JPH01264933A - Production of iron hydroxide or iron oxide - Google Patents

Abstract

PURPOSE:To obtain easily and inexpensively pure iron (hydro)oxide by carrying out electrodialysis of a liquid suspension contg. iron (hydro)oxide, cations, and anions with an ion exchange membrane, and removing the cations and the anions. CONSTITUTION:A liquid suspension contg. iron hydroxide, iron oxide, together with cations and anions as impurities is prepd. by prepg. iron hydroxide by the hydrolysis of iron salt such as iron sulfate, iron chloride, etc., and oxidizing, etc., further the product of the hydrolysis. The cations and anions are removed from the liquid suspension by feeding the liquid suspension contg. the impurities to an electrodialysis cell provided with ion exchange membranes and carrying out electrodialysis of the suspension. The liquid suspension freed of the cations and anions is then concentrated, thus, particles of pure acicular iron hydroxide and acicular iron oxide, are obtd. Magnetic particles having high output and high density recording characteristic are obtd. by reducing the iron hydroxide particles or iron oxide particles in hot reducing gas.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application in Family Business] The present invention relates to a method for producing iron hydroxide or iron oxide.

[Conventional technology]

In recent years, there has been active development of magnetic particles having characteristics suitable for high output and high density recording, magnetic particles having large saturation magnetization, and high coercive force.

Magnetic particles having such characteristics are generally made from acicular crystal hydrated iron oxide particles, acicular crystal iron oxide particles containing disembodied metals other than iron, and are heated in a reducing gas at 350° C. It can be obtained by heating reduction at about ℃. The raw material, acicular crystal hydrated iron oxide particles, acicular crystal iron oxide particles,
Generally, iron hydroxide is obtained by hydrolyzing iron and ferric salts such as iron sulfate, iron chloride, iron nitrate, and the like, and is further oxidized. In this production method, salt is produced by hydrolysis. When magnetic particles are manufactured from iron hydroxide containing this salt, the salts contained as impurities reduce the above-mentioned excellent properties of the magnetic particles. It is being removed. A filter press is used to remove the salts, partly due to the high viscosity of the iron hydroxide suspension.

[Problem to be solved by the invention]

However, there is a problem in that the filter press cannot sufficiently remove salts in iron hydroxide.

In order to achieve sufficient salt removal, the iron hydroxide suspension must be sufficiently diluted, which requires a large amount of water, and the diluted suspension must be thoroughly diluted. Although large-scale concentration and filtration equipment, two dispersion and suspension equipment are required to obtain this, the equipment costs and costs associated with the removal process are enormous.

[Means to solve the problem]

The present inventors have conducted extensive research into methods for producing pure iron hydroxide or iron oxide. As a result, a suspension of iron hydroxide or further oxidized iron oxide obtained by hydrolyzing iron salts is supplied to the ion exchange membrane electrodialysis tank, and the iron oxide contained in the suspension causes salt formation. By removing cations and anions by electrodialysis, they succeeded in producing pure iron hydroxide or iron oxide, leading to the completion of the present invention.

That is, the present invention supplies a suspension containing iron hydroxide or iron oxide, cations and anions to an ion exchange membrane electrodialysis tank, and performs electrodialysis to remove cations from the suspension. and a method for producing iron hydroxide or iron oxide, characterized by removing anions.

According to the present invention, almost complete removal of cations and anions from a suspension containing iron hydroxide or iron oxide and cations and anions can be achieved, and moreover, economically pure hydroxide It is possible to produce iron or iron oxide.

The iron hydroxide in the present invention includes ferrous hydroxide and ferric hydroxide.
Iron droplets, iron oxyhydroxide, etc. are used.

Further, as the iron oxide, ferrous oxide and ferric oxide are used. The suspension in the present invention contains one or both of iron hydroxide and iron oxide. Cations contained in the suspension of iron hydroxide or iron oxide include alkali metal ions such as sodium ions and potassium ions; alkaline earth metal ions such as magnesium ions and calcium ions; ammonium ions, etc. Examples of anions include halogen ions such as chloride ions, iodine ions, and oxalide ions; sulfate ions; nitrate ions;
Calculation of oxalate ion, acetate ion, etc.? Commonly used are chloride ions, etc.

The suspension containing iron hydroxide or iron oxide and cations and anions in the present invention is generally obtained by the following method. iron sulfate, iron chloride, iron nitrate, iron oxalate,
Alkaline solutions of ferrous and ferric salts such as iron acetate, e.g.
It can be obtained by hydrolysis by adding an aqueous solution of an alkali metal hydroxide or an alkaline earth metal hydroxide or an ammonia aqueous solution. Iron hydroxide produced by hydrolysis may be partially oxidized to become iron oxyhydroxide or iron oxide.

Further, the above suspension may contain various water-soluble metal salts used as raw materials for magnetic particles. For example, water-soluble metal salts such as sodium and potassium silicates, chromium salts, nickel salts, and magnesium salts may be included.

The total concentration of iron hydroxide and iron oxide in the suspension to be subjected to electrodialysis in the present invention is not particularly limited, but generally 1 to 30
(Hit/l is preferably in the range of 1 to 1009/l. Particularly preferred is 1 to 1009/l. Therefore, if the concentration of iron hydroxide or iron oxide exceeds the above range, dilute it to the above range. It is preferable to do so.

The ion exchange membrane electrodialysis tank and electrodialysis method of the present invention include:
Any known ion exchange membrane electrodialysis cell may be used without any particular restriction as long as it has a basic structure in which a cation exchange membrane and an anion exchange membrane are arranged between an anode and a cathode. For example, a three-chamber type with one cation exchange membrane and one anion exchange membrane installed between the anode and cathode, a cation exchange membrane and an anion exchange membrane alternately arranged between the electrodes via a chamber frame, and both These include the filter press type and unit cell type, which have a basic structure in which a demineralization chamber and a concentration chamber are formed by an ion exchange membrane and a chamber frame. The type and number of positive and anion exchange membranes used in such an ion exchange membrane electrodialysis tank, the flow path spacing (membrane spacing) of the demineralization chamber and the concentration chamber, etc. are determined based on the suspension of iron hydroxide or iron oxide to be treated. It is selected as appropriate depending on the type of liquid and processing amount.

In particular, the cation exchange membrane may be a conventional cation exchange membrane, but preferably a membrane having an anion exchange layer on at least one side of the cation exchange membrane is effective. for example,
1st. Second. Anion exchange groups such as tertiary amino groups and quaternary ammonium bases are chemically or physically adsorbed on one side of a cation exchange membrane, or chemically bonded. When such a cation exchange membrane is used, leakage of iron ions becomes extremely small, which is preferable. Furthermore, the interval between the channels in the demineralization chamber is generally preferably 10 mm or more, since it is necessary that the channels are not blocked by iron hydroxide or oxidative suspension. It is also preferable to provide a stirrer in the desalination chamber.

A method for removing cations and anions in a suspension containing iron hydroxide or iron oxide and cations and anions using an ion-exchange membrane electrodialysis tank includes A suspension or diluted suspension of iron hydroxide or iron oxide was supplied, an electrolyte solution was supplied to the concentration chamber, and an electrode solution consisting of an electrolyte solution such as saline was also supplied to the anode and anode chambers. This is carried out by passing a direct current between the anode and the cathode.

In the electrodialysis according to the present invention, the voltage applied to the electrodialysis tank, current density, temperature, liquid flow rate, and treatment time depend on the properties of the target iron hydroxide or iron oxide suspension and the concentration of the salt to be removed. Select as appropriate.

For example, the rate at which iron hydroxide or iron oxide suspension is fed to an ion exchange membrane electrodialysis tank is generally 0.01 to 20 cI.
rL/Sal! , preferably 0.1 to 5 crrL/s
ee, and the electrical density is generally 0.01 to 20 A/dm
2. Preferably, 0.1 to 5 A/dm is applied, and the temperature is preferably about 10 to 50°C.

Since the suspension of iron hydroxide or iron oxide that is the target of electrodialysis in the present invention is highly viscous and adhesive, it should be treated immediately after desalting by electrodialysis, for example, within one hour. It is preferable to drain the processing liquid from the desalting chamber first, and then perform backwashing with tap water to remove the suspension remaining in the container. By this operation, when performing electrodialysis again, it is possible to prevent clogging of the liquid flow path, clogging of the membrane, the rinser, etc., and to sufficiently suppress voltage increases, etc.

〔effect〕

As explained above, according to the method of the present invention, salts that adversely affect magnetization can be almost completely removed by a simple method of supplying a suspension of iron hydroxide or iron oxide to an ion exchange membrane electrodialysis tank. Since it can be removed, pure iron hydroxide or iron oxide suspension can be produced easily and inexpensively.

〔Example〕

Examples are shown below to specifically explain the present invention, but the present invention is not limited thereto.

Example-1 Ferrous sulfate aqueous solution K A NaOH aqueous solution was added, air was blown at pH 6, and a Fe0OHR suspension was produced at a temperature of 40°C. The suspension concentration is 1009/A
'Met.

50% of vaginal fluid with water! The solution was diluted to 1 liter and subjected to electrodialysis according to the method of the present invention to remove Na 2 SO 4 .

The electrodialysis tanks include Neosegta CMS (manufactured by Tokuyama Soda ■, a strong acidic cation exchange membrane with an anion exchange layer on the surface) and NeoSepta AM (manufactured by Tokuyama Soda ■, a strongly basic anion exchange membrane) and a desalination chamber. An electrodialysis tank TS-2 type (effective membrane area 2 dm2/pair, desalination chamber manufactured by Tokuyama Soda ■, channel spacing 10 m) was used, which was divided into a concentration chamber and a concentration chamber.

Electrodialysis conditions were a temperature of 40°C and an average current density of 1.5A/d.
It was operated at a membrane speed of 0.5 cm/See. The results are shown in Table-1. Immediately after the electrodialysis was completed, the treated solution in the desalting chamber was drained, and then backwashed with tap water to remove the suspension remaining in the cell.

Example-2 KO in ferrous sulfate aqueous solution containing 2 mot/l of Fe)
(Add aqueous solution, pH 7.5, temperature 40℃
A reaction for producing (0H)2 (concentration 2009/l) was carried out. Vaginal fluid was diluted with water to 50911 and subjected to electrodialysis according to the method of the present invention to remove K2SO4.

The electrodialysis tank and electrodialysis conditions were the same as in Example-1. The results are shown in Table IK.

Example-3 A NaOH aqueous solution was added to a ferric nitrate aqueous solution, and air was blown at 2.5 to perform a reaction to produce a Fe203 suspension (concentration 2o9/l) at a temperature of 70°C, and the stock solution was processed by the method of the present invention. Electrodialysis was performed to remove NaNos.

As the electrodialysis tank, the same one as in Example-1 was used,
Electrodialysis conditions are temperature: 40°C, average current density: 1.2A/dm
It was operated at a two-film surface speed of 1.0 or less. Table 1 shows the results.
Shown below.

Example-4 Adding N to a ferrous bromide aqueous solution containing 1 mot/l of Fe
An aOH aqueous solution was added, air was blown at pH 6, and a Fe0OH suspension was produced at a temperature of 50°C. The suspension concentration was 1209/l. The vaginal fluid was diluted with water to 409/l and subjected to electrodialysis to remove NaBr according to the method of the invention.

As the electrodialysis tank, the same one as in Example-1 was used,
Electrodialysis conditions are temperature 30℃ average current density 1.4A/dm
, membrane surface velocity of 0.6 cm,/see. The results are shown in Table-1.

Example 5 Using the same solution as in Example 1, an electrodialysis tank was prepared using a cation exchange membrane [Neosepta CM (strongly acidic cation exchange membrane manufactured by i-sansodamono) t]. It was treated under the same cell and electrodialysis conditions. The results are shown in Table-1.

Table-1 Comparative Example-1 The same suspension as in Example-1 was filtered using a filter press filter, the filtered solid cake was again dispersed and suspended in water, and the suspension was further filtered and dispersed. was repeated to remove Na2SO4. The results are shown in Table-2.

Claims (1)

[Claims] 1) A suspension containing iron hydroxide or iron oxide, cations and anions is supplied to an ion exchange membrane electrodialysis tank, and cations and anions are removed from the suspension by electrodialysis. A method for producing iron hydroxide or iron oxide, which comprises removing iron hydroxide or iron oxide.