Influence of dissolved CO2 on crystallization of epsomite - variation of temperature

Despite the minor amounts of gases dissolved in solutions, they can bring effects on many crystallization systems, which should be regarded as one type of “invisible” impurity. The evidence of the effect of different dissolved gases on crystallization was provided in previous work. The variation of temperature was taken into consideration in this study. CO2 saturated solutions were prepared and air saturated solutions were used as a comparison. The results indicate that the influence of dissolved CO2 on crystallization of epsomite is altered with the variation of temperature. At low temperature, dissolved CO2 tends to suppress the thermodynamics and kinetic aspects of the solutions. With the increase of temperature the trend is reversed, i.e. at high temperature (>30 °C), dissolved CO2 enhances the relating properties of the solutions. At low temperature, the decrease of the pH value could be the dominating factor. Whereas at high temperature when the dissolved CO2 is in a supersaturated state, it starts to nucleate and grow, and partially changes into nano- or microbubbles, which can attach on crystal surfaces and disturb the crystallization process just as impurities do.