| 摘要 |
PROBLEM TO BE SOLVED: To prevent selenium from being eluted by mixing a selenium-contg. industrial waste and cement, settling the mixture until the elution of selenium is stabilized, then adding ferric ion to it while keeping the mixture at a specified pH and curing the admixture. SOLUTION: First, a selenium elution test from a selenium-contg. sludge obtd. after treating waste water is made by using aq. solns. each having a different pH. Namely, an aq. soln. previously so regulated that the eluate is controlled to pH 0-14 and contg. hydrochloric acid and sodium hydroxide is used as a solvent, the solvent is mixed with the selenium-contg. sludge (contg. 70.6% water and having 51,000 mg/kg total selenium content in a dry state) and agitated, and then the selenium content in the filtrate is measured. Consequently, the concn. of the eluted selenium is rapidly increased outside pH 3.5 to 6.5 range. The fact shows that pH control is important in the treatment of a selenium-contg. waste. Meanwhile, since pH is controlled to 10-12 in the conventional method of caking the mixture with cement, the elution of selenium is not prevented. |
