Preparation method and application of Fenton reagent based on waste lithium iron phosphate electrode material

Abstract

The invention belongs to the field of solid waste resource utilization, and discloses a preparation method and application of a Fenton reagent based on a waste lithium iron phosphate electrode material. According to the method, the solid waste of the waste lithium iron phosphate electrode material is used as an iron source for preparing the Fenton reagent, and metal elements without recovery value in the waste lithium iron phosphate electrode material can be subjected to resource utilization under the condition that multiple purification treatment is not needed. In addition, the strong acid introduced in the process of recycling the lithium iron phosphate electrode material through hydrometallurgy can be directly used for regulating and controlling the pH value of the Fenton reaction, so that resource recycling of the lithium iron phosphate electrode material and effective utilization of the waste strong acid are realized. On the other hand, the Fenton reagent is prepared on the basis of the waste lithium iron phosphate electrode material, so that the addition of ferric salt required by the Fenton reaction can be reduced, and a large amount of strong acid is reduced or even not required to be added from the outside, thereby greatly reducing the operation cost of treating wastewater by the Fenton reaction, and realizing the effect of treating waste by waste; and economic benefits and environmental benefits of resource recycling and wastewater treatment of the waste lithium iron phosphate batteries are comprehensively considered.

Description

Technical Field

[0001] The invention belongs to the field of solid waste resource utilization, and relates to a preparation method of a Fenton reagent based on waste lithium iron phosphate electrode materials and application thereof. Background Art

[0002] The main source of global greenhouse gases is the use of fossil energy. In order to achieve energy conservation and emission reduction, the use of fossil fuels, especially fossil fuel vehicles, must be reduced. Electric vehicles use batteries to store energy and do not involve fuel combustion. Therefore, they can effectively reduce carbon emissions, protect the environment, and effectively curb global warming. Lithium iron phosphate batteries have many advantages such as abundant raw materials, low price, non-toxicity, simple production process, good safety, and good thermal stability. At present, they have become one of the main power sources for electric vehicles in my country. Although lithium iron phosphate batteries occupy half of the power batteries, they are now facing more and more problems of lithium iron phosphate battery retirement and recycling. If these waste lithium iron phosphate batteries cannot be recycled in time and effectively, they will not only cause serious pollution to the environment, but also cause serious waste of resources. However, the material components of lithium iron phosphate batteries are complex, and the separation and extraction of valuable metals require advanced technology and complex processes, so the recycling cost is high, and the market value of the recycled iron element is extremely low, resulting in poor economic benefits and low recycling rate of lithium iron phosphate batteries. In addition, hydrometallurgical technology is currently mainly used to recycle lithium iron phosphate battery materials. A large amount of waste strong acid in the recycling process requires further treatment, further increasing the cost of recycling waste lithium iron phosphate batteries.

[0003] On the other hand, high-concentration, high-salinity, and difficult-to-degrade wastewater has complex water quality components, high organic matter content, COD generally above 10,000 mg / L, and generally contains toxic and hazardous substances, which has become a difficult problem for sewage treatment in my country and even in the world, and has seriously damaged the environmental ecosystem. Homogeneous Fenton reaction is an advanced oxidation technology that uses Fe 2+ It can degrade pollutants by generating strong oxidative free radicals with H2O2. It has extremely strong non-selective oxidizing ability and can efficiently degrade various organic pollutants. It has the characteristics of fast reaction speed, wide applicability and good degradation effect. It is one of the main treatment methods for high-concentration and highly toxic wastewater. However, the homogeneous Fenton method consumes a large amount of hydrogen peroxide and iron salts, and the optimal reaction pH reaction activity range usually needs to be regulated between 2.5-3, resulting in high operating costs for homogeneous Fenton wastewater treatment, and the need to add a large amount of strong acid for pH value regulation.

[0004] On the one hand, the iron element in waste lithium iron phosphate batteries is cheap, resulting in low economic recycling value of waste lithium iron phosphate batteries. Random disposal will cause serious solid waste environmental pollution and resource waste problems. The most commonly used hydrometallurgical recovery technology will also produce waste acid; on the other hand, the existing Fenton reagent degradation of wastewater requires the addition of a large amount of divalent iron and a large amount of acid to adjust the pH, which greatly increases the cost of wastewater treatment. Summary of the invention

[0005] In order to overcome the deficiencies of the prior art, realize the low-cost and high-efficiency recycling of iron elements in waste lithium iron phosphate batteries and the effective degradation of high-concentration wastewater, the present invention provides a method for preparing a Fenton reagent based on waste lithium iron phosphate electrode materials and its application, and utilizes waste lithium iron phosphate battery electrode materials to treat high-concentration wastewater. In view of the low recycling value of iron in waste lithium iron phosphate battery materials and the complex separation and extraction process, and the problem that a large amount of strong acid is generated during the recycling process and needs to be treated urgently, the present invention uses solid waste of waste lithium iron phosphate electrode materials as the iron source for preparing Fenton reagents, avoiding multiple complex purification treatments of metal elements in waste lithium iron phosphate. In addition, the strong acid introduced in the process of hydrometallurgical recovery of lithium iron phosphate electrode materials can be directly used to regulate the pH value of the Fenton reaction, thereby realizing the resource recycling of lithium iron phosphate electrode materials and the effective utilization of waste strong acids. On the other hand, the preparation of Fenton reagent based on waste lithium iron phosphate electrode materials can reduce the amount of iron salt required for the Fenton reaction, reduce or even eliminate the need to add large amounts of strong acid from the outside, thereby significantly reducing the operating cost of Fenton reaction wastewater treatment, achieving "waste treatment with waste", and taking into account the economic and environmental benefits of the resource recycling of waste lithium iron phosphate batteries and wastewater treatment.

[0006] The above object of the present invention is achieved through the following technical solutions:

[0007] A method for preparing Fenton reagent based on waste lithium iron phosphate electrode materials, the specific steps are as follows:

[0008] S1. After collecting the waste lithium iron phosphate electrode material, the waste lithium iron phosphate electrode material is subjected to high temperature calcination and oxidation under oxygen-containing atmosphere;

[0009] S2. Dissolve the material oxidized in step S1 using a strong acid to obtain a solution containing trivalent iron ions;

[0010] S3. Adding a reducing agent to the solution containing ferric ions obtained in step S2 to convert ferric ions into ferrous ions to obtain a ferrous solution, which is used as a source of ferrous iron in Fenton's reagent;

[0011] S4. The ferrous iron solution obtained in step S3 is mixed with hydrogen peroxide to obtain a homogeneous Fenton reagent.

[0012] Furthermore, the waste lithium iron phosphate electrode material in step S1 comes from retired lithium iron phosphate batteries of electric vehicles, communication base stations, grid energy storage, etc.

[0013] Furthermore, the oxygen-containing atmosphere in step S1 is one or more of air, oxygen and argon, oxygen and nitrogen. Preferably, the oxygen-containing atmosphere in step S1 is in air atmosphere.

[0014] Furthermore, the high temperature calcination conditions in step S1 are: calcination time is 1 to 5 hours, and calcination temperature is 500 to 900° C. Preferably, calcination time is 1 to 2 hours, and calcination temperature is 500 to 700° C.

[0015] Further, the strong acid in step S2 is any one or more of sulfuric acid, hydrochloric acid, and nitric acid, and the concentration of the strong acid is 1 to 3 mol / L. Preferably, the strong acid in step S2 is sulfuric acid. The concentration of sulfuric acid is 2 to 3 mol / L.

[0016] Further, the liquid-solid ratio of the strong acid to the lithium iron phosphate in step S2 is 6-10: 1. Preferably, the liquid-solid ratio of the strong acid to the lithium iron phosphate in step S2 is 8-10:1.

[0017] Further, the dissolution conditions in step S2 are: dissolution temperature of 30-70°C, stirring speed of 100-500 r / min, and reaction time of 1-5 hours. Preferably, the dissolution conditions in step S2 are: dissolution temperature of 50-70°C, stirring speed of 200-300 r / min, and reaction time of 3-5 hours.

[0018] Furthermore, the reducing agent added in step S3 is any one or more of iron powder, iron block, and iron filings, and the reducing agent and Fe 3+ The molar ratio of is 0.8-1.5:2. Preferably, the reducing agent is iron powder; preferably, the iron powder and Fe 3+ The molar ratio is 0.9-1.2:2.

[0019] Further, the mass ratio of ferrous iron to hydrogen peroxide in the homogeneous Fenton reagent in step S4 is 1:40-50. Preferably, the mass ratio of ferrous iron to hydrogen peroxide in the homogeneous Fenton reagent in step S4 is 1:45-50.

[0020] Further, the mixing conditions in step S4 are: the mixing temperature is 10-25°C, and the mixing stirring speed is 100-600 r / min. Preferably, the mixing conditions in step S4 are: the mixing temperature is 15-25°C, and the mixing stirring speed is 300-600 r / min.

[0021] The present invention also claims to protect the application of the Fenton reagent prepared by the above preparation method in treating wastewater.

[0022] The specific application is: adding the prepared homogeneous Fenton reagent into phenol wastewater, and adjusting the pH of the wastewater to 2-4 using the waste strong acid introduced in step S2.

[0023] Furthermore, the pH is preferably adjusted to 2.5-3 with a strong acid.

[0024] Furthermore, the wastewater is any one or more of phenol wastewater, printing and dyeing wastewater, pesticide wastewater, coking wastewater, and garbage leachate.

[0025] Further, the initial TOC value of the wastewater is 95-105 mg / L, and more preferably, the initial TOC value of the wastewater is 95-100 mg / L.

[0026] The present invention provides a preparation method of Fenton reagent based on waste lithium iron phosphate electrode material and its application in treating wastewater. The waste lithium iron phosphate electrode material is calcined at high temperature under oxygen-containing atmosphere; the oxidized lithium iron phosphate is dissolved by strong acid to obtain a solution containing trivalent iron ions; a reducing agent is added to convert the trivalent iron ions into divalent iron ions as the source of divalent iron in the Fenton reagent; the reagent is further mixed with hydrogen peroxide to obtain a homogeneous Fenton reagent, and the waste strong acid used for acid leaching of the waste lithium iron phosphate is used to adjust the pH of the wastewater to the optimal oxidation range. The reagent is applied to wastewater to achieve mineralization of the wastewater through a homogeneous Fenton reaction.

[0027] The beneficial effects of the present invention compared with the prior art are:

[0028] The present invention extracts high-content iron components from waste lithium iron phosphate electrode materials and uses the iron components as the source of divalent iron in the homogeneous Fenton process. In the process of extracting the iron components, the strong acid contained in the iron ion solution can directly adjust the pH of the wastewater to 3. This not only makes full use of the waste strong acid in the acid leaching process and reduces the addition of acid in the homogeneous Fenton process, but also effectively solves the solid waste pollution of waste lithium iron phosphate batteries and the water pollution of wastewater, thereby achieving the good economic and social application value of "treating waste with waste". BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 These are SEM images of lithium iron phosphate before and after calcination in Example 1, wherein Figure a is the SEM image before calcination of lithium iron phosphate; and Figure b is the SEM image after calcination of lithium iron phosphate.

[0030] Figure 2 These are the results of the mineralization of phenol wastewater in Comparative Example 1 and Comparative Example 2.

[0031] Figure 3 This is a comparison chart of the results of the mineralization of phenol wastewater using the homogeneous Fenton reagent prepared in Examples 1-4.

[0032] Figure 4 It is a process diagram of the preparation method of the present invention. DETAILED DESCRIPTION

[0033] The present invention is described in detail below by specific examples, but the protection scope of the present invention is not limited. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0034] Comparative Example 1

[0035] 0.25 g of thiosulfate heptahydrate was mixed with H2O2 (1600 mg / L) and added into 500 mL of 60 mg / L phenol wastewater. Sulfuric acid was added dropwise to adjust the pH to 3. Samples were taken every five minutes. After standing, the supernatant was taken. The removal rate of phenol wastewater was 57.61%.

[0036] Comparative Example 2

[0037] 0.1g of commercial lithium iron phosphate positive electrode material powder was used, and it was calcined at 700℃ in an air atmosphere for 1h, the starting temperature was 20℃, and the heating rate was 1℃ / min. The calcined material was added to a beaker, and 2mL2.5mol / L H2SO4 was added, and it was placed on a magnetic stirrer at 60℃, 300r / min to react for 5h, and then filtered to obtain a filtrate containing trivalent iron ions. 0.1g of iron powder was added to the filtrate and reacted for 30min, and the trivalent iron in the filtrate was converted into divalent iron to obtain a divalent iron solution. The divalent iron solution was mixed with 1600mg / L hydrogen peroxide and added to 500mL 60mg / L phenol wastewater, the pH was adjusted to 3, and samples were taken every five minutes. After standing, the supernatant was taken, and its removal rate for phenol wastewater was 56.25%. Example 1

[0038] 0.1g of waste lithium iron phosphate battery powder (after dismantling retired lithium iron phosphate batteries from electric vehicles, communication base stations, grid energy storage, etc., the positive electrode part of the lithium iron phosphate is crushed to obtain powder) is placed in an air atmosphere and calcined at 600°C. The calcination time is 1h, the starting temperature is 20°C, and the heating rate is 1°C / min: the calcined lithium iron phosphate is added to a beaker, and 10mL 2.5mol / L H2SO4 is added, and it is placed on a magnetic stirrer at 60°C and 300r / min for 4h, and then filtered to obtain a filtrate containing trivalent iron ions; 0.05g of iron powder is added to the filtrate and reacted for 30min, and the trivalent iron in the filtrate is converted into divalent iron; a divalent iron solution is obtained; the divalent iron solution is mixed with 5000mg / L hydrogen peroxide and added to 500mL 60mg / L phenol wastewater, the pH is adjusted to 3, and samples are taken every five minutes. After standing, the upper clear liquid is taken.

[0039] Example 2

[0040] 0.1g of waste lithium iron phosphate battery powder (after dismantling retired lithium iron phosphate batteries from electric vehicles, communication base stations, power grid energy storage, etc., the positive electrode part of the lithium iron phosphate is crushed to obtain powder) is placed in an air atmosphere and calcined at 700°C for 1h, the starting temperature is 20°C, and the heating rate is 1°C / min; the calcined lithium iron phosphate is obtained; the calcined lithium iron phosphate is added to a beaker, and 2mL 2.5mol / L H2SO4 is added, and it is placed on a magnetic stirrer at 60°C and 300r / min for reaction for 5h, and then filtered to obtain a filtrate containing trivalent iron ions; 0.1g of iron powder is added to the filtrate and reacted for 30min, and the trivalent iron in the filtrate is converted into divalent iron; a divalent iron solution is obtained; the divalent iron solution is mixed with 1600mg / L hydrogen peroxide and added to 500mL 60mg / L phenol wastewater, the pH is adjusted to 2, and samples are taken every five minutes, and the upper clear liquid is taken after standing.

[0041] Example 3

[0042] 0.05g of waste lithium iron phosphate battery powder (after dismantling retired lithium iron phosphate batteries from electric vehicles, communication base stations, grid energy storage, etc., the positive electrode part of the lithium iron phosphate is crushed to obtain powder) is placed in an air atmosphere and calcined at 600°C for 1h, the starting temperature is 20°C, and the heating rate is 1°C / min; the calcined lithium iron phosphate is obtained; the calcined lithium iron phosphate is added to a beaker, and 0.5mL 0.5mol / L H2SO4 is added, and it is placed on a magnetic stirrer for reaction at 60°C and 300r / min for 4h, and then filtered to obtain a filtrate containing trivalent iron ions; 0.1g of iron powder is added to the filtrate and reacted for 30min, and the trivalent iron in the filtrate is converted into divalent iron; a divalent iron solution is obtained; the divalent iron solution is mixed with 2400mg / L hydrogen peroxide and added to 500mL 60mg / L phenol wastewater, the pH is adjusted to 5, samples are taken every five minutes, and the upper clear liquid is taken after standing.

[0043] Example 4

[0044] 0.05g of waste lithium iron phosphate battery powder (after dismantling retired lithium iron phosphate batteries from electric vehicles, communication base stations, grid energy storage, etc., the positive electrode part of the lithium iron phosphate is crushed to obtain powder) is placed in an air atmosphere and calcined at 600°C for 1h, the starting temperature is 20°C, and the heating rate is 1°C / min; the calcined lithium iron phosphate is obtained; the calcined lithium iron phosphate is added to a beaker, and 1mL 1.5mol / L H2SO4 is added, and it is placed on a magnetic stirrer for reaction at 60°C and 300r / min for 2h, and then filtered to obtain a filtrate containing trivalent iron ions; 0.2g of iron powder is added to the filtrate and reacted for 60min, and the trivalent iron in the filtrate is converted into divalent iron; a divalent iron solution is obtained; the divalent iron solution is mixed with 1600mg / L hydrogen peroxide and added to 500mL 60mg / L phenol wastewater, the pH is adjusted to 4, samples are taken every five minutes, and the upper clear liquid is taken after standing.

[0045]

[0046]

[0047] The above-described embodiments are only preferred embodiments of the present invention, but not all feasible embodiments of the present invention. For those skilled in the art, any obvious changes made thereto without departing from the principles and spirit of the present invention should be considered to be included in the scope of protection of the claims of the present invention.

Claims

1. A method for preparing Fenton reagent based on waste lithium iron phosphate electrode material, characterized in that: The specific steps are as follows: S1. After collecting the waste lithium iron phosphate electrode material, the waste lithium iron phosphate electrode material is subjected to high temperature calcination and oxidation under oxygen-containing atmosphere; S2. Dissolve the material oxidized in step S1 using a strong acid to obtain a solution containing trivalent iron ions; S3. Adding a reducing agent to the solution containing ferric ions obtained in step S2 to convert ferric ions into ferrous ions to obtain a ferrous solution, which is used as a source of ferrous iron in Fenton's reagent; S4. The ferrous iron solution obtained in step S3 is mixed with hydrogen peroxide to obtain a homogeneous Fenton reagent.

2. A method for preparing a Fenton reagent based on waste lithium iron phosphate electrode material as claimed in claim 1, characterized in that: The oxygen-containing atmosphere in step S1 is one or more of air, oxygen and argon, or oxygen and nitrogen.

3. A method for preparing a Fenton reagent based on waste lithium iron phosphate electrode material as claimed in claim 1, characterized in that: The high temperature calcination conditions in step S1 are: calcination time is 1 to 5 hours, and calcination temperature is 500 to 900°C.

4. A method for preparing a Fenton reagent based on waste lithium iron phosphate electrode material as claimed in claim 1, characterized in that: The strong acid in step S2 is any one or more of sulfuric acid, hydrochloric acid and nitric acid, and the concentration of the strong acid is 1 to 3 mol / L.

5. A method for preparing a Fenton reagent based on waste lithium iron phosphate electrode material as claimed in claim 1, characterized in that: The liquid-to-solid ratio of the strong acid to the lithium iron phosphate in step S2 is 6-10:

1.

6. A method for preparing a Fenton reagent based on waste lithium iron phosphate electrode material as claimed in claim 1, characterized in that: The dissolution conditions in step S2 are: dissolution temperature of 30 to 70° C., stirring speed of 100 to 500 r / min, and reaction time of 1 to 5 hours.

7. A method for preparing a Fenton reagent based on waste lithium iron phosphate electrode material as claimed in claim 1, characterized in that: The reducing agent added in step S3 is any one or more of iron powder, iron block, and iron filings. 3+ The molar ratio is 0.8-1.5:

2.

8. A method for preparing a Fenton reagent based on waste lithium iron phosphate electrode material as claimed in claim 1, characterized in that: The mass ratio of ferrous iron to hydrogen peroxide in the homogeneous Fenton reagent in step S4 is 1:40-50; the mixing conditions in step S4 are: the mixing temperature is 10-25° C., and the mixing stirring speed is 100-600 r / min.

9. A Fenton reagent prepared based on waste lithium iron phosphate electrode material as described in any one of claims 1 to 8 and its use in treating wastewater.

10. The use according to claim 9, wherein the prepared homogeneous Fenton reagent is added to phenol wastewater, and the pH of the wastewater is adjusted to 2-4 using the waste strong acid introduced in step S2.

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