JP2006307283A - Method for recovering noble metal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for recovering noble metals where noble metals can be efficiently recovered and recycled from a noble metal-containing disposal material disposed of from various fields. <P>SOLUTION: In the method for recovering noble metals, flux is added to a noble metal-containing disposal material and a silver-containing disposal material, so as to be mixed and melted in a melting furnace, so as to be separated into glassy slag and metal, thereafter, the separated metal is transferred to an oxidizing furnace, flux is added in the oxidizing furnace, oxidation treatment is performed, so as to be separated into oxide slag and a noble metal-containing silver alloy, the separated noble metal-containing silver alloy is, if required, subjected to compositional regulation, is cast, and is thereafter subjected to silver electrolysis, so as to be electrodeposited silver, the silver is recovered, and the noble metals are subjected to wet treatment, so as to be stepwise recovered from electrolytic sludge. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for recovering a noble metal capable of efficiently recovering and recycling the noble metal from a waste material containing the noble metal discarded from various fields.

  Waste materials containing precious metals are in various fields, and some of them are listed, for example, waste substrates, waste catalysts, precious metal product waste, precious metal plating waste liquid, precious metal-containing blast powder, etc. It covers a wide variety such as solid, film, and liquid.

As a typical method for recovering precious metals from these waste materials, there is a wet method that has been used in, for example, mines. In this wet method, waste materials are pretreated as necessary, such as firing, pulverization, sieving, chemical reduction, etc., then dissolved in aqua regia or nitric acid, etc. It is a method of recovering each noble metal component by recovering as metallic copper.
On the other hand, in Patent Documents 1 to 8, as a dry process, a waste catalyst containing a white metal-containing substance is melted together with metal copper or copper oxide in a furnace to transfer the platinum group into the molten copper metal, and obtained. A method has been proposed in which a molten copper metal containing platinum group is oxidized under conditions that oxidize copper to some extent, and phase separation is performed between molten oxides such as nickel, iron and indium and molten metal enriched with platinum group elements. ing.
JP 2000-248322 A JP 2004-68071 A JP 2004-269936 A JP 2004-270008 A JP 2004-275866 A JP 2004-277791 A JP 2004-277792 A JP-A-2005-54201

However, in the wet method, since copper is preferentially recovered, the subsequent precious metals, particularly the platinum group, are poorly recovered, and a large amount of acid must be used. It was not practical.
In contrast, the dry methods described in Patent Documents 1 to 8 have advantages that the recovery rate is higher than that of the wet method and that the platinum group can be recovered at a lower cost than the wet method. There were the following problems to be solved.
In this dry method, the obtained molten copper metal is mostly copper, and the amount of white metal is only a very small amount of about 1% or less, and after first recovering copper by an electrolytic method, Since white metal is recovered, it is the same as the wet method in that copper is preferentially recovered. The electrolytic method for separating copper (copper electrolysis) has a copper alloy with a content of 99% or more. There is a problem that the electric cost and the chemical cost are very high and the processing speed is slow. And since collection | recovery of a white metal becomes a subsequent process, generally the cost was very huge.

  Therefore, an object of the present invention is to propose a method for recovering a noble metal that solves the problems of the conventional processing method and can efficiently recover and recycle the noble metal from various waste materials.

The present invention has been proposed in view of the above, and after adding flux to precious metal-containing waste material and silver-containing waste material, mixing and melting in a melting furnace to separate into glassy slag and metal, the separated metal Is transferred to an oxidation furnace, flux is added in the oxidation furnace, and oxidation treatment is performed to separate the oxide slag and the noble metal-containing silver alloy, and the composition of the separated noble metal-containing silver alloy is adjusted as necessary. Then, the present invention relates to a method for recovering noble metal, characterized in that silver electrolysis is performed to recover silver as electrodeposited silver, and the noble metal is wet-treated from electrolytic sludge and recovered stepwise.
That is, the method for recovering a noble metal of the present invention includes:
(1) adding flux to noble metal-containing waste material and silver-containing waste material, mixing and melting in a melting furnace, and separating into vitreous slag and metal;
(2) transferring the separated metal to an oxidation furnace, adding a flux, oxidizing in the oxidation furnace and separating it into oxide slag and a noble metal-containing silver alloy;
(3) a step of adjusting the composition of the separated noble metal-containing silver alloy as necessary and casting;
(4) a step of recovering silver as electrodeposited silver by subjecting the noble metal-containing silver alloy after casting to silver electrolysis;
(5) including a step of wet-treating noble metal from electrolytic sludge and recovering it stepwise.

  Moreover, in the said noble metal collection | recovery method, the silver containing waste material proposes the method characterized by being the silver obtained by the photosensitive material recycling process.

  Furthermore, in the method for recovering precious metals, a method is also proposed in which the precious metal-containing waste material is a powder obtained by separating low-grade precious metal-containing waste material or the like by flotation.

  Moreover, in the said noble metal collection | recovery method, the noble metal containing silver alloy taken out from the oxidation furnace, Ag and a noble metal are 80 to 95%, The base metal containing Cu is 5 to 20%, The method characterized by the above-mentioned. I also propose.

  Further, the present invention includes a step of recovering silver by silver electrolysis of a noble metal-containing silver alloy of 40 to 94% Ag-base metal containing 40 to 94% Cu and 1 to 30% noble metal. A collection method is also proposed.

The recovery method of the noble metal of the present invention is a production cost as compared with the conventional wet method, because various precious metals are absorbed and recovered by silver contained in the silver-containing waste material, for example, silver obtained by the photosensitive material recycling process. Can be kept low, and the processing speed is also increased.
Moreover, since silver is circulated and used, the melting point is lower than that of the dry method in which copper is circulated such as in Patent Documents 1 to 8, and precious metals can be easily taken up. In particular, there is an influence of viscosity, so that noble metals are easily solidified. Moreover, it is possible to circulate the introduction of the silver material, and it is possible to reduce the net addition amount of silver. It also leads to curbing silver consumption. Furthermore, silver electrolysis does not have to be carried out at a high content like copper electrolysis, and has the advantages of low electrical and chemical costs and high processing speed.

  In the case of using precious metal-containing waste materials such as low-grade precious metal-containing waste materials separated by flotation, it is possible to selectively concentrate precious metals, mainly precious metals. Even extremely low-grade waste materials, which were difficult, can be primarily concentrated by flotation as pretreatment. Further, by collecting and concentrating a plurality of low-grade waste materials by selecting a flotation reagent, recovery of noble metals is promoted.

  When the noble metal-containing silver alloy taken out from the oxidation furnace is 80 to 95% of Ag and noble metal, and the base metal containing Cu is 5 to 20%, silver to be added with noble metal containing or not containing silver and Can be separated as electrodeposited silver and slime during silver electrolysis, and can be purified respectively. Moreover, as a specific composition before electrolysis, it does not need to exist with high purity centering on crude silver, and it can concentrate as a solid solution.

  Silver is contained in the noble metal recovery method including the step of recovering silver by silver electrolysis of a noble metal-containing silver alloy of 40 to 94% -Cu containing a base metal of 5 to 40% -noble metal of 1 to 30% of the present invention. Or if it is a solid solution alloy of the noble metal which does not contain silver, and the silver to introduce | transduce, it can isolate | separate as an electrodeposition silver and a slime at the time of silver electrolysis, and can refine | purify, respectively. In addition, the specific composition before electrolysis does not need to be present with high purity centering on crude silver, and the efficiency of silver electrolysis can be increased by concentrating as a solid solution.

Each step constituting the noble metal recovery method of the present invention will be described.
(1) A step of adding flux to precious metal-containing waste material and silver-containing waste material, mixing and melting in a melting furnace, and separating into vitreous slag and metal;
The noble metal-containing waste material indicates, for example, incineration ash such as a waste substrate, a waste catalyst, a noble metal product waste, a noble metal plating waste liquid, and may partially contain organic matter.
In addition, as precious metal-containing waste materials, some precious metal product scraps, buffs, and leuters can be applied as jewelry-related transition items from the current (wet) treatment, and removed crowns, gypsum, asbestos, etc. Waste substrate, automobile / petrochemical waste catalyst, electronic substrate manufacturing process waste, waste electronic parts, paste / plating (adsorption resin), sandblasting powder, etc. can be applied.
In addition, low-grade precious metal-containing waste materials such as waste substrates such as electronic substrates can be pulverized and subjected to flotation, and this precious metal-containing waste material can also be used.
Flotation is often performed for the purpose of selecting resources from minerals, and is generally used to separate minerals based on hydrophobicity and hydrophilicity, which are one of the surface properties of mineral particles. Defined as law. That is, hydrophobic minerals are not easily wetted by water, but exhibit floating properties because their surfaces have affinity with gas or oily substances. On the other hand, hydrophilic minerals are easily wetted by water, so they remain in the water phase and do not float easily. By applying this, not only the surface properties inherent in minerals but also various flotation reagents are used to artificially control the original hydrophobicity or hydrophilicity of the mineral particle surface to control its floatability. Change them to separate each other. A particularly useful foam flotation method is to generate or introduce a large number of fine bubbles after adding a suitable flotation reagent to the suspension of pulverized fine particles and adjusting the surface properties of the fine particles. Hydrophobic fine particles can be attached to the surface, floated and separated and recovered. As equipment to carry out these flotation, there are already Fahrenwald type flotation machines (FW type, Denver Sub-A type flotation machines), Fegergren type flotation machines, Agiteya type flotation machines, Worman type flotation machines Various types of flotation beneficiators are commercially available.
The silver-containing waste material generally refers to silver, silver product waste, etc. obtained from a film, a fixing solution, or waste generated in the manufacturing process by a sensitive material recycling process. If silver is contained in the noble metal-containing waste material, it is not necessary to add a silver-containing waste material separately. That is, the noble metal-containing waste material and the silver-containing waste material may be a kind of waste material.
As the flux, silica, calcium oxide, calcium carbonate, borax or the like can be used.

  These precious metal-containing waste materials and silver-containing waste materials are provided with a silver-noble metal alloy having a specific composition in the step (4) to be described later, and in order to electrolyze the silver-noble metal alloy, the treatment ratio is adjusted in advance. It is desirable to keep it. That is, it is desirable to sample each waste material and subject it to elemental analysis to adjust the amount of addition to the melting furnace. Specifically, it is desirable to mix so that the ratio of silver and noble metal is about 6: 4.

In the melting furnace, when the flux is added to the precious metal-containing waste material and the silver-containing waste material, and mixed and melted at 1200 to 1700 ° C., it is separated into glassy slag and metal due to the difference in specific gravity. The metal contains silver, noble metals such as gold, platinum, palladium and rhodium, and base metals such as copper and lead. Further, the vitreous slag contains other components, for example, vitreous components such as NaO and SiO ₂ . This glassy slag is removed.

(2) The step of transferring the metal to the oxidation furnace and adding the flux, and oxidizing it in the oxidation furnace to separate it into oxide slag and noble metal-containing silver alloy;
In this step, the metal separated in the step (1) is transferred to an oxidation furnace, and flux is added to oxidize the metal. The difference from the oxidation process in the dry method in which copper is circulated in Patent Documents 1 to 8 and the like is that the conventional dry method does not oxidize copper (oxidizes copper to some extent), and is a metal that is baser than copper. In the present invention, the oxidation treatment is performed under conditions that do not oxidize silver, and the metal that is lower than silver is oxidized and removed. By removing it by oxidation, a large amount of copper can be separated as an oxide.
The oxidation furnace is, for example, tiltable and can be heated at 1300 to 1600 ° C., and can be oxidized by introducing air (oxygen-containing gas) into the furnace or molten metal. The inside base metal becomes oxide slag and is separated from the noble metal-containing silver alloy which is not oxidized. In this case, the oxide slag is separated so as to be located above the inside of the furnace, and the noble metal-containing silver alloy is located below (bottom) inside the furnace. This noble metal-containing silver alloy contains copper (a small amount) in addition to silver and the noble metal alloy. The oxide slag contains oxides such as iron, nickel, copper (a large amount), chromium, tin, lead, and zinc. In this step, the noble metal-containing silver alloy taken out from the oxidation furnace is oxidized and separated so that Ag and noble metal are 80 to 95% and base metal containing Cu is 5 to 20%.

(3) A step of adjusting the composition of the separated noble metal-containing silver alloy as necessary and casting;
In this step, in order to facilitate silver electrolysis in the subsequent step (4), the composition is adjusted, for example, by adding silver as necessary, and the composition ratio is 5 to 40 base metals containing Ag 40 to 94% -Cu. % —Adjust so that it is 1-30% of the noble metal. Thereafter, an electrode plate (alloy anode plate) used in the next (4) electrolysis step is cast from the alloy whose composition has been adjusted.

(4) The step of recovering silver by silver electrolysis of the noble metal-containing silver alloy after casting In order to silver electrolyze the noble metal-containing silver alloy separated in the above-mentioned step (2), the above-mentioned step (3) Using the obtained electrode plate (alloy anode plate), silver nitrate is used as the electrolyte, and the silver concentration is 20 g / L or more, preferably 60 g / L. The bath voltage is 1-3V, preferably 2.5V. The cathode current density is 200 to 300 A / m ² , preferably 270 A / m ² . Further, the temperature of the electrolytic solution can be normal temperature.
As described above, the silver noble metal alloy supplied to the silver electrolysis in this step is adjusted so that the base metal containing Ag is 40 to 94% -Cu containing 5 to 40% and the noble metal is 1 to 30%. In the case of silver electrolysis, noble metal is not electrodeposited on the cathode, and silver can be recovered with high purity and high electrical efficiency. When deviating from this range, electrolysis is performed immediately after energization, but the electrolytic sludge adheres to the anode, hinders electrolysis, reduces electrolysis efficiency, and prevents electricity from flowing. In addition, electrodeposition of other metals and noble metals is likely to occur on the cathode, resulting in poor electrolytic efficiency of silver recovery.

(5) A step of wet-treating precious metal from electrolytic sludge and recovering it step by step;
After separating and purifying only silver in the step (4) described above, the electrolytic sludge contains noble metals such as gold, platinum, palladium and rhodium. In order to recover the precious metal from these electrolytic sludges, the precious metal is recovered stepwise by wet treatment.

The oxide slag separated in the step (2) has been described as containing iron oxide, nickel oxide, copper oxide, chromium oxide, etc. Precious metals are also included. Therefore, in order to collect | recover copper, a trace amount silver, and a noble metal from this oxide slag, it processes in a reduction furnace. That is, the oxide slag is transferred to a reducing furnace, and flux and a carbonaceous reducing agent are added to perform smelting reduction. Coke is preferably used as the carbonaceous reducing agent.
By this reduction treatment, the copper oxide in the oxide slag is reduced to metallic copper, and silver and noble metals also accumulate in the lower part (bottom part) of the furnace in the same manner as this metallic copper. On the other hand, iron oxide, nickel oxide, chromium oxide and the like are hardly reduced, so that they remain as oxide slag and are separated by being located above the furnace.
The separated copper and noble metal-containing silver alloy is recovered as metal copper by copper electrolysis, and the residue is wet-treated with the electrolytic sludge in the step (4) to recover the noble metal step by step.

In the example shown in FIG. 1, two types of noble metal-containing waste materials were used, and one of them (noble metal-containing waste material 2) was subjected to flotation.
These noble metal-containing waste materials 1 and 2 and silver-containing waste material were melted at 1200 to 1700 ° C. by adding flux in a melting furnace, and separated into vitreous slag and metal. The vitreous slag was removed, the metal was transferred to an oxidation furnace, added with flux, and oxidized by introducing air or the like at 1300 to 1600 ° C., and separated into oxide slag and a noble metal-containing silver alloy.
The separated noble metal-containing silver alloy was adjusted in composition as necessary, and was cast and formed into an electrode plate used in the subsequent silver electrolysis. Silver electrolysis was performed using this electrode plate, and silver was taken out as electrodeposited silver.
On the other hand, the separated oxidized slag was transferred to a reduction furnace, subjected to reduction treatment, separated into a large amount of copper components and slag, and then subjected to copper electrolysis to take out copper.
And the electrolytic sludge collect | recovered from the above-mentioned silver electrolysis and copper electrolysis is combined, and a noble metal is wet-processed and collect | recovered in steps.

[Selection of precious metals from low-grade precious metal-containing waste materials by flotation]
After the firing and pulverization treatment, a flotation treatment was performed on the dental waste material having a particle size that passed through a sieve of 60 mesh (aperture 250 μm). Regarding the dental waste material, first, a slurry having a pulp concentration of 10% was prepared in a condition layer. Next, the slurry being stirred was subjected to sulfurization treatment with sodium hydrosulfide. After sufficient stirring, the pH was adjusted to 2 or less. Thereafter, 50 mg / l of a collecting agent (potassium n-amylxanthate (KAX)) was added using a flotation machine. Further, a small amount of a foaming agent (4-methyl-2-pentanol (MIBC)) was added.
When the floss and the sink were collected under the above conditions and the precious metal was analyzed, the recovery rate of the precious metal in the obtained floss (recovered material) was 88.2%, and the precious metal quality was changed from 0.15% to 2.39. % Could be concentrated. The floss (recovered material) in which the precious metal is concentrated is subjected to an acid dissolution treatment, and the sink in which a trace amount of the precious metal (11.8%) remains is subjected to a refining treatment after filtration and drying.

表１より明らかなように、酸化処理当初に比べて明らかに銀及び貴金属が濃縮され、ニッケル、インジウム、鉄は消失し、銅も含有量が著しく低下した。 [Oxidation treatment and separation]
Table 1 shows an example in which silver and noble metals are concentrated as metals and base metals such as copper are separated by oxidation treatment in an oxidation furnace.

As apparent from Table 1, silver and noble metals were clearly concentrated as compared with the beginning of the oxidation treatment, nickel, indium and iron disappeared, and the content of copper was remarkably reduced.

[First step]
After firing 100 kg of noble metal-containing (and silver-containing) waste material to remove organic substances, 30 kg of incinerated ash (including metal) is added to flux components (Na ₂ BO ₄ O ₇ .10H ₂ O: Na ₂ CO ₃ = 6). : 4) 13.8 kg was mixed and melted at 1350 ° C. in a melting furnace.
When the metal and the glassy slag were separated and the obtained metal was analyzed by fluorescent X-ray, the alloy was 4% noble metal, 10% Ag, and 86% other than that.

[Second step]
Thereafter, 20 kg of the separated metal is transferred to an oxidation furnace, and 5 kg of flux (CaO: Na ₂ CO ₃ : Na ₂ BO ₄ O ₇ .10H ₂ O = 1.5: 1: 1) is charged and oxidized at 1350 ° C. It processed and isolate | separated and isolate | separated into the noble metal containing silver alloy (precious metal 0.8Kg / Ag2Kg / Cu containing base metal 1.2Kg) and oxide slag (21Kg).

[Third step]
Thereafter, the obtained silver-containing machine metal alloy (Ag 50% —base metal 30% containing Cu—noble metal 20%) was cast into an alloy without segregation in a melting furnace, and used in the next silver electrolysis step ( Alloy anode plate) was prepared.

[Fourth step]
7 L of silver nitrate (60 g / L) as an electrolytic solution is placed in an electrolytic cell having a length of 340 mm, a width of 120 mm, and a depth of 200 mm, and an alloy having a width of 50 mm, a length of 120 mm, and a thickness of 7 mm manufactured in the third step. Two pieces of an anode and a cathode with a SUS plate width of 50 mm × length of 120 mm × thickness of 2 mm were introduced so that the distance between the electrodes was 100 mm.
The bath voltage was fixed at 2.5 V, and the cathode current density was applied for 7 hours in the range of 250 to 300 A / m ^2. As a result, noble metals were concentrated in the electrolytic sludge without mixing noble metals in the electrodeposited silver. Recovered in a state.

[Fifth step]
The electrolytic sludge obtained in the third step was dissolved in aqua regia, silver was filtered off, and Au, Pt and Pd were recovered stepwise from the filtrate.

[Comparative example of the fourth step]
7L of silver nitrate (60g / L) as an electrolytic solution is placed in an electrolytic cell of length 340mm x width 120mm x depth 200mm, and the width is 50mm x length 120mm x produced by Ag35% -Cu35% -noble metal 30% alloy. Two pieces of an alloy anode having a thickness of 7 mm and a cathode having a width of SUS plate of 50 mm × length of 120 mm × thickness of 2 mm were introduced so that the distance between the electrodes was 100 mm.
The bath voltage was fixed at 2.5 V and the cathode current density was applied for 7 hours in the range of 250 to 300 A / m ^2. As a result, the electrolytic sludge fixed to the alloy anode, the current density decreased to 50 A / m ² , Electrodeposition has become difficult.

  Precious metals can be efficiently recovered and recycled from precious metal-containing waste materials discarded from various fields.

It is a flowchart which shows an example of the collection | recovery method of the noble metal of this invention.

Claims (5)

  Flux is added to the precious metal-containing waste material and silver-containing waste material, mixed and melted in a melting furnace to separate into glassy slag and metal, and then the separated metal is transferred to an oxidation furnace, and the flux is applied in the oxidation furnace. In addition, it is oxidized to separate it into oxide slag and a noble metal-containing silver alloy. The composition of the separated noble metal-containing silver alloy is adjusted as necessary. After casting, silver is electrolyzed to form silver as electrodeposited silver. A method for recovering a noble metal, characterized in that the noble metal is recovered by a wet process from electrolytic sludge and recovered stepwise.   The method for recovering a noble metal according to claim 1, wherein the silver-containing waste material is silver obtained by a light-sensitive material recycling process.   The method for recovering a noble metal according to claim 1 or 2, wherein the noble metal-containing waste material is a powder separated by flotation.   2. The method for recovering a noble metal according to claim 1, wherein the noble metal-containing silver alloy taken out from the oxidation furnace contains 80 to 95% of Ag and noble metal and 5 to 20% of a base metal containing Cu.   A method for recovering a noble metal, comprising a step of recovering silver by silver electrolysis of a noble metal-containing silver alloy of Ag 40 to 94% -base metal containing Cu 40 to 94% -noble metal 1 to 30%.

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