JP2011122176A - Method for separating palladium from chloride solution containing arsenic - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method in which palladium can selectively be separated from chloride solution containing arsenic and the palladium at a low cost, and even in the case that the arsenic concentration varies, the palladium can stably and efficiently be separated. <P>SOLUTION: After adsorbing the palladium while a primary adsorbent composed of an anion exchange resin having amine or polyamine as a functional group, is brought into contact with the chloride solution containing the palladium and the arsenic, at least one secondary adsorbent selected from an active carbon, quaternary ammonium salt type anion exchange resin, pyridine type anion exchange resin and dithiocarbamic acid-based chelate resin, is brought into contact with liquid after primary adsorption containing the remained palladium which is not adsorbed with the primary adsorbent, to adsorb the palladium in the liquid after the primary adsorption. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention is a method for separating palladium as a noble metal from a chloride solution containing arsenic as an impurity, for example, from a chloride solution containing arsenic and palladium produced in a copper smelting process, and separating palladium with high efficiency by an ion exchange method. Regarding the method.

  Various recycle raw materials such as copper concentrate and waste catalyst which are raw materials for the copper smelting process may contain precious metals such as gold, silver and palladium. In the case of copper concentrate, the precious metals contained in these copper concentrates and recycled raw materials are treated by the copper smelting process and the copper electrolytic refining process. In the case of recycled raw materials, the precious metals are treated by the metal recovery process. It has been separated and recovered, and further refined and recycled as a precious metal smelting process.

  In the precious metal refining step, wet processing is generally used, and various processes for separating and recovering precious metals are known. For example, raw materials such as copper electrolytic slime generated in the copper electrolytic purification process are mixed with an aqueous solution containing chloride ions such as hydrochloric acid, and copper and noble metals are leached into the aqueous chloride solution in the presence of an oxidizing agent such as chlorine gas. After that, a wet process is often used in which the obtained leachate is treated with an ion exchange resin.

  For example, in Patent Document 1, an aqueous solution of chloride containing a platinum group element and an adsorbent composed of a polyamine type ion exchange resin are measured under a condition where the oxidation-reduction potential measured with a silver-silver chloride electrode as a reference electrode is 700 to 1100 mV. The platinum group element is adsorbed on the resin by contacting it, and the adsorbed resin is washed with hydrochloric acid solution or water, and then an aqueous solution containing thiourea at a liquid temperature of 60 to 90 ° C. is brought into contact with the washed resin to form platinum. A method for eluting group elements is described.

  According to the method of Patent Document 1, 99% or more of a platinum group element contained in an aqueous chloride solution, for example, 99% of palladium is adsorbed on the adsorbent, and 99.7% of the adsorbed palladium is adsorbed in the thiourea-containing aqueous solution. It is possible to elute. In addition, since palladium is expensive, for example, it is considered preferable to recover from a contained solution to a low concentration such that it is less than 10 mg / l. For profitability, a recovery rate of at least 95% has been required. .

  However, when the method described in Patent Document 1 is applied to a raw material containing arsenic as an impurity, such as a copper electrolytic slime produced in a copper smelting process, when the concentration of coexisting arsenate ions increases, palladium on an ion exchange resin The adsorption rate of will decrease. For this reason, in industrial operations where the column is packed with ion exchange resin, breakthrough begins early, the frequency of elution from the ion exchange resin increases, and ion exchange resin must be replaced early. There was a problem of being forced.

  Moreover, in recent years, it has become difficult to obtain high-quality ore as a copper smelting raw material, and in particular, the quality of arsenic contained as an impurity has increased. Since it is difficult to effectively separate arsenic even if such ore is selected, the arsenic quality in the copper concentrate is on the rise. In addition, since most of the arsenic contained in the copper concentrate is distributed in the same manner as the noble metal, it is necessary to treat a solution containing arsenic as an impurity together with a noble metal such as palladium in the noble metal purification step. For this reason, in the method of Patent Document 1 described above, a decrease in the adsorption rate of palladium has become an increasingly serious problem.

  As a method for separating and recovering palladium from an aqueous solution containing palladium other than the above, for example, Patent Document 2 discloses hot spring water containing palladium, amidoxime group, phosphate group, amine group, iminodiacetic acid group, phosphoric acid with zirconium. Alternatively, a method of adsorbing palladium by contacting with an adsorbent having a chelate-forming group carrying iron is described. However, since most of the metal ions coexisting in the liquid are adsorbed by this method, arsenic and the like are adsorbed together with palladium, and it is not possible to selectively concentrate and separate only palladium.

  Patent Document 3 discloses that palladium sludge recovered from electroless plating waste solution is dissolved in mineral acid under an oxidized state, and this solution is brought into contact with activated carbon supporting a reducing agent such as a hydroquinone derivative. A method for adsorbing palladium is disclosed. This method is characterized in that palladium can be adsorbed with high efficiency by utilizing the synergistic action of the activated carbon and the reducing agent.

  However, since the binding force between palladium and activated carbon is too strong, it was difficult to efficiently elute palladium adsorbed on the activated carbon. Palladium remaining without being eluted needs to be recovered by decomposing activated carbon by means of roasting or the like, so when processing a solution containing a high concentration and a large amount of palladium, the amount of activated carbon that decomposes also increases. Therefore, there is a disadvantage that it is extremely disadvantageous in terms of cost.

  Furthermore, as described above, it is easily assumed that the concentration of arsenic in the palladium-containing solution to be treated in actual operation varies due to changes in the raw material situation of copper smelting. However, in actual operation of each method described above, it is generally not easy to change the apparatus and operating conditions frequently and flexibly. For this reason, even when the arsenic concentration in the palladium-containing solution to be treated fluctuates, there is an increasing demand for a method that can always obtain a constant adsorption rate stably.

JP 2004-131745 A Japanese Patent Laid-Open No. 2006-026588 JP 2001-303148 A

  In view of the conventional problems described above, the present invention can selectively separate palladium from a chloride solution containing arsenic and palladium at a low cost, and is stable and efficient even when the arsenic concentration fluctuates. An object is to provide a method capable of separating palladium.

In order to achieve the above object, the present inventors examined the form of palladium or arsenic in a chloride solution. First, it is considered that palladium in a chloride solution mainly forms a complex with a chloride ion and exists in the form of a chloro complex represented by, for example, [PdCl ₆ ] ²⁻ . Further, arsenic in the chloride solution is considered to exist mainly as arsenate ions in addition to the form of complex with palladium described later.

On the other hand, when palladium and arsenic acid coexist in a chloride solution, the form of the complex formed by both is not well understood. However, a phosphate ion having a chemical property very similar to that of an arsenate ion is, for example, [Pd ₆ (PO ₄ ) ₅ ] ³⁻ or [Pd ₆ (PO ₄ ) ₄ (HPO ₄ ) as a complex with a palladium ion. It is known to form strong complexes such as ^2- . Therefore, in the case of arsenic acid as well, a strong complex of a form such as [Pd ₆ (AsO ₄ ) ₅ ] ³⁻ or [Pd ₆ (ASO ₄ ) ₄ (HAsO ₄ )] ²⁻ is formed. It is thought that.

  The above-mentioned complex of palladium and arsenic acid is formed in preference to the above-mentioned chloro complex, and as a result, the ratio of palladium existing as a chloro complex in the chloride solution is considered to decrease. In addition, the complex of palladium and arsenic acid differs from the chloro complex in the same manner as the phosphate ion and arsenic complex described above in terms of chemical properties such as complexing ability, and can easily be used as a weakly basic ion exchange resin such as a polyamine type. Since it is not adsorbed, it was considered difficult to apply a method of separating and recovering with a polyamine type ion exchange resin alone as in Patent Document 1.

  Therefore, as a result of repeated experiments and examinations, the present inventors first adsorbed palladium existing in the form of a chloro complex that is easily adsorbed using an adsorbent that has a relatively weak adsorption force but is easy to elute. Then, arsenic is contained by using a two-stage adsorption method that forms a strong complex with arsenic acid and recovers palladium remaining in the solution using an adsorbent that has a strong adsorption force but is difficult to elute. It has been found that palladium in chloride solution can be separated economically and efficiently.

  That is, in the method for separating palladium from a chloride solution containing palladium and arsenic provided by the present invention, a primary adsorbent comprising an anion exchange resin having amine or polyamine as a functional group is contacted with the chloride solution. Then, after adsorbing palladium on the primary adsorbent, activated carbon, quaternary ammonium salt type anion exchange resin, pyridine type are added to the post-primary adsorbed solution containing palladium remaining without being adsorbed on the primary adsorbent. It is characterized in that at least one secondary adsorbent selected from an anion exchange resin and a dithiocarbamic acid chelate resin is brought into contact to adsorb palladium in the liquid after the primary adsorption to the secondary adsorbent.

  According to the present invention, palladium can be selectively separated from a chloride solution containing arsenic, and the separation can be continued stably and highly efficiently even when the arsenic concentration varies. In addition, the ion exchange resin of the primary adsorbent can be reused, and the secondary adsorbent is difficult to elute, so even when it is finally decomposed, the amount used can be reduced, and the operation can be performed with reduced costs as a whole. It is. In addition, since it is not necessary to use a special reagent or a special adsorbent, it is possible to minimize the environmental load such as waste water treatment.

  The method for separating palladium according to the present invention is a primary adsorbent comprising an anion exchange resin having an amine or polyamine as a functional group when adsorbing and separating palladium from a chloride solution containing palladium and arsenic with an adsorbent. And a secondary adsorption process using at least one secondary adsorbent selected from activated carbon, a quaternary ammonium salt type anion exchange resin, a pyridine type anion exchange resin, and a dithiocarbamic acid chelate resin. And.

  In the primary adsorption step, palladium present as a chloro complex, which is the majority of palladium present in a plurality of forms described above in the chloride solution, is adsorbed by the primary adsorbent. The primary adsorbent used in the primary adsorption step may be any adsorbent that has a relatively weak adsorptive power and is easy to elute and has a weak chelate binding force with palladium. An anion exchange resin having a polyamine is preferred.

  As the anion exchange resin as the primary adsorbent, for example, an amine type having a primary, secondary, or tertiary amine as a functional group, or a polyamine type anion exchange resin having a polyamine is suitable. In particular, polyamine type anion exchange resins which are easily available industrially are most suitable. Palladium adsorbed on the anion exchange resin as the primary adsorbent can be easily eluted and recovered by contacting with an eluent such as an aqueous solution of thiourea or hydrochloric acid.

  The liquid passing conditions in the primary adsorption step vary depending on the concentration and composition of the chloride solution, but in the case of an operation in which a general anion exchange resin is packed in a column and continuously passed, for example, in one hour. When passing at a flow rate (SV2.5) that is 2.5 times the volume of the resin, a volume (BV15) that is about 15 times the amount of the resin can be passed. The temperature of the chloride solution to be passed is preferably about 40 ° C. In addition, as a guideline for resin exchange, it may be a time when an adsorption rate of 90% or more is obtained, specifically, a time when the palladium concentration in the liquid after the primary adsorption is increased to about 0.02 g / l or more. .

In the primary adsorption step using the above-described anion exchange resin, it is not possible to adsorb and separate all palladium in a chloride solution containing arsenic. That is, for example, palladium that forms a complex with arsenic in a form such as [Pd ₆ (AsO ₄ ) ₅ ] ³⁻ or [Pd ₆ (ASO ₄ ) ₄ (HAsO ₄ )] ²⁻ is a primary adsorbent. The anion exchange resin is not adsorbed and remains in the liquid after the primary adsorption.

  Therefore, in the present invention, in the next secondary adsorption step, palladium remaining in the post-primary adsorption solution obtained in the primary adsorption step as a complex with arsenic having the above form is used using the secondary adsorbent. Separation by adsorption.

  As the secondary adsorbent, an adsorbent that has a strong adsorbing power and is difficult to elute is required, and is selected from activated carbon, quaternary ammonium salt type anion exchange resin, pyridine type anion exchange resin, and dithiocarbamic acid chelate resin. At least one of these can be used preferably. In addition, the said activated carbon does not need to use the activated carbon containing organic chelate formation agents, such as the hydroquinone derivative of the said patent document 3, and means general activated carbon.

  In the secondary adsorption process, a secondary adsorbent with strong adsorptive power is used to adsorb the complex of arsenic and palladium that is difficult to be adsorbed on the amine-type or polyamine-type anion exchange resin used as the primary adsorbent. is doing. Therefore, the palladium adsorbed on the secondary adsorbent is strongly adsorbed, and it is difficult to elute palladium in a form that can reuse the secondary adsorbent. Therefore, finally, it is necessary to decompose the secondary adsorbent by means such as roasting and recover palladium.

  However, in the present invention, since most of the palladium in the chloride solution has already been separated in the primary adsorption step, the amount of secondary adsorbent used is the same as that in the chloride solution using the same adsorbent. The amount of palladium is much less than when separated in a single adsorption step. In addition, since the secondary adsorbent has a simpler structure and is cheaper than the primary adsorbent, it is possible to minimize the increase in cost even if it is decomposed by roasting or the like. Is possible.

[Example 1]
After copper concentrate was smelted in a copper smelting process and electrolytic copper was separated by electrolytic purification, copper electrolytic slime precipitated at the bottom of the electrolytic cell was recovered. This copper electrolytic slime was washed with water and dehydrated, then mixed in a hydrochloric acid solution having a concentration of 1 mol / l to form a slurry, and leached using chlorine gas. Copper was separated from the obtained leachate, and the hydrochloric acid concentration was adjusted to obtain a chloride solution having a composition of palladium concentration of 0.14 g / l, arsenic concentration of 6.6 g / l, and free hydrochloric acid concentration of 1 mol / l. .

The above chloride solution was used as a stock solution, and 100 ml of a polyamine type anion exchange resin (trade name: Purolite A-830) manufactured by Sumitomo Chemical Co., Ltd. was added as a primary adsorbent to 1000 ml of this stock solution and maintained at 25 ° C. Then, while adding a 25% aqueous solution of NaClO _2, silver - maintaining the redox potential to a silver chloride electrode reference electrode (ORP) in the range of 900～1100MV. After potential adjustment, the mixture was stirred and mixed with a stirrer for 30 minutes (primary adsorption step).

  After the stirring, the mixture was filtered using a filter paper, Nutsche and a filter bottle to separate into solid and liquid. As a result of analyzing the filtrate (liquid after primary adsorption) by ICP, the palladium concentration was 0.010 g / l, the arsenic concentration was 6.0 g / l, and 93% of the palladium contained in the stock solution and 9% of the arsenic were It was found that it was adsorbed on the ion exchange resin. However, it is difficult to say that the palladium has been sufficiently recovered in view of the palladium concentration in the post-primary adsorption solution.

  Therefore, 100 ml each of the post-primary adsorption solution obtained in the primary adsorption step was taken, and 1.0 g of the following secondary adsorbent was mixed with each, and stirred with a stirrer at 25 ° C. for 30 minutes (secondary Adsorption process). Thereafter, filtration and solid-liquid separation were performed in the same manner as described above, and the obtained filtrate (secondary adsorbed solution) was analyzed by ICP to measure the concentrations of palladium and arsenic.

  As for the secondary adsorbent used in the secondary adsorption step, sample 1 is coconut shell activated carbon (trade name: Kuraray Coal GW) manufactured by Kuraray Co., Ltd., and sample 2 is a pyridine-based anion exchange manufactured by Sumitomo Chemical Co., Ltd. Resin (trade name: Sumichel CR-2), sample 3 is a dithiocarbamic acid chelate resin (trade name: Sumichelate Q-10) manufactured by Sumitomo Chemical Co., Ltd., and sample 4 is quaternary ammonium I manufactured by Sumitomo Chemical Co., Ltd. It is a type anion exchange resin (trade name: Duolite A-113).

  Table 1 below shows the types of secondary adsorbents, the concentrations of palladium and arsenic in the secondary adsorbed solution, and the adsorption rates of palladium and arsenic from the stock solution. As a comparative example, the concentration of palladium and arsenic in the post-primary adsorption solution obtained only by the primary adsorption step without performing the secondary adsorption step, and the adsorption rate of palladium and arsenic from the stock solution are as follows. The results are also shown in Table 1.

  Only in the primary adsorption process using the polyamine type anion exchange resin as a comparative example, 93% of palladium in the stock solution was separated. On the other hand, in the Example of the present invention in which the same primary adsorption process is combined with the secondary adsorption process, 96% of sample 1 using activated carbon as the secondary adsorbent, sample 2 using pyridine anion exchange resin, and dithiocarbamine The adsorption rate was 99% in sample 3 using an acid-based chelate resin and 98% in sample 4 using a quaternary ammonium type I anion exchange resin. That is, palladium contained in 0.14 g / l in the stock solution could be separated until it became 5 mg / l or less.

[Example 2]
100 ml of the primary post-adsorption liquid obtained by the primary adsorption step using a polyamine type anion exchange resin (trade name: Purolite A-830) in Example 1 was collected. This post-primary adsorption solution was passed through a column (activated carbon 5 ml, inner diameter 12 mm × height 45 mm) filled with Kuraray Co., Ltd. coconut shell activated carbon (trade name: Kuraray Coal GW).

  At that time, the liquid flow rate was a flow rate (SV2) that is twice the ion exchange resin capacity per hour. When the amount of the effluent (BV) from the column discharge part becomes 4 to 150 times the volume of the ion exchange resin, the liquid discharged first after the previous collection is collected, and the ICP is used to collect palladium and The concentration of arsenic was analyzed. The obtained results are shown in Table 2 below for each sampling range of the effluent volume (BV) together with the concentration of the stock solution.

  As can be seen from this result, the adsorption rate of palladium was 99% or more, which was further improved as compared with Example 1, by passing the liquid through a column. On the other hand, it was confirmed that the adsorption rate of arsenic gradually decreased with the passage of liquid and the selectivity was further improved.

Claims (1)

  In the method for separating palladium from a chloride solution containing palladium and arsenic, the primary adsorbent composed of an anion exchange resin having an amine or polyamine as a functional group is brought into contact with the chloride solution to obtain primary palladium. After adsorbing to the adsorbent, activated carbon, a quaternary ammonium salt type anion exchange resin, a pyridine type anion exchange resin, dithiocarbamic acid is added to the post-primary adsorption solution containing palladium remaining without being adsorbed by the primary adsorbent. A method for separating palladium, comprising bringing a secondary adsorbent to adsorb palladium in a solution after primary adsorption by contacting at least one secondary adsorbent selected from a system chelate resin.