone volume ratio of 1:15 was then added as an antisolvent to induce crystallization of SDS·1/8 hydrate by cubic addition. Finally, cooling crystallization and isothermal aging were carried out to further increase the yields and gave monodispersed particle size. The stability test showed that the produced SDS·1/8 hydrate could be stored at various relative humidity environments for at least 5 days.

A Novel Hydrate Form of Sodium Dodecyl Sulfate and Its Crystallization Process

“…Those hydrate forms, excluding SDS·1/8 hydrate, were prepared and formed in purely aqueous media. It was reported that its 1/8 hydrate is stable under normal conditions. , In addition, one crystal structure of the anhydrous SDS form has already been determined using a combination of synchrotron radiation powder diffraction and molecular modeling, while SDS is apt to absorb and bind to water molecules in air at ambient conditions.…”

“…Oftentimes, a short evaporation time like this makes it difficult to have a good control over the crystalline form of its product to be specific. SDS is highly soluble in water and forms micelles in aqueous solution above 8.2 mM, which is its CMC at 25 °C. , As the solute concentration of SDS in aqueous solution increases by reducing its water content, the SDS solution will pass through several complex phases of micelles, liquid crystals, and coagels toward the formation of a very thick slurry, causing poor mixing, and heat and mass transfer . The strong affinity to water of those structures often makes the removal of water from the slurry with high viscosity very difficult and energy-consuming.…”

“…However, such understanding of those SDS crystallization subjects was constrained to the “cooling” method, in aqueous solutions, and on a small scale, such as sealed capillary tubes, ,, or sample cells for various instruments, FTIR, DSC, , dynamic light scattering (DLS) and small angle neutron scattering (SANS) . More recently, we have developed a controllable SDS crystallization process, which integrates evaporation, antisolvent addition, and cooling methods, to produce stable SDS·1/8 hydrate-specific solids . The aims of the present study were to screen pseudo-polymorphs with the use of organic solvents, and to further develop the crystallization process directly following from the synthesis of SDS.…”

“…Noticeably, it was said that the commercially purchased SDS solids are indeed a mixture of various hydrate forms rather than a specific hydrate form. 25 Moreover, SDS may undergo an autocatalytic, acid-catalyzed hydrolysis that produces 1-dodecanol and hydrogen sulfate, and its rate of hydrolysis is dependent on concentration, temperature, and pH. 26,27 Therefore, in the present study, we were the first to re-examine our purchased SDS products by several solid-state characterization tools, including powder Xray diffraction (PXRD), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), Raman spectroscopy, dynamic vapor sorption (DVS), and elemental analysis (EA).…”

Surface-Induced Crystallization of Sodium Dodecyl Sulfate (SDS) Micellar Solutions in Confinement

“…Due to its wide range of applications, the phase behavior of aqueous solutions of SDS and its hydrated crystals, at equilibrium and in static conditions, has been extensively investigated over the past decades. ,,− Nevertheless, the kinetics of phase transformations upon variations of temperature and concentration and those occurring in the vicinity of the interfaces remain largely unresolved. Here, we focus on transformations from the micellar L 1 to the crystalline C phase that occur upon cooling at fixed surfactant concentration.…”