| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for efficiently removing Sb in waste water to <=0.1 mg/l or further to a trace concn. of <=0.01 mg/l as an alternative to the conventional method for removing Sb in waste water, in which, for example, a large amt. of a ferric salt is needed to remove Sb sufficiently, the deposit has to be further treated, the cost is consequently increased, and Sb is hardly removed to <=0.1 mg/l even by adding an Al compd. in the presence of a Ca compd. SOLUTION: The valency of the Sb contained in waste water is controlled to 5 in the presence of >=0.7 g/l Ca ion and >=1.5 g/l Cl ion by using an oxidizing agent, >=20 mg/l, preferably >=50 mg/l, Al salt as Al is added, and then the pH is adjusted to >=10, preferably >=11. Otherwise, pH is adjusted in the presence of Ca and Cl ions, the valency of Sb is then controlled to 5, and Sb is removed along with the deposit formed by adding the Al salt. Consequently, the Sb in the waste water is decreased to <=0.1 mg/l and further to <=0.01 mg/l.
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