| 摘要 |
PURPOSE:To relatively readily remove SiO2 in a hydrochloric acid pickled waste liquid of steel stock and effectively perform production of high purity iron oxide, by stirring the hydrochloride-pickled waste liquid of steel stock and then filtering the separated solid content using a filter having a specific pore size. CONSTITUTION:A hydrochloric acid-pickled waste liquid of steel stock is stirred and a solid content in the above-mentioned waste liquid is filtered using a filter having average pore size of >=0.1 to remove silicon content. When the above-mentioned stirring is too strong, aggregating SiO2 is often broken. Therefore, for example when an impeller is used, stirring rate of <=about 200rpm is preferable and when gas bubbling is carried out, gas flow rate of about 0.1-1Nm<3>/min based on the pickled waste liquid of 1m<3> is preferable. When the stirring temperature of the pickled waste liquid is too high, aggregation of SiO2 is promoted, but solubility of SiO2 is remarkably increased. When the stirring temperature of the pickled waste is too low, much time is required for aggregation. Therefore the stirring temperature is preferably about 40-60 deg.C. |
