JPS5836932A - Manufacture of ferromagnetic oxide - Google Patents

Abstract

PURPOSE:To obtain a ferromagnetic oxide easily especially through normal temp. reaction independent of reaction temp. characteristics, by reacting lepidocrosite with ferrous ions in >=6pH value, especially in an alkaline range. CONSTITUTION:A soln. contg. ferrous ions, for example, as FeCl2, is added to a soln. of lepidocrosite (gamma-FeOOH) and reaction is accelerated by always keeping pH>=6 to give a ferromagnetic oxide consisting of magnetite, ferrite (Fe3O4) as shown in the formula. At that time, an amount of ferrous ions added is 1/2 of gamma-Fe in mole ratio as shown in the formula. This reaction occurs in a moment especially even at a low temp. gamma-FeOOH is obtained by oxidizing ferrous ions in an acidic range of a soln. at normal temp.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a spinel-type ferromagnetic oxide.

As a method for producing spinel-type ferromagnetic oxides, an alkali is added to an aqueous ferrous salt solution to form a white precipitate of ferrous iron, and then the aqueous solution in which this precipitate is suspended is gradually oxidized to produce magnetite or A so-called wet oxidation method for producing iron oxyhydroxide or a mixture thereof has been developed, and this method is already in practical use as an effective method for producing ferrite and treating waste liquids containing heavy metals.

In this method, setting conditions such as reaction temperature, pH setting, oxidation conditions, etc. are important, and it must be carried out under specific conditions to produce magnetite and ferrite. Figure 1 shows how the crystal structure of the iron compound produced changes depending on the alkali addition ratio and the degree of 1 reaction when an alkali is added to a ferrous salt solution and then an air oxidation reaction is actively carried out. This is what is shown. As is clear from the figure, Fe3O4 is produced at a high reaction temperature, and Feα is produced at a low reaction temperature, so the reaction must be carried out at a high temperature to obtain magnetite, which is a magnetic oxide particle. However, it is not impossible to perform the oxidation reaction at room temperature without relying on the above reaction conditions, but it requires special equipment for the oxidation treatment, and the oxidation reaction takes a long time. Various problems remained in addition to processing operations and processing time.

The present invention solves the above problems at once; it does not require an oxidation reaction, and the degree of source of one reaction is high or low.

The present invention provides a method that can instantaneously generate ferromagnetic oxides using simple equipment, almost unaffected by pH settings and other processing conditions. That is, the present invention is a method in which lepidocrocite and ferrous ions are reacted in a solution with a pH of 6 or higher to completely generate a ferromagnetic oxide.

The present inventor has discovered that when ferrous ions are added to a liquid of Lepidocroci (rPeoOH), magnetite (F*5O4) is produced by the following reaction under conditions where the pH of the liquid is 6 or higher.

2rFeOOH+FeOH→Fe3O4+f-50+
H”rFeooH converts ferrous ion to Fe in a strongly acidic region.
It is known that the above reaction occurs because ferrous ions are adsorbed in the form of FeOH when the pH of the liquid is 6 or higher, especially in the alkaline region. Precipitates as magnetite.

During the above reaction, H is produced and the liquid returns to the acidic side, so it is necessary to maintain the pH of the liquid at 6 or higher during the reaction by adding an alkali. However, if the liquid is strongly alkaline, there is no need to add alkali. Also, the pH of the solution when adding ferrous ions
When the pH is 6 or less, an alkali is added to adjust the pH to 6 or more. In this way, the pH range of the solution at the time of addition of ferrous ions does not matter as long as the pH of the solution during the reaction is maintained at 6 or higher. Furthermore, ferrous ions may be supplied in either solid or liquid form.

As is clear from the above formula, the amount of ferrous ion added is 4 of the total amount of rFeooH in terms of molar ratio.

If the amount of FeooH added is small, rFeooH remains in the solution, making it impossible to obtain highly pure magnetite.

Further, in the above reaction, the reaction temperature does not matter at all. This is because adsorption of ferrous ions to γFe0OH occurs over the entire temperature range in a solution with a tip pH of 6 or more.

In addition to these adsorption functions, the reason why the above reaction occurs instantaneously even at low temperatures is that rFeoOH has a crystal structure very similar to Pg304, and the activation required for the structural change to F,304. This is thought to be because the energy is extremely small.

Note that rFeooH can be obtained by oxidizing ferrous ions in a normal temperature solution in an acidic region.

Therefore, by generating γFe00H in a liquid containing heavy metal ions, such as heavy metal-containing waste liquid, and subsequently performing the above-mentioned treatment on this solution, heavy metal ions can be incorporated into the crystal lattice using the γFe00H generated in the liquid. You can get ferrite. Of course pH
γFe00H may be added to the waste liquid containing 6 or more heavy metals, and in either case, magnetite and ferrite can be produced with simple operations without requiring special equipment.

As described above, according to the present invention, the reaction temperature is not influenced by the reaction temperature characteristics as shown in FIG. It has the excellent effect of being able to produce magnetite and ferrite, and particularly easily producing ferromagnetic oxides through room temperature reactions. Examples of the present invention are shown below.

(Example 1) 750 rrL of pH 5.5 solution containing 59 FaCl
Blow 1.5 tons of air per minute into liquid 2+ at a temperature of 25°C, Fg
The ions were oxidized to produce rFeoOH'. Furthermore, 2.52 FeCl2 was added to this solution (pH 5.5), and the pH of the solution was adjusted to several levels in the range of 5 to 10 by changing the amount of alkali added to the solution. When we investigated the precipitates formed in the liquid when the pH was 4 or higher, black precipitates were formed instantaneously (5 to 6 minutes), and all of these were Fa3Ql, but at pH 5.8 or lower, the liquid There was no change in color, and the precipitate obtained was a mixture of rFgooH and Fg(OH)2. The components of the precipitate were analyzed by powder X-ray diffraction, Mössbacher earth vector, electron microscopy, and chemical analysis. This also applies to the following examples.

Figure 2 shows particles of rFe(1)H generated in the liquid.
The figure shows the amount of F generated in the liquid when the pH is set to 6.4 or higher.
It is an electron micrograph showing particles of a304.

(Example 2) After generating γFeα in a solution using 52 FgC4 in the same manner as in Example 1, the solution was adjusted to an alkaline region (pH 8
, 9, 10, 11), and 2.5f of FeC1 is added to these.
simultaneously adding a pH 2 solution containing e and an alkaline solution,
The pH of each solution was maintained at 8.9.10.11. After adding all the FaC1q solutions, complete FgsO4 was produced in the solutions at both pHs. 1 Also, 2.5
2 F#C/J as an alkaline suspension with pH 8, 9, 10, 11, and added with γFe00H containing pH 8, 9,
The results were the same when suspensions of 10 and 11 were added.

(Example 5) In the same liquid (PH8, 9, 10, 11) as in Example 2,
M? +, C6", Cu", CI", Z?L'+
After adding 5 to 5 g of FeC1y to Fe1C, a solution containing 2.51 FeC1y was added to each solution at the same time as an alkali as in Example 2, and the final pH of the solution was adjusted to 8, 9,
It was kept at 10.11.

All precipitates formed in each solution were ferrite containing these metal ions. It has been found that these metal ions are completely incorporated into the lattice points of the ferrite and re-eluted only when the ferrite slightly dissolves in an acidic region of pH 3 or less. Furthermore, when ferrite is formed, the concentration of metal ions in the solution is 0 at a liquid temperature of 25°C.
It was less than 0 lppm.

The same results were obtained when the same test was conducted on other liquids containing metal ions such as T and +'Z Ns2': Mn''+ Cr.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the changes in the product with respect to the alkali addition ratio and reaction temperature in the conventional method, Figure 2 is an electron micrograph of rFeooH added to the liquid, and Figure 3 is the magnetite produced by the method of the present invention. This is an electron micrograph. Patent applicant Nippon Electric Environmental Engineering Co., Ltd. Figure 1 nOH/2Fe + Figure 2 Figure 3

Claims (1)

[Claims] (2) Total amount of lepidocrocite 2. The method for producing a ferromagnetic oxide according to claim 1, wherein about 2 ferrous ions are added at a molar ratio of 1 to 1.