JPH11302626A - Reducing agent for metal recovery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a reducing agent usable to efficiently recover metals including noble metals and not problematic in the deposition of metals, etc., on e.g. the inside wall of a reactor by using a 1-aminopyrrolidine (salt) as the effective component. SOLUTION: This agent contains 1-aminopyrrolidine or a hydrochloride, sulfate, phosphate, or like salt thereof as the effective component. Metals can be recovered in the following way. Scraps of noble metal ornaments are dissolved in aqua regia, concentrated sulfuric acid is added to the solution, and the nitric acid contained in aqua regia is perfectly removed. At least 1.5 mol, desirably, 3-7 mol of the reducing agent is added per mol of the metals to be recovered, and optionally, an alkali agent is added to adjust the system to a pH of 3-13, desirably 5-10.5. The resulting mixture is heated to 20-120 deg.C, desirably, 50-85 deg.C under or without agitation and left standing for at least 10 min, desirably, 30 min to 1 hr to deposit metals containing noble metals. The alkali agent is exemplified by potassium hydroxide or sodium hydroxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a novel reducing agent for recovering metals. The metal recovery reducing agent of the present invention is effective for reducing and recovering a metal, preferably a noble metal, from a solution.

[0002]

2. Description of the Related Art In recent years, in various fields such as an electric / electronic field and an organic synthesis field, with the remarkable development of industrial technology, precious metals such as gold, silver, palladium, platinum, rhodium, iridium, osmium, rhenium, etc. Are widely used not only as decorative articles but also as electronic industrial materials such as semiconductors, circuit boards, cathode ray tubes, etc., and catalysts for organic chemical reactions. On the other hand, it is a well-known fact that the amount of production of precious metals is very small as compared with other metals, and therefore, it is a major issue to efficiently recover and reuse precious metals.

[0003] Recovery of precious metals involves dissolving with acid, electrolysis, metal complex formation, metal compound adsorbents, solvent extraction, salting out, ionization into scraps of precious metal decorations, waste liquids containing noble metals and noble metal ions, and plating waste liquids. A noble metal compound is obtained by performing separation and purification means such as chromatography, and the noble metal compound is reduced. The recovery is as high as 95%.

[0004]

As a method for reducing a noble metal compound, a method using a reducing agent is generally used because the equipment and chemicals used are inexpensive and the operation is easy. Examples of the reducing agent include hydrazine hydrate, hydrazine sulfate, hydrazine hydrochloride, sulfurous acid, sodium sulfite, formalin, formic acid and the like. However, when these reducing agents are used, there is a problem that noble metals and by-products generated by the reduction reaction easily adhere to the inner wall of the reaction vessel and the like, and the recovery rate of the noble metals decreases. In order to achieve the above-mentioned 95% recovery rate, it is necessary to recover also the noble metal adhered to the inner wall and the like of the reaction vessel. However, at present, many complicated steps are required. An object of the present invention is to provide a reducing agent for metal recovery that can efficiently recover a metal containing a noble metal and that does not adhere to an inner wall or the like of a reaction vessel.

[0005]

Means for Solving the Problems The present invention relates to a reducing agent for recovering metals containing at least one selected from 1-aminopyrrolidine and a salt thereof as an active ingredient. ADVANTAGE OF THE INVENTION According to the reducing agent for metal collection | recovery of this invention, a metal containing a noble metal can be precipitated, without adhering to the inner wall of a reaction container, and improvement of a collection rate and simplification of a collection | recovery process are achieved. Therefore, the metal recovery reducing agent of the present invention is particularly useful for recovering a metal from a solution of the metal. Furthermore, the reducing agent for recovering metals of the present invention has very low toxicity, and is very useful in the present situation where the preservation of the natural environment and the safety of employees in workplaces are particularly important.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The reducing agent for recovering metals according to the present invention comprises:
-At least one selected from aminopyrrolidine and salts thereof is used as an active ingredient. 1-Aminopyrrolidine is a known compound and is used, for example, as an intermediate for the production of pharmaceuticals and agricultural chemicals. Examples of the salt of 1-aminopyrrolidine include, for example, hydrochloride, sulfate, phosphate and the like. Among these, 1-aminopyrrolidine itself can be preferably used.

The reducing agent for recovering metals of the present invention can be used for recovering various metals recoverable by reduction.
It is preferably used for recovering precious metals such as palladium, platinum, rhodium, iridium, osmium, rhenium and the like, and particularly preferably used for recovering gold, palladium, platinum and the like. The metal recovery reducing agent of the present invention is used for recovering a metal from an organic solvent solution or an aqueous solution containing a metal, preferably from an aqueous solution. In recovering the metal in the present invention, the method can be carried out in the same manner as in the conventional method, except that the reducing agent of the present invention is used instead of the conventional reducing agent. However, as described later, the amount of the reducing agent used, the pH of the reaction system, the reaction temperature, the reaction time, and the like can be appropriately changed.

As a specific example of the metal recovery in the present invention, a scrap of metal (for example, a scrap of a precious metal ornament) is dissolved in aqua regia and concentrated hydrochloric acid is added thereto to remove nitric acid contained in the aqua regia. After completely removing, the method of adding the reducing agent of the present invention, the method of adding the reducing agent of the present invention to the waste liquid after metal purification or the plating waste liquid, and the catalyst used in the synthesis of the organic compound (for example, a noble metal catalyst) Dissolved in acid,
This can be passed through an ion exchange resin to adsorb only the metal derived from the catalyst, elute this metal with an acid, and add the reducing agent of the present invention. The amount of the reducing agent of the present invention depends on the type of the reducing agent used and the metal to be recovered,
It can be appropriately selected from a wide range according to the pH value, reaction temperature and the like in the system, but is usually 1.5 mol or more, preferably 3 to 7 mol, per 1 mol of the metal to be recovered.

In the present invention, an alkali agent can be added to the system in order to reduce the amount of the reducing agent used. If the pH of the solution containing the metal to be recovered is alkaline, the recovery may be performed as it is, or the recovery may be performed after further adding an alkali agent as needed.
On the other hand, when the pH of the solution containing the metal is acidic, the recovery may be carried out as it is, but it is preferable to carry out the recovery after adding an appropriate amount of an alkali agent. Here, the alkali agent is not particularly limited, and known agents can be used. For example, potassium hydroxide, hydroxides of alkali metals such as sodium hydroxide, potassium carbonate, carbonates of alkali metals such as sodium carbonate, Ammonia, ammonium carbonate and the like can be mentioned. Among these, an alkali metal hydroxide can be preferably used. One alkali agent can be used alone, or two or more alkali agents can be used in combination. The amount of the alkaline agent to be added can be appropriately selected from a wide range according to the pH of the solution to be recovered and the metals and other components contained in the solution.
The alkali agent is added to a degree, preferably 5 to 10.5.

The recovery of metal by the reducing agent of the present invention is usually carried out in two steps.
The reaction is performed at a temperature of about 0 to 120 ° C, preferably 50 to 85 ° C. The metal recovery by the reducing agent of the present invention is performed with or without stirring. In the present invention, the reducing agent of the present invention is added to a solution containing the metal to be recovered, and at the same time, the metal precipitates at a recovery rate close to 100%. The reaction may be allowed to proceed usually for at least 10 minutes, preferably for about 30 minutes to 1 hour. In the present invention, conventional reducing agents such as hydrazine hydrate, hydrazine sulfate, hydrazine hydrochloride, sulfurous acid, sodium sulfite, formalin and formic acid can be used in combination as long as the preferable effects of the reducing agent of the present invention are not impaired. The metal precipitated in the reaction system by the reducing agent of the present invention can be easily recovered by a simple separation and purification means such as filtration as in the conventional method.

[0011]

The present invention will be described more specifically with reference to examples and comparative examples. Example 1 1 liter of aqua regia (pH = 5) containing platinum at a concentration of 1.3 × 10 ⁻³ mol / l was placed in a reaction vessel, and a 10% by weight aqueous solution of sodium hydroxide was added dropwise to adjust the pH to 10%. Was adjusted. While heating this solution to 80 ° C., 1.95 g of a 60% by weight aqueous solution of 1-aminopyrrolidine was stirred.
(1.3 × 10 ⁻² mol), platinum was deposited without adhering to the inner wall of the reaction vessel. The precipitated platinum was recovered by filtration. The recovery of platinum was 99.8%.

Comparative Example 1 Instead of a 60% by weight aqueous solution of 1-aminopyrrolidine, 0.81 g of an 80% by weight aqueous solution of hydrazine hydrate (1.
When platinum was recovered in the same manner as in Example 1 except that 3 × 10 ^-2 mol) was used, platinum was partially adhered to the inner wall of the reaction solution. Recovery rate of platinum by filtration is 8
Only 6%.

Example 2 The relationship between the amount of the reducing agent of the present invention and the recovery of platinum was examined.
As a sample, as in Example 1, 1.3 × 10
Aqua regia (pH = 5) 1 containing ^-3 mol / L
A 10 wt% aqueous solution of sodium hydroxide was added dropwise to the liter to adjust the pH to 10. 1 as a reducing agent
-Aminopyrrolidine was used. Reaction temperature 80-85 ° C
The recovery rate of platinum was examined by changing the amount of the reducing agent while controlling the amount of platinum. The results are shown in FIG. From FIG. 1, it can be seen that at a platinum concentration / reducing agent concentration (molar ratio) of 3 or more, a recovery of 99% or more is achieved.

[0014]

According to the present invention, it is possible to obtain a metal-reducing reducing agent which can efficiently recover metals including noble metals and which does not adhere to the inner walls of the reaction vessel. Furthermore, the reducing agent for recovering metals of the present invention has very low toxicity, and is very useful in the present situation where the preservation of the natural environment and the safety of employees in workplaces are particularly important.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the addition amount (concentration) of a reducing agent (1-aminopyrrolidine) and the recovery rate of platinum.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akihiro Nabeshima 463 Kagasuno, Kawauchi-machi, Tokushima City, Tokushima Prefecture Inside the Otsuka Chemical Co., Ltd. Inside Tokushima Factory

Claims (2)

[Claims] 1. A reducing agent for recovering a metal, comprising as an active ingredient at least one selected from 1-aminopyrrolidine and a salt thereof. 2. The reducing agent according to claim 1, wherein the metal is a noble metal.