| 摘要 |
PURPOSE:To economically recover iron hydroxide and phosphoric acid from sludge having a low zinc content by neutralizing an alkaline phosphate soln. with the sludge, filtering it and adding an alkali soln. to the residue to obtain iron hydroxide contg. zinc. CONSTITUTION:When phosphoric acid and iron hydroxide are recovered from sludge contg. zinc phosphate and iron phosphate as principal components and produced during the formation of a phosphate film on the surface of a metal, an alkaline alkali phosphate soln. is neutralized with the sludge and filtered to recover an alkali phosphate soln. An alkali soln. is added to the residue to saponify the residue and iron hydroxide contg. zinc is separated from an alkaline alkali phosphate soln. by filtration. The separated iron hydroxide contg. zinc is washed with about 5-30% alkali soln. to remove phosphoric acid and the alkali is removed by washing with a mineral acid. The iron hydroxide is then washed with water and utilized as starting material for iron oxide for producing soft ferrite contg. zinc.
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