To efficiently recover zinc and lead contained in fly ash by including a process for recovering zinc using a zinc solubilizing agent, a pH adjusting agent and an insolubilizing agent and a process for recovering lead using a lead solubilizing agent and an insolubilizing agent.
Zinc is recovered as zinc insolubilized residue by adding the zinc solubilizing agent to the fly ash to extract zinc and solid-liquid separating, adding the pH adjusting agent and the insolubilizing agent to the extraction filtrate to insolubilize zinc and solid-liquid separating. The impurities in zinc insolubilization filtrate are removed by flocculating and settling and vaporized and concentrated to recover salts and the condensed water. Next, lead is recovered as lead insolubilized residue by adding the lead solubilizing agent to the zinc extraction residue to extract lead and solid-liquid separating, adding the insolubilizing agent to the extraction filtrate to insolubilize lead and solid- liquid separating. The impurities in lead insolubilization filtrate is removed by flocculating and settling to recover the lead solubilizing agent. Further, the lead extraction residue, the salts and sludge discharged in the recovery of the lead insolubilizing agent are dried, then melted and solidified to recover as molten slag.
NAGASAWA MATSUTARO
YAMANAKA TAKESHI
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