JPH0331654B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to the purification of an aqueous ferrous sulfate solution produced as a by-product from the sulfuric acid pickling process of steel sheets. [Prior Art] Iron oxide has been widely used as a main raw material for ferrite. The general manufacturing method for iron oxide is to convert ferrous sulfate crystals, which are produced as a by-product from the sulfuric acid pickling process of steel sheets, into
The so-called dry method involves roasting at 1100°C, the so-called wet method involves oxidizing the ferrous hydroxide suspension produced by the reaction of the by-produced ferrous sulfate aqueous solution with an alkali, and passing an oxygen-containing gas through the ferrous hydroxide suspension, or A widely used method is to further heat the hydrous ferric oxide or magnetite obtained by the wet method. However, when iron oxide produced using ferrous sulfate, which is a by-product from the above-mentioned steel plate sulfuric acid pickling process, is used as the main raw material for ferrite, especially soft ferrite, there are many problems in terms of quality characteristics. . That is, in the starting material ferrous sulfate aqueous solution,
It contains a large amount of SiO ₂ and metal impurities such as Al, Ca, and Na, and these impurities are contained in iron oxide during the manufacturing process. This fact can be seen, for example, in the 3rd to 5th lines of the right column on page 1 of Japanese Patent Publication No. 36-15360. It is clear from the statement that "impurities in iron usually get mixed into the product." Therefore, soft ferrite products, which are final products manufactured using iron oxide as the main raw material, contain
A large amount of SiO ₂ and metal impurities are contained, and these impurities cause deterioration of the characteristics of soft ferrite products. Among these impurities, the following will focus on SiO ₂ , which is said to have the most adverse effect on soft ferrite products. Iron oxide is SiO ₂ usually 0.04 to 0.10 for Fe ₂ O ₃
(hereinafter simply referred to as 0.04 to 0.10% by weight), and this iron oxide and Zn, Mn,
Soft ferrite powder obtained by a manufacturing method of mixing ferrite auxiliary raw materials such as Ni, Mg, and Cu compounds, heating, firing, and pulverizing (hereinafter simply referred to as the dry method) is further processed with SiO ₂ in the manufacturing process.
is mixed in, resulting in a product containing a large amount of SiO ₂ . SiO ₂ contained in soft ferrite powder is
It is known that it causes a decrease in characteristics such as magnetic permeability (μ) and electrical resistance. This fact is evidenced, for example, in Japanese Patent Publication No. 49-15360, which states, ``... impurities are accumulated in ferric oxide, and magnetic materials that require high performance and miniaturization, especially soft manganese-zinc-based or It cannot be used at all for composite ferrites such as those based on manganese and magnesium, and the main reason for this is that the crystals of the ferrite particles become coarse due to the action of a trace amount of silicic acid (SiO ₂ ) contained in ferric oxide. , and the (electrical) resistance value and μ·Q characteristics are reduced...” This is clear from the description. [Problems to be solved by the invention] In recent years, with the miniaturization and weight reduction of electrical equipment, the soft ferrite magnetic materials incorporated in these devices have also tended to become smaller. Increasing magnetic permeability (μ) and electrical resistance are increasingly required, and iron oxide is contained in iron oxide, the main raw material for soft ferrite.
There is a strong demand for the development of a method for purifying and removing SiO ₂ . In order to purify and remove SiO ₂ in iron oxide, the present inventor has developed
Various studies were conducted regarding the existence form of SiO ₂ and methods for purifying and removing SiO ₂ . The present inventor first studied the existence form of SiO ₂ in each process in order to find out whether the purpose could be easily achieved by performing a treatment to purify and remove SiO ₂ in any process in the production process of iron oxide. did. Traditionally, iron oxide has been subjected to various treatments to form SiO ₂
Attempts have been made to purify and remove it. The present inventor has discovered that in the case of iron oxide obtained by the above-mentioned dry method, SiO ₂ exists in the form of adhesion, and in the case of the iron oxide obtained by the above-mentioned wet method,
We considered that SiO ₂ is present and incorporated in the crystal structure of the iron oxide particles that are generated, and therefore it is extremely difficult to purify and remove SiO ₂ at the stage where iron oxide is generated. Then, the present inventor found that it is necessary to perform some kind of treatment in advance to purify and remove SiO ₂ before iron oxide is purified, that is, at the ferrous sulfate aqueous solution stage. . Furthermore, the present inventor has conducted repeated studies to purify and remove SiO ₂ contained in the ferrous sulfate aqueous solution, and has found that the SiO ₂ contained in the ferrous sulfate aqueous solution exists in the form of SiO ₂ colloidal particles. We focused on the fact that These SiO ₂ colloidal particles are extremely fine particles, and can be processed not only by ordinary filtration means such as a filter press, vacuum suction filtration machine, and precoat pressure filtration machine, but also by using a special filtration machine, an ultrafiltration machine. However, it was impossible to remove it. [Means for Solving the Problems] The present inventor has further studied the method of efficiently removing the fine SiO ₂ colloidal particles contained in the ferrous sulfate aqueous solution, and has developed a method for efficiently removing the fine SiO ₂ colloidal particles. It was thought that it would be better to form coarse aggregates with good filterability. Then, add PH to the ferrous sulfate aqueous solution.
Knowledge that when aluminum hydroxide colloid particles are added in steps 4 and 5, the aluminum hydroxide colloid particles can adsorb and aggregate SiO ₂ colloid particles on the particle surface to form coarse aggregates with good filterability. The present invention has been completed. That is, the present invention provides an aqueous solution of ferrous sulfate with a pH of 4 to
In Step 5, add aluminum hydroxide colloidal particles, or if necessary further add negatively charged cellulose to adsorb and aggregate SiO ₂ in the aqueous solution onto the surface of the aluminum hydroxide colloidal particles; Alternatively, there is a method for purifying an aqueous ferrous sulfate solution, which comprises adsorbing and aggregating SiO ₂ in the aqueous solution onto the cellulose surface via colloidal aluminum hydroxide particles, followed by filtration. [Function] First, the method for purifying a ferrous sulfate aqueous solution according to the present invention involves electrically adsorbing and aggregating negatively charged SiO ₂ colloidal particles onto the surface of positively charged aluminum hydroxide colloidal particles. By doing so, aggregates are formed and the aggregates are passed through. The coarse aggregates thus produced are
Separate separation can be carried out using conventional filtration means such as the above-mentioned filter press, vacuum suction filtration machine, and precoat pressure filtration machine. Ultrafiltration allows more efficient separation. When adding aluminum hydroxide colloidal particles to a ferrous sulfate aqueous solution, if negatively charged cellulose is present, the aggregates can be further coarsened, and the aggregates can be further coarsened. Since the state forms a network structure, the permeability can be improved and separation can be performed more efficiently. Aggregates in this phenomenon are created by adsorbing and aggregating negatively charged SiO ₂ through negatively charged aluminum hydroxide colloid particles on the surface of negatively charged cellulose. It is thought that it will become even coarser as time goes on. Moreover, since this aggregate forms a network structure in which the cellulose is intertwined with each other, it is thought that it has excellent transient properties. Next, various conditions for implementing the present invention will be described. The ferrous sulfate aqueous solution used in the present invention is a ferrous sulfate aqueous solution produced as a by-product from the sulfuric acid pickling process of steel sheets. The sources of ferrous sulfate aqueous solution are:
In addition, there is an aqueous ferrous sulfate solution discharged from the titanium white production process, and this aqueous ferrous sulfate solution can also be used as a starting material in the present invention. The pH of the ferrous sulfate aqueous solution in the present invention needs to be adjusted to 4 to 5 by adding aqueous ammonia. In this case, it is practically preferable to neutralize mainly with scrap iron or the like, and then adjust the pH to 4 to 5 with aqueous ammonia. If the pH is less than 4, the added aluminum hydroxide colloidal particles will dissolve, and if the pH exceeds 5, a large amount of iron in the ferrous sulfate aqueous solution will precipitate, so obtain a purified ferrous sulfate aqueous solution. Therefore, the object of the present invention cannot be achieved. As the aluminum hydroxide colloidal particles in the present invention, aluminum hydroxide colloidal particles produced by mixing an aqueous aluminum salt solution and an alkali can be used as they are, or those that have been further washed with water can be used. The amount of aluminum hydroxide colloidal particles added is 25 to 60% by weight based on SiO ₂ in terms of Al ₂ O ₃
It is. If it is less than 25% by weight, the effect of purifying and removing SiO ₂ is not sufficient. It is possible to carry out the present invention even when the amount exceeds 60% by weight, and even when aluminum hydroxide colloidal particles are present in excess of the SiO ₂ colloidal particles in the ferrous sulfate aqueous solution, they can be separated separately by filtration. However, it is meaningless and uneconomical to add more than necessary. For the filtration in the present invention, ordinary filtration means such as the above-mentioned filter press, vacuum suction filtration machine, and precoat pressure filtration machine may be used. Ultrafiltration allows efficient separation. As the negatively charged cellulose in the present invention, commercially available filtered cotton may be used as is. Moreover, shredded cotton thread can also be used. The amount of negatively charged cellulose added is 10 to 10% of the amount of negatively charged cellulose to the aluminum hydroxide colloidal particles.
20 times the weight. If it is less than 10 times the weight,
Further improvement in overefficiency cannot be expected. Although the present invention can be practiced even when the amount exceeds 20 times the weight, it is meaningless and uneconomical to add more than necessary. In the present invention, the addition order of cellulose and aluminum hydroxide colloidal particles may be either first or simultaneous. Cellulose is dispersed in an aqueous aluminum salt solution and then an alkali is added to hydrate the cellulose surface. Those to which aluminum colloidal particles are adsorbed can also be used. [Example] Next, the present invention will be explained with reference to Examples. In addition, the amount of Fe ²⁺ in the following examples is JIS K
1462 5.2.2. Potassium dichromate titration method:
The amount of SiO ₂ was measured by luminescence plasma analysis, and the amount of Al was measured by atomic absorption spectrometry. Example 1 Fe80.6g/, SiO ₂ 0.12g/(for Fe ₂ O ₃
It corresponds to 0.104% by weight. ), prepare a steel plate sulfuric acid pickling ferrous sulfate aqueous solution 1 containing Al0.014g/,
Aqueous ammonia was added to the aqueous solution to adjust the pH to 4.5.
Separately, aluminum sulfate (Al ₂ (SO ₄ ) ₃・17H ₂ O)
0.42g was dissolved in 0.1% water to make an aluminum sulfate aqueous solution containing 0.035g/Al, and 0.5ml of ammonia water was added to this to generate aluminum hydroxide colloidal particles at pH 9.5. was washed with water until the pH reached 7. Aluminum hydroxide colloid particles after washing with water
0.10g was added to the ferrous sulfate aqueous solution (SiO ₂
This corresponds to 54% by weight. ) and stirred for 5 minutes, and then separated using a filter press. Fe ²⁺ remaining in the filtrate is 77.1g/, SiO ₂ is
The content was 0.0041 g/(corresponding to 0.0037% by weight based on Fe ₂ O ₃ ) and 0.006 g/Al. Examples 2 to 7 Ferrous sulfate was prepared in the same manner as in Example 1, except that the type of ferrous sulfate aqueous solution, the amount of aluminum hydroxide colloid particles added, the type of cellulose, the amount added, and the filtration means were varied. The aqueous solution was purified. The main purification conditions and purification results are shown in Table 1. Comparative Example 1 An attempt was made to purify a ferrous sulfate aqueous solution in the same manner as in Example 5, except that aluminum hydroxide colloidal particles were not added. Fe ²⁺ remaining in the filtrate is 77.9
g/, SiO ₂ is 0.101 g/(0.0899 for Fe ₂ O ₃
Corresponds to % by weight. ) and Al was 0.013 g/, and impurities in the ferrous sulfate aqueous solution were hardly removed.

【table】

〔effect〕

According to the method of adding colloidal aluminum hydroxide particles in the present invention, colloidal particles of SiO ₂ can be adsorbed and aggregated on the surface of colloidal aluminum hydroxide particles to form coarse aggregates with good transient properties. SiO ₂ in an iron aqueous solution can be easily purified and removed. Furthermore, according to the method of adding aluminum hydroxide colloidal particles and cellulose according to the present invention, the aggregates can be further coarsened, and furthermore,
Since the aggregates form a network structure, the permeability can be improved and SiO ₂ in the ferrous sulfate aqueous solution can be purified and removed more efficiently.
That is, according to the present invention, as shown in the previous example, the SiO ₂ content in the ferrous sulfate aqueous solution can be purified and removed to 0.005% by weight or less, so the ferrous sulfate aqueous solution can be used as the starting material. The content of SiO ₂ in the iron oxide obtained as is very small. Therefore,
Even if SiO ₂ is unavoidably mixed in during the manufacturing process of soft ferrite powder using the dry method mentioned above, the SiO ₂ content in the final product can be suppressed overall, making it possible to produce soft ferrite products with extremely low SiO ₂ content. Obtainable. Furthermore, according to the method of the present invention, not only SiO ₂ in the ferrous sulfate aqueous solution but also metal impurities such as Al mentioned above can be purified and removed at the same time. In addition to the above-mentioned dry method, methods for producing soft ferrite magnetic materials include Zn, which is a ferrite auxiliary raw material,
There is a so-called wet method in which a spinel type oxide produced by adding an alkali to an aqueous ferrous sulfate solution containing an aqueous solution of Mn, Ni, Mg, and Cu salts and performing an oxidation reaction is heated and calcined. Naturally, even in the case of this wet method, it is possible to use an aqueous ferrous sulfate solution purified from metal impurities such as SiO ₂ and Al by the method of the present invention.

Claims (1)

[Claims] 1. Aluminum hydroxide colloidal particles are added to a ferrous sulfate aqueous solution at pH 4 to 5, and the aluminum hydroxide colloidal particles are coated on the surface of the aluminum hydroxide colloidal particles.
A method for purifying an aqueous ferrous sulfate solution, which comprises adsorbing and coagulating SiO ₂ and then filtering it. 2 Add aluminum hydroxide colloidal particles to a ferrous sulfate aqueous solution at pH 4 to 5 to coat the surface of the aluminum hydroxide colloidal particles with the particles in the aqueous solution.
A method for purifying an aqueous ferrous sulfate solution, which comprises adsorbing and coagulating SiO ₂ and then ultrafiltrating it. 3 Add colloidal aluminum hydroxide particles and negatively charged cellulose at a pH of 4 to 5 to a ferrous sulfate aqueous solution, and add the colloidal particles of aluminum hydroxide to the surface of the cellulose through the colloidal particles of aluminum hydroxide in the aqueous solution.
A method for purifying an aqueous ferrous sulfate solution, which comprises adsorbing and coagulating SiO ₂ and then filtering it.