Crystallization kinetics of MgSO₄ · 7 H₂O in presence of tenside

Abstract

The effect of sodium dodecyl sulfate (SDS) on crystallization kinetics and crystal habit of MgSO, . 7 H,O from aqueous solutions at 25 "C was investigated in batch experiments. It highly depends on the supersaturation level. Both increasing supersaturation and rising concentration of the tenside promote the production of needle-like crystals but the influence of the driving force is much more pronounced. SDS increases the crystallization rate and the linear crystal growth rate in length direction of the crystals. To a high degree it also influences properties of the crystallizing solution such as surface tension and viscosity. Der EinfluI3 von Natriumdodecylsulfat (SDS) auf die Kristallisationskinetik und auf die Kristallform von MgSO, . 7 H,O wurde bei 25 "C aus wiiBrigen Losungen in Batch-Experimenten untersucht. Die Tensidwirkung hiingt in starkem MaBe vom Ubersiittigungsniveau ab. Sowohl steigende fTbersiittigung als auch Erhohung der Tensidkonzentration fordern die Entstehung nadelformiger Kristalle, wobei der TriebkrafteinfluB dominiert. SDS erhoht die Kristallisationsgeschwindigkeit und die lineare Kristallwachstumsgeschwindigkeit in Liingsrichtung der Kristalle. Es beeinfluBt auch Eigenschaften der Kristallisetionslosung wie Oberfliichenspannung und Viskositiit in starkem MaBe.JAMES, D. W., CARRICK, M. T., FROST, R . L . : J. Raman Spectrosc. 13 (19x2) 115

Interaction between Epsomite Crystals and Organic Additives

“…The growth of these faces is thus slowed down, resulting in the overdevelopment of the {110} form along the c-axis that changes the crystals' habit from blocky or prismatic to acicular (Figures 3 and 4), or in the formation of tabular {020} forms (Figure 4). Habit changes resulting in the overdevelopment of {110} forms have been observed in the case of epsomite crystals grown in the presence of sodium dodecyl sulfate 50 and urea. 5 Overall, these observations suggest that the interaction of organic additives and epsomite crystals follows a general mechanism that is not highly dependent on the additive structure.…”

“…29 However, little is known about 4 On the other hand, although much research has been dedicated to the study of the interaction between sparingly soluble alkali earth salts and organic additives, very little is known about the interaction of organic additives with divalent cations in highly soluble salts such as magnesium sulfates. To our knowledge only two papers studied the effects of organics, a surfactant (sodium dodecyl sulfate) 50 and urea, 5 on the crystallization of epsomite.…”

Influence of Surfactants on Sodium Chloride Crystallization in Confinement

“…For instance, the presence of sodium dodecyl sulfate was observed to increase the nucleation rate of MgSO 4 . 24 These contradictory examples suggest that the crystal−impurity interactions are highly specific and need to be treated individually. 25,26 Even after numerous studies, no conclusive theory has been developed to predict the influence of surfactants on salt nucleation that allows one to tailor the surfactants for achieving specific effects on the formation of salt crystals.…”

Effect of Sodium Dodecyl Sulfate on the Continuous Crystallization in Microfluidic Devices Using Microbubbles

“…Qazi et al studied the effect of several types of surfactants, including sodium dodecyl sulfate (SDS), on the static crystallization of sodium chloride in a microcapillary by introducing a small volume by capillary action and concluded that surfactants inhibit the crystallization by passivation of the nucleation sites. In another study the nucleation rate of the single‐phase batch crystallization of magnesium sulfate was found to be enhanced by the addition of SDS to the liquid solution . For crystal growth both enhancing as inhibiting trends are observed .…”

“…Various impacts are expected for different surfactant-crystal combinations. Due to the variety of available surfactants no suitable theoretical background to predict the influence of surfactants is available and their application is mainly based on empirical research [1,2].…”