JP5556701B2 - Method for separating impurity elements from platinum group solution - Google Patents

Description

  The present invention relates to a method for obtaining a platinum group element solution having a low impurity concentration by separating impurity elements, particularly bismuth, tin, and antimony, from a solution containing a platinum group element.

  Platinum group elements such as platinum, palladium, rhodium, and ruthenium are rare in terms of resources, and are rarely produced in natural minerals containing platinum group elements in high quality. Therefore, as a raw material for platinum group elements produced industrially, by-products and spent catalysts from non-ferrous metal smelting such as copper account for the majority.

  When separating and recovering platinum group elements from such platinum group raw materials, for example, anode slime produced in the copper electrolysis process is used as a raw material, which is leached using chlorine gas or chloride, and obtained from the obtained leachate. Separates and collects platinum group elements. In that case, generally, after separating and collecting gold and silver, platinum group elements are separated and collected by a method such as solvent extraction or ion exchange.

  As one method for separating a platinum group element from a platinum group element solution containing impurities such as bismuth, tin, and antimony, there is a method described in Patent Document 1, for example. This method is a method for recovering a platinum group element from an ion exchange resin adsorbed with a platinum group element in a solution by a roasting-acid leaching method, and the ion exchange resin is 500 to 1000 ° C. in an oxidation-reduction atmosphere. Baked at the temperature of, leached the baked product with hydrochloric acid in the presence of an oxidizing agent, and added potassium chloride to the resulting leachate, for example, to separate platinum as a precipitate of potassium hexachloroplatinate (IV) Is the method.

  Precipitation of the platinum group concentrate obtained by the method described in Patent Document 1 described above is performed by adding alkali to change it again to a hydroxide form, adding hydrochloric acid to the hydroxide to dissolve it, and then adding high concentration platinum. A family solution. However, when the obtained platinum group solution contains impurities, especially bismuth, tin, and antimony, it is difficult to completely separate these impurities, and the process is complicated, such as increasing the purification load in the subsequent process. It took a lot of time and effort, and led to an increase in cost. Furthermore, there is a problem that the loss of platinum group elements increases and the actual yield decreases.

  As a method for separating the platinum group element and bismuth relatively efficiently, there is a method described in Patent Document 2, for example. This method includes a first step of leaching a platinum group element-containing material containing an impurity element, a second step of solvent extraction of the impurity element from the obtained leaching product liquid, and a third step of solvent extraction of palladium from the extraction residual liquid. The fourth step of solvent extraction of the cationic impurity element from the extraction residual liquid, the fifth step of hydrolyzing the extraction residual liquid to separate platinum, the sixth step of leaching and separating ruthenium from the precipitate, And a seventh step of solvent extraction of iridium to obtain a back extraction product liquid containing iridium and an extraction residual liquid containing rhodium.

  In the method described in Patent Document 2, bis (2-ethylhexyl) phosphoric acid (D2EHPA) is used as an organic extractant for solvent extraction of a cationic impurity element from the extraction residual liquid obtained in the third step. However, when processing a raw material having a high bismuth concentration, in addition to an increase in the processing period and man-hours, there has been a problem of loss during extraction and separation of platinum group elements.

  Further, as a method for efficiently separating the platinum group element from tin and antimony, for example, there is a method described in Patent Document 3. According to the method of Patent Document 3, (1) a platinum raw material containing tin is oxidized and dissolved, and ammonium chloride is added to the obtained solution to crystallize ammonium hexachloroplatinate (IV) crystals. ) Suspend the crystals in a hydrochloric acid solution having a concentration of 1 to 2 mol / l, cool the suspension and then cool it to dissolve and separate tin to purify the crystals. (3) Purify the purified crystals with alkali It is suspended in an aqueous solution, and a reducing agent is added to obtain platinum powder.

  However, when the method described in Patent Document 3 is applied to, for example, a platinum raw material having a high tin content, the amount of raw material that can be processed per unit time is limited, so that the processing time increases and the number of man-hours increases. There was a problem to do.

JP 2007-302944 A JP 2005-097695 A JP 2008-038159 A

  In view of the above-described conventional problems, the present invention efficiently separates impurity elements such as bismuth, tin, and antimony from a solution containing a platinum group element at a low cost, and has a low impurity element concentration. It aims at providing the method of obtaining the solution of a group element.

In order to achieve the above object, the method for separating an impurity element from a platinum group solution provided by the present invention separates an impurity element from a platinum group solution containing bismuth, tin, and antimony as impurity elements together with the platinum group element. It is a method, Comprising: The following 1st-5th processes are provided, It is characterized by the above-mentioned.
(1) First step (2) of obtaining platinum group potassium salt by adding potassium chloride to the above platinum group solution to precipitate and deposit platinum group element as potassium salt, and solid-liquid separation to obtain platinum group potassium salt 2nd step to obtain potassium salt after washing by adding dilute hydrochloric acid at a concentration of 1 to 3 mol / l to the salt and separating it into solid and liquid (3) Whether sodium hydroxide solution is added to the obtained potassium salt after washing Or after washing, sodium hydroxide is added to a suspension obtained by adding pure water to a potassium salt and suspended to produce a potassium salt-neutralized starch containing a platinum group hydroxide, followed by solid-liquid separation. Third step for obtaining potassium salt neutralized starch (4) Fourth step for adding potassium hydroxide and oxidizing agent to the obtained potassium salt neutralized starch and leaching, followed by solid-liquid separation to recover the leaching residue (5) Hydrochloric acid is added to the recovered leaching residue and dissolved to form a platinum group hydroxide. A fifth step of obtaining a solution mixture

  According to the present invention, an impurity element such as bismuth, tin, and antimony can be efficiently separated from a solution containing a platinum group element to obtain a solution of a platinum group element having a low impurity element concentration. Therefore, the distribution of impurities to the platinum group element purification process can be reduced, the number of processing days and man-hours can be reduced, and the loss of platinum group elements that cannot be recovered can be reduced.

2 is a flow sheet showing each step of the method of the present invention in Example 1. 10 is a flow sheet showing each step in Comparative Example 1.

A method for separating impurity elements such as bismuth, tin, and antimony from the solution containing the platinum group element of the present invention will be described in the order of steps. First, in the first step, each platinum group element in the solution is precipitated and precipitated as a potassium salt by adding potassium chloride to the platinum group solution of the starting material. For example, in the case where the platinum group element is platinum, the precipitation is performed by changing hexachloroplatinum (IV) acid into the form of potassium hexachloroplatinum (IV) (K ₂ PtCl ₆ ). The precipitated platinum group potassium salt is solid-liquid separated and supplied to the next second step.

  The platinum group solution used in the first step is not particularly limited as long as it contains an impurity element such as bismuth, tin, and antimony together with the platinum group element. Examples of typical platinum group solution include a solution obtained by dissolving anode slime produced in a copper electrolysis process with aqua regia, or a leach solution obtained by leaching anode slime using chlorine gas or chloride.

  In the next second step, dilute hydrochloric acid is added to the platinum group potassium salt obtained in the first step and mixed and washed. By this washing with dilute hydrochloric acid, impurity elements such as bismuth, tin and antimony adhering to the platinum group potassium salt are removed without hydrolysis and precipitation, and separated from the platinum group potassium salt into the dilute hydrochloric acid washing solution. The Therefore, by performing solid-liquid separation after washing, the amount of impurity elements in the platinum group potassium salt after washing, particularly the amount of bismuth and antimony, can be greatly reduced.

  It is important that the dilute hydrochloric acid used for washing the platinum group potassium salt in the second step has a concentration in the range of 1 to 3 mol / l. When the concentration of dilute hydrochloric acid is less than 1 mol / l, the separation of bismuth, tin, and antimony becomes insufficient without much difference from washing with water. Moreover, a part of platinum group element melt | dissolves and it is easy to lose. On the other hand, if the concentration of dilute hydrochloric acid exceeds 3 mol / l, not only there is not a great difference in the separation effect of bismuth, tin and antimony, but also the equipment tends to be corroded and the cost is increased.

  At the time of cleaning in the second step, the higher the solution temperature, the higher the solubility of the potassium salt and the higher the cleaning effect. However, if the solution temperature is too high, a fine potassium salt is generated with a decrease in temperature during solid-liquid separation after washing, which may cause clogging of the filter cloth and deteriorate filterability. For this reason, it is preferable to carry out at normal temperature without particularly heating. The cleaning time is preferably as long as possible, but generally a sufficient cleaning effect can be obtained in about 20 to 30 minutes.

  Moreover, in the said 2nd process, it is preferable to adjust the potassium chloride density | concentration in the solution which added the diluted hydrochloric acid which is a washing | cleaning liquid to the range of 120-150 g / l. If the potassium chloride concentration in the solution is less than 120 g / l, even the platinum group element is excessively eluted, which causes a loss of the platinum group element. Further, when the potassium chloride concentration exceeds 150 g / l, the cost increases, and unreacted crystals remain and clog the filter cloth when separating into solid and liquid, or adversely affect the operation. Therefore, it is not preferable.

  As described above, as a method for adjusting the potassium chloride concentration to be high, potassium chloride is added to the solution in which dilute hydrochloric acid is added in the second step, or the platinum group is formed when the potassium salt is formed in the first step. It can be adjusted by controlling the amount of potassium chloride added to the solution.

The washed platinum group potassium salt obtained by solid-liquid separation in the second step is suspended in the next third step by adding a sodium hydroxide solution or adding pure water to the washed potassium salt. The suspension is neutralized by adding sodium hydroxide . By this neutralization reaction, the platinum group element is precipitated as a hydroxide. The obtained potassium salt neutralized starch containing platinum group hydroxide is solid-liquid separated and supplied to the next fourth step.

Neutralization of the platinum group potassium salt uses, for example, a solution having a sodium hydroxide concentration of about 10 to 12%, and this solution is added to the washed platinum group potassium salt so that the pH is in the range of 7 to 8. Adjust as follows. When the pH exceeds 8 , a part of platinum group elements such as ruthenium may be re-dissolved in the solution and lost. On the other hand, if the pH is less than 7 , a part of the platinum group element cannot be recovered and remains in the solution, resulting in loss.

  In the fourth step, the potassium salt neutralized starch obtained in the third step is leached by adding sodium hydroxide and an oxidizing agent, and leaching mainly consisting of hydroxides of platinum group elements by solid-liquid separation. Collect the residue. By this leaching, tin that remains relatively much in the platinum group potassium salt that has been washed in the second step can be efficiently separated into the leaching solution.

  As the sodium hydroxide used for leaching the potassium salt neutralized starch, it is suitable to use a solution having a concentration of about 10 to 12% from the viewpoint that it can be accurately controlled when handled and added. As the oxidizing agent, chlorine gas, ozone, sodium chlorite, or the like can be used, but sodium chlorite is suitable in view of ease of handling and cost. At the time of leaching, the oxidation potential of a slurry obtained by adding sodium hydroxide and an oxidizing agent to potassium salt neutralized starch is measured. Specifically, when a silver-silver chloride electrode is used as a reference electrode, it continues until it reaches 200 mV. By doing so, residual impurities such as tin can be leached and a leaching residue made of a platinum group hydroxide can be obtained. The higher the reaction temperature, the more preferable leaching is promoted. Practically, the reaction temperature is preferably 60 to 80 ° C.

  The leaching residue collected in the fourth step is made into a platinum group hydroxide solution by adding hydrochloric acid and dissolving in the fifth step. In addition, the density | concentration and addition amount of hydrochloric acid used for melt | dissolution of a leaching residue can be adjusted with the conditions used for the process of a platinum hydroxide solution.

  The hydrochloric acid used for dissolving the leaching residue is preferably about 12M, that is, concentrated hydrochloric acid, but may be appropriately adjusted according to the wet state of the leaching residue. The amount of hydrochloric acid added is preferably about 2 liters per 1 kg of the wet leaching residue, and can be dissolved by adding the whole amount at the start and maintaining at room temperature or 60 to 90 ° C. with stirring.

  By the method of the present invention comprising the above first to fifth steps, impurity elements such as bismuth, tin, and antimony are efficiently separated from the platinum group element solution, and the platinum group hydroxide having a low impurity element concentration is dissolved. A liquid can be obtained. In addition, although platinum and ruthenium are partly distributed to the potassium salt neutralized filtrate separated in the third step and the alkaline leachate separated in the fourth step, these are respectively high-grade raw materials for platinum and ruthenium. It can be used effectively by supplying it to the purification process.

[Example 1]
A platinum group raw material containing a large amount of Bi, Sn, and Sb as impurities was prepared, and this platinum group raw material was processed according to each step shown in FIG. That is, the platinum group raw material was dissolved in aqua regia, and the dissolution residue was filtered to obtain a raw material solution. Potassium chloride was added to this raw material solution, and the produced precipitate was subjected to solid-liquid separation to obtain a platinum group potassium salt (first step).

  This platinum group potassium salt was added to 3 mol / l dilute hydrochloric acid so that the slurry concentration became 500 g / l in terms of Wet, and the mixture was stirred and washed for 30 minutes. During this washing, the potassium chloride concentration in the solution was 130 g / l. After washing with dilute hydrochloric acid, the washed potassium salt and dilute hydrochloric acid washing solution were separated into solid and liquid using Nutsche and 5C filter paper (second step).

  Pure water was added to and suspended in the potassium salt crystals after washing. Sodium hydroxide was added to this suspension to adjust the pH to a neutral region of 7 to 8, and the produced potassium salt neutralized starch and potassium salt neutralized filtrate were subjected to solid-liquid separation (No. 3). Process).

  A sodium hydroxide solution was further added to the obtained potassium salt neutralized starch composed of hydroxide to adjust the pH to 11 or more, and a slurry in which the hydroxide was suspended was obtained. After heating this slurry to 60 ° C., a sodium chlorite solution is added as an oxidizing agent, and oxidation is performed until the oxidation-reduction potential (reference electrode: silver chloride electrode) reaches 1000 mV to perform alkali leaching. It was. Thereafter, solid-liquid separation was performed to obtain an alkali leaching solution and an alkali leaching residue (fourth step).

  Next, hydrochloric acid was added to the obtained alkali leaching residue to adjust the pH to be in the range of 1.5 to 2, and the alkali leaching residue was dissolved to obtain a hydroxide solution (fifth step). . In the finally obtained hydroxide solution, 90% or more of impurity elements Bi, Sn, and Sb can be separated, and as a result, a hydroxide solution of a platinum group element having a low impurity quality is obtained. It was.

  In Example 1 above, platinum in each solution of the dilute hydrochloric acid cleaning solution in the second step, the potassium salt neutralized filtrate in the third step, the alkali leaching solution in the fourth step, and the hydroxide solution in the fifth step The concentrations (wt%) of the group elements (Pt, Pd, Rh, Ru) and the impurity elements (Bi, Sn, Sb) are shown in Table 1 below, with the platinum group potassium salt being 100 wt%.

  As can be seen from the results in Table 1 above, the concentrations of Bi, Sn, and Sb in the platinum group hydroxide solution obtained by dissolving the alkaline leaching residue with hydrochloric acid are greatly different from those in the platinum group potassium salt. Reduced to In addition, although the platinum group potassium salt neutralized filtrate in the third step contains a relatively large amount of Pt, it could be used as a high-grade raw material used in the platinum purification step in the subsequent step. Further, Ru and Pt are distributed in the alkaline leachate in the fourth step, but Ru and Pt are further recovered by supplying each of the purification steps.

  According to the present invention, as shown in Table 1, the effect of separating Pd and Rh among the platinum group elements is remarkable. Of the platinum group elements, Pt and Ru are partly distributed to the potassium salt neutralized filtrate and the alkaline leaching solution. As described above, these are effectively supplied as high-grade raw materials to the Pt and Ru purification processes. Can be used.

[Comparative Example 1]
Using the same platinum group raw material as in Example 1, the treatment was performed according to the steps shown in FIG. That is, the platinum group raw material was dissolved in aqua regia, potassium chloride was added to the raw material solution obtained by filtering the dissolution residue, and the resulting precipitate was subjected to solid-liquid separation to obtain a platinum group potassium salt.

  This platinum group potassium salt is neutralized so as to have a pH of 7-8 by adding sodium hydroxide as it is without washing with dilute hydrochloric acid, and the resulting potassium salt neutralized starch is solidified with the potassium salt neutralized filtrate. The liquid was separated. Next, the obtained potassium salt neutralized starch was added and dissolved in hydrochloric acid having a concentration of 6 mol / l so that the slurry concentration would be 100 g / l in terms of Wet, to obtain a hydroxide solution.

  In the comparative example 1, the concentrations (wt%) of platinum group elements (Pt, Pd, Rh, Ru) and impurity elements (Bi, Sn, Sb) in each of the potassium salt neutralized filtrate and the hydroxide solution. Table 2 below shows platinum group potassium salt as 100% by weight.

  As can be seen from the above results, the hydroxide solution finally obtained has a high concentration of Bi, Sn, and Sb, and these impurity elements can be separated from the platinum group elements Bi, Sn, and Sb. could not. Pt in the platinum group potassium salt was also distributed to the potassium salt neutralized filtrate, and this potassium salt neutralized filtrate could be supplied as a raw material to the platinum purification step.

Claims (3)

A method for separating an impurity element from a platinum group solution containing bismuth, tin, and antimony as impurity elements together with a platinum group element, comprising the following first to fifth steps, from the platinum group solution: Separation method of impurity elements.
(1) First step (2) of obtaining platinum group potassium salt by adding potassium chloride to the above platinum group solution to precipitate and deposit platinum group element as potassium salt, and solid-liquid separation to obtain platinum group potassium salt 2nd step to obtain potassium salt after washing by adding dilute hydrochloric acid at a concentration of 1 to 3 mol / l to the salt and separating it into solid and liquid (3) Whether sodium hydroxide solution is added to the obtained potassium salt after washing Or after washing, sodium hydroxide is added to a suspension obtained by adding pure water to a potassium salt and suspended to produce a potassium salt-neutralized starch containing a platinum group hydroxide, followed by solid-liquid separation. Third step for obtaining potassium salt neutralized starch (4) Fourth step for adding potassium hydroxide and oxidizing agent to the obtained potassium salt neutralized starch and leaching, followed by solid-liquid separation to recover the leaching residue (5) Hydrochloric acid is added to the recovered leaching residue and dissolved to form a platinum group hydroxide. A fifth step of obtaining a solution mixture   2. The platinum according to claim 1, wherein in the second step, the concentration of potassium chloride in the solution at the time of mixing and washing by adding dilute hydrochloric acid to a platinum group potassium salt is adjusted to a range of 120 to 150 g / l. Of separating impurity elements from a group solution.   The platinum group solution is a leachate obtained by leaching the anode slime produced in the copper electrolysis process using chlorine gas or chloride, or a solution obtained by dissolving in aqua regia. 3. A method for separating an impurity element from a platinum group solution according to 1 or 2.

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