A method for removing impurities from a fluorine ammonium salt solution, and a method for producing a fluorine ammonium salt

Abstract

The present application relates to a kind of fluorine ammonium salt solution impurity removal method, fluorine ammonium salt preparation method, belong to fluorine chemical technology field.The fluorine ammonium salt solution impurity removal method of the present application, first fluorine ammonium salt solution and fluorine silicic acid solution are mixed, the mixed solution with pH 2~3 is obtained, then lead compound and mixed solution are mixed, lead compound produces lead ion in liquid environment, and then lead ion and phosphate ion and sulfate ion in mixed solution occur precipitation reaction, then excess lead ion is removed using lead adsorbent, finally solid-liquid separation is carried out, and impurity removal liquid is obtained.The fluorine ammonium salt solution impurity removal method of the present application is simple to operate, can efficiently remove phosphate ion and sulfate ion in fluorine ammonium salt solution and / or fluorine silicic acid solution, without introducing other impurity ions.

Description

TECHNICAL FIELD

[0001] The application relates to a method for removing impurities from a fluorine ammonium salt solution and a preparation method of the fluorine ammonium salt, and belongs to the technical field of fluorine chemical industry. BACKGROUND

[0002] When fluorosilicic acid by-produced in phosphate fertilizer production is used to produce ammonium fluoride and ammonium bifluoride, the fluorosilicic acid needs to be first ammonolyzed into ammonium fluoride and silicon dioxide, and then the ammonium fluoride solution is obtained by filtering out the silicon dioxide, and the ammonium fluoride solution is cooled, crystallized and separated to obtain the ammonium fluoride and the ammonium bifluoride; the fluorosilicic acid by-produced in the phosphate fertilizer production is mainly prepared by absorbing the tail gas of the wet-process phosphoric acid, and the wet-process phosphoric acid production process comprises phosphorite decomposition and phosphoric acid concentration, therefore, the fluorosilicic acid by-produced in the phosphate fertilizer production inevitably contains impurity components such as phosphate and sulfate. Therefore, when the fluorosilicic acid by-produced in the phosphate fertilizer production is used to produce the ammonium fluoride and the ammonium bifluoride, the water-soluble phosphorus and sulfur impurities in the fluorosilicic acid raw material will enter the ammonium fluoride solution after the ammonolysis of the fluorosilicic acid raw material, and the phosphorus and sulfur impurities will be cyclically enriched in the ammonium fluoride mother liquor after the cooling and crystallization, and salts such as ammonium phosphate and ammonium sulfate are generated, and the ammonium phosphate and the ammonium sulfate reaching the saturation degree will be separated out together with the main product to generate a mixture of the main product, the ammonium phosphate and the ammonium sulfate, so that the main content of the main product is low, and the product quality is reduced.

[0003] At present, in the production process of the ammonium fluoride and the ammonium bifluoride, the production enterprises mainly remove the phosphorus and the sulfur from the fluorosilicic acid raw material, and the commonly used chemical phosphorus removal agents are aluminum salt, iron salt, iron filings, calcium salt and the like. Patent document DE1942925A1 discloses a method for separating phosphate from fluorosilicic acid for producing ammonium fluoride, and the phosphate is removed from the fluorosilicic acid in the form of FePO4 by adding the oxide, hydroxide or hydroxide oxide of trivalent iron into the fluorosilicic acid and adjusting the pH to 2-4 by ammonia gas. Patent document US3870786A adopts a water-soluble aluminum salt, and adjusts the pH to above 3 by using ammonia water, sodium hydroxide, sodium carbonate, potassium carbonate or sodium hydroxide to precipitate the phosphate. However, when the phosphate is precipitated by using iron or aluminum, the acidity cannot be too high, and the HPO4 2- generated in the strong acid environment cannot completely precipitate the phosphate. Moreover, the solubility of the sulfate of iron and aluminum is high, and additional addition of barium salt and other chemical reagents is needed to precipitate the sulfate, and the use of multiple chemical reagents will cause more impurity ions to enter the system.

[0004] Chinese patent document CN114804030A discloses a method and device for preparing anhydrous hydrogen fluoride. The invention uses fluorosilicic acid, a byproduct of the phosphate fertilizer industry, as a fluorine source to produce anhydrous hydrogen fluoride. After reacting with ammonia water, the fluorosilicic acid is treated to remove phosphorus and sulfur to obtain an ammonium fluorosilicate solution. The ammonium fluorosilicate solution is reacted with ammonia water, and then concentrated and decomposed by evaporation and heat to obtain an ammonium hydrogen fluoride melt. The ammonium hydrogen fluoride melt is reacted with sodium fluoride, and then cooled and crystallized to obtain sodium hydrogen fluoride paste. The sodium hydrogen fluoride paste is dried and decomposed by heat to obtain crude hydrogen fluoride gas, which is then purified to obtain anhydrous hydrogen fluoride. In this method, iron oxide and / or iron fluorosilicate are used to remove phosphate ions from the ammonium fluorosilicate solution, and lead oxide and / or lead fluorosilicate are used to remove sulfate ions from the ammonium fluorosilicate solution. Therefore, two chemical reagents are also needed to remove phosphate and sulfate ions in this patent, and there is still a problem of introducing more impurity ions, and the efficiency of impurity removal is low. Patent document US3201193A removes phosphate ions from fluorosilicic acid solution by bubbling ammonia gas into the solution until saturation, and the phosphate ions are removed in the form of ammonium phosphate. However, this method consumes a large amount of high-purity ammonia, increasing production costs.

[0005] Therefore, there is an urgent need to develop an efficient and low-cost method for removing phosphate and sulfate ions from fluorosilicic acid solution, ammonium fluoride solution, and ammonium hydrogen fluoride solution. SUMMARY

[0006] The present application aims to provide a method for removing impurities from a fluorine-ammonium salt solution, which can solve the problems of low efficiency and high cost in removing phosphate and sulfate ions from fluorosilicic acid solution, ammonium fluoride solution, and ammonium hydrogen fluoride solution.

[0007] Another object of the present application is to provide a method for preparing a fluorine-ammonium salt, which can solve the problems of complex preparation process and high impurity content in the product due to the low efficiency of removing phosphate and sulfate ions in the preparation of fluorine-ammonium salt.

[0008] To achieve the above objects, the technical scheme adopted by the method for removing impurities from a fluorine-ammonium salt solution of the present application is as follows:

[0009] A method for removing impurities from a fluorine-ammonium salt solution, comprising the following steps:

[0010] (1) mixing fluorine-ammonium salt solution and fluorosilicic acid solution to obtain a mixture with a pH of 2-3; the fluorine-ammonium salt is ammonium fluoride and / or ammonium hydrogen fluoride; the mixture contains phosphate ions and sulfate ions;

[0011] (2) mixing the mixture with a lead compound and then removing lead ions in the system after the mixing reaction using a lead adsorbent to obtain a decontaminated solution; the lead compound is one or any combination of lead oxide, lead hydroxide, and lead fluorosilicate.

[0012] The impurity removal method of the fluoroammonium salt solution of the present application first mixes the fluoroammonium salt solution and the fluosilicic acid solution to obtain a mixed solution with pH of 2-3, then mixes the lead compound with the mixed solution, the lead compound generates lead ions in the liquid environment, the lead ions further react with the phosphate ions and the sulfate ions in the mixed solution to precipitate, then removes the excessive lead ions by using a lead adsorbent, and finally performs solid-liquid separation to obtain a decontaminated solution. The impurity removal method of the fluoroammonium salt solution of the present application is simple in operation and can efficiently remove the phosphate ions and the sulfate ions in the fluoroammonium salt solution and / or the fluosilicic acid solution without introducing other impurity ions.

[0013] In step (1), when the pH of the mixed solution is less than 2, HPO4 2- will be generated, which causes incomplete precipitation of the phosphate, and when the pH of the mixed solution is greater than 3, silicon dioxide will be precipitated, which affects the decontamination effect.

[0014] The fluoroammonium salt solution used in the present application is fluoroammonium salt mother liquor produced in the production of ammonium fluoride, ammonium bifluoride mother liquor produced in the production of ammonium bifluoride, or a mixture of the fluoroammonium salt mother liquor produced in the production of ammonium fluoride and the ammonium bifluoride mother liquor produced in the production of ammonium bifluoride.

[0015] Preferably, the pH of the fluoroammonium salt solution is 4.0-5.0.

[0016] Preferably, the mass fraction of the phosphate in the fluoroammonium salt solution is 0.05-0.88%, the mass fraction of the sulfate is 0.07-0.95%, and the mass fraction of the lead ions is 1 ppm-5 ppm.

[0017] The fluosilicic acid solution used in the present application mainly consists of water, fluosilicic acid, phosphate and sulfate. The fluosilicic acid solution used in the present application is a fluosilicic acid solution by-produced in the production of phosphate fertilizer.

[0018] Preferably, the mass fraction of the fluosilicic acid solution is 5%-20%. For example, the mass fraction of the fluosilicic acid solution is 15%-20%. The mass fraction of the fluosilicic acid in the fluosilicic acid solution by-produced in the production of phosphate fertilizer is generally 5%-20%, and the fluosilicic acid solution used in the present application is the fluosilicic acid solution by-produced in the production of phosphate fertilizer.

[0019] Preferably, the mass fraction of the phosphate in the fluosilicic acid solution is 0.03-0.1%, the mass fraction of the sulfate is 0.04-0.15%, and the mass fraction of the lead ions is 1 ppm-4 ppm.

[0020] Preferably, the lead oxide is selected from one or any combination of PbO, Pb2O3, Pb3O4. When the lead compound is added to the mixed solution for mixing reaction, PbO, Pb2O3, Pb3O4 or Pb(OH)2 first reacts with fluorosilicic acid in the mixed solution to form lead fluorosilicate, and the lead ion in the lead fluorosilicate then precipitates with phosphate and sulfate.

[0021] To avoid introducing impurities, the amount of the lead compound is determined according to the standard of just being able to precipitate the phosphate and sulfate contained in the system. Preferably, the amount of substance of lead element in the lead compound is a, the amount of substance of phosphate ion in the mixed solution is b, and the amount of substance of sulfate ion in the mixed solution is c, and a = x * b + y * c, x = 1.50-1.56, and y = 1.00-1.04.

[0022] Preferably, the temperature of the mixing reaction is 20-50°C. The end point of the mixing reaction can be determined by detecting the content of sulfate and phosphate in the system after the mixing reaction.

[0023] To accelerate the rate of the mixing reaction and the precipitation speed of the impurities, further preferably, the temperature of the mixing reaction is 40-50°C, and the time is 0.5-2h. For example, the temperature of the mixing reaction is 50°C, and the time is 0.5h.

[0024] Preferably, when the mixed solution and the lead compound are subjected to the mixing reaction, the pH of the system of the mixing reaction is controlled to be not more than 3. Controlling the pH of the system of the mixing reaction to be not more than 3 has the effects of avoiding the precipitation of silicon dioxide in the system and promoting the progress of the impurity removal reaction. During the mixing reaction, the lead compound can consume part of the fluorosilicic acid, which can cause the pH of the system of the mixing reaction to be greater than 3. To prevent the precipitation of silicon dioxide, a pH regulator needs to be added to control the pH of the system of the mixing reaction to be greater than 3. To avoid introducing impurities, preferably, when the mixed solution and the lead compound are subjected to the mixing reaction, a pH regulator is added to control the pH of the system of the mixing reaction to be not more than 3, and the pH regulator is fluorosilicic acid and / or a fluorosilicic acid solution.

[0025] Preferably, the lead adsorbent is activated carbon. The amount of the lead adsorbent is determined according to the standard of just being able to completely adsorb the lead ion. In the present application, the activated carbon can be obtained by commercial purchase.

[0026] Preferably, the mass ratio of the lead adsorbent to the lead compound is (3-4): 10.

[0027] It can be understood that when the lead adsorbent is used to remove the lead ions in the mixed reaction system, the mixed reaction system can be passed through an adsorption tower in which the lead adsorbent is fixed to remove the lead, or the lead adsorbent and the mixed reaction system can be mixed, and then solid-liquid separation is performed to remove the lead.

[0028] Preferably, the method for removing the lead ions in the mixed reaction system by using the lead adsorbent comprises the following steps: mixing the lead adsorbent and the mixed reaction system, and then performing solid-liquid separation to obtain a removal liquid. The solid obtained by the solid-liquid separation is lead phosphate, lead sulfate, a small amount of lead fluoride, the lead adsorbent, the lead adsorbent adsorbed lead fluorosilicate, and possibly lead dioxide, which can be harmlessly treated by high-temperature calcination.

[0029] In order to avoid the precipitation of silicon dioxide in the system when the lead adsorbent and the mixed reaction system are mixed, preferably, during the mixing of the lead adsorbent and the mixed reaction system, the pH of the system is controlled to be not greater than 3 by adding a pH regulator to the system, and the pH regulator is fluorosilicic acid and / or a fluorosilicic acid solution.

[0030] Preferably, the temperature for mixing the lead adsorbent and the mixed reaction system is 20-60°C, and the time is 0.5-2h. Further preferably, the temperature for mixing the lead adsorbent and the mixed reaction system is 50-60°C, and the time is 0.5-2h. For example, the temperature for mixing the lead adsorbent and the mixed reaction system is 50°C, and the time is 2h.

[0031] It can be understood that the liquid obtained by using the lead adsorbent to remove the lead ions in the mixed reaction system is the removal liquid.

[0032] The technical scheme adopted by the preparation method of the fluoroammonium salt of the present application is as follows:

[0033] The preparation method of a fluoroammonium salt comprises the following steps: performing an ammoniation reaction on the removal liquid obtained by the removal method of the fluoroammonium salt solution, then performing solid-liquid separation, and then performing crystallization on the liquid obtained by the solid-liquid separation to obtain the fluoroammonium salt.

[0034] The preparation method of the fluoroammonium salt of the present application adopts the removal liquid obtained by the removal method of the fluoroammonium salt solution to perform an ammoniation reaction, then performs solid-liquid separation, the solid obtained by the solid-liquid separation is white carbon black, and then the liquid obtained by the solid-liquid separation is crystallized to obtain the fluoroammonium salt. The fluoroammonium salt obtained by the preparation method of the fluoroammonium salt of the present application has high purity and low impurity content, and the preparation process is simple.

[0035] Preferably, the ammoniation reaction is a mixing reaction of the removal liquid and an ammoniation agent; and the ammoniation agent is ammonia gas and / or ammonia water.

[0036] To obtain the ammonium fluoride product and to reduce the introduction of impurities, preferably, the ratio of the molar amount of nitrogen atoms in the ammoniating agent to the molar amount of fluosilicic acid in the impurity-removing solution is (5-8):1. For example, the ratio of the molar amount of nitrogen atoms in the ammoniating agent to the molar amount of fluosilicic acid in the impurity-removing solution is (6-8):1. It can be understood that the molar amount of nitrogen atoms in the ammoniating agent is the molar amount of NH3 in the ammoniating agent.

[0037] Preferably, the temperature of the ammoniating reaction is 40-70°C and the time is 0.5-2h.

[0038] Preferably, the method for crystallization comprises the following steps: heating the liquid obtained by the solid-liquid separation to 150-180°C to evaporate and concentrate to a concentrated solution in which the mass fraction of the ammonium fluoride salt is 40-70%, and then lowering the concentrated solution to room temperature to crystallize, and solid-liquid separation, and the solid obtained by the solid-liquid separation is the ammonium fluoride salt. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 The flowchart of the method for preparing the ammonium fluoride salt of Example 3 of the present application. DETAILED DESCRIPTION

[0040] The technical solutions of the present application are further described below in combination with specific examples.

[0041] First, the method for removing impurities from the ammonium fluoride salt solution of the present application specifically comprises the following steps:

[0042] Example 1

[0043] The method for removing impurities from the ammonium fluoride salt solution of the present application specifically comprises the following steps:

[0044] (1) Take 1000g of the ammonium fluoride mother liquor produced in the production of ammonium fluoride, and detect that the mass fraction of phosphate and sulfate in the ammonium fluoride mother liquor is 0.34% and 0.85% respectively, the mass fraction of lead ions is 5ppm, and the pH of the ammonium fluoride mother liquor is 4.0; take an appropriate amount of the clarified fluosilicic acid solution with a mass fraction of 15% (fluosilicic acid solution produced by a certain factory as a byproduct of phosphate fertilizer), and detect that the mass fraction of phosphate and sulfate in the fluosilicic acid solution is 0.08% and 0.12% respectively, and the mass fraction of lead ions is 3ppm;

[0045] Then, add 1000g of the ammonium fluoride mother liquor into the clarified fluosilicic acid solution with a mass fraction of 15%, and stir uniformly to obtain a mixed solution with pH=2.5, in which the amount of substance of phosphate ions and sulfate ions is 0.038mol and 0.091mol respectively;

[0046] (2) 39.1 g of lead trioxide (the amount of substance of lead element in the lead trioxide is 0.169 mol) is added into the mixed solution, and stirred for 0.5 h at 50°C (in the process of stirring and reaction, the pH value of the reaction system is detected, when the pH value of the reaction system is 3, fluosilicic acid is added into the system to control the pH value of the reaction system at 3), then 15.6 g of activated carbon is added into the reacted system, and stirred for 2 h at 50°C (in the process of stirring, the pH value of the system is detected, when the pH value of the system is 3, fluosilicic acid is added into the system to control the pH value of the system at 3), then filtered, and the filtered liquid is the impurity-removed solution.

[0047] Example 2

[0048] The impurity-removing method of the fluoroammonium salt solution of the present example specifically comprises the following steps:

[0049] (1) 1000 g of ammonium fluoride mother liquor produced in the production of ammonium fluoride is taken, and the mass fraction of phosphoric acid radical and sulfuric acid radical in the ammonium hydrogen fluoride mother liquor is 0.59% and 0.67% respectively, the mass fraction of lead ion is 3 ppm, and the pH value of the ammonium hydrogen fluoride mother liquor is 4.5; an appropriate amount of mass fraction 5% clear fluosilicic acid solution is taken, and the mass fraction of phosphoric acid radical and sulfuric acid radical in the fluosilicic acid solution is 0.03% and 0.04% respectively, and the mass fraction of lead ion is 1 ppm;

[0050] Then 1000 g of ammonium hydrogen fluoride mother liquor is added into the mass fraction 5% clear fluosilicic acid solution, and stirred uniformly to obtain a mixed solution with pH = 3, and the amount of substance of phosphoric acid radical ion and sulfuric acid radical ion in the mixed solution is 0.064 mol and 0.073 mol respectively;

[0051] (2) 39.1 g of lead trioxide (the amount of substance of lead element in the lead trioxide is 0.169 mol) is added into the mixed solution, and stirred for 0.5 h at 50°C (in the process of stirring and reaction, the pH value of the reaction system is detected, when the pH value of the reaction system is 3, fluosilicic acid is added into the system to control the pH value of the reaction system at 3), then 15.6 g of activated carbon is added into the reacted system, and stirred for 2 h at 50°C (in the process of stirring, the pH value of the system is detected, when the pH value of the system is 3, fluosilicic acid is added into the system to control the pH value of the system at 3), then filtered, and the filtered liquid is the impurity-removed solution.

[0052] Example 3

[0053] The impurity-removing method of the fluoroammonium salt solution of the present example specifically comprises the following steps:

[0054] (1) Take 1000g of ammonium fluoride mother liquor produced in the production of ammonium fluoride, and detect that the mass fraction of phosphate and sulfate in the ammonium fluoride mother liquor is 0.88% and 0.95% respectively, the mass fraction of lead ions is 5ppm, and the pH of the ammonium fluoride mother liquor is 5.0; take an appropriate amount of 20% clear fluosilicic acid solution, and detect that the mass fraction of phosphate and sulfate in the fluosilicic acid solution is 0.1% and 0.15% respectively, and the mass fraction of lead ions is 4ppm;

[0055] Then 1000g of ammonium fluoride mother liquor is added into the 20% clear fluosilicic acid solution, and stirred uniformly to obtain a mixture with pH=2, in which the amount of substance of phosphate ions and sulfate ions is 0.094mol and 0.101mol respectively;

[0056] (2) 55.5g of lead tetroxide (the amount of substance of lead element in the lead tetroxide is 0.243mol) is added into the mixture, and stirred at 50°C for 0.5h (in the process of stirring reaction, the pH of the reaction system is detected, and when the pH of the reaction system is greater than 2, fluosilicic acid is added into the system to control the pH of the reaction system at 2); then 19.4g of activated carbon is added into the reacted system, and stirred at 50°C for 2h (in the process of stirring, the pH of the system is detected, and when the pH of the system is greater than 2, fluosilicic acid is added into the system to control the pH of the system at 2); then filtered, and the obtained liquid after filtration is the impurity removal liquid.

[0057] Example 4

[0058] The impurity removal method of the ammonium fluoride solution of the present example specifically comprises the following steps:

[0059] (1) Take 1000g of ammonium fluoride mother liquor produced in the production of ammonium fluoride, and detect that the mass fraction of phosphate and sulfate in the ammonium fluoride mother liquor is 0.05% and 0.07% respectively, the mass fraction of lead ions is 1ppm, and the pH of the ammonium fluoride mother liquor is 4.5; take an appropriate amount of 15% clear fluosilicic acid solution, and detect that the mass fraction of phosphate and sulfate in the fluosilicic acid solution is 0.08% and 0.12% respectively, and the mass fraction of lead ions is 3ppm;

[0060] Then 1000g of ammonium fluoride mother liquor is added into the 15% clear fluosilicic acid solution, and stirred uniformly to obtain a mixture with pH=2.5, in which the amount of substance of phosphate ions and sulfate ions is 0.007mol and 0.010mol respectively;

[0061] (2) 5.0 g of lead hydroxide (the amount of substance of lead element in the lead hydroxide is 0.021 mol) is added into the mixed solution, and the reaction is stirred at 40°C for 2 h (during the stirring reaction, the pH value of the reaction system is detected, and when the pH value of the reaction system is greater than 2.5, fluosilicic acid is added into the system to control the pH value of the reaction system at 2.5), then 2.0 g of activated carbon is added into the reacted system, and the stirring is carried out at 60°C for 0.5 h (during the stirring, the pH value of the system is detected, and when the pH value of the system is greater than 2.5, fluosilicic acid is added into the system to control the pH value of the system at 2.5), then filtration is carried out, and the obtained liquid after filtration is the impurity-removed solution.

[0062] Example 5

[0063] The impurity-removing method of the fluoroammonium salt solution of the present example specifically comprises the following steps:

[0064] (1) The step (1) of the present example is the same as the step (1) of the impurity-removing method of the fluoroammonium salt solution of Example 1;

[0065] (2) 34.3 g of lead oxide (the amount of substance of lead element in the lead oxide is 0.154 mol) is added into the mixed solution, and the reaction is stirred at 50°C for 0.5 h (during the stirring reaction, the pH value of the reaction system is detected, and when the pH value of the reaction system is greater than 2.5, fluosilicic acid is added into the system to control the pH value of the reaction system at 2.5), then 13.7 g of activated carbon is added into the reacted system, and the stirring is carried out at 50°C for 2 h (during the stirring, the pH value of the system is detected, and when the pH value of the system is greater than 2.5, fluosilicic acid is added into the system to control the pH value of the system at 2.5), then filtration is carried out, and the obtained liquid after filtration is the impurity-removed solution.

[0066] Comparative Example 1

[0067] The impurity-removing method of the present comparative example specifically comprises the following steps:

[0068] (1) An appropriate amount of clear fluosilicic acid solution with a mass fraction of 15% is taken, and it is detected that the mass fraction of phosphoric acid radical and sulfuric acid radical in the fluosilicic acid solution is 0.08% and 0.12% respectively; the mass of the fluosilicic acid solution is the same as that of the fluosilicic acid solution used in the preparation of the mixed solution in Example 1;

[0069] (2) adding an appropriate amount of lead oxide into the fluosilicic acid solution (the ratio of the mass of the lead oxide to the sum of the mass of the phosphate and sulfate in the fluosilicic acid solution is the same as the ratio of the mass of the lead oxide to the sum of the mass of the phosphate and sulfate in the mixed solution in Example 1) and stirring the reaction at 50°C for 0.5h (during the stirring reaction, the pH value of the reaction system is detected, when the pH value of the reaction system is greater than 2.5, fluosilicic acid is added into the system to control the pH value of the reaction system at 2.5), then adding activated carbon (the mass ratio of the activated carbon to the lead oxide is 3:10) into the system after the reaction, stirring the system at 50°C for 2h (during the stirring, the pH value of the system is detected, when the pH value of the system is greater than 2.5, fluosilicic acid is added into the system to control the pH value of the system at 2.5), then filtering, and the filtered liquid is the impurity-removing solution.

[0070] Comparative Example 2

[0071] The difference between the impurity-removing method of the fluoroammonium salt solution of the present comparative example and the impurity-removing method of the fluoroammonium salt solution of Example 1 is that in step (1) of the impurity-removing method of the fluoroammonium salt solution of the present comparative example, the amount of the fluosilicic acid solution is increased to obtain a mixed solution with pH = 1.5; and the amounts of the lead oxide and the activated carbon in step (2) are adjusted so that the ratio of the mass of the lead oxide to the sum of the mass of the phosphate and sulfate in the fluosilicic acid solution is the same as the ratio of the mass of the lead oxide to the sum of the mass of the phosphate and sulfate in the mixed solution in Example 1, and the mass ratio of the activated carbon to the lead oxide used in the present comparative example is 3:10.

[0072] Comparative Example 3

[0073] The impurity-removing method of the present comparative example specifically comprises the following steps:

[0074] (1) taking 1000g of fluoroammonium salt mother liquor (the fluoroammonium salt mother liquor in the present comparative example is the same as the fluoroammonium salt mother liquor used in Example 1);

[0075] (2) adding an appropriate amount of lead oxide into the fluoroammonium salt mother liquor (the ratio of the mass of the lead oxide to the sum of the mass of the phosphate and sulfate in the fluoroammonium salt mother liquor is the same as the ratio of the mass of the lead oxide to the sum of the mass of the phosphate and sulfate in the mixed solution in Example 1) and stirring the reaction at 50°C for 0.5h (during the stirring reaction, the pH value of the reaction system is detected, when the pH value of the reaction system is greater than 2.5, fluosilicic acid is added into the system to control the pH value of the reaction system at 2.5), then adding activated carbon (the mass ratio of the activated carbon to the lead oxide is 3:10) into the system after the reaction, stirring the system at 50°C for 2h (during the stirring, the pH value of the system is detected, when the pH value of the system is greater than 2.5, fluosilicic acid is added into the system to control the pH value of the system at 2.5), then filtering, and the filtered liquid is the impurity-removing solution.

[0076] Secondly, the preparation method of the fluoroammonium salt of the present application is specifically as follows:

[0077] Example 6

[0078] The preparation method of the fluoroammonium salt of the present example specifically includes the following steps as shown in Figure 1

[0079] (1) The impurity removal liquid 200 g is obtained according to the impurity removal method of the fluoroammonium salt solution of Example 1;

[0080] (2) Ammonia gas is introduced into the impurity removal liquid prepared in step (1) to perform an ammoniation reaction, the temperature of the ammoniation reaction is 40℃, the time is 2h, then the system after the ammoniation reaction is filtered, and the solid obtained by the filtration is white carbon black; the molar ratio of NH3 in the ammonia gas to the molar amount of fluosilicic acid in the impurity removal liquid prepared in step (1) is 6:1;

[0081] (3) The liquid obtained by the filtration in step (2) is heated to 150℃ to perform evaporation and concentration to a concentrated liquid, the mass fraction of the fluoroammonium salt in the concentrated liquid is 40%, then the concentrated liquid is reduced to room temperature, ammonium fluoride is crystallized and precipitated, then filtration is performed, and the solid obtained by the filtration is vacuum dried at 60℃ for 3h to obtain ammonium fluoride.

[0082] The purity of the ammonium fluoride prepared in the present example is 98.3%, the mass fractions of sulfate, phosphate and lead ions in the ammonium fluoride are 0.003%, 0.002% and 2ppm respectively; the purity of the white carbon black prepared in the present example is 92.6%, the mass fractions of sulfate, phosphate and lead ions in the white carbon black are 0.01%, 0.01% and 2ppm respectively. Therefore, the impurity content in the ammonium fluoride and the white carbon black prepared in the present example is low, which meets the requirements of the national standard.

[0083] Example 7

[0084] The preparation method of the fluoroammonium salt of the present example specifically includes the following steps:

[0085] (1) The impurity removal liquid is obtained according to the impurity removal method of the fluoroammonium salt solution of Example 1;

[0086] (2) Ammonia gas is introduced into the impurity removal liquid prepared in step (1) to perform an ammoniation reaction, the temperature of the ammoniation reaction is 70℃, the time is 0.5h, then the system after the ammoniation reaction is filtered, and the solid obtained by the filtration is white carbon black; the molar ratio of NH3 in the ammonia gas to the molar amount of fluosilicic acid in the impurity removal liquid prepared in step (1) is 8:1;

[0087] ​(3) The liquid obtained by filtration in step (2) is heated to 180°C for evaporation and concentration to a concentrated liquid with a mass fraction of 70% of ammonium fluoride salt, and then the concentrated liquid is cooled to room temperature, ammonium fluoride is crystallized and precipitated, then filtration is carried out, and the solid obtained by filtration is vacuum dried at 60°C for 3h to obtain ammonium fluoride.

[0088] The purity of ammonium bifluoride prepared in this example is 99.1%, and the mass fractions of sulfate, phosphate and lead ions in ammonium bifluoride are 0.006%, 0.005% and 4ppm, respectively. The purity of white carbon black prepared in this example is 92.9%, and the mass fractions of sulfate, phosphate and lead ions in white carbon black are 0.02%, 0.02% and 3ppm, respectively. Therefore, the impurity content in ammonium fluoride and white carbon black prepared in this example is low, which meets the requirements of national standards.

[0089] Experimental Example

[0090] In order to evaluate the impurity removal effect of the impurity removal methods of Examples 1-4 and Comparative Examples 1-3, the mass fractions of sulfate, phosphate and lead ions in the impurity removal liquids obtained from Examples 1-4 and Comparative Examples 1-3 were detected, and the test results are shown in Table 1.

[0091] Table 1 Mass fractions of sulfate, phosphate and lead ions in the impurity removal liquids obtained from Examples 1-2 and Comparative Examples 1-3

[0092] raffinate sulfate (wt%) phosphate (wt%) lead ions (ppm) Example 1 0.002 0.001 6 Example 2 0.002 0.003 5 Example 3 0.003 0.003 4 Example 4 0.001 0.001 2 Example 5 0.001 0.001 7 Comparative Example 1 0.002 0.060 6 Comparative Example 2 0.002 0.024 8 Comparative Example 3 0.040 0.090 23

Claims

1. A method for removing impurities from a solution of a fluoroammonium salt, characterized by, The method comprises the following steps: (1) mixing a fluorine ammonium salt solution and a fluosilicic acid solution to obtain a mixed solution with a pH of 2-3; the fluorine ammonium salt is ammonium fluoride and / or ammonium bifluoride; the mixed solution contains phosphate ions and sulfate ions; (2) mixing the mixed solution and a lead compound to perform a mixing reaction, and then removing lead ions in the system after the mixing reaction by using a lead adsorbent to obtain a decontaminated solution; the lead compound is one or any combination of lead oxide, lead hydroxide and lead fluosilicate; the amount of substance of lead in the lead compound is a, the amount of substance of phosphate ions in the mixed solution is b, and the amount of substance of sulfate ions in the mixed solution is c, so that a = x * b + y * c, x = 1.50-1.56, and y = 1.00-1.

04.

2. The method for removing impurities from a fluoroammonium salt solution according to claim 1, wherein The mass fraction of the fluosilicic acid solution is 5%-20%.

3. The method of removing impurities from a fluoroammonium salt solution according to claim 1, wherein The lead oxide is selected from one or any combination of PbO, Pb2O3 and Pb3O4.

4. The method for removing impurities from a fluoroammonium salt solution according to claim 1, wherein The temperature of the mixing reaction is 20-50 DEG C.

5. The method for removing impurities from a fluoroammonium salt solution according to claim 4, wherein The temperature of the mixing reaction is 40-50 DEG C, and the time is 0.5-2 h.

6. The method of impurity removal of a fluoroammonium salt solution according to claim 1, wherein When the mixed solution and the lead compound are mixed to perform the mixing reaction, the pH of the system of the mixing reaction is controlled to be not more than 3.

7. The method of removing impurities from a solution of a fluoroammonium salt according to claim 1, wherein The lead adsorbent is activated carbon; and the mass ratio of the lead adsorbent to the lead compound is (3-4):

10.

8. The method of impurity removal of a fluoroammonium salt solution according to claim 1, wherein The method for removing lead ions in the system after the mixing reaction by using the lead adsorbent comprises the following steps: mixing the lead adsorbent and the system after the mixing reaction, and then performing solid-liquid separation to obtain the decontaminated solution.

9. A process for the preparation of a fluoroammonium salt, characterized in that, The method comprises the following steps: The decontaminated solution obtained by the decontamination method of the fluorine ammonium salt solution in any one of claims 1-8 is subjected to an ammoniation reaction, then solid-liquid separation is performed, and then the liquid obtained by the solid-liquid separation is subjected to crystallization to obtain a fluorine ammonium salt.

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