JPH035324A - Production of iron oxide for rerrite material - Google Patents

Abstract

PURPOSE:To obtain an aqueous solution of refined ferrous chloride suitable for producing iron oxide for ferrite material by regulating the pH value of an aqueous solution of ferrous chloride to a value in a specific range by the use of iron or iron compound, partially forming a precipitate of goethite, and then separating the above precipitate. CONSTITUTION:In a method for producing iron oxide by applying high temp. roasting to an aqueous solution of ferrous chloride, the pH value of the aqueous solution of ferrous chloride is regulated to 2-5 by neutralizing free hydrochloric acid by the use of iron or iron compound and then the above aqueous solution is brought into contact with oxygen or oxygen-containing gas, by which 0.5-15% of iron (Fe) content in the solution is oxidized into a precipitate composed principally of hydrated ferric oxide (goethite, FeOOH). Subsequently, the above precipitate is separated and the aqueous solution of refined ferrous chloride is obtained, and this aqueous solution is subjected to high temp. roasting.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is a method of extracting St%A from the hydrochloric acid pickling waste of steel materials such as steel plates
The present invention relates to a method for producing iron oxide for ferrite raw material with a low content of impurities such as n%P.

<Conventional technology> Ferrous chloride aqueous solution generated as pickling waste of steel plates is
Usually Six A11s P% Cr, Cu.

It contains impurities such as Ti, and for example, when this waste liquid is roasted to produce iron oxide, these impurities remain in the iron oxide, so when the produced iron oxide is used as a ferrite raw material, This causes deterioration of its magnetic properties. In particular, when used in soft ferrite materials that require miniaturization and high performance, trace impurities such as Si%AfL and P can coarsen the crystals of ferrite particles, significantly impairing their electrical and magnetic properties. known to decrease.

Conventionally, in order to reduce the amount of impurities contained in the waste solution from pickling steel materials, a coagulation-filtration separation method has been used mainly for the purpose of de-sin, but the coagulation effect under strong acidic conditions is In addition, there was a problem that the removal rate of impurity components other than Si was low.

On the other hand, in order to enhance the coagulation effect, there are methods to increase the pH by neutralizing free hydrochloric acid in the ferrous chloride aqueous solution with an alkali, and methods to neutralize trivalent iron (Fe"") present in a small amount in the raw material solution with an alkali. A method has been proposed in which F e (OH) 3 is precipitated by adding F e (OH) 3 and impurities are removed by coprecipitation. but,
When an alkali is used, there is a problem that NH4, Na'', Ca''Mg'', etc. are mixed into the purified solution as impurities, and since these cannot be easily separated from the solution, they remain as impurities.

Therefore, as a method for removing impurities in a ferrous chloride aqueous solution by coprecipitation without alkali treatment, hydrated ferric oxide (β-FeOOH) is
A method of co-precipitation separation of impurities by producing
21731), and a method (Japanese Patent Publication No. 6O-8980) has been proposed in which the iron oxide precipitate produced is separated and removed by contacting with an oxygen-containing gas in the coexistence of an iron material for the purpose of removing Cr.

<Problems to be Solved by the Invention> However, the above-mentioned i-manufacturing method by coprecipitation has the following problems.

That is, according to Japanese Patent Publication No. 56-21731, the p)1 condition during the aeration reaction is a strongly acidic region around 1, and although a certain degree of impurity removal effect can be obtained, when using Si for wood purposes, , AJ2. It was found that the removal rate of P, Cr, etc. was not sufficient. Especially regarding P.
As will be described later, the solubility of metal orthophosphate (PO4) is high in a strongly acidic region, which causes it to be dissolved in the liquid and difficult to remove. In addition, the pH at which precipitation occurs
A similar tendency is observed for metal elements whose range is, for example, 3 or more.

On the other hand, Japanese Patent Publication No. 1989-8980 proposed that, for the purpose of removing Cr, by making iron material exist in the solution during aeration, the pH of the solution was
Although it is said that H is adjusted to 1.5 to 3.5, the iron material has a reducing effect, and under coexistence conditions, Fe is reduced by oxygen-containing gas.
The oxidation reaction of S
There is a problem in that it is not easy to obtain a sufficient amount of precipitate to remove i, Ai, and p by coprecipitation and adsorption. On the other hand, since it is an oxidizing atmosphere, there are restrictions on the pH increase due to the reducing action of the iron material, which is considered to be a factor in the insufficient removal of impurities such as St, An, and P. In addition, the F el C112 concentration in the solution is 25 to 4
0wt%, but each 1off problem mentioned above is 40w
It is particularly noticeable at concentrations of t% or higher.

The present invention solves the above-mentioned problems and efficiently and economically produces a purified ferrous chloride aqueous solution from which impurities such as Si and AILS P are removed from a steel plate hydrochloric acid pickling waste solution with a wide range of concentrations or its concentrate. The purpose is to provide manufacturing technology.

Means for Solving the Problems> As a result of extensive research into an inexpensive purification method for ferrous chloride aqueous solution in the manufacturing process of iron oxide for ferrite raw materials, the present inventors found that iron or iron compounds After adjusting the pH of the solution to 2 to 5 using It was discovered that impurities such as St%AfL%P can be effectively coprecipitated and adsorbed and removed by separation, and the present invention was completed.

That is, in order to achieve the above object, according to the present invention, in a method for producing iron oxide by roasting a ferrous chloride aqueous solution at a high temperature, free hydrochloric acid is dissolved in the ferrous chloride aqueous solution with iron or an iron compound. After adjusting the pH to 2 to 5, the iron (Fe) content in the solution is reduced to 0.5 to 15 by contacting with oxygen or an oxygen-containing gas.
% to a precipitate whose main component is hydrated ferric oxide (FeOOH), and the precipitate is separated to form a purified ferrous chloride aqueous solution, followed by high-temperature roasting. A method for producing iron oxide is provided.

The present invention will be explained in more detail below.

First, the raw material to which the present invention is applied is an aqueous iron chloride solution such as waste hydrochloric acid pickling of steel plates or the like or concentrated waste hydrochloric acid obtained by heating and concentrating this.

These usually contain free hydrochloric acid and are often in a strongly acidic state with a pH of less than 1.

Therefore, free hydrochloric acid is neutralized using iron or an iron compound without using an alkali, and the pH is adjusted to 2 to 5; preferably 3 to 4. The iron or iron compounds used for neutralization can be mill scale, scrap, iron powder, or other iron sources generated in steel mills. In particular, if it is metallic iron, trivalent iron (trivalent iron, which is present in small amounts in the liquid) can be used. Fe ”) is reduced (273F e ”+ 173F e −* Fe
”), so it is advantageous in terms of increasing the pH. Also, in terms of reaction rate, it is desirable to have a shape with a large specific surface area.

The reason for adjusting the pH to the above range is that S i O2
A This is to lower the solubility of impurities such as JZ and P, and to coarsen the particles to facilitate coprecipitation and adsorption separation in the next step. In addition, it is technically difficult to raise the pH to 5 or higher when no alkali is used, and some of the divalent iron (F e '') in the solution starts to precipitate.
e It is undesirable because it becomes a mouthful.

The above reaction proceeds rapidly at temperatures above 60°C, preferably above 80°C, and although the ferrous chloride concentration of the treatment solution is arbitrary, it is economically advantageous to handle it at a high concentration (40 wt% or above). be.

The ferrous chloride aqueous solution thus prepared is separated from the aforementioned iron or iron compound and sent to the next step. On this occasion,
A filtration operation may be performed to completely separate suspended substances such as fine scales. The thus obtained aqueous ferrous chloride solution is brought into contact with oxygen or an oxygen-containing gas to convert 0.5 to 15% of the Fe content in the solution into hydrated iron oxide (FeOO).
By oxidizing to H) to form a precipitate and coagulating and filtering it,
Impurities such as St, AJZ, and P are separated by coprecipitation and adsorption.

The impurity removal mechanism at this time will be explained below. First, SL exists as 5i02 (silica),
In the strongly acidic region, it mainly exists as silicate ions, but at pH 2
When neutralized to 5 to 5, colloidal polymerization progresses and the particles become coarse as negatively charged colloidal silica.

On the other hand, AjZ dissolves as chloride in a strongly acidic region, but p
As H increases, hydroxide precipitates and deposits. In addition to AIL, this includes Cr and Cu.

Ti and the like also exhibit similar behavior.

Regarding Zarani P, in the strongly acidic region, phosphate ions (
It is dissociated from metals as a soluble first salt ((Me"H2PO4) Me is a metal). On the other hand, when the pH is raised to a range of 2 to 5, metals A second salt (Me"HPO4) and a third salt (Me"Pop) are formed, and the third salt is particularly poorly soluble and precipitates out.Moreover, the main form of the precipitated phosphate From the solubility data of FePO4 (see Figure 2), the minimum solubility of FePO4 is p
It is in H3, 5-4.

As mentioned above, by adjusting the pH, Si, An,
Impurities such as P can be made insolubilized, making coprecipitation and adsorption separation easier.

On the other hand, the main component of the precipitate produced by wet oxidation is hydrated iron oxide, and as a result of X-ray diffraction analysis, β-FeOOH
It turns out to be , which has the following properties:

In other words, it is porous in structure and has a large surface area, is positively charged in liquid, lowers the zeta potential of negatively charged substances such as colloidal silica, neutralizes the charges, and coagulates, and is easily agglomerated by anionic polymer flocculants. It also has excellent sedimentation separation properties and filtration properties. All of these are very desirable properties for a carrier that undergoes coprecipitation and adsorption treatment.

Based on the above points, the present inventors have found that they can improve efficiency by combining the insolubilization effect through pH adjustment and the coprecipitation/adsorption effect using hydrous iron oxide (FeOOH) as a carrier, and by allowing both reactions to occur independently. It was discovered that impurities such as SL, AJZ, and P in an aqueous ferrous chloride solution can be removed at a surprisingly high removal rate over a wide range of concentrations, leading to the completion of the present invention.

In addition, to explain the implementation conditions of the wet oxidation in more detail, the proportion of Fe oxidized to hydrated iron oxide is as follows:
．． It may be 5-15%, preferably 1-5%. 0.5
If it is less than 15%, the sufficient effect of the present invention cannot be obtained, and if it exceeds 15%, the refining effect will not be proportional and Fe loss will increase, which is uneconomical.

In addition, the temperature condition is 50 to 100°C, preferably 70 to 9°C.
The reaction proceeds rapidly at 0°C. Although the pH drops to 2 or less at the end of the oxidation reaction, the impurities co-precipitated and adsorbed during the first half of the reaction are not easily separated or re-eluted, and do not cause a decrease in removal rate. Of course, the carrier, hydrated iron oxide, will not be redissolved in this pH range.

In addition, in order to promote flocculation of the precipitate, it is recommended to add an anionic polymer flocculant, the amount of which is 5 to 50 m
g/It, preferably 10-30 mg/It
IL is good. The precipitate after coagulation is discharged out of the system as a filter cake by means such as ordinary sedimentation separation or filtration separation. On the other hand, the finally obtained purified ferrous chloride solution is converted into ferric oxide (Fe2 os
) and can be used as a raw material for high-quality soft ferrite.

An example of a specific implementation flow of the present invention will be explained below based on FIG. 1. Dissolve raw material ferrous chloride aqueous solution (pH
Adjustment) Introduce into apparatus 1, add Fe or Fe compound (scrap pieces as an example), neutralize free hydrochloric acid, and p
After setting H2 to H5, only the solution is transferred to the oxidizer 3 via the buffer tank 2.

Next, in the oxidizer 3, oxygen or an oxygen-containing gas (for example, air) is dispersed in the liquid, and a precipitate of hydrated iron oxide is generated through gas-liquid contact. Hydrous iron oxide that has co-precipitated and adsorbed impurities such as Si, Al, P, etc. is coagulated with an anionic polymer flocculant, concentrated with thickener 4, dehydrated and separated with filter breath 5, and discharged from the system as a cake. .
On the other hand, the clarified liquid from the thickener 4 is passed through the clarification filter 6.
to obtain a purified ferrous chloride aqueous solution. This purified liquid is further roasted in a blow-out roasting furnace 7 if necessary, so that highly pure ferric oxide can be produced.

<Example> The present invention will be specifically explained below based on Examples.

(Example 1.2) A batch-type melting tank filled with scrap (cold-rolled steel plate scrap pieces generated in a steelworks) at least 5 times the theoretical consumption amount, using the steel plate hydrochloric acid pickling waste liquid as shown in Table 1 as a raw material. The mixture was stirred for 2.5 hours at a temperature of 90° C. to neutralize all free hydrochloric acid in the raw materials, reduce Fe'+ to the total amount of Fe'', and adjust the pH to 3 to 3.5.

Next, after taking out the liquid and separating it from the scrap material, air was dispersed into the liquid at a flow rate of 1117 min for 1.5 to 2 hours while maintaining the liquid temperature at 70 to 80°C in an oxidation tank.
By oxidizing 3.0 to 3.5% of Fe in the solution, β
A precipitate of -FeOOH was deposited.

Further, 10 mg/j2 of an anionic polymer flocculant was added, and after stirring for 10 minutes, the mixture was left to stand and separated by sedimentation, and the cake was separated by dehydration. On the other hand, the supernatant liquid was filtered through a 1μ filter, and purified F e Cm2 liquid was recovered as a clear liquid.

The operating conditions of Example 1.2 are shown in Table 1, and the purified FeC obtained
Product iron oxide (Fez o3) from the component analysis value of JZ2 liquid
Table 2 shows the content of impurity components in terms of base.

(Comparative Examples 1 to 4) Using the same raw materials as in the previous example, operations were performed under the following conditions.

Comparative Example 1 □ Raw material liquid was directly agglomerated.

Comparative Example 2 □ The raw material liquid was scrap-dissolved to increase the pH, and then coagulated and filtered without oxidative coprecipitation.

Comparative Example 3 □ Raw material liquid was subjected to oxidation coprecipitation at a low pH level without scrap dissolution, followed by coagulation filtration (method of 1982-21731).

Comparative Example 4 □ Raw material liquid was subjected to oxidation coprecipitation and coagulation filtration at the same time in the presence of scrap (method of Japanese Patent Publication No. 60-8980).

Other operating conditions are the same as in the example. The respective implementation conditions are shown in Table 1, and the obtained FeCj2. Table 2 shows the components of the liquid (converted values based on Fe03).

As is clear from Table 1.2, it is clear that impurities can be efficiently reduced by operating as in the present invention.

In the method of the comparative example, in particular, S iO2A j2 s P
However, the purification effect is poor and the oxidation reaction takes time (Comparative Example 4).

Raw material and purified FeCJlz liquid result of analysis

[Brief explanation of drawings]

FIG. 1 is a flow diagram showing an example of an apparatus used in the manufacturing method of the present invention. FIG. 2 is a diagram showing the solubility of FePO4. Explanation of symbols 1...Dissolving (pH adjustment) device, 2...Buffer tank, 3...Oxidizing device, 4...Thickener 5...Filter press, 6...Clarifying filter <Effects of the invention 〉 Since the present invention is configured as described above, it is possible to purify an aqueous ferrous chloride solution at low cost, and by performing a high-temperature roasting treatment, it is possible to produce highly pure iron oxide useful as a raw material for high-grade ferrite. It has the effect that it can be obtained.

Claims (1)

[Claims] (1) In a method for producing iron oxide by roasting a ferrous chloride aqueous solution at a high temperature, after neutralizing free hydrochloric acid in the ferrous chloride aqueous solution with iron or an iron compound and adjusting the pH to 2 to 5, 0.5 to 15 of iron (Fe) in solution by contacting with oxygen or oxygen-containing gas
% to a precipitate whose main component is hydrated ferric oxide (FeOOH), and the precipitate is separated to form a purified ferrous chloride aqueous solution, followed by high-temperature roasting. Method for producing iron oxide.