KR920005574B1 - Process for the production of alpha-feooh - Google Patents

Abstract

The preparation of α-FeOOH for self-recording media comprises (A) refining waste hydrochloric acid, which is a byproduct from acidic pickling process at steel-making plant, to remove non- soluble materials and scales by membrane filter, (B) adding alkali solution to refined hydrochloric acid to adjust pH to 2.5-7 so that Fe+3 ion and other impurities are removed and refined ferrous chloride solution is produced, (C) adding alkali solution to above ferrous chloride solution under non-oxidizing atmosphere to adjust the pH of initial reactants to more than 13, and (D) oxidizing above solution with an oxidizing gas at 10-100 deg.C for more than 1 hr.

Description

Method for manufacturing magnetic recording medium (FeOOH)

1a to 1n degrees: Electron micrographs of iron hydroxides synthesized by oxidizing the reaction product from waste acid after the first and second purification steps according to the present invention at 45 ° C in the initial pH range of 4.5-13.65.

2a to 2c: Electron micrographs of iron hydroxides synthesized by oxidizing the reaction product from waste acid that passed only the first purification step at 45 ° C. at an initial pH of 13, 13.5 and 13.6.

3a to 3h: Electron micrographs of the iron hydroxides synthesized by oxidizing the reactants from the waste acid after the first and second purification steps according to the present invention at various pHs at an initial pH of 13.

-수산화철(

-FeOOH)분말을 제조하는 방법에 관한 것으로서, 보다 상세하게는 제철소에서 열연강판의 스케일(Scale)을 제거하기 위해 염산 산세 처리과정중 부생되는 폐산을 이용하여 알칼리 중화법으로 정제한 후 염화제일철 용액을 습식산화하여 자기 기록용매체로 시용되는

-Fe₂O₃계 산화철 및 철분말을 제조하기 위한 출발원료인

-FeOOH을 제조하는 방법에 관한 것이다.The present invention is a needle type suitable as a starting material for a magnetic recording medium

Iron hydroxide (

-FeOOH) powder, and more particularly, to remove the scale of the hot-rolled steel sheet in the steel mill, the ferric chloride solution after purification by alkaline neutralization method using waste acid generated by by-product during hydrochloric acid pickling process Wet oxidized and applied to magnetic recording media

-Fe ₂ O _{3 is} a starting material for manufacturing iron oxide and iron powder

It relates to a method of producing -FeOOH.

-Fe₂O₃계 산화철로서, 이는 오디오 및 비디오 테이프, 컴퓨터 테이프, 플로피 디스크(floppy disk), 카드(card)등 각종 정보 기록분야에 다양햐게 활용되고 있는 자성분말이다. 급속한 정보사회의 발달에 따라, 보다 좁은 면적에 보다 많은 정보량을 기억할 수 있는 매체가 절실히 요구되고 있다. 이에 부응하는 기록매체용 산화철계 자성재료로서는 8밀리 비디오용 테이프, 전자카메라 디스크, 접촉자기 전사용 모체 테이프, 디지탈 기록용 테이프 등에 활용도가 높은 철분말(metal powder)을 들 수가 있다. 이처럼 자기 기록분야에 있어서 산화철에 자성재료가 차지하는 비중이 큰 것은 우수한 물리적 화학적 특성을 겸비하고 있는데 반해 다른 기록매체에 비해 값이 싸기 때문이다.At present, the most popular type of magnetic recording medium

-Fe ₂ O ₃ -based iron oxide, which is a magnetic powder widely used in various information recording fields such as audio and video tapes, computer tapes, floppy disks, cards, and the like. With the rapid development of information society, there is an urgent need for a medium capable of storing more information in a smaller area. Corresponding iron oxide-based magnetic materials for recording media include high-availability iron powder such as 8-millimeter video tapes, electronic camera disks, contact magnetic transfer matrix tapes, and digital recording tapes. The reason why the magnetic material occupies a large portion of the iron oxide in the magnetic recording field is because it has excellent physical and chemical properties but is cheaper than other recording media.

-FeOOH를 제조하여야 한다.In addition to the basic magnetic properties such as high saturation magnetic flux density, large square ratio, and coercive force as large as the magnetic head allows, the characteristics required for the magnetic recording medium include the uniform dispersion, surface roughness, chemical and mechanical durability of the magnetic particles. Included. The properties of these magnetic recording media are largely dominated by intrinsic factors and extrinsic factors. Internal factors include saturation magnetization, residual magnetization, coercive force, angular boiling, and external factors include particle shape and size, overwhelming distribution, pore size and number, and dispersibility. Since external factors greatly influence internal factors, external factors must be well controlled to obtain a magnetic recording medium having good characteristics. Magnetic properties of acicular iron oxide-based magnetic materials are dependent on crystal magnetic anisotropy, magnetostrictive anisotropy, and shape magnetic anisotropy. Crystalline magnetic anisotropy and magnetostrictive anisotropy are material-specific integers that have a constant value regardless of particle shape, but shape magnetic anisotropy is determined by particle shape, which greatly affects magnetic properties. In order to obtain excellent magnetic properties, it has a good acicular property and a uniform particle size distribution.

-FeOOH should be manufactured.

-Fe₂O₃계 산화철 및 철분말의 입자형태는 출발물질인

-수산화철(

-FeOOH)의 입자 형태를 그대로 유지하며 결정학적 배향관계도

-수산화철침상축이

-Fe₂O₃및 철분말의 침상축과 일치하는 토포태틱(topotactic) 반응이므로

-수산화철 입자형태의 제어는 대단히 중요하다.

The particle shape of -Fe ₂ O ₃ -based iron oxide and iron powder is a starting material

Iron hydroxide (

-FeOOH) particle shape and crystallographic orientation

-Iron hydroxide needle shaft

Is a topotactic reaction consistent with the needle axis of Fe ₂ O ₃ and iron powder

Control of the iron hydroxide particle shape is very important.

-수산화철(

-FeOOH) 제조에 사용되었던 원료는 주로 황산철이었다. 황산철은 다량으로 손쉽게 입수가 가능하였으며 이를 원료로 하여 제조한 생성물의 품질이 우수하다는 점에 그 이유가 있었으나, 근간에 관련업계들이 제반사정으로 인하여 황산철보다 염화철이 원료입수가 유리하게 되었으며, 황산철을 원료로한 생성물의 특성과 동등이상의 품질의 나타내는

-수산화철을 염화철로부터 합성할 수 있다는 것이 확인되었다.(일본 특허 소 57-61635)Conventionally

Iron hydroxide (

The raw material used for the production of -FeOOH) was mainly iron sulfate. Iron sulfate was easily available in large quantities, and there was a reason that the quality of the product manufactured using this material was excellent. However, due to the general circumstances of related industries, iron chloride was more advantageous than iron sulfate. Indicative of quality equivalent to or higher than that of iron sulfate

It was confirmed that iron hydroxide can be synthesized from iron chloride. (Japanese Patent No. 57-61635)

-수산화철(

-FeOOH) 제조방법에는 일반적으로 산성영역법과 알칼리 영역법이 있다.("Condition for the Formation of Fe₃O₄by the Air Oxidation of Fe(OH)₂Suspension, " Bull Chem Soc Jpn., Vol 47(7), 1646-1650(1974) 산성 수용액에서 제조한

-수산화철은 수지상이 많이 생성하므로 최종생성물의 분산성과 자장배향성 및 자기 특성에 악영향을 미치게 되나 공업적으로는 유리한 방법이다. 한편 알칼리 수용액에서 제조한

-수산화철은 수지상이 거의 없고 침상성이 비교적 크기 때문에 고성능 테이프용 자성분 원료로 이용되고 있다.

Iron hydroxide (

-FeOOH) In general, there are acidic and alkalinized methods ("Condition for the Formation of Fe ₃ O ₄ by the Air Oxidation of Fe (OH) ₂ Suspension," Bull Chem Soc Jpn., Vol 47 ( 7), 1646-1650 (1974) prepared in acidic aqueous solution

-Iron hydroxide produces a lot of dendritic phase, which adversely affects dispersibility, magnetic field orientation, and magnetic properties of the final product, but is an industrially advantageous method. Meanwhile prepared in alkaline aqueous solution

Iron hydroxide is used as a magnetic raw material for high-performance tape because it has almost no dendritic phase and relatively high acicularity.

-FeOOH를 제조하고자 하였으며; 일본 특허(소 56-169131, 56-73631, 56-73632)에서는 입자크기가 작고 축비가 큰

-수산화철을 제조하기 위해, 황산철 용액에 알칼리를 가하고 입자 크기를 작게 하기 위한 목적으로 산화제(염소산칼륨, 염소산나트륨)를 첨가하거나 입도분포를 균일하게 하기 위하여 Zn, Si 등을 첨가하고 이를 장시간 방치한후, 후속 열처리시 입자간 소결방지 목적으로 규산나트륨을 첨가하여 산화반응시켜

-FeOOH를 제조하였다. 일본특허(소 58-25202)에서는 황산철 용액에 P를 첨가하여 입도분포가 균일하고 수지상이 적으며 합성 반응온도(50℃)가 높아도 마그네타이트(Fe₃O₄)의 생성이 없는

-FeOOH를 제조하였다. 또한 일본 특허(소 57-61635)에서는, 출발원료로 염화철을 이용하여 값싸고 고품질인

-수산화철을 제조하기 위하여, 염화철 용액에 임의로 유산 이온을 첨가하고 침상비나 크기를 조절하기 위한 첨가제(Zn, Ni, Co) 및 환원처리시의 소결방지제(Si)를 첨가하여

-수산화철을 제조하였다.In Japanese Patent (S56-73633), ferrous sulfate is used as ferrous iron solution, ferrous precipitate suspension produced at pH 11 or more is left for a long time, and then oxidized to 80 ° C or lower using an oxidizing agent to have good crystallinity and high axial ratio. Bed with small particle size

Attempted to produce -FeOOH; Japanese Patent (S 56-169131, 56-73631, 56-73632) has a small particle size and a large axial ratio.

To prepare iron hydroxide, add oxidizing agents (potassium chlorine, sodium chlorate) for the purpose of adding alkali to the iron sulfate solution and reduce the particle size, or add Zn, Si, etc. to make the particle size distribution and leave it for a long time. After the subsequent heat treatment, sodium silicate was added for oxidation prevention

-FeOOH was prepared. Japanese Patent No. 58-25202 discloses that the addition of P to the iron sulfate solution results in a uniform particle size distribution, low dendritic phase, and no formation of magnetite (Fe ₃ O ₄ ) even at high synthesis reaction temperatures (50 ° C).

-FeOOH was prepared. In addition, the Japanese patent (S 57-61635) uses iron chloride as a starting material, which is cheap and high quality.

To prepare iron hydroxide, optionally add lactic acid ions to the iron chloride solution, add additives (Zn, Ni, Co) for adjusting the bed ratio or size, and anti-sintering agent (Si) during the reduction treatment.

Iron hydroxide was prepared.

-FeOOH 제조를 위한 대부분의 공지 방법들은 출발원료로 황산철을 사용하고 있으며 각종 첨가제로

-수산화철의 입자특성향상 및 후속 열처리시 유발되는 소결 현상들을 억제하고자 하였다. 또한 염화철을 원료로 사용하는 방법에서도 여러 첨가제 및 소결방지제를 사용하였다.As mentioned above,

Most known methods for producing FeOOH use iron sulfate as a starting material and various additives.

-To improve the particle characteristics of iron hydroxide and to suppress the sintering phenomenon caused by the subsequent heat treatment. In addition, various additives and antisintering agents were used in the method using iron chloride as a raw material.

-수산화철의 제조에 관한 방법에 대해서는 전무한 상태에 있다. 이것은 폐산속에 용해되어 있는 불순물들의 제어가 곤란하여 불순물의 영향에 민감한 전자기제품, 그중에서도 기록매체로 사용되는 자성분의 자기적 성질을 열화시켜 자성분으로서의 구비조건을 갖추지 못하기 때문이다.It is obvious that iron chloride will become a major source of iron oxide magnetic recording media as the acid used in pickling lines in steel mills has been almost entirely converted from sulfuric acid to hydrochloric acid because of its pickling ability. At present, the development of magnetic fluid using hydrochloric acid pickling waste and the manufacture of pigment water iron oxide have been conducted.

There is no state on the method for producing iron hydroxide. This is because it is difficult to control the impurities dissolved in the waste acid and deteriorates the magnetic properties of the magnetic products sensitive to the influence of the impurities, among them, the magnetic material used as the recording medium, thereby failing to meet the requirements for the magnetic material.

-수산화철을 제조하는 방법을 제공하고자 하는 것이다. 본 발명은 특히 상기 정제 염화제일철 용액의 초기 반응을 pH 및 산화반응시간을 적절히 조절함으로서 여러가지 첨가제를 첨가함이 없이 우수한 입도 및 침상 결정성을 갖는

-수산화철의 제조방법을 제공하고자 하는 것이다.The present invention is suitable for magnetic recording from ferrous chloride solution which is purified from impurities in waste acid produced in by-product steel pickling line.

It is to provide a method for producing iron hydroxide. In particular, the present invention has excellent particle size and acicular crystallinity without adding various additives by appropriately adjusting the pH and oxidation reaction time of the initial reaction of the purified ferrous chloride solution.

It is to provide a method for producing iron hydroxide.

-수산화철을 제조하는 단계를 포함하여 구성된다.The production method of the present invention comprises the first purification step of purifying the hydrochloric acid waste liquid by-product from the iron pickling line by a filtration membrane; Adding a alkaline solution to the first purified hydrochloric acid waste solution to adjust the pH to a range of 2.5-7 and removing a Fe ^{+ 3} ion and other impurities in the hydrochloric acid waste solution to prepare a ferric chloride solution; Alkaline is added to the ferric chloride solution obtained by the first and second purification while alkali is added to adjust the pH of the initial reactant, and then oxidized using oxidizing gas to make a needle type suitable for magnetic recording media.

It comprises a step of preparing the iron hydroxide.

-수산화철 제조단계를 좀 더 상세히 설명하면 다음과 같다.The waste acid purification step

-The iron hydroxide manufacturing step is described in more detail as follows.

[Waste settlement]

The steel mill waste acid undergoes a first purification step through the filtration membrane, including high concentrations of iron chloride (ie, about 3.58 mol (M) of ferric chloride and about 0.16 M of ferric chloride (Fe ⁺³ / Fe ⁺² = 0.0446), including Mn, A solution containing other impurities such as Ca, Al, Mg, CR, Ti, K, Si is obtained.

In order to produce acicular iron hydroxide suitable for magnetic recording media, control of ferric chloride ions and other containing impurities is very important. In other words, when a ferrous salt solution containing a large amount of ferric ions is used as a raw material, granular magnetite is produced, so that shape magnetic anisotropy, which is a requirement for recording media, cannot be expected. Mn, Si and other impurities impair the magnetic properties of the recording medium, so controlling these components is very important.

In the purification of ferric chloride ions and other impurities, the present invention utilizes pH and solubility relationships. That is, a small amount of alkaline solution (preferably 4M NaOH solution) was added dropwise until the pH2.5-7 was gradually stirred in the first purified waste acid in a non-oxidizing atmosphere, and a red ferric chloride precipitate was formed, which was filtered. By this, a high concentration of ferrous chloride solution (Fe ⁺² : 1.63M, Fe ⁺³ : 0.01M, Fe ⁺³ / Fe ⁺² = 0.006, and other impurities: about ppm) can be obtained. have.

-수산화철(

-FeOOH)제조][

Iron hydroxide (

-FeOOH) Manufacture]

-수산화철 단일상(single phase)이 생성되는 반응물의 초기 pH는 약 13이상이며 최종 pH는 약 11.9-12.97범위이다.As described above, the high-concentration ferric chloride solution obtained by the first and second purification is placed in a reaction vessel and stirred under a non-oxidizing atmosphere (eg, nitrogen gas is blown at 5 L / min) and an alkaline solution (for example, 4M NaOH solution) was added in small portions to adjust the pH of the initial reactant to an appropriate level, and then the non-oxidizing atmosphere was replaced with an oxidizing atmosphere by air intake (3 L / min) and the like for 1 hour at a temperature of about 10-100 ° C. Oxidize. As the reaction progresses, the pH decreases, and the initial white precipitate containing ferrous chloride gradually changes to yellow through green green rust. After about 3 hours, there is little change of pH and dark yellow. Completely changed.

The initial pH of the reactants from which the iron hydroxide single phase is produced is at least about 13 and the final pH is in the range of about 11.9-12.97.

-FeOOH와

-FeOOH의 혼합물,

-FeOOH와 Fe₃O₄등의 혼합물과 기록재료에 부적합한 구형의 산화철이 생성된다. 또한 반응온도가 낮으면 너무 미세한 입자가 생성되어 후속 열처리시 입자간의 소결이 일어나 침상성을 소실하므로 자기 기록 재로로서는 부적합하게 된다. 반면에 반응온도가 너무 높게 되면 구상의 마그네타이트(Fe₃O₄)가 생성되므로 이들의 제어가 대단히 중요하다.What is important in the present invention is that the initial pH of the reaction solution, the reaction temperature and reaction time if the initial pH of the reactants is low

-With FeOOH

A mixture of -FeOOH,

A mixture of -FeOOH and Fe ₃ O ₄ and a spherical iron oxide which is not suitable for the recording material are produced. In addition, when the reaction temperature is low, too fine particles are generated and sintering between the particles occurs during the subsequent heat treatment, thus losing the acicular property, which is not suitable as a magnetic recording material. On the other hand, if the reaction temperature is too high, spherical magnetite (Fe ₃ O ₄ ) is produced, so their control is very important.

-수산화철 단일상이 생성되는 pH 영역에서는 pH의 증가에 따라 침상입자의 길이가 증가하는 경향과 더불어

-Fe₂O₃의 자기적 성질도 향상되었다. 반응온도가 증가함에 따라 침상비가 증가하며 40-60℃ 범위에서 생성된 시료로부터 제조된

-Fe₂O₃의 자기적 성질이 가장 우수하였다.

In the pH range where iron hydroxide single phase is produced, the length of needle-shaped particles increases with increasing pH.

The magnetic properties of -Fe ₂ O ₃ were also improved. As the reaction temperature increases, the needle ratio increases and is prepared from the sample produced in the range of 40-60 ° C.

The magnetic properties of -Fe ₂ O ₃ were the best.

Hereinafter, the present invention will be described in detail through examples.

Example 1

The waste acid produced in the iron pickling line was first purified using a filtration membrane, and other impurities, including Fe ⁺³ ions, among the first purified waste acid components were secondly purified by alkaline neutralization using pH and solution diagrams. Secondary purification was performed by slowly stirring the first purified waste acid and adding a small amount of 4M caustic soda (NaOH) solution until the pH was in the range of 2.4-7, producing a red ferric chloride precipitate, and filtering the ferric chloride precipitate into a needle bed. A light green ferric chloride solution suitable for the production of iron hydroxide was obtained.

Wet chemical analysis was performed on the first and second purified ferric chloride solutions as described above, and the results are shown in Table 1 below.

TABLE 1

300 ml of the light green 1.63M ferrous chloride solution prepared by the first and second purification as described above were collected and put into a stirrer, and 4M caustic soda solution was added while stirring at a stirring speed of 1500 rpm in a non-oxidizing atmosphere to adjust the initial pH of the reaction solution. It was changed in the range of 4.5 to 13.65 and oxidized for 4 hours at the reaction temperature of 45 DEG C while blowing an oxidizing atmosphere, that is, air at 3 L / min.

The precipitate produced under each condition was filtered and dried, and the product was qualitatively analyzed by X-ray diffraction analysis, and the needle ratio was obtained by electron microscope observation. The results are shown in Table 2 below. The electron micrographs of the samples are shown in FIG. It was.

-Fe₂O₃를 제조하고 VSM를 이용하여 측정한 자기적 특성도 표 2에 나타내었다. 또한 제이철 이온 및 기타 불순물의 함유량을 제어하지 않은 1차 정제 폐산을 이용, 침상의

-FeOOH 단일상이 생성되는 조건(즉, ph 13이상의 조건)에서 반응시켜 얻은 수산화철의 생성물을 X-선으로 정성 분석하여 표 2에 나타내었으며 전자 현미경사진을 제2도에 나타내었다. 또한 이들을

-Fe₂O₃로 전환해서 측정한 자기적 특성도 표 2에 나타내었다.On the other hand, as a result of electron microscope observation, a sample containing only needle-shaped particles was subjected to subsequent heat treatment (dehydration 550 ° C 1hr, reduction 325 30min, oxidation 250 ° C 30min).

The magnetic properties of -Fe ₂ O ₃ and measured using VSM are also shown in Table 2. In addition, by using primary purified waste acid that does not control the content of ferric ions and other impurities,

The product of iron hydroxide obtained by the reaction under the condition of producing -FeOOH single phase (that is, above pH 13) was qualitatively analyzed by X-ray and shown in Table 2, and the electron micrograph is shown in FIG. Also these

The magnetic properties measured by conversion to -Fe ₂ O ₃ are also shown in Table 2.

TABLE 2

-FeOOH를 비롯하여

-FeOOH와

-FeOOH의 혼합물, Fe₃O₄등이 생성되며 pH 13이상에서는

-FeOOH 단일상이 생성됨을 알 수 있다. 자기적 성질 또한

-FeOOH 단일상이 생성되는 pH 13이상의 시료가 우수한 특성을 나타내고 있다. 그러나 1차 정제단계만을 거쳐 제이철 이온의 량 및 기타 불순물의 함유량을 제어하지 않은 폐산을 사용한 경우는 표 2 및 제2도에 나타난 바와 같이 침상의

-FeOOH와 구상의 마그네타이트 혼합상이 생성되었으며 구상의 마구네타이트 생성으로 형상이방성의 기여효과가 감소되기 때문에 자기적 성질도 열악하였다.As can be seen in Table 2 and the accompanying 1-1 to 1-14 degrees, in the case of using waste acid in which ferric chloride ions and other impurities were controlled through the above-described first and second purification steps, The hydroxide could be obtained. That is, if the initial pH of the reactants is low,

-Including FeOOH

-With FeOOH

-FeOOH mixture, Fe ₃ O _4, etc. are formed, pH above 13

It can be seen that -FeOOH single phase is generated. Magnetic properties

Samples with a pH of 13 or above, where a -FeOOH single phase is produced, exhibit excellent properties. However, in the case of using waste acid which did not control the amount of ferric ions and other impurities through only the first purification step, as shown in Table 2 and FIG.

The mixture of -FeOOH and spherical magnetite was produced and its magnetic properties were poor because spherical magnetite production reduced the contribution of shape anisotropy.

Example 2

-Fe₂O₃를 제조하고 VSM을 이용하여 측정한 자기적 특성도 표 3에 함께 표기하였다.As in Example 1, 300 ml of the light green 1.63M ferrous chloride solution obtained by the 1st and 2nd purification were collected and put into a stirrer, and 4M caustic soda solution was added at a stirring speed of 1500rpm in a non-oxidizing atmosphere and the initial reaction of the reaction solution was carried out. The pH was maintained at 13, and the oxidation temperature, that is, air was blown at 3 l / min, the reaction temperature was changed to 10-70 ° C., and the reaction time was constant at 4 hours for oxidation reaction. The precipitate produced under each condition was filtered and dried to analyze the product by X-ray diffraction analysis, and the needle ratio was obtained by electron microscope observation. The results are shown in Table 3 below. The electron micrographs of the samples are shown in FIG. . Further heat treatment (dehydration 550 ℃ 1hr, reduction 325 ℃ 30min, oxidation 250 30min)

-Fe ₂ O ₃ was prepared and the magnetic properties measured using the VSM are also shown in Table 3.

TABLE 3

As shown in Table 3 and the accompanying 3-1 to 3-8 degrees, when the reaction temperature is high, spherical magnetite is produced, which causes a deterioration of magnetic properties. On the other hand, if the reaction temperature is low, it can be seen that the formation of extremely fine particles, the needle property is lost due to inter-sintering sintering during the subsequent heat treatment, the magnetic properties deteriorate.

Example 3

-Fe₂O₃를 제조하고 VSM을 이용하여 자기특성들을 측정하고 결과들을 하기표 4에 표기하였다.As in Example 1, 300 ml of the light green 1.63M ferrous chloride solution obtained by the first and second purification was collected and put into a stirrer, and 4M caustic soda solution was added thereto while stirring at a stirring speed of 1500 rpm in a non-oxidizing atmosphere. The initial pH of was maintained at 13.2, and the reaction temperature was changed to 10-90 ° C. while the oxidizing atmosphere, that is, air was blown at 3 L / min, and the reaction time was constant at 4 hours for oxidation reaction. The precipitates produced under each condition were filtered and dried to qualitatively analyze the product by X-ray diffraction analysis, and the needle ratio was obtained by electron microscopy. Subsequent heat treatment (dehydration 550 ° C 1hr, reduction 325 ° C 30min, oxidation 250 ° C 30min) )in

-Fe ₂ O ₃ was prepared, magnetic properties were measured using VSM, and the results are shown in Table 4 below.

TABLE 4

:

-FeOOH(Remarks)

:

-FeOOH

Example 4

As in Example 1, 300 ml of the light green 1.63M ferrous chloride solution obtained by the first and second purification were collected and put into a stirrer, and 4M caustic soda solution was added thereto while stirring at a stirring speed of 1500 rpm in a non-oxidizing atmosphere. The initial pH was maintained at 13.65 and the reaction temperature was changed to 10-90 ° C. while the oxidative atmosphere, that is, air was blown at 3 L / min, and the reaction time was constant at 4 hours for oxidation reaction.

-Fe₂O₃를 제조하고 VSM을 이용하여 자기특성을 측정한 결과를 표 5에 나타내었다.The precipitate produced under each condition was filtered and dried. The product was analyzed qualitatively by X-ray diffraction analysis, followed by subsequent heat treatment (dehydration 550 ° C. 1hr, reduction 325 ° C. 30min, oxidation 250 ° C. 30min).

-Fe ₂ O ₃ was prepared and the results of measuring the magnetic properties using the VSM is shown in Table 5.

TABLE 5

Example 5

As in Example 1, 300 ml of the light green 1.63M ferrous chloride solution obtained by the first and second purification were collected and put into a stirrer, and 4M caustic soda solution was added thereto while stirring at a stirring speed of 1500 rpm in a non-oxidizing atmosphere. The initial pH was maintained at 13.5, the reaction temperature was changed to 1-10 hours while the oxidizing atmosphere, that is, the air was blown at 3 L / min, and the reaction time was changed to 1-10 hours for oxidation.

-Fe₂O₃를 제조하고 VSM을 이용하여 자기특성을 측정하고 결과를 하기표 6에 표기하였다.The precipitate produced under each condition was filtered and dried to qualitatively analyze the product by X-ray diffraction analysis. The needle ratio was obtained by electron microscopy, followed by subsequent heat treatment (dehydration 550 ℃ 1hr, reduction 325 ℃ 30min, oxidation 250 ℃ 30min). )in

-Fe ₂ O ₃ was prepared, magnetic properties were measured using VSM, and the results are shown in Table 6 below.

TABLE 6

Claims (1)

Insoluble matters and scales in the hydrochloric acid wastewater produced in the pickling line at the steel mill are first purified by a filtration membrane, and an alkali solution is added to the primary purified hydrochloric acid waste solution to adjust the pH to a range of 2.5-7, thereby increasing the Fe ⁺³ ion. And removing other impurities to prepare a secondary purified ferrous chloride solution, and to the secondary purified solution by adding an alkaline solution in a non-oxidizing atmosphere to adjust the pH of the initial reactant to 13 or more, the temperature of 10-100 ℃ For magnetic recording media using an oxidizing gas for at least 1 hour

Iron hydroxide (

-FeOOH) manufacturing method.

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