WO2007023521A1

WO2007023521A1 - Method of separating gold

Info

Publication number: WO2007023521A1
Application number: PCT/JP2005/015227
Authority: WO
Inventors: Katsutoshi Inoue; Hidetaka Kawakita; Kumiko Kajiyama; Daisuke Hirata
Original assignee: Saga University; Muromachi Chemicals Inc.
Priority date: 2005-08-22
Filing date: 2005-08-22
Publication date: 2007-03-01
Also published as: JPWO2007023521A1; JP4827146B2

Abstract

A method in which using an inexpensive adsorbent, gold being present in a low concentration in an aqueous hydrochloric acid solution is separated and recovered as gold particles. An adsorbent obtained by sulfuric acid treatment of persimmon peel is brought into contact with an aqueous hydrochloric acid solution containing at least gold as a metal ion, thereby effecting selective adsorption of gold particles onto the adsorbent.

Description

Specification

Gold separation method

Technical field

[0001] The present invention relates to a technique for separating gold for the purpose of isolating, recovering, or purifying gold, and in particular, only gold from various metals dissolved in an aqueous hydrochloric acid solution. The present invention relates to a technology for selectively and effectively separating particles as solid particles (gold particles).

Technical background

[0002] Gold has been used in many fields in recent years as a jewelry material and electrical / electronic material in addition to jewelry. Since gold is expensive, recovery from various wastes and waste liquids has attracted attention. However, the amount of gold contained in the waste is very small, and it is easy to selectively separate and recover gold from other metals present in large excess.

[0003] In recent years, solvent extraction methods and ion exchange methods have been adopted for the recovery of precious metals in the anode slime of copper and nickel ole. In these recovery processes, metals are completely dissolved in an aqueous hydrochloric acid solution containing chlorine gas and sodium hypochlorite, and then each precious metal is recovered by solvent extraction or ion exchange. Details of the solvent extraction method and ion exchange method for the recovery of precious metals are described in, for example, a review in Non-Patent Document 1 and the like.

Non-Patent Document 1: Junji Shibata, Akihiko Okuda “Precious Metal Recycling Technology” Resources and Materials, 118 卷 1, p. 1 -8 (2002)

[0004] In the current recovery process, gold is solvent extracted using dibutyl carbitol, methyl isobutyl ketone, or tributyl phosphate. Such a solvent extraction method is also introduced in Non-Patent Document 2, for example. However, in these solvent extractions, other precious metals and base metals are also extracted depending on the conditions, so that a multi-stage extraction / back-extraction operation is necessary, which increases the cost of separation and purification.

Non-Patent Document 2: Hideo Koshimura “Precious metals, present status of recovery technology” Chemical Technology Journal MOL, No. 4, p. 76 -81 (1986)

[0005] For the recovery of gold and silver from a basic cyan solution, an adsorption method using activated carbon or an ion exchange method using a strong basic anion exchange resin is widely employed. But these Even in the method, the selectivity of activated carbon and resin is not so high, so the base metal is adsorbed considerably. In addition, since activated carbon and resin are difficult to desorb and elute after adsorption, a very high cost method is used in which all of these are incinerated and the metal is recovered after adsorption. Intensity Activated charcoal and resin are easy to incinerate, and tar and coke-like substances are often generated that are cumbersome after treatment.

[0006] Recently, a metal adsorption separation technique using tannin contained in plants has attracted attention as one of easy-to-handle materials. Tannin is one of the organic substances that make up plants, and has many phenol, catechol, and pyrogallol sites in its molecular structure. Plant-derived natural substances rich in tannin include grapes, green tea, and red wine. In particular, the amount of polyphenol contained in grapes is said to be about 200 times that of red wine. Tannin is a component of plant bitterness and astringency, and what is particularly abundant in persimmon is called persimmon tannin. Mature astringents at the right time for harvest contain 1-2% water-soluble tannins and immature astringents contain 5-6% persimmon tannins.

[0007] For example, Sakaguchi et al. Reported in Non-Patent Document 3 etc. that tannin is effective for the adsorption and removal of uranium and thorium.

Non-Patent Document 3: T. Sakaguchi, A. Nakajima; separation Science and Technology, 29-2, p. 205-221 (1994)

[0008] In addition, non-patent documents 4 and 5 report the adsorption of metal ions by an adsorbent using mimosa tannin and watnoretannin as raw materials.

Non-Patent Document 4: Yamaguchi Tohiko, Iura Yoshinori, Higuchi Mitsuo, Sakata Isao; Journal of the Wood Society, 37 卷 9, p. 815-820 (1991)

Non-patent document 5: Y. Nakano, K. Takeshita, T. Tsutsumi; Water Research, 35-2, p. 496-500 (2001)

However, these adsorbents are prepared by extracting the above tannin components from the plants containing them, and are expensive because they require the cost of extraction and recovery from those plants.

[0010] In previous researches, the present inventors found that tannin components such as astringent peels were not used by using an adsorbent prepared by cost-effectively extracting tannin components from plants containing them. It has been found that uranium and thorium can be recovered by using as an adsorbent the plant part itself containing a large amount as a raw material. For example, Patent Document 1 has already reported it.

Patent Document 1: JP 2004-330005 A

[0011] The adsorbent disclosed in Patent Document 1 enables efficient recovery of uranium and thorium using straw skin, but in order to prepare an insoluble adsorbent in water. It was difficult to use paraformaldehyde, which is a harmful chemical substance, in the crosslinking process. Disclosure of the invention

Problems to be solved by the invention

[0012] An object of the present invention is to prepare an adsorbent without using a material that is burdensome to the human body and the environment, and effectively collect gold from various wastes and waste liquids at an unprecedented low cost. It is to provide a new technology that can be separated.

Means for solving the problem

[0013] As a result of intensive studies to solve the above-mentioned problems, the present inventor has found that specific adsorbents containing various metals can be obtained by using an adsorbent obtained by cross-linking cocoon skin only with sulfuric acid. The inventors have found that gold can be selectively separated from an aqueous solution, and have completed the present invention.

[0014] Forcibly, according to the present invention, the adsorbent obtained by treating sulfuric acid on the cocoon skin is brought into contact with an aqueous hydrochloric acid solution containing at least gold as a metal ion, whereby gold is added to the adsorbent. There is provided a method for separating gold, comprising a step of selectively adsorbing particles. The invention's effect

[0015] By using the present invention, it is possible to recover only gold from various waste liquids and wastes that can be provided as an aqueous hydrochloric acid solution as highly pure gold particles in a very selective and efficient manner.

Brief Description of Drawings

[0016] [Fig. 1] is a chemical formula showing a repetitive structure of persimmon tannin that constitutes persimmon skin as a raw material of the adsorbent used in the present invention.

[Fig. 2] Shows the relationship between adsorption percentage (A) of various metal ions and hydrochloric acid concentration ([HC1]). FIG. 3 shows the relationship between the amount of gold adsorbed and the concentration of gold remaining in hydrochloric acid.

FIG. 4 is an X-ray diffraction pattern of the adsorbent after gold is adsorbed.

FIG. 5 is a digital micrograph of the adsorbent after gold adsorption.

BEST MODE FOR CARRYING OUT THE INVENTION

[0017] The kakitannin (ニン tannin) as a raw material of the adsorbent used in the present invention is a substance in which four compounds of epicatechin 'catechin 3-gallate' epigallocatechin 'gallocatechin-3-gallate are chemically bound. It is. Their composition ratio is 1: 1: 2: 2 and has a repeating structure as shown in FIG. It is a high-molecular weight anthocyanin polymer with a molecular weight of about 15,000. In the adsorbent of the present invention, persimmon tannin is provided from persimmon skin, and astringent persimmon skin containing abundant persimmon tannin is particularly preferable.

[0018] This tannin is a water-soluble compound, and as it is, it elutes into an aqueous solution during the adsorption operation and significantly reduces the adsorption of the target substance. Cross-linking treatment is necessary to prevent such elution of tannin. In the past, crosslinking agents such as epichlorohydrin and norformaldehyde have been generally used for the crosslinking treatment, but these crosslinking agents are harmful and costly after use. Surprisingly, the present inventor is able to effectively absorb high-selective separation of gold by using only concentrated sulfuric acid in the cross-linking treatment of tannin without using a conventional cross-linking agent. It has been found that an agent can be obtained. This is because tannin has a large number of hydroxyl groups, so only a condensation reaction using concentrated sulfuric acid enables sufficient crosslinking, and the crosslinking reaction can be carried out between cellulose tannin molecules and also cellulose and hemisphere coexisting with tannin. It is thought to be performed between the polysaccharides of cellulose.

[0019] The cross-linking treatment for obtaining the adsorbent used in the present invention is carried out by pulverizing the astringent peel into a powder and then reacting it by stirring in an oil bath with concentrated sulfuric acid. After cross-linking treatment, neutralize with, for example, aqueous sodium hydrogen carbonate, wash thoroughly, for example, first with water, then with lmol / dm ³ hydrochloric acid, and finally with water again, then dry and then grind In this way, the target adsorbent is prepared. In this case, the ratio of the mixture of astringent peel and concentrated sulfuric acid is 1.0 to 0.5 kg, preferably 0.7 to 0.8 kg with respect to concentrated sulfuric acid (generally 98 to 90% concentrated sulfuric acid) l dm ³ It is. The temperature of the oil bath at this time is 80 to 120 ° C, preferably 90 to 1 10 ° C. The reaction time is 12 to 48 hours, preferably 18 to 30 hours. [0020] By using the scab-derived adsorbent prepared by the cross-linking treatment as described above, various forms of aqueous hydrochloric acid solutions containing various metal ions and conventional batch operations or column operations can be used. By contacting the adsorbent, gold can be selectively adsorbed and recovered.

[0021] Base metals such as zinc, iron, lead, copper, and cobalt and precious metals such as gold, palladium, and platinum exist as chloride complexes of anions in relatively high concentration aqueous chloride solutions. Is known to be adsorbed on, for example, anion exchange resins having primary to quaternary amino groups. For example, regarding adsorption from hydrochloric acid by Dowe X 1 which is a quaternary ammonium salt type strongly basic ion exchange resin, a very large number of metals are illustrated in Non-Patent Document 6 and the like.

Non-Patent Document 6: Edited by J. A. Marinsky, Ion Exchange, vol. 1, p. 317, Maec el Dekker, New York (1966)

[0022] On the other hand, the adsorbent of the present invention selectively adsorbs only gold from an aqueous chloride solution, and does not adsorb base metals as described above and noble metals other than gold at all. The chloride concentration range for selectively adsorbing gold is 0.01 to 12 mol / dm 3 concentration range, preferably 0.0 to 8 mol / dm ³ when the aqueous chloride solution is hydrochloric acid. Concentration range.

[0023] According to the present invention, when an adsorbent derived from sulfuric acid-treated carp skin is brought into contact with an aqueous hydrochloric acid solution containing low concentrations of gold and other metal ions, only gold is selectively adsorbed. The adsorbed gold is reduced and deposited as gold particles. The average particle size of the gold particles is about several microns to several hundred microns, and can be easily separated from the adsorbent particles by existing methods such as sieving and gravity sorting (specific gravity difference sorting).

Hereinafter, embodiments of the present invention will be described in more detail by way of examples. However, the present invention is not limited to these examples.

Example 1

[0024] Preparation of adsorbent

The astringent peel produced in the production of dried koji was powdered as it was, and 15 g was taken into 20 ml of 98% concentrated sulfuric acid, and the mixture was subjected to crosslinking treatment by heating and stirring at 100 ° C for 24 hours . The reaction mixture was added to 500 ml of an aqueous sodium bicarbonate solution with a concentration of 100 g / dm ³ Was added to neutralize, and then washed with 1000 ml of distilled water at 50 ° C. and then with 1000 ml of distilled water at room temperature. Thereafter, the mixture was stirred with 500 ml of hydrochloric acid having a concentration of ImolZdm ³ for 12 hours, filtered, and the filtrate was washed with distilled water until the pH became neutral. After that, it was put in a dryer at 70 ° C and dried for 24 hours. After that, it was pulverized with a ball mill, sieved, and a particle size of 150 microns or less was used as an adsorbent.

Example 2

[0025] Effect of hydrochloric acid concentration on gold adsorption

An aqueous hydrochloric acid solution of gold (III) having a concentration of 0.2 mmol / dm ³ was prepared by dissolving chloroauric acid in hydrochloric acid having a concentration of 0.:! To 8 mol / dm ³ . 10 ml of this aqueous solution and 10 mg of the adsorbent prepared in Example 1 were put into a triangular flask with a stopper, and adsorbed by shaking for 30 hours in a constant temperature water bath at 30 ° C. The concentration of gold in the solution before and after adsorption was measured with an AA-6650 type atomic absorption photometer manufactured by Shimadzu, and the amount of adsorption was determined. The concentration of hydrochloric acid in the solution was determined by neutralization titration. Also, the adsorption percentage (A) was obtained from the decrease in gold concentration in the solution by adsorption according to the following formula.

Adsorption percentage = [(Gold concentration before adsorption-Gold concentration after adsorption) Gold concentration before Z adsorption) X 100

The results are shown in Figure 2 as the relationship between the percentage of adsorption (A) and the concentration of hydrochloric acid ([HC1]). Gold is adsorbed almost quantitatively without much influence on the concentration of hydrochloric acid.

By the same method, the base metals such as iron (III), zinc (II), copper (II), tin (IV) and the noble metals palladium (II) and Platinum (IV) was adsorbed. Some platinum adsorption was seen, but negligible compared to gold. There is very little adsorption of other metals.

Example 3

[0026] Relationship between gold adsorption amount and gold concentration

By dissolving chloroauric acid in hydrochloric acid at a concentration of 0.1 mol / dm ^3, a solution of gold hydrochloric acid at a concentration of! ~ 60 mmol Zd m ³ was prepared. 1 Oml of this aqueous solution and 10 mg of the adsorbent prepared in Example 1 were placed in a stoppered triangular flask and adsorbed by shaking for 30 hours in a constant temperature water bath at 30 ° C. AA-6650 type atom made by Shimadzu The amount of adsorption was determined by measuring with an absorptiometer.

Figure 3 shows the relationship between the gold adsorption amount (Q) and the gold concentration (Ce) in the solution after adsorption. At first, the amount of gold adsorbed increases as the gold concentration increases, and at a concentration of about lOmmolZd m ³ or more, it becomes a constant value regardless of the concentration. From this constant value, the saturated adsorption amount in this concentration range was determined to be about 4.5 mmol Zg. Compared with other adsorbents, this adsorption amount is extremely large. Furthermore, a BET-type adsorption behavior was observed in which the amount of adsorption increased further when the gold concentration was 30 mmol / dm ³ or more. Thus, the adsorbent of the present invention has an extremely excellent adsorption capacity for gold.

Example 4

[0027] Gold adsorption form

The adsorbent after adsorbing gold was washed with water and dried, and then X-ray diffraction was observed using a RINT-8829 type X-ray diffraction apparatus manufactured by Rigaku Corporation. The results are shown in Fig. 4.

2 Four sharp peaks are observed at Θ = 83.12, 44.22, 64.50 and 77.42, indicating the presence of elemental gold.

Example 5

[0028] Formation of gold particles

When the adsorbent after adsorbing gold was washed with water and dried, it was observed using a Keyence digital microscope VH X200, and the image shown in FIG. 5 was obtained. Here, the gold particles are shining white, and the black part is the adsorbent of the crust. It can be seen that gold particles of several hundred microns are generated.

Industrial application fields

[0029] The yield of Japanese astringents is 117,900t / year, and many of them are peeled and removed, then processed into dried straw and used for food. About 9% of the skin generated when making dried straw is discarded. The adsorbent used in the present invention can be prepared by applying a simple sulfuric acid treatment using such a material.

By virtue of this, the present invention separates and recovers low-concentration gold in wastes and waste liquids in various industrial fields, such as anodic slime leachate produced in electrolytic ironmaking such as copper and nickel. Or, it can be refined and inexpensive and easy to handle. Can also be utilized as a gentle process.

Claims

The scope of the claims

[1] The step of selectively adsorbing gold particles on the adsorbent is carried out by bringing the adsorbent obtained by subjecting the cocoon skin to sulfuric acid treatment with an aqueous hydrochloric acid solution containing at least gold as metal ions. A method for separating gold, comprising:

[2] The method for separating gold according to [1], wherein the cocoon skin is an astringent skin.

[3] The method for separating gold according to claim 1 or 2, wherein the concentration of the aqueous hydrochloric acid solution is from 0.:! To 8 mol / dm ³ .

[4] The method for separating gold according to any one of claims 1 to 3, further comprising a step of separating the gold particles from the adsorbent.