| 摘要 |
PURPOSE: To obtain goethite uniform in particle size distribution and having a specified average particle diameter and a specified acicularity ratio by oxidizing part of Fe<2+> at a prescribed temp. in a 1st stage and oxidizing the remainder at a higher temp. in a 2nd stage when oxidation is carried out with H2 O2 , etc., in an aq. medium contg. FeSO4 and Na2 CO3 . CONSTITUTION: In a 1st oxidation process, an aq. H2 O2 soln. is fed in about 10sec and 5-10% of Fe<2+> is oxidized at 40-55 deg.C. In a 2nd oxidation process, the remainer is oxidized at >=55 deg.C to obtain the objective goethite having <=0.2μm particle diameter and an acicularity ratio of >=10% The oxidation in the 2nd process may be carried out by a conventional method if the reaction temp. is higher than that in the 1st process and it is carried out, e.g. by blowing air at 300ml/min rate for 4hr. An embodiment is as follows; gaseous N2 is blown into 1.31 Na2 CO3 soln. having 1.1mol/L concn. at 30 deg.C for 30min, 0.5l FeSO4 soln. having 1.4mol/L concn. is added to the Na2 CO3 soln. and stirred at 52 deg.C for 30min and 25ml aq. H2 O2 soln. having 0.8mol/L concn. is added in 10sec. The temp. of the resultant mixture is increased to 58 deg.C while blowing gaseous N2 and then air is blown at 300mL/min rate for 4hr. |
