Making ash slag harmless and metal recovery from secondary volatilized fly ash

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Elution property of heavy metal from fly ash molten slag and synthesized slag containing heavy metals were investigated. Some of results are follows.Melting treatment and vitrification of fly ash was effective for prevention of dissolution of heavy metals but with minor exception. Adding silica to fly ash and holding high temperature was valid with prevention of dissolution of heavy metals. Elution pH changes after elution test that affect elution property. Alkali metal rich fly ash rises elution pH. Heat treatment of slag had an effect for improve the elution of heavy metals.The leaching of secondary volatilized fly ash with sulfuric acid and hydrochloric acid has been conducted, and leaching properties of ash were investigated. Some of results are follows.Zn, Pb, Cu and Fe were leached from secondary volatilized fly ash by hydrochloric acid solution, but Pb was not leached from the ash by sulfuric acid solution. For leaching the ash containing high amount of alkali content, a large quantity of acid was needed.Cu was recovered from the leaching solution after sulfuric acid leaching by cementation. Fe and Zn were recovered from the solution after cementation by pH control. Pb was leached from the residue after sulfuric acid leaching by sodium acetate solution.