JP2000087007A - Reducing agent for metal recovery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a reducing agent for enabling metals containing a noble metal to recover effectively and furthermore, having no adhesion of metals or the like to an inner wall or the like of a reaction vessel by using one selected from hydrazinoalcohols or salts thereof as an active ingredient. SOLUTION: This reducing agent makes at least one selected from hydrazinoalcohols represented by the general formula, HORNHNH2 (wherein R is a 1-8C alkylene group of a straight or branched chain) and salts thereof as an active ingredient. As the reducing agent, particularly 4-hydrazinobutanol, and hydrochloride, sulfate, sulfonate and sulfamate thereof are preferable. The reducing agent can be used for various metals to be recovered by reduction, and to use it for recovering noble metals of gold, silver, palladium, osmium, rhenium or the like is preferable. The reducing agent is preferably used for recovering metals from an aqueous solution. An amount used of the reducing agent is usually at least 1.5 mole, preferably 3-7 mole. per 1 mole of a metal to be recovered.

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.

[0005] Recently, safety of factory workers has been emphasized.
As the work environment is being reviewed, there is a demand for a metal recovery reducing agent that is more safe for the human body than hydrazine hydrate or the like. 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.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a compound of the general formula HOR
According to the present invention, there is provided a metal-reducing reducing agent comprising at least one selected from hydrazino alcohols represented by NHNH ₂ (wherein R is a linear or branched alkylene group having 1 to 8 carbon atoms) and salts 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.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a general formula HORNHNH ₂ (where R represents 1 carbon atom) is used as a reducing agent.
Specific examples of hydrazino alcohols represented by the following formulas (1) to (8), such as hydrazinomethanol, 1-hydrazinoethanol,
Hydrazinoethanol, 1-hydrazinopropanol,
2-hydrazinopropanol, 3-hydrazinopropanol, 1-hydrazinobutanol, 2-hydrazinobutanol, 3-hydrazinobutanol, 4-hydrazinobutanol, 1-hydrazinopentanol, 2-hydrazinopentanol, 3-hydrazinopentanol, 4-hydrazinopentanol, 5-hydrazinopentanol,
5-hydrazinohexanol, 6-hydrazinohexanol, 7-hydrazinoheptanol, 8-hydrazinooctanol and their inorganic salts such as hydrochloride, sulfate, phosphonate, sulfamate, carboxylic acid, and anhydride thereof Organic acid salts such as oligomers or polymer salts, etc., including organic substances. Examples of the carboxylic acid and its anhydride include oxalic acid, benzoic acid, maleic anhydride, and acrylic acid. Examples of the polymer include polyacrylic acid. Among them 4
-Hydrazinobutanol and its hydrochloride, sulfate, phosphonate, sulfamate are particularly preferred.

The hydrazino alcohol used in the present invention can be produced by reacting a halogenated alcohol with hydrazine. For example, 4-hydrazinobutanol can be produced by reacting 4-halogenobutanol with hydrazine. The hydrazino alcohol of the present invention has a strong reducing power and is a safer reducing agent.

The reducing agent for recovering metals of the present invention can be used for recovering various metals that can be recovered 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 precious metal decoration) 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 metal to be collected is alkaline, the collection may be performed as it is, or may be performed after 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, and the like. 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 alkali 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 with 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, hydrazine hydrate, hydrazine sulfate, hydrazine hydrochloride, 1-aminopyrrolidine, sulfurous acid, sodium sulfite, formalin, as long as the preferable effects of the reducing agent of the present invention are not impaired.
A reducing agent such as formic acid can be used in combination. Metal precipitated in the reaction system by the reducing agent of the present invention, as in the conventional method,
It can be easily recovered by simple separation and purification means such as filtration.

[0013]

The present invention will be described more specifically with reference to examples and comparative examples. Examples 1 to 3 and Comparative Example 1 18.76 g of gold (Au) was placed in a 500 ml beaker and dissolved by heating in 100 ml of aqua regia. The heating was relaxed, and the reducing agent and water shown in Table 1 were added little by little. The deposited gold was filtered, washed with concentrated hydrochloric acid and hot water. The precipitate on the filter paper was put into a crucible together with the filter paper and calcined. Table 1 shows the amount of the reducing agent used and the gold recovery rate.

[0014]

[Table 1]

Examples 4 to 6 and Comparative Example 2 10.00 g of gold (Au) was placed in a 300 ml beaker and dissolved by heating in 50 ml of aqua regia. 10m concentrated hydrochloric acid while boiling
The mixture was added three times each, and water was added to make the liquid volume 100 ml.
The reducing agents shown in Table 2 were added little by little, and the precipitates were obtained in Example 1.
The gold was recovered by the same treatment as described above. Table 2 shows the amount of the reducing agent used and the gold recovery rate.

[0016]

[Table 2]

[0017]

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.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Takashi Kitajima 463 Kagasuno, Kawauchi-cho, Tokushima City, Tokushima Prefecture Inside the Tokushima Plant of Tsukashima Chemical Co., Ltd. (72) Inventor Tomohiro Furuichi 463 Kagasuno, Kawauchi-machi, Tokushima City, Tokushima Prefecture Inside the Tokushima Plant

Claims (3)

[Claims] 1. An active ingredient comprising at least one selected from hydrazino alcohols represented by the general formula HORNHNH ₂ (wherein R is a linear or branched alkylene group having 1 to 8 carbon atoms) and salts thereof. Reducing agent for metal recovery. 2. The reducing agent according to claim 1, wherein the hydrazino alcohol is 4-hydrazinobutanol. 3. The reducing agent according to claim 1, wherein the metal is a noble metal.