JP2009155677A - Method for recovering noble metal, and recovered noble metal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for economically recovering noble metal-containing waste or the like with high efficiency. <P>SOLUTION: In the method where a noble metal-containing material is heated and melted 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, and the molten metal layer comprising the noble metal is separated from an oxide layer, so as to be recovered, the reduction melting is performed in the two stages of strong reduction and weak reduction, slag comprising reduced tin oxide and noble metal is formed by the strong reduction, and next, iron comprised in the melted metal layer is removed into the slag by the weak reduction, thus the melted metal layer having an increased noble metal grade is recovered. <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). In addition, a method is also known in which catalyst waste is heated together with iron or lead to absorb noble metal in iron lead instead of metallic copper.

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 part of the platinum group such as ruthenium Ru has a low solubility in copper of less than 1%. 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-containing material is heated and melted together with a tin compound, a reducing agent, and a flux, the noble metal is eluted by this reduction melting, and the eluted noble metal is absorbed into the metal tin molten layer, and the molten metal layer containing the noble metal In the method of separating and recovering from the oxide layer, the reduction melting is carried out in two stages, strong reduction and weak reduction, to form slag containing little tin oxide and noble metal by strong reduction, and then the iron content contained in the molten metal layer. A method for recovering a noble metal, characterized by recovering a molten metal layer having a high quality by removing slag by weak reduction.
[2] In the strong reduction, the reducing coke is reduced and melted using 5 to 10% of the precious metal content, and the reducing coke is reduced and melted using 0 to 2% of the reducing agent as a weak reduction. The precious metal recovery method according to [1].
[3] The precious metal recovery method according to any one of [1] or [2] above, wherein the precious metal-containing material is a catalyst waste containing precious metal or a waste of electronic equipment material.
[4] The precious metal recovery method according to any one of [1] to [3], wherein the tin compound is metal tin, a tin alloy, tin oxide, or a tin compound other than these.
[5] A noble metal recovery method for separating noble metal from noble metal-containing metal tin recovered by the method described in any one of [1] to [4] above.
[6] Noble metal-containing metal tin recovered by the method described in any one of [1] to [5] above, or noble metal-containing metal recovered by the method described in any of [1] to [5] above Precious metal separated from tin.

  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. A metal tin melt layer can be formed by adding a reducing agent or flux together with the tin compound and heating to reduce and melt, and the eluted noble metal can be sufficiently absorbed by the metal tin melt layer 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 performs reductive melting in two stages of strong reduction and weak reduction, and forms a large amount of slag with a small content of tin oxide and noble metal in the strong reduction, so that the slag is discharged out of the furnace. As a result, the burden of weak reduction can be reduced, and loss of precious metals when removing the iron content of impurities into a small amount of slag in weak reduction can be reduced.

  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 precious metal recovery method of the present invention heats and melts a precious metal-containing material together with a tin compound, a reducing agent, and a flux, and elutes the precious metal by this reductive melting, absorbs the precious metal eluted into the metal tin melt layer, and removes the precious metal. In the method of separating and recovering the molten metal layer contained from the oxide layer, the reduction melting is carried out in two steps, strong reduction and weak reduction, to form a slag containing little tin oxide and noble metal by strong reduction, and then molten metal It is a noble metal recovery method characterized by recovering a molten metal layer in which the iron content contained in the layer is removed to slag by weak reduction to improve the quality of the noble metal.

  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.

  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 chemical industry catalyst and the automobile catalyst is about 2.5% at most, so that the amount of tin is 10-30% of the amount of precious metal-containing waste. A 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 to reduce and melt. A carbon material such as coke may be used as the reducing agent. The amount of coke used is an amount corresponding to strong reduction and weak reduction.

  Silica sand, calcium carbonate, iron oxide or the like may be used as the flux. Addition of the flux lowers the melting temperature of the mixture of the noble metal-containing material and the tin compound, and promotes the generation of slag. The amount of the flux may be about 200 to 300% of the amount of the catalyst for chemical industry or the catalyst for automobile. 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 to 1500 ° C.

  By heating with the reducing agent, the metallic tin is melted, or the tin compound is reduced and the metallic tin is eluted to form a molten metallic tin layer. Further, the noble metal contained in the catalyst waste is reduced and eluted, and is absorbed by the generated molten metal tin. 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 tin layer. The eluted noble metal hardly transfers to the slag layer and is absorbed by the lower molten metal tin layer.

  The method of the present invention performs two-stage reduction, strong reduction and weak reduction, in the reduction melting. 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, a weak reduction may be possible even if the amount of coke used is zero.

  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 expel (remove) the iron content of the molten metal layer to the slag, tin and noble metal absorbed in the slag layer increase, and the amount of loss increases. In the method of the present invention, the strong reduction is first performed to sufficiently advance the metallization of the noble metal and tin, and after further discharging the slag, the iron content is removed to the slag by weak reduction. The amount of tin is small, and these loss amounts can be suppressed. Moreover, since the iron content in the metal is driven out into the slag by weak reduction, the burden of refining the metal recovered after the weak reduction is greatly reduced.

  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]
1000 kg of catalyst waste for chemical industry (Ru content 2%) is charged into a closed melting furnace together with 120 kg of metal tin, 60 kg of reducing agent coke and 2500 kg of flux are added and heated at 1400 ° C. for 6 hours. Strong reduction was performed to melt the entire charge. 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, 140 kg of metal was recovered. The recovered metal components are shown in Table 1.

[Example 2]
According to the conditions shown in Table 1 except that 150 kg of tin oxide was used instead of metal tin, 140 kg of metal was recovered in the same manner as in Example 1. The recovered metal components are shown in Table 1.

Example 3
Other than using 1000g of catalyst waste for automobile exhaust gas purification (Pt content 1.0%) instead of catalyst waste for chemical industry, and using 100kg of tin alloy (90wt% tin, 10wt% iron) instead of metallic tin In accordance with the conditions shown in Table 1, 99 kg of metal was recovered in the same manner as in Example 1. The recovered metal components are shown in Table 1.

Example 4
According to the conditions shown in Table 1, 140 kg of metal was recovered in the same manner as in Example 1 except that 1000 kg of electronic device material waste (Pd content 2%) was used instead of chemical industrial catalyst waste. The recovered metal components are shown in Table 1.

[Comparative Example 1]
According to the conditions shown in Table 1, except for using 100 kg of metal copper instead of metal tin, 102 kg of metal was recovered in the same manner as in Example 1. The recovered metal components are shown in Table 1.
As shown in Table 1, in Examples 1 to 4 of the present invention, the amount of noble metal (Ru, Pt, Pd) contained in the recovered metal tin was the amount of noble metal (Ru, P) contained in the recovered metal copper of Comparative Example 1. Noble metal can be efficiently recovered. Furthermore, the iron content in the recovered metal tin of Examples 1 to 4 is 1% to 2%, and the iron content is remarkably small.

Claims (6)

A precious metal-containing material is heated and melted together with a tin compound, a reducing agent, and a flux, and the precious metal is eluted by this reductive melting, and the eluted precious metal is absorbed into the metal tin molten layer, and the molten metal layer containing the precious metal is oxidized. In the method of separating and recovering from the layer, the reduction melting is performed in two steps, strong reduction and weak reduction, to form slag with little tin oxide and noble metal by strong reduction, and then the iron content in the molten metal layer is weakly reduced A method for recovering a noble metal, comprising: recovering a molten metal layer that has been removed by slag to improve the quality of the noble metal.
In the strong reduction, the reducing agent coke is reduced and melted using 5 to 10% of the precious metal-containing material, and the reducing agent is reduced and melted using 0 to 2% of the reducing agent coke as weak reduction. The precious metal recovery method to be described.
The method for recovering a noble metal according to claim 1 or 2, wherein the noble metal-containing material is a catalyst waste containing an noble metal or an electronic equipment material waste.
The precious metal recovery method according to any one of claims 1 to 3, 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 noble metal from noble metal-containing metal tin recovered by the method according to any one of claims 1 to 4.
A noble metal-containing metal tin recovered by the method according to any one of claims 1 to 5, or a noble metal separated from the noble metal-containing metal tin recovered by a method according to any one of claims 1 to 5.