JP6401814B2 - Method for recovering precious metal from hydrochloric acid acidic Sn-containing precious metal catalyst recovery liquid - Google Patents

Description

  The present invention relates to a method for recovering a noble metal from a hydrochloric acid acidic Sn-containing noble metal catalyst recovery liquid.

When a copper film is formed by electroless copper plating on a non-conductive surface such as plastic or glass, and on the inner surface of a printed wiring board through hole or blind via hole made of a non-conductive material, a catalytic metal that becomes the initial precipitation nucleus of copper deposition Must be uniformly adsorbed on the surface to be plated. It is desirable to select a noble metal as a catalyst because of its metal properties such as catalytic activity and oxidation resistance, and palladium (Pd) is generally widely used as a catalyst from the economical aspect. As a method for precipitating such Pd, a method widely used for a long time is a mixture of water-soluble salt palladium chloride (PdCl ₂ ) and water-soluble salt stannous chloride (SnCl ₂ ). There is a method of immersing a non-conductive substrate, which is an object to be plated, in a catalyst solution, and depositing Pd ions as Pd metal on the surface by utilizing the reducing power of stannous ions. In such a method, a hydrochloric acid acidic Sn-containing noble metal catalyst recovery liquid is recovered as a waste liquid.

  Examples thereof include a method for recovering a noble metal from such a hydrochloric acid Sn-containing noble metal catalyst recovery solution. For example, the method of patent documents 1-3 is mentioned.

  Patent Document 1 discloses palladium that precipitates palladium together with a hydroxide of tin and separates it from the acidic solution of hydrochloric acid by increasing the pH of the acidic solution of hydrochloric acid containing palladium ions stabilized by divalent ions of tin. The separation method is described.

  Patent Document 2 discloses a method of concentrating a precipitate made of palladium and tin by centrifuging a wastewater containing a precipitate made of palladium and tin, and then dissolving the precipitate in the concentrated solution, and then using a reducing agent to make palladium. A method for recovering palladium characterized by depositing a metal is described.

In Patent Document 3, the catalyst metal colloid is concentrated as a precipitate on a porous metal filter, and then the precipitate is removed from the porous metal filter by backwashing the precipitate with a fluid. A method of recovering the catalytic metal from the fluid comprising: solubilizing the precipitate with an HCl / H ₂ O ₂ mixture to form a solution, and then recovering the catalytic metal from the solution. Has been.

Japanese Patent Laid-Open No. 2001-131552 JP 2003-147448 A JP 2003-247029 A

  According to Patent Document 1, it is disclosed that palladium can be efficiently recovered without being affected by coexisting copper ions and the like.

  However, according to studies by the present inventors, the method described in Patent Document 1 has an overwhelmingly large amount of Pd to Sn (Pd / Sn) of 1/50 or less. It is necessary to precipitate Sn as a hydroxide and collect it at the same time, and since the load in the subsequent dissolution process and the separation and purification process of Pd is high, the productivity is low, which is industrially disadvantageous.

  Further, according to Patent Document 2, it is disclosed that palladium can be recovered economically and efficiently from wastewater containing dilute palladium precipitates, such as washing wastewater discharged from the palladium nucleus imparting step, which has been disposed of in the past. Has been.

  However, according to the study by the present inventors, the method described in Patent Document 2 precipitates Sn, which is overwhelmingly present with respect to Pd, as a hydroxide at the same time as the method described in Patent Document 1. It is the starting point to recover and recover, and the productivity is low, which is industrially disadvantageous.

  Patent Document 3 discloses that a method for recovering a catalytic metal from a fluid containing a catalytic metal colloid is provided.

  However, according to the study by the present inventors, the method described in Patent Document 3 uses a large amount of chemicals in backwashing, and further increases the load in the wastewater treatment process. It can be said that.

  This invention is made | formed in view of this situation, Comprising: From the hydrochloric acid acidic Sn containing noble metal catalyst recovery liquid, providing the noble metal recovery method which can collect | recover a noble metal efficiently by a simple method. Objective.

  In the method of selectively adsorbing noble metal on activated carbon by bringing the aqueous solution containing the hydrochloric acid acidic Sn-containing noble metal catalyst recovery solution into contact with activated carbon, and recovering the noble metal, the present inventors added to the aqueous solution in contact with activated carbon. The effects of the precious metal recovery rate due to the compounds to be investigated were examined. As a result, the present inventors have found that the recovery rate of the noble metal varies depending on the type of compound to be added.

  Therefore, the present inventors have found that the above object can be achieved by the present invention described below by variously examining the types of compounds added to the aqueous solution brought into contact with the activated carbon.

The method for recovering a noble metal according to one aspect of the present invention is a method for recovering a noble metal from a hydrochloric acid acidic Sn-containing noble metal catalyst recovery liquid by activated carbon adsorption. An organic compound having a carboxy group in a molecule is added to an aqueous solution containing the recovery liquid. An addition step of preparing a post-addition solution to which the organic compound has been added, and adding the post-addition solution to a zeta potential in a 10 mmol / L sodium tetraborate aqueous solution and 0.01 mmol / L Passing step of passing through an activated carbon layer containing activated carbon having an absolute value of a difference from a zeta potential in an aqueous sodium acid solution of 0 to 25 mV and a pore volume of 1 nm or less in pore diameter of 45 to 500 mm ³ / g And a step of separating the activated carbon layer from the post-addition liquid that has passed through the activated carbon.

  According to such a configuration, in a method of recovering a noble metal by bringing an aqueous solution containing a hydrochloric acid acidic Sn-containing noble metal catalyst recovery solution into contact with activated carbon, an organic compound having a carboxy group in the molecule in the aqueous solution to be treated. The recovery rate of precious metals can be increased simply by adding. Moreover, the precious metal adsorbed on the activated carbon contained in the activated carbon layer is allowed to pass through the activated carbon layer after the addition of the organic compound added liquid through the activated carbon layer. Does not easily desorb from activated carbon. Also from this, the recovery rate of the noble metal can be increased.

  From these things, according to said structure, the collection | recovery method of a noble metal which can collect | recover a noble metal efficiently by a simple method from the aqueous solution containing hydrochloric acid acidic Sn containing noble metal catalyst collection liquid can be provided. .

  In the noble metal recovery method, the organic compound is preferably a carboxylic acid having 6 or less carbon atoms.

  According to such a configuration, a higher recovery rate of the noble metal can be realized. That is, it is possible to provide a method for recovering a noble metal more efficiently from an aqueous solution containing a hydrochloric acid acidic Sn-containing noble metal catalyst recovery solution by a simple method.

  Moreover, in the said noble metal collection | recovery method, the said collection | recovery liquid contains metals other than the said noble metal, The said addition process WHEREIN: Content of the said organic compound with respect to the said other metal in the said aqueous solution is molar ratio. The organic compound is preferably added in a step of 0.3 to 5 times.

  According to such a configuration, a higher recovery rate of the noble metal can be realized. That is, it is possible to provide a method for recovering a noble metal more efficiently from an aqueous solution containing a hydrochloric acid acidic Sn-containing noble metal catalyst recovery solution by a simple method.

  In the noble metal recovery method, the noble metal is preferably palladium.

  According to such a configuration, palladium used as a plating catalyst can be recovered as a noble metal, which is very significant.

  In the noble metal recovery method, the post-addition solution preferably has an acid concentration of less than 0.8 mol / L, and in the passing step, the noble metal and Sn are preferably separated and adsorbed on the activated carbon layer.

  According to the study by the present inventors, it has been found that when the acid concentration is high as the post-addition solution used in the passing step, the recovery rate of the noble metal is increased. On the other hand, even when the acid concentration of the solution after addition is in a relatively low state, by using the noble metal recovery method according to one embodiment of the present invention, that is, by adding the organic compound, High recovery rate can be realized. Therefore, even if the acid concentration is less than 0.8 mol / L, the high recovery rate of the noble metal can be realized without intentionally increasing the acid concentration. Note that, according to the method for recovering a noble metal according to one embodiment of the present invention, naturally, even if the acid concentration is relatively high, a high recovery rate of the noble metal can be realized.

  ADVANTAGE OF THE INVENTION According to this invention, the collection | recovery method of a noble metal which can collect | recover a noble metal efficiently with a simple method from hydrochloric acid acidic Sn containing noble metal catalyst recovery liquid can be provided.

FIG. 1 is a schematic diagram for explaining an example of a noble metal recovery method according to an embodiment of the present invention. FIG. 2 is an apparatus for evaluating a noble metal recovery method according to an embodiment of the present invention. FIG. 3 is a graph showing the relationship between the molar ratio of oxalic acid and Sn and the Pd recovery rate. FIG. 4 is a graph showing the relationship between the acid concentration and the zeta potential. FIG. 5 is a graph showing the relationship between the molar ratio of oxalic acid and Sn and the Pd recovery rate.

  Hereinafter, although the embodiment concerning the present invention is described, the present invention is not limited to these.

The method for recovering a noble metal according to an embodiment of the present invention is a method for recovering a noble metal from an acidic Sn-containing noble metal catalyst recovery liquid by activated carbon adsorption. In this recovery method, an addition step of preparing a post-addition solution in which the organic compound is added by adding an organic compound having a carboxy group in the molecule to the aqueous solution containing the recovery solution; And a step of passing through an activated carbon layer containing predetermined activated carbon (passing step) and a step of separating the activated carbon layer from the post-addition liquid that has passed through the activated carbon (separation step). The activated carbon contained in the activated carbon layer used in the passing step is the absolute value of the difference between the zeta potential in the 10 mmol / L sodium tetraborate aqueous solution and the zeta potential in the 0.01 mmol / L sodium tetraborate aqueous solution. Is 0 to 25 mV, and the pore volume with a pore radius of 1 nm or less is 45 to 500 mm ³ / g. The hydrochloric acid Sn-containing noble metal catalyst recovery liquid is an aqueous solution used in the passing step in the recovery method according to the present embodiment, and is an hydrochloric acid acidic recovery liquid that is an aqueous solution containing tin and a noble metal. . For example, a hydrochloric acid acidic solution after being used in a nucleation step of electroless plating with an aqueous solution containing a tin compound and a noble metal compound, a washing waste solution discharged in the washing step, and the like.

  According to such a method, an organic compound having a carboxy group in the molecule in the aqueous solution to be treated is obtained by bringing the aqueous solution containing the acidic Sn-containing noble metal catalyst recovery solution into contact with activated carbon to recover the noble metal. The recovery rate of precious metals can be increased simply by adding. Therefore, according to said method, a noble metal can be efficiently collect | recovered by an easy method from the aqueous solution containing hydrochloric acid acidic Sn containing noble metal catalyst collection | recovery liquid. Moreover, the precious metal adsorbed on the activated carbon contained in the activated carbon layer is allowed to pass through the activated carbon layer after the addition of the organic compound added liquid through the activated carbon layer. Does not easily desorb from activated carbon. Also from this, the recovery rate of the noble metal can be increased. From these things, the above collection methods can collect noble metals efficiently from an aqueous solution containing a hydrochloric acid acidic Sn-containing noble metal catalyst recovery solution by a simple method.

  The adding step in the recovery method according to the present embodiment is not particularly limited as long as an organic compound having a carboxy group in the molecule can be added to the aqueous solution containing the hydrochloric acid-containing Sn-containing noble metal catalyst recovery solution. Specific examples of the adding step include a step of adding the organic compound to the aqueous solution so that the organic compound has a concentration described later.

  The organic compound having a carboxy group in the molecule is not particularly limited as long as it is an organic compound having at least one carboxy group in the molecule. Moreover, the number of carboxy groups contained in the molecule of the organic compound may be one or more per molecule as described above, and preferably two or more. Examples of the organic compound having a carboxy group in the molecule include carboxylic acids such as dicarboxylic acids and hydroxy acids. The carboxylic acid preferably has 6 or less carbon atoms, more preferably 2 to 6 carbon atoms. Specific examples of organic compounds having a carboxy group in the molecule include formic acid, acetic acid, propionic acid, butyric acid, acrylic acid, maleic acid, glutaric acid, adipic acid, oxalic acid, malonic acid, succinic acid, and tartaric acid. , And citric acid. Among the exemplified compounds, formic acid, acetic acid, oxalic acid, tartaric acid, and citric acid are preferable as the organic compound, and formic acid, oxalic acid, tartaric acid, and citric acid are more preferable. Moreover, the said organic compound may be used individually by 1 type, and may be used in combination of 2 or more type. An organic compound having a carboxy group in the molecule may have at least one carboxyl group in the molecule, and has a hydroxyl group, an unsaturated bond, etc. in addition to the carboxyl group in the molecule. May be.

  The processing target in the recovery method according to the present embodiment is not particularly limited as long as it is an aqueous solution containing hydrochloric acid acidic Sn-containing noble metal catalyst recovery liquid. Even if the concentration of the noble metal is low, the recovery method according to this embodiment can be recovered at a high recovery rate. Specifically, the concentration of the noble metal in the aqueous solution is not particularly limited, but it is preferably 1000 mg / L or less from the viewpoint of efficient adsorption and recovery. That is, the concentration of the noble metal in the adjustment liquid is substantially the same as the concentration of the noble metal in the aqueous solution, and is preferably 1000 mg / L or less. Moreover, it is preferable that these noble metal concentrations are 0.1-1000 mg / L, It is more preferable that it is 0.1-500 mg / L, It is further more preferable that it is 0.1-100 mg / L. Moreover, although it can collect | recover even if there is much content of a noble metal, when trying to collect | recover fully, activated carbon may be required in large quantities. This is considered to be due to the fact that when the content of the noble metal is large, the pores of the activated carbon are blocked with the noble metal that rapidly adsorbs, and the saturated adsorption amount decreases.

  Moreover, it is preferable that the aqueous solution used for the passage process in the collection method according to the present embodiment is an aqueous solution containing a noble metal, further containing an inorganic acid, and having an acid concentration of less than 0.8 mol / L. According to the study by the present inventors, it has been found that when the aqueous solution supplied to the recovery step contains an inorganic acid and the acid concentration is high, the recovery rate of the noble metal is increased. On the other hand, even when the acid concentration of the aqueous solution is in a relatively low state, by using the noble metal recovery method according to the embodiment of the present invention, that is, by adding the organic compound, high recovery of the noble metal is achieved. Rate can be realized. Therefore, even if the acid concentration is less than 0.8 mol / L, the high recovery rate of the noble metal can be realized without intentionally increasing the acid concentration. In addition, according to the noble metal recovery method according to the embodiment of the present invention, naturally, even if the acid concentration is relatively high, a high recovery rate of the noble metal can be realized.

  Further, the aqueous solution containing the hydrochloric acid-containing Sn-containing noble metal catalyst recovery liquid may contain other metals, inorganic salts, organic substances, and the like in addition to the noble metal and tin (Sn). According to the recovery method according to the present embodiment, the noble metal can be efficiently adsorbed on the activated carbon even if components other than these noble metals are included. Moreover, even if base metals, such as iron, nickel, and copper, are mixed, a noble metal can be efficiently collect | recovered using the collection | recovery method concerning this embodiment. In addition to water, the aqueous solution containing the hydrochloric acid-containing Sn-containing noble metal catalyst recovery solution contains other solvents such as alcohols such as ethanol and isopropanol, and hydrophilic solvents such as ketones such as acetone. There is no problem.

  Specifically, the aqueous solution containing the hydrochloric acid acidic Sn-containing noble metal catalyst recovery solution is a used catalyst which is a washing waste liquid obtained by washing the object to be plated after being immersed in a plating catalyst imparting agent containing a noble metal. Examples include recovered liquid and rinse tank waste liquid. Such a washing waste liquid does not have a high concentration of noble metal, and has not been used so far for recovering noble metals. If it is the collection | recovery method which concerns on this embodiment, the noble metal to contain can be efficiently collect | recovered also from such a washing waste liquid.

  The noble metal is not particularly limited, and examples thereof include gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), and ruthenium (Ru). . Further, the washing waste liquid contains a noble metal derived from a plating catalyst imparting agent. Examples of the plating catalyst imparting agent include an agent for imparting a plating catalyst for performing electroless plating to an object to be plated. More specifically, a hydrochloric acid acidic solution containing palladium (Pd) and tin (Sn), such as a hydrochloric acid acidic solution containing palladium chloride and stannous chloride (hydrochloric acid acidic Pd—Sn in which Pd and Sn coexist) Solution) and the like. In addition, the washing | cleaning waste liquid at the time of using the hydrochloric acid acidic solution containing palladium (Pd) and tin (Sn) as a plating catalyst provision agent is also called PdSn catalyst waste liquid. By using such a washing waste liquid as a processing object in the recovery method according to the present embodiment, palladium used as a plating catalyst can be recovered, which is very significant. From this point, palladium is preferable as the noble metal. As a plating catalyst imparting agent used when performing electroless plating, a hydrochloric acid acidic solution containing palladium (Pd) and tin (Sn) is generally used. For this reason, it is preferable that the noble metal is palladium and the other metal is tin. That is, it is possible to recover palladium as a noble metal from a PdSn catalyst waste liquid that is a washing waste liquid when a hydrochloric acid acidic solution containing palladium (Pd) and tin (Sn) is used. Is meaningful. Moreover, as an aqueous solution containing a noble metal, what contained only 1 type of the noble metal of the said illustration may be contained, and 2 or more types may be contained.

  In addition, the concentration of the organic compound in the post-addition solution that is an aqueous solution containing the hydrochloric acid-containing Sn-containing precious metal catalyst recovery solution after the addition step is such that the recovery rate of the precious metal is increased as described above. There is no particular limitation. The concentration is, for example, preferably 0.5 to 1.1 mol / L, more preferably 0.6 to 1 mol / L when oxalic acid or tartaric acid is used as the organic compound. More preferably, it is 0.7-0.9 mol / L. Further, when the aqueous solution containing the hydrochloric acid Sn-containing noble metal catalyst recovery liquid contains a metal other than the noble metal, specifically, when the plating catalyst imparting agent contains a metal other than the noble metal, The concentration of the organic compound in the aqueous solution containing the hydrochloric acid-containing Sn-containing noble metal catalyst recovery solution (post-addition solution) after the addition step is preferably as follows. Specifically, the concentration is preferably such that the content of the organic compound relative to the other metal in the aqueous solution is 0.3 to 5 times in terms of molar ratio. As described above, the molar ratio is preferably 0.3 to 5 times, more preferably 0.5 to 4 times, and even more preferably 0.7 to 3 times. Further, if the concentration is too low, there is a tendency that the effect of improving the recovery rate of the noble metal by adding the organic compound cannot be sufficiently exhibited. On the other hand, if the concentration is too high, the COD concentration in the wastewater after the recovery of Pd increases, and the load of the subsequent wastewater treatment increases. Moreover, even if it adds more than this, an effect hardly changes and there exists a tendency for the organic compound to add to become useless. Therefore, when the concentration of the organic compound is within the above range, the recovery rate of the noble metal can be further increased.

  Moreover, the collection | recovery method which concerns on this embodiment may make a washing waste liquid as mentioned above into a process target object. The following aspects are mentioned as this specific aspect.

  First, the object to be plated is immersed in a plating catalyst imparting agent containing a noble metal stored in the catalyst tank 11. And the to-be-plated to-be-plated processed material taken out from the catalyst tank 11 is sequentially immersed in the several water-washing tanks 12, 13, and 14 as shown in FIG. By performing such a water washing step, the object to be plated is washed with water. As the plurality of washing tanks 12, 13, and 14, the plurality of washing tanks arranged so that the liquid in the tank flows into the previous washing tank from the subsequent washing tank in the order of immersing the object to be plated. Use. Here, as the plurality of washing tanks 12, 13, and 14, the first washing tank 12 which is the first washing tank and the first washing tank 12 have the order in which the objects to be plated are immersed after the first washing tank 12. Although the 3rd water washing tank of the 2nd water washing tank 13 which is the water washing tank of the 2nd and the 3rd water washing tank 14 which is the water washing tank after the order in which the said to-be-plated process thing is immersed from the said 2nd water washing tank 13 is used. Four or more washing tanks may be used. By sequentially immersing the objects to be plated in the plurality of washing tanks 12, 13, and 14 as described above, the cleanliness of the liquid in the tank is gradually increased, so that the objects to be plated are efficiently washed with water. be able to. In such a water washing process, the noble metal concentration in the liquid in the tank of the 1st water washing tank 12 is the highest. Moreover, the liquid in the tank of the 3rd water washing tank 14 flows into the 1st water washing tank 12 finally via the 2nd water washing tank 13, and the liquid in the tank of the 2nd water washing tank 13 is also Then, it flows into the first washing tank 12. From these things, the liquid in the tank of this 1st washing tank 12 is used as an aqueous solution containing the hydrochloric acid acidic Sn containing noble metal catalyst recovery liquid which is a processing target in the recovery method concerning this embodiment at the addition process. It is preferable. In such an aspect, as shown in FIG. 1, the adding step according to the present embodiment stores the liquid that has flowed out of the first water washing tank 12 in the collecting tank 15 and uses the adding device 16 to collect the liquid. Examples include a step of adding the organic compound to the liquid stored in the tank 15. By adopting such an embodiment, the noble metal can be efficiently recovered from the washing waste liquid in which it is difficult to recover the noble metal by a simpler method. FIG. 1 is a schematic diagram for explaining an example of a noble metal recovery method according to an embodiment of the present invention.

  Further, the passing step in the recovery method according to the present embodiment is a post-addition liquid (organic having a carboxy group in the molecule), which is an aqueous solution in which an organic compound having a carboxy group in the molecule is added to the aqueous solution containing the recovery liquid. The aqueous solution to which the compound is added is not particularly limited as long as it passes through an activated carbon layer containing predetermined activated carbon. That is, this step is a step in which an aqueous solution in which an organic compound having a carboxy group is added in the molecule (post-addition solution) is brought into contact with activated carbon, and the noble metal in the aqueous solution is adsorbed onto the activated carbon. Specific examples of the passing step include a step of allowing an aqueous solution to which the organic compound is added to pass through a filter (activated carbon holding filter) including activated carbon. By doing so, the noble metal contained in the aqueous solution to which the organic compound is added is adsorbed to the activated carbon provided in the filter. Therefore, a high recovery rate can be realized by using an aqueous solution to which an organic compound as described above is added (liquid after addition) as the liquid that passes through the filter. This is presumably because the addition of an organic compound increases the ability of the noble metal to be adsorbed on the activated carbon as compared to Sn, so that Sn and the noble metal are separated and the noble metal is preferentially adsorbed on the activated carbon. More specifically, as the passing step, as shown in FIG. 1, a step of passing the liquid in the tank from the recovery tank 15 through the filter 18 including activated carbon by the pump 17 can be mentioned. In addition, as shown in FIG. 1, the aqueous solution containing the hydrochloric acid acidic Sn-containing noble metal catalyst recovery solution may be circulated and passed through a filter provided with activated carbon a plurality of times. Further, the liquid that has passed through the filter may be discharged through a flow path in which a flow meter 19 is installed.

  Moreover, in the collection | recovery method which concerns on this embodiment, if the said activated carbon layer is a process of isolate | separating from the liquid after addition (liquid after passage) which passed the said activated carbon layer, it will not specifically limit. This process is also called a separation process. Examples of the separation step include a step of recovering the activated carbon layer after the solution after addition has passed. In the separation step, the noble metal adsorbed on the activated carbon can be desorbed and recovered as a noble metal. That is, as the separation step, more specifically, the activated carbon layer after passing the post-addition solution is separated from the post-passage solution, and the adsorbed noble metal is desorbed from the activated carbon contained in the activated carbon layer. And the like.

  The method for desorbing the noble metal adsorbed on the activated carbon is not particularly limited. As this desorption method, specifically, a method in which activated carbon on which a noble metal is adsorbed is directly dissociated as a noble metal salt with an inorganic strong acid such as aqua regia, and is recovered as metallic palladium by hydrogen reduction or electrolytic reduction. Alternatively, the activated carbon adsorbing the noble metal is burned to be ashed, and the noble metal is extracted from the obtained ashed product with an inorganic strong acid such as aqua regia and reduced.

  Moreover, when the process which makes the activated carbon layer pass the aqueous solution by which the acid concentration was maintained as the said passing process is used, the space velocity SV is not specifically limited. The space velocity SV is, for example, preferably 1 to 5000 / h, more preferably 10 to 4500 / h, and still more preferably 100 to 4000 / h. The higher the space velocity SV, the greater the amount of treatment, but the shorter the contact time with activated carbon, the lower the precious metal recovery rate. In the recovery method according to the present embodiment, even when the space velocity is relatively high, for example, even when the aqueous solution is passed through the filter under a relatively high speed condition of a space velocity of 500 / h or more, High recovery rate can be maintained. From this, even if the space velocity SV is within the above range, a sufficiently excellent recovery rate can be realized.

  The space velocity SV can be measured by a known method. The space velocity SV is calculated, for example, by measuring the flow rate and dividing the measured flow rate by the volume of the filter medium of the filter.

  The activated carbon layer is not particularly limited as long as it includes predetermined activated carbon and is layered. That is, it is not particularly limited as long as it is provided with activated carbon so that the liquid passing through this layer contacts the activated carbon. Examples of the activated carbon layer include activated carbon provided in a filter shape, and activated carbon packed in a cylindrical container such as a cylinder. Among these, as the activated carbon layer, a filter-like filter is preferably used for convenience and the like.

  Although the case of a filter will be described as the activated carbon layer, as described above, the activated carbon layer is not particularly limited as long as it includes a predetermined activated carbon and is layered.

  As the above filter, for example, a molded body of a mixture containing activated carbon and a binder may be used.

  The content of activated carbon contained in the filter is preferably 20% by mass or more. A higher activated carbon content is preferable in terms of improving the amount of precious metal adsorption, but in practice, it is difficult to form a filter with only activated carbon. Moreover, the content of activated carbon should just be the quantity which can hold | maintain activated carbon to a filter, and although it changes with kinds of binder etc., about 97 mass% is a limit normally. From these things, it is preferable that content of the activated carbon contained in the said filter is 20-97 mass%, It is more preferable that it is 30-95 mass%, It is further more preferable that it is 35-90 mass%. .

  A binder will not be specifically limited if it can hold | maintain activated carbon and can comprise a filter. Moreover, as a binder, the binder which can hold | maintain activated carbon and can be shape | molded in a filter shape may be sufficient, for example, and the binder for carrying | supporting activated carbon on the base material which comprises a filter may be sufficient. Specific examples of such a binder include fibrillated fibers and thermoplastic binder particles. Moreover, as a binder, it can use besides these, Moreover, these may be used independently and may be used in combination of 2 or more types of binders.

  The fibrillated fiber may be a pulp-like fiber obtained by defibrating a fiber that can be fibrillated using a high-pressure homogenizer, a high-speed disaggregator, or the like. The average fiber diameter of the fibrillated fiber is, for example, preferably 0.1 to 50 μm, and more preferably 1 to 20 μm. Moreover, it is preferable that it is 0.5-4 mm, for example, and, as for the average fiber length of a fibrillated fiber, it is more preferable that it is 1-2 mm. Specific examples of the fibers forming the fibrillated fibers include acrylic fibers, polyethylene fibers, polypropylene fibers, polyacrylonitrile fibers, cellulose fibers, polyamide fibers, and aramid fibers. Among these, acrylic fiber and cellulose fiber are preferable because they are easily fibrillated and have a high effect of restraining activated carbon. As a commercially available product, for example, “Bi-PUL”, which is a homo acrylic pulp manufactured by Nippon Exlan Industrial Co., Ltd., can be obtained.

  Further, the thermoplastic binder particles may be formed of a thermoplastic polymer capable of fusing activated carbon. Specific examples of the thermoplastic polymer include polyolefin, polystyrene, polymethyl methacrylate, polyacrylonitrile, ethylene-vinyl acetate copolymer, polyester, polyamide, and polyurethane. These polymers may be used alone or in combination of two or more. Among these, polyethylene, polypropylene, polystyrene, ethylene-vinyl acetate copolymer, polyethylene terephthalate, polybutylene terephthalate, polymethyl methacrylate, and the like are widely used, and polyethylene is particularly preferable from the viewpoint of binding properties. The average particle diameter of the thermoplastic binder particles is preferably, for example, 0.1 to 200 μm, and more preferably 1.0 to 50 μm, from the viewpoint of excellent sheet strength and moldability.

  The manufacturing method of a filter provided with the said activated carbon will not be specifically limited if the filter of the above structures can be manufactured. As a manufacturing method of the filter provided with the activated carbon, for example, a conventional method can be used according to the kind of the binder.

  When fibrillated fibers are used as the binder, a method using wet molding is preferable as a method for producing the filter including the activated carbon. Specifically, the activated carbon and the fibrillated fiber are mixed and then dispersed in water so that the solid concentration is about 0.1 to 10% by mass (particularly 1 to 5% by mass). And a method including a slurry preparation step of preparing a slurry and a drying step of removing moisture from the prepared slurry. A drying process is not specifically limited, For example, you may use the method of pouring a slurry into the water-permeable box-shaped container formed from the metal net made from stainless steel, etc., draining water, and drying. In the drying process, the prepared slurry is filled into a mold cavity having a sheet-shaped cavity having a predetermined shape and a large number of through-holes for decompressing the inside of the cavity, and moisture in the slurry is removed from the through-holes. A method of removing by suction may be used. More specifically, examples of the method including the drying step of removing by suction include the method described in Japanese Patent No. 3516811. The ratio of the fibrillated fiber is preferably 1 to 20 parts by mass, and preferably 3 to 10 parts by mass with respect to 100 parts by mass of the activated carbon, from the viewpoint of excellent balance such as water resistance and moldability. Is more preferable. Furthermore, when the binder is fibrillated fiber, the shape of the activated carbon may be fibrous.

  When thermoplastic binder particles are used as the binder, a method using dry molding is preferable as a method for producing the filter including the activated carbon. As this method, for example, a method using injection molding or the like can be mentioned. More specifically, using a mixer such as a Henschel mixer, the activated carbon powder and the thermoplastic binder particles are mixed by stirring at a desired ratio. A molding step in which a mold having a sheet-like cavity is filled with the obtained mixture, and the mold is heated to a melting point or higher than the melting point of the thermoplastic binder particles to melt or soften the binder particles, and then cooled and solidified. And the like. The ratio of the thermoplastic binder particles is preferably 5 to 50 parts by mass, and more preferably 7 to 20 parts by mass with respect to 100 parts by mass of the activated carbon from the viewpoint of excellent sheet strength and moldability. .

  The activated carbon used here is not particularly limited as long as the relationship between the zeta potential and the pore volume satisfy the above numerical range. The activated carbon is as follows.

  First, the activated carbon has an absolute value of a difference between a zeta potential in a 10 mmol / L sodium tetraborate aqueous solution and a zeta potential in a 0.01 mmol / L sodium tetraborate aqueous solution of 0 to 25 mV, It is preferably 18 mV. The zeta potential here is, for example, the zeta potential at normal temperature (25 ° C.). If the difference in zeta potential is too large, the adsorptive capacity of activated carbon for noble metals tends to decrease. This is considered to be as follows. First, since there are many functional groups that can be dissociated in an aqueous sodium tetraborate solution, it is considered that the ability to electrostatically adsorb noble metal ions increases and inhibits the reducing ability. Further, it is considered that noble metal ions are easily adsorbed in an oxide state, and the adsorption of noble metal ions depends on the amount of functional groups. From these facts, it is considered that noble metal ions cannot be adsorbed with high yield.

  In addition, the absolute value of the difference in zeta potential is preferably 0.01 to 15 mV, more preferably 0.1 to 12 mV, and more preferably 1 to 5 mV from the viewpoint of adsorptivity of noble metals. Further preferred. Further, the absolute value of the difference in zeta potential is preferably 3 to 15 mV, more preferably 5 to 12 mV, and more preferably 8 to 11 mV, from the viewpoint of adsorbing noble metals with high selectivity to base metals. More preferably it is.

  The activated carbon preferably has a zeta potential in a 10 mmol / L sodium tetraborate aqueous solution of −60 to 0 mV, more preferably −50 to −5 mV, and −45 to −10 mV. Is more preferable, and it is still more preferable that it is -40--20mV. When the zeta potential at this concentration is within the above range, it is possible to efficiently adsorb noble metals contained in an aqueous solution such as a washing waste liquid at a low concentration.

  In addition, the measuring method of zeta potential can be measured by a well-known method, for example, can be measured using a zeta potential measuring device. More specifically, it can be measured by the method described in the examples.

Further, the activated carbon, volume of pores pore radius 1nm is a 45~500mm ³ / g, is preferably 150~500mm ³ / g, more preferably 200 to 450 mm ³ / g 250 to 420 mm ³ / g, more preferably 300 to 400 mm ³ / g, and particularly preferably 350 to 380 mm ³ / g. If the pore volume is too small or too large, the ability of activated carbon to adsorb noble metals tends to be insufficient. This is presumably due to the fact that if the pore volume is too small, the volume used for the adsorption or reduction reaction is substantially reduced, so that the adsorption amount of the noble metal is reduced. Further, it is considered that if the pore volume is too large, the bulk density is lowered and a sufficient amount of noble metal adsorption per unit volume cannot be obtained.

  In addition, the measuring method of the pore volume with a pore radius of 1 nm or less can be measured by a publicly known method, and examples thereof include a method of performing nitrogen adsorption isotherm measurement and calculating from the obtained adsorption isotherm. More specifically, it can be measured by the method described in the examples.

  Moreover, it is preferable that the activated carbon has high decolorization performance of the sugar solution from the viewpoint of the adsorption rate. Specifically, the activated carbon preferably has a decolorization performance of the sugar solution of 30 to 100%, more preferably 50 to 99%, still more preferably 70 to 98%, and more preferably 80 to It is still more preferable that it is 97%, and it is especially preferable that it is 85-95%. If the decolorization performance of the sugar solution is within the above range, the movement and diffusion of the adsorbing substance such as noble metal ions within the activated carbon can be facilitated, and the adsorption speed of the noble metal can be increased. For this reason, the activated carbon whose decolorization performance of the sugar solution is within the above range is suitable for a dynamic filter such as a liquid passing filter. On the other hand, if the decolorization performance of the sugar solution is too low, it may take time to adsorb the noble metal.

  In addition, the measuring method of sugar liquid decoloring performance can be measured by a well-known method, for example, can be evaluated by measuring the light absorbency of a sugar liquid. More specifically, it can be measured by the method described in the examples.

Further, the activated carbon, BET specific surface area calculated by the nitrogen adsorption method, is preferably 100~5000m ² / g, more preferably 300~4000m ² / g, in 500~3000m ² / g more preferably in, even more preferably from 1000~2500m ² / g, still more preferably from 1500~2300m ² / g, particularly preferably 1800~2200m ² / g. If the specific surface area is too small or too large, the adsorbability of activated carbon for precious metals tends to be insufficient. This is presumably because if the specific surface area is too small, the amount of precious metal adsorbed decreases due to a decrease in the volume used for adsorption or reduction reaction. Moreover, when the said specific surface area is too large, it is thought that adsorption capacity falls by the fall of a bulk density.

  In addition, the measuring method of a specific surface area can be measured by a well-known method, For example, the method etc. which perform a nitrogen adsorption isotherm measurement and calculate from the obtained adsorption isotherm are mentioned. More specifically, it can be measured by the method described in the examples.

  Moreover, the shape of the activated carbon is not particularly limited. Examples of the shape of the activated carbon include granular, fibrous, and indeterminate shapes, and are usually granular or fibrous. In the case of a granular form, the activated carbon preferably has an average primary particle of, for example, 1 μm to 5 mm, and more preferably 10 μm to 2 mm. In the case of a fiber, the activated carbon preferably has an average fiber diameter of, for example, 1 to 500 μm, more preferably 2 to 300 μm, and further preferably 5 to 50 μm.

  Moreover, the manufacturing method of the said activated carbon is not specifically limited, A well-known method etc. are mentioned. Specifically, examples of the method for producing the activated carbon include a method of carbonizing a carbonaceous material and then activating the carbonized carbonaceous material.

  The carbonaceous material is not particularly limited. Specifically, examples of the carbonaceous material include plant-based carbonaceous materials, mineral-based carbonaceous materials, synthetic resin-based carbonaceous materials, and natural fiber-based carbonaceous materials. More specifically, plant-based carbonaceous materials include plant-derived materials such as wood, sawdust, charcoal, fruit shells such as coconut shells and walnut shells, fruit seeds, pulp production by-products, lignin, and molasses. Can be mentioned. In addition, examples of the mineral-based carbonaceous material include mineral-derived materials such as peat, lignite, lignite, lanthanum, anthracite, coke, coal tar, coal pitch, petroleum distillation residue, and petroleum pitch. In addition, examples of the synthetic resin-based carbonaceous material include materials derived from synthetic resins such as phenol resin, polyvinylidene chloride, and acrylic resin. Examples of the natural fiber carbonaceous material include materials derived from natural fibers such as natural fibers such as cellulose and regenerated fibers such as rayon. As the carbonaceous material, one kind may be used alone, or two or more kinds may be used in combination. Moreover, as a carbonaceous material, plant-type carbonaceous materials, such as a coconut shell, are preferable from the point that the pore volume with a pore radius of 1 nm or less is easy to develop.

  Moreover, it does not specifically limit as an activation method at the time of manufacturing activated carbon, For example, any activation of gas activation and chemical activation is employable. Moreover, as an activation method, gas activation and chemical activation may be combined.

  Moreover, as gas used in gas activation, water vapor | steam, a carbon dioxide gas, oxygen, LPG combustion exhaust gas, or these mixed gas etc. can be mentioned, for example. Among these, as the gas used in the gas activation, in view of safety and reactivity, a steam-containing gas containing 10 to 50% by volume of steam is preferable.

  Moreover, conditions, such as activation temperature, activation time, and temperature rising rate, are not specifically limited, It can select suitably by the kind, shape, size, etc. of carbonaceous material. Specifically, the activation temperature is preferably 700 to 1100 ° C, and more preferably 800 to 1000 ° C.

  Examples of the chemical activator used in chemical activation include chemicals having dehydration, oxidation, and erosion. Specific examples of the chemical activator include zinc chloride, potassium hydroxide, sodium hydroxide, phosphoric acid, potassium sulfide, sulfuric acid, and various alkalis. As a chemical activator, 1 type may be used independently and may be used in combination of 2 or more type. Moreover, as a chemical activator, zinc chloride and phosphoric acid are preferable from the point that a pore volume with a pore radius of 1 nm or less is easily developed.

  Moreover, the density | concentration and usage-amount of a chemical activator are not specifically limited, According to the kind of chemical activator, the quantity of a raw material, etc., it can select suitably. When phosphoric acid is used, the carbonaceous raw material is mixed with about 30 to 95% by mass, preferably 60 to 80% by mass phosphoric acid, and this mixture is heated at 300 to 750 ° C. for 20 minutes to 10 hours, preferably 30 minutes to Activate by heating for about 5 hours. Further, when zinc chloride is used, when the zinc chloride concentration is about 40 to 70% by mass, for example, 0.4 to 5.0 times by mass, preferably 1.0 to 4.5 times by mass, more preferably 1 About 5 to 3.5 times the mass. The activation time is, for example, about 20 minutes to 10 hours, preferably about 30 minutes to 5 hours. The activation temperature is a temperature not higher than the boiling point of zinc chloride (732 ° C.). This temperature is usually about 450 to 730 ° C, preferably about 550 to 700 ° C.

  Moreover, you may wash | clean the activated carbon after activation, in order to remove ash and a chemical | medical agent. The activated carbon after washing may be heat-treated in an inert gas atmosphere in order to remove impurities that could not be removed sufficiently by washing. By sufficiently removing the impurities by heat treatment, the activated carbon adsorbing the noble metal can be burned and ashed, and contamination of the impurity can be prevented when extracting the noble metal from the obtained ash. Moreover, activated carbon after activation may be pulverized, or may be cut if it is fibrous.

  For pulverization, for example, a jaw crusher, a hammer mill, a pin mill, a roller mill, a rod mill, a ball mill, a jet mill, or the like can be used depending on the target particle size.

  The present invention will be described more specifically with reference to the following examples. However, the scope of the present invention is not limited to these examples.

  First, each physical property value of the activated carbon used in this example was measured by the following method.

[Specific surface area and pore volume with pore radius of 1 nm or less]
The specific surface area of the sample (activated carbon) and the pore volume with a pore radius of 1 nm or less were calculated from the adsorption isotherm obtained by measuring the nitrogen adsorption isotherm. Specifically, first, 0.1 g of a sample was filled in a sample tube, and pretreatment was performed under reduced pressure at 300 ° C. for 5 hours. Using Belsorb 28SA (manufactured by Nippon Bell Co., Ltd.), the nitrogen adsorption isotherm of the sample was measured at the liquid nitrogen temperature of the sample part. Using the obtained adsorption isotherm using BEL analysis software (Version 4.0.13), the two points with the highest correlation coefficient are the relative pressure of 0.01 or less and the relative pressure of 0.05 to 0.1. The specific surface area was determined. The pore volume with a pore radius of 1 nm or less was calculated by the CI method of the software.

[Zeta potential difference]
The zeta potential of the sample (activated carbon) was measured using a zeta potential measuring device. Specifically, first, 20 mg of activated carbon powder (center particle diameter: 6 to 7 μm) was added to 100 mL of an aqueous solution having a sodium tetraborate concentration of 10 mmol / L and 0.01 mmol / L to prepare a dispersion. Using this dispersion, a particle movement speed at 25 ° C. for calculating the zeta potential was measured using a zeta potential measuring device (“MARK II” manufactured by RANK BROTHERS). The particle moving speed was measured by introducing the dispersion into a predetermined cell, observing the particles in the dispersion in the cell measuring section with a microscope, and measuring the particle moving speed under a voltage of 20V. As for the particle moving speed, the time (second) when moving a distance of 60.3 μm was measured for 5 to 10 particles. Using the average value (S) of the measured time, the zeta potential in a 10 mmol / L sodium tetraborate aqueous solution and the zeta potential in a 0.01 mmol / L sodium tetraborate aqueous solution were respectively represented by the following formulas: Asked. And the difference (zeta potential difference) was calculated. The distance between the electrodes necessary for the calculation is 8.53 cm.

Electric field A (V / cm) = 20 / 8.53 = 2.345 V / cm
Particle migration speed L (μm / sec) = 60.3 / S
Mobility (μm · cm / sec · V) = L / A
Zeta potential (mV) =-12.83 × mobility.

[Sugar liquid decolorization performance]
The sugar solution decolorization performance was evaluated by measuring the absorbance of the sugar solution. Specifically, first, 350 g of trithermal sugar (manufactured by Mitsui Sugar Co., Ltd.) is collected, 300 ml of ion-exchanged water is added, and the mixture is dissolved by stirring at 70 ° C. or lower. After cooling, the pH is adjusted to 7 ± 0.1 with NaOH or HCl. On the other hand, 300 g of granulated sugar (manufactured by Mitsui Sugar Co., Ltd.) is collected, 300 ml of ion-exchanged water is added, and stirred and dissolved at 70 ° C. or lower. After cooling, the pH is adjusted to 7 ± 0.1 with NaOH or HCl. A sugar solution in which the absorbance at a wavelength of 420 nm is adjusted to a range of 0.75 to 0.78 using the two types of sugar solutions is defined as a stock solution for measuring a sugar solution decolorization performance.

  0.092 g of activated carbon is weighed into a 100 ml conical stoppered Erlenmeyer flask, 50 ml of the stock solution for measuring sugar liquid decolorization performance is added, and shaken at 50 ° C. with an amplitude speed of 130 to 140 reciprocations / minute for 1 hour. Filtration was carried out using a filter paper 5C in a constant temperature bath at 50 ° C., the absorbance at wavelengths of 420 nm and 700 nm of the filtrate was measured, and the sugar solution decolorization performance was calculated by the following formula.

Absorbance (420nm)-Absorbance (700nm) = A
(A blank-A sample) / A blank = molasses decolorization performance (%)
(In the formula, A blank is A when activated carbon is not added, and A sample is A when activated carbon is added).

[Oxygen atom% by XPS]
The activated carbon before palladium adsorption was measured with an X-ray photoelectron spectrometer (“PHI Quantera SXM” manufactured by ULVAC-PHI Co., Ltd.). X-ray excitation conditions: 100 μm-25W-15 kV, cathode: Al, measurement range: 1000 μm × 1000 μm The pressure was measured under the measurement conditions of 6 × 10 ⁻⁷ Pa, and O1s waveform separation analysis was performed to calculate oxygen atom%.

[Binding state of palladium by XPS]
The activated carbon on which palladium was adsorbed was subjected to X-ray photoelectron spectrometer (“PHI Quantera SXM” manufactured by ULVAC-PHI Co., Ltd.) to determine the binding state of palladium, X-ray excitation condition: 100 μm-25W-15 kV, counter cathode: Al Measurement range: 1000 μm × 1000 μm, pressure: 6 × 10 ⁻⁷ Pa Measurement was performed, and the binding state of various activated carbons was analyzed from the spectrum of Pd3d. The attribution of the binding species of Pd3d5 / 2 is shown (refer to XPS handbook).

Pd: 335.3 eV (± 0.2)
PdO: 336.3 eV (± 0.2)
halides: 337.1 eV (± 0.7)
PdO ₂ : 338.0 (± 0.3).

  Next, the activated carbon used in this example will be described.

Production Example 1 (activated carbon No. 1)
100 g of coconut shell charcoal having an alkaline earth metal content of 4 g / kg was activated at 920 ° C. As for the gas composition at the time of activation, the CO ₂ partial pressure is 10%, the H ₂ O partial pressure is 30%, and the other gas is N ₂ . The activation time was 20 minutes. The obtained activated carbon was washed with a 1 mol / L hydrochloric acid aqueous solution, washed with water, and then dried. The obtained dried product was heat-treated at 700 ° C. for 30 minutes in a fluidized furnace. The gas at the time of heat processing was implemented with the LNG combustion gas. Table 1 shows various physical properties of the obtained activated carbon.

Production Example 2 (activated carbon No. 2)
After adding 100 mL of a 4000 g / L aqueous zinc chloride solution to 100 g of sawdust, the temperature was raised to 700 ° C. at a rate of 5 ° C./min, kept at 700 ° C. for 1 hour, and then cooled. The obtained activated carbon was washed by boiling with 1 mol / L hydrochloric acid and washed with water. Table 1 shows various physical properties of the obtained activated carbon.

Production Example 3 (activated carbon No. 3)
100 g of coconut shell charcoal having an alkaline earth metal content of 1 g / kg was activated under the same conditions as in Production Example 1. The activation time was 3 hours. The obtained activated carbon was washed with 1 mol / L hydrochloric acid, washed with water, dried, and subjected to the same heat treatment as in Production Example 1. Table 1 shows various physical properties of the obtained activated carbon.

Production Example 4 (activated carbon No. 4)
100 g of sawdust was impregnated with a 75% phosphoric acid aqueous solution so that the phosphoric acid was 150 g, and heat treatment was performed at a temperature of 550 ° C. During the heat treatment, air was flowed at a rate of 3 L / min. After the heat treatment, the obtained fired product was washed with boiling water. Table 1 shows various physical properties of the obtained activated carbon.

Production Example 5 (activated carbon No. 5)
100 g of sawdust was impregnated with a 75% concentration phosphoric acid aqueous solution so that phosphoric acid was 100 g, and heat treatment was performed at a temperature of 550 ° C. During the heat treatment, air was flowed at a rate of 3 L / min. After the heat treatment, the obtained fired product was washed with boiling water. Table 1 shows various physical properties of the obtained activated carbon.

Production Example 6 (activated carbon No. 6)
The phenol resin fiber was oxidized at 300 ° C. for 1 hour, and the oxidized product was subjected to dry distillation at 700 ° C. for 1 hour. The obtained phenol resin fiber subjected to dry distillation treatment was treated in an LPG combustion gas atmosphere at an activation temperature of 950 ° C. for 5 hours. Table 1 shows various physical properties of the obtained activated carbon.

Activated carbon No. 7
Commercially available activated carbon (“GW-H” manufactured by Kuraray Chemical Co., Ltd.) It was set to 7. The various physical properties are shown in Table 1.

Activated carbon No. 8
Commercially available activated carbon (“KW” manufactured by Kuraray Chemical Co., Ltd.) It was set to 8. The various physical properties are shown in Table 1.

Production Example 7 (activated carbon No. 9)
Activation was performed for 30 minutes under the same conditions as in Example 1 using raw ash obtained by dry distillation of sawdust. The obtained activated carbon was washed with 1 mol / L hydrochloric acid, washed with water and dried. Table 1 shows various physical properties of the obtained activated carbon.

Activated carbon No. 10
Commercially available activated carbon (Kuraray Chemical Co., Ltd. “GW”) was activated carbon. It was set to 10. The various physical properties are shown in Table 1.

Production Example 8 (activated carbon No. 11)
The phenol resin fiber was oxidized at 300 ° C. for 1 hour, and the oxidized product was subjected to dry distillation at 700 ° C. for 1 hour. The obtained carbonized phenol resin fiber was treated in an LPG combustion gas atmosphere at an activation temperature of 950 ° C. for 3 hours. Table 1 shows various physical properties of the obtained activated carbon.

Production Example A (activated carbon holding filter A)
Activated charcoal No. 100L for tap water 100L in a small 100L beater. 6 (fibrous activated carbon) was added in a dry weight of 1.5 kg, and then fibrillated acrylic pulp (“Bi-PUL / F” manufactured by Nippon Exlan Kogyo Co., Ltd.) as a binder was equivalent to 0.075 kg in dry weight. The fibrous activated carbon is finely divided by dispersing and mixing the fibrous activated carbon and the binder and narrowing the gap between the fixed teeth and the rotating teeth of the beater. When the fiber length of the fibrous activated carbon is shortened, the weight per unit volume increases because the filling property is improved when the fiber is formed into a fixed shape. This weight per unit volume was called the beating density, and was used as a measure of the shortness of the fibrous activated carbon. As a molded body for measuring the beating density, a double tubular molding die provided with a large number of small holes for suction described in Japanese Patent No. 3516811, 300 mm on the center axis of a small hole diameter for suction of 3 mmφ and a pitch of 5 mm. A mesh metal mesh was wound to prepare a mold having a medium shaft diameter of 18 mmφ, an outer diameter of 40 mmφ, and an outer diameter of 50 mm, and a slurry was sucked from the center to prepare a cylindrical molded body. A slurry having a beating density of 0.18 g / ml was obtained from the size and weight of the dried product of the molded body, and the slurry having the beating density was used as a standard slurry.

  Activated carbon No. classified into 7 L of this standard slurry was classified to JIS 30/60 Mesh. 1 (granular) 0.735 kg, activated carbon No. 1 pulverized so that D50 measured by a wet particle size analyzer (“Microtrac MT3000” manufactured by Nikkiso Co., Ltd.) is about 40 μm. 0.21 kg of 1 (powder) and 0.053 kg of fibrillated acrylic pulp (Bi-PUL / F) in terms of dry weight were added, and tap water was further added to make the amount of slurry 110 L.

  Using the slurry, suction molding was performed to prepare a molded body of 250 mm × 250 mm × 5 mm.

  The produced molded body was dried and punched with a Thomson blade having an inner diameter of 10 mmφ to obtain an activated carbon holding filter A having an outer diameter of 10 mmφ and a thickness of 5 mm. At this time, the weight of the molded body was 0.09 g.

Moreover, the said pore volume in the mixed state of the activated carbon contained in the activated carbon holding filter A was 351 mm < ³ > / g.

Production example B (activated carbon retention filter B)
Activated charcoal No. classified to JIS 30/60 Mesh with respect to 7 L of standard slurry similar to Production Example A was obtained. 7 (granular) 0.735 kg, activated carbon No. 7 pulverized so that D50 measured by a wet particle size analyzer (“Microtrac MT3000” manufactured by Nikkiso Co., Ltd.) is about 40 μm. 7 (powder) 0.21 kg and fibrillated acrylic pulp (Bi-PUL / F) 0.053 kg in terms of dry weight were added, and tap water was further added to make the amount of slurry 110 L. In the same manner as in Production Example A, suction molding, drying, and punching were performed to obtain an activated carbon holding filter B. At this time, the weight of the molded body was 0.13 g.

Moreover, the pore volume in the mixed state of activated carbon contained in the activated carbon holding filter B was 79 mm ³ / g.

Production Example C (activated carbon holding filter C)
The tap water 88L was added only to the same standard slurry 22L as in Production Example A, and suction molding, drying, and punching were performed in the same manner as in Production Example A to obtain an activated carbon holding filter C. At this time, the weight of the molded body was 0.07 g.

The activated carbon contained in the activated carbon holding filter C had a zeta potential difference of 14.9 mV. Moreover, the said pore volume in the mixed state of the activated carbon contained in the activated carbon holding filter C was 200.0 mm < ³ > / g.

  Table 2 shows the mixing ratio of the activated carbon retaining filter.

[Example]
Example 1
First, as an aqueous solution containing a hydrochloric acid acidic Sn-containing noble metal catalyst recovery solution, a Pd—Sn catalyst aqueous solution (Pd—Sn catalyst simulated waste liquid) containing 5.4 mg / L of palladium and 250 mg / L of tin was used as a standard solution.

  Next, the collection method according to the present embodiment was evaluated by the following method.

  First, as shown in FIG. 2, the Pd—Sn catalyst simulated waste liquid was stored in the supply tank 21. The stored Pd—Sn catalyst simulated waste liquid was pumped by the pump 22 and passed through the activated carbon holding filter 23. Thereafter, the passed liquid (filtrate) was stored in the collection tank 24. And the palladium (Pd) density | concentration of the liquid stored in the collection tank 24 was measured, and the collection | recovery rate of palladium in the activated carbon holding | maintenance filter 23 was computed from the decreasing amount of palladium density | concentration. The palladium concentration or tin concentration of the filtrate was adjusted by adding 50 μl of nitric acid for measuring harmful metals (manufactured by Wako Pure Chemical Industries, Ltd.) to 20 ml of the filtrate, and using an ICP emission spectroscopic analyzer (manufactured by Perkin Elmer Co., Ltd.). "Optical Emission Spectrometer Optima 4300 DV"). Further, by adjusting the output of the pump 22 and the like, the liquid passing speed, the space speed SV, and the like can be appropriately adjusted. FIG. 2 shows an apparatus for evaluating the noble metal recovery method according to the embodiment of the present invention.

Then, hydrochloric acid is added to the Pd—Sn catalyst simulated waste liquid to adjust the acid concentration to 0.2 mol / L, and oxalic acid (H ₂ C ₂ O ₄ ) is added to the other organic compound having a carboxy group in the molecule. An activated carbon retaining filter using an oxalic acid content that is an organic compound with respect to tin (Sn) that is a metal in a molar ratio as shown in Table 3 as an aqueous solution containing a hydrochloric acid-containing Sn-containing noble metal catalyst recovery solution. As above, using the activated carbon holding filter A, the recovery rate of palladium in the activated carbon holding filter was measured. At that time, the liquid flow rate was set to 240 mL / h, and the space velocity SV was set to 600 / h. The results are shown in Table 3. FIG. 3 also shows a graph of the results. Table 3 shows the oxalic acid content, space velocity SV, Pd concentration of the supplied liquid (inlet Pd concentration), Pd concentration of the filtrate (outlet Pd concentration), inlet Pd concentration and outlet Pd concentration. The recovered Pd recovery rate is shown. The Pd recovery rate is a value obtained by dividing the difference between the inlet Pd concentration and the outlet Pd concentration by the inlet Pd concentration. Further, “<0.2” in the outlet Pd concentration indicates that the outlet Pd concentration is less than 0.2 mg / L and is lower than the detection limit. Further, “> 96%” in the Pd recovery rate is that the Pd recovery rate is higher than 96%, and the outlet Pd concentration is below the detection limit. FIG. 3 is a graph showing the relationship between the molar ratio of oxalic acid and Sn and the Pd recovery rate. In FIG. 3, the result of Example 1 is indicated by a broken line 31.

  As can be seen from Table 3 and FIG. 3, when oxalic acid is added to the Pd—Sn catalyst simulated waste liquid as much as possible, the Pd recovery rate increases. It can also be seen that the Pd recovery rate increases as the oxalic acid content is increased. From this, the content of oxalic acid relative to tin, that is, the content of the organic compound having a carboxy group in the molecule relative to other metals other than the noble metal is 0.3 to 5 times in molar ratio. It turns out that it is preferable at the point which raises Pd recovery.

  In addition, when the oxalic acid that is an organic compound having a carboxy group in the molecule is not added to the Pd—Sn catalyst simulated waste liquid that is an aqueous solution containing the hydrochloric acid-containing Sn-containing noble metal catalyst recovery liquid, the Pd recovery rate is not sufficiently increased. The reason was examined.

Specifically, the zeta potential of the Pd—Sn catalyst simulated waste liquid was measured. More specifically, the zeta potential of the Pd—Sn catalyst simulated waste liquid when the acid concentration was varied was measured. That is, the relationship between the zeta potential of the Pd—Sn catalyst simulated waste liquid and the acid concentration was measured. At that time, the case where oxalic acid was added to the Pd—Sn catalyst simulated waste liquid was compared with the case where it was not added. The Pd—Sn catalyst simulated waste liquid used at this time was adjusted to have a Pd concentration of 5 mg / L and an Sn concentration of 250 mg / L. The result is shown in FIG. Moreover, in FIG. 4, the result at the time of adding oxalic acid so that the said molar ratio may be set to 0.35 is shown by the broken line 41, and oxalic acid was added so that the said molar ratio might be set to 1.05 The result of the case is indicated by a broken line 42, the result when oxalic acid is added so that the molar ratio is 1.76 is indicated by the broken line 43, and the result when no oxalic acid is added is indicated by the broken line 44. Show. FIG. 4 shows that when oxalic acid is added, the zeta potential decreases regardless of the acid concentration of the Pd—Sn catalyst simulated waste liquid. From this, it is considered that palladium or tin is contained in a Pd ⁰ · nSnOOH ⁺ state in the Pd—Sn catalyst simulated waste liquid without adding oxalic acid and having a low acid concentration. Moreover, it is thought that palladium and tin are contained in the state of Pd ⁰ · nSnCl ₄ ²⁻ in the Pd—Sn catalyst simulated waste liquid to which oxalic acid is added regardless of the acid concentration. From these facts, when oxalic acid is not added to the Pd—Sn catalyst simulated waste liquid, which is an aqueous solution containing a hydrochloric acid acidic Sn-containing noble metal catalyst recovery liquid, and the acid concentration is low, SnO _{2 is} deposited on the surface of the activated carbon holding filter. It is considered that Sn as SnO.OH is easily adsorbed. This is considered to be one of the reasons why the Pd recovery rate is not sufficiently increased when oxalic acid, which is an organic compound having a carboxy group in the molecule, is not added. FIG. 4 is a graph showing the relationship between the acid concentration and the zeta potential.

From the above, when oxalic acid is added to the Pd-Sn catalyst simulated waste liquid, which is an aqueous solution containing a hydrochloric acid acidic Sn-containing noble metal catalyst recovery liquid, palladium and tin are contained in the state of Pd ⁰ · nSnCl ₄ ^2−. It is thought that it is done. For this reason, it is thought that Pd and Sn do not often block the pores of the activated carbon. On the other hand, when oxalic acid is not added to the Pd—Sn catalyst simulated waste liquid, which is an aqueous solution containing hydrochloric acid-containing Sn-containing noble metal catalyst recovery liquid, and its acid concentration is low, palladium and tin are converted into Pd ⁰ · nSnOOH. It is thought that it is contained in a ⁺ state. For this reason, it is speculated that Sn is blocked as SnO _{2 in} the pores of the activated carbon, thereby reducing the adsorptivity of Pd. From these facts, when oxalic acid is not added to the Pd—Sn catalyst simulated waste liquid, which is an aqueous solution containing hydrochloric acid-containing Sn-containing noble metal catalyst recovery liquid, the Pd recovery rate does not increase, and when oxalic acid is added, Pd The recovery rate is thought to increase.

(Example 2)
As an aqueous solution containing a hydrochloric acid acidic Sn-containing precious metal catalyst recovery solution, a Pd-Sn catalyst aqueous solution (Pd-Sn catalyst simulated waste liquid) containing 3.5 mg / L of palladium and 200 mg / L of tin is used as an activated carbon holding filter. Example 1 is the same as Example 1 except that the activated carbon holding filter B is used instead of the activated carbon holding filter A. The results are shown in Table 4.

(Example 3)
Example 2 is the same as Example 2 except that an activated carbon holding filter C is used instead of the activated carbon holding filter B as the activated carbon holding filter. The results are shown in Table 5.

  As can be seen from Tables 4 and 5, even when an activated carbon retaining filter different from that used in Example 1 was used, the higher the acid concentration of the aqueous solution containing the hydrochloric acid-containing Sn-containing noble metal catalyst recovery solution, the higher the Pd High recovery rate.

Further, from Tables 3 to 5, the absolute value of the difference between the zeta potential in the 10 mmol / L sodium tetraborate aqueous solution and the zeta potential in the 0.01 mmol / L sodium tetraborate aqueous solution is 25 mV or less, and It can be seen that it is preferable to use an activated carbon holding filter including activated carbon having a pore volume of 1 nm or less and a pore volume of 45 to 500 mm ³ / g in terms of increasing the Pd recovery rate.

  In addition, the results in Examples 2 and 3 (results shown in Tables 4 and 5) are also shown in FIG. The result in Example 2 is indicated by a broken line 32, and the result in Example 3 is indicated by a broken line 33.

  Moreover, even if what uses other activated carbon as activated carbon with which an activated carbon holding filter is equipped, the same tendency is shown. Specifically, activated carbon No. Activated carbon other than 10 Any one of 1 to 11 may be used. Moreover, these activated carbons may be used independently and may be used in combination of 2 or more type. In addition, activated carbon No. No. 10 did not exhibit the above effect of the present invention.

Example 4
Next, the case where the organic compound which has a carboxy group in a molecule | numerator is changed is examined. Specifically, it is the same as Example 1 except that tartaric acid (H ₄ C ₄ O ₆ ) was used as the organic compound having a carboxy group in the molecule. The results are shown in Table 6.

  FIG. 5 is a graph showing the relationship between the acid concentration and the Pd recovery rate. Further, the results in Example 4 (results shown in Table 6) are shown in FIG. FIG. 5 is a graph showing the relationship between the molar ratio of oxalic acid and Sn and the Pd recovery rate.

  As can be seen from Table 6 and FIG. 5, the organic compound having a carboxy group in the molecule as the organic compound having a carboxy group in the molecule is sufficiently high in noble metal, such as tartaric acid, for example. The recovery rate can be realized. That is, it is understood that the organic compound having a carboxy group in the molecule is not particularly limited.

  Formic acid and citric acid also showed the same effect as in Example 1.

  Moreover, even if the Pd—Sn catalyst simulated recovery liquid was adjusted and passed repeatedly several times, the same effect as in Example 1 was exhibited.

DESCRIPTION OF SYMBOLS 11 Catalyst tank 12,13,14 Flush tank 15,24 Recovery tank 16 Adder 17,22 Pump 18,23 Filter 19 Flowmeter 21 Supply tank

Claims (4)

In the method of recovering noble metal from hydrochloric acid acidic Sn-containing noble metal catalyst recovery liquid by activated carbon adsorption,
An addition step of preparing a post-addition solution to which the organic compound is added by adding an organic compound having a carboxy group in the molecule to the aqueous solution containing the recovery solution;
Passing the post-addition liquid through an activated carbon layer containing activated carbon having a pore radius of 45 nm to 500 mm ³ / g with a pore radius of 1 nm or less;
Separating the activated carbon layer from the post-addition liquid that has passed through the activated carbon .
The organic compound is, a method of recovering precious metals characterized by oxalic acid or tartaric der Rukoto. The recovered liquid contains a metal other than the noble metal;
2. The adding step is a step of adding the organic compound such that the content of the organic compound with respect to the other metal in the aqueous solution is 0.3 to 5 times in molar ratio. The precious metal recovery method described in 1.   The method for recovering a noble metal according to claim 1, wherein the noble metal is palladium. The post-addition solution has an acid concentration of less than 0.8 mol / L,
The noble metal recovery method according to claim 1, wherein in the passing step, the noble metal and Sn are separated and adsorbed on the activated carbon layer.

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