Method for treating nickel-containing waste residues generated by nitrogen trifluoride electrolysis

Abstract

The invention relates to a method for treating nickel-containing waste residues generated by nitrogen trifluoride electrolysis. The method comprises the following steps: crushing fluorine-containing nickel residues into solid powder; dissolving the fluorine-containing nickel slag solid powder by using an oxidizing solution, controlling the temperature to be 30-60 DEG C and the pH to be 3.5-5, and stirring until the fluorine-containing nickel slag is completely dissolved, so as to obtain a mixed turbid liquid a containing nickel fluoride, ammonium bifluoride and ferric hydroxide; filtering to obtain ferric hydroxide precipitate and a mixed solution b; adjusting the pH value of the mixed solution b to 7-9 by using a sodium hydroxide solution, and filtering to obtain a nickel fluoride solid and a mixed solution c; heating and concentrating the mixed solution c, and cooling and crystallizing to obtain a sodium fluoride crystal and an ammonium fluoride solution; and evaporating the ammonium fluoride solution to dryness to obtain ammonium fluoride crystals. According to the method, comprehensive recycling of the nickel-containing waste residues generated in the nitrogen trifluoride electrolysis process is achieved, the main nickel element is recycled, and it is ensured that other valuable elements such as fluorine and ammonium in the waste residues are effectively extracted and reused.

Description

Technical Field

[0001] The invention relates to the technical field of process methods for recovering nickel-containing waste slag, and in particular to a method for treating nickel-containing waste slag produced by electrolysis of nitrogen trifluoride. Background Art

[0002] High-purity nitrogen trifluoride gas is an excellent plasma etching gas, so it occupies an important position in many industries such as integrated circuits and semiconductor manufacturing. At present, the electrolytic method is generally used in the industry to prepare high-purity nitrogen trifluoride. The electrolyte is a mixture of anhydrous hydrogen fluoride and ammonium bifluoride, and the anode is a nickel plate. However, during the electrolysis of nitrogen trifluoride, nickel will gradually be dissolved and corroded by the electrolyte. A small amount of nickel dissolved in the electrolyte will be electroplated at the cathode, and most of it will accumulate at the bottom of the electrolytic cell in the form of salt or metal, which not only consumes part of the electrolyte but also causes the anode area to gradually decrease, thereby affecting the efficiency of electrolysis. Therefore, the bottom nickel slag must be treated regularly and the nickel plate must be replaced.

[0003] The composition of nickel slag is relatively complex, of which about 60%-70% is nickel fluoride in the solid. Nickel, as a precious metal, has a high economic value, so it must be recycled. At the same time, in the process of recycling nickel, other by-products such as ammonium fluoride should be considered to be recycled to better reduce production costs. At present, there are mainly the following methods for treating electrolytic waste slag of nitrogen trifluoride: one is to sell it in the form of nickel slag and hand it over to a professional company for treatment. This method is very low in price and cannot well reduce the company's production costs; the other is to dissolve the electrolytic nickel-containing waste slag with water, and then separate the solid and liquid to obtain an ammonium fluoride aqueous solution and solid waste slag containing fluorine, nickel and iron. The solid slag still needs to be handled by a professional company. Another method is to dissolve the nickel slag with hydrofluoric acid, add sulfuric acid to the electrolyte, and use electrolysis to recover metallic nickel. This treatment method consumes a lot of energy and has high requirements for the electrolyte. If the iron is not completely removed, the electrolytically deposited nickel will contain a large amount of iron, which will also affect the external sale price. Chinese patent CN114349079A provides a resource treatment method for nickel slag solid waste in the electrolytic production of nitrogen trifluoride gas, comprising the following steps: washing of nickel slag, dissolution of nickel slag, complexation of nickel and ammonia, washing of Fe(OH)3 precipitate, preparation of Ni(OH)2 product and treatment of colorless filtrate. However, this method adds sulfuric acid and excess ammonia water to the electrolyte, which consumes a lot of energy and costs, and the total recovery rate of each element in the nickel slag is low.

[0004] Chinese patent CN112645396B discloses a method for treating fluorine-containing nickel slag produced during the preparation of nitrogen trifluoride, which realizes the recovery and recycling of nickel metal resources and ammonium fluoride. However, in order to dissolve or extract the nickel element in the nickel slag, strong acid hydrofluoric acid is added as a solvent or catalyst. These fluorine-containing substances are not only costly, but also may cause additional environmental pollution during the treatment process. Summary of the invention

[0005] The object of the present invention is to provide a method for treating nickel-containing waste slag produced by electrolysis of nitrogen trifluoride, which realizes the recovery of all substances in the nickel slag without the need to add fluorine-containing substances, and the main product is easy to prepare and has high purity.

[0006] The specific technical scheme of the method for treating nickel-containing waste slag produced by electrolysis of nitrogen trifluoride of the present invention is as follows:

[0007] A method for treating nickel-containing waste slag produced by electrolysis of nitrogen trifluoride comprises the following steps:

[0008] S1, crushing the fluorine-containing nickel slag mixture;

[0009] S2, dissolving the fluorine-containing nickel slag solid powder with an oxidizing solution, controlling the temperature at 30°C-60°C, controlling the pH at 3.5-5, stirring until the fluorine-containing nickel slag is completely dissolved, and obtaining a mixed suspension a containing nickel fluoride, ammonium bifluoride, and ferric hydroxide;

[0010] S3, filtering to obtain iron hydroxide precipitate and mixed solution b;

[0011] S4, adjusting the pH value of the mixed solution b to 7-9 with a sodium hydroxide solution, filtering, and obtaining a nickel fluoride solid and a mixed solution c;

[0012] S5, heating and concentrating the mixed solution c, and cooling and crystallizing to obtain sodium fluoride crystals and ammonium fluoride solution;

[0013] S6. Evaporating the ammonium fluoride solution to dryness to obtain ammonium fluoride crystals.

[0014] Preferably, in step S2, the oxidizing solution is a hydrogen peroxide solution, and the mass concentration of the hydrogen peroxide solution is 30%.

[0015] Preferably, in step S2, the mass ratio of the hydrogen peroxide solution to the fluorine-containing nickel slag is 2:1-3:1.

[0016] Preferably, in step S4, the concentration of the sodium hydroxide solution is 1-1.5 mol / L.

[0017] Preferably, in step S5, the heating concentration temperature is 100°C, and the cooling crystallization temperature is 10°C.

[0018] Preferably, in step S6, the evaporation temperature is 120°C.

[0019] Preferably, in step S1, the fluorine-containing nickel slag is nickel slag containing electrolyte.

[0020] Preferably, the mass content of electrolyte in the nickel slag containing electrolyte is 50-60%, the electrolyte includes ammonium bifluoride and hydrogen fluoride, and the solid nickel slag includes 60-70% nickel fluoride and 10-20% ferric fluoride or ferrous fluoride.

[0021] The method of treating nickel-containing waste slag produced by electrolysis of nitrogen trifluoride according to the present invention has the following beneficial effects:

[0022] 1. In the traditional treatment method, in order to dissolve or extract the nickel element in the nickel slag, it is often necessary to add strong acids such as hydrofluoric acid as solvents or catalysts. However, these fluorine-containing substances are not only costly, but also may cause additional environmental pollution during the treatment process. The present invention cleverly utilizes the original fluorine-containing electrolyte in the electrolytic waste slag, and then adds the strong oxidizing property of the hydrogen peroxide solution to directly dissolve the nickel slag without adding additional fluorine-containing substances, thereby reducing the treatment cost and reducing the potential harm to the environment.

[0023] 2. The core advantage of the present invention is that it realizes the comprehensive recycling of nickel-containing waste slag produced during the electrolysis of nitrogen trifluoride. Not only the main nickel element is recovered, but also other valuable elements in the waste slag, such as fluorine and ammonium, are effectively extracted and reused. This comprehensive recycling strategy not only reduces resource waste, but also greatly reduces the risk of environmental pollution, which is in line with the concept of green chemistry and circular economy.

[0024] 3. Hydrogen peroxide (H2O2) as a green oxidant plays a key role in the present invention. Its oxidizing property is better than the traditional air oxidation method, and it can quickly remove the divalent iron ions (Fe 2+ ) is oxidized to ferric ion (Fe 3+ ), thus promoting the subsequent precipitation of iron and extraction of nickel. This efficient oxidation process not only improves the processing efficiency, but also ensures the full recovery of nickel in the nickel slag.

[0025] 4. The present invention successfully produces high-purity nickel fluoride products by precisely controlling the pH value of the solution and using effective separation techniques such as filtration and crystallization. During the entire treatment process, the iron impurities in the nickel slag are effectively removed by the oxidation of hydrogen peroxide and the adjustment of the pH value, so that the iron content of the final product is extremely low. DETAILED DESCRIPTION

[0026] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation method, structure, characteristics and effects of the present invention are described in detail below in combination with the preferred embodiments.

[0027] In the following examples, the verification of ferric hydroxide is carried out by utilizing the principle that under acidic conditions, reddish-brown ferric hydroxide reacts with potassium iodide solution to obtain purple-black iodine element.

[0028] The verification of nickel fluoride is carried out according to the method specified in HG / T 3734-2004 "Industrial Nickel Fluoride".

[0029] The verification of ammonium fluoride is carried out according to the method specified in GB / T 1276-1999 "Chemical Reagent Ammonium Fluoride".

[0030] Example 1

[0031] A method for treating nickel-containing waste slag produced by electrolysis of nitrogen trifluoride comprises the following steps:

[0032] S1. The fluorine-containing nickel slag containing electrolyte is crushed, wherein the solid matter is crushed into powder with a particle size of 0.1 mm-0.5 mm, the content of electrolyte in the fluorine-containing nickel slag is 60%, the electrolyte includes ammonium bifluoride and hydrogen fluoride, the solid nickel slag includes 60% nickel fluoride and 20% ferric fluoride or ferrous fluoride, and the remaining solid is copper fluoride and other impurities;

[0033] S2, adding 2 kg of 30% mass concentration hydrogen peroxide solution to 1 kg of nickel slag containing electrolyte, stirring at 1200 rotation speed, controlling the temperature at 35±5°C, detecting the pH value of the solution in real time, and controlling the pH at 4.0±0.5 until the nickel slag is completely dissolved to obtain a yellow mixed suspension a;

[0034] S3, filtering the mixed suspension a under reduced pressure to obtain iron hydroxide solid and a mixed solution b;

[0035] S4, slowly dropwise adding 1 mol / L sodium hydroxide solution into the mixed solution b, adjusting the pH value to 7, gradually precipitating green nickel fluoride solid, standing for 1 hour, filtering, and obtaining green nickel fluoride solid and mixed solution c;

[0036] S5, heating and concentrating the mixed solution c at a heating temperature of 100° C., and then cooling to 10° C. for crystallization to obtain white sodium fluoride crystals and a supernatant ammonium fluoride solution;

[0037] S6. Evaporating the supernatant ammonium fluoride solution to dryness at an evaporation temperature of 120° C. to obtain white ammonium fluoride crystals with an ammonium fluoride content of 98.1%.

[0038] After testing, the overall recovery rate of each element in the solution reached 97.4%.

[0039] Example 2

[0040] A method for treating nickel-containing waste slag produced by electrolysis of nitrogen trifluoride comprises the following steps:

[0041] S1. The fluorine-containing nickel slag containing electrolyte is crushed, wherein the solid matter is crushed into a solid powder with a particle size of 0.1 mm-0.5 mm, the content of electrolyte in the fluorine-containing nickel slag is 55%, the electrolyte includes ammonium bifluoride and hydrogen fluoride, the solid nickel slag includes 70% nickel fluoride and 10% ferric fluoride or ferrous fluoride, and the remaining solid is copper fluoride and other impurities;

[0042] S2, adding 3 kg of 30% mass concentration hydrogen peroxide solution to 1 kg of nickel slag containing electrolyte, stirring at 1200 rotation speed, controlling the temperature at 45±5°C, detecting the pH value of the solution in real time, and controlling the pH at 4.0±0.5 until the nickel slag is completely dissolved to obtain a yellow mixed suspension a;

[0043] S3, filtering the mixed suspension a under reduced pressure to obtain iron hydroxide solid and a mixed solution b;

[0044] S4, slowly dropwise adding 1.5 mol / L sodium hydroxide solution into the mixed solution b, adjusting the pH value to 8, gradually precipitating green nickel fluoride solid, standing for 1 hour, filtering, and obtaining green nickel fluoride solid and mixed solution c;

[0045] S5, heating and concentrating the mixed solution c at a heating temperature of 100° C., and then cooling to 25° C. for crystallization to obtain white sodium fluoride crystals and a supernatant ammonium fluoride solution;

[0046] S6. Evaporate the supernatant ammonium fluoride solution to dryness at an evaporation temperature of 120° C. to obtain white ammonium fluoride crystals with an ammonium fluoride content of 98.3%.

[0047] After testing, the overall recovery rate of each element in the solution reached 96.3%.

[0048] Example 3

[0049] A method for treating nickel-containing waste slag produced by electrolysis of nitrogen trifluoride comprises the following steps:

[0050] S1. The fluorine-containing nickel slag containing electrolyte is crushed, wherein the solid matter is crushed into a solid powder with a particle size of 0.1 mm-0.5 mm, the content of electrolyte in the fluorine-containing nickel slag is 50%, the electrolyte includes ammonium bifluoride and hydrogen fluoride, the solid nickel slag includes 63% nickel fluoride and 15% ferric fluoride or ferrous fluoride, and the remaining solid is copper fluoride and other impurities;

[0051] S2, adding 2.5 kg of 30% mass concentration hydrogen peroxide solution to 1 kg of nickel slag containing electrolyte, stirring at 1200 rotation speed, controlling the temperature at 55±5°C, detecting the pH value of the solution in real time, and controlling the pH at 4.5±0.5 until the nickel slag is completely dissolved to obtain a yellow-brown mixed suspension a;

[0052] S3, the mixed suspension a is filtered under reduced pressure to obtain a reddish brown solid and a mixed solution b, and the solid is ferric hydroxide precipitate as determined by titration;

[0053] S4, slowly dropwise add 1 mol / L sodium hydroxide solution to the mixed solution b, adjust the pH value to 9, gradually precipitate a green solid, let stand for 1 hour, filter, obtain a green solid and a mixed solution c, and determine by titration that the solid substance is nickel fluoride;

[0054] S5, heating and concentrating the mixed solution c at a heating temperature of 110° C., and then cooling to 20° C. for crystallization to obtain white sodium fluoride crystals and a supernatant ammonium fluoride solution;

[0055] S6. Evaporate the supernatant ammonium fluoride solution to dryness at an evaporation temperature of 120° C. to obtain white ammonium fluoride crystals. The crystals are determined to be ammonium fluoride by titration, and the content of ammonium fluoride is 98.0%.

[0056] After testing, the overall recovery rate of each element in the solution reached 98.5%.

[0057] The core advantage of the present invention is that it realizes the comprehensive recycling of nickel-containing waste slag produced during the electrolysis of nitrogen trifluoride. Not only the main nickel element is recovered, but also other valuable elements in the waste slag, such as fluorine and ammonium, are effectively extracted and reused. This comprehensive recycling strategy not only reduces resource waste, but also greatly reduces the risk of environmental pollution, which is in line with the concept of green chemistry and circular economy.

[0058] Comparative Example 1

[0059] Compared with Example 3, the only difference is that nickel slag without electrolyte is used in S1, and the remaining steps and experimental conditions are consistent with Example 3. After the experiment, each substance was detected, and the overall recovery rate of each element in the solution was only 36%.

[0060] In the traditional treatment method, in order to dissolve or extract the nickel element in the nickel slag, it is often necessary to add strong acids such as hydrofluoric acid as solvents or catalysts. However, these fluorine-containing substances are not only expensive, but also may cause additional environmental pollution during the treatment process. The present invention cleverly utilizes the original electrolyte in the electrolytic waste slag, and then adds the strong oxidizing property of the hydrogen peroxide solution to directly dissolve the nickel slag without adding additional fluorine-containing substances, thereby reducing the treatment cost and reducing the potential harm to the environment.

[0061] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for treating nickel-containing waste slag produced by electrolysis of nitrogen trifluoride, characterized in that: The following steps are involved: S1, crushing the fluorine-containing nickel slag mixture; S2, dissolving the fluorine-containing nickel slag solid powder with an oxidizing solution, controlling the temperature at 30°C-60°C, controlling the pH at 3.5-5, stirring until the fluorine-containing nickel slag is completely dissolved, and obtaining a mixed suspension a containing nickel fluoride, ammonium bifluoride, and ferric hydroxide; S3, filtering to obtain iron hydroxide precipitate and mixed solution b; S4, adjusting the pH value of the mixed solution b to 7-9 with a sodium hydroxide solution, filtering, and obtaining a nickel fluoride solid and a mixed solution c; S5, heating and concentrating the mixed solution c, and cooling and crystallizing to obtain sodium fluoride crystals and ammonium fluoride solution; S6. Evaporating the ammonium fluoride solution to dryness to obtain ammonium fluoride crystals.

2. A method for treating nickel-containing waste slag produced by electrolysis of nitrogen trifluoride according to claim 1, characterized in that: In step S2, the oxidizing solution is a hydrogen peroxide solution, and the mass concentration of the hydrogen peroxide solution is 30%.

3. A method for treating nickel-containing waste slag produced by electrolysis of nitrogen trifluoride according to claim 2, characterized in that: In step S2, the mass ratio of the hydrogen peroxide solution to the fluorine-containing nickel slag is 2:1-3:

1.

4. The method for treating nickel-containing waste slag produced by electrolysis of nitrogen trifluoride according to claim 1, characterized in that: In step S4, the concentration of the sodium hydroxide solution is 1-1.5 mol / L.

5. The method for treating nickel-containing waste slag produced by electrolysis of nitrogen trifluoride according to claim 1, characterized in that: In step S5, the heating concentration temperature is 100°C, and the cooling crystallization temperature is 10°C.

6. The method for treating nickel-containing waste slag produced by electrolysis of nitrogen trifluoride according to claim 1, characterized in that: In step S6, the evaporation temperature is 120°C.

7. The method for treating nickel-containing waste slag produced by electrolysis of nitrogen trifluoride according to claim 1, characterized in that: In step S1, the fluorine-containing nickel slag mixture is nickel slag containing electrolyte.

8. The method for treating nickel-containing waste slag produced by electrolysis of nitrogen trifluoride according to claim 7, characterized in that: The mass content of the electrolyte in the nickel slag containing the electrolyte is 50%-60%, the electrolyte comprises ammonium bifluoride and hydrogen fluoride, and the solid nickel slag comprises 60%-70% of nickel fluoride and 10%-20% of ferric fluoride or ferrous fluoride.