JP2009155678A - Method for recovering noble metal, and recovered noble metal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for economically recovering a noble metal from noble metal-containing waste or the like with high efficiency. <P>SOLUTION: Disclosed is a method for recovering a noble metal where a noble metal-containing material is cleaned with molten metal tin, so as to form a tin-noble metal alloy, thus the tin-noble metal alloy is separated and recovered. Preferably, the remaining noble metal-containing material is heated together with a tin compound, a reducing agent and flux, the noble metal is eluted by the reduction melting, further, the noble metal is absorbed into the produced metal tin melted layer, the melted metal layer comprising the noble metal is separated from an oxide layer, so as to be recovered, the recovered tin-noble metal alloy is electrolytically refined, so as to recover the noble metal, and further, the reduction melting is performed in the two stages of strong reduction and weak reduction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for recovering noble metals economically and efficiently from wastes containing noble metals such as gold, platinum and palladium.

  As an exhaust gas purification catalyst for automobiles, an alumina support layer is formed on a heat-resistant support and a noble metal such as Pt, Pd, Rh is supported on the support layer is widely known. Electronic substrates, lead frames, etc. Noble metals are widely used as conductive materials in electronic device parts. In addition, noble metals such as gold, platinum and palladium are widely used as petrochemical catalysts.

  Conventionally, noble metals are recovered from these used catalysts (referred to as catalyst waste), and wet recovery methods and dry recovery methods are known. As a wet recovery method, a method of dissolving catalyst waste in an acid and leaching a noble metal is known (Patent Document 1). As a dry recovery method, catalyst waste containing platinum group metal is heated with copper or copper oxide, flux, reducing agent to absorb platinum group metal in molten metal copper, and then the molten metal copper is partially oxidized. Then, by forming a copper oxide layer, the platinum group metal is concentrated in the metal copper, the copper oxide is separated, and the metal copper containing the platinum group metal is recovered (Patent Document 2). , 3, 4). Moreover, it replaces with metallic copper and the method of heating a catalyst waste with iron and making a precious metal absorb in iron is also known.

The conventional wet recovery method has a low extraction rate of noble metals in acid leaching, and the post-treatment of the leaching residue is troublesome. On the other hand, in the conventional dry recovery method, those using metal copper as an absorbent as a precious metal recovery means are sufficiently recovered because some of the platinum group such as ruthenium Ru has a low solubility in copper of about 10%. Difficult to do. Those using molten iron as a noble metal absorber have problems that the solubility of the noble metal is low and the melting temperature is high.
Japanese Patent Laid-Open No. 02-138424 Japanese Patent Laid-Open No. 04-317423 Japanese Patent Laid-Open No. 04-318128 JP 07-216467 A

  The present invention solves the above problems in the conventional dry recovery method, and uses metal tin as an absorbent instead of metal copper, metal lead, etc., and economically absorbs noble metal in molten metal tin. Provide an efficient collection method. In the method of the present invention, gold, silver and platinum group metals are referred to as noble metals.

The present invention relates to a noble metal recovery method and the like that have solved the above-described problems with the following technical configuration.
[1] A noble metal recovery method comprising washing a noble metal-containing material with molten metal tin to form a tin noble metal alloy, and separating and recovering the tin noble metal alloy.
[2] The noble metal recovery method of [1], wherein the recovered tin precious metal alloy is electrolytically purified to recover the precious metal.
[3] When a noble metal-containing material is washed with molten metal tin to form a tin noble metal alloy, the noble metal-containing material remaining without forming the alloy is heated together with a tin compound, a reducing agent, and a flux. A precious metal recovery method characterized by elution of a precious metal by melting and absorption of the precious metal into a generated molten metal tin layer, and separating and recovering the molten metal layer containing the precious metal from the oxide layer.
[4] Reducing and melting the residual noble metal-containing material in two steps, strong reduction and weak reduction, to form slag with little tin oxide and noble metal by strong reduction, and then iron content contained in the molten metal layer into slag by weak reduction The precious metal recovery method described in [3] above, wherein the molten metal layer that has been expelled to improve the quality of the precious metal is recovered.
[5] The noble metal recovery method according to any one of [1] to [4] above, wherein the noble metal-containing material is a catalyst waste or electronic equipment material waste containing a noble metal.
[6] The noble metal recovery method according to any one of [1] to [5] above, wherein the tin compound is metal tin, a tin alloy, tin oxide, or a tin compound other than these.
[7] A noble metal recovery method for separating a noble metal from a noble metal-containing molten metal recovered by the method described in any one of [1] to [6] above.
[8] From the noble metal-containing metal tin recovered by the method described in any one of [1] to [7] above or from the noble metal-containing metal tin recovered by the method according to any one of claims 1 to 7 Isolated precious metal.

  The noble metal recovery method of the present invention is a method using metal tin as a noble metal absorber, and noble metals such as gold, platinum, palladium, ruthenium and the like all have sufficient solubility in metal tin. By adding a reducing agent or flux together with the tin compound and heating to reduce and melt, the metal tin melt layer can be formed and the melted noble metal can be sufficiently absorbed by the metal tin and efficiently recovered. Specifically, for example, ruthenium dissolves only about several percent in copper but dissolves in tin up to about 20%, so that ruthenium can be efficiently recovered.

  The noble metal recovery method of the present invention is capable of recovering the noble metal by separating the tin noble metal alloy by washing the catalyst waste or the like with molten metal tin before the reduction melting, separating the tin noble metal alloy, Since the precious metal-containing material remaining without forming the tin precious metal alloy is reduced and melted to recover the precious metal, the burden of reductive melting is reduced and the precious metal can be recovered efficiently.

  Furthermore, the precious metal recovery method of the present invention forms slag with a low content of tin oxide and precious metal in strong reduction by carrying out reductive melting in two stages of strong reduction and weak reduction, thereby reducing the burden of weak reduction. As a result, a high-quality metal layer can be formed and the precious metal can be efficiently recovered.

  The noble metal recovery method of the present invention can be widely applied to materials containing noble metals such as catalyst waste and electronic equipment material waste. In addition to metal tin, tin oxide, tin alloys or other tin compounds can be used as an absorbent together with a reducing agent, so that it can be easily implemented, and metal tin, tin oxide, tin alloys, etc. Because it is possible to use the scrap of, it is excellent in economic efficiency.

Hereinafter, the present invention will be specifically described based on embodiments. In addition, unless otherwise indicated,% is the mass%.

The noble metal recovery method of the present invention is a noble metal recovery method characterized in that a noble metal containing material is washed with molten metal tin to form a tin noble metal alloy, and the tin noble metal alloy is separated and recovered. The precious metal-containing material remaining without being heated is heated together with a tin compound, a reducing agent, and a flux to elute the precious metal by this reductive melting and to absorb the precious metal in the formed metal tin molten layer. It is a noble metal recovery method characterized in that a molten metal layer contained is separated and recovered from an oxide layer.

  As the noble metal-containing material, catalyst waste containing noble metal, electronic device material waste, or the like can be used. Catalyst waste containing precious metals includes automobile exhaust gas purification catalysts and petrochemical catalysts. For example, automobile exhaust gas purification catalysts generally contain about 1000 ppm of Pt, 600 to 700 ppm of Pd, and 100 to 200 ppm of Rh, and petrochemical catalysts contain about 4000 ppm of Pt and about 2% of Ru. ing. In addition, waste such as electrodes and paste contains several thousand ppm of Pt, Ru, Ir and the like. The recovery method of the present invention can be widely applied to these various precious metal-containing materials.

  In the precious metal recovery method of the present invention, as a first step [washing step], precious metal-containing materials such as catalyst waste are washed with molten metal tin. This cleaning method is, for example, (i) charging metal tin and catalyst waste into a melting furnace, heating the metal tin above the melting point of metal tin to melt the metal tin, and stirring the catalyst waste etc. in the molten metal tin (Ii) A method in which a metal tin bath is formed in advance, and a catalyst waste or the like is put into the bath and stirred and washed, or (iii) molten metal tin is poured into the catalyst waste or the like in a shower to wash it. Various cleaning methods can be applied, such as the method of Molten metal tin is heated and kept in a molten state so as not to solidify during liquid feeding or processing.

  By washing the noble metal-containing material with molten metal tin, the noble metal contained in the catalyst waste or the like dissolves in the metal tin to form a tin noble metal alloy. The tin noble metal alloy is separated and recovered. This cleaning treatment reduces the burden of reductive melting in the next process, reduces loss of precious metals in the reductive melting process, and improves yield.

  The produced tin noble metal alloy has a large specific gravity, so that it accumulates at the bottom of the melting furnace, and a noble metal-containing material (catalyst waste, etc.) that is not consumed for alloy formation remains on the upper side. A tin noble metal alloy is extracted from the bottom of the melting furnace. The extracted tin precious metal alloy can recover the precious metal by electrolytic purification.

  For the precious metal-containing material remaining without forming the tin precious metal alloy in the cleaning process with molten metal tin, as a second stage (reduction process), the residual precious metal-containing material is heated together with the tin compound, the reducing agent, and the flux. Perform reduction melting. The noble metal is eluted by this reductive melting, and the eluted noble metal is absorbed in the produced metal tin molten layer. Molten metal tin serves as a precious metal absorber.

  As the tin compound, metal tin, tin alloy, tin oxide, or other tin compounds can be used. If a tin alloy, tin oxide, or a tin compound other than these is heated and melted together with a reducing agent, the tin component is reduced and a molten layer of metal tin is formed, so not only metal tin but also tin alloys, tin oxide, etc. These tin compounds can be used.

  The tin compound is used in an amount that sufficiently absorbs the precious metal contained in the precious metal-containing waste. Specifically, as described above, the precious metal contained in the catalyst for chemical industry and the catalyst for automobiles is about 2.5% at most, so the amount of precious metal-containing waste remaining in the melting furnace is 10 to 10%. A 15% amount of tin compound may be used.

  The noble metal-containing material is added with a reducing agent together with a tin compound and placed in a closed melting furnace, preferably a flux is added together with the reducing agent, and heated to a temperature at which these raw materials are melted for reduction melting. A carbon material such as coke may be used as the reducing agent. The amount of coke used is an amount that sufficiently reduces the noble metal-containing material. Specifically, for example, the amount may be about 5 to 10% with respect to the amount of the catalyst for chemical industry or the catalyst for automobile.

  Silica sand, calcium carbonate, iron oxide or the like may be used as the flux. Addition of flux lowers the melting temperature of noble metal-containing materials and tin compounds, and promotes slag formation. The amount of the flux may be about 200 to 300% with respect to the amount of the precious metal-containing material to be processed (chemical industry catalyst or automobile catalyst). The heating temperature is a temperature at which the noble metal-containing material and the tin compound are melted. For example, the melting is performed by heating to 1300 ° C to 1500 ° C.

  By heating with a reducing agent, metallic tin is melted, or the tin compound is reduced and metallic tin is eluted to form a molten metal tin layer (molten metal layer). Further, the noble metal contained in the catalyst waste or the like is reduced and eluted, and absorbed by the molten metal layer. On the other hand, tin oxide and other oxides (slag) produced by heating and melting have a specific gravity smaller than that of the molten metal, and form a slag layer on the molten metal layer. The eluted noble metal hardly transfers to the slag layer and is absorbed by the lower molten metal layer.

  Preferably, the reductive melting is performed in two stages, strong reduction and weak reduction. In strong reduction, the amount of coke of the reducing agent is appropriately 5 to 10% with respect to the noble metal-containing material. By this strong reduction, slag having a small content of tin dioxide and noble metal is formed. For example, a slag having a tin oxide content of 1 wt% or less and a noble metal content of 100 ppm or less can be formed.

  Weak reduction after strong reduction. For example, when the slag analysis value becomes Sn 1% or less, the slag in the furnace is discharged and the process proceeds to weak reduction. In weak reduction, the amount of coke of the reducing agent is suitably 0 to 2% with respect to the noble metal-containing material. In addition, when using the arc furnace using a carbon electrode, since carbon of an electrode is consumed, even if the amount of coke used is zero, weak reduction may be possible.

  Due to the weak reduction, iron in the molten metal is removed by the slag, so that generation of a hard head is suppressed. The metal tin molten layer (molten metal layer) that has absorbed the precious metal contains iron components derived from the raw material catalyst waste, etc., and iron easily forms an alloy with tin. It forms a so-called tin-iron alloy. Weak reduction is performed to remove this iron from the metal layer to the slag layer to improve the noble metal quality of the metal layer. Moreover, metal impurities other than iron are also removed by slag by weak reduction.

  When weak reduction is performed from the beginning in order to drive out (remove) iron from the molten metal layer, tin and noble metal absorbed in the slag layer increase, and these losses increase. If the iron is removed to the slag by weak reduction after the strong reduction is first performed and the noble metal and tin are sufficiently metallized, the loss of the noble metal and tin absorbed in the first slag is small. Moreover, since the iron content in the metal is driven out by weak reduction, it is possible to recover the metal having a high precious metal quality.

  Since the specific gravity of slag is lighter than that of metal, a slag layer is formed above the molten metal layer. Therefore, the melting furnace is tilted to pour out the upper slag layer, or the slag is discharged from the tap hole using the hydrostatic pressure while the melting furnace is installed, and separated from the molten metal tin layer.

  After separating and removing the slag layer, air is blown into the molten metal tin layer, or an oxidizing agent is added to form a tin oxide layer, and this tin oxide layer is separated and removed to reduce the capacity of the molten metal tin layer. The concentration of the noble metal contained in the molten metal tin layer can be relatively increased. Moreover, the base component contained in molten metal tin is slag-ized and removed by oxidizing molten metal tin.

  The slag layer separated from the molten tin layer can be reused by returning to the heating and melting step. By reusing slag, the precious metal accompanying the slag is inevitably absorbed by the molten metal tin, and the recovery rate can be increased.

  After the slag layer is separated and removed, the molten metal tin layer is recovered. The molten metal tin absorbs the noble metal eluted from the catalyst waste. The recovered and cooled noble metal-containing metal tin has a structure in which noble metal crystals are interspersed between metal tin crystals or a structure composed of crystals in which noble metals and tin are alloyed. The contained noble metal can be separated from the metallic tin by a method such as electrolytic purification or acid dissolution.

[Example 1]
In a metal tin bath (metal tin 1500 kg, temperature 400 ° C.), 1000 kg of chemical industrial catalyst waste (Ru content 2%) was added and stirred for 4 hours for washing. The tin noble metal alloy collected at the bottom of the container was recovered. The recovered amounts and components of this tin noble metal alloy are shown in Table 1.

[Example 2]
The catalyst waste remaining in the container in Example 1 was charged into a closed melting furnace together with 120 kg of metallic tin, added with 60 kg of reducing agent coke and 2500 kg of flux, and heated at 1400 ° C. for 6 hours for strong reduction. The entire charge was melted. In addition, the silica flux, calcium carbonate, and iron oxide were mixed and used for the flux respectively. Subsequently, after removing the produced | generated slag layer, 5 kg of cokes were further added, and it reduced at 1400 degreeC by heating for 6 hours. After this reduction, 120 kg of metal was recovered. The recovered metal components are shown in Table 1.

Example 3
A tin precious metal alloy was recovered in the same manner as in Example 1 except that 1000 kg of catalyst waste for automobile exhaust gas purification (Pt content 1.0%) was used instead of catalyst waste for chemical industry and 1500 kg of metal tin was used. . The recovered amounts and components of this tin noble metal alloy are shown in Table 1.

Example 4
The catalyst waste remaining in the container in Example 3 was charged into a closed melting furnace together with 65 kg of a tin alloy (90 wt% tin, 10 wt% iron), and strong reduction and weak reduction were performed in the same manner as in Example 2. After this reduction, 60 kg of metal was recovered. The recovered metal components are shown in Table 1.

Claims (8)

A precious metal recovery method comprising: cleaning a precious metal-containing material with molten metal tin to form a tin precious metal alloy, and separating and recovering the tin precious metal alloy.
The noble metal recovery method according to claim 1, wherein the recovered tin noble metal alloy is electrolytically purified to recover the noble metal.
When the precious metal content is washed with molten metal tin to form a tin precious metal alloy, the precious metal content remaining without forming the alloy is heated together with the tin compound, the reducing agent, and the flux. The precious metal recovery method is characterized in that the precious metal is absorbed in the molten metal tin layer formed and the molten metal layer containing the precious metal is separated from the oxide layer and recovered.
Reducing and melting the residual noble metal-containing material in two stages, strong reduction and weak reduction, to form slag with a small amount of tin oxide and noble metal by strong reduction, and then expelling iron contained in the molten metal layer into slag by weak reduction and precious metal The precious metal recovery method according to claim 3, wherein the molten metal layer with improved quality is recovered.
The noble metal recovery method according to any one of claims 1 to 4, wherein the noble metal-containing material is a catalyst waste or an electronic equipment material waste containing a noble metal.
The precious metal recovery method according to any one of claims 1 to 5, wherein the tin compound is metal tin, a tin alloy, tin oxide, or a tin compound other than these.
A noble metal recovery method for separating a noble metal from a noble metal-containing molten metal recovered by the method according to any one of claims 1 to 6.
A noble metal-containing metal tin recovered by the method according to any one of claims 1 to 7, or a noble metal separated from the noble metal-containing metal tin recovered by a method according to any one of claims 1 to 7.