WO2024093075A1

WO2024093075A1 - Method for extracting iron from ferro-nickel alloy and preparing hydrogen peroxide

Info

Publication number: WO2024093075A1
Application number: PCT/CN2023/079176
Authority: WO
Inventors: 李森; 李长东; 阮丁山; 陈若葵; 乔延超; 何芳
Original assignee: 广东邦普循环科技有限公司; 湖南邦普循环科技有限公司
Priority date: 2022-11-05
Filing date: 2023-03-02
Publication date: 2024-05-10
Also published as: CN115849307A

Abstract

Provided is a method for extracting iron from a ferro-nickel alloy and preparing hydrogen peroxide, comprising: S1, mixing a ferro-nickel alloy with an acid solution, and introducing inert gas to obtain a slurry; S2, heating the slurry for a reaction, filtering the slurry after the reaction, and taking a filtrate to obtain a ferro-nickel leachate; S3, adding a phosphorus source and an oxidizing agent into the ferro-nickel leachate for precipitation, and washing, drying and dehydrating a filter residue to obtain iron phosphate; S4, collecting tail gas generated in step S2, and carrying out a desulfurization and purification operation on the collected tail gas to obtain hydrogen; and S5, adding an organic solvent and a catalyst into the hydrogen for a hydrogenation-oxidation reaction to obtain a hydrogen peroxide product. The whole method for extracting the iron from the ferro-nickel alloy and preparing the hydrogen peroxide has a simple principle and a high comprehensive recovery rate, and meanwhile, it allows for a relatively high utilization rate of both iron and hydrogen peroxide prepared by hydrogen production.

Description

Method for extracting iron from nickel-iron alloy and preparing hydrogen peroxide

Technical Field

The present application relates to the technical field of positive electrode materials for lithium-ion batteries, and in particular to a method for extracting iron from a nickel-iron alloy and preparing hydrogen peroxide.

Background technique

With the rapid development of the new energy industry, the demand for positive electrode materials and precursors has exploded. Among them, ternary lithium batteries have quickly occupied a very important position in power batteries due to their high energy density and good cycle performance. Nickel, cobalt, and manganese, as indispensable key elements in the positive electrode materials of ternary lithium batteries, are also increasingly in short supply. But at the same time, the safety and cost issues of new energy vehicles are gradually attracting attention. Among them, the advantages of lithium iron phosphate positive electrode materials are obvious, such as long life, safe use, high temperature resistance, and green environmental protection. Therefore, the market demand for lithium iron phosphate is increasing, and the demand for iron phosphate as a precursor for the preparation of lithium iron phosphate is also increasing accordingly.

The related technology discloses a method for recovering iron from alloy leachate in the cobalt-nickel industry, wherein the method involves first purifying the alloy leachate to remove impurities in the solution to obtain a purified liquid; using the purified liquid, ammonium dihydrogen phosphate and hydrogen peroxide to obtain a filter residue and a filtrate under low temperature conditions; after washing and slurrying the filter residue, phosphoric acid is added and the temperature is raised to 90°C for conversion to obtain dihydrate iron phosphate, which is then calcined to prepare an anhydrous iron phosphate product.

However, although the above method recovers iron from the alloy, this method first uses ammonium dihydrogen phosphate to obtain a synthetic material, and then uses phosphoric acid to convert it into dihydrated iron phosphate. The entire method is cumbersome to operate, and the phosphorus-containing waste liquid is not further recycled, resulting in a waste of phosphorus sources.

Summary of the invention

The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

The purpose of the present application is to overcome the deficiencies in the prior art and to provide a method for extracting iron from a nickel-iron alloy and preparing hydrogen peroxide, which is simple to operate and can avoid waste of phosphorus sources.

The purpose of this application is achieved through the following technical solutions:

A method for extracting iron from a nickel-iron alloy and preparing hydrogen peroxide, comprising:

S1: mixing the nickel-iron alloy with acid solution and introducing an inert gas to obtain a slurry;

S2: heating the slurry to react, filtering the slurry after the reaction, and taking the filtrate to obtain a nickel-iron leaching solution;

S3: adding a phosphorus source and an oxidant to the nickel-iron leaching solution for precipitation, washing, drying and dehydrating the filter residue to obtain iron phosphate;

S4: collecting the tail gas generated in step S2, and performing desulfurization and purification operations on the collected tail gas to obtain hydrogen;

S5: adding an organic solvent and a catalyst to the hydrogen to carry out a hydrogenation-oxidation reaction to obtain a hydrogen peroxide product.

In one embodiment, in the nickel-iron alloy, the content of nickel element is 15% to 40%, and the content of iron element is 60% to 85%.

In one embodiment, the acid solution is at least one of sulfuric acid, hydrochloric acid or nitric acid.

In one embodiment, the inert gas is nitrogen or argon.

In one of the embodiments, the heating temperature of the slurry heating reaction is 50° C. to 90° C., and the heating time is 1 h to 20 h.

In one embodiment, the phosphorus source is at least one of phosphoric acid or phosphate;

The phosphate is at least one of trisodium phosphate, sodium dihydrogen phosphate, sodium monohydrogen phosphate, ammonium monohydrogen phosphate, ammonium dihydrogen phosphate or potassium phosphate.

In one embodiment, the temperature for adding the phosphorus source and the oxidant to the nickel-iron leaching solution for precipitation is 60° C. to 100° C., and the heating time is 3 h to 10 h.

In one embodiment, the washing is pulping washing, the liquid-to-solid ratio of the washing is 0.5 mL/g to 20 mL/g; and the washing time is 0.5 h to 5 h.

In one embodiment, the desulfurizing agent used to desulfurize the collected tail gas is complex iron;

Optionally, the adsorbent used for purification is at least one of alumina, silica gel, activated carbon, or carbon molecular sieve.

The present application also provides an application of the method for extracting iron from a nickel-iron alloy and preparing hydrogen peroxide as described in any of the above embodiments in preparing a positive electrode material.

Compared with the prior art, this application has at least the following advantages:

1. The method for extracting iron from nickel-iron alloy and preparing hydrogen peroxide of the present application comprises reacting the nickel-iron alloy with acid solution under an inert atmosphere, wherein the generated gas contains no oxygen and does not generate an explosion risk; then, a part of the nickel-iron leaching solution is oxidized by adding an oxidant, and then mixed with the generated gas for desulfurization and purification operations to obtain hydrogen;

2. The method of extracting iron and preparing hydrogen peroxide from nickel-iron alloy of the present application uses nickel-iron alloy as raw material, collects the tail gas generated by the heating reaction of the slurry during the leaching process, and performs desulfurization and purification operations to recover hydrogen and purify it, and then uses it to prepare hydrogen peroxide. At the same time, the prepared hydrogen peroxide product can also be reused as an oxidant to prepare iron phosphate;

3. The method for extracting iron from nickel-iron alloy and preparing hydrogen peroxide in the present application, the iron element in the nickel-iron alloy can be used to prepare iron phosphate, which can be further used as a precursor of lithium iron phosphate to prepare lithium iron phosphate positive electrode material. The principle of the method for extracting iron from nickel-iron alloy and preparing hydrogen peroxide is relatively simple and the comprehensive recovery rate is high. At the same time, the utilization rates of iron and hydrogen production for preparing hydrogen peroxide are both high, which has good industrial prospects and economic benefits, avoids the problem of phosphorus-containing waste liquid not being further recycled and avoids the waste of phosphorus sources.

Other aspects will be apparent upon reading and understanding the drawings and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

FIG1 is a flow chart of a method for extracting iron from nickel-iron alloy and preparing hydrogen peroxide according to an embodiment of the present invention;

Fig. 2 is a process diagram of the method for extracting iron and preparing hydrogen peroxide from the nickel-iron alloy shown in Fig. 1;

FIG3 is a SEM image of a finished ferric phosphate product obtained by the method for extracting iron from a nickel-iron alloy and preparing hydrogen peroxide in Example 1 of the present application (the scale bar is 30 μm);

FIG4 is another SEM image of the finished ferric phosphate product obtained by the method for extracting iron from nickel-iron alloy and preparing hydrogen peroxide in Example 1 of the present application (the scale bar is 3 μm);

FIG5 is an XRD diagram of an iron phosphate product obtained by the method for extracting iron from a nickel-iron alloy and preparing hydrogen peroxide in Example 1 of the present application.

Detailed ways

In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thoroughly and comprehensively understood.

It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation method.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

As shown in Figures 1 and 2, the method for extracting iron from a nickel-iron alloy and preparing hydrogen peroxide in one embodiment is used to prepare iron phosphate and hydrogen peroxide. Further, the method for extracting iron from a nickel-iron alloy and preparing hydrogen peroxide includes some or all of the following steps:

S1, mixing the nickel-iron alloy with acid solution, and introducing inert gas to obtain slurry.

In this embodiment, the nickel-iron alloy is mixed with an acid solution and an inert gas is introduced to obtain a slurry. In one embodiment, the acid solution is at least one of sulfuric acid, hydrochloric acid or nitric acid. In this embodiment, the acid solution is sulfuric acid. The reaction equation involved in mixing the nickel-iron alloy with the acid solution and introducing an inert gas is:
Ni+H ₂ SO ₄ =NiSO ₄ +H ₂ ↑;
Fe+H ₂ SO ₄ =FeSO ₄ +H ₂ ↑;

It can be seen that both the nickel and iron elements in the nickel-iron alloy can undergo a replacement reaction with the acid solution and eventually produce hydrogen.

Furthermore, the step of mixing the nickel-iron alloy with the acid solution and introducing an inert gas is specifically as follows: mixing the nickel-iron alloy with the acid solution, introducing an inert gas and stirring the mixture to allow the nickel-iron alloy and the acid solution to be fully mixed and reacted.

S2, heating the slurry for reaction, filtering the slurry after the reaction, and taking the filtrate to obtain the nickel-iron leaching solution.

In this embodiment, the slurry is heated to react, and the slurry after the reaction is filtered, and the filtrate is taken to obtain the nickel-iron leaching solution. In other words, the slurry is heated to react, and the slurry after the reaction is filtered, and only the filtrate is taken to obtain the nickel-iron leaching solution.

S3, adding a phosphorus source and an oxidant to the nickel-iron leaching solution for precipitation, washing, drying and dehydrating the filter residue to obtain iron phosphate.

In this embodiment, a phosphorus source and an oxidant are added to the nickel-iron leaching solution for precipitation to obtain iron phosphate and a nickel-containing filtrate; the filter residue is washed, dried, and dehydrated to obtain iron phosphate.

S4, collecting the tail gas generated in step S2, and desulfurizing and purifying the collected tail gas to obtain hydrogen.

In the present embodiment, the tail gas generated in step S2 is collected, and the collected tail gas is desulfurized and purified to obtain hydrogen. It is understandable that in addition to hydrogen, acid mist may also be entrained in the gas produced by the reaction. For example, the tail gas produced by the slurry heating reaction includes hydrogen and acid mist, and desulfurization and purification operations are required to obtain higher purity hydrogen. Furthermore, before the step of desulfurizing and purifying the collected tail gas, the method for extracting iron from nickel-iron alloy and preparing hydrogen peroxide also includes: preparing a desulfurizer for subsequent desulfurization operations. In the present embodiment, the preparation reaction equation of the desulfurizer is:
2Fe ²⁺ +2H ₂ O ₂ +2H ⁺ =2Fe ³⁺ +2H ₂ O;
Fe ³⁺ +3OH ^- =Fe(OH) ₃ ↓;
Fe(OH) ₃ =Fe ₂ O ₃ .H ₂ O (yellow iron oxide) + 2H ₂ O.

Furthermore, the reaction equation involved in the desulfurization operation of the collected tail gas is:
_Fe2O3.H2O ₊ _3H2S ₌ _Fe2S3.H2O ₊ _3H2O _;
_Fe2O3 _· _H2O + _3H2S ＝2FeS+S↓+ _4H2O ;
_Fe2S3.H2O + ₃ _/ _2O2 = _Fe2O3.H2O + _3S _↓ ;
2FeS+3/ _2O2 ₊ _H2O ₌ _Fe2O3.H2O +2S↓.

S5, adding an organic solvent and a catalyst into the hydrogen to carry out a hydrogenation-oxidation reaction to obtain a hydrogen peroxide product.

The method for extracting iron from nickel-iron alloy and preparing hydrogen peroxide comprises the following steps: firstly, mixing the nickel-iron alloy with acid solution and introducing an inert gas to obtain a slurry; then heating the slurry for reaction, filtering the slurry after the reaction, and taking the filtrate to obtain a nickel-iron leaching solution; then adding a phosphorus source and an oxidant to the nickel-iron leaching solution for precipitation, taking the filter residue for washing, drying, and dehydrating to obtain iron phosphate; then collecting the tail gas generated in step S2, and performing desulfurization and purification operations on the collected tail gas to obtain hydrogen; and finally adding an organic solvent and a catalyst to the hydrogen to perform a hydrogenation oxidation reaction operation to obtain a hydrogen peroxide product.

The method for extracting iron from nickel-iron alloy and preparing hydrogen peroxide of the present application comprises the following steps: reacting the nickel-iron alloy with acid solution under an inert atmosphere, wherein the generated gas contains no oxygen and does not generate an explosion risk; then, a part of the nickel-iron leaching solution is oxidized by adding an oxidant, and then mixed with the generated gas for desulfurization and purification operations to obtain hydrogen; since the nickel-iron alloy is used as a raw material, the tail gas generated by the slurry heating reaction during the leaching process is collected, and desulfurization and purification operations are performed to recover the hydrogen, purify the hydrogen, and then use it to prepare hydrogen peroxide, and hydrogen peroxide is prepared at the same time. The product can also be reused as an oxidant to prepare iron phosphate; the iron element in the nickel-iron alloy can be used to prepare iron phosphate, which can be further used as a precursor of lithium iron phosphate to prepare lithium iron phosphate positive electrode material. The principle of the entire method for extracting iron from the nickel-iron alloy and preparing hydrogen peroxide is relatively simple and the comprehensive recovery rate is high. At the same time, the utilization rate of iron and hydrogen production to prepare hydrogen peroxide is high, and it has good industrialization prospects and economic benefits. The method for extracting iron from the nickel-iron alloy and preparing hydrogen peroxide in the present application avoids the problem of phosphorus-containing waste liquid not being further recycled and avoids the waste of phosphorus sources.

Further, the catalyst is a Pt catalyst (platinum catalyst) or a nickel catalyst or a palladium catalyst to better perform hydrogenation and oxidation. In this embodiment, the catalyst is a Pt catalyst.

Furthermore, adding an organic solvent and a catalyst to hydrogen to carry out a hydrogenation oxidation reaction comprises: firstly adding an organic solvent and a catalyst to hydrogen to carry out a hydrogenation operation to obtain an intermediate hydride; The product is oxidized and extracted to obtain hydrogen peroxide product.

In one embodiment, in the nickel-iron alloy, the content of nickel is 15% to 40%, and the content of iron is 60% to 85%. Furthermore, in the nickel-iron alloy, the content of sulfur is 0.01% to 0.1%.

In one embodiment, the actual amount of acid added is 0.5 to 1.2 times the theoretical amount of acid. Alternatively, the actual amount of acid added is 0.6 to 1.0 times the theoretical amount of acid.

In one embodiment, the inert gas is nitrogen or argon.

In one of the embodiments, the heating temperature of the slurry heating reaction is 50°C to 90°C. Optionally, the heating temperature of the slurry heating reaction is 60°C to 85°C, so that the slurry heating reaction can better produce nickel-iron leaching solution.

In one of the embodiments, the heating time is 1 hour to 20 hours, and optionally, the heating time is 5 hours to 15 hours, so that the slurry heating reaction can better produce nickel-iron leaching solution.

In one of the embodiments, the above-mentioned method of extracting iron from nickel-iron alloy and preparing hydrogen peroxide has a high comprehensive recovery rate, the utilization rate of iron in the raw material is greater than 95%, and the utilization rate of producing hydrogen to prepare hydrogen peroxide is greater than 90%, which has good industrial prospects and economic benefits.

Furthermore, the oxidant is at least one of hydrogen peroxide, oxygen and sodium thiosulfate.

Furthermore, part of the nickel-iron leaching solution obtained in step S2 is used to prepare an iron oxide desulfurizer, thereby reducing the loss of the oxidant required for the hydrogen desulfurization operation and further improving the utilization rate of the iron element.

In one embodiment, the phosphorus source is at least one of phosphoric acid or a phosphate;

In one embodiment, the phosphate is at least one of trisodium phosphate, sodium dihydrogen phosphate, sodium monohydrogen phosphate, ammonium monohydrogen phosphate, ammonium dihydrogen phosphate or potassium phosphate.

In one embodiment, the temperature of adding a phosphorus source and an oxidant to the ferronickel leaching solution for precipitation is 60°C to 100°C, and the heating time is 3h to 10h. Optionally, the temperature of adding a phosphorus source and an oxidant to the ferronickel leaching solution for precipitation is 70°C to 90°C, and the heating time is 4h to 8h, so as to better obtain iron phosphate.

In one embodiment, the washing is pulping washing, and the liquid-to-solid ratio of the washing is 0.5 mL/g to 20 mL/g; The washing time is 0.5h to 5h.

Furthermore, the step of purifying the desulfurized gas is specifically as follows: passing the desulfurized gas into a PSA (Pressure Swing Adsorption) device for adsorption.

In one embodiment, the desulfurizing agent used to desulfurize the collected tail gas is complex iron; in one embodiment, the adsorbent used for purification is at least one of alumina, silica gel, activated carbon, or carbon molecular sieve;

In one embodiment, the organic solvent is AAQ (2-Amylanthraquinone, 2-amylanthraquinone, chemical formula is C ₁₉ H ₁₈ O ₂ ) or EAQ (2-Ethylanthraquinone, 2-ethylanthraquinone, chemical formula is C ₁₆ H ₁₂ O ₂ ). In this embodiment, the organic solvent is EAQ, which acts as a carrier of oxygen and hydrogen. Hydrogen reacts with EAQ to generate hydroanthraquinone, which then reacts with oxygen to generate hydrogen peroxide. The reaction equation involved is:
EAQ+H ₂ =EAQH ₂ ;
_EAQH2 + _O2 = _H2O2 + _EAQ .

The present application also provides an application of the method for extracting iron from a nickel-iron alloy and preparing hydrogen peroxide as described in any of the above embodiments in preparing a positive electrode material, that is, the present application also provides a method for preparing a positive electrode material, the steps of which include the method for extracting iron from a nickel-iron alloy and preparing hydrogen peroxide as described in any of the above embodiments, or one of the raw materials used in the positive electrode material is prepared by the method for extracting iron from a nickel-iron alloy and preparing hydrogen peroxide as described in any of the above embodiments. In this embodiment, the raw materials used in the positive electrode material are iron phosphate and/or hydrogen peroxide.

2. The method of extracting iron from nickel-iron alloy and preparing hydrogen peroxide of the present application uses nickel-iron alloy as raw material, collects tail gas generated during the leaching process, i.e., the heating reaction of the slurry, and performs desulfurization and purification operations to recover hydrogen and purify it, and then uses it to prepare hydrogen peroxide. At the same time, the prepared hydrogen peroxide product can also be reused as an oxidant to prepare iron phosphate;

3. The method of extracting iron from nickel-iron alloy and preparing hydrogen peroxide in the present application, the iron element in the nickel-iron alloy can be used to prepare iron phosphate, which can be further used as a precursor of lithium iron phosphate to prepare lithium iron phosphate positive electrode material. The principle of the whole method of extracting iron from nickel-iron alloy and preparing hydrogen peroxide is relatively simple and the comprehensive recovery rate is high. At the same time, the utilization rate of iron and hydrogen production to prepare hydrogen peroxide is high, which has good industrialization prospects and economic benefits, avoids the problem of phosphorus-containing waste liquid not being further recycled, and avoids the waste of phosphorus source.

Some specific examples are listed below, and if % is mentioned, it means percentage by weight. It should be noted that the following examples do not exhaust all possible situations, and the materials used in the following examples can be obtained from commercial sources unless otherwise specified.

Example 1

The method for extracting iron from nickel-iron alloy and preparing hydrogen peroxide in this embodiment comprises the following steps:

(1) crushing and grinding 25 g of nickel-iron alloy (Ni35.4%, Fe63.1%) to obtain about 23.5 g of nickel-iron powder; preparing 0.8 times the theoretical amount of 1.5 mol/L dilute sulfuric acid solution, mixing the solution with 23.5 g of nickel-iron powder, placing the solution in a closed reactor, introducing nitrogen to replace air, and obtaining a mixed slurry;

(2) heating the mixed slurry of step (1) to 80° C., and collecting hydrogen generated during the reaction through a tail gas pipeline;

(3) After adding 52 ml of phosphoric acid and 62 ml of hydrogen peroxide to the leaching solution (Fe ²⁺ concentration 41.5 g/L) obtained after the reaction in step (2), the pH was adjusted to 2.0 using sodium carbonate and heated to 80°C for precipitation reaction. 6h, after the reaction is completed, the slurry is filtered to obtain iron phosphate and nickel-containing filtrate;

(4) adding pure water to the iron phosphate slag in step (3) at a liquid-to-solid ratio of 10 mL/g for pulping and washing for 1.5 h, and then filtering to obtain wet iron phosphate slag, which was then dried and crushed to obtain precursor iron phosphate;

(5) The hydrogen collected in step (2) is desulfurized by preparing Fe ₂ O ₃ ·H ₂ O slurry with a liquid-to-solid ratio of 3 mL/g and then enters PSA pressure swing adsorption to prepare hydrogen with a purity of 99.52%;

(6) The hydrogen prepared in step (5) is used to prepare hydrogen peroxide with a content of 25.2% under the action of AAQ solvent and Pt catalyst, and the hydrogen peroxide can be recycled to the iron phosphate precipitation stage.

FIG3 is a SEM image (scale bar 30 μm) of the finished iron phosphate product obtained by the method for extracting iron from a nickel-iron alloy and preparing hydrogen peroxide in Example 1 of the present application, and FIG4 is another SEM image (scale bar 3 μm) of the finished iron phosphate product obtained by the method for extracting iron from a nickel-iron alloy and preparing hydrogen peroxide in Example 1 of the present application. It can be seen from FIG3 and FIG4 that the size of the prepared iron phosphate particles is relatively uniform, and they are all spherical particles formed by interlacing flaky primary particles. FIG5 is an XRD image of the iron phosphate product obtained by the method for extracting iron from a nickel-iron alloy and preparing hydrogen peroxide in Example 1 of the present application. It can be seen from the diffraction peaks in FIG5 that the iron phosphate prepared in the present application is consistent with the characteristic peaks in the standard card (PDF#50-1635).

Example 2

(1) crushing and grinding 50 g of nickel-iron alloy (Ni 27.6%, Fe 71.8%) to obtain about 48 g of nickel-iron powder; preparing 0.9 times the theoretical amount of 1.2 mol/L dilute sulfuric acid solution, mixing the solution with 48 g of nickel-iron powder, placing the solution in a closed reactor, introducing nitrogen to replace air, and obtaining a mixed slurry;

(2) heating the mixed slurry of step (1) to 85° C., and collecting hydrogen generated during the reaction through a tail gas pipeline;

(3) adding 48 ml of phosphoric acid and 57 ml of hydrogen peroxide to the leaching solution (Fe ²⁺ concentration 38.2 g/L) obtained after the reaction in step (2), adjusting the pH to 2.5 with sodium carbonate, heating to 70° C. for precipitation reaction for 8 h, and filtering the slurry after the reaction to obtain iron phosphate and nickel-containing filtrate;

(4) adding pure water at a liquid-to-solid ratio of 15 mL/g to the iron phosphate slag in step (3) for pulping and washing for 1.0 h, and then filtering to obtain wet iron phosphate slag, which is then dried and crushed to obtain precursor iron phosphate;

(5) The hydrogen collected in step (2) is desulfurized by Fe ₂ O ₃ ·H ₂ O slurry with a liquid-to-solid ratio of 3 mL/g and then enters PSA pressure swing adsorption to prepare hydrogen with a purity of 99.61%;

(6) The hydrogen prepared in step (5) is used to prepare hydrogen peroxide with a content of 26.3% under the action of AAQ solvent and Pt catalyst, and the hydrogen peroxide can be recycled to the iron phosphate precipitation stage.

Example 3

(1) crushing and grinding 200 g of nickel-iron alloy (Ni35.4%, Fe63.1%) to obtain about 192 g of nickel-iron powder; preparing 0.7 times the theoretical amount of 1.2 mol/L dilute sulfuric acid solution, mixing it with 48 g of the nickel-iron powder, placing it in a closed reactor, and introducing nitrogen to replace the air to obtain a mixed slurry;

(2) heating the mixed slurry of step (1) to 75° C., and collecting hydrogen generated during the reaction through a tail gas pipeline;

(3) adding 91.7 g of sodium phosphate and 48 ml of hydrogen peroxide to the leaching solution ( ^Fe2+ concentration 32.2 g/L) obtained after the reaction in step (2), adjusting the pH to 1.8 with sodium carbonate, heating to 90° C. for precipitation reaction for 4 h, and filtering the slurry after the reaction to obtain iron phosphate and nickel-containing filtrate;

(4) The iron phosphate slag in step (3) was added with pure water at a liquid-to-solid ratio of 12 mL/g for pulping and washing. The washing time was 1.0 h. After the washing, the wet iron phosphate slag was filtered to obtain the precursor. Iron phosphate;

(5) The hydrogen collected in step (2) is desulfurized by Fe ₂ O ₃ ·H ₂ O slurry with a liquid-to-solid ratio of 2.5 mL/g and then enters PSA pressure swing adsorption to prepare hydrogen with a purity of 99.49%;

(6) The hydrogen prepared in step (5) is used to prepare hydrogen peroxide with a content of 27.1% under the action of EAQ solvent and Pt catalyst, and the hydrogen peroxide can be recycled to the iron phosphate precipitation stage.

Comparative Example 1

A method for preparing iron phosphate for lithium battery, the specific steps are as follows:

(1) Iron dissolving: Iron flakes and dilute phosphoric acid are continuously added to the first reactor to produce ferrous liquid and hydrogen-rich gas. The ferrous liquid is output after concentration compensation adjustment in the second reactor;

(2) Hydrogen-rich gas water washing: The hydrogen-rich gas produced in the first reaction kettle of iron dissolving is discharged from the gas outlet at the top of the kettle and enters the water washing tower for water washing and separation before entering the gas cabinet;

(3) Compression: The hydrogen-rich gas in the gas cabinet is pressurized to 1.2 MPa by a compressor and sent to the deoxygenation reactor;

(4) Hydrogen purification: The deoxygenated hydrogen-rich gas enters the pressure swing adsorption tower for adsorption. Various impurity gases with strong adsorption capacity in the raw gas are adsorbed by the adsorbent, and the hydrogen product gas with weaker adsorption capacity is directly discharged from the exhaust port at the top of the adsorption tower to the hydrogen buffer tank, which is connected to the hydrogen storage tank;

(5) Impurity gas desorption: desorption is carried out by depressurization/flushing to complete the regeneration of the adsorbent;

(6) Adsorption tower pressurization: Use product gas to raise the pressure in the adsorption tower to the pressure required for adsorption and enter the next adsorption cycle;

(7) The ferrous liquid produced in the second reactor is output, oxidized, mixed with phosphate, pH adjusted, precipitated, washed, filtered, and dried to obtain ferric phosphate.

In comparative example 1, iron sheets are used to react with phosphoric acid to produce hydrogen, while the present application uses nickel-iron alloy to react with sulfuric acid to produce hydrogen, and an inert gas is introduced before the reaction to avoid the risk of hydrogen and oxygen mixing to form an explosive mixture after leakage; comparative example 1 requires the use of hydrogen and oxygen to react to generate water for deoxygenation, and the recovery rate of hydrogen is greatly reduced, while the hydrogen produced by the present application does not contain oxygen, and can be desulfurized without causing hydrogen recovery losses; the present application also prepares the purified hydrogen into hydrogen peroxide, which is then reused in the system to prepare iron phosphate, thereby realizing process cyclicity and having industrial prospects.

The finished iron phosphate products prepared in the above Examples 1 to 3 were tested for physical and chemical indicators, and the results are shown in Table 1 below:

Table 1: Physical and chemical index test results of anhydrous ferric phosphate prepared in Examples 1-3

It can be seen from the results in Table 1 that the various physical and chemical indicators of the iron phosphate prepared in Examples 1 to 3 of the present application meet the iron phosphate standards for positive electrode materials.

The iron phosphate prepared in the above Examples 1 to 3 was prepared into lithium iron phosphate according to a conventional method, and the electrical properties of the prepared lithium iron phosphate were tested respectively. The results are shown in Table 2:

Table 2: Comparison of compaction density and electrical performance test results of lithium iron phosphate powder synthesized from iron phosphate of Examples 1-3 and Comparative Example 1

From the data in Table 2, it can be seen that the initial discharge specific capacity of the lithium iron phosphate prepared in Examples 1 to 3 of the present application is above 160.5 mAh/g, and the capacity retention rate after 100 cycles is greater than 96%. However, the initial discharge specific capacity of the lithium iron phosphate prepared in Comparative Example 1 is only 143.9 mAh/g, and the capacity retention rate after 100 cycles is only 94.78. It can be seen that the iron phosphate synthesized lithium iron phosphate powder of the present application has better compaction density and electrical properties.

The hydrogen collected from the leaching solution prepared in Examples 1 to 3 above was analyzed after desulfurization and purification, and the results are shown in Table 3:

Table 3: Gas analysis results after hydrogen purification

It can be seen from the data in Table 3 that the percentage of hydrogen collected by the leachate prepared in Examples 1 to 3 of the present application reaches more than 99.49%, while the percentage of hydrogen in Comparative Example 1 is 98.91. Compared with Comparative Example 1, the hydrogen recovery rate of Examples 1 to 3 of the present application is higher.

The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent application. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims. .

Claims

A method for extracting iron from a nickel-iron alloy and preparing hydrogen peroxide, comprising:

S1: mixing the nickel-iron alloy with acid solution and introducing an inert gas to obtain a slurry;

S2: heating the slurry to react, filtering the slurry after the reaction, and taking the filtrate to obtain a nickel-iron leaching solution;

S3: adding a phosphorus source and an oxidant to the nickel-iron leaching solution for precipitation, washing, drying and dehydrating the filter residue to obtain iron phosphate;

S4: collecting the tail gas generated in step S2, and performing desulfurization and purification operations on the collected tail gas to obtain hydrogen;

S5: adding an organic solvent and a catalyst to the hydrogen to carry out a hydrogenation-oxidation reaction to obtain a hydrogen peroxide product.
The method for extracting iron from a nickel-iron alloy and preparing hydrogen peroxide according to claim 1, wherein, in the nickel-iron alloy, the content of nickel element is 15% to 40%, and the content of iron element is 60% to 85%.
The method for extracting iron from nickel-iron alloy and preparing hydrogen peroxide according to claim 1, wherein the acid solution is at least one of sulfuric acid, hydrochloric acid or nitric acid.
The method for extracting iron from nickel-iron alloy and preparing hydrogen peroxide according to claim 1, wherein the inert gas is nitrogen or argon.
The method for extracting iron from nickel-iron alloy and preparing hydrogen peroxide according to claim 1, wherein the heating temperature of the slurry heating reaction is 50° C. to 90° C., and the heating time is 1 h to 20 h.
The method for extracting iron from nickel-iron alloy and preparing hydrogen peroxide according to claim 1, wherein the phosphorus source is at least one of phosphoric acid or phosphates; and the phosphate is at least one of trisodium phosphate, sodium dihydrogen phosphate, sodium monohydrogen phosphate, ammonium monohydrogen phosphate, ammonium dihydrogen phosphate or potassium phosphate.
The method for extracting iron from nickel-iron alloy and preparing hydrogen peroxide according to claim 1, wherein the temperature for adding a phosphorus source and an oxidant to the nickel-iron leaching solution for precipitation is 60° C. to 100° C., and the heating time is 3h～10h.
The method for extracting iron from nickel-iron alloy and preparing hydrogen peroxide according to claim 1, wherein the washing is pulping washing, the liquid-to-solid ratio of the washing is 0.5 mL/g to 20 mL/g; and the washing time is 0.5 h to 5 h.
The method for extracting iron from nickel-iron alloy and preparing hydrogen peroxide according to claim 1, wherein the desulfurizing agent for desulfurizing the collected tail gas is complex iron;

Optionally, the adsorbent used for purification is at least one of alumina, silica gel, activated carbon, or carbon molecular sieve.
Application of the method for extracting iron from a nickel-iron alloy and preparing hydrogen peroxide as described in any one of claims 1 to 9 in preparing a positive electrode material.