JPH036389A - Method for removing impurity from acidic solution containing ferrous ion - Google Patents

Abstract

PURPOSE:To produce high-purity alpha-Fe2O3 powder by adjusting the pH of a waste steel pickling soln. in a neutralization tank, transferring the soln. to a reaction tank, adding a specified metal and aq. alkali to adjust the pH and to crystallize the impurities other than Fe in the soln., flocculating and separating the separated impurities with a flocculant, bringing the supernatant liq. into contact with a chelate resin to purify the liq. and roasting the liq. CONSTITUTION:Steel material is descaled with aq. hydrochloric acid, and the waste pickling soln. 16 contg. >=5wt.% ferrous ion is charged into the neutralization tank 2 packed with steel cuttings 1 and circulated by a pump 14. Steam 15 is injected to heat the soln. to >=80 deg.C, the pH is controlled to 0.5-4, and the soln. is transferred to the reaction tank 4. An acidic soln. 17 of one or two kinds of metals among Al, Cr, V, B and Zn is added while agitating the soln. by an impeller 3, aq. alkali 18 is further added to adjust the pH of the soln. to 3.5-6, the hydroxide of the added metal is crystallized, then a flocculant 19 is added to flocculate the crystals, and the flocs are settled and separated. The supernatant liq. is passed through a chelate tower 6 to remove the residual impurities such as Ni and then introduced into a roaster 8 (hydrochloric acid recovery device) via a a liq. storage tank 7 and roasted to produce high-purity alpha-Fe2O3 powder.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is aimed at recovering high-purity iron oxide from acid solutions containing iron ions or iron salts. Relating to a method for removing impurities.

An example of an iron-containing acid solution to which the present invention is applied is a waste liquid obtained when a steel material is pickled with hydrochloric acid.

[Conventional technology]

In recent years, pickling using hydrochloric acid has become mainstream in the cleaning process for removing scale from steel materials. This steel material pickling waste liquid is roasted at high temperature, and the hydrochloric acid recovered is reused as a pickling liquid. Powdered iron oxide (α-Fe203) produced as a by-product at this time is mainly used as a raw material for ferrite or a pigment.

By the way, as shown in Table 1 below, for example, the steel material pickling waste liquid contains impurities other than iron, particularly impurities such as silicon and N1. For this reason, these impurities are mixed into the by-product iron oxide, and for example, the content of 5102 is 0.
045 to 0.06%, and the Ni content is o, oog to 0.06%.
It becomes 025%.

On the other hand, in order to improve the performance of ferrite magnetic materials, it is necessary to improve the properties such as the purity and particle size of iron oxide used as a raw material. It is important to use iron oxide powder. For example, silicone content is 09% or less as SiO2,
The Ni content is required to be 0.015% or less, and in recent years, it is strongly desired that both of these components be 0.005 to 0.007% or less.

The conventional method for removing silicic acid and recovering iron oxide from steel pickling waste is to add alkaline solution to iron sulfate solution to crystallize iron hydroxide, which is then oxidized and heated to produce high-purity iron oxide. The mainstream method was to obtain iron oxide. In this method, high purity is achieved by repeating or combining iron salt crystallization operations. However, this method often
Recovery of acid is not possible. In addition, it has the disadvantage that the process is complicated and the manufacturing cost is high due to the crystallization operation of the iron salt, oxidation heating, etc.

Therefore, in recent years, an inexpensive method has been proposed in which iron oxide is produced at the same time as the hydrochloric acid is recovered by roasting the waste solution from steel pickling using hydrochloric acid. In this method, prior to roasting, silicic substances in the waste liquid are removed mainly as 5i02. For example, special public service in Showa 59
No. 73439 discloses a method for obtaining low-SiO2 iron oxide by ultrafiltering a waste solution from hydrochloric acid pickling of steel materials and subjecting the pickling waste solution from which silicon impurities have been removed to roasting or crystallization treatment. ing. However, there is a limit to the size of particles that can be removed by ultrafiltration, so
It is difficult to stably obtain α-Fe203 of 0.01% or less. Furthermore, since the ultrafiltration process has low efficiency in principle, it is not possible to remove the entire amount of SiO2.

In addition, in Japanese Patent Publication No. 151335/1983, a cationic polymer flocculant was added to the hydrochloric acid pickling waste solution to make it siliceous (Si0
A method is disclosed in which 2) is aggregated and separated by ultrafiltration. Since this method also uses ultrafiltration, it has the same disadvantage of low efficiency as the above-mentioned method.

Furthermore, in JP-A-51-14898, an alkaline solution is added to the pickling waste liquid to perform a neutralization reaction, and silicon is produced together with the produced ferrous hydroxide or ferric hydroxide alone, or a mixture of the two. A method of co-precipitating a substance and then separating it by filtration is disclosed. However, this method has poor silicon co-precipitation efficiency, so it is necessary to generate 8 to 10% iron hydroxide.
It has drawbacks such as large loss of iron components.

On the other hand, regarding the removal of Ni ions contained in a concentrated iron salt aqueous solution, glyoximes such as dimethylglyoxime are added to the etching solution using ferric chloride to remove the nickel contained in the etching solution. A method for removing nickel glyoxime by precipitating it is known (Japanese Patent Application Laid-Open No. 190367/1983).

Also known is a method of removing nickel as nickel hydroxide or metal nickel by adding iron powder (Japanese Unexamined Patent Publication No. 82-191428). However, since both of these methods involve solid-liquid separation of nickel ions as inert nickel hydroxide or metallic nickel, it is extremely difficult to separate them from iron, which is contained in large amounts in the solution.

Furthermore, it is necessary to control the amount of dimethylglyoxime or iron powder added depending on the nickel ions in the waste liquid, so it is extremely difficult to stably remove nickel ions to a low concentration.

Furthermore, in Japanese Patent Publication No. 5g-50138, nickel or It is disclosed that copper can be selectively recovered. However, it is theoretically impossible to remove siliconity using this method.

[Problem to be solved by the invention]

As mentioned above, the conventional techniques cannot efficiently remove the silica in the steel material pickling waste solution. Furthermore, an efficient and economical method that can sufficiently remove impurities mainly composed of silicon and Ni components through a series of operations has not yet been established.

In view of the above circumstances, an object of the present invention is to remove SiO□ and Ni from an acid solution containing ferrous ions, such as steel pickling waste, through a series of operations to reduce the content to 3 to 4 ppm or less. It can reduce Cr and AΩ at the same time.

It is an object of the present invention to provide a method that can also remove or prevent the increase of other impurities such as P and Ti, and can treat the entire amount with high efficiency.

[Means to solve the problem]

The method of removing impurities from an acid solution containing ferrous ions according to the present invention includes (a) adding metallic iron to an acid solution containing 5% by weight or more of ferrous ions to adjust the pH to 0.5 to 4; (b) A, Q, and Cr are added to the obtained pH-adjusted solution.

a step of adding an acid solution of one or more metals selected from the group consisting of V, B, and Zn and uniformly dissolving the metal; (e) the pH of the solution obtained above is 3.5 to 3.5; (d) one or two selected from anionic flocculants and nonionic flocculants; A step of adding the above flocculant to flocculate the crystallized hydroxide and separating it by sedimentation; The invention is characterized by comprising a step of bringing the chelate resin into contact with the chelate resin.

In the above method, the pH-adjusted solution in step (a) is brought into contact with the same chelating resin as in step (e), and then the solution selected from the group consisting of AΩ, Cr, V, B and Zn in step (b) is A step of adding one or more of these may be performed.

The present invention will be explained in detail below.

In step (a) of the present invention, metallic iron is added to the steel material pickling waste solution, and the metallic iron is dissolved by increasing the temperature to 70°C or higher, preferably 75 to 80°C while performing liquid circulation or mechanical stirring. . This reduces the pH value of the solution to 0.
It is adjusted to 5 or more, preferably 2.0 or more, and 4.0 or less. Pickling is usually carried out at 60 to 80 °C, and dissolution of metallic iron is an exothermic reaction according to the following reaction.
No special temperature raising operation is required. This pH adjustment is relatively easy and can be completed in about 2 hours.

Fe+2HCρ→F e CΩ2+H2↑ The metal iron used for the above pH adjustment is preferably a cut piece (cPL, chopper, etc.) generated during refining of steel material after pickling treatment.

However, various pieces of iron material can be used without being limited to this. The reason for using metallic iron for pH adjustment is
For example, if an alkaline agent such as caustic soda or caustic potash is used, the recovery rate of hydrochloric acid will decrease when the waste liquid is roasted at high temperature in a later step. Further, the use of ammonia causes environmental health problems.

In step (b) of the present invention, the pH obtained in step (a) is
Add an appropriate amount of one or more acid solutions of metals such as aluminum, chromium, vanadium, boron, and zinc to the adjustment solution (or the solution that has been brought into contact with the same chelate resin as in step (e)). and make a uniform solution.

Subsequently, in step (c), an alkali is added to neutralize to a pH suitable for each added element. According to this, the hydroxide of the additive element (for example, 8Ω(011)3
.

Cr(OH)3, etc.) is crystallized. This crystallization reaction is carried out using 5in2° (S i
04)''-0-1~5 Proceeds with impurity fine particles or oxide ions as nuclei, and simultaneously captures and polymerizes them.This neutralization reaction is carried out at pH 6 or below to prevent the formation of iron hydroxide. Preferably, the pH is -3.5 to 6.

Next, in step (d), one or more types of flocculants selected from anionic flocculants and nonionic flocculants are added. As a result, fine colloidal crystallized particles are aggregated and coarsened, and separated from the solution.

The final step (e) is a step of adsorbing and removing nickel ions. This treatment is performed on the supernatant obtained in step (d). In addition, as mentioned above, step (a)
It is optional to perform the same treatment on the pH-adjusted liquid obtained in . Removal of nickel ions is carried out by bringing the liquid to be treated into contact with a chelate resin having picolylamines as an exchange group. The chelate resin used in the present invention is an ion exchange resin having picolylamines such as bispicolylamine and N-(2-hydroxypropyl)picolylamine as an exchange group.

FIG. 1 shows how the adsorption constant K of the above chelate resin changes with pH value. The adsorption constant is given by the following equation.

K = [R-Men/[RHnl
Hnl: Concentration of chelate resin not adsorbing metal [Me]: Concentration of metal present in the solution without being adsorbed by the chelate resin.

As can be seen from FIG. 1, when the pH value is less than 0.5, the adsorption constant for nickel is small, and nickel ions cannot be removed to a low concentration. On the other hand, when the pH is 2
Above, nickel ions are well adsorbed. Therefore,
It is necessary to remove the Nila 4 Kel ion in step (e) by adjusting the pH value to 0.5 or more, preferably in the range of 2.0 to 6.0.

The following two methods can be used to bring the solution to be treated into contact with the chelate resin in step (e). The first method is to add a chelate resin to the waste liquid and stir it. The second method is to fill a column with chelate resin and pass the waste liquid through it. The latter method is preferable because it has better operability and can lower the nickel ion concentration in the treatment liquid.

A chelate resin whose adsorption capacity has decreased due to adsorption of nickel ions can be regenerated using hydrochloric acid and water in an amount of about IO% by weight. By restoring the nickel ion adsorption ability through this regeneration operation, the chelate resin can be reused.

〔Effect of the invention〕

As described above, according to the present invention, in the crystallization reaction of hydroxide in an acid solution, fine colloidal silica and silicate ion particles 5 (S io2. (S i04 ) suspended in the solution The silicon content, which is an impurity, can be removed by the growth of the crystallized product with -0-1 to 5) as the nucleus and the incorporation of these particles into the crystallized product by adsorption. Further, ions such as Ni and Cu can be adsorbed and removed by contact with the chelate resin.

Therefore, the SiO2 content and Ni content in the waste liquid should be reduced to 3 to 4 pp.
C, Aβ, and Ti at the same time.

Other impurities such as Cu can be removed or prevented from increasing. Moreover, these can be performed as a series of operations and with highly efficient total processing.

〔Example〕

Hereinafter, the present invention will be illustrated more specifically by Examples.

Example 1 FIG. 2 shows the apparatus used to carry out the method of the invention. In the figure, 2 is a neutralization tank with a capacity of 12 m3. The neutralization tank is filled with cut steel pieces through line 1. 4 is a reaction tank for carrying out a sedimentation separation reaction, and this reaction tank is provided with a stirring blade 3 having a diameter of 6 and a diameter of 1.0 m. 5 is diameter 3
It is a cylindrical chelate tower with a length of 50m+ns and a height of 1.5m.

The inside of the chelate tower 5 is filled with 100 g of a chelate resin 6 having picolylamine as an exchange group. 7 is a liquid storage tank, 8 is a roaster for recovering hydrochloric acid, and 9 is an indirect water cooling type cooler.

Piping as shown in the figure is provided between the above devices, and each line is provided with a pump for feeding liquid. That is, the pump 10 is used to send liquid from the neutralization tank 2 to the reaction tank 4.
Alternatively, the metering pump 11 is used to send the liquid from the reaction tank 4 to the chelate tower 5, and the pump 1 is used to send the liquid from the reaction tank 4 to the storage tank 7.
2, liquid is sent from the liquid storage tank 7 to the roaster 8 by pumps 13, respectively. Further, in the neutralization tank 2, liquid circulation is performed by a pump 14, and the temperature is increased by supplying steam from a line 15.

The present invention was carried out using the above-mentioned apparatus in the following manner.

First, 10 m 3 of steel material pickling waste liquid is filled into the neutralization tank 2 through the line 16, and the temperature is raised to 80° C. while the liquid is circulated by the pump 14. After the pickling waste liquid is adjusted to a predetermined pH value, the pump 10 is driven to send the entire amount of the pickling waste liquid in the neutralization tank 2 to the reaction tank 4.

In the reaction tank 4, a predetermined amount of the acid solution of the additive metal is added through the line 17 while stirring the pickling waste liquid. Also,
Alkaline solution is added through line 18 to achieve a predetermined pH.
adjusted to the value. In this process, impurities are captured simultaneously with the crystallization reaction of the added metal. The amount of the additive metal is determined depending on the target impurity removal rate.

Moreover, as conditions for efficiently carrying out the reaction, rapid stirring and temperature maintenance at 40 to 60°C are important.

When this crystallization reaction has sufficiently progressed, a flocculant is added through line 19 after reducing the stirring speed. The amount of the flocculant added is a predetermined amount proportional to the amount of the added metal and the amount of the liquid to be treated in order to sufficiently coarsen the crystallized material by aggregation. By stopping stirring and allowing the mixture to stand for 2 to 3 hours, the aggregates are sufficiently settled.

8. A predetermined amount of the supernatant liquid after the aggregates have been sufficiently settled as described above is passed through the chelate tower 5 by driving the metering pump 11. Exit 20 of chelate tower 5
Collect the treated liquid every 1 m3 and measure the nickel concentration.

The liquid treated as described above was stored in the liquid storage tank 7. Furthermore, the liquid was sent to roaster 8 and roasted to obtain iron oxide.

Examples of operational results obtained by implementing the method of the present invention in the manner described above are as follows:
They are summarized in Table 2.

Example 2 Using the same apparatus shown in FIG. 2 as used in Example 1, the present invention was carried out in the following manner.

The neutralization tank 2 was filled with 10 m3 of steel material pickling waste liquid through the line 16. The temperature was raised to 80° C. while circulating the liquid, and a predetermined pH value was obtained. Next, by driving the metering pump 11, a predetermined amount of the liquid to be treated was passed through the chelate tower 5, and then stored in the reaction tank 4. In the reaction tank 4, an acid solution of an additional metal was added through a line 17 while stirring the liquid to be treated. Further, by adding alkaline liquid through line 18, the pH was adjusted to a predetermined value.

After the crystallization of the added metal had sufficiently progressed, the stirring speed was slowed down and the flocculant was added through line 19.

After the crystallized material was sufficiently coarsened by aggregation, stirring was stopped and the mixture was allowed to stand still for 2 to 3 hours to allow the agglomerate to sufficiently settle. Thereafter, by driving the pump 12, the supernatant liquid of the reaction tank 4 was stored in the liquid storage tank 7. Furthermore, this treated liquid is transferred to the roaster 8 by the pump 13.
Iron oxide was formed by sending the powder to a boiler and roasting it.

Examples of operational results obtained by implementing the method of the present invention in the manner described above are as follows:
They are summarized in Table 3.

2

[Brief explanation of drawings]

FIG. 1 is a diagram showing how the adsorption constant K for metal ions of the chelate resin used in the present invention changes depending on pH. FIG. 2 is a diagram showing an example of an apparatus used to carry out the method of the present invention.

Claims (2)

[Claims] (1) A method for removing impurities from an acid solution containing ferrous ions, the method comprising: (a) adding metallic iron to an acid solution containing 5% by weight or more of ferrous ions to lower the pH to 0.5; (b) adding an acid solution of one or more metals selected from the group consisting of Al, Cr, V, B and Zn to the obtained pH-adjusted solution; (c) Adding an alkaline solution so that the pH of the solution obtained above is within the range of 3.5 to 6, the hydroxide of the metal element added is crystallized. (d) a step of adding one or more types of flocculant selected from an anionic flocculant and a nonionic flocculant to flocculate and separate the crystallized hydroxide by sedimentation; ) A method characterized by comprising the step of contacting a supernatant liquid after sedimentation and separation of aggregates with a chelate resin having a picolylamine as an exchange group. (2) A method for removing impurities from an acid solution containing ferrous ions, the method comprising: (a) adding metallic iron to an acid solution containing 5% by weight or more of ferrous ions to lower the pH to 0.5; (b) After bringing this pH-adjusted solution into contact with a chelate resin having picolylamines as an exchange group, Al, Cr, V, B, and Zn are added to the resulting solution. (c) adding an acid solution of one or more metals selected from the group consisting of and uniformly dissolving the metal; (c) adjusting the pH of the solution obtained above to within the range of 3.5 to 6; (d) adding one or more flocculants selected from anionic flocculants and nonionic flocculants; A method characterized by comprising the steps of: aggregating the crystallized hydroxide and separating it by sedimentation.