| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a method for treating a fly ash which efficiently recovers calcium and prevents a heavy metal such as lead from being included into the calcium to be recovered. <P>SOLUTION: This method comprises (A) the step of mixing the fly ash with water to form into slurry; (B) the step of first adjusting the pH value of a mixture of the slurry and hydrochloric acid to 7.0 to 11.0, by adding the hydrochloric acid to the slurry, and obtaining a liquid portion containing a part of the calcium and a solid material containing the remainder of the calcium and various kinds of heavy metals by solid/liquid separation; (C) the step of mixing the obtained solid material with water to form into the slurry, then adjusting the pH value of the mixture to 1.5 to 3.0 by adding sulfuric acid, and obtaining the liquid portion containing copper and zinc and the solid material by solid/liquid separation; and (D) the step of mixing the obtained solid material with the water into the slurry, then adjusting the pH value of the slurry to 13.8 or more, by adding an alkalifying agent such as sodium hydroxide and obtaining the liquid portion containing lead and the solid material containing the calcium hydroxide by solid/liquid separation. <P>COPYRIGHT: (C)2004,JPO</p> |
