WO2021117385A1 - Method and device for recovering catalytic metal from aqueous solution including catalytic metal coprecipitated with tin - Google Patents

Abstract

The present invention addresses the problem of providing a method for recovering a catalytic metal from an aqueous solution which contains a catalytic metal which is coprecipitated with tin, said method being characterized by including: the separation of a tin coprecipitate by filtering said aqueous solution at a point in time at which the concentration of the catalytic metal which has been eluted into said aqueous solution is no more than 8 mg/L; and thereafter, the separation and recovery of the catalytic metal from the separated tin coprecipitate. As a result, it is possible to efficiently recover a catalytic metal (precious metal) in rinse water. The present invention is useful in the field of recycling for recovering valuable metals from wastewater that contains valuable metals and was discharged in an electroless plating process.

Description

Method and device for recovering catalyst metal from aqueous solution containing catalyst metal coprecipitated with tin

The present invention relates to a method and a recovery device for recovering a catalyst metal from an aqueous solution containing a catalyst metal coprecipitated with tin.

When electroless plating is performed on the surface of plastic, glass, etc., it is necessary to support the catalyst metal on the surface to be plated as a pretreatment, and palladium (Pd), which is a noble metal, is selected as the catalyst metal. It is common to be done. Further, as a method of supporting the metal, a method is adopted in which the object to be plated is immersed in a catalyst solution in which a catalyst metal salt and stannous chloride are mixed, and the catalyst metal is precipitated on the surface to be plated by the reducing power of tin (Sn). ing.

After the object to be plated is immersed in the catalyst solution to support the catalyst metal, the excess catalyst solution is washed by immersing it in cleaning water (mainly pure water). The washing water after washing contains hydrochloric acid in addition to palladium chloride and tin chloride (or a complex thereof) as main components, although it depends on the type of catalyst metal. The hydrochloric acid concentration is 0.005 mol / L or less.

By the way, since the used catalyst solution and the washing water after washing contain an expensive catalyst metal (precious metal), it is necessary to recover it. Usually, the used catalyst liquid is outsourced to a recovery company as it is, and then the precious metal is recovered, or a precious metal recovery device is installed in the factory to collect the recovered product on which the precious metal is adsorbed. It is outsourced to a contractor for collection.

By the way, by diluting the catalyst solution in the washing water about 100 times, the pH of the catalyst solution (pH <1) rises to 2 to 3, tin in the catalyst solution precipitates, and in the precipitate. The catalyst metal also co-precipitates. Since the catalyst metal is expensive, it is required to recover the catalyst metal in the cleaning liquid as well as the catalyst liquid.

The following techniques are known as a method for recovering the catalyst metal in the washing water. For example, Patent Document 1 describes a method in which a tin precipitate containing a catalyst metal in washing water is solid-liquid separated by a method such as centrifugation, and the precipitate is dissolved and recovered with hydrochloric acid / hydrogen peroxide solution. ..
Patent Document 2 describes a method in which a tin precipitate containing a catalyst metal in washing water is filtered using a porous filter, and the precipitate separated by backwash is decomposed into hydrochloric acid / hydrogen peroxide solution and recovered. ing.
In Patent Documents 3 and 4, an acid is added to the washing water to adjust the pH to 0.8 to 5 mol / L to suppress the formation of tin precipitate, the pore radius is 1 nm or less, and the pore volume is 45 to 500 mm ³ /. A method of passing the liquid through activated carbon which is g and recovering the liquid is described.

Japanese Unexamined Patent Publication No. 2001-303148 Patent No. 6236311 JP-A-2017-133109 Japanese Unexamined Patent Publication No. 2017-133110

An object of the present invention is to provide a method for recovering a catalyst metal from an aqueous solution containing a catalyst metal such as palladium coprecipitated with tin with a high recovery rate.

In order to solve the above problems, the method for recovering the catalyst metal according to the embodiment of the present invention is a method for recovering the catalyst metal from an aqueous solution containing a catalyst metal co-precipitated with tin (tin co-precipitate). When the concentration of the catalytic metal eluted in the aqueous solution is 8 mg / L or less, the aqueous solution is filtered to separate the tin co-precipitate, and then the catalytic metal is recovered from the separated tin co-precipitate. To do.

According to the present invention, it is possible to recover a catalyst metal (precious metal) such as palladium in the washing water, which has been conventionally discarded. In particular, it has an excellent effect that it is possible to provide a method for separating the catalyst metal from an aqueous solution containing a catalyst metal such as palladium coprecipitated with tin with a high recovery rate.

It is a schematic diagram of the recovery device which concerns on this embodiment.

In the electroless plating step, the object to be plated is immersed in a catalyst solution in which a catalyst metal salt and stannous chloride are mixed to support the catalyst metal on the surface to be plated. Precious metals Au (gold), Ag (silver), Pt (platinum), Pd (palladium), Rh (rhodium), Ir (iridium), Ru (lutenium), Os (osmium) are used as catalyst metals. In particular, Pd is mainly used. After that, the object to be plated on which the catalyst metal is supported is immersed in washing water made of pure water or the like, and the excess catalyst liquid is washed. The cleaning water after cleaning contains a catalyst metal which is a noble metal, and since the catalyst metal is expensive, it is required to recover the catalyst metal in the cleaning water.

By the way, the catalyst metal is co-precipitated with tin in the washing water, but the present inventor left the washing water containing the catalyst solution (catalyst metal: Pd) overnight, and the color of the washing water changed. I noticed that it changed from light brown to transparent. Then, when the Pd concentration in the washing water was measured, it was confirmed that the Pd concentration was remarkably high. From this, the present inventor has found that catalyst metals such as Pd coprecipitated with tin are ionized and eluted with the passage of time.

Based on these findings, the present embodiment is a catalyst in an aqueous solution containing a catalytic metal coprecipitated with tin (tin coprecipitate) when the concentration of the catalytic metal eluted in the aqueous solution is 8 mg / L or less. It is characterized in that a tin coprecipitate containing a metal is filtered and separated, and a catalytic metal is recovered from the separated tin coprecipitate. As described above, by filtering the aqueous solution to separate the tin co-precipitate before the catalyst metal is ionized and eluted from the tin co-precipitate, the recovery loss due to the elution of the catalyst metal can be reduced. Has an effect.

The start of elution (ionization) of the catalytic metal varies depending on various factors such as pH and liquid temperature. For example, elution starts after about 24 hours, or elution starts after about 16 days. Although there are some that can be confirmed, what is important here is the relationship between the storage time (period) of the aqueous solution (washing water) in which tin and the catalytic metal are co-precipitated and the concentration of the catalytic metal eluted in the aqueous solution in advance. When the concentration of the eluted catalytic metal is below a specific concentration, the aqueous solution is passed through a filter to be filtered. As a result, the loss of the catalyst metal dissolving in the aqueous solution can be reduced, and the recovery efficiency can be improved. It is preferable to filter when the concentration of the catalyst metal eluted in the aqueous solution is 8 mg / L or less, more preferably 2 mg / L or less. This makes it possible to increase the recovery efficiency to 50% or more.

The tin coprecipitate is preferably filtered using a filter with an opening of 10 μm or less. Since the tin coprecipitate has a fine particle size, if the opening of the filter exceeds 10 μm, the tin coprecipitate may pass through the filter and cannot be sufficiently filtered. More preferably, a filter having an opening of 1 μm or less is used. Further, the liquid passing speed of the filtration filter is preferably 100 L / min or less. Since the tin coprecipitate has a small specific gravity, if the liquid passing speed exceeds 100 L / min, the tin coprecipitate may pass through the filter and cannot be sufficiently filtered.

Then, as a method of separating and recovering the catalytic metal from the filtered tin co-precipitate, for example, the separated tin co-precipitate is calcined together with the filtration filter to reduce the volume, and then hydrochloric acid, a hydrogen peroxide solution, and /. Alternatively, Sn and Pd (catalyst metal) can be dissolved with aqua regia, and the dissolved Pd can be reduced with iron powder or a chemical to recover the precipitated Pd metal. Alternatively, the separated tin coprecipitate is re-injected into an aqueous solution in which the adsorbent such as an ion exchange resin or a chelate resin is installed and held for a certain period of time to allow the catalyst metal to be eluted into the aqueous solution at any time. It can be recovered with an adsorbent.

As a specific recovery device, as shown in FIG. 1, a stock tank (washing water raw water tank) for storing an aqueous solution (washing water) in which tin and a catalyst metal are co-settled and a tin co-sink are filtered and separated. A recovery device including a filter tank (filter housing) provided with a filter for the purpose and a pump for feeding liquid from the stock tank to the filter tank can be used.

Examples of the present invention will be described. It should be noted that the following examples are merely representative examples, and the present invention need not be limited to these examples and should be interpreted within the scope of the technical idea described in the specification. It is a thing.

(Example 1)
An aqueous solution in which tin and palladium are co-precipitated (Pd: 11 mg / L, Sn: 1350 mg / L, pH: 2 to 3) is maintained at a liquid temperature of about 18 ° C. to 23 ° C. The Sn concentration was measured. As a result, as shown in Table 1, the concentration of Pd in the aqueous solution gradually increased after the retention period was 24 hours. Then, after about 48 hours had passed, Pd was almost eluted. Since the target can be achieved if the recovery rate is 50% or more, it can be seen that it is preferable to filter the tin coprecipitate from the aqueous solution before 36 hours.

(Example 2)
An aqueous solution in which tin and palladium are co-precipitated (Pd: 17 mg / L, Sn: 580 mg / L, pH: 2 to 3) is maintained at a liquid temperature of about 18 ° C. to 23 ° C. The Sn concentration was measured. As a result, as shown in Table 1, the concentration of Pd in the aqueous solution gradually increased after the retention period was 16 days. Then, after about 30 days had passed, Pd was almost eluted. Since the target can be achieved if the recovery rate is 50% or more, it can be seen that it is preferable to filter the tin coprecipitate from the aqueous solution before 20 days.

According to the present invention, according to the present invention, it is possible to recover a catalyst metal (precious metal) such as palladium in the washing water, which has been conventionally discarded. In particular, it has an excellent effect of being able to provide a method for separating the catalyst metal from an aqueous solution containing a catalyst metal such as palladium coprecipitated with tin with a high recovery rate. The present invention is useful in the field of recycling in which the valuable metal is recovered from the wastewater containing the valuable metal discharged in the electroless plating process.

1 Stock tank (washing water raw water tank)
2 Liquid feed pump (magnet pump)
3 Flowmeter 4 Filter (filter element)
5 Filter tank (filter housing)

Claims (7)

A method of recovering a catalytic metal from an aqueous solution containing a catalytic metal co-precipitated with tin. When the concentration of the catalytic metal eluted in the aqueous solution is 8 mg / L or less, the aqueous solution is filtered and co-precipitated with tin. A method for recovering a catalyst metal from a catalyst metal-containing aqueous solution, which comprises separating an object and then recovering the catalyst metal from the separated tin co-precipitate. The method for recovering a catalyst metal from a catalyst metal-containing aqueous solution according to claim 1, wherein the filtration is performed using a filter having a mesh size of 10 μm or less. The method for recovering a catalyst metal from a catalyst metal-containing aqueous solution according to claim 2, wherein the liquid passing speed of the filter is 100 L / min or less. The catalyst according to any one of claims 1 to 3, wherein the separated tin co-precipitate is dissolved in hydrochloric acid, hydrogen peroxide solution, or / and aqua regia to separate and recover the catalyst metal. A method for recovering a catalytic metal from a metal-containing aqueous solution. The catalyst metal-containing aqueous solution according to any one of claims 1 to 3, wherein the separated tin co-precipitate is placed in an aqueous solution, held, and the catalytic metal to be eluted is separated and recovered by an adsorbent. Method of recovering catalytic metal from. The method for recovering a catalyst metal from an aqueous solution containing a catalyst metal according to any one of claims 1 to 5, wherein the catalyst metal is a noble metal. A recovery device for carrying out the method for recovering a catalyst metal from a catalyst metal-containing aqueous solution according to any one of claims 1 to 6, for storing an aqueous solution in which tin and the catalyst metal are co-precipitated. From a catalyst metal-containing aqueous solution, which comprises a stock tank, a filter tank for filtering and separating tin co-deposits, and a pump for passing the aqueous solution from the stock tank to the filter tank. Catalytic metal recovery device.

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