Neutralization of alkaline coal fly ash leachates by CO 2(g)

Abstract

The factors that control pH in alkaline fly ash leachates were investigated in a series of experiments with four fly ashes. The rate at which the fly ash leachates were neutralized by CO 2(g) adsorption and subsequent calcite precipitation was directly proportional to S concentrations in the fly ash leachates because of the effects of SO 4 2− on calcite precipitation was directly proportional to S concentrations in fly ash declined from their initial high values, solution concentrations of Mg increased further slowed calcite precipitation. The incorporation of SO 4 2− and Mg into te cal CaCO 3(s) that is more soluble than pure calcite. As a result, the leachates remained oversaturated with respect to calcite after 18–135 of reaction time. In fly ash leachates in natural systems, the rate of input of CO 2(g) into the leachate is expected to control the overall rate of pH equilibrium.