TREATMENT OF NEUTRAL FLY ASH

摘要

PURPOSE:To easily and efficiently treat neutral fly ash having a wide variation in heavy metal contents with no rise of the pH which is increased by elution of the heavy metals or increase of the quantity of an object to be treated, without mixing a calcium hydroxide source. CONSTITUTION:A phosphoric acid series compound whose molar ratio of alkali metal to phosphoric acid is 1 to 4 is mixed to the neutral fly ash without mixing the calcium hydroxide source to adjust the pH in the range of 6 to 12. The specific phosphoric acid series compound is pref. the one which forms a compound having remarkably low solubility with the heavy metals in the neutral fly ash in a wider pH range such as pH 6-12, so that elution of the heavy metals is surely prevented by its small addition quantity. The initial pH can be maintained by sufficiently corresponding to variations of the components or quantity of the fly ash by a buffering action of the phosphoric acid series compound. A problem in the case of mixing the calcium hydroxide source is eliminated.