JPH0657347A - Method for recovering pd ion from waste liquid of pickling of stainless steel with palladium salt and nitric acid - Google Patents

Abstract

PURPOSE:To efficiently separate and recover Pd by specifying the concn. of the excess hydrochloric acid in a waste liquid of pickling with an acid mixture composed of Pd-contg. hydrochloric acid and nitric acid to the specific value or below, absorbing the Pd ion to a ion exchange resin layer and eluting the Pd ion with the hydrochloric acid of a specific concn. etc. CONSTITUTION:The waste liquid of the pickling with the acid mixture composed of the Pd-contg. hydrochloric acid and nitric acid used for descaling of stainless steels is filtered to remove impurities therefrom; thereafter, the liquid is concd. and is diluted with water, by that, the concn. of the excess hydrochloric acid in the waste liquid is adjusted to 1mol/kg or lower. The waste liquid is then passed through the ion exchange resin layer, to which the greater part of the Pd is adsorbed. This Pd is eluted with a 10 to 36wt.% hydrochloric acid solution or an ammonia water contg. 0.1 to 5N ammonia and is then washed with pure water. As a result, the Pd is effectively separated and recovered from the waste liquid of the pickling with the acid mixture composed of the Pd-contg. hydrochloric acid and nitric acid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a pickling waste solution of stainless steel pickled with a hydrochloric acid / nitric acid mixed pickling solution containing Pd (palladium) and a hydrochloric acid / nitric acid mixture obtained by wiping Pd carried on stainless steel. The present invention relates to a method for recovering Pd ions from a waste solution of a solution.

[0002]

2. Description of the Related Art Sulfuric acid has been conventionally used for scale removal of stainless steel materials, but this method of sulfuric acid pickling waste liquid treatment is a neutralization treatment method of neutralizing and removing metal salts as metal oxides. Alternatively, the method was one of a roasting method in which iron oxide and sulfuric acid as iron raw materials were recovered after being concentrated and added to a sulphide ore roasting furnace. On the other hand, for scale removal of ordinary steel, from about 20 years ago, sulfuric acid pickling was replaced with hydrochloric acid pickling, and the hydrochloric acid pickling waste liquid at that time was recovered by pyrolysis roasting and reused as pickling solution. On the other hand, the obtained iron oxide is effectively used as a raw material for ferrite.

A hydrochloric acid pickling method has been attempted for stainless steel materials because of the ease of recovering hydrochloric acid. However, in order to improve the pickling ability, a hydrochloric acid / nitric acid mixed solution containing (or dissolving) expensive Pd is used. Attempted to use. However, there is a problem that the pickling treatment with the palladium-containing hydrochloric acid / nitric acid mixture is not practical unless Pd is recovered from the waste liquid by the above-mentioned neutralization treatment method or roasting method.

[0004]

A typical composition of a hydrochloric acid / nitric acid mixed pickling waste solution containing Pd ions is as shown in Table 1. Here, NO ₃ ⁻ is reduced by Fe (II) in the waste liquid and is often small.

Table 1 Example of hydrochloric acid / nitric acid mixed pickling waste liquid ───────────────────────────────── Specific gravity 1.176 Fe (II) 2.04 wt% Fe (III) 2.42 Cr (III) 0.884 Ni (II) 0.102 Mn (II) 0.016 Pd (II) 0.0033 Total-Cl 24.4 nO ₃ ^- in the sense that ND ──────────────────────────────── Note) not detected with ND.

When separating impurities from such waste liquid, a metal hydroxide precipitation method by neutralization is often used. Examples of the neutralization treatment include a method using a metal such as metallic iron and a method using an alkali such as ammonia or sodium hydroxide. As shown in Table 1, Fe (II), Fe
When both (III) are contained in a large amount, it is difficult to recover a trace amount of Pd from this.

That is, Fe (II) hydroxide is precipitated at a pH of about 8 or higher, Fe (III) is precipitated at a pH of about 2 or higher, while Pd (II) is chloride ion (as described in this specification). Pd complex ions are also referred to as Pd ions) depending on the concentration, and are precipitated at a pH of about 2 to 8 or higher. Therefore, even if the amount of hydrochloric acid is controlled by evaporation or the like, Fe (II) or
It behaves in the same manner as Fe (III), and after separation of a large amount of hydroxide, further separation and recovery from Fe (II) or Fe (III) is required. Even if an oxidation or reduction treatment is used together before the neutralization treatment, most of the Fe ions are F due to the oxidation treatment.
When e (III) is used and neutralization filtration is performed, Ni, Mn, Cr, etc. still remain on the solution side together with Pd, and re-separation from these ions is required. Moreover, Fe is reduced by the reduction treatment.
When most of the ions are Fe (II) and the amount of free hydrochloric acid is small and only Pd is separated by filtration by the neutralization treatment, the standard redox potential of Fe ions Fe ³⁺ / Fe ²⁺
PdCl ₄ ^2- / Pd for 0.7 volt (1M HCl)
↓ 0.6 volt, Pd ²⁺ / Pd ↓ Since it is 0.99 volt, Pd ion is also reduced together with Fe (III) ion and Pd
d precipitates as metal Pd. Therefore, when a metal such as metallic iron is used as the reducing agent, Pd is deposited on the metal surface, and its recovery becomes a problem. When an organic reagent or the like is used as the reducing agent, a large amount of Fe (III) ions needs to be reduced, which is not economically advantageous.

Therefore, it is very difficult to recover Pd, which is a valuable resource, by the conventionally used neutralization method, and a method for effectively and economically recovering hydrochloric acid and Pd by a series of operations is still established. Not not. In view of the above circumstances, the present invention has an object of highly efficiently recovering Pd from a waste liquid in which a large amount of ferrous ions and ferric ions coexist, such as a stainless hydrochloric acid pickling waste liquid. Another object of the present invention is to provide a method for recovering hydrochloric acid from the waste liquid by using roasting together.

[0009]

According to the present invention, a hydrochloric acid / nitric acid mixed pickling waste solution containing Pd (palladium) is treated to reduce the excess hydrochloric acid concentration in the waste solution to 1 mol / kg or less, Most of Pd is adsorbed on the ion exchange resin through the exchange resin layer, and then Pd ions are eluted and recovered by ammonia water containing 10 to 36 wt% hydrochloric acid or 5N or less ammonia or ammonia-ammonium chloride solution. This is a method of recovering Pd ions.

According to the present invention, Pd is selectively recovered by the anion exchange resin by reducing the concentration of free hydrochloric acid, and the hydrochloric acid generated in the process of treating the waste solution of the pickling solution of the eluent is effectively reused. It is possible to recover Pd at a high concentration by using ammonia as an eluent without adding new chemicals to be used as an eluent. It is possible to obtain a waste liquid which can be decomposed into a metal oxide and hydrogen chloride gas by the method described above, for example, roasting, and the metal oxide and hydrochloric acid can be separated and recovered.

The present invention will be described in detail below with reference to the drawings. When eluting the Pd adsorbed on the ion exchange resin, the treatment is slightly different depending on whether the eluent used is a hydrochloric acid type or an ammonia type, and therefore the treatment will be described separately.

FIG. 1 shows a series of operations in which hydrochloric acid is used to elute Pd adsorbed on an ion exchange resin in the method of separating and recovering Pd contained in the stainless acid pickling waste liquid according to the present invention.

The waste liquid discharged from the pickling equipment contains some insoluble matter, but since Pd is hardly contained in the insoluble matter, it is removed by filtration ().

Among the ions in the pickling waste liquid, Fe (III) and Pd tend to form a chloroanion complex, and the anion complex produced is simply FeCl ₄ ^- and PdCl.
_m is represented by ^n-(m = 3 or 4, n = m-2) , the generation of these ions Cl ^- is influenced by ionic concentration. Fig. 2 shows FeCl ₂ 4.6 wt%, FeCl ₃ 7.0 wt%, CrC
l ₃ 2.7 wt%, NiCl ₂ 0.23 wt%, MnCl ₂
This is an example of the effect of removing Pd by the strongly basic anion exchange resin when the concentration of excess hydrochloric acid is changed with respect to a solution of 0.037 wt% and PdCl ₂ 0.0167 wt%. The smaller the amount of excess hydrochloric acid, the better the recovery of Pd. This is probably because when the amount of excess hydrochloric acid increases, the adsorption of the palladium chloro complex is hindered by the increase in Cl ⁻ anion concentration or the formation of FeCl ₄ ⁻ . Therefore, in FIG. 1, after the waste liquid is concentrated, steam stripping, diffusion dialysis, or the like to remove a part of the excess hydrochloric acid before the anion exchange treatment, and in some cases diluted with water to remove the excess hydrochloric acid amount. It is controlled to 1 mol / kg or less () and sent to the ion exchange process () (the numbers in ○ indicate the position on the process).

If nitrate radicals remain in the waste acid, it may cause deterioration of the ion exchange resin. In this case, concentration or steam stripping is preferable to diffusion dialysis. That is, the nitric acid in the waste acid is decomposed by the reaction with Fe (II) due to concentration or steam stripping, and is reduced to an almost negligible amount. The hydrochloric acid gas that has been distilled or diffused (or hydrochloric acid separated by diffusion dialysis) is recovered by the hydrochloric acid recovery device (). In the case of the concentration operation, the concentration of hydrochloric acid condensed and recovered is about 20 wt%, and in this case, it can be reused as it is as an eluent (regeneration liquid) from the ion exchange resin described later.

FIG. 3 shows a strongly basic anion exchange resin column.
And FeCl₂4.6 wt%, FeCl ₃7.0 wt%, C
rCl₃2.7 wt%, NiCl₂0.23 wt%, MnC
l₂0.037wt%, PdCl₂0.0875 wt%, excess
Leakage of Pd when continuously passing 1 mol / kg solution of surplus hydrochloric acid
It is an example of a curve. Pd is well adsorbed on the resin
I understand. Leakage in Figure 3 in the actual ion exchange tower
The elution (regeneration) operation is switched to before the point. Elution is 1
Adsorption using 0 wt% or more, preferably 20 wt% or more hydrochloric acid
It can be carried out countercurrently or cocurrently with respect to the flow direction. Figure
4 is an ion exchange resin color in which Pd is adsorbed in FIG.
When flowing 35 wt% or 20 wt% hydrochloric acid in cocurrent
It is an example of a Pd elution curve. 30-40L / L each
-R or P adsorbed by passing 80-100 L / L-R
It can be seen that most of d elutes. Elution (regeneration) operation
The column that has completed the process suppresses the elution of residual uneluted Pd.
If necessary, wash with water and switch to adsorption operation again.
Be done.

The hydrochloric acid used for elution may be hydrochloric acid recovered from the acid concentration adjusting step shown in FIG. 1 or hydrochloric acid newly supplied to the pickling equipment. Since Pd recovered in the eluent is a hydrochloric acid solution, it can be returned to the pickling facility as it is with almost no post-treatment. This method requires a larger amount of the eluent than in the case of a usual ion exchange resin treatment, such as desalting of water, and is a method that is difficult to be established in a process in which hydrochloric acid cannot be sufficiently utilized. However, the amount of hydrochloric acid that can be used is sufficient considering that both the hydrochloric acid and Pd recovered as in the treatment of the waste liquid from the pickling equipment using hydrochloric acid, which is the object of the present invention, are returned to the pickling equipment. Since it can be used as it is as a Pd-hydrochloric acid solution for pickling equipment, there is no loss of hydrochloric acid, and this is a characteristic advantage of the hydrochloric acid elution method.

FIG. 5 shows a series of operations in which ammonia water is used to elute the Pd adsorbed on the ion exchange resin in the method for separating and recovering Pd contained in the stainless pickling waste liquid according to the present invention. .

FIG. 5 is basically the same as FIG. 1, but there is a slight difference in the treatment because ammonia water is used for elution in the ion exchange step. From the ion exchange process to Pd
Differences from the hydrochloric acid elution method for recovery are described below.

Up to the Pd adsorption treatment, the same operation as in the hydrochloric acid elution method is performed. In the case of the ammonia elution method, since the eluent is alkaline, metals such as Fe (III) are hydrolyzed and precipitated as hydroxide precipitates, which may deteriorate the performance of the resin and cause clogging. Therefore, Pd attached or adsorbed to the resin
To remove most of the other metals, once water or 1 mol
After washing with a diluted hydrochloric acid solution of not more than / L, Pd is eluted. Pd can be eluted with ammonia water having an ammonia concentration of 0.1 to 5N, preferably about 0.5 to 1N. FIG. 6 is an example of an elution curve when this treatment is performed on a column that has been treated in the same manner as in FIG. The ammonia concentration used in this example is 1N. It has a very good elution property as compared with FIG. This is P due to ammonia
It is considered that this is because the chloro complex of d changed to an ammine complex and the charge of the complex changed from negative to positive, so that the complex was easily eluted from the anion exchange resin.

It can be easily analogized that the same effect can be obtained by using an ammonia-ammonium chloride solution.

Even if washing is performed before the ammonia elution treatment, a small amount of metal other than Pd remains in the eluent, and a slight amount of hydroxide precipitates may exist in the eluent. These may be removed by using a filtration process or the like in some cases.

Since the elution method using an ammonia-based eluent has a better elution property than the hydrochloric acid elution method, the concentration of Pd in the eluate recovery solution can be concentrated several times more than in the case of hydrochloric acid elution. Since ammonia has high volatility, it can be concentrated if necessary, and most of the ammonia can be evaporated and condensed, recovered, and reused as the eluent of the ion exchange resin. In this case, Pd in the concentrated solution is concentrated several hundred times or more as compared with the stock solution in the ion exchange step and the concentration step, and is recovered as a concentrated Pd solution. The advantage of the ammonia elution method is that a small amount of eluent can be used and a large degree of concentration can be achieved in the ion exchange process.

Fe (II) is the main metal in the waste liquid from which most of Pd and traces of ferric iron have been removed in the ion exchange process.
Fe (III), Cr (III), Ni (II), Mn (II), each dissolved in the form of chloride. This waste liquid is the same as an ordinary metal chloride-hydrochloric acid solution, and can be roasted if necessary to decompose the metal chloride into metal oxides and hydrogen chloride, and recover as metal oxides and hydrochloric acid.

When the recovered metal oxide is discarded, Cr may become a problem. In this case, most of them can be removed by performing the following processing. That is, Fe (II), Fe (III), Cr (III), Ni
The pH at which the metals of (II) and Mn (II) hydrolyze is about 8, 2, 5, 7, and 8, respectively. Therefore, before the waste liquid is roasted, Fe is added by metallic iron or another reducing agent. (III) → Fe
(II), pH 5-6 with metallic iron or ammonia
By neutralizing to a certain extent, Cr can be selectively separated as a hydroxide precipitate.

By the above operation, it becomes possible to efficiently recover Pd of valuables from the waste liquid of stainless hydrochloric acid / nitric acid pickling, and hydrochloric acid can be easily recovered by using roasting of the waste liquid together.

Whether to use the hydrochloric acid elution method or the ammonia elution method in the ion exchange step is determined depending on the use of the Pd solution to be recovered or the requirements of the equipment to be manufactured. Further, by appropriately inserting ammonia elution in the hydrochloric acid elution method, it is possible to regenerate the resin by eluting Pd accumulated in the ion exchange resin in a trace amount and accumulated for a long period of time.

The above method is applied to a waste solution of a catalyst in which Pd is carried on a stainless steel thin plate such as an exhaust gas catalyst, and the like.
It is also possible to recover precious metals such as.

[0029]

[Examples] Hereinafter, a method for recovering palladium from a waste solution of a stainless hydrochloric acid / nitric acid pickling solution will be described with reference to Examples.

Example 1 (when hydrochloric acid was used as an eluent) 100 L of hydrochloric acid / nitric acid mixed pickling waste liquid having the composition shown in the above Table 1 (1)
18 kg) was concentrated to prepare 45.4 kg of a solution having an excess hydrochloric acid concentration of 1.6 mol / kg. The amount of liquid distilled at this time was 72.0.
kg and hydrochloric acid concentration was 21.7 wt%.

40 kg of pure water was added to the concentrated solution obtained in order to adjust the concentration of excess hydrochloric acid to 1 mol / kg or less, and the concentration of excess hydrochloric acid was adjusted to 0.
It was set to 85 mol / kg. The Pd concentration in the obtained acid concentration adjusting solution was 45.4 mg / kg.

85.4 kg of this solution was mixed with a solution having the same composition as the acid concentration adjusting solution to stabilize the resin in advance.
Pd was adsorbed and separated by pouring onto a strongly basic anion exchange resin layer which was repeatedly adsorbed and eluted several times with a wt% hydrochloric acid aqueous solution. The palladium concentration in the metal chloride solution passed through the ion exchange resin layer was reduced to 1.8 mg / kg.

Next, in order to elute Pd, 35.2 kg of hydrochloric acid (21.7 wt%) generated and condensed during the above-mentioned concentration is caused to flow in a direction parallel to the time of adsorption on the ion-exchange resin layer, and the uneluted Pd is eluted. 1 l of pure water to stop the cleaning process
Then, 36.2 kg of a recovered liquid was obtained by combining with the above eluent.
The Pd and hydrochloric acid concentrations in the recovered liquid were as follows.

Pd: 101 mg / kg HCl: 21.1 wt% Recovery rate of palladium was 94.2%.

The hydrochloric acid used for elution is a part of the hydrochloric acid recovered by the concentration operation, and when the obtained palladium recovery liquid is returned to the pickling equipment, there is no loss of hydrochloric acid.

The metal chloride solution that has passed through the ion-exchange resin can be roasted as described above to recover hydrochloric acid and metal oxide.

Example 2 (When Ammonia Water is Used for Elution) The hydrochloric acid / nitric acid mixed pickling waste liquid 10 having the composition shown in Table 1 above, in which insoluble matters were removed by filtration.
0 L (118 kg) was concentrated to give an excess hydrochloric acid concentration of 1.6 mol /
45.2 kg of a kg solution was prepared. The amount of liquid distilled at this time was 72.2 kg, and the hydrochloric acid concentration was 21.6 wt%.

40 kg of pure water was added to the concentrated solution obtained in order to adjust the concentration of excess hydrochloric acid to 1 mol / kg or less, and the concentration of excess hydrochloric acid was adjusted to 0.
It was set to 85 mol / kg. The palladium concentration in the obtained acid concentration adjusting liquid was 45.5 mg / kg.

85.2 kg of this solution was adsorbed, washed, and eluted several times with a solution having the same composition as the acid concentration adjusting solution, pure water, and 1N ammonia water to stabilize the resin in advance.
It was poured into a strongly basic anion exchange resin layer which was repeatedly washed, and palladium was adsorbed and separated. The ion-exchange resin layer after the adsorption operation was washed with 1 L of pure water, and was combined with the metal chloride solution that passed through the ion-exchange resin layer. The palladium concentration in the mixed solution was 1.6 mg / kg.

Next, in order to elute Pd, 1N ammonia water was added in the direction of cocurrent with the time of adsorption to the ion-exchange resin layer in 3.2.
L was poured and washed with 1 L of pure water, and both were combined to obtain 4.3 kg of a recovered liquid. The Pd concentration in the recovered liquid was as follows.

The recovery rate of Pd: 863 mg / kg Pd was 95.7%.

Since ammonia in the obtained recovery liquid has a high volatility, most of it can be easily recovered by concentrating it depending on the case, and at the same time, the Pd concentration can be further increased.

[0043]

As described above, the Pd according to the present invention is
By adopting the recovery method of Pd, it is possible to recover Pd more effectively from the hydrochloric acid / nitric acid mixed pickling waste liquid, and it is also possible to recover hydrochloric acid by using roasting together. The achievement of the present invention makes it practically possible to use a hydrochloric acid / nitric acid mixed solution containing Pd ions, since hydrochloric acid and Pd can be circulated and used for scale removal of stainless steel materials.

Further, by applying the present invention to a waste solution of a catalyst such as an exhaust gas catalyst in which Pd or the like is carried on a stainless steel thin plate, it is possible to recover a noble metal such as Pd.

[Brief description of drawings]

FIG. 1 is a flowchart showing a palladium recovery process by a hydrochloric acid elution method according to the present invention.

FIG. 2 is a graph showing an example of the influence of excess hydrochloric acid concentration in the treatment with a strongly basic anion exchange resin.

FIG. 3 is a graph showing an example of a palladium leakage curve due to a strongly basic anion exchange resin.

FIG. 4 is a graph showing an example of a palladium elution curve with hydrochloric acid.

FIG. 5 is a flow chart showing a palladium recovery process by an ammonia elution method according to the present invention.

FIG. 6 is a graph showing an example of a palladium elution curve with 1N aqueous ammonia.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiyuki Imayasu 4-4-2, Funato, Itabashi-ku, Tokyo Inside Nittetsu Kakoki Co., Ltd.

Claims (1)

[Claims] 1. After treating a hydrochloric acid / nitric acid mixed pickling waste solution containing Pd (palladium) to reduce the concentration of excess hydrochloric acid in the waste solution to 1 mol / kg or less, most of it is passed through an ion exchange resin layer. After adsorbing Pd on the ion exchange resin, after that 1
Pd ion is eluted and recovered by ammonia water containing 0 to 36 wt% hydrochloric acid or 0.1 to 5N ammonia or ammonia-ammonium chloride solution.
A method of collecting d ions.