JPH05271816A - Method for recovering metallic pt, pd and rh in waste pickling solution - Google Patents

Abstract

PURPOSE:To recover a catalytic metal from a pickling soln. obtained by incorporating a catalyst such as Pt ion, Pd ion and Rh ion into hydrochloric acid and selectively adding NO3<-> ion and which has been used for pickling a steel- base metal. CONSTITUTION:A steel-base metal is pickled by a pickling soln. obtained by incorporating Pt ion, Pd ion and Rh ion or further NO3<-> ion into hydrochloric acid, and Cr<6+> ion is added to the waste pickling soln. in the form of K2Cr2O7, CrO3, etc. When >=90% of Pd and Rh are recovered, Cr<6+> ion (g/l) >=22.5+3.75XT ( deg.C) should be kept, and Cr<6+> ion (g/l) >=52.5+3.75XT ( deg.C) should be kept when >=40% Pt, Pd and Rh are recovered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering precious metal ions added to a pickling solution as a pickling catalyst.

[0002]

2. Description of the Related Art During cold rolling of a steel sheet, pickling is carried out after mechanical descale treatment such as shot blasting is performed on oxide scale formed on the surface of a hot coil obtained by hot rolling. This pickling treatment not only completely removes scale but also has an important role of dissolving and removing surface flaws to form a smooth surface.

Conventionally, the pickling solution has been properly used depending on the type of steel depending on its scraping ability and the surface condition after pickling. For example, nitric hydrofluoric acid is used for austenitic stainless steel, but when this nitric hydrofluoric acid solution is used for pickling of ferritic stainless steel, it produces intergranular corrosion even though it has excellent fusing ability. After that, the surface condition was inferior, and hydrochloric acid or sulfuric acid having a good surface quality was used, although it was inferior in the abrading ability.

On the other hand, the applicant of the present application has previously mentioned that in Japanese Patent Application No. 3-109265, hydrochloric acid is used as a base, and nitrate ion is added to this, and Pt ion and Pd are used as catalysts.
A solution containing added ions, Rh ions, etc., is excellent as a pickling solution that can obtain a smooth cutting ability for any steel type without requiring proper use depending on the steel type and a smooth surface state after pickling. I disclosed that it is a thing.

Although this pickling solution has an extremely high pickling ability, the prices of Pt ion, Pd ion and Rh ion are very expensive, and the concentration in the solution is 500 mg / liter or less, which is a very small amount. However, the amount of pickling solution on an industrial scale becomes large, and it is necessary to recover from the processing waste solution and reuse it.

[0006]

The object of the present invention is to provide Pt.
An object of the present invention is to provide a method for efficiently recovering and reusing expensive metal from a waste liquid of a high-speed pickling solution to which ions, Pd ions, and Rh ions have been added.

[0007]

P in the pickling waste liquid of the present invention
The t, Pd, and Rh metal recovery methods are:
In the waste liquid of the solution in which the steel metal is pickled with the pickling solution which selectively contains d ions and Rh ions or further contains NO ₃ ⁻ ions, Cr ⁶⁺ ions of the following formula P
It is characterized in that an amount represented by g / liter obtained at a recovery target ratio of t, Pd and Rh ions and a waste liquid temperature is added.

B. When recovering 90% or more of Pt, Pd and Rh Cr ⁶⁺ ions (g / liter) ≧ 22.5 + 3.75 ×
T (° C) b. When recovering 40% or more of Pt, Pd and Rh Cr ⁶⁺ ions (g / liter) ≧ 52.5 + 3.75 ×
T (° C) However, in the above formula, T is the temperature of the waste liquid expressed in ° C.

The Cr ⁶⁺ ions are K ₂ Cr ₂ O ₇ and CrO.
_{3, K 2 CrO 4, Na} 2 CrO 4 · 4H 2 O, Na 2
Cr ₂ O ₇ · 2H ₂ O, BaCrO ₄ , (NH ₄ ) ₂ C
It is added in a form of being dissolved in hydrochloric acid such as rO ₄ , (NH ₄ ) ₂ Cr ₂ O ₇ .

[0010]

[Function] By adding Cr ⁶⁺ ions to the hydrochloric acid pickling waste liquid containing Pt ions, Pd ions and Rh ions, P
t ion, Pd ion, Rh ion are metal Pt, metal P
d, it became clear that it could be separated from the pickling solution by precipitating it instead of the metal Rh. This Pt ions to hydrochloric acid, Pd ion, for the additional inclusion of a catalyst such as Rh ions, further NO ₃ ^-
It was found in an experiment for investigating the influence of various dissolved ions in a pickling solution obtained by selectively adding ions. In Table 1, 240 g / liter of HCl, 10 g / liter of HNO ₃ and 50 of Pd ions are used.
30 g / liter of Fe ²⁺ ions and Fe ³⁺ ions were added to a hydrochloric acid aqueous solution adjusted to be added as mg / liter PdCl ₂ .
About 7 g / liter of Cr ³⁺ ions and Cr ⁶⁺ ions, FeCl ₂ .4H ₂ O, FeCl ₃ .6H ₂ O,
The formation of precipitates after addition with CrCl ₃ .6H ₂ O and K ₂ Cr ₂ O ₇ is shown. Only when Cr ⁶⁺ ions were added, metal Pd could be separated by precipitation. Since the saturation solubility of Pt ion, Pd ion, and Rh ion was drastically changed by the addition of Cr ⁶⁺ ion, it is considered that precipitation separation can be easily performed.

[0011]

[Table 1]

[0012]

【Example】

Example 1 SUS430 was immersed in a treatment solution prepared by adding 250 g / liter of HCl, 10 g / liter of HNO ₃ , 50 mg / liter of Pd ions and PdCl ₂ as PdCl ₂ , and 85 g / liter of SUS430 after pickling treatment. Cr ⁶⁺ ions were added in the form of K ₂ Cr ₂ O _{7 to} the dissolved pickling waste liquid, the waste liquid temperature and the addition amount were changed, and Pd which was separated as a precipitate was recovered.

FIG. 1 shows the recovery rate of Pd in relation to the added amount of Cr ⁶⁺ ions and the liquid temperature. As shown in the figure, the area between the recovery rates of 40% and 90% is
It can be seen that there is a relatively narrow range of Cr ⁶⁺ ion addition amount and liquid temperature, and the Cr ⁶⁺ ion addition amount and liquid temperature should be specified considerably.

Even if a pickling solution was prepared using the Pd thus recovered, the same cutting efficiency as that of the pickling solution initially added as PdCl ₂ was obtained.

Example 2 Cr type stainless steel, Ni type stainless steel, and low Cr steel were pickled, and the recovery amount of the liquid to be discarded was investigated by changing the temperature and the amount of Cr ⁶⁺ ion added. The results are shown in Table 2. A new liquid was prepared using the recovered Pt, Pd, and Rh, and the liquid was blended. The melt cutting efficiency was excellent, and the smoothness of the surface after the melt cutting was also excellent. Pt, Pd, R by chemicals
Chloride of h, PdCl ₂ as nitric oxide, H ₂ PtCl
₆ , H ₂ PtCl ₄ , RhCl ₃ .3H ₂ O, [Pd
(NH ₃ ) ₂ ] Cl ₂ , Pd (NO ₃ ) _{2 and the} like were obtained, and a smoothing ability equivalent to that of an aqueous hydrochloric acid solution and a smooth surface after pickling were obtained.

[0016]

[Table 2]

[0017]

The present invention has the following effects.

(1) The expensive metal component added as a catalyst can be recovered and reused without deteriorating the abrading ability and surface smoothness of the pickling solution.

(2) Therefore, the utilization efficiency of the high-speed pickling solution to which the catalyst is added can be increased.

(3) Pickling It becomes possible to carry out inexpensive pickling by reusing Pt, Pd, Rh, etc., which account for a large proportion of the cost of the chemical.

[Brief description of drawings]

FIG. 1 shows the relationship between waste liquid temperature, Cr ⁶⁺ ion addition amount, and Pd recovery rate.

Claims (2)

[Claims] 1. A hydrochloric acid Pt ion, Pd ion, for the additional inclusion of a catalyst such as Rh ions, further NO ₃ ^- ions selectively added to the pickling solution by liquid waste after pickling steel quality metal comprising A method for recovering Pt, Pd, and Rh metals in a pickling waste liquid, in which Cr ⁶⁺ ions are added. 2. The Pt and P in the pickling waste liquid according to claim 1, wherein the amount of Cr ⁶⁺ ions is T and the waste liquid temperature is ° C, and an amount satisfying the following conditions (a) and (b) is added to the waste liquid.
d, Rh metal recovery method. I. When recovering 90% or more of Pt, Pd and Rh Cr ⁶⁺ ions (g / liter) ≧ 22.5 + 3.75 ×
T (° C) b. When recovering 40% or more of Pt, Pd and Rh Cr ⁶⁺ ions (g / liter) ≧ 52.5 + 3.75 ×
T (° C).