JP2005144374A - Method for removing chlorine ion in nonferrous metal sulfate solution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple and inexpensive method capable of separating and removing chlorine ions contained in a solution of a nonferrous metal sulfate such as nickel sulfate or the like to reduce the same to an extremely minute amount level desired in a use of an electronic material, a catalyst material or the like. <P>SOLUTION: In this method, at least one of metal silver, silver oxide or silver sulfate or carbonate is added to a chlorine-containing sulfate solution to sediment and remove chlorine ions in the solution as silver chloride. The excessive silver ions remaining in the solution can be removed by a cementation method. Further, this sedimented and removed silver chloride is reacted with an alkali solution to regenerate silver oxide and this silver oxide is returned to a chlorine ion removing process. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for separating and removing chlorine ions contained in a solution from a sulfate solution of a non-ferrous metal such as nickel sulfate, copper sulfate, and cobalt sulfate.

  Sulfates such as nickel sulfate, copper sulfate, and cobalt sulfate are widely used as various industrial raw materials for plating, pigments, etc. Recently, high purity materials are required for electronic materials and catalytic materials. Yes.

  Non-ferrous metal sulfate solutions as described above often contain chlorine as one of the impurities. Chlorine as an impurity is attributed to the fact that hydrochloric acid and chlorine used in the process of producing sulfate from ore remain or are mixed in various raw materials such as scrap and plating sludge. ing.

  These chloride ions not only adversely affect the progress of corrosion of reaction vessels and piping during the process of purifying nonferrous metal sulfate from solution, but also remain in nonferrous metal sulfate products. In particular, in the case of products used for applications such as electronic materials and catalyst materials, the performance of electronic components and catalysts deteriorates due to the chemical reaction of chlorine ions. The complete removal of ions is desired.

  Although it is difficult to remove chloride ions contained in sulfate solution, as a complete removal method, once extract metal ions in solution using acidic extraction solvent, back extraction with sulfuric acid to obtain sulfate solution There is a method (Japanese Patent Laid-Open No. 10-310436). Since the acidic extractant extracts only metal cations and does not extract chloride ions, a sulfate solution containing no chloride ions can be obtained. However, this method requires an alkali or acid for pH adjustment in the extraction and back extraction, and thus increases the cost. Therefore, it has been difficult to apply this method for other purposes.

  Further, chlorine ions in the solution can be removed by selective adsorption to an ion exchange resin. However, in the sulfate solution, since the concentration of sulfate ions serving as a matrix is significantly higher than the concentration of chloride ions to be removed, competition of adsorption sites of the ion exchange resin occurs, and sulfate ions are also adsorbed. Therefore, selective adsorption of chloride ions is very difficult, and the removal thereof is not sufficient.

  Furthermore, a separation method using a difference in crystallization efficiency such as crystallization of metal salt is also conceivable. For example, sulfate is less soluble than chloride, and sulfate concentrates preferentially when a sulfate solution containing chlorine ions is concentrated by heating. However, a method for adjusting the crystallization degree so that chlorine ions are not mixed and separating and recovering only desired metal sulfate crystals is industrially expensive.

  As another method, a method of precipitating chlorine ions as silver chloride by adding silver nitrate is also known (Japanese Patent Laid-Open No. 10-216741). However, in this method, it is difficult to determine the optimum amount of silver nitrate to be added to chlorine ions, so an excess amount of Ag ions remains in the solution and nitrate radicals remain in the system, thus removing anions. It cannot be adapted to the process. In addition, the silver chloride precipitated and separated by this method was redissolved using a complex formation reaction, recovered as a metal by electrolysis, and repeated as a process again as silver nitrate. There was a problem.

JP-A-10-310436 Japanese Patent Laid-Open No. 10-216741

  In view of the above-described conventional circumstances, the present invention separates and removes chlorine ions contained in a sulfate solution of a non-ferrous metal such as nickel sulfate, so that a trace amount level desired for applications such as electronic materials and catalyst materials is obtained. It is an object of the present invention to provide a simple and inexpensive method capable of reducing chlorine ions to a minimum.

  In order to achieve the above object, the present invention provides a method for removing chlorine ions in a non-ferrous metal sulfate solution by adding metal silver, silver oxide, silver sulfate or carbonate to a non-ferrous metal sulfate solution containing chlorine. It is characterized in that at least one salt is added and chlorine ions in the solution are precipitated and removed as silver chloride.

  In the method for removing chlorine ions in the non-ferrous metal sulfate solution of the present invention, it is preferable to manage the progress and end point of the chlorine ion removal reaction by the measured value of the chlorine ion concentration using an ion meter.

  In the method for removing chlorine ions in the non-ferrous metal sulfate solution of the present invention, excessive silver ions remaining in the solution can be removed by a cementation method after the silver chloride is precipitated and removed.

  Furthermore, in the method for removing chlorine ions in the non-ferrous metal sulfate solution of the present invention, the silver chloride that has been removed by precipitation is reacted with an alkali to form silver oxide, and the obtained silver oxide is repeatedly subjected to the chlorine ion removing step to produce sulfuric acid. Can be added to the salt solution.

  According to the present invention, by simply adding silver metal, silver oxide, silver sulfate or carbonate to a sulfate solution, chlorine ions contained in the solution can be separated and removed as silver chloride easily and inexpensively. In particular, it is possible to reduce chlorine ions to a very small level desired in applications such as electronic materials and catalyst materials. Further, the separated and recovered silver chloride can be regenerated with an alkali at a low cost and repeatedly used in the chlorine ion removing step.

In the chlorine ion removal method of the present invention, chlorine ions contained in a sulfate solution such as nickel sulfate are reacted with silver ions to form hardly soluble silver chloride (AgCl), which is precipitated and separated from the solution. The silver ion source added to the sulfate solution is at least metal silver (silver metal), silver oxide (Ag ₂ O), silver sulfate (Ag ₂ SO ₄ ), or silver carbonate (Ag ₂ CO ₃ ). Any one of them.

As a main reaction in the chlorine ion removing step, the case of using silver metal is shown in the following reaction formula 1.
[Reaction Formula 1]
2Ag + H ₂ O ₂ + 2HCl = 2AgCl + 2H ₂ O

  When silver metal is added in a sulfate solution, it elutes into the solution as silver ions under acidic and oxidizing conditions, and reacts with chlorine ions in the solution to form poorly soluble silver chloride (AgCl). Precipitate. As conditions for the silver metal to dissolve, it is desirable that the pH is 1-2 and the redox potential ORP is about 600 mV (vs. Ag / AgCl). In the ORP of 600 mV or less, the dissolution of silver metal does not proceed, chlorination occurs only on the silver surface, and the fixation of chloride ions does not proceed.

Moreover, as a main reaction in the said chlorine ion removal process, the case where silver oxide is used is shown in the following Reaction Formula 2, and the case where silver sulfate or carbonate is used is shown in the following Reaction Formula 3, respectively.
[Reaction Formula 2]
Ag ₂ O + NiCl ₂ + H ₂ SO ₄ = 2AgCl + NiSO ₄ + H ₂ O
[Reaction Formula 3]
Ag ⁺ + Cl ⁻ = AgCl

  Since silver oxide and silver carbonate are dissolved in an acidic sulfate solution, and silver sulfate is dissolved in water, silver ions and chloride ions generated by dissolution react to form hardly soluble silver chloride and precipitate. These reactions proceed at pH 7 or lower. Silver nitrate also dissolves in the solution in the same way as silver sulfate and reacts with chlorine ions to form silver chloride. In this case, nitrate ions are mixed in the solution, so that anions such as this step are separated. It is unsuitable for cases.

  The amount of silver to be added is desirably about 1 equivalent in terms of silver ions with respect to chlorine ions. Although the reaction between chloride ion and silver ion occurs quantitatively, it is generally difficult to analyze the chloride ion concentration in a sulfate solution quickly or continuously, and therefore it is difficult to determine the amount of silver ion added. . Therefore, silver or a silver salt added in an equivalent amount or more tends to remain in the solution in the form of silver ions. Therefore, it is preferable to control and control the progress and end point determination of the reaction based on the measured value of the chlorine ion concentration using an ion meter.

  Moreover, after silver chloride is precipitated and removed, excess silver ions remaining in the solution can be recovered by metal cementation. For example, nickel, zinc, copper, or the like can be used as the metal to be added. However, since it is necessary to dissolve an amount of metal necessary for the cementation reaction, it is necessary to perform the reaction while maintaining the pH at about 1. From this cementation, the silver ions remaining in the solution can be almost completely removed.

  Conventionally, the silver chloride separated and removed from the sulfate solution by various methods is dissolved as a complex salt in aqueous ammonia, concentrated hydrochloric acid, etc., and after obtaining metallic silver by electrolysis, the silver is dissolved in nitric acid as necessary. Thus, the process has been repeated in the chlorine ion removal step (see JP-A-10-216741). However, this method is expensive in terms of cost because it requires different steps of dissolution by complex formation and electrolysis.

In the method of the present invention, in order to reduce this cost, the separated and recovered silver chloride is brought into contact with ants such as caustic soda and reacted according to the following reaction formula 4 to regenerate as silver oxide. The obtained silver oxide can be added to the sulfate solution by repeating the chlorine ion removing step.
[Reaction Formula 4]
_{2AgCl + 2NaOH = 2NaCl + Ag 2} O + H 2 O

Since the above reaction involves dehydration, it is desirable to use an alkali solution having a concentration as high as possible. In addition, since the reaction does not proceed as the chlorine ion concentration increases, it is effective to add 5 to 15 times the alkali with respect to the equivalent, and to use a high concentration alkaline solution of about 8N. In the above reaction, if the alkali solution such as caustic soda include carbon dioxide absorbed from the atmosphere, although there may be a Ag ₂ CO ₃ generated with Ag 2 _O, chloride ions removed in the present invention In this case, there is no problem because silver carbonate can be used.

Also, to prevent re-reaction with chlorine ions, the mixture was filtered, then washed, is contacted with further fresh alkali solution, thereby improving the regeneration efficiency of the Ag 2 _O. By repeating this series of regeneration steps (reaction, filtration, washing) several times, it is possible to obtain silver oxide having a lower silver chloride quality. Further, the alkali added excessively contains silver oxide corresponding to the solubility, but this can be recovered by adding chlorine ions.

[Example 1]
Place 100 ml of synthetic nickel sulfate solution containing chlorine ions in a 200 ml beaker, add 0.9 to 1.5 equivalents of silver sulfate or silver oxide to chlorine ions in the solution, and at room temperature (25 ° C.). The mixture was stirred and mixed with a stirrer for 1 hour. The composition of the synthetic nickel sulfate solution was Ni: 102 g / l, Cl: 1.0 g / l, and SO ₄ : 165 g / l.

  The solution after the reaction was filtered, and the analysis result of the obtained filtrate was shown in Table 1 below together with the added equivalent of silver sulfate or silver oxide added, the pH of the solution, and the ORP of the solution. As can be seen from the results, both silver sulfate and silver oxide have an effect of removing chlorine ions, the reactivity is very good, and the chlorine ions can be reduced to 1 mg / l or less.

[Example 2]
100 ml of a synthetic nickel sulfate solution having the same composition as in Example 1 above was placed in a 200 ml beaker, 1.0 equivalent of silver metal powder was added to the chlorine ions in the solution, and the mixture was stirred at 80 ° C. for 1 hour. Stir and mix. Since silver powder is difficult to dissolve, the reaction was carried out by adjusting the pH to 1 with sulfuric acid and raising the ORP to 600 mV (vs. Ag / AgCl) with hydrogen peroxide.

  The solution after the reaction was filtered, and the analysis result of the obtained filtrate was shown in Table 2 below together with the addition equivalent of the added silver powder, the pH of the solution, and the ORP of the solution. As can be seen from this result, the silver powder also has an effect of removing chlorine ions, the reactivity is very good, and the chlorine ions can be reduced to 1 mg / l or less.

[Example 3]
50 ml of two kinds of synthetic nickel sulfate solutions containing chlorine ions are put in a 100 ml beaker, and silver oxide is added little by little while confirming the chlorine ion concentration in the solution with an ion meter equipped with a chlorine ion electrode. The mixture was stirred and mixed with a stirrer at 25 ° C for 1 hour. The synthetic nickel sulfate solution has an initial Ni ion concentration of 100 g / l, and an initial Cl ion concentration of 0.53 g / l and 0.19 g / l, respectively.

  The added silver oxide reacts almost instantaneously at the beginning of the reaction, but the reaction gradually slows from the point where the chloride ion concentration falls below 100 mg / l. Therefore, when the chlorine ion concentration falls below 100 mg / l, silver oxide is added in finer portions while measuring the chlorine ion concentration with an ion meter, and finally the reaction is performed for 1 hour, and then held for 30 minutes. Finished.

  Regarding the final solution after completion of the reaction, the ion meter value and chemical analysis value of the chlorine ion concentration and the analysis result of the silver ion amount are shown in Table 3 below together with the addition equivalent of the added silver oxide. As can be seen from this result, when the chlorine ion concentration in the final liquid is 10 mg / l, the silver in the final liquid is extremely small, less than 0.001 g / l, but the chlorine ion concentration in the final liquid is 0.001. When the concentration was reduced to about 1 mg / l, 0.016 g / l of silver ions was detected in the final solution.

  According to Example 3 above, it was confirmed that the reaction could be controlled while predicting the chemical analysis value of chlorine ions in the solution with a chlorine ion meter, and the end point could be determined reliably. In addition, by controlling the amount of silver added with an ion meter, it was possible to hardly leave silver ions in the nickel sulfate solution after chlorine ion removal.

[Example 4]
50 ml of a synthetic nickel sulfate solution having a silver ion concentration of 0.16 g / l was placed in a 100 ml beaker, and excess nickel metal or nickel sulfide was added to try to fix silver ions by cementation. The reaction temperature was 80 ° C. and the pH was adjusted to 1 with sulfuric acid. As the silver ion, silver sulfate, which is a dissolved form in a sulfuric acid bath, was used.

  The silver ion concentration in the final solution after completion of cementation was measured, and the results are shown in Table 4 below together with the addition equivalents of nickel metal and nickel sulfide to silver. As can be seen from this result, silver ions excessively eluted in the solution can be fixed by cementation of nickel metal or nickel sulfide.

[Example 5]
From silver chloride, put 5 g of silver chloride in a 100 ml beaker, add 1-15 times caustic soda solution of 8N (25%) and react for 2 hours at normal temperature or 60 ° C. A regeneration test to silver oxide (Ag ₂ O) was performed. However, only for sample 7, the test was conducted by contacting 3 times the equivalent of 8N caustic soda for 5 cycles.

The slurry after the reaction is filtered, washed with water, dried, analyzed by X-ray diffraction, the composition ratio of Ag ₂ O is obtained from the peak intensity, and the result is shown in Table 5 as Ag ₂ O quality. Indicated. Although NaCl was simultaneously generated by the reaction shown in the above reaction formula 4, it was removed by washing with water and was hardly detected.

  As can be seen from this result, to increase the regeneration rate from silver chloride to silver oxide, it is effective to add 5 to 15 times caustic soda with respect to the equivalent, and the higher the temperature, the more effective. Furthermore, as in sample 7, regeneration by repeated contact that can suppress the influence of chlorine ions was most effective, and regeneration was possible up to about 90% in silver oxide quality.

[Example 6]
Using regenerated silver oxide (silver quality: 86.2 to 90.4% by weight) and reagent silver oxide (silver quality: 93.1% by weight) obtained in the same manner as in Example 5 above, each of chloride ions A removal test was performed. That is, the above silver oxides were added to a nickel sulfate solution having a composition of Ni: 105 g / l and Cl: 1.10 g / l and reacted at room temperature (25 ° C.) for 1 hour. The reaction end point was determined using an ion meter.

  The final solution after the reaction was analyzed for chlorine ion concentration and silver ion concentration. The results are shown in Table 6 below together with the silver quality and added equivalent of added silver oxide and the chlorine ion concentration measured by an ion meter in the final solution. As can be seen from this result, silver oxide regenerated from silver chloride also has an effect of removing chlorine ions, and the chlorine ions could be reduced to 1 mg / l or less.

Claims (4)

It is characterized by adding at least one of metallic silver, silver oxide, or silver sulfate or carbonate to a nonferrous metal sulfate solution containing chlorine, and precipitating and removing chlorine ions in the solution as silver chloride. A method for removing chloride ions in a non-ferrous metal sulfate solution. The method for removing chlorine ions in a non-ferrous metal sulfate solution according to claim 1, wherein the progress and end point of the chlorine ion removal reaction are managed by the measured value of the chlorine ion concentration using an ion meter. 3. The removal of chlorine ions in a non-ferrous metal sulfate solution according to claim 1, wherein excess silver ions remaining in the solution are removed by a cementation method after the silver chloride is precipitated and removed. Method. The precipitated silver chloride is reacted with an alkali to form silver oxide, and the obtained silver oxide is added to the sulfate solution by repeating the chlorine ion removing step. A method for removing chloride ions in a nonferrous metal sulfate solution as described.