Myung Gyu Lee

Effects of sodium laurylsulfate on crystal structure of calcite formed from mixed solutions

Sodium laurylsulfate (SLS), an anionic surfactant, was used for tailoring calcite via a solution route. SLS was dissolved in calcium and carbonate source solutions at various concentrations and critical micelle concentrations (CMCs). The crystallized particles were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), laser-scattering particle size measurements, and thermogravimetric analysis (TGA). Energy dispersive spectroscopy (EDS) analysis was carried out to measure sulfur profiles on the surface of the particles. SLS tended to produce small calcite particles in the carbonate source solution, whereas this effect was not obvious in the calcium source solution. It is believed that the electrostatic repulsion force in the carbonate source solution contributes to the different particle refining effects of SLS seen in the two solutions.

Effects of temperature on the carbonation of flue gas desulphurization gypsum using a CO2/N2 gas mixture

The carbonation of flue gas desulphurization (FGD) gypsum using a CO2/N2 gas mixture was investigated to study the feasibility of using the flue gas directly in the gypsum carbonation. The effect of the reaction temperature on the carbonation reaction and the carbonation conversion efficiency of the samples were considered. In this study, the carbonation conversion efficiency was calculated using a new method for decreasing the error range from a sample containing unreacted gypsum. The carbonation reaction at 40°C was nearly twice as fast as the reaction at room temperature. In addition, the carbonation conversion efficiency at 40°C (96%) was nearly the same as that at room temperature. However, the efficiency decreased significantly with temperature, especially above 60°C. It can, therefore, be concluded that the direct use of flue gas in gypsum carbonation is most feasible at 40°C. The temperature of carbonation strongly affected the CaCO3 polymorphs and the morphological characteristics. Calcite with various shapes was the dominant (40–90%) phase at all temperatures. At temperatures below 40°C, spherical-shaped vaterite was pronounced, while needle-flower-shaped aragonite was dominant at temperatures above 80°C.