| 摘要 |
PURPOSE:To easily obtain low-SiO2 iron oxide of superior quality at a low cost from waste liquor discharged after pickling a steel plate, etc. with hydrochloric acid, by adding a coagulant to the waste liquor to coagulate silicon components, removing the silicon components by filtration, and thermally decomposing the remaining waste liquor by roasting. CONSTITUTION:To waste liquor discharged after pickling a steel plate, etc. with hydrochloric acid is added a coationic polyacrylamide type polymer coagulant in >=0.04 weight ratio of the coagulant to silicon components in the waste liquor expressed in terms of SiO2. The waste liquor contg. the coagulant is cured for >=20min to grow coagulated particles, and this coagulated SiO2 is separated by filtration. After removing the SiO2, the waste liquor is thermally decomposed by roasting to manufacture iron oxide. By this method low-SiO2 iron oxide contg. <=0.009wt% SiO2 can be manufactured easily by additionally installing a few apparatus such as a coagulating vessel and a filter in existing facilities for recovering hydrochloric acid. |
