JP2003293049A - Method for recovering silver from slag containing silver and lead - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To recover silver and lead from silver- and lead-containing slag of copper electrolysis slime with superior separability. <P>SOLUTION: In this silver recovering method, a reducing material and a slag-forming material are added to the silver-and lead-containing slag obtained from the copper electrolysis slime, and reduction refining is carried out to form the silver contained in a metallic phase into lead bullion. After separation of slag, air or oxygen-enriched air is blown into the metallic phase and oxidation refining is performed to subject the lead to slagging and recover the crude silver in the metallic phase. It is preferable to carry out the oxidation refining of the lead bullion in two steps. First, a first-step oxidation refining is performed until 5 to 10% lead content in the metallic phase is reached and then the slag phase is separated; then a second-step oxidation refining is performed until ≤0.1% lead content in the metallic phase is reached and then the slag phase is separated. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for efficiently separating and recovering silver from lead from a silver lead-containing slag, particularly a silver lead-containing slag obtained by subjecting a copper electrolytic slime to a wet chlorination treatment.

[0002]

2. Description of the Related Art Conventionally, in the copper electrolysis process in copper smelting,
Impurities insoluble in the electrolytic solution are by-produced as a residue. This copper electrolytic slime contains a considerable amount of platinum, selenium, tellurium, lead, gold, silver, copper, etc., and many methods for separating and recovering these metals have been proposed so far. Due to the various properties of these metals, it is difficult to separate and recover all the metal species simultaneously by a single method. Therefore, separate or recover two metals individually or simultaneously. The method of doing so far has been tried. A continuous processing system combining these methods is known.

Of these, regarding lead and silver, for example, Japanese Examined Patent Publication No. 60-59975, a copper electrolytic slime intermediate treated product containing lead as a sulfate and silver as a chloride is treated with alkali hydroxide or The residue obtained by solid-liquid separation after reacting with an aqueous solution of alkali carbonate is further reacted with a nitric acid solution to elute lead in the residue as lead nitrate, while leaving silver in the residue and solid-liquid separating it. A method for concentrating silver to separate lead and silver is described. Although this treatment method has a higher silver concentration effect than the conventional method, it requires the addition of an excess amount of alkali, and if the reaction temperature exceeds room temperature, the silver elutes together with lead, making it difficult to separate lead and silver. There is a problem such as becoming.

Further, in JP-A-4-236731, a copper electrolytic slime is roasted to recover a roasted starch containing a noble metal, bismuth and lead, and a predetermined amount of iron is added to the roasted starch. It describes a method of melting and producing high antimony slag and noble lead, and treating this noble lead in a silver-separation step. Although this method has good separability of lead and silver, it has a problem that an electrolytic recovery step of silver and an electrolytic recovery step of gold are required because gold is mixed in when a silver ingot is manufactured in the melting step. Further, since this treatment method is a dry treatment, it is difficult to combine noble metals other than silver and gold with a wet method.

In Japanese Unexamined Patent Publication No. 9-316559, decoppered slime is leached with chloride to form a precipitate containing silver chloride as a main component, sodium carbonate is added thereto to dechlorinate, and further leaching with ammonia is performed. Extract silver into the solution, add caustic soda to the silver chloride obtained by neutralizing it to convert it to silver oxide, and add reducing agents such as sugars and hydrazine to this to remove the silver oxide in the residue. A method for reducing and recovering metallic silver is described. This method can recover high-quality silver, but it requires a lot of work due to dechlorination treatment, ammonia leaching, neutralization treatment, conversion to silver oxide with caustic soda, reduction with sugars and treatment steps. Since it separates with other metal components such as lead, there is the inconvenience that another method must be used to recover lead. As a related technology, "Resources and Materials" (116. No. 6 published in 2000) describes that iron powder and sulfuric acid are added to the chlorination residue to perform silver reduction and lead sulfate conversion. However, it is difficult to simultaneously recover high-quality silver and lead simultaneously by this method alone. Further, this method is suitable when the lead content is low, and is not suitable for a treatment slag containing 10 wt% or more of lead because of large loss of silver.

[0006]

DISCLOSURE OF THE INVENTION The present inventors have solved the above problems in the conventional processing method, and efficiently recover high-quality silver from copper electrolytic slime by separating it from lead with a simple method. Provide a way to do.

[0007]

That is, the present invention relates to a silver recovery method having the following constitution. (1) Add a carbon material and a slag forming material to a silver lead-containing slag, perform reduction smelting to convert the silver contained in the metal phase into noble lead, separate the slag, and then add air or oxygen-enriched air to the metal phase. A method for recovering silver from a silver-lead-containing slag, which comprises blowing and oxidizing and slagging lead to slag to recover crude silver in a metal phase. (2) The silver recovery method according to (1) above, which uses a silver lead-containing slag obtained by subjecting copper electrolytic slime to wet chlorination. (3) Oxidative smelting of noble lead is carried out in two steps, firstly the oxidative smelting of the first step is carried out until the lead content of the metal phase becomes 5% to 10% to separate the slag phase, and then the second step. The silver recovery method according to (1) or (2) above, wherein the slag phase is separated by performing the staged oxidative smelting until the lead content of the metal phase becomes 0.1% or less. (4) The silver recovery method according to (3) above, in which the slag separated by the second-stage oxidation melting is returned to the first-stage oxidation melting and the oxidation melting is repeated. (5) In reduction smelting, carbon powder is used as a reducing material,
The method for recovering silver-lead according to any one of (1) to (4) above, wherein the amount of carbon powder added is 2 to 4 times the reaction equivalent of lead contained in the silver-lead-containing slag. (6) In reduction smelting, sodium carbonate is used as a slag forming material, and the addition amount of sodium carbonate is 1.2 to 2.0 times the total reaction equivalent of silver and lead contained in the silver lead-containing slag. 1)
~ The silver recovery method as described in any of (5). (7) Oxidation and smelting by adding silica material (1)-
The silver recovery method as described in any of (6).

According to the recovery method of the present invention, the silver lead-containing slag obtained from the copper electrolytic slime is continuously subjected to reduction smelting and oxidation smelting, and preferably the oxidation smelting is carried out in two steps. Can be efficiently separated from lead and recovered. That is, when the silver-lead-containing slag is oxidized and smelted from the beginning, a large amount of silver is contained in the slag mainly composed of lead oxide (PbO), resulting in a large silver loss. In the recovery method of the present invention, reduction smelting is first performed to make silver in the metal into a form of noble lead (Ag-Pb alloy) to suppress silver loss. Next, oxidation smelting is performed to convert lead into slag. Lead is more easily oxidized than silver and is converted to lead oxide to form slag. On the other hand, since silver remains as a metal without being oxidized, silver and lead can be easily separated. By carrying out this oxidative smelting in two steps, the loss amount of silver taken into the slag can be controlled, the silver recovery rate can be increased, and high-quality silver can be recovered.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The silver recovery method of the present invention will be specifically described below with reference to Examples. In addition,% is wt% unless otherwise indicated. The outline of the processing method of the present invention is shown in FIG.
As shown in the figure, the treatment method of the present invention comprises adding a reducing material and a slag forming material to a silver lead-containing slag, reducing and smelting the silver contained in the metal phase into noble lead, and extracting the slag. Injecting air or oxygen-enriched air into the phase, oxidizing and slagging lead to slag, and recovering the crude silver in the metal phase, preferably wet electrolytic chlorination of copper electrolytic slime. Oxidation smelting of the noble lead obtained by reduction smelting is carried out in two stages using the treated silver-lead-containing slag, and the first stage oxidization smelting leads to a lead content of 5% to 10% in the metal phase. This is a silver recovery method in which the slag is removed once, and then the second-stage oxidation smelting is performed until the lead content of the metal phase becomes 0.1% or less.

[Silver-Lead-Containing Slag] The copper electrolytic slime used in the present invention may be any by-product produced in ordinary copper electrolysis. As described above, generally in copper electrolysis, components insoluble in the electrolytic solution accumulate to form copper electrolysis slime. This copper electrolytic slime contains a large amount of platinum, selenium, tellurium, lead, gold, silver and copper. This copper electrolytic slime is wet-chlorinated to extract gold into the liquid. The wet chlorination treatment is performed by adding chlorine gas or hydrogen peroxide to copper electrolytic slime in a hydrochloric acid solution. At this time, the silver and lead in the slime become insoluble silver chloride and lead chloride and remain in the leaching slag.

The chlorinated copper electrolytic slime is thoroughly washed with water or warm water. By this washing with water, water-soluble chlorides such as gold chloride are removed from the leach slag. The amount of water or warm water used is preferably 1 liter or more per 1 kg of copper electrolytic slime. The content of gold contained in the copper electrolytic slime is generally about 5% or less, but most of it is extracted into the liquid by this wet chlorination treatment and washing.

[Reduction Smelting] The silver lead-containing slag is placed in a smelting furnace, a reducing material and a slag forming material are added, and reduction smelting is performed in a non-oxidizing atmosphere. By performing reduction smelting, silver and lead in the metal are alloyed to form precious lead (Ag-Pb alloy),
The amount of silver taken into the slag (the amount of silver loss) can be suppressed. Carbon powder such as coke may be used as the reducing material. The amount of carbon powder added is preferably 2 to 4 times the reaction equivalent of lead contained in the silver lead-containing slag. Further, sodium carbonate or the like can be used as the slag forming material. Sodium carbonate is preferable because it has a better slag separability than calcium carbonate. The amount of sodium carbonate added is suitably 1.2 to 2.0 times, preferably 1.5 to 1.7 times the total reaction equivalent of silver and lead contained in the silver lead-containing slag. Melting temperature is 1050
C. to 1200.degree. C. is suitable, and about 1100.degree. C. is preferable.

When the silver lead-containing slag is charged into a smelting furnace together with coke powder and saw ash and heated to 1050 ° C. to 1200 ° C., silver chloride and lead chloride in the slag are reduced as shown in the following formula, and silver lead is added. An alloy molten metal phase (noble lead) and a molten NaCl slag phase are formed. The desalted metal phase is separated from the slag phase and taken out, and sent to an oxidation furnace. 2AgCl + Na ₂ CO ₃ → 2Ag + 2NaCl + CO
₂ + 1 / 2O ₂ PbCl ₂ + Na ₂ CO ₃ + 1 / 2C → Pb + 2NaC
l + 3 / 2CO ₂

[Oxidation Smelting] A silver lead alloy (noble lead) metal phase is charged into an oxidation furnace to perform oxidation melting. Since lead is more easily oxidized than silver, it turns into lead oxide and forms slag. At the same time, other impurity metals are also oxidized to form slag. On the other hand, since silver is not oxidized and remains in the metal phase, silver and lead can be easily separated. In the oxidation furnace, the above noble lead (Ag-Pb alloy) is added to 1050
℃ ~ 1200 ℃, preferably heated to around 1100 ℃,
Air or oxygen-enriched air is blown into the metal phase through a lance for smelting.

As the oxidative smelting progresses, the lead content of the metal phase gradually decreases, and the amount of slag phase (PbO) increases. During this oxidative smelting, silica material such as silica sand (SiO ₂ ) is added to suppress the reactivity of silver and smelt in order to suppress the oxidation of the metal phase silver and transfer to the slag phase as much as possible. Good to do. The amount of silica sand added is SiO: to PbO: 2 mol.
An amount that provides a ratio of 1 molar ratio is suitable.

When the oxidative smelting is carried out in a single stage, when the lead content of the metal phase becomes several percent or less at the end of the oxidation reaction, the oxidation of silver rapidly progresses and the slag (PbO-SiO ₂ ) phase contains silver. The amount increases. The amount of such silver transferred to the slag phase (the amount of loss)
In order to minimize the above, it is advisable to perform noble lead oxidation and smelting in two stages.

First, the slag phase is separated by performing the first-stage oxidation smelting until the lead content of the metal phase becomes 5% to 10%. When the content of lead in the metal phase is less than 5%, the oxidation of silver rapidly progresses and the amount of silver loss increases, which is not preferable.
If the lead content of the metal phase is about 5%, the amount of silver oxide contained in the slag phase can be suppressed to about 0.5% or less. On the other hand, when the lead content of the metal phase is more than 10%, the effect of separating lead and silver decreases. Since most of the slag is lead oxide, the separated slag can be used as a lead smelting raw material.

Next, the second-stage oxidation smelting is performed on the remaining metal phase from which the slag phase has been separated. This oxidation smelting is performed until the lead content of the metal phase becomes 0.1% or less, and the slag phase is separated. Silver remains in the metal phase from which the slag phase has been separated, without being oxidized, and crude silver can be recovered. By casting this crude silver on the anode and performing electrolytic refining, high-purity electrosilver having a purity level of 99.99% can be obtained.
Since the separated slag contains about 2 to 10% of silver oxide, the slag is returned to the first stage of the smelting for reuse and reused, and the smelting for oxidation is repeated. The content of silver oxide contained in the slag of this second-stage oxidation smelt is higher than that of the slag phase of the first oxidation smelt, but the amount of slag produced is small, and it is used by returning it to the first oxidation smelt. It does not result in a loss of silver. As shown in Example 2, the silver in the slag is significantly reduced by repeating the second-stage slag in the first-stage oxidative smelting and blowing nitrogen for a short time before blowing oxygen. You can

[0019]

EXAMPLES The present invention will be specifically described below with reference to examples. The results of Examples and Comparative Examples are shown in Table 1.

[Example 1] 13 kg of a silver lead-containing slag (Ag: 14.6%, Pb: 52.8%) obtained by wet-chlorinating decoppered slime was charged into a smelting furnace, and 600 g of coke powder was added thereto. 7560 g of sodium carbonate was added, and reduction and smelting was performed by heating and holding at 1100 ° C. for 60 minutes. The produced slag was separated to recover 9060 g of metal (noble lead). Further, this metal was put into an oxidation furnace, 980 g of silica sand was added, and 110 L while blowing 3 L / min of oxygen-enriched air (80% oxygen) through a lance.
It heated at 0 degreeC and performed the 1st stage oxidation smelting for 200 minutes.
The slag generated here is separated to leave metal 2010g, 15g of silica sand is added again to this, and the second stage oxidation smelting is performed by blowing 3 L / min of oxygen-enriched air through a lance and heating to 1100 ° C. It was The generated slag was separated to recover 1880 g of metal (crude silver). The lead content of the metal was 0.062%. The silver content of the slag of the first stage oxidation smelting was 0.21%. The silver content of the slag of the second stage oxidation smelting is 5.22%, but the slag amount is 110
It was g.

[Example 2] 13 kg of the same silver lead-containing powder (Ag: 15.2%, Pb: 49.1%) as in Example 1 was charged into a smelting furnace, to which 700 g of coke powder and 6930 g of sodium carbonate were added. Then, it was heated and held at 1100 ° C. for 60 minutes for smelting. The produced slag was separated to recover 8270 g of metal (noble lead). Then, put this metal in an oxidation furnace and add quartz sand 880.
g and add oxygen-enriched air (80% oxygen) through lance 3
While blowing L / min, it was heated to 1100 ° C. and the first-stage oxidation smelting was performed for 180 minutes. The slag generated here was separated to leave 2110 g of metal, and 20 g of silica sand was again added to this.
Was added and the mixture was heated to 1100 ° C. while blowing 3 L / min of oxygen-enriched air through the lance to perform second-stage oxidation smelting. Generated slag is separated and metal (crude silver) 1940
g was recovered. The lead content of the metal was 0.049%. The separated second stage slag is 140g, 7.14%
Contains silver. When this was repeated in the next first-stage oxidation smelting and nitrogen was blown for the first 30 minutes, the silver content in the slag was reduced to 0.35%.

Comparative Example 1 13 kg of the same silver lead content (Ag: 14.6%, Pb: 52.8%) as in Example 1 was charged into a smelting furnace, to which 8890 g of sodium carbonate and 995 g of silica sand were added. 1
Smelting was performed by heating and holding at 100 ° C. for 60 minutes. The produced slag was separated and 1430 g of metal (crude silver) was recovered. The lead content in the recovered metal was 1.14%. On the other hand, the amount of separated slag is 12560 g, which is 3.77.
% Silver.

Comparative Example 2 13 kg of the same silver-lead containing silver (Ag: 15.2%, Pb: 49.1%) as in Example 2 was charged into a smelting furnace, to which 700 g of coke powder and 8150 g of sodium carbonate were added. And held at 1100 ° C. for 60 minutes for smelting. The generated slag was separated and 8190 g of metal (noble lead) was recovered. Then, put this metal in an oxidation furnace and add quartz sand 880.
g and add oxygen-enriched air (80% oxygen) through lance 3
The mixture was heated to 1100 ° C. while blowing L / min to carry out oxidation smelting for 240 minutes. The produced slag was separated to recover 1790 g of metal (crude silver). The lead content of the metal was 0.13%. On the other hand, the amount of slag was 6310 g, and the silver content was 2.83%.

[0024]

[Table 1]

[0025]

According to the recovery method of the present invention, high-grade silver can be efficiently separated from lead in a silver lead-containing slag obtained by wet chlorination of copper electrolytic slime and recovered.

[Brief description of drawings]

FIG. 1 is a process diagram showing an outline of a recovery method of the present invention.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Keiichi Sekiguchi             1-279 Kitabukuro-cho, Saitama City, Saitama Prefecture             Mitsubishi Materials Corporation Research Institute Omiya Lab             Research Center F-term (reference) 4K001 AA01 AA20 BA12 BA17 DA05                       EA03 EA04 EA07 HA01 KA13

Claims (7)

[Claims] 1. A reducing material and a slag forming material are added to a silver lead-containing slag, and reduction smelting is performed to convert the silver contained in the metal phase into noble lead, and the metal phase is enriched with air or oxygen after separating the slag. A method for recovering silver from a silver-lead-containing slag, characterized by recovering crude silver in a metal phase by blowing air and oxidizing and smelting lead to slag. 2. The silver recovery method according to claim 1, wherein a silver lead-containing slag obtained by subjecting copper electrolytic slime to a wet chlorination treatment is used. 3. Oxidation smelting of noble lead is carried out in two steps, firstly oxidization smelting of the first step is carried out until the lead content of the metal phase becomes 5% to 10%, and then the slag phase is separated. The silver recovery method according to claim 1 or 2, wherein the slag phase is separated by performing the second-stage oxidative smelting until the lead content of the metal phase becomes 0.1% or less. 4. The silver recovery method according to claim 3, wherein the slag separated by the second-stage oxidation melting is returned to the first-stage oxidation melting and the oxidation melting is repeated. 5. In the reduction smelting, carbon powder is used as a reducing material, and the addition amount of carbon powder is 2 to 4 times the reaction equivalent of lead contained in the silver lead-containing slag. The silver lead recovery method described in. 6. In reduction smelting, sodium carbonate is used as a slag forming material, and the addition amount of sodium carbonate is 1.2 to 2.0 times the total reaction equivalent of silver and lead contained in the silver lead-containing slag. The silver recovery method according to claim 1. 7. The silver recovery method according to claim 1, wherein a silica material is added to carry out oxidation smelting.