硝酸による酸化鉄の精製 (第1報)

磁鉄鉱の精製について

抄録

Purification of magnetite containing mainly sulfides as impurities was achieved by a combination of physical method, such as flotation, magnetic separation, etc., and chemical treatment with nitric acid. Nitric acid was used because (1) it easily dissolves both sulfides and a part of non-ferrous metallic oxides, (2) it did not dissolve comparatively iron oxides, and (3) it could easily be recovered.
Results of experiment were as follows:
(1) Sulfides in magnetite were almost completely leached by treating the are with 60% nitric acid at 50°C, and with 20-40% nitric acid at 70°C for 3 hours.
(2) The higher the sulfides content of the iron oxide, the more amount of the iron oxide are were dissolved by nitric acid treatment. This might be attributed to sulfuric acid formed by the oxidation of sulfides with nitric acid.
(3) The rate determining step of desulfurization of sulfides was surface chemical reaction of the first order when isolated sulfides particles predominated. After isolated particles were diss olved out, the rate determining step changed into something like apparent diffusion of nitric acid into solid phase or, more exactly, intrusion of nitric acid into the surface of sulfides particles.
(4) The nitric acid and sulfuric acid in the waste solution could be separated by precipitating the basic sulfate Fe₂0₃-2S0₃-H₂0 when the above solution was heated.
(5) The iron sheet was prepared by melting the sponge iron, which was obtained by reducing the above purified are in hydrogen stream, was examined by auto-recording fluxmeter and showed the value of 10, 000-13, 000 as μmax and 0.5-0.3 as Hc.