| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain a soln. of rare earth metal components and to recover the rare earth metal components and lead by adding sulfuric acid to optical glass sludge, executing heating treatment, melting rare earth metal components included in the sludge, precipitating lead, barium, silica or the like and separating this precipitation from the soln. SOLUTION: Sulfuric acid is added to optical glass sludge including rare earth metal components generated from optical glass polishing-cleaning stages and waste water treating apparatus incidental thereto, and heating treatment is executed. The concn. of sulfuric acid is preferably regulated to >=5 wt.%, and, in the case of the concn. is 80 to 90%, the separating effect between the soln. of the rare earth metal components and the precipitation of lead and Ba as impurities is made remarkable. The temp. and time in the heating treatment can be changed by the concn. of sulfuric acid, and, in the case of 80% sulfuric acid, about 150 deg.C and about 3 hr are regulated. Sodium sulfate is added to the obtd. soln. of the rare earth metal components, and heating treatment is executed to produce the sodium sulfate double salt of the rare earth metal components, which is preferably separated to recover as precipitation.</p> |
