JPS585989B2 - Yukiyo Bio-Site FE - Google Patents

Description

[Detailed Description of the Invention] As a method for removing Fe ions from waste acid containing a large amount of heavy metal ions used in the process of metal smelting or pickling of metal products, NaCaNH salt is added to the waste acid. P of the overtopping wave
Conventionally, a method has been adopted in which H is adjusted and heavy metal ions are removed in the form of hydroxide, and Na25o, Ca5o4. (NH4
)2804 etc. were sold as by-products or discarded.

However, as pollution treatment advances in various fields, the above-mentioned by-products increase and become unmarketable.

Sales became difficult.

In addition, it has become extremely difficult to reject the project due to the high cost and prevention of secondary pollution.

In the case of HNO3 waste liquid, NO3 ions cannot be removed by neutralization, and this wastewater poses a problem as enriched wastewater, and regulations regarding N ions are required, especially in areas bordering the Seto Inland Sea or lakes.

In addition, the cost of chemicals used for pH adjustment has skyrocketed due to rising energy costs and changes in manufacturing methods, resulting in extremely high costs.

Further, the solution is concentrated in vacuum or concentrated by cooling to remove the gold layer ions contained in the salt form 1, for example, FeS.

Gold in waste acid is increased by crystals such as 7H20.
Although there is a method of lowering the on, it has the drawback that the by-product crystals cannot be treated economically, and furthermore, it requires a lot of energy for concentration, making it uneconomical.

Furthermore, as a solvent extraction method, There are 49,995 items.

According to this method, Fe3+ ions are extracted using ketones or ethers as an organic solvent.
For example, in the case of MIBK, it dissolves at about 20,000 PPM, so it is not economical, and when used in ether, it has the disadvantage that it is no longer suitable for industrial use.

Furthermore, the waste acid is directly led to an electrolytic chamber, and Fe is recovered as metallic iron by electrolysis, and ClS is recovered.

Methods using ion-selective membranes (cation or anion) or various types of microporous membranes as diaphragms have been announced as methods for recovering acid by moving ions, etc. to another chamber separated by a diaphragm, but none of them are effective. Also, the acidity is high because the waste acid is directly electrolyzed, and the metal ions decrease as the electrolysis progresses, reducing efficiency.

Liquid conditions suitable for electrolysis cannot be achieved, other electrolytes cannot be added, metal ions other than Fe can also be electrodeposited,
It has drawbacks such as not being able to obtain a highly pure electrolyte and lowering the added value (iv).

In addition, by passing through a diffusion dialysis membrane before electrolysis, a part of the free acid is moved to another chamber before electrolysis.

Alternatively, attempts have been made to overcome the above-mentioned drawbacks by moving the free acid to another chamber as much as possible by electrodialysis, but as the electrolysis progresses, the electrolyte decreases and the power source decreases, or the metal ions decrease too much. The drawback is that a large volume of liquid must be circulated in order to recover the acid to the extent that it does not.

However, Japanese Patent Application Laid-open No. 48-213 related to the inventor of the present application
59. Or in the patent application filed in 1983-31550,
Fe ions in the solution are extracted using organic solvent A containing alkyl phosphoric acid, etc., and HC is used to remove Fe ions from the organic phase.
It was not possible to increase the Fe ion concentration in the stripping solution.

For this purpose, by bringing into contact organic solvent B containing primary to quaternary amines or phosphoric acid esters, it is possible to obtain a concentrated Fe-containing chloride solution, and this solution is thermally decomposed to release Fe. There are ways to reduce the energy required to recover oxides and HCl.

What is the thermal decomposition method of chloride solution? In the case of small capacity, it is difficult to implement due to high equipment costs.

Furthermore, since the method involves spraying a chloride solution onto high-temperature areas, there is a drawback in that it is corrosive and stable operation cannot be continued for a long period of time.

The present invention has been made to overcome the drawbacks of these conventional methods.

The gist of this is that organic solvent 1, such as D2BHPA (D2-2-
A step of regenerating the acid by extracting Fe3+ ions in the solution into an organic phase by contacting an organic solvent containing Na25o3. NaH8o3. So
2. After facilitating stripping by reducing Fe3+ ions in the organic phase by contacting with an aqueous solution bubbling a hydrazine compound, Na2S, NaCl or a reducing substance (in gaseous form).

By contacting with mineral acids such as HCl, H2SO4.

The objective is to exfoliate Fe ions into the aqueous phase.

Next, details of the present invention will be explained with reference to the accompanying drawings.

FIG. 1 shows an example of the implementation method.

When the waste acid containing a large amount of Fe3+ ions is introduced into the Fe extraction step and brought into contact with an organic solvent containing alkyl phosphoric acid, the Fe3+ ions in the aqueous solution are extracted into the organic phase as shown in the following equation, and the acid is It will be collected.

Fe",,, +3R-H+: R3Fej3H+R-H is an organic solvent having an H-type exchange group.

The fact that Fe3+ ions can be extracted in a strong acid region is shown in Figure 4, which shows the relationship between the ratio of Fe3+ ions being extracted into the organic phase and the pH in one contact, although Fe2+ ions cannot be extracted.

This shows that Fe''+ ions can be extracted well.

FIG. 2 shows an equilibrium curve when Fe3+ ions are extracted using D2EHPA (di-2-ethylhexyl phosphoric acid) as an extractant.

Next, the Fe3+ ions extracted into the organic phase.

By contacting with a mineral acid having a higher H ion concentration than the extraction conditions, it is exfoliated from the organic phase to the aqueous phase as shown in the linear equation.

R3'Fe+3H(J';3R-H+FeC#315%
The peeling equilibrium curve due to HCl is shown by the line ○--○ in FIG.

As shown in the figure, in order to further increase the Fe ion concentration of the stripping solution, the mineral acid used for stripping must have an even higher H+ ion concentration, which results in loss of economic efficiency.

In the present invention, before stripping off Fe3+ ions in the organic phase, a reducing substance 1, for example, a hydrazine compound is added.

NaH8o3. Na25o3. By contacting with an aqueous solution containing NaNO2 or an aqueous solution bubbling a reducing gas such as So2 gas, the valence of Fe ions in the organic phase is changed.

Next, when brought into contact with a mineral acid such as HCI or H2So4, it can be easily stripped to the aqueous phase and the Fe ion concentration in the stripping solution can be increased.

The equilibrium curve shown by the X-X line in FIG.
%H (when in contact with J'.

It is understood that it is possible to make the Fe concentration extremely high compared to the ◯--0 line in the figure.

Also, as shown in the relationship between PH and extraction rate in Figure 4,
When Fe2+ ions become
As can be seen, it can be extracted with an aqueous solution with a low ion concentration (aqueous solution with a low ion concentration), and conversely, with an aqueous solution with a pH of 4 or less, it is possible to exfoliate from the organic phase to the aqueous phase.In order to exfoliate Fe ions in the organic phase, It can be seen that the method of the present invention is more economical than the conventional method since only a low concentration of mineral acid is required.

Next, the extractant used in the present invention is selected from the group shown below.

R represents an alkyl group, and in each group, an alkyl group having 4 to 18 carbon atoms is generally used.

One with 8 carbon atoms is D2EHPA (di-2-ethylhexyl phosphoric acid).

A typical example is 0PPA (octyl pyrophosphoric acid).

is also well known.

In addition, the petroleum hydrocarbon diluent used in the present invention is an aromatic hydrocarbon or an aliphatic hydrocarbon,
Of course, mixtures of these can also be used, and of course mixtures of miscellaneous petroleum hydrocarbons such as kerosene can also be used.

Furthermore, the concentration of the organic solvent used is determined by the concentration of the substance in the target waste acid and the amount of other acids coexisting.
Generally, it is adjusted to 2-75% (volume ratio).

Next, the reducing substances used in the present invention include hydrazine compounds such as N2H4, Na
25o3. Na25o3. It is typified by Na2S and the like, and their gaseous forms (SO2, etc.) are used.

When the present invention is implemented, there are the following advantages.

(1) It becomes possible to process iron sulfate, which has traditionally been considered economically difficult to process, and economically recover metallic iron, iron oxide, and sulfuric acid.

(2) C has been announced for some time.

Unlike the method of obtaining waste acid by directly electrolyzing it, it is possible to obtain highly pure metallic iron and iron oxide and recovered acid that does not contain any Fe ions, without generating secondary pollution such as C12 gas. .

(3) Not only large-capacity equipment but also equipment for treating small-volume waste acid is highly economical, so closed circuits can be formed at various pickling locations.

Next, an example of the present invention will be described, but the present invention is not limited thereto.

Example 1 Used for pickling stainless steel.

A waste acid containing a large amount of Fe ions and having the following analysis results was used in the practical test.

(Unit 9/13) Alkyl phosphoric acid 1 e.g. D2EHPA (
As shown by the first-order equation, Fe3+ ions are extracted into the organic phase by contacting with an organic solvent containing (above).

When Fe3+ ions, which are the majority of metal ions, are extracted, the acid will be regenerated and recovered.

FIG. 2 shows an equilibrium curve for extracting Fe3+ ions using an organic solvent obtained by diluting 50% D2EHPA (described above) with kerosene.

The Fe3+ ions extracted from the organic phase filter are treated with HCl or H
By contacting with 2So4, it is stripped from the organic phase and the organic solvent is regenerated, as shown by the linear equation.

It has been discovered that the Fe ions can be easily stripped by weakly reducing the Fe ions in the organic phase before stripping the Fe3+ ions.

This is evidenced by the fact that Fe2+ ions are not extracted unless the pH is high, as shown in FIG.

This effect can be obtained by bringing it into contact with a reducing solution before the stripping step.

Examples of reducing solutions include NaH803 and hydrazine compounds.

- By adding Na2So4 or bubbling So2 gas, etc., a weakly reduced solution can be made and used.

Next, add 50% D2EHPA (described above) to the organic phase diluted with kerosene at 23.94%. ! li! /1 Fe3+ ions were extracted and brought into contact with each reducing solution before stripping with 150 El/1 Hcl.

It is shown in Table (1).

Example 2 The analysis results of waste sulfuric acid used for pickling metal materials were used in practical tests.

To the above-mentioned waste acids (1) and (2), l, r, 40% HNO3 was added in a ratio of 0.11/1 for the purpose of oxidizing Fe2+ ions.
01 waste acid to convert Fe2+ ion to Fe3+
After conversion into ions, alkyl phosphates 1 such as D2BHP
Contact with an organic solvent containing A (described above).

Fe3+ ions were extracted and sulfuric acid was regenerated.

Continuous extraction test of Fe3+ ions.

The mixer-settler extractor used in the practical test has a width of 1
The mixer was a pump suction type mixer, and the number of revolutions was varied in the range of 180 to 310 rpm to control the phase separation and interface height.

The aqueous phase and organic phase were supplied in fixed amounts using metering pumps.

Equipment names (1) and (2) are both 10-stage mixer settlers.

tsu Notes - 50% D2EHPA.

Note: H2SO4 concentration in the inlet aqueous phase is 40%HNO3
changed due to the addition of

In the contact experiment with the cleaning liquid, the aqueous phase 1 was mixed with 1.5M NaCl+0
．． 1. It was contacted with MNa2So3 solution.

Do not touch water phase 2.

Note that the cleaning liquid is managed by pH and potential.

In the continuous test, 0/A=1.0/1.0.

Fe in the organic phase was removed by a five-stage mixer-settler extractor.
changed the valence of

Continuous Peeling Test The equipment used for the test is the same as the one used for the continuous extraction test, so it will be omitted.

The present invention, which has many of the features described above, makes it possible to provide an economical closed circuit at the waste acid discharge point, which can be easily installed alongside an existing pickling line, etc., regardless of the capacity.

As a method for recovering acids containing Fe ions using organic solvents.

It has extremely great industrial value.

[Brief explanation of drawings]

Figure 1 is a process diagram showing an example of the present invention, Figure 2 is an equilibrium curve for Fe3+ ion extraction using an organic solvent in which 50% D2EHPA is diluted with kerosene as an extractant, and Figure 3 is an equilibrium curve for Fe3+ ion extraction using 15% H (l). Peeling equilibrium curve diagram (〇-〇) when back extraction (peeling) is performed. Also, peeling equilibrium when back extraction (peeling) is performed using Na25O3 or NaCl as a reducing substance and 15% HC/. The curve diagram (X-X) is shown. Figure 4 shows the organic phase (30% D2EHPA, kerosene dilution,
It is a curve chart showing the relationship between PH and the extraction rate of Fe3+ ions (〇-9.-〇) and the relationship between PH and the extraction rate of Fe2+4 ions (X-X) in a sulfuric acid acidic solution.

Claims (1)

[Claims] Fe3+ ions are extracted and contained in an organic solvent in which 1-alkyl phosphoric acid is diluted with a petroleum-based hydrocarbon, and the organic solvent is brought into contact with an aqueous solution containing a reducing substance or a solution in which the reducing substance is bubbled. By using an organic solvent, the Fe ions can be easily stripped off, and then the Fe ions in the organic phase can be stripped off by contacting the organic solvent with a mineral acid. A method for recovering acids containing