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.

Figure 1

PXRD patterns of (a) commercial SDS cylindrical granules and commercial SDS cylindrical granules aged in a cosolvent with volume ratios of water to acetone of (b) 1:10, (c) 1:17, and (d) 1:25 at 5 °C for 8 h.

Figure 2

TGA scans for commercial SDS cylindrical granules before and after aging in a cosolvent with volume ratios of water to acetone of 1:10, 1:17, and 1:25 at 5 °C for 8 h.

Figure 3

DSC scans of (a) commercial SDS cylindrical granules and commercial SDS cylindrical granules aged in a cosolvent with volume ratios of water to acetone of (b) 1:10, (c) 1:17, and (d) 1:25 at 5 °C for 8 h.

Figure 4

Temperature, volume of water, and volume of acetone vs. time profile of the crystallization process of the SDS·1/8 hydrate.

Figure 5

FTIR spectrum of the produced SDS·1/8 hydrate crystals.

Figure 6

PXRD pattern of (a) the produced SDS·1/8 hydrate, and theoretical patterns of (b) anhydrous SDS from CCDC (database identifier: VECYOR01), (c) SDS·1/8 hydrate from CCDC (database identifier: DODSUL), (d) SDS hemihydrate from CCDC (database identifier: COYGEC10), and (e) SDS monohydrate from CCDC (database identifier: ZZZMAI01).

Figure 7

TGA scans of the produced SDS·1/8 hydrate crystals subjected to (a) 25%, (b) 52%, and (c) 75% RH at 25 °C for 5 days.

Figure 8

PXRD patterns of (a) our produced SDS·1/8 hydrate and (b) our produced SDS 1/8 hydrate subjected to (b) 25%, (c) 52%, and (d) 75% RH at 25 °C for 5 days.

Figure 9

TGA scans of commercial SDS cylinder granules at the (a) first TGA heating and (b) second TGA heating.

Figure 10

PXRD patterns of (a) commercial SDS cylinder granules after the first heating, (b) anhydrous SDS from CCDC (database identifier: VECYOR01), (c) SDS·1/8 hydrate from CCDC (database identifier: DODSUL), (d) SDS hemihydrate from CCDC (database identifier: COYGEC10), and (e) SDS monohydrate from CCDC (database identifier: ZZZMAI01).