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

研究了粉煤灰、熔融渣和含重金属合成渣对重金属的溶出性能。结果表明：熔融处理和玻璃化处理对防止重金属溶出有一定的效果，但也有一定的例外。在粉煤灰中添加二氧化硅并保持高温可有效防止重金属的溶出。洗脱试验后洗脱液pH值发生变化，影响洗脱性能。富碱金属粉煤灰提高了重金属的淋洗pH值，炉渣的热处理对提高重金属的淋洗效果有一定的促进作用。采用硫酸和盐酸对二次挥发粉煤灰进行了浸出试验，研究了二次挥发粉煤灰的浸出性能。研究结果表明：盐酸溶液能浸出二次挥发飞灰中的Zn、Pb、Cu和Fe，而硫酸溶液不能浸出飞灰中的Pb;含碱量高的灰渣浸出时需要大量酸，浸出液经硫酸浸出后，采用胶结法回收铜。通过pH控制从置换后的溶液中回收Fe和Zn。采用醋酸钠溶液从硫酸浸出后的残渣中浸出铅。

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.