Method for refining ammonium sulfate and application

Abstract

The invention provides an ammonium sulfate refining method and application, the method comprises the following steps: providing a crude ammonium sulfate aqueous solution, the crude ammonium sulfate aqueous solution comprises NH4 < + >, SO4 < 2->, Fe < 2 + >, C2O4 < 2-> and Mn < 2 + >; adjusting the crude ammonium sulfate aqueous solution to be alkaline, so that Fe < 2 + > is converted into ferric hydroxide precipitate; adding calcium hydroxide into the crude ammonium sulfate aqueous solution to convert C2O4 < 2-> into calcium oxalate precipitate; adding soluble phosphate into the crude ammonium sulfate aqueous solution to convert Mn < 2 + > into phosphate precipitate of manganese; and filtering the crude ammonium sulfate aqueous solution containing the ferric hydroxide precipitate, the calcium oxalate precipitate and the manganese phosphate precipitate, and evaporating and crystallizing the filtrate to obtain ammonium sulfate. According to the method, Fe < 2 + >, C2O4 < 2-> and Mn < 2 + > in the crude ammonium sulfate aqueous solution are respectively precipitated and removed by using different precipitants, so that the contents of Fe < 2 + >, C2O4 < 2-> and Mn < 2 + > in the crude ammonium sulfate aqueous solution can be effectively reduced, the purity of ammonium sulfate is improved, and the method is suitable for industrial production and application.

Description

Technical Field

[0001] The present application relates to the technical field of ammonium sulfate production, and in particular to a method and application of refined ammonium sulfate. Background Art

[0002] Lithium iron manganese phosphate (LiMnFePO4) has a higher energy density than lithium iron phosphate (LFP), which can increase the voltage platform of the cathode material while maintaining the stability of LFP. Ferromanganese oxalate is a manganese iron salt precursor commonly used in the preparation of LiMnFePO4. The waste liquid from industrial preparation of ferromanganese oxalate contains high levels of sulfate and ammonium ions. However, due to the high impurity content, the ammonium sulfate obtained by directly drying the waste liquid is of low purity and has limited application value. Therefore, a method for refining ammonium sulfate is needed. Summary of the Invention

[0003] The present application provides a method and application of refined ammonium sulfate. The method can effectively reduce the Fe content in crude ammonium sulfate aqueous solution by using chemical precipitation. 2+ 、C2O4 2- and Mn 2+ .

[0004] In a first aspect, the present application provides a method for refining ammonium sulfate, comprising:

[0005] Providing a crude ammonium sulfate aqueous solution, the crude ammonium sulfate aqueous solution comprising NH4 + 、SO4 2- 、Fe 2+ 、C2O4 2- and Mn 2+ ;

[0006] Adjust the crude ammonium sulfate aqueous solution to be alkaline to make Fe 2+ Converted into iron hydroxide precipitate;

[0007] Calcium hydroxide is added to the crude ammonium sulfate aqueous solution to make C2O4 2- Converted into calcium oxalate precipitate;

[0008] Soluble phosphate is added to the crude ammonium sulfate aqueous solution to make Mn 2+ Phosphate precipitation converted to manganese;

[0009] The crude ammonium sulfate aqueous solution containing the iron hydroxide precipitate, calcium oxalate precipitate and manganese phosphate precipitate is filtered, and the filtrate is evaporated and crystallized to obtain ammonium sulfate.

[0010] According to the present application, different precipitants are used to precipitate Fe 2+ 、C2O4 2- and Mn 2 +The precipitation of the three ions does not interfere with each other and can be carried out in the same reaction system. The precipitates can be filtered and removed at the same time. This method is simple and can effectively reduce the Fe content of crude ammonium sulfate aqueous solution. 2+ 、C2O4 2- and Mn 2+ content, improve the purity of ammonium sulfate, and is suitable for industrial production applications.

[0011] In some embodiments, the method specifically comprises:

[0012] Providing a crude ammonium sulfate aqueous solution, the crude ammonium sulfate aqueous solution comprising NH4 + 、SO4 2- 、Fe 2+ 、C2O4 2- and Mn 2+ ;

[0013] Adjust the crude ammonium sulfate aqueous solution to be alkaline to make Fe 2+ Converting into iron hydroxide precipitate to obtain a first suspension;

[0014] Calcium hydroxide is added to the first suspension to make C2O4 2- Converting into calcium oxalate precipitate to obtain a second suspension;

[0015] Soluble phosphate is added to the second suspension to make Mn 2+ converting it into a manganese phosphate precipitate to obtain the crude ammonium sulfate aqueous solution containing the iron hydroxide precipitate, the calcium oxalate precipitate and the manganese phosphate precipitate;

[0016] The crude ammonium sulfate aqueous solution containing the iron hydroxide precipitate, calcium oxalate precipitate and manganese phosphate precipitate is filtered, and the filtrate is evaporated and crystallized to obtain ammonium sulfate.

[0017] In some embodiments, the crude ammonium sulfate aqueous solution is adjusted to be alkaline to make Fe 2+ The conversion into ferric hydroxide precipitate specifically includes: using ammonia water to adjust the crude ammonium sulfate aqueous solution to pH = 8-10, so that Fe 2+ Converted into iron hydroxide precipitate.

[0018] In some embodiments, the calcium hydroxide and the C2O4 in the crude ammonium sulfate aqueous solution 2- The molar ratio is 0.8 to 10:1, and can be optionally 0.9 to 1.1:1.

[0019] In some embodiments, the soluble phosphate and the Mn in the crude ammonium sulfate aqueous solution 2+ The molar ratio is 1 to 2:1, and can be optionally 1 to 1.05:1.

[0020] In some embodiments, the soluble phosphate includes at least one of ammonium phosphate, ammonium hydrogen phosphate, and ammonium dihydrogen phosphate; optionally, the soluble phosphate includes ammonium phosphate and / or ammonium hydrogen phosphate.

[0021] In some embodiments, the evaporation and crystallization of the filtrate to obtain ammonium sulfate includes: adjusting the filtrate to pH = 2-6 with sulfuric acid, converting NH3·H2O into NH4 + , and then evaporate and crystallize to obtain ammonium sulfate.

[0022] In some embodiments, the crude ammonium sulfate aqueous solution is derived from the waste liquid generated after the preparation of ferromanganese oxalate, wherein the iron content in the waste liquid is ≥1000ppm, the manganese content is ≥500ppm, and the C2O4 2- Content ≥10000ppm.

[0023] In a second aspect, the present application provides an ammonium nitrogen fertilizer, comprising: ammonium sulfate prepared according to the method described in any embodiment of the first aspect, wherein the nitrogen content of the ammonium nitrogen fertilizer is ≥19.6%, and can optionally be ≥20.5%.

[0024] In some embodiments, the ammonium nitrogen fertilizer contains 10ppm to 50ppm of iron, 5ppm to 20ppm of manganese, and C2O4 2- The content is 100ppm~500ppm. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0026] Figure 1 This is a process flow chart of an embodiment of the present application. DETAILED DESCRIPTION

[0027] The various embodiments or implementation schemes in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments.

[0028] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with an embodiment or example is included in at least one embodiment or example of the present application. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0029] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0030] As described in the background technology, in the waste liquid currently produced by manganese ferrooxalate, the waste liquid can generally be treated directly by drying and crystallizing to recover ammonium sulfate. Since the waste liquid contains a large amount of oxalate, ferrous ions and manganese ions, the purity of the ammonium sulfate obtained by this method is low, and it is difficult to directly apply it to related products, and its application value is low.

[0031] Therefore, to improve its application value, the purity of ammonium sulfate can be increased by reducing the content of oxalate, ferrous ions, and manganese ions in the wastewater. This can reduce its application value in products such as ammoniacal nitrogen fertilizer, improve its application value, and reduce wastewater treatment costs. Related technologies can remove impurity ions by passing the wastewater through an ion permeation membrane, but this method is costly and has low treatment efficiency, making it unsuitable for industrial production applications.

[0032] Based on this, the present application provides a method and application of refined ammonium sulfate, which mainly uses a chemical precipitation method to add different precipitants to the crude ammonium sulfate aqueous solution to separate Fe 2+ 、C2O4 2- and Mn 2+ The ammonium sulfate is converted into a precipitate and removed, thereby effectively reducing the content of impurities in the ammonium sulfate, improving its purity, and effectively improving its application value. The specific implementation methods of this application are described in detail below.

[0033] A method for refining ammonium sulfate

[0034] In a first aspect, the present application provides a method for refining ammonium sulfate, comprising:

[0035] Providing a crude ammonium sulfate aqueous solution, the crude ammonium sulfate aqueous solution includes NH4 + 、SO4 2- 、Fe 2+ 、C2O4 2- and Mn 2+ ;

[0036] Adjust the crude ammonium sulfate aqueous solution to alkaline, so that Fe 2+ Converted into iron hydroxide precipitate;

[0037] Add calcium hydroxide to the crude ammonium sulfate aqueous solution to make C2O4 2-Converted into calcium oxalate precipitate;

[0038] Add soluble phosphate to the crude ammonium sulfate aqueous solution to make Mn 2+ Phosphate precipitation converted to manganese;

[0039] The crude ammonium sulfate aqueous solution containing ferric hydroxide precipitate, calcium oxalate precipitate and manganese phosphate precipitate is filtered, and the filtrate is evaporated and crystallized to obtain ammonium sulfate.

[0040] According to the present application, different precipitants are used to precipitate Fe 2+ 、C2O4 2- and Mn 2 + The precipitation of the three ions does not interfere with each other and can be carried out in the same reaction system. The precipitates can be filtered and removed at the same time. This method is simple and can effectively reduce the Fe content of crude ammonium sulfate aqueous solution. 2+ 、C2O4 2- and Mn 2+ content, improve the purity of ammonium sulfate, and is suitable for industrial production applications.

[0041] Specifically, this method is mainly used to remove Fe 2+ 、C2O4 2- and Mn 2+ Among them, ferrous ions are obtained by adjusting the crude ammonium sulfate aqueous solution to alkalinity, and the ferrous ions in the solution will be oxidized and converted into ferric hydroxide precipitates. The solubility product constant of ferric hydroxide is small, and the content of iron in the solution can be effectively reduced under alkaline conditions; oxalate ions are obtained by adding calcium hydroxide to the crude ammonium sulfate aqueous solution, and the calcium ions react with oxalate ions to form calcium oxalate precipitates. The solubility product constant of calcium oxalate is small, which can effectively reduce the content of oxalate in the solution. At the same time, the solubility of calcium hydroxide itself is small, and excess calcium hydroxide will also be removed during the filtration step, and no excessive impurity calcium ions will be introduced into the solution; manganese ions are obtained by adding soluble phosphates. Under the action of phosphates, the manganese ions will be converted into insoluble manganese phosphate or manganese hydrogen phosphate precipitates, thereby effectively reducing the content of manganese ions in the solution.

[0042] It should also be noted that the order of precipitating the three ions in this method is not further limited and can be adjusted according to actual needs. According to the above precipitation principle, the precipitation methods of the three ions do not interfere with each other, so there is no need to remove them by precipitation and filtration in steps, and they can be removed after precipitation in the same reaction system.

[0043] It can also be understood that, in the context of the present application, soluble phosphate refers to a soluble salt that can ionize phosphate ions in an aqueous solution, including but not limited to soluble orthophosphate, soluble hydrogen phosphate, and soluble dihydrogen phosphate; in addition, the addition of calcium hydroxide can be the direct addition of calcium hydroxide or the addition of calcium oxide. After calcium oxide is added to the aqueous solution, it will react with water to form calcium hydroxide, which also falls within the scope of protection of the present application.

[0044] In some embodiments, the method specifically comprises:

[0045] Providing a crude ammonium sulfate aqueous solution, the crude ammonium sulfate aqueous solution includes NH4 + 、SO4 2- 、Fe 2+ 、C2O4 2- and Mn 2+ ;

[0046] Adjust the crude ammonium sulfate aqueous solution to alkaline, so that Fe 2+ Converting into iron hydroxide precipitate to obtain a first suspension;

[0047] Calcium hydroxide is added to the first suspension to make C2O4 2- Converting into calcium oxalate precipitate to obtain a second suspension;

[0048] Add soluble phosphate to the second suspension to make Mn 2+ converting into a manganese phosphate precipitate to obtain a crude ammonium sulfate aqueous solution containing an iron hydroxide precipitate, a calcium oxalate precipitate and a manganese phosphate precipitate;

[0049] The crude ammonium sulfate aqueous solution containing ferric hydroxide precipitate, calcium oxalate precipitate and manganese phosphate precipitate is filtered, and the filtrate is evaporated and crystallized to obtain ammonium sulfate.

[0050] In the above embodiment, the flow chart is as follows: Figure 1 As shown, the order of precipitation of the three impurity ions is further limited, which can further reduce the Fe 2+ 、C2O4 2- and Mn 2+ Specifically, the ferrous ions in the solution are first precipitated by adjusting the pH, then calcium hydroxide is added to precipitate the oxalate ions, and finally, soluble phosphate is used to precipitate the manganese ions; wherein, Fe 2+ 、C2O4 2- and Mn 2+The pH of the aqueous solution is acidic, and the effect of directly using calcium hydroxide to precipitate oxalate under acidic conditions is weaker than that under alkaline conditions. Therefore, after adjusting the pH to alkaline, the oxalate ions are precipitated, which can further reduce the content of oxalate in the solution. On the other hand, the solubility of calcium hydroxide is lower under alkaline conditions, so the introduction of calcium ions can be further reduced, thereby further improving the purity of ammonium sulfate. At the same time, since oxalate ions have a certain chelating effect on manganese ions in the solution, they will affect the precipitation of manganese ions in the solution. Therefore, after precipitating oxalate ions, soluble phosphates are used to precipitate manganese ions. This can reduce the effect of oxalate on the precipitated manganese ions, thereby further reducing the content of manganese ions in the solution. Therefore, by adjusting the precipitation order of the above-mentioned impurity ions, the purity of ammonium sulfate can be further improved, and its application value can be further improved.

[0051] In some embodiments, the crude ammonium sulfate aqueous solution is adjusted to be alkaline to make Fe 2+ The conversion into ferric hydroxide precipitate specifically includes: using ammonia water to adjust the crude ammonium sulfate aqueous solution to pH = 8-10, so that Fe 2+ Converted into iron hydroxide precipitate.

[0052] In some of the above embodiments, ammonia water is used to adjust the crude ammonium sulfate aqueous solution to pH = 8-10. Using ammonia water as a pH regulator can avoid the introduction of new impurity cations. In addition, when the pH is 8-10, Fe 2+ The ammonium sulfate is fully converted into ferric hydroxide precipitate. Under these conditions, oxalate ions and manganese ions react more easily with the corresponding precipitant, further reducing the content of impurity ions, thereby further improving the purity of ammonium sulfate. For example, the pH value can be 8, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10, or any range thereof.

[0053] In some embodiments, calcium hydroxide and C2O4 in crude ammonium sulfate aqueous solution 2- The molar ratio is 0.8 to 10:1.

[0054] In some of the above embodiments, a proper excess of calcium hydroxide is more conducive to the sufficient precipitation of oxalate. At the same time, due to the low solubility of calcium hydroxide, a proper excess will not introduce too much calcium ions, thus being more conducive to improving the purity of ammonium sulfate and reducing the refining cost. 2-The molar ratio of 1:1 to 2:1 can be 0.8:1, 0.9:1, 1:1, 1.05:1, 1.1:1, 1.2:1, 1.3:1, 1.5:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, or any range thereof, more preferably 0.9 to 1.1:1.

[0055] In some embodiments, the soluble phosphate and the Mn in the crude ammonium sulfate aqueous solution are 2+ The molar ratio is 1 to 2:1.

[0056] In some of the above embodiments, the soluble phosphate will ionize and hydrolyze in the aqueous solution, and its reaction with the manganese ion mainly generates manganese phosphate and manganese hydrogen phosphate precipitates with smaller solubility product constants. At the same time, under alkaline conditions, the above precipitation reaction is more likely to occur. In the aqueous solution of soluble phosphate and crude ammonium sulfate, Mn 2+ When the molar ratio of phosphate to manganese is 1 to 2:1, the manganese ions can be fully converted into manganese phosphate precipitation, and the influence of excessive soluble phosphate on the purity of ammonium sulfate can be reduced, thereby further improving the purity of ammonium sulfate. 2+ The molar ratio of 1:1, 1.05:1, 1.1:1, 1.15:1, 1.2:1, 1.25:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, or any range thereof, more preferably 1 to 1.05:1.

[0057] In some embodiments, the soluble phosphate includes at least one of ammonium phosphate, ammonium hydrogen phosphate, and ammonium dihydrogen phosphate. These compounds are commonly used soluble ammonium phosphate salts. The use of ammonium salts can avoid the introduction of new impurity cations. Moreover, these compounds have good solubility and can be fully ionized and hydrolyzed in aqueous solution, allowing the precipitation reaction to proceed fully.

[0058] Furthermore, the soluble phosphate includes ammonium phosphate and / or ammonium hydrogen phosphate. The corresponding aqueous solutions of ammonium phosphate and ammonium hydrogen phosphate are alkaline. Since manganese ions react with soluble phosphates to achieve better precipitation under alkaline conditions, the use of ammonium phosphate and / or ammonium hydrogen phosphate can reduce the pH drop of the system during the treatment process, thereby further reducing the content of impurity ions in the system and improving the purity of ammonium sulfate.

[0059] In some embodiments, evaporating and crystallizing the filtrate to obtain ammonium sulfate comprises: adjusting the filtrate to pH=2-6 using sulfuric acid to convert NH3·H2O into NH4 + , and then evaporate and crystallize to obtain ammonium sulfate.

[0060] In some of the above embodiments, the pH of the filtrate is adjusted to 2-6 using ammonium sulfate, which can fully fix the ammonium ions in the filtrate and reduce the volatilization of ammonium ions in the form of ammonia gas during the evaporation and crystallization process, thereby further improving the recovery rate of ammonium sulfate. At the same time, using sulfuric acid as a pH regulator can also avoid the introduction of new impurity anions and improve the purity of ammonium sulfate.

[0061] In some embodiments, the crude ammonium sulfate aqueous solution is derived from the waste liquid generated after the preparation of ferromanganese oxalate, wherein the iron content in the waste liquid is ≥1000ppm, the manganese content is ≥500ppm, and the C2O4 2- Content ≥10000ppm.

[0062] In some of the above embodiments, the method for refining ammonium sulfate can be used to treat the waste liquid generated after the preparation of manganese ferrooxalate, and thus can be applied to the field of lithium batteries. The waste liquid generated after the preparation of manganese ferrooxalate is used as a raw material. After treatment by the above method, the content of oxalate, iron and manganese elements therein can be effectively reduced, and the ammonium sulfate therein can be recycled and utilized. On the one hand, the cost of sewage treatment can be reduced, and on the other hand, environmental pollution can be reduced.

[0063] In some embodiments, each precipitation reaction can be carried out at 30-60° C. with stirring. Properly increasing the temperature can increase the rate of the precipitation reaction, while stirring can also promote the precipitation reaction to proceed fully, thereby improving the purification efficiency and further increasing the purity of ammonium sulfate.

[0064] In some embodiments, during each precipitation reaction, the precipitant used, such as calcium hydroxide or soluble phosphate, has a purity of not less than 95%. A high-purity precipitant can further reduce the introduction of impurities, thereby improving the purity of ammonium sulfate.

[0065] In a second aspect, the present application provides an ammonium nitrogen fertilizer, comprising: ammonium sulfate prepared according to the method of any embodiment of the first aspect, wherein the nitrogen content of the ammonium nitrogen fertilizer is ≥19.6%.

[0066] According to the present application, the ammonium sulfate prepared by the method of any embodiment of the first aspect has a high purity, so it can be directly used as an ammonia nitrogen fertilizer. Its nitrogen content can be above 19.6%, preferably above 20.5%, and has a high application value.

[0067] In some embodiments, the ammonium nitrogen fertilizer has an iron content of 10ppm to 50ppm, a manganese content of 5ppm to 20ppm, and a C2O4 2- The content is 100ppm~500ppm.

[0068] In some of the above embodiments, the contents of carbon, manganese and oxalate in the ammonia nitrogen fertilizer can be controlled within the above ranges, which causes less pollution to the environment and can supplement crops with appropriate trace elements. Therefore, the ammonia nitrogen fertilizer can be directly applied to crops.

[0069] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0070] Determination of manganese and iron content

[0071] Weigh 0.2 g of each sample into a 100 mL beaker, add 10 mL of 10% nitric acid solution, and digest at 120°C for 0.5 h. Draw up to volume in a 100 mL volumetric flask. Then, pipette 1 mL into a 100 mL volumetric flask and bring to volume to obtain the test solution. Determine the manganese and iron contents of the samples using an inductively coupled plasma optical emission spectrometer (ICP-OES, Agilent 5800).

[0072] Determination of oxalate content

[0073] Weigh approximately 0.5 g of sample into a 100 mL conical flask, add 20 mL of sulfuric and phosphoric acid mixture to dissolve, heat to approximately 60°C, and add dropwise a 0.02 mol / L potassium permanganate solution (calibrated with sodium oxalate of known purity) until the solution turns light purple and does not fade for 30 seconds, which is the endpoint. Record the titration volume; perform 3-4 sets of parallel experiments.

[0074] Calculate the oxalate content (mass fraction ω) in the sample according to the following formula:

[0075] ω=(88·2.5·c2·V3) / (1000·m1)

[0076] c2—concentration of potassium permanganate standard solution, in mol / L

[0077] V3—the volume of potassium permanganate standard solution consumed by the titration sample, in mL;

[0078] m1—The mass of the sample weighed, in g.

[0079] Nitrogen content determination

[0080] Accurately weigh 1.6-1.8g of sample into a beaker, dissolve it in an appropriate amount of distilled water, and quantitatively transfer it to a 250mL volumetric flask. Finally, dilute to the mark with distilled water and shake well. Use a pipette to transfer 25mL of the test solution into an Erlenmeyer flask. Add 1-2 drops of methyl red indicator. The solution will turn red. Neutralize it with 0.1mol / L NaOH standard solution until the red turns golden yellow. Then add 8mL of neutralized 1:1 formaldehyde solution and 1-2 drops of phenolphthalein indicator, shake well. After standing for one minute, titrate with 0.1mol / L NaOH standard solution until the solution turns light red for half a minute. This is the endpoint. Record the reading and repeat 2-3 times. Calculate the nitrogen content in the sample based on the concentration of the NaOH standard solution and the volume consumed in the titration.

[0081] Example 1

[0082] A method for refining ammonium sulfate comprises the following steps:

[0083] Take 1000g of oxalic acid manganese iron waste liquid, in which the content of iron element is 1439.27ppm, the content of manganese element is 792.82ppm, C2O4 2- The content of 11090.83ppm was added to the reactor, heated to 50℃ and kept warm, with a stirring speed of 500r / min, and then ammonia water with a concentration of 5mol / L was added, the pH was adjusted to 9.0, and stirring was continued for 10min;

[0084] Then add 8.2 g of 95% pure calcium hydroxide powder to the reactor and continue stirring for 10 min;

[0085] Then, 5.0 g of 99% pure diammonium hydrogen phosphate powder was added to the reactor and stirred for 20 min.

[0086] The suspension in the reaction kettle was discharged, cooled to room temperature, and the filtrate was obtained by vacuum filtration to obtain an ammonium sulfate solution;

[0087] A sulfuric acid solution with a concentration of 4 mol / L was added to the ammonium sulfate solution to reduce the pH value of the solution to 4, and then evaporated and crystallized to obtain ammonium sulfate solid.

[0088] Example 2

[0089] A method for refining ammonium sulfate comprises the following steps:

[0090] Take 1000g of oxalic acid manganese iron waste liquid, in which the content of iron element is 1439.27ppm, the content of manganese element is 792.82ppm, C2O4 2-The content of 11090.83ppm was added to the reactor, heated to 50℃ and kept warm, with a stirring speed of 500r / min, and then ammonia water with a concentration of 5mol / L was added, the pH was adjusted to 9.0, and stirring was continued for 10min;

[0091] Then add 5.0 g of 99% pure diammonium hydrogen phosphate powder to the reactor and continue stirring for 10 min;

[0092] Then add 8.2 g of 95% pure calcium hydroxide powder to the reactor and continue stirring for 20 min;

[0093] The suspension in the reaction kettle was discharged, cooled to room temperature, and the filtrate was obtained by vacuum filtration to obtain an ammonium sulfate solution;

[0094] A sulfuric acid solution with a concentration of 4 mol / L was added to the ammonium sulfate solution to reduce the pH value of the solution to 4, and then evaporated and crystallized to obtain ammonium sulfate solid.

[0095] Example 3

[0096] Take 1000g of oxalic acid manganese iron waste liquid, in which the content of iron element is 1439.27ppm, the content of manganese element is 792.82ppm, C2O4 2- The content was 11090.83ppm; the mixture was added to a reactor and heated to 50°C and kept warm, with a stirring speed of 500r / min, and then 5.0g of 99% pure diammonium hydrogen phosphate powder was added and stirred for 10min;

[0097] Then add 8.2 g of 95% pure calcium hydroxide powder to the reactor and continue stirring for 10 min;

[0098] Then, add 5 mol / L ammonia water to the reactor to adjust the pH to 9.0 and continue stirring for 20 min;

[0099] The suspension in the reaction kettle was discharged, cooled to room temperature, and the filtrate was obtained by vacuum filtration to obtain an ammonium sulfate solution;

[0100] A sulfuric acid solution with a concentration of 4 mol / L was added to the ammonium sulfate solution to reduce the pH value of the solution to 4, and then evaporated and crystallized to obtain ammonium sulfate solid.

[0101] Example 4

[0102] Take 1000g of oxalic acid manganese iron waste liquid, in which the content of iron element is 1439.27ppm, the content of manganese element is 792.82ppm, C2O4 2-The content was 11090.83ppm; the mixture was added to a reactor and heated to 50°C and kept warm, with a stirring speed of 500r / min, and then 5.0g of 99% pure diammonium hydrogen phosphate powder was added and stirred for 10min;

[0103] Then, 5 mol / L ammonia water was added to the reactor to adjust the pH to 9.0 and the mixture was stirred for 10 min.

[0104] Then add 8.2 g of 95% pure calcium hydroxide powder to the reactor and continue stirring for 20 min;

[0105] The suspension in the reaction kettle was discharged, cooled to room temperature, and the filtrate was obtained by vacuum filtration to obtain an ammonium sulfate solution;

[0106] A sulfuric acid solution with a concentration of 4 mol / L was added to the ammonium sulfate solution to reduce the pH value of the solution to 4, and then evaporated and crystallized to obtain ammonium sulfate solid.

[0107] Comparative Example 1

[0108] A method for preparing ammonium sulfate comprises the following steps:

[0109] Take 1000 g of the same ferromanganese oxalate waste liquid as in Example 1, adjust the pH of the waste liquid to 4 with a 4 mol / L sulfuric acid solution, and then perform evaporation and crystallization to obtain ammonium sulfate solid.

[0110] Test section

[0111] The ammonium sulfate solids obtained in the examples and comparative examples were tested for the contents of manganese, iron, oxalate and nitrogen. The results are shown in Table 1.

[0112] Table 1

[0113]

[0114]

[0115] According to Table 1, the contents of manganese, iron and oxalate in the obtained ammonium sulfate in each embodiment are significantly reduced compared with Comparative Example 1. The method for refining ammonium sulfate provided by the present application is used to treat manganese ferrooxalate waste liquid to prepare ammonium sulfate, which can effectively reduce the contents of manganese, iron and oxalate in ammonium sulfate and increase the nitrogen content of ammonium sulfate.

[0116] Further comparison of Examples 1 to 4 shows that the order of settling the impurities has a great influence on the effect of impurity removal. In Example 1, the order of settling the iron element first, then the oxalate ion, and then the manganese element can cooperate with each other to further reduce the content of manganese, iron and oxalate in ammonium sulfate and increase the nitrogen content of ammonium sulfate.

[0117] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for refining ammonium sulfate, characterized in that: include: Providing a crude ammonium sulfate aqueous solution, the crude ammonium sulfate aqueous solution comprising NH4 + 、SO4 2- 、Fe 2+ 、C2O4 2- and Mn 2+ ; Adjust the crude ammonium sulfate aqueous solution to be alkaline to make Fe 2+ Converted into iron hydroxide precipitate; Calcium hydroxide is added to the crude ammonium sulfate aqueous solution to make C2O4 2- Converted into calcium oxalate precipitate; Soluble phosphate is added to the crude ammonium sulfate aqueous solution to make Mn 2+ Phosphate precipitation converted to manganese; The crude ammonium sulfate aqueous solution containing the iron hydroxide precipitate, calcium oxalate precipitate and manganese phosphate precipitate is filtered, and the filtrate is evaporated and crystallized to obtain ammonium sulfate.

2. The method according to claim 1, characterized in that Specifically include: Providing a crude ammonium sulfate aqueous solution, the crude ammonium sulfate aqueous solution comprising NH4 + 、SO4 2- 、Fe 2+ 、C2O4 2- and Mn 2+ ; Adjust the crude ammonium sulfate aqueous solution to be alkaline to make Fe 2+ Converting into iron hydroxide precipitate to obtain a first suspension; Calcium hydroxide is added to the first suspension to make C2O4 2- Converting into calcium oxalate precipitate to obtain a second suspension; Soluble phosphate is added to the second suspension to make Mn 2+ converting it into a manganese phosphate precipitate to obtain the crude ammonium sulfate aqueous solution containing the iron hydroxide precipitate, the calcium oxalate precipitate and the manganese phosphate precipitate; The crude ammonium sulfate aqueous solution containing the iron hydroxide precipitate, calcium oxalate precipitate and manganese phosphate precipitate is filtered, and the filtrate is evaporated and crystallized to obtain ammonium sulfate.

3. The method according to claim 1 or 2, characterized in that The crude ammonium sulfate aqueous solution is adjusted to be alkaline, so that Fe 2+ The conversion into ferric hydroxide precipitate specifically includes: Ammonia water was used to adjust the pH of the crude ammonium sulfate aqueous solution to 8-10. 2+ Converted into iron hydroxide precipitate.

4. The method according to claim 1 or 2, characterized in that The calcium hydroxide and the C2O4 in the crude ammonium sulfate aqueous solution 2- The molar ratio is 0.8 to 10:1, and can be optionally 0.9 to 1.1:

1.

5. The method according to claim 1 or 2, characterized in that The soluble phosphate and the Mn in the crude ammonium sulfate aqueous solution 2+ The molar ratio is 1 to 2:1, and can be optionally 1 to 1.05:

1.

6. The method according to claim 1 or 2, characterized in that The soluble phosphate includes at least one of ammonium phosphate, ammonium hydrogen phosphate, and ammonium dihydrogen phosphate; Optionally, the soluble phosphate includes ammonium phosphate and / or ammonium hydrogen phosphate.

7. The method according to claim 1 or 2, characterized in that The filtrate is evaporated and crystallized to obtain ammonium sulfate, comprising: Use sulfuric acid to adjust the filtrate to pH = 2-6 to convert NH3·H2O into NH4 + , and then evaporate and crystallize to obtain ammonium sulfate.

8. The method according to claim 1 or 2, characterized in that The crude ammonium sulfate aqueous solution is derived from the waste liquid generated after the preparation of ferromanganese oxalate, wherein the iron content in the waste liquid is ≥1000ppm, the manganese content is ≥500ppm, and the C2O4 2- Content ≥10000ppm.

9. An ammonium nitrogen fertilizer, characterized in that include: According to any one of claims 1 to 8, the ammonium sulfate prepared by the method has a nitrogen content of ≥19.6%, and can optionally have a nitrogen content of ≥20.5%.

10. The ammonium nitrogen fertilizer according to claim 9, characterized in that The ammonium nitrogen fertilizer contains 10ppm to 50ppm of iron, 5ppm to 20ppm of manganese, and C2O4 2- The content is 100ppm~500ppm.

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