Cation solubilities of lignite fly ashes

Abstract

Concentrations of calcium, sodium, magnesium, and iron were determined in water extracts of four lignite fly ashes from three Northern Great Plains mines in order to study the cation solubilities of the various ashes. The main mass of soluble cationic material released was represented by Ca and Na, although a considerable variability existed among the four ashes in proportional and absolute amounts solubilized. Magnesium and iron generally were solubilized at rates roughly one to two orders of magnitude less than Ca and Na. As the ratios of water to ash were increased, generally greater relative amounts of Ca, Mg, and Fe and lesser relative amounts of Na were found in solution. Dust collector ash was higher in sulfate than electrostatic precipitator ash, and approximately 50 percent of the cations solubilized by water from dust collector ashes appeared to exist as sulfates. A considerable portion of the Ca, Mg, and Na is believed to exist in the ash as oxide, thus giving rise to high pH values for water suspensions.