Treatment of Lignite Mine Water with Lignite Fly Ash and Its Zeolite

Abstract

As expected, a zeolite formed from lignite fly ash proved to be far more effective in treating the water from the Neyvelli lignite mines than the fly ash itself. Treatment of mine water at different doses with both materials revealed that the zeolite increased the pH from 2.73 to 8.58 and removed most of the hardness, including the Ca and Mg hardness, as well as the acidity from the mine water. In contrast, the fly ash increased the hardness, Ca, Mg, and sulphate in the mine water. The fly ash was partially effective in removing metals like Mn, Ni, Zn, and Cr. In contrast, increased dosing of lignite fly ash zeolite removed 98.6% of the Mn, 99.94% of the Fe, 96.35% of the Ni, 99.30% of the Cu, 19.15% of the Cd, and 100% of the Zn, Pb, and Cr from lignite mine water. The surface of the lignite fly ash particles were initially covered with loosely attached metals that were released in the acidic water, though due to its alkaline nature, it did partially remove the metals from the mine water.