การกําจัดซัลเฟตจากนํ้าระบายเหมืองแร่โดยการสร้างตะกอนเอททริงไกต์ที่อุณหภูมิสูง

Abstract

The aim of this research was to investigate the optimum conditions for sulfate removal in lignite coal mine drainage by ettringite precipitation. Central Composite Design (CCD) was used to examine the effects of temperature, reaction time, and Al/S ratio (mole basis) on the sulfate removal efficiency. The statistical analysis showed that the Al/S ratio has a significant effect on the sulfate removal efficiency, which depends on the temperature. When using a low Al/S ratio, the sulfate removal efficiency increases with the increasing of the reaction temperature. Conversely, when using a high Al/S ratio, the sulfate removal efficiency reduces at high reaction temperature. The optimum conditions obtained from the prediction equation were a temperature of 30 °C, a reaction time of 0.5 h, and the Al/S ratio at 3.65. At optimum conditions, it was found that the sulfate removal efficiency was up to 80% when treating Lamphun and Lampang mine drainages. In addition, the results of the XRD pattern of precipitates obtained from Lamphun mine drainage found a majority of ettringite (Ca4Al2(SO4)3(OH)12) when the precipitation was done at low temperatures. On the other hand, monosulfate (Ca4Al2(SO4)(OH)12) and calcium carbonate (CaCO3) were found to be a majority when the precipitation at high temperatures.