A method for treating nickel precipitation re-dissolution in ammonium sulfate solution

Abstract

The invention discloses a method for treating nickel precipitates in ammonium sulfate solution and belongs to the field of metallurgy and chemical engineering. The method combines free nickel ions into a stable organic nickel complex precipitate by sequentially adopting a combination of pretreatment, ammonium sulfide nickel precipitation, oxidation and complex breaking, and fenammonium nickel solidification, and finally removes the nickel precipitate by simple filtration. The method can effectively prevent the nickel precipitate from dissolving, solves the problem of excessive heavy metal content caused by the dissolution of heavy metal nickel precipitates in ammonium sulfate solution, and makes the salt product of the purified ammonium sulfate solution reach the GB535-1995 superior product quality standard through evaporation and crystallization, thereby improving economic benefits and avoiding environmental pollution, and having high application value.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgy and chemical engineering, and in particular to a method for treating the re-dissolution of nickel precipitates in an ammonium sulfate solution. Background Art

[0002] The production process of many major products in the metallurgical and chemical industries produces a large amount of ammonium sulfate-containing salt solution. This salt solution contains a certain amount of heavy metal nickel ions. These nickel ions can enter the ammonium sulfate product during the subsequent evaporation and crystallization process, causing the ammonium sulfate product to exceed the heavy metal content standard. Currently, commonly used methods for removing nickel from ammonium sulfate salt solutions include resin adsorption and chemical precipitation. The resin adsorption method suffers from the following problems: during the sulfuric acid elution process after resin adsorption, a large amount of nickel sulfate solution is produced, which requires further processing, resulting in a complex process flow and high processing costs. Chemical precipitation often uses sulfide to precipitate nickel, which is simple and easy to operate. However, during this process, nickel forms an insoluble nickel sulfide precipitate. Simultaneously, due to the hydrolysis of the sulfide, some nickel hydroxide precipitates. Subsequently, the nickel hydroxide forms complex ions with ammonium ions and enters the solution, causing the nickel precipitate to dissolve again. This results in excessive nickel content in the post-precipitation solution, significantly affecting the quality of the ammonium sulfate product.

[0003] Therefore, in view of the problems of incomplete nickel removal, complicated process flow and high treatment cost in the metallurgical and chemical industry, as well as the phenomenon of nickel precipitation and re-dissolution in ammonium sulfate solution, it is very necessary to develop a treatment method that can effectively prevent the occurrence of nickel precipitation and re-dissolution in ammonium sulfate solution, so that the quality of ammonium sulfate products can reach industrial-grade product standards. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a method for treating nickel precipitates and dissolving in ammonium sulfate salt solution. The treatment method solves the problems of incomplete nickel removal, complex process flow, relatively high operating requirements, high treatment cost, low stability, difficulty in promotion and difficulty in meeting industrial-grade product standards of salt products in the existing methods by adopting a combined process of pretreatment, ammonium sulfide nickel precipitation, oxidation and chelation breaking, and thiram ammonium nickel fixation.

[0005] In order to solve the above problems, the technical solutions adopted by the present invention are as follows:

[0006] A method for treating nickel precipitate re-dissolution in ammonium sulfate solution, comprising the following steps:

[0007] S1. Pretreatment: adjusting the pH of the nickel-containing ammonium sulfate solution to 4-6;

[0008] S2, nickel precipitation: adding ammonium sulfide solution to the ammonium sulfate solution prepared in step S1, adjusting the pH to 7-9, stirring, without solid-liquid separation, to obtain a nickel precipitation solution;

[0009] S3, oxidative decomposition of nickel: ozone is introduced into the nickel precipitation solution of step S2, and thiamin solution is added at the same time. After stirring, the nickel precipitate is filtered to separate the ammonium sulfate solution to obtain an ammonium sulfate solution with extremely low nickel content.

[0010] As a preferred embodiment of the present invention, the ammonium sulfate concentration of the nickel-containing ammonium sulfate salt solution in step S1 is 20-200 g / L; the nickel ion concentration is 0.001-1.0 g / L.

[0011] As a preferred embodiment of the present invention, the acid used for adjusting the pH in steps S1 and S2 is 4N sulfuric acid, and the base is industrial ammonia water with a mass fraction of 25%.

[0012] As a preferred embodiment of the present invention, the mass fraction of the ammonium sulfide solution in step S2 is 5-20%; the volume ratio of the ammonium sulfide solution to the ammonium sulfate salt solution is 1:500-2000.

[0013] As a preferred embodiment of the present invention, the stirring time in step S2 is 2 to 4 hours, preferably 3 to 4 hours; and the stirring speed is 100 to 300 r / min.

[0014] As a preferred embodiment of the present invention, the amount of ozone introduced in step S3 is 1-20 mg / L, preferably 4-6 mg / L. Ozone is continuously introduced during the reaction, with a gas volume ratio of 1-1.5.

[0015] As a preferred embodiment of the present invention, the mass fraction of the fenamide solution in step S3 is 1 to 30%.

[0016] As a preferred embodiment of the present invention, the volume ratio of the fenamide solution to the ammonium sulfate solution in step S3 is 0.002-0.010:1.

[0017] As a preferred embodiment of the present invention, the stirring time in step S3 is 2 to 6 hours.

[0018] As a preferred embodiment of the present invention, the ozone in step S3 is introduced into the nickel-precipitated liquid by a gas pressure pump.

[0019] As a preferred embodiment of the present invention, the pore size of the filter element used for the filtration in step S3 is 0.2 to 0.5 μm.

[0020] As a preferred embodiment of the present invention, a pH meter is used to monitor the pH value in steps S1 to S3.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The method for treating the re-dissolution of nickel precipitate in ammonium sulfate solution of the present invention solves the problem of excessive heavy metals caused by the re-dissolution of heavy metal nickel precipitate in ammonium sulfate solution by sequentially adopting the combined steps of pretreatment, ammonium sulfide nickel precipitation, oxidation complex breaking, and furamide nickel solidification. The pretreatment is carried out by adjusting the pH value of the ammonium sulfate solution, and then ammonium sulfide is added to the solution to sulfide the nickel ions to generate metal sulfide precipitates. The oxidation complex breaking is carried out by adding ozone, a strong oxidizing complex breaking agent, at the same time as the precipitation reaction is completed, which can effectively destroy the stable complex state between ammonia and the re-dissolved nickel ions, so that the nickel-ammonia complex ions are dissociated into Ni 2+ , then add fenamide to combine it with free nickel ions to form a stable organic nickel complex precipitate, and finally remove the nickel precipitate by simple filtration. The treatment method of the present invention can not only effectively prevent the nickel precipitate from re-dissolving, solve the problem of excessive heavy metal content caused by the re-dissolution of the nickel precipitate, but also completely remove the impurity heavy metal Ni, so that the salt product of the purified ammonium sulfate salt solution after evaporation and crystallization meets the GB535-1995 superior product quality standard. The process is simple, the operation is stable, the operation requirements are relatively low, the processing cost is low, the economic benefits are improved, and the environmental pollution is avoided, and the application value is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention provides a process flow chart of the method for treating nickel precipitate re-dissolution in ammonium sulfate solution. DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] like Figure 1 As shown, the method for treating nickel precipitation and re-dissolution in ammonium sulfate solution provided by the present invention comprises three steps in sequence: pretreatment, ammonium sulfide nickel precipitation, and oxidation to break the complex and solidify the nickel. The specific operation is as follows:

[0026] S1. Pretreatment: Adjust the pH of the nickel-containing ammonium sulfate solution to 4-6 with 4N sulfuric acid;

[0027] S2, nickel precipitation: according to the volume ratio of ammonium sulfide solution to ammonium sulfate solution of 1:500-2000, add 5-20% ammonium sulfide solution by mass to the ammonium sulfate solution prepared in step S1, adjust the pH to 7-9 with 25% industrial ammonia water by mass, stir at a speed of 100-300 r / min for 2-4h, without solid-liquid separation, to obtain a nickel precipitation solution;

[0028] S3, oxidative decomposition of nickel: 1-20 mg / L of ozone is continuously pumped into the nickel precipitation liquid in step S2 by a gas pressure pump, and at the same time, a mass fraction of 1-30% of furamide solution is added according to the volume ratio of furamide solution to ammonium sulfate salt solution of 0.002-0.010:1. After stirring for 2-6 hours, the mixture is filtered with a filter element with a pore size of 0.2-0.5 μm to separate the nickel precipitate from the ammonium sulfate solution to obtain an ammonium sulfate salt solution with extremely low nickel content.

[0029] 1. Investigation on the effect of nickel precipitation with single thiram

[0030] The present invention uses fenamide as a nickel precipitation reagent, which can react with heavy metal nickel ions at room temperature to generate water-insoluble chelated salts to form precipitates, thereby achieving the purpose of removing heavy metal nickel ions. In order to prove the nickel precipitation effect of fenamide, the following single fenamide nickel precipitation effect test was carried out, and the operation was as follows:

[0031] The solid fenamide sample used in this experiment was prepared as a 30% by weight solution. Nickel pre-precipitation solution was obtained in batches from the same workshop. The pre-precipitation solution was treated according to the pretreatment steps of pH adjustment, oxidative complex breaking, and nickel fixation with fenamide. The test results are shown in Table 1.

[0032] Table 1 Effect of fenamide dosage on nickel precipitation effect of solutions with different nickel contents

[0033]

[0034]

[0035] From the data in Table 1, it can be seen that the nickel precipitation effect and filtration performance of the present invention using fenamide are good, and the formed precipitate does not dissolve back for a long time. It can be seen that the fenamide solution can capture heavy metal nickel ions, and no hydroxide precipitate is produced or the amount produced is very small during the precipitation reaction. Therefore, the use of fenamide to precipitate nickel can effectively prevent the occurrence of the nickel precipitate dissolution phenomenon.

[0036] 2. Investigation on the effect of nickel precipitation with ammonium sulfide + thiram

[0037] As shown in Table 1, the processing cost of using only fentanyl to precipitate nickel is high, so it is necessary to explore a combined nickel precipitation solution that can reduce the processing cost. The inventors, in combination with the equipment layout and process operating conditions in existing production, need to extend the nickel precipitation and dissolution time as much as possible so that the nickel content in the clear liquid passing through the precision filter meets the standard. Currently, it is considered that this dissolution time requires at least 3 hours. Under this precondition, ammonium sulfide is first used to completely precipitate nickel, and then different amounts of fentanyl precipitant are added to investigate the nickel precipitation and dissolution phenomenon. The test results are shown in Table 2.

[0038] Table 2 Effect of fenamide dosage on nickel precipitation effect

[0039]

[0040]

[0041] From the results in Table 2, it can be seen that the addition of fenamide after the nickel is completely precipitated with ammonium sulfide can effectively prolong the re-dissolution time interval. As the amount of fenamide increases, the re-dissolution time interval becomes longer. The cost of fenamide required to maintain precipitation for 2 hours without re-dissolution is 4.425 yuan / m 3 Solution, at this consumption, if the Ni index is relaxed to 0.01g / L, it can be maintained for 4 hours; the cost of using fenamide required to maintain precipitation for 4 hours without re-dissolving is 13.275 yuan / m 3 Solution, at this consumption, the Ni index can be relaxed to 0.01g / L and can be maintained for more than 6 hours. 3 In a solution containing 0.18 g / L of nickel, when using only fenamide to precipitate nickel, the amount of fenamide used is 2.813 kg. When using a mixed reagent to precipitate nickel, the amount of fenamide required to maintain complete non-redissolution for 2 hours is 0.375 kg, which is 13.3% of the amount used when using only fenamide. It can be seen that the combined solution of ammonium sulfide nickel precipitation and fenamide nickel fixation in the present invention not only greatly prolongs the redissolution time, but also greatly reduces the processing cost.

[0042] Example 1:

[0043] The treatment object of this embodiment is the raffinate produced by the hydrometallurgical liquid extraction, in which the (NH4)2SO4 concentration is 42.6g / L, Ni + The concentration is 0.44g / L and the processing volume per cycle is 20m 3 .

[0044] A method for treating nickel precipitate re-dissolution in ammonium sulfate solution comprises the following steps:

[0045] S1. Pretreatment: Adjust the pH of the nickel-containing ammonium sulfate solution to 4.5 with 4N sulfuric acid;

[0046] S2, nickel precipitation: add 0.2m of ammonium sulfide solution with a mass fraction of 10% to the ammonium sulfate solution prepared in step S1. 3 The pH value was adjusted to 7.5 with 20% industrial ammonia water, and the mixture was stirred at 300 rpm for 4 hours to obtain a nickel precipitation solution.

[0047] S3, oxidative decomposition of nickel: 10 mg / L of ozone is continuously pumped into the nickel precipitation liquid in step S2 by a gas pressure pump, and at the same time, a 2% mass fraction of furamide solution is added according to the volume ratio of furamide solution to ammonium sulfate salt solution of 0.002 to 0.010:1. After stirring for 4 hours, the mixture is filtered with a filter element with a pore size of 0.5 μm to separate the nickel precipitate from the ammonium sulfate solution to obtain an ammonium sulfate salt solution with extremely low nickel content.

[0048] The nickel ion concentration in the treated liquid is 0.0003g / L, the nickel ion concentration is 0.0003g / L after standing for 4 hours, and the nickel ion concentration is 0.0003g / L after 8 hours. The Ni in the treated liquid does not dissolve again, and the product after concentration and crystallization meets the standards of high-quality ammonium sulfate.

[0049] Example 2:

[0050] The difference between this embodiment and embodiment 1 is that the treatment object of this embodiment is the raffinate produced by the hydrometallurgical liquid extraction, in which the (NH4)2SO4 concentration is 35.2g / L, and Ni + The concentration is 0.26g / L.

[0051] The nickel ion concentration in the treated liquid is 0.0002 g / L, the nickel ion concentration is 0.0002 g / L after standing for 4 hours, and the nickel ion concentration is 0.0002 g / L after 8 hours. The product after concentration and crystallization meets the standards of high-quality ammonium sulfate.

[0052] Comparative Example 1:

[0053] The difference between this comparative example and Example 1 is that: the pH of the nickel-containing ammonium sulfate solution is adjusted to 2.0 with 4N sulfuric acid in the pretreatment;

[0054] The nickel ion concentration in the treated liquid is 0.06 g / L. After standing for 4 hours, the nickel ion concentration is 0.06 g / L. After 8 hours, the nickel ion concentration is 0.06 g / L. It can be seen that the nickel ion purification depth is insufficient at this pH, and the product after concentration and crystallization does not meet the standard of high-quality ammonium sulfate.

[0055] Comparative Example 2:

[0056] The difference between this comparative example and Example 1 is that: in S3, air is continuously pumped into the nickel-precipitated solution in step S2 by a gas pressure pump;

[0057] The nickel ion concentration in the treated liquid was 0.0003 g / L, the nickel ion concentration was 0.002 g / L after standing for 4 hours, and the nickel ion concentration was 0.0086 g / L after 8 hours. The product after concentration and crystallization did not meet the standards for superior ammonium sulfate.

[0058] Comparative Example 3:

[0059] The treatment object of this embodiment is the raffinate produced by the hydrometallurgical liquid extraction, in which the (NH4)2SO4 concentration is 42.6g / L, Ni + The concentration is 0.44g / L and the processing volume per cycle is 20m 3 .

[0060] A method for treating nickel precipitate re-dissolution in ammonium sulfate solution comprises the following steps:

[0061] S1. Pretreatment: Adjust the pH of the nickel-containing ammonium sulfate solution to 4.5 with 4N sulfuric acid;

[0062] S2, nickel precipitation: add 0.2m of ammonium sulfide solution with a mass fraction of 10% to the ammonium sulfate solution prepared in step S1. 3 The pH value was adjusted to 7.5 with 20% industrial ammonia water, and the mixture was stirred at 300 rpm for 4 hours to obtain a nickel precipitation solution.

[0063] S3, oxidative decomposition of nickel: 10 mg / L of ozone is continuously pumped into the nickel precipitated solution in step S2 by a gas pressure pump. After stirring for 4 hours, the solution is filtered with a filter element with a pore size of 0.5 μm to separate the nickel precipitate from the ammonium sulfate solution to obtain an ammonium sulfate salt solution with extremely low nickel content.

[0064] The nickel ion concentration in the treated liquid was 0.0003 g / L, the nickel ion concentration was 0.0007 g / L after standing for 4 hours, and the nickel ion concentration was 0.0032 g / L after 8 hours. The Ni in the treated liquid showed a re-dissolution phenomenon, and the product after concentration and crystallization did not meet the standards for superior ammonium sulfate.

[0065] The above embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and replacements made by technicians in this field on the basis of the present invention fall within the scope of protection required by the present invention.

Claims

1. A method for treating nickel precipitate re-dissolution in ammonium sulfate solution, characterized in that: The following steps are involved: S1. Pretreatment: adjusting the pH of the nickel-containing ammonium sulfate solution to 4-6; S2, nickel precipitation: adding ammonium sulfide solution to the ammonium sulfate solution prepared in step S1, adjusting the pH to 7-9, stirring, and obtaining a nickel precipitation solution; S3, oxidative decomposition of nickel: ozone is introduced into the nickel precipitation solution of step S2, and thiamin solution is added at the same time. After stirring, the solution is filtered to obtain an ammonium sulfate solution with extremely low nickel content.

2. The method for treating nickel precipitate re-dissolution in ammonium sulfate solution according to claim 1, wherein: The ammonium sulfate concentration of the nickel-containing ammonium sulfate salt solution in step S1 is 20-200 g / L, and the nickel ion concentration is 0.001-1.0 g / L.

3. The method for treating nickel precipitate re-dissolution in ammonium sulfate solution according to claim 1, wherein: The acid used for adjusting the pH in steps S1 and S2 is sulfuric acid, and the base is industrial ammonia water.

4. The method for treating nickel precipitate re-dissolution in ammonium sulfate solution according to claim 1, wherein: The mass fraction of the ammonium sulfide solution in step S2 is 5-20%; the volume ratio of the ammonium sulfide solution to the ammonium sulfate salt solution is 1:500-2000.

5. The method for treating nickel precipitate re-dissolution in ammonium sulfate solution according to claim 1, wherein: The stirring time in step S2 is 2 to 4 hours, and the stirring speed is 100 to 300 r / min.

6. The method for treating nickel precipitate re-dissolution in ammonium sulfate solution according to claim 1, wherein: The amount of ozone introduced in step S3 is 1-20 mg / L.

7. The method for treating nickel precipitate re-dissolution in ammonium sulfate solution according to claim 1, wherein: The mass fraction of the fenamide solution in step S3 is 1 to 30%.

8. The method for treating nickel precipitate re-dissolution in ammonium sulfate solution according to claim 1 or 7, characterized in that: The volume ratio of the fenamide solution to the ammonium sulfate solution in step S3 is 0.002 to 0.010:

1.

9. The method for treating nickel precipitate re-dissolution in ammonium sulfate solution according to claim 1, wherein: The stirring time in step S3 is 2 to 6 hours.

10. The method for treating nickel precipitate re-dissolution in ammonium sulfate solution according to claim 1, characterized in that: The ozone in step S3 is introduced into the nickel-precipitated liquid by a gas pressure pump.

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