JP2006176814A - METHOD FOR COLLECTING Au FROM CYANOGEN-CONTAINING AQUEOUS SOLUTION AND APPARATUS THEREFOR - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for collecting Au from an Au-cyanide-containing aqueous solution, where the collecting efficiency of Au is high, and further, the space of a collecting apparatus therefor can be made small, and to provide an apparatus for realizing the method. <P>SOLUTION: The method for collecting Au from an Au-cyanide-containing raw material aqueous solution comprises: a membrane separation stage where the raw material aqueous solution is separated into a concentrated liquid and a penetrated liquid using a reverse osmosis membrane; and an electrolysis stage where the concentrated liquid is electrolyzed in a first electrolytic cell, so as to collect Au. The half-concentrated liquid obtained in the membrane separation stage is electrolyzed in a second electrolytic cell, as a part of Au in the half-concentrated liquid is recovered, it is recirculated, so as to cause membrane separation, and, at the optional point of time in which the concentration of Au in the half-concentrated liquid increases, it is fed to the first electrolytic cell, thus Au is collected. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method and apparatus for recovering Au from an aqueous solution containing Au and cyanide.

  When Au is plated on electronic parts or mechanical parts, an aqueous solution containing Au and cyan is used as a plating bath. Therefore, a considerable amount of Au that has not been consumed during plating remains together with cyan in the electroplated solution after plating. Therefore, a method for recovering Au as a valuable metal from an aqueous solution containing Au and cyan like an aqueous solution after Au plating has already been proposed.

  For example, in Patent Document 1, as a method for treating cyanide-containing water containing valuable metals, cyanide-containing water is electrolyzed by passing a direct current between the anode and the cathode, and decomposition products other than oxygen and water are not generated. There has been proposed a technique for recovering metals, decomposing cyanide, and decomposing organic matter by oxidizing with an oxidizing agent. In Patent Document 2, as a method for recovering valuable metals from cyan-containing waste liquid, cyan waste liquid containing valuable metals is supplied to an electrolytic cell, insoluble material is used for the anode, and electrolysis is performed while rotating the cathode plate surface. Techniques have been proposed to deposit valuable metals on the surface of the cathode plate.

  However, in such a technique, the Au concentration in the liquid to be processed is not taken into consideration, and therefore, when the Au concentration is low, the Au recovery efficiency is poor and energy is wasted.

In addition, the plated product that is attached to the surface is removed by washing the plated product with water, but the washing water used for the removal also contains a small amount of Au. However, since Au contained in the washing water after removal is still in a low concentration, it has been difficult to efficiently recover Au from such washing water.
JP-A-9-225470 ([Claims], [0004], etc.) JP-A-10-18074 ([Claims] etc.)

  As a result of repeated studies to provide a method for efficiently recovering Au and an apparatus for realizing such a method, the present inventors obtained a raw material aqueous solution containing Au by concentrating it using a reverse osmosis membrane. In other words, based on these findings, the technique of Japanese Patent Application No. 2004-221753 was previously proposed. However, when Au is separated from an aqueous solution containing Au and cyan by using a reverse osmosis membrane, the permeation blocking rate of Au is about 70% at the maximum. Therefore, in order to increase the recovery efficiency of Au, a plurality of reverse osmosis membranes are used. It was necessary to use multiple types of treatments using reverse osmosis membranes. Therefore, there is a problem that the processing equipment becomes large, and there is room for improvement.

  The present invention has been made in view of such circumstances, and an object of the present invention is a method of recovering Au from an aqueous solution containing Au and cyan, which has a high Au recovery efficiency and eliminates the Au recovery device. It is to provide a method that can be made space. Another object of the present invention is to provide an apparatus for realizing such a method.

  When recovering Au from an aqueous solution containing Au and cyan, the present inventors have intensively studied to provide a method and apparatus capable of efficiently recovering Au even when the facility space is limited. As a result, if the raw material aqueous solution to be treated is first subjected to membrane separation using a reverse osmosis membrane, and the resulting concentrated solution is electrolyzed, the Au concentration in the electrolytic solution increases, so the Au recovery efficiency Secondly, if the semi-concentrated liquid in the middle of membrane separation is electrolyzed and a part of Au is recovered, the number of times of membrane separation treatment can be reduced, and the Au recovery device can be saved in space. The inventors have found that the recovery efficiency of Au is improved and completed the present invention.

  That is, the Au recovery method according to the present invention is a method for recovering Au from a raw material aqueous solution containing Au and cyan, and a membrane separation step of separating the raw material aqueous solution into a concentrated solution and a permeated solution using a reverse osmosis membrane. And electrolyzing the concentrated liquid in a first electrolysis tank to recover Au, and electrolyzing the semi-concentrated liquid obtained in the membrane separation process in a second electrolysis tank A part of Au in the semi-concentrated liquid is recovered and recirculated for membrane separation, and sent to the first electrolysis tank as the concentrated liquid at any time when the Au concentration in the semi-concentrated liquid increases. The point is that Au is collected. The semi-concentrated liquid obtained in the membrane separation step is electrolyzed in a second electrolysis tank and recirculated while recovering a part of Au in the semi-concentrated liquid to separate the membrane, What is necessary is just to collect | recover Au by sending to the said 1st electrolysis tank as said concentrate at the time until a liquid volume reaches 1/30 times the liquid volume of the said raw material aqueous solution.

  According to the Au recovery method of the present invention, the permeate can be used as plating process water. In the method of the present invention, it is preferable that an aqueous solution containing hypochlorite ions is added to and mixed with the raw material aqueous solution and then treated with dehypochlorous acid before being supplied to the membrane separation step.

  The Au recovery device according to the present invention is a device for recovering Au from a raw material aqueous solution containing Au and cyan, a supply means for supplying the raw material aqueous solution to a membrane separator, and the raw material aqueous solution as a reverse osmosis membrane. A separator for separating the concentrated solution and the permeate using a first electrolyzer for recovering Au by electrolyzing the concentrated solution, and a path for extracting a semi-concentrated solution from the membrane separator; A second electrolysis apparatus for recovering Au by electrolyzing the extracted semi-concentrated liquid, and a path for returning the electrolyzed liquid after electrolysis by the second electrolysis apparatus to the membrane separation apparatus It has a gist in that it includes.

  The supply means is provided with a means for adding an aqueous solution containing hypochlorite ions, and between the supply means and the membrane separator, a dehydration treatment for subjecting the raw material aqueous solution to a hypochlorous acid treatment. It is preferable to provide a chlorous acid apparatus.

  According to the Au recovery method of the present invention, the efficiency of Au recovery from a cyanate-containing aqueous solution can be improved by combining membrane separation treatment with a reverse osmosis membrane and electrolysis of a semi-concentrated liquid during the membrane separation treatment. In addition, a space-saving Au recovery device can be provided. Moreover, according to this invention, the apparatus for implement | achieving such a method can be provided.

In the membrane separation process using a reverse osmosis membrane, about 70% by mass of the total amount of Au contained in the raw material aqueous solution can be separated to the concentrate side, which can be recovered by electrolysis, but the remaining 30% by mass The degree leaks to the permeate side. The reason why about 30% by mass of Au permeates the reverse osmosis membrane is not completely understood, but a compound of Au and cyan (specifically, a gold cyanide complex: [Au (CN) ₂ ^- molecular structures, etc.) are considered present inventors to be one of the causes is linear. Since noble metals other than Au generally do not permeate the reverse osmosis membrane, it is considered that this reverse osmosis membrane permeation phenomenon is unique to Au, and the permeability of Au to the reverse osmosis membrane changes the type of reverse osmosis membrane. But it wasn't too much. Therefore, when the raw material aqueous solution containing Au and cyan is processed, when the membrane separation step is performed only once, about 30% by mass of the total amount of Au contained in the raw material aqueous solution is processed as a waste liquid.

  For this reason, the technique previously proposed by the present inventors (see Japanese Patent Application No. 2004-2121753) collects Au that has permeated the reverse osmosis membrane in the first membrane separation step (that is, Au in the permeate). In order to achieve this, it is recommended that the membrane separation process be performed again on the permeate. However, in order to perform the membrane separation process twice or more, two or more membrane separation apparatuses are required, which causes a problem of pressing the processing facility space.

  Therefore, the present inventors have repeatedly studied aiming at space saving of the processing equipment. As a result, if the semi-concentrated liquid in the middle of the membrane separation process is electrolyzed and a part of Au is collected in advance, the Au concentration in the liquid to be processed in the membrane separation process can be reduced, so that the reverse osmosis membrane The absolute amount of Au that permeates and leaks to the permeate side can be reduced. As a result, the recovery efficiency of Au can be increased, and it is not necessary to provide a plurality of membrane separation devices, and the processing equipment can be saved in space. Revealed. Hereinafter, the Au recovery method according to the present invention will be described.

  The Au recovery method according to the present invention is a method of recovering Au from a raw material aqueous solution containing Au and cyan, and a membrane separation step of separating the raw material aqueous solution into a concentrated solution and a permeated solution using a reverse osmosis membrane; An electrolysis process in which the concentrated liquid is electrolyzed in a first electrolysis tank to recover Au, and the semi-concentrated liquid obtained in the membrane separation process is electrolyzed in a second electrolysis tank to be semi-concentrated A part of Au in the liquid is recovered and recirculated to separate the membrane, and sent to the second electrolysis tank as the concentrated liquid at any time when the Au concentration in the semi-concentrated liquid increases. It is characterized in that it is collected. The semi-concentrated liquid refers to a liquid that is recycled in the membrane separation step, and refers to a liquid before being supplied to the first electrolysis tank as a concentrated liquid.

In the Au recovery method according to the present invention, a raw material aqueous solution containing Au and cyan is subjected to membrane separation using a reverse osmosis membrane, and the resulting concentrated solution is electrolyzed in a first electrolysis tank, whereby Au is separated from the raw material aqueous solution. Recover. By electrolyzing the concentrated liquid, the Au concentration in the concentrated liquid is increased, so that the Au recovery efficiency can be increased. In general, it is known that when an aqueous solution containing cyanide is electrolyzed, cyanide ions in the solution are decomposed into CO ₂ and N _2, but the same decomposition treatment is performed in the method of the present invention. .

  In the present invention, it is important to recover a part of Au in advance by electrolyzing the semi-concentrated liquid during the membrane separation treatment. That is, when separating a raw material aqueous solution into a concentrated solution and a permeated solution using a reverse osmosis membrane, the raw material aqueous solution is gradually concentrated by circulating and passing through the reverse osmosis membrane several times. In this circulation, Au is recovered by electrolyzing the semi-concentrated liquid. In this way, the absolute amount of Au permeating the reverse osmosis membrane can be reduced by sequentially recovering Au in the semi-concentrated liquid and lowering the Au concentration.

  The semi-concentrated liquid concentrated by circulating a plurality of reverse osmosis membranes is supplied to the first electrolysis tank at any time when the Au concentration in the semi-concentrated liquid is increased, and is electrolyzed to recover Au. To do. The time when the Au concentration in the semi-concentrated liquid increases cannot be uniformly defined because it is necessary to consider the Au concentration in the electrolytic solution (that is, the concentrated liquid) in the electrolysis step after the membrane separation step. Considering the working time and cost required for concentration, the Au concentration in the semi-concentrated liquid is more than 1 time and less than 30 times (more preferably more than 1 time and less than 10 times) with respect to the Au concentration of the raw material aqueous solution. It is good to be the time to become. The reason for setting the arbitrary time point is that it is preferable to adjust the degree of concentration by the Au concentration or the like of the raw material aqueous solution.

  However, since it is difficult to measure the Au concentration in the semi-concentrated liquid in real time, when the Au concentration in the semi-concentrated liquid increases, the amount of the semi-concentrated liquid is 1 with respect to the amount of the raw material aqueous solution. / The time until the amount reaches 30 times. This is because it is not practical to concentrate the amount of the semi-concentrated liquid to 1/30 times or more the amount of the raw material aqueous solution. The lower limit is not particularly limited, but if the amount of the semi-concentrated liquid does not reach 1/5 times the amount of the raw material aqueous solution, the Au concentration in the liquid is too low and it is uneconomical to electrolyze. Become. Particularly preferably, the semi-concentrated liquid may be supplied to the first electrolysis tank as the concentrated liquid when it reaches 1/10 times the amount of the raw aqueous solution.

  The increase in the Au concentration in the semi-concentrated liquid circulated in the membrane separation process is performed by, for example, providing a flow meter on the path before and after the second electrolysis tank to measure the amount of the semi-concentrated liquid, The amount and the amount of permeated liquid separated in the membrane separation step are determined by measuring each with a flow meter.

Conditions for electrolysis during the membrane separation process are not particularly limited, and known conditions can be adopted. For example, the voltage during electrolysis may be about 0.1 to 20 V, and the current density may be about 0.0001 to 0.5 A / cm ² . As the anode, for example, an insoluble metal electrode (DSE) for aqueous solution electrolysis manufactured by Permerek Electrode Co., Ltd. may be used. For example, a Ti electrode or a SUS electrode may be used as the cathode.

What is necessary is just to employ | adopt the electrolysis conditions in the electrolysis process after a membrane separation process, the voltage at the time of electrolysis is about 0.1-20V, and a current density is about 0.0001-0.5 A / cm < ² >. That's fine. As the anode, for example, DSE manufactured by Permerek Electrode Co., Ltd. may be used. For example, a Ti electrode or a SUS electrode may be used as the cathode.

  In the above description, the configuration in which the tank for electrolyzing the concentrated liquid (first electrolysis tank) and the tank for electrolyzing the semi-concentrated liquid (second electrolysis tank) has been described, but the facility space is limited. In order to save space, the second electrolysis tank may also serve as the first electrolysis tank. That is, when the raw material aqueous solution is subjected to membrane separation into a concentrated solution and a permeated solution using a reverse osmosis membrane, the semi-concentrated solution in the middle of the membrane separation is electrolyzed in the same electrolysis tank to recover Au from the semi-concentrated solution. The concentrate obtained after recirculation and membrane separation and recovering Au in the semi-concentrated liquid may be discharged out of the system as waste liquid after recovering Au to the desired concentration in the same electrolysis tank. .

  In the method of the present invention, since the membrane separation process using a reverse osmosis membrane and the electrolysis in the middle of the membrane separation process are combined, one step is sufficient for the membrane separation treatment step, and one step for the membrane separation treatment step. By doing so, it is possible to save the space of the equipment. However, since a small amount of Au is also contained in the permeate, when the Au in the raw material aqueous solution is recovered to the limit, the permeate is further concentrated using a separate reverse osmosis membrane. It is desirable to recover Au contained in the permeate by electrolyzing the concentrated solution a.

  The raw material aqueous solution to be treated in the present invention is an aqueous solution containing Au and cyanide. For example, a plated solution after Au plating is applied to an electronic part or a machine part, and a water washing after washing the plated product. Such as water.

  The Au concentration in the raw material aqueous solution is not limited, but considering the working time and cost required for performing the membrane separation treatment, the Au concentration in the raw material aqueous solution is preferably 1000 ppm or less (not including 0 ppm). This is because the lower the concentration of Au contained in the raw material aqueous solution, the higher the effect obtained by concentrating by membrane separation and then electrolyzing. A more preferable Au concentration is about 300 ppm or less (not including 0 ppm). However, considering the operation cost of Au recovery, it is recommended that the Au concentration in the raw material aqueous solution is 1 ppm or more.

  Of course, even if the Au concentration in the raw material aqueous solution exceeds 1000 ppm, the Au recovery method and apparatus according to the present invention can be employed. However, when the Au concentration in the aqueous solution to be treated exceeds 1000 ppm, the aqueous solution is electrolyzed to collect Au in advance, and the electrolyzed solution after electrolysis is used as the raw material aqueous solution of the present invention. preferable.

  By the way, the raw material aqueous solution often contains, for example, a buffer or a surfactant in addition to Au and cyan. The buffering agent is added to adjust the pH of the plating bath, and there are an organic type and an inorganic type. Examples of the organic buffer (organic) include citric acid and formic acid, and examples of the inorganic buffer (inorganic) include phosphoric acid. On the other hand, the surfactant is added in order to improve the wettability of the plating substrate or prevent the generation of mist (mist) in the plating process, and examples thereof include fatty acid sulfonates and alcohol sulfates. Hereinafter, these buffers and surfactants may be referred to as “buffers and the like”.

  If these buffering agents are contained in the raw material aqueous solution, the buffering agent will also be mixed into the spent solution after electrolysis and recovery of Au. There is a need to process. For this reason, problems such as an increase in the scale of facilities have occurred.

  On the other hand, in the method of the present invention, since the raw material aqueous solution is separated into the concentrate and the permeate by the membrane separator, most of the buffering agent and the like is separated to the concentrate side and is hardly contained on the permeate side. . Therefore, the permeate can be used as plating process water. The plating process water means water used in the plating process, for example, water constituting a plating bath or water used for washing a product after plating, and the permeate is used instead of such water. be able to. The permeate may be returned to the raw material aqueous solution side as necessary, mixed with the raw material aqueous solution, and reprocessed.

  It is preferable that an aqueous solution containing hypochlorite ions is added to the raw material aqueous solution, mixed, and then subjected to dehydrochlorite treatment before being supplied to the membrane separation step. In other words, if the raw material aqueous solution is stored in a storage tank or the like, bacteria may propagate. When a raw material aqueous solution containing such bacteria is supplied to the reverse osmosis membrane, the bacteria adhere to the reverse osmosis membrane and promote membrane deterioration. However, if the raw material aqueous solution and the aqueous solution containing hypochlorite ions are mixed, the bacteria existing in the raw material aqueous solution can be prevented from growing and further killed.

  However, if a raw material aqueous solution containing hypochlorite ions is separated using a reverse osmosis membrane, the reverse osmosis membrane deteriorates due to the oxidation of hypochlorite ions, so the raw material aqueous solution after killing bacteria is The membrane separation treatment is performed after the dehydrochlorous acid treatment.

As an aqueous solution containing hypochlorite ions, (a) a commercially available hypochlorous acid aqueous solution, (b) an aqueous solution obtained by electrolyzing an aqueous solution to which a soluble inorganic chloride is added, (c) reverse osmosis An aqueous solution obtained by adding a soluble inorganic chloride to the liquid that has permeated the membrane and electrolyzing the liquid can be used. The soluble inorganic chloride is one that is ionized and dissolved in the electrolytic solution to generate Cl ^- ions. The kind of the soluble inorganic chloride is not particularly limited, and examples thereof include NaCl and KCl. In consideration of ease of addition and cost, NaCl is optimal.

  The hypochlorite ion concentration in the aqueous solution containing hypochlorite ions is not particularly limited, and for example, a concentration of about 0.01 to 15% by mass can be used.

  The amount of the aqueous solution containing hypochlorite ions to be added to the raw material aqueous solution is not limited so long as bacteria in the raw material aqueous solution are killed, and the addition amount is not limited, but includes the raw aqueous solution and hypochlorite ions. What is necessary is just to contain about 0.0001-5 mass% of hypochlorite ion in the liquid after mixing with aqueous solution.

In the method of the present invention, in order to increase the electrolysis efficiency in the electrolysis step, it is preferable to coexist Cl 2 ⁻ in the electrolysis step in the first electrolysis tank. This is because, if Cl ⁻ is present during electrolysis, the amount of electrolyte increases, so that current easily flows. In addition, when electrolysis is performed in a coexistence system of Cl ⁻ , hypochlorite ions (ClO ⁻ ) are generated, and these hypochlorite ions also indirectly oxidize cyan ions, so that they can also serve as cyanide treatment.

In electrolysis process, Cl ^- when the coexisting is an electrodeposition already liquid after the electrolysis step was mixed with the raw aqueous solution, and then be supplied from the processing de hypochlorite to membrane separation step preferable.

  The electrolyzed liquid after the electrolysis step may be discharged out of the system after performing an appropriate treatment as necessary, and the electrolyzed liquid may contain a small amount of Au. Au may be recovered using an exchange resin or the like. Moreover, it may be returned to the raw material aqueous solution and mixed with the raw material aqueous solution.

  Next, an apparatus for realizing the Au recovery method according to the present invention will be described. An Au recovery device according to the present invention is a device for recovering Au from a raw material aqueous solution containing Au and cyan, a supply means for supplying the raw material aqueous solution to a membrane separation device, the raw material aqueous solution using a reverse osmosis membrane Including a membrane separation device that separates the concentrate into a permeate, a first electrolysis device that electrolyzes the concentrate to recover Au, and a path for extracting the semi-concentrate from the membrane separator; A second electrolysis apparatus for recovering Au by electrolyzing the extracted semi-concentrated liquid, and a path for returning the electrolyzed liquid after electrolysis by the second electrolysis apparatus to the membrane separation apparatus There is a feature in including. This apparatus will be described in more detail with reference to the drawings. However, the present invention is not limited to this, and can be implemented with appropriate modifications within a range that can be adapted to the purpose described above and below. They are all included in the technical scope of the present invention.

  FIG. 1 is a schematic explanatory view showing a configuration example of an Au recovery apparatus according to the present invention. In FIG. 1, 51 is a supply means, 52 is a membrane separator, 53 is a first electrolyzer, 54 is a second electrolyzer, 61 and 62 are valves, and 100 to 105 are paths.

  The supply means 51 includes a supply path for supplying the raw material aqueous solution to the membrane separation device 52 and a raw material supply power (for example, a pump) (not shown). A valve 61 is provided on the path of the supply means 51, and the raw material aqueous solution is supplied to the membrane separation device 52 by the supply means 51 by opening the valve 61. The aqueous raw material solution supplied to the membrane separator 52 is separated into a concentrate and a permeate by a reverse osmosis membrane (not shown) in the membrane separator 52.

  At this time, the semi-concentrated liquid that has passed through the reverse osmosis membrane is supplied to the second electrolyzer 54 through the path 103 and collects Au by electrolysis. The collected Au is taken out of the system through the path 104. On the other hand, the spent solution after being electrolyzed by the second electrolyzer 54 is returned to the membrane separator through the path 105 and subjected to the membrane separation process again. That is, if the raw material aqueous solution is membrane-separated only once by the reverse osmosis membrane, the concentration is insufficient. Therefore, a recirculation path is provided for returning the semi-concentrated liquid that has passed through the reverse osmosis membrane to the upstream side of the membrane separation device 52, Concentrate through osmotic membrane. In the present invention, Au is recovered from the semi-concentrated liquid during the circulation. That is, the raw material aqueous solution supplied to the membrane separation device 52 is gradually concentrated by circulating the cycle of the membrane separation device 52 → the path 103 → the second electrolysis apparatus 54 → the path 105, and Au is sequentially recovered. is there.

  Next, at any time when the Au concentration in the semi-concentrated liquid increases, the valve 62 provided on the path 100 is opened to supply the semi-concentrated liquid as the concentrated liquid to the electrolyzer 53, and by electrolysis Collect Au. The collected Au is taken out of the system through the path 101. On the other hand, the electrolyzed solution after the electrolysis is discharged out of the system from a route not shown.

  According to the configuration shown in FIG. 1, since Au is sequentially recovered during the concentration of the raw material aqueous solution, the concentration of Au in the liquid separated by the reverse osmosis membrane can be reduced, and a plurality of membrane separation devices are not provided. In both cases, Au can be efficiently recovered, and the equipment can be saved in space.

  When the Au concentration in the semi-concentrated liquid increases, a flow meter is provided on the path 103, the path 105, and the path 102 to measure the liquid volume of the semi-concentrated liquid or the permeated liquid. It may be determined in consideration of.

  The permeate generated by concentrating the raw material aqueous solution is sequentially discharged out of the system through the path 102. This permeate may be discharged after appropriate treatment or may be used as plating process water.

  In the membrane separator 52, the membrane may be separated by pressurizing to about 1 to 6 MPa. Preferably, it is about 4-6 MPa. As the reverse osmosis membrane used in the membrane separator 52, for example, polyamide reverse osmosis membrane (high pressure type) manufactured by filmtec, cellulose acetate reverse osmosis membrane (high pressure type) manufactured by Toyobo Co., Ltd., or the like can be used.

  FIG. 2 is a schematic explanatory view showing another configuration example of the Au recovery apparatus according to the present invention. The same parts as those in FIG. 2 are denoted by the same reference numerals to avoid redundant description. In FIG. 2, 55 is a second membrane separation device, 56 is a third electrolysis device, and 106 to 108 are paths.

  In the configuration shown in FIG. 2, the permeate separated by the membrane separation device 52 is supplied to the second membrane separation device 55 through the path 102, where the concentrated solution a and the permeate are fed by a reverse osmosis membrane (not shown). separated into b. The concentrated liquid a is supplied to the third electrolyzer 56 via the path 106 and collects Au by electrolysis. The collected Au is taken out through the path 107. The electrolyzed liquid after the electrolysis in the third electrolyzer 56 is discharged out of the system through a path (not shown).

  According to the configuration shown in FIG. 2, the permeate can be further separated by the second membrane separation device 55 and concentrated, and then electrolyzed by the third electrolysis device 56, whereby Au can be recovered to the limit, and the entire system can be recovered. As a result, the Au recovery efficiency increases.

  On the other hand, the permeate b separated by the second membrane separation device 55 is subjected to membrane separation processing by the membrane separation device 52 and the second membrane separation device 55, respectively. Since the electrolysis in the second electrolyzer 54 is combined, the Au concentration in the permeate b is considerably low. Therefore, even if the permeate b is discharged out of the system, there is little influence on the Au recovery efficiency of the entire system. This permeate b may be discharged after appropriate treatment or may be used as plating process water.

  In the second membrane separation device 55 as well as the membrane separation device 52, the concentrated liquid supplied to the second membrane separation device 55 passes through the reverse osmosis membrane in the second membrane separation device 55 a plurality of times. In this way, it is circulated and concentrated (circulation path not shown). At this time, Au may be sequentially recovered by electrolysis during concentration.

  The reverse osmosis membrane used in the second membrane separation device 55 may be the same type as the reverse osmosis membrane used in the membrane separation device 52, but the permeate to be separated in the second membrane separation device 55 is Since the membrane separation has already been performed once by the membrane separation device 52, the osmotic pressure of the permeate is relatively smaller than the osmotic pressure of the raw material aqueous solution to be separated by the membrane separation device 52. Therefore, the reverse osmosis membrane used in the second membrane separation device 55 can be of a lower pressure type than the reverse osmosis membrane used in the membrane separation device 52, which contributes to cost reduction.

  In the second membrane separation device 55, the membrane may be separated by pressurizing to about 0.1 to 1 MPa. Examples of the reverse osmosis membrane used in the second membrane separation device 55 include a polyamide-based reverse osmosis membrane (for example, “LF10 (trade name)”: low pressure type) manufactured by Nitto Denko Matex Co., Ltd. and a polyamide-based reverse membrane manufactured by filmtec. An osmosis membrane (low pressure type), a cellulose acetate reverse osmosis membrane (low pressure type) manufactured by Daicel Corporation, and the like can be used.

  In the configuration shown in FIGS. 1 and 2, the supply means 51 is provided with means (not shown) for adding an aqueous solution containing hypochlorite ions, and between the supply means 51 and the membrane separation device 52. It is preferable to provide a dehydrochlorous acid device (not shown) for treating the raw aqueous solution with dehydrochlorous acid.

  Although the method of the dehydrochlorous acid process performed with a dehypochlorous acid apparatus is not specifically limited, For example, it is easy to add sodium sulfite etc. to the raw material aqueous solution as a chemical | medical agent for dehydrochlorous acid.

By the way, in the electrolysis process, it is recommended to electrolyze in the presence of Cl 2 ⁻ in order to increase the electrolysis efficiency. Therefore, it is preferable to add a soluble inorganic chloride addition means to the first electrolyzer 53 or the third electrolyzer 56 in the configuration shown in FIGS. The soluble inorganic chloride is not particularly limited as long as it dissolves by ionization in an electrolytic solution and generates Cl 2 ⁻ ions, and examples thereof include NaCl and KCl. In view of ease of addition and cost, NaCl is optimal. The amount of the soluble inorganic chloride added to the electrolytic solution is not particularly limited, but may be added so as to be 0.0001 to 5% by mass.

In the case where a soluble inorganic chloride addition means is attached to the electrolysis apparatus and the electrolyzed liquid electrolyzed in the presence of Cl 2 ⁻ is returned to the supply means 51, a raw material aqueous solution is provided between the supply means 51 and the membrane separator 52. In order to treat hypochlorous acid, it is necessary to provide a hypochlorous acid apparatus (not shown).

  The permeated liquid (permeated liquid b) and the charged liquid may be supplied to an ion exchange tank (not shown) to recover Au contained in a trace amount in the liquid. As the anion exchange resin filled in the ion exchange tank, for example, “SA10A (trade name)” or “SA11A (trade name)” manufactured by Mitsubishi Chemical Corporation can be suitably used.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the following examples are not intended to limit the present invention, and can be implemented with appropriate modifications within a range that can meet the gist of the preceding and following descriptions. They are all included in the technical scope of the present invention.

Example 1
300 L of an aqueous solution containing Au: 150 ppm, cyan: 15 ppm, and bacteria: 14 ppm was used as a raw material aqueous solution, and Au was recovered from the raw material aqueous solution using the Au recovery apparatus shown in FIG. This raw material aqueous solution contains citric acid: 800 ppm and phosphoric acid: 300 ppm as buffering agents. In addition, the said bacterium refers to the suspended particle part whose maximum length is 1 μm or more (the same applies hereinafter). The recovery process, membrane separation treatment conditions and electrolysis treatment conditions are as follows.

<Recovery process>
The raw material aqueous solution was supplied to the membrane separation device 52 by the supply means 51 and separated into a concentrated solution and a permeated solution. At this time, the semi-concentrated liquid that passed through the reverse osmosis membrane provided in the membrane separator 52 was extracted from the path 103 and supplied to the second electrolyzer 54, and electrolyzed to recover Au. The collected Au was taken out from the path 104. On the other hand, the electrolyzed solution after being electrolyzed by the second electrolyzer 54 was returned to the membrane separator 52 through the path 105. When the Au concentration in the semi-concentrated liquid is increased through the cycle of the membrane separation device 52 → the path 103 → the second electrolyzer 54 → the path 105, the first electrolyzer 53 passes through the path 100 as a concentrated liquid. And recovered by electrolysis. The collected Au was taken out from the path 101. The time when the Au concentration in the semi-concentrated liquid increases is the time when the amount of the semi-concentrated liquid reaches 1/10 times the amount of the raw material aqueous solution, and the flow meter provided on the path 102 The liquid volume of the permeated liquid was measured (not shown), and this measurement result and the liquid volume of the raw material aqueous solution were judged.

<Membrane separation treatment conditions>
In the membrane separator 52, a polyamide reverse osmosis membrane (high pressure type) manufactured by filmtec was used as the reverse osmosis membrane, and the raw material aqueous solution was supplied to the membrane at a pressure of 5.0 MPa. The permeate outflow amount at this time was 3.0 L / min, and it was concentrated to 1/10 times the amount of the raw material aqueous solution.

<Electrolysis conditions>
In the first electrolyzer 53 and the second electrolyzer 54, DSE manufactured by Permerek Electrode Co., Ltd. was used as the anode, and Ti electrode was used as the cathode. The voltage during electrolysis was 2.5 V, and the current density was 0.001 A / cm ² . The first electrolyzer and the second electrolyzer are not provided with a soluble inorganic chloride addition means.

  The concentrations of Au, cyan, citric acid, and phosphoric acid at each site shown in FIG. 1 were measured, and the results are shown in Table 1 below. The amount of liquid in each part is also shown.

  As a result, the amount of Au contained in the raw material aqueous solution is 45 g, whereas the amount of Au recovered from the path 101 is 19.3 g, and the amount of Au recovered from the path 104 is 22.5 g. According to the Au recovery method, 92.9% Au was recovered from an aqueous solution with an Au concentration of 150 ppm. The electrolysis efficiency in the first electrolyzer 53 was 3.8%, and the electrolysis efficiency in the second electrolyzer 54 was 4.0%.

Example 2
300 L of an aqueous solution containing Au: 850 ppm, cyan: 85 ppm, and bacteria: 40 ppm was used as a raw material aqueous solution, and Au was recovered from the raw material aqueous solution using the Au recovery device shown in FIG. This raw material aqueous solution contains citric acid: 3000 ppm and phosphoric acid: 900 ppm as buffering agents. The recovery process, membrane separation treatment conditions and electrolysis treatment conditions are as follows.

<Recovery process>
The raw material aqueous solution was supplied to the membrane separation device 52 by the supply means 51 and separated into a concentrated solution and a permeate. At this time, the semi-concentrated liquid that passed through the reverse osmosis membrane provided in the membrane separator 52 was extracted from the path 103 and supplied to the second electrolyzer 54, and electrolyzed to recover Au. The collected Au was taken out from the path 104. On the other hand, the electrolyzed solution after being electrolyzed by the second electrolyzer 54 was returned to the membrane separator 52 through the path 105. When the Au concentration in the semi-concentrated liquid is increased through the cycle of the membrane separation device 52 → the path 103 → the second electrolyzer 54 → the path 105, the first electrolyzer 53 passes through the path 100 as a concentrated liquid. And recovered by electrolysis. The collected Au was taken out from the path 101. The time when the Au concentration in the semi-concentrated liquid increases is the time when the amount of the semi-concentrated liquid reaches 1/10 times the amount of the raw material aqueous solution, and the flow meter provided on the path 102 The liquid volume of the permeated liquid was measured (not shown), and this measurement result and the liquid volume of the raw material aqueous solution were judged.

  The permeate was supplied to the second membrane separation device 55 through the path 102 and separated into the concentrate a and the permeate b. The concentrated liquid a was supplied to the third electrolyzer 56 through the path 106 and electrolyzed to recover Au. The collected Au was taken out from the path 107.

<Membrane separation treatment conditions>
In the membrane separator 52, a polyamide reverse osmosis membrane (high pressure type) manufactured by filmtec was used as the reverse osmosis membrane, and the raw material aqueous solution was supplied to the membrane at a pressure of 5.0 MPa. The permeate outflow amount at this time was 3.0 L / min, and it was concentrated to 1/10 times the amount of the raw material aqueous solution. In the second membrane separation device 55, a polyamide-based reverse osmosis membrane (“LF10 (trade name)”: low pressure type) manufactured by Nitto Denko Matex Co., Ltd. is used as the reverse osmosis membrane, and the permeate is converted into a membrane at a pressure of 1.0 MPa. Supplied. The permeate outflow at this time was 1.5 L / min, and it was concentrated to 1/10 times the amount of permeate.

<Electrolysis conditions>
In the first electrolyzer 53, DSE manufactured by Permerek Electrode Co., Ltd. was used as the anode, and Ti electrode was used as the cathode. The voltage during electrolysis was 2.5 V, and the current density was 0.002 A / cm ² . In the second electrolyzer 54, DSE manufactured by Permerek Electrode Co., Ltd. was used as the anode, and a Ti electrode was used as the cathode. The voltage during electrolysis was 2.5 V, and the current density was 0.001 A / cm ² . In the 3rd electrolysis apparatus 56, DME by Permerec Electrode Co., Ltd. was used as an anode, and Ti electrode was used as a cathode. The voltage during electrolysis was 9 V, and the current density was 0.001 A / cm ² . In addition, the said 1st-3rd electrolyzer is not attached with the soluble inorganic chloride addition means.

  The concentrations of Au, cyan, citric acid, and phosphoric acid at each site shown in FIG. 2 were measured, and the results are shown in Table 2 below. The amount of liquid in each part is also shown.

  As a result, the amount of Au contained in the raw material aqueous solution was 255 g, whereas the amount of Au recovered from the path 101 was 109.5 g, the amount of Au recovered from the path 104 was 122 g, and the Au recovered from the path 107 The amount was 16.6 g, and according to the Au recovery method of the present invention, 97.3% Au could be recovered from an aqueous solution with an Au concentration of 850 ppm. The electrolysis efficiency in the first electrolyzer 53 is 6.8%, the electrolysis efficiency in the second electrolyzer 54 is 6.7%, and the electrolysis efficiency in the third electrolyzer 56 is 3.6%. It was.

Comparative Example 1
In Example 1 above, except that the second electrolysis tank 54 and the path 104 shown in FIG. 1 are not provided, the same Au recovery apparatus as in Example 1 is used, and the raw material aqueous solution is Au from the same conditions as in Example 1 above. Was recovered. The path 103 and the path 105 are connected.

  The concentrations of Au, cyan, citric acid, and phosphoric acid at each site shown in FIG. 1 were measured, and the results are shown in Table 3 below. The amount of liquid in each part is also shown.

  As a result, the amount of Au contained in the raw material aqueous solution is 45 g, whereas the amount of Au recovered from the path 101 is 31.4 g. According to this method, only 69.7% Au can be recovered from an aqueous solution having an Au concentration of 150 ppm. The electrolysis efficiency in the first electrolyzer 53 was 4.8%.

  Comparing the result of Comparative Example 1 with the result of Example 1, the efficiency of Au recovery can be increased by electrolyzing the semi-concentrated liquid in the middle of the membrane separation process as in Example 1.

Comparative Example 2
In Example 2, the same Au recovery as in Example 2 was performed except that the raw material aqueous solution used in Example 1 was used as the raw material aqueous solution and the second electrolysis tank 54 and the path 104 shown in FIG. 2 were not provided. Au was collect | recovered from raw material aqueous solution using the apparatus. However, the electrolysis treatment conditions were changed as follows. The path 103 and the path 105 are connected.

<Electrolysis conditions>
In the first electrolyzer 53, DSE manufactured by Permerek Electrode Co., Ltd. was used as the anode, and Ti electrode was used as the cathode. The voltage during electrolysis was 2.5 V, and the current density was 0.001 A / cm ² . In the 3rd electrolysis apparatus 56, DME by Permerec Electrode Co., Ltd. was used as an anode, and Ti electrode was used as a cathode. The voltage during electrolysis was 12 V, and the current density was 0.001 A / cm ² . The first electrolyzer 53 and the third electrolyzer 56 used here are not provided with a soluble inorganic chloride addition means.

  The concentrations of Au, cyan, citric acid, and phosphoric acid at each site shown in FIG. 2 were measured, and the results are shown in Table 4 below. The amount of liquid in each part is also shown.

  As a result, the amount of Au contained in the raw material aqueous solution is 45 g, whereas the total amount of Au recovered from the paths 101 and 107 is 41.8 g. According to this method, 92.9% Au can be recovered from an aqueous solution having an Au concentration of 150 ppm. The electrolysis efficiency in the first electrolyzer 53 was 4.8%, and the electrolysis efficiency in the third electrolyzer 56 was 3.0%.

  When the results of Comparative Example 2 and the results of Example 1 were compared, the Au recovery efficiency was 92.9%, which was the same. Therefore, when the semi-concentrated liquid in the middle of the membrane separation process is electrolyzed as in Example 1, the Au recovery efficiency can be increased even if there is only one membrane separation processing apparatus, and the space can be saved.

Comparative Example 3
In Example 2 described above, Au was recovered from the raw material aqueous solution using the same Au recovery apparatus as in Example 2 except that the second electrolysis tank 54 and the path 104 shown in FIG. 2 were not provided. However, the electrolysis treatment conditions were changed as follows. The path 103 and the path 105 are connected.

<Electrolysis conditions>
In the first electrolyzer 53, DSE manufactured by Permerek Electrode Co., Ltd. was used as the anode, and Ti electrode was used as the cathode. The voltage during electrolysis was 2.5 V, and the current density was 0.003 A / cm ² . In the 3rd electrolysis apparatus 56, DME by Permerec Electrode Co., Ltd. was used as an anode, and Ti electrode was used as a cathode. The voltage during electrolysis was 8.0 V, and the current density was 0.001 A / cm ² . The first electrolyzer 53 and the third electrolyzer 56 used here are not provided with a soluble inorganic chloride addition means.

  The concentrations of Au, cyanide, citric acid, and phosphoric acid at each site shown in FIG. 2 were measured, and the results are shown in Table 5 below. The amount of liquid in each part is also shown.

  As a result, the amount of Au contained in the raw material aqueous solution is 255 g, whereas the total amount of Au recovered from the paths 101 and 107 is 226.7 g. According to this method, 88.9% Au can be recovered from an aqueous solution having an Au concentration of 850 ppm. The electrolysis efficiency in the first electrolyzer 53 was 7.1%, and the electrolysis efficiency in the third electrolyzer 56 was 5.3%.

  Comparing the results of Comparative Example 3 with the results of Example 2, the efficiency of Au recovery can be increased by electrolyzing the semi-concentrated liquid in the middle of the membrane separation process as in Example 2.

Example 3
In Example 1 described above, Au was recovered under the same conditions except that the supply means 51 was provided with a means for adding an aqueous solution containing hypochlorite ions.

  That is, an aqueous solution containing hypochlorite ions is added to the raw material aqueous solution so that the hypochlorite ion concentration in the supply means 51 is 0.0005% by mass, and a dechlorite treatment apparatus (not shown). After being treated with dehydrochlorous acid, the membrane was supplied to the membrane separator 52. As the hypochlorous acid treatment apparatus, a sodium sulfite addition apparatus was used.

  A mixture of the above aqueous solution containing hypochlorite ions and the raw material aqueous solution is allowed to stand at room temperature for 1 day, and then the particles having a maximum length of 1 μm or more are collected from the particles suspended in the solution, and mass measurement is performed. The bacterial concentration was measured by As a result, the bacterial concentration in the liquid was 1 ppm. The reason for the decrease in the bacterial concentration is thought to be the death of bacteria (concentration: 14 ppm) contained in the raw material aqueous solution by hypochlorite ions.

It is the schematic explanatory drawing which showed the example of a structure of Au collection | recovery apparatus which concerns on this invention. It is the schematic explanatory drawing which showed the other structural example of Au collection | recovery apparatus which concerns on this invention.

Explanation of symbols

51: Supply means 52: Membrane separation device 53: First electrolysis device 54: Second electrolysis device 55: Second membrane separation device 56: Third electrolysis device 61-62: Valves 100-108: Path

Claims (6)

A method for recovering Au from a raw material aqueous solution containing Au and cyanide,
A membrane separation step of separating the raw material aqueous solution into a concentrate and a permeate using a reverse osmosis membrane, and an electrolysis step of recovering Au by electrolyzing the concentrate in a first electrolysis tank,
The semi-concentrated liquid obtained in the membrane separation step is electrolyzed in a second electrolysis tank and recirculated while recovering a part of Au in the semi-concentrated liquid to separate the membrane, A method for recovering Au from a cyanate-containing aqueous solution, wherein Au is recovered by sending it to the first electrolysis tank as the concentrated liquid at an arbitrary time when the Au concentration increases.   The method according to claim 1, wherein the semi-concentrated liquid is sent to the first electrolysis tank as the concentrated liquid until the amount of the semi-concentrated liquid reaches 1/30 times the amount of the raw aqueous solution.   The method according to claim 1, wherein the permeate is used as plating process water.   The method according to any one of claims 1 to 3, wherein an aqueous solution containing hypochlorite ions is added to and mixed with the raw material aqueous solution, followed by dehydrochlorous acid treatment, and then supplied to the membrane separation step. An apparatus for recovering Au from a raw material aqueous solution containing Au and cyanide,
Supply means for supplying the raw material aqueous solution to the membrane separator;
A membrane separation device for separating the raw material aqueous solution into a concentrate and a permeate using a reverse osmosis membrane;
A first electrolyzer for electrolyzing the concentrated liquid to recover Au;
Furthermore, a route for extracting the semi-concentrated liquid from the membrane separator,
A second electrolysis apparatus for recovering Au by electrolyzing the extracted semi-concentrated liquid;
A path for returning the spent solution after being electrolyzed by the second electrolyzer to the membrane separator;
An apparatus for recovering Au from a cyanate-containing aqueous solution, comprising:   A means for adding an aqueous solution containing hypochlorite ions is attached to the supply means, and the raw material aqueous solution is subjected to a hypochlorous acid treatment between the supply means and the membrane separator. The apparatus of Claim 5 provided with the dehydrochlorous acid apparatus.

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