JPS6221716A - Production of high-quality iron oxide powder for ferrite magnetic material - Google Patents

Abstract

PURPOSE:To obtain the titled iron oxide powder economically, from the zinc- leaching residue produced as a by-product of wet zinc refining, by leaching the residue with an acid in reducing atmosphere, removing Si, Al, As, etc., from the leachate, precipitating iron from the liquid by oxidation, and purifying the precipitate. CONSTITUTION:The zinc-leaching residue produced as a by-product of wet zinc refining process is leached with an acid in a reducing atmosphere, and the leachate is neutralized with CaCO3 or slaked lime to 4-5 pH, and Si, Al, etc., are precipitated and removed together with gypsum. The leachate is added with copper ion and zinc powder to effect the precipitation and removal of arsenic in the form of copper arsenide. The leachate is adjusted to an iron concentration of <=35g/l and made to react with oxidizing gas in an autoclave at >=200 deg.C to effect the oxidization of ferrous ion. The precipitated iron compound composed mainly of iron oxide is separated, the soluble components are removed with water, end the iron oxide is dried, calcined and pulverized. After removing the soluble components again with water, the residue is dried to obtain the titled iron oxide powder.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses zinc leaching residue, which is a byproduct of wet zinc smelting, as a starting material, leaches it with acid in a reducing atmosphere, and pre-neutralizes the resulting solution to produce ferrite magnetic material. The present invention relates to a method for producing high-grade iron oxide powder suitable for materials.

BACKGROUND ART Conventionally, processing methods called the goethite method, jarosite method, and hematite method have been employed as a method for recovering iron and other valuable metals from zinc leaching residue, which is a byproduct of wet zinc smelting, as a starting material. As the name suggests, these processing methods are used to separate iron and zinc contained in a solution obtained by acid leaching zinc leaching residue. The site method attempts to separate an iron compound mainly composed of jarosite, and the hematite method attempts to separate an iron compound mainly composed of hematite by precipitating them from the solution.

However, with either method, the impurity concentration in the leachate is high, so the iron compound obtained also has a high impurity quality (and has low value as an iron compound. Even trying to obtain iron oxide for ferrite magnetic materials from.

The purification method is difficult and there have been few examples of it being carried out industrially.

JP-A-56-164018, filed by the same applicant.

The present invention discloses a process for purifying a leachate in order to reduce the impurity level of iron compounds, thereby obtaining high-grade iron oxide for use in ferritic materials. The method proposed in this publication involves plating the leachate with a neutralizing agent such as calcium carbonate.
Aj in the liquid at about H4-5! , a first step in which impurities such as Si are separated by precipitation together with gypsum; and arsenic in the form of sulfide or copper arsenide by adding zinc powder in the presence of hydrogen sulfide or copper to the liquid of the first step from which the precipitate has been separated. The second step is to remove the precipitate, and the liquid from the second step after removing the precipitate is heated to a total pressure of 1
6~20kg/c+*”G, /FA degree 180~200
The third step is to oxidize the iron under pressure and high temperature at ℃ to oxidize and precipitate it.

A fourth step in which the iron oxide precipitate obtained in the third step is washed under pressure with hot water at 170 to 200°C to elute impurities such as Zn, Na, etc. in the iron oxide, and the iron oxide precipitate obtained in the fourth step is 7 iron oxides
It consists of a fifth step of desulfurizing roasting at 00 to 1000°C and pulverizing the obtained burned ore.

The present invention aims to further improve the method described in this publication, and more specifically, the method described in this publication does not require a high-temperature pressure washing step (fourth step) for removing Na deposits. The purpose is to obtain high-grade iron oxide powder while omitting the following.

The present invention provides a further improved formulation that achieves this objective.

Zinc leaching residue, which is a byproduct of wet zinc smelting, is leached with acid in a reducing atmosphere, and the resulting leachate is pre-neutralized, and further neutralized to pH 4-5 with calcium carbonate or slaked lime to remove silicon, aluminum, etc. in the solution. The first step is to precipitate it together with gypsum and separate it from the liquid.

The second step is to precipitate arsenic in the solution in the form of copper arsenide by adding copper ions and zinc powder to the solution from the first step after separating the precipitate, and to separate this precipitate from the liquid.

After separating the precipitate, the solution in the second step was mixed with an iron concentration of 35 g/
1 or less and react with an oxidizing gas at a temperature of 200°C or higher in an autoclave, and this reaction oxidizes ferrous ions in the solution and precipitates an iron compound whose main component is iron oxide (α-FezOz). The third step is to separate this precipitate from the liquid.

A fourth step of adding water to the iron compound-containing precipitate obtained in the third step to form a slurry to elute dissolved components, separating the eluate, and then drying and roasting.

The fifth step is to crush the iron oxide obtained in the fourth step, add water to form a slurry, elute the dissolved components, separate the two eluates, and then dry.

The present invention provides a method for producing high-grade iron oxide powder for ferrite magnetic materials.

The first and second steps in the method of the present invention are as follows.

There is no substantial difference from the method described in the above-mentioned Japanese Patent Application Laid-Open No. 56-164018. However, in the third step of the method of the present invention, the iron concentration is set to 35 g/l or less and the reaction temperature in the autoclave is set to 200° C. or higher.The method of the present invention does not include the fourth step of the method described in the publication. Instead, the iron compound-containing precipitate is washed with water and then roasted, and by this roasting, jarosite is added to the Na co-precipitated in the third step.
By changing to SO4, K 2s04 and pulverizing the 3 roasted product and washing it with water, Na and K in the iron oxide are further lowered, and at the same time, water-soluble Ca and Zn in the a-ferric oxide are leached out, and the result is 0 for 8 minutes. .1% or less.

FIG. 1 shows a flowchart of the manufacturing process of the present invention.

For reference, the flow of the manufacturing process described in the above-mentioned Japanese Patent Application Laid-Open No. 56-164018 is shown in FIG.

The present invention will be explained in detail below.

[First step]

The leachate obtained by leaching the zinc leaching residue under a reducing gas atmosphere (So gas) usually contains 65 to 85 g/l of zinc.
, ferrous iron; 35-40 g/l, free sulfuric acid; 20-40 g/l
30g/l, and various other impurities are also contained.

The main purpose of pre-neutralization is to remove free sulfuric acid from the liquid.
Neutralize until H1-2 to obtain 1 gypsum. In the first step of the present invention, this pre-neutralized liquid is neutralized using calcium carbonate or slaked lime, and Al and Si contained in the liquid are precipitated together with gypsum. The reaction temperature is 60~
80℃.

pH 4-5. Preferably, the A content in one solution is set to 4.5 to 5, and one reaction time is set to about 2 hours, followed by sedimentation separation.
I is 90% or more 1 Si is removed by 50% or more, Al concentration i in the sono solution;! , 30mg/j! Below, 5il1
The degree is 20 mg/ρ or less. The residual rate of iron and zinc in the liquid is 95% or more.

[Second process]

In the second step, the solution obtained in the first step is dearsenized. This arsenization treatment follows the method described in Japanese Patent Laid-Open No. 5474272 filed by the same applicant. Reaction temperature 50-70t, p
While adjusting to H4-5, add 0.0% copper sulfate as copper ion.
After adding 3 to 0.5 g/1, add 1.0 to 2.0 g/f of zinc powder, and add 2 to 3 g/f while stirring Wl.
By reacting for a period of time and separating the generated precipitate by filtration, more than 95% of the arsenic in the liquid can be removed, and the arsenic concentration in the liquid becomes leg71 or less. At the same time, metals with a lower ionization tendency than zinc are removed at the same time. Note that, depending on the case, dearsenization using hydrogen sulfide may also be used in combination.

[Third step]

The third step is a step in which the liquid obtained in the second step is supplied to an autoclave, and ferrous iron in the liquid is oxidized with oxygen gas to obtain iron oxide. In the method of JP-A-56-164018,
Na and K contained in the liquid precipitate together with iron in this process, forming NaFe1(SOa)i(OH)* and KFes.
(SOa)z(OH)a jarosite was produced, which entered the iron oxide and lowered its quality. The present inventors conducted various tests and studies to solve this problem, and found that the iron concentration in the liquid should be 35 g/1 or less, preferably 30 g/1.
It has been found that coprecipitation of Na can be prevented by reducing the Na content to 1 or less and reacting it with an oxidizing gas at a temperature of 200° C. or higher in an autoclave. In a test example, a solution with an iron concentration of 32 g/12 was fed into an autoclave, and the temperature was maintained at 210°C with steam while stirring, and the ferrous iron was oxidized at an oxygen partial pressure of 3 kg/cm. Iron oxide α-Fe103 is NazO,K,0
The quality was 200 ppm or less in all cases. Also, S
ing and arsenic are also less than 1 oopPIl.

A 1 gos varies depending on the Al concentration in the original solution.

It was 200 ppm or less.

[Fourth step]

The fourth step is a step in which the iron oxide obtained in the third step is washed with water, dried, and roasted. The iron oxide obtained by filtration and dehydration in the third step has about 20% attached moisture, and Zn in the liquid
, free sulfuric acid, and various other metal ions are attached. Furthermore, because the reaction was carried out at high temperatures, the solubility of gypsum in the liquid decreased and co-precipitated with iron trioxide. The purpose of washing with water is to remove these components by dissolving them in water. This is done by adding, for example, 10 times its wet weight of water to iron oxide to form a slurry, and stirring the slurry for 30 to 60 minutes.

Filter and dehydrate. This results in Zn and free sulfuric acid.

Plaster, etc. will move into the liquid. The filtered cake has a water content of approximately 20%
%, and the analysis value after drying is, for example, FezO391-9
5%, ZnO, 3~0.5%, Ca
0 100-500ppm.

It is about 81-3%. Roasting is carried out in the air. One of the purposes of roasting is to desulfurize the S in the iron oxide, and at the same time decompose the jarosite that is slightly contained, and convert it into soluble N.
The purpose is to convert to azSO□, K, soo. This reaction is.

2 M Fes (SOa)! (OH) h →3
FezO, + M2SO4+3SJ + 68zO(M
=Na or K) 8 As a result of thermal analysis experiments conducted by the present inventors, it was revealed that such jarosite decomposes at a temperature of 650 to 750°C. The second purpose of roasting is to roast the iron oxide particles grown in the autoclave, which are non-uniform and have various shapes, so that the particles can grow further. This makes it possible to obtain uniform fine particles in the next step (fifth step) of pulverization. From such a thing,
Roasting temperature is 700-900℃, preferably 750-85℃
It is preferable to carry out the process at a temperature in the range of 0°C; below this temperature, desulfurization and decomposition will be insufficient, and above this range, the particles will grow too much and it will be difficult to grind them into uniform fine particles. - In the example, using a manful furnace, 80% of S content is
The result was roasted in air at 0°C for 3 hours.

Its S grade decreased to 0.25%.

[Fifth step]

The fifth step is to crush the roasted product, wash it with water, dry it, and crush it. In this pulverization, the iron oxide particles grown by roasting are finely pulverized to the particle size required for ferrite magnetic materials, and the NazSO□ produced by roasting is
, to make it easier for SO to be eluted during the next water wash. For example, by crushing the fired crystal aggregate with an atomizer and pulverizing it with a two-vibration ball mill for 30 to 60 minutes, the grain size can be reduced to 1.2 μm or less. For washing with water, for example, the slurry is formed with water in an amount 10 times the dry weight of iron oxide, stirred for 30 to 60 minutes, and filtered. As a result, the Na accompanying the crushed iron oxide
, K.

Gypsum, Zn, etc. are eluted. The grade of the iron oxide powder obtained by drying this is 5. For example, Fe; 69% or more (this is Fe*0
3; 98.6% or more), Zn; 0.2-0
．． 4%.

NagO, to! O+ Cab, As, Sing, etc. are all below loopppm, 82□Os; 20
0 ppm or less + S: 0.1% or less, resulting in iron oxide powder with extremely low impurity quality.

The particle size is 1.2 μm or less, but if necessary, it is further crushed using an atomizer-1 vibrating ball mill, etc.

It can be made into finer particles by pulverization.

The method of the present invention will now be explained in more detail with reference to Examples.

(2) Removal of impurities by neutralization in the second step) The solution obtained by leaching the zinc leaching residue with an acidic solution in a reducing atmosphere is pre-neutralized with calcium carbonate, and 1 gypsum is separated to create a solution with the composition shown in Table 1. I got it. The pH of this solution was 2.0. This pre-neutralized solution was placed in a 5β beaker and stirred while maintaining the salinity for one reaction at 70° C., and neutralized to pH 4, 0, 4, 5 or 5.0 using calcium carbonate. After running the reaction for 2 hours.

This solid-liquid separation was performed, and the values of each component in the filtrate were analyzed.

The results are shown in Table 2.

As is clear from the results in Table 2, the removal rate of aluminum and silicon is not sufficient at pH 4.0, but p
At H4,5 and pH5,0, aluminum is 90%
As described above, silicon was efficiently removed with a removal rate of 60% or more.

Table 1 (Analysis values of pre-neutralized liquid) Table 2 (Analysis values of neutralized filtrate) A solution having the composition 3 was placed in a beaker 51, stirred while maintaining the reaction temperature at 60°C, and the pH was adjusted to 4.5 with sulfuric acid, and copper sulfate was added to the solution at a concentration of 0.3 g/l as copper ions. , zinc powder was added to give a total amount of 1.5gl. After the reaction was carried out for 2 hours, this liquid was separated by filtration, and each component in the filtrate was analyzed. The results are shown in Table 4. As shown in Table 4, arsenic was removed at a high removal rate of 1 mg/jl or less.

Table 3 (Analytical values of neutralized condensate) Table 4 (Analytical values of dearsenized condensate) ■ Third step (Generation of iron oxide) Add water to the dearsenized condensate to increase the iron concentration to approximately 30 g/1 A solution (pH = 4.5) whose composition is shown in Table 5 was placed in an autoclave having an internal volume of 3.5 liters, and the temperature was raised while stirring. The reaction temperature was 160℃ and 180t, respectively.
, maintained at 200℃, 220℃, 240℃, oxygen partial pressure 3
Oxygen gas was blown into the reaction mixture at a concentration of 1.5 kg/cm, and the reaction was allowed to proceed for 4 hours.Then, the exhaust valve was opened to discharge the product through the cooling coil, and the product was filtered to obtain iron oxide.Products at each reaction temperature The analytical values are shown in Table 6.

As is clear from the results in Table 6, when the 3 reaction temperature becomes high, especially above 200°C, Na, 0, and... 0 rapidly decreases to 200 ppm or less. Moreover, SiJ and As are also less than 100 pp-, and A j! ! Iron oxide containing 200 pp- or less of O was obtained.

Table 5 (Analytical values of iron oxide producing source liquid) Table 6 (Analytical values of produced iron oxide) ■Fourth step (Washing, drying and roasting of iron oxide) In the third step, the reaction temperature was 210°C, Oxygen partial pressure 3k
g/cm", the iron oxide whose composition is shown in Table 7 produced in a reaction time of 3 hours was made into a slurry with 10 times its wet weight of water and stirred for 60 minutes.

It was filtered off and dried. As seen in Table 8, the analytical values after washing with water and drying are shown in Table 8.

500g of this zero-order iron oxide from which Zn, free sulfuric acid, Mn, Mg, and Ca had been removed was placed in a magnetic crucible, and roasted for 3 hours at a roasting temperature of 700 to 900°C using a Matsufuru furnace. The analytical values of the obtained iron oxide are shown in Table 9.
As seen in Table 9, the S quality has decreased.

Table 7 (Analysis values of produced iron oxide) Table 8 (Analysis values of iron oxide after washing with water and drying) Table 9 (Analysis values of roasted iron oxide) ■ Fifth step (Crushing of roasted iron oxide and washing with water) In the fourth step, the iron oxide whose composition is shown in Table IO obtained by roasting at 800°C for 3 hours was placed in a stainless steel pot (volume 31), and a steel ball (12.7 cm - φ) was placed in a stainless steel pot (volume 31).
Add 0 kg and use a vibration mill for 15 minutes.

Milling was carried out for 30 minutes, 45 minutes and 60 minutes, respectively. Water was added in an amount 10 times the weight of the iron oxide to form a slurry, stirred for 60 minutes, filtered, and dried. The analytical values of the obtained iron oxide are shown in Table 11. As is clear from the results in Table 11, Z n, NazO, KzO.

CaO and S were further reduced, and high-grade iron oxide could be obtained.

゛Table 11 (Analysis values of roasted iron oxide after crushing and washing with water)

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing a process example of the manufacturing method of the present invention, and FIG. 2 is a flowchart showing a process example of a conventional manufacturing method.

Claims (2)

[Claims] (1) The zinc leaching residue, which is a byproduct of wet zinc smelting, is acid leached in a reducing atmosphere, and the obtained leachate is pre-neutralized,
The first step is to further neutralize the solution to pH 4-5 with calcium carbonate or slaked lime to precipitate silicon, aluminum, etc. in the solution along with gypsum and separate it from the solution. After separating the precipitate, copper ions are added to the solution in the first step. In the second step, the arsenic in the solution is precipitated in the form of copper arsenide by adding copper arsenide and zinc powder, and this precipitate is separated from the liquid.
1 or less and react with an oxidizing gas at a temperature of 200°C or higher in an autoclave, and this reaction oxidizes ferrous ions in the solution and precipitates an iron compound whose main component is iron oxide (α-Fe_2O_3). The third step is to separate the precipitate from the liquid, and the third step is to add water to the iron compound-containing precipitate obtained in the third step to form a slurry to elute the dissolved components, and after separating the eluate, dry and roast it. 4 steps, and a 5th step of pulverizing the iron oxide obtained in the fourth step, adding water to make a slurry to elute the dissolved components, separating the eluate and drying it. A method for producing high-grade iron oxide powder. (2) The solution after pre-neutralization in the first step is mainly composed of ferrous ions and zinc ions, and contains magnesium, calcium, sodium, potassium, arsenic, and silicon. A method for producing high-grade iron oxide powder for ferrite magnetic materials.