PRODUCTION OF MULTIPLE OXIDE POWDER FOR SOFT FERRITE FROM WASTE PLATING LIQUID

PROBLEM TO BE SOLVED: To provide a production method of a multiple oxide powder for a soft ferrite from a plating waste liq. as a source recycling method of a Fe and a Zn in a high concn. Fe-Zn based plating waste liq. SOLUTION: This method is composed of a stage in which a free sulfuric acid in the Fe-Zn based plating waste liq., is neutralized, and the liq. is further neutralized with an iron powder or an alkali agent to pH3-6 to insolubilize impurity such as Al, Cr, Si, P and heavy metal and the impurity is removed by filtration and separation, the stage in which one or >=2 kinds sulfide crystal or sulfide aq. soln. of Zn, Mn, Ni, Cu and Co are blended to this soln. so as to obtain a composition of a ferrite, then, water content is evaporated to obtain a metal sulfide mixed crystal, the stage in which this metal sulfide mixed crystal is heat-treated at a temp. range of 850-1,000 deg.C and the stage in which the powder obtained by the heat-treatment is washed to remove a sulfuric group or Mg, Ca and Na and the powder is dried.