Preparation method and application of cobaltosic oxide catalyst

Abstract

The invention discloses a preparation method and application of a cobaltosic oxide catalyst, and the preparation method of the cobaltosic oxide catalyst comprises the following steps: mixing positive electrode powder of a waste lithium cobaltate battery with a purification agent, spreading the mixture in a reaction device, and carrying out oxidizing roasting treatment to obtain the cobaltosic oxide catalyst. The waste lithium ion battery material in the market is fully utilized to prepare the cobaltosic oxide catalyst, the extraction rate and selectivity of cobalt element are improved by improving the preparation conditions, and the prepared cobaltosic oxide catalyst has catalytic performance equivalent to that of a commercial cobaltosic oxide catalyst and can be used as a catalyst for degrading organic wastewater. Besides, the method directly utilizes the waste positive electrode material to prepare the high-efficiency catalyst, so that not only is the use of expensive high-purity metal salt avoided, but also the added-value utilization of waste is realized, the preparation of the high-added-value catalyst at low cost is realized, and the method has important economic and social benefits.

Description

Technical Field

[0001] The invention belongs to the technical field of resource processing of waste lithium-ion batteries, and specifically relates to a method for preparing a cobalt tetroxide catalyst and application thereof. Background Art

[0002] With the rapid replacement of portable electronic products and the rapid development of the new energy power vehicle industry, a large number of lithium-ion batteries are scrapped and retired. Lithium-ion batteries at the end of their service life contain a large amount of organic electrolytes, graphite and heavy metals, which will affect human health and the healthy development of the new energy industry. Voluntary recycling of retired lithium-ion batteries is the key to achieving a win-win situation for the economy and the environment and is the key to solving the problem.

[0003] At present, the industrial production of lithium-ion battery resource recycling mainly adopts two methods: pyrometallurgy adopted in Europe and the United States and hydrometallurgy adopted in my country. Pyrometallurgy directly crushes the waste batteries and then performs high-temperature reduction smelting to obtain Fe-Co-Ni alloy, in which the lithium resources are discarded in the form of slag. Domestic hydrometallurgical enterprises mainly use sulfuric acid as leaching agent and hydrogen peroxide as reducing agent to leach metals and then perform graded extraction. This method can achieve high-efficiency recovery of metals such as lithium, cobalt, nickel, and manganese. However, due to the coexistence of multiple metal ions in the acid leaching system, the extraction and separation process is complicated and long, which is very easy to cause metal loss and reagent loss during the recovery process and has the risk of secondary pollution.

[0004] The salting roasting method can significantly reduce the decomposition temperature of the positive electrode material by adding additives, and is widely used in the processing and recycling of failed lithium-ion battery positive electrode materials. Depending on the additives, the salting roasting process mainly includes sulfation roasting (or sulfidation roasting), chlorination roasting and nitration roasting. Lin et al. conducted a study on lithium extraction by sulfation roasting with NCM positive electrode powder. After fully mixing and drying the positive electrode powder with 98wt% concentrated sulfuric acid, the powder was roasted at 800℃ for 120min, and the Li leaching rate was 96.92wt%. The leaching rates of Al, Cu, Ni, Co, and Mn were all less than or about 1wt%. The Li leaching rate of this method is relatively high, but it needs to be carried out under strong acid and high temperature conditions, and Al, Cu, Ni, Co, and Mn cannot be selectively separated. In the inventor's preliminary research, NH4Cl was used as a chlorinating agent to chlorinate and roast LMO positive electrode powder in an oxygen atmosphere to achieve selective chlorination of lithium, and the Li leaching rate reached 91.73wt%. Peng et al. obtained a Li leaching rate of 93 wt % by water leaching after nitration (70°C, 5 h, nitric acid waste ratio of 30 mmol / g) and selective roasting (250°C, 1 h). Although the reaction conditions of the above two methods are milder, the leaching rate and selectivity are lower. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and provide a method for preparing a cobalt tetroxide catalyst and its application. The method for preparing a cobalt tetroxide catalyst has the advantages of mild reaction conditions, high yield and high selectivity, and the prepared cobalt tetroxide catalyst has good catalytic effect.

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing a cobalt oxide catalyst comprises: mixing the cathode powder of a waste lithium cobalt oxide battery with a purification agent, spreading the mixture in a reaction device, and performing an oxidation roasting treatment to obtain a cobalt oxide catalyst;

[0008] The purifying agent is at least one of NaHSO4, KHSO4, (NH4)2SO4, NH4HSO4, NaNH4SO4, NH4NO3, NH4Cl, and NaCl, and the molar ratio of the negative charge of the positive electrode powder to the negative charge of the anion in the purifying agent is 1:4-8;

[0009] The thickness of the positive electrode powder and the mixed purification agent is not more than 2 cm;

[0010] The temperature of the oxidation roasting is 500-700°C, the time of the oxidation roasting is 0.5-2h, and the oxygen partial pressure in the oxidation roasting atmosphere is not less than 10kPa.

[0011] Preferably, the atmosphere for oxidative roasting is oxygen or air, and the flow rate of the atmosphere is 50 to 100 mL / min.

[0012] Preferably, the preparation method further comprises: after the oxidative roasting treatment, ball milling and water washing the product.

[0013] More preferably, the ball milling speed is 2000-3000 rpm, and the ball milling time is 0.5-1 h.

[0014] More preferably, the solid-liquid ratio of the water immersion washing is 50-100 g / L, and the time of the water immersion washing is 1-2 h.

[0015] Preferably, the positive electrode powder is prepared by disassembling waste lithium cobalt oxide batteries to obtain positive electrode sheets, subjecting the positive electrode sheets to pyrolysis treatment to remove a binder, and then separating and collecting the positive electrode sheets.

[0016] More preferably, the pyrolysis treatment is carried out in an inert atmosphere, the pyrolysis treatment temperature is 450 to 550° C., and the pyrolysis treatment time is 1 to 2 hours.

[0017] A cobalt tetroxide catalyst is prepared by the above preparation method.

[0018] The cobalt tetroxide catalyst prepared by the above preparation method is used as a catalytic material.

[0019] A photocatalyst comprises the cobalt tetroxide catalyst prepared by the above preparation method.

[0020] The present invention has at least the following beneficial effects:

[0021] The present invention makes full use of waste lithium-ion battery materials on the market to prepare cobalt tetroxide catalysts. By improving the preparation conditions, the extraction rate and selectivity of the cobalt element are improved. The prepared cobalt tetroxide catalyst has comparable catalytic performance to commercial cobalt tetroxide catalysts and can be used as a catalyst for degradation of organic wastewater. In addition, the present method directly uses waste positive electrode materials to prepare high-efficiency catalysts, which not only avoids the use of expensive high-purity metal salts, but also realizes the added value of waste, and realizes the preparation of high-value-added catalysts at low cost, which has important economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The process route diagram of the present invention for preparing cobalt tetroxide catalyst from waste lithium cobalt oxide battery positive electrode material;

[0023] Figure 2 The morphology of the cathode powder (a, b) and the prepared cobalt oxide catalyst (c, d) used in Example 1;

[0024] Figure 3 The X-ray diffraction (XRD) diagram of the cobalt oxide catalyst prepared in Examples 1 to 6;

[0025] Figure 4 This is a graph showing the degradation efficiency of the cobalt tetraoxide catalyst prepared in Examples 1 to 6 when used to catalyze the degradation of tetracycline. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further illustrated and described below through specific implementation methods.

[0027] In the following examples, the water used can be one or more of distilled water, purified water, and drinking water; unless otherwise specified, the detection methods in the following examples are conventional detection methods; the reagents in the following examples are purchased from commercial channels unless otherwise specified.

[0028] In the following examples, the positive electrode powder is obtained by disassembling waste lithium cobalt oxide batteries to obtain positive electrode sheets, and then pyrolyzing at 450° C. for 1 hour to remove the binder. In other possible implementations, the positive electrode powder can be obtained by disassembling and purifying waste lithium cobalt oxide batteries using technical means commonly used by those skilled in the art.

[0029] In the following examples, in the molar ratio of positive electrode powder to purification reagent, the amount of positive electrode powder is calculated as the mass of positive electrode powder / molecular weight of lithium cobalt oxide, and the amount of purification reagent is calculated as the amount of negative charge of its anion.

[0030] Example 1

[0031] This embodiment provides a method for preparing a cobalt trioxide catalyst. Figure 1 , including the following steps:

[0032] 1. The positive electrode powder and NH4Cl were uniformly mixed at a molar ratio of 1:6, laid in a reaction vessel with a thickness of 0.5 cm, and then oxidized and roasted in air with an oxygen partial pressure of 20 kPa. The air flow rate was controlled at 50 mL / min, the heating rate was 5 °C / min, the reaction temperature was 500 °C, and the reaction time was 0.5 h.

[0033] 2. The residue after the reaction was ball-milled, washed with water, and finally filtered and dried to obtain a cobalt oxide catalyst, wherein the ball-milling conditions were: a rotation speed of 2000 rpm, and a time of 1 hour; and the water-immersion washing conditions were: a solid-liquid ratio of 50 g / L, and a time of 1 hour. Among them, the impurity ion removal rate was 99.23%, and the yield of the cobalt oxide catalyst was 99.34%.

[0034] Example 2

[0035] This embodiment provides a method for preparing a cobalt trioxide catalyst. Figure 1 , including the following steps:

[0036] 1. The positive electrode powder and NH4Cl were uniformly mixed at a molar ratio of 1:6, spread in a reaction vessel with a thickness of 2 cm, and then oxidized and roasted in air with an oxygen partial pressure of 20 kPa. The air flow rate was controlled at 50 mL / min, the heating rate was 5 °C / min, the reaction temperature was 700 °C, and the reaction time was 0.5 h.

[0037] 2. The residue after the reaction was ball-milled, washed with water, and finally filtered and dried to obtain a cobalt tetraoxide catalyst, wherein the ball-milling conditions were: rotation speed 2000 rpm, time 1 hour; and the water-immersion washing conditions were: solid-liquid ratio 50 g / L, time 1 hour. Among them, the impurity ion removal rate was 97.95%, and the yield of the cobalt tetraoxide catalyst was 98.76%.

[0038] Example 3

[0039] This embodiment provides a method for preparing a cobalt trioxide catalyst. Figure 1 , including the following steps:

[0040] 1. The positive electrode powder and (NH4)S2O8 were uniformly mixed at a molar ratio of 1:4, laid in a reaction vessel with a thickness of 0.5 cm, and then oxidized and roasted in air with an oxygen partial pressure of 10 kPa. The air flow rate was controlled at 50 mL / min, the heating rate was 5 °C / min, the reaction temperature was 500 °C, and the reaction time was 0.5 h.

[0041] 2. The residue after the reaction was ball-milled, washed with water, and finally filtered and dried to obtain a cobalt oxide catalyst, wherein the ball-milling conditions were: rotation speed 2000 rpm, time 1 hour; and the water-immersion washing conditions were: solid-liquid ratio 50 g / L, time 1 hour. Among them, the impurity ion removal rate was 99.50%, and the yield of the cobalt oxide catalyst was 99.56%.

[0042] Example 4

[0043] This embodiment provides a method for preparing a cobalt trioxide catalyst. Figure 1 , including the following steps:

[0044] 1. Mix the positive electrode powder with NaHSO4 (1 / 2 (SO4 2- ) were uniformly mixed at a molar ratio of 1:4, laid in a reaction container with a thickness of 0.5 cm, and then oxidized and roasted in air with an oxygen partial pressure of 30 kPa. The air flow rate was controlled to be 50 mL / min, the heating rate was 5°C / min, the reaction temperature was 500°C, and the reaction time was 0.5 h.

[0045] 2. The residue after the reaction was ball-milled, washed with water, and finally filtered and dried to obtain a cobalt oxide catalyst, wherein the ball-milling conditions were: a rotation speed of 2000 rpm, and a time of 1 hour; and the water-immersion washing conditions were: a solid-liquid ratio of 50 g / L, and a time of 1 hour. Among them, the impurity ion removal rate was 96.13%, and the yield of the cobalt oxide catalyst was 99.29%.

[0046] Example 5

[0047] This embodiment provides a method for preparing a cobalt trioxide catalyst. Figure 1 , including the following steps:

[0048] 1. The positive electrode powder and NH4Cl were uniformly mixed at a molar ratio of 1:6, spread in a reaction vessel with a thickness of 2 cm, and then oxidized and calcined in oxygen. The oxygen flow rate was controlled at 50 mL / min, the heating rate was 5°C / min, the reaction temperature was 500°C, and the reaction time was 0.5 h.

[0049] 2. The residue after the reaction was ball-milled, washed with water, and finally filtered and dried to obtain a cobalt oxide catalyst, wherein the ball-milling conditions were: a rotation speed of 2000 rpm, and a time of 1 hour; and the water-immersion washing conditions were: a solid-liquid ratio of 50 g / L, and a time of 1 hour. Among them, the impurity ion removal rate was 99.78%, and the yield of the cobalt oxide catalyst was 99.61%.

[0050] Example 6

[0051] This embodiment provides a method for preparing a cobalt trioxide catalyst. Figure 1 , including the following steps:

[0052] 1. The positive electrode powder and NH4Cl were uniformly mixed at a molar ratio of 1:6, laid in a reaction vessel with a thickness of 0.5 cm, and then oxidized and roasted in air with an oxygen partial pressure of 20 kPa. The air flow rate was controlled at 50 mL / min, the heating rate was 5 °C / min, the reaction temperature was 500 °C, and the reaction time was 2 h.

[0053] 2. The residue after the reaction was ball-milled, washed with water, and finally filtered and dried to obtain a cobalt oxide catalyst, wherein the ball-milling conditions were: rotation speed 2000 rpm, time 1 hour; and the water-immersion washing conditions were: solid-liquid ratio 50 g / L, time 1 hour. Among them, the impurity ion removal rate was 99.56%, and the yield of the cobalt oxide catalyst was 98.23%.

[0054] Comparative Example 1

[0055] The preparation method of this comparative example comprises the following steps:

[0056] 1. The positive electrode powder and NH4Cl were uniformly mixed at a molar ratio of 1:1, laid in a reaction vessel with a thickness of 3 cm, and then oxidized and roasted in air with an oxygen partial pressure of 20 kPa. The air flow rate was controlled at 50 mL / min, the heating rate was 5 °C / min, the reaction temperature was 500 °C, and the reaction time was 0.5 h.

[0057] 2. The residue after the reaction was ball milled, washed with water, and finally filtered and dried to obtain the product. The ball milling conditions were: rotation speed 2000 rpm, time 1 hour; the water washing conditions were: solid-liquid ratio 50 g / L, time 1 hour. Among them, the impurity ion removal rate was 28.71%, and the yield of cobalt tetroxide was 27.24%.

[0058] Since the amount of purification agent used is too low, the impurity ions are not completely removed, and the resulting product is a mixture of lithium cobaltate and cobalt tetroxide.

[0059] Comparative Example 2

[0060] The preparation method of this comparative example comprises the following steps:

[0061] 1. The positive electrode powder and NH4Cl were uniformly mixed at a molar ratio of 1:4, spread in a reaction vessel with a thickness of 0.5 cm, and then calcined in nitrogen. The nitrogen flow rate was controlled at 50 mL / min, the heating rate was 5°C / min, the reaction temperature was 500°C, and the reaction time was 0.5 h.

[0062] 2. The residue after the reaction is ball milled, washed with water, and finally filtered and dried to obtain the product. The ball milling conditions are: rotation speed 2000rpm, time 1h; the water washing conditions are: solid-liquid ratio 50g / L, time 1h. Among them, cobalt ions are removed together with impurity ions.

[0063] Since the oxygen partial pressure of the reaction involved was too low (almost oxygen-free), a large amount of cobalt ions could not effectively participate in the synthesis reaction, and ultimately no effective catalyst was synthesized.

[0064] Comparative Example 3

[0065] The preparation method of this comparative example comprises the following steps:

[0066] 1. The positive electrode powder and NH4HCO3 were uniformly mixed at a molar ratio of 1:4, laid in a reaction vessel with a thickness of 0.5 cm, and then oxidized and roasted in air with an oxygen partial pressure of 20 kPa. The air flow rate was controlled at 50 mL / min, the heating rate was 5 °C / min, the reaction temperature was 500 °C, and the reaction time was 0.5 h.

[0067] 2. The residue after the reaction is ball milled, washed with water, and finally filtered and dried to obtain the product, wherein the ball milling conditions are: rotation speed 2000rpm, time 1h; the water washing conditions are: solid-liquid ratio 50g / L, time 1h. Among them, the removal rate of impurities is less than 5%, and the yield of cobalt trioxide catalyst is less than 5%.

[0068] Since the purification reagents used are not compatible, a large number of impurity ions cannot be effectively removed, and the final residue is still waste lithium cobalt oxide powder.

[0069] Performance Testing

[0070] 1. Taking Example 1 as an example, the morphology of the cathode powder (a, b) and the prepared cobalt oxide catalyst was measured, and the results are as follows: Figure 2 As shown, it can be seen that the positive electrode powder is transformed from an irregular spherical shape to a regular octahedral (spinel) shape after being treated by the preparation method of Example 1, indicating that Example 1 synthesized the classic spinel structure cobalt oxide.

[0071] 2. X-ray diffraction (XRD) was performed on the cobalt tetraoxide catalysts prepared in Examples 1 to 6. Figure 3This is the diffraction pattern of Example 1. It can be seen that under the action of the purification agent, the impurity ions in the positive electrode powder are effectively removed, and finally a high-purity cobalt tetroxide catalyst is obtained.

[0072] 3. The cobalt oxide catalysts prepared in Examples 1 to 6 and the commercial cobalt oxide catalyst were respectively combined with peroxymonosulfate (PMS) to catalytically degrade tetracycline. The catalytic effect was as follows: Figure 4 As shown, it can be seen that the degradation efficiency of the cobalt tetroxide catalysts synthesized in Examples 1 to 6 for tetracycline is comparable to that of the commercial cobalt tetroxide catalyst, indicating that the synthesized cobalt tetroxide catalyst has excellent photocatalytic performance.

[0073] The above description is only a preferred embodiment of the present invention, and therefore cannot be used to limit the scope of the present invention. That is, equivalent changes and modifications made according to the patent scope of the present invention and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A method for preparing a cobalt trioxide catalyst, characterized in that: include: The cathode powder of the waste lithium cobalt oxide battery is mixed with a purification agent and then spread in a reaction device for oxidation roasting to obtain a cobalt tetraoxide catalyst; Wherein, the purification agent is at least one of NaHSO4, KHSO4, (NH4)2SO4, NH4HSO4, NaNH4SO4, NH4NO3, NH4Cl, and NaCl, and the molar ratio of the negative charge of the positive electrode powder to the negative charge of the anion in the purification agent is 1:4-8; The paving thickness of the positive electrode powder and the mixed purification agent is not greater than 2 cm; The temperature of the oxidation roasting is 500-700° C., the time of the oxidation roasting is 0.5-2 hours, and the oxygen partial pressure in the atmosphere of the oxidation roasting is not less than 10 kPa.

2. The method for preparing a cobalt trioxide catalyst according to claim 1, characterized in that: The atmosphere of the oxidative roasting is oxygen or air, and the flow rate of the atmosphere is 50-100 mL / min.

3. The method for preparing a cobalt trioxide catalyst according to claim 1 or 2, characterized in that: Also includes: After the oxidation roasting treatment, the product was ball milled and washed with water.

4. The method for preparing a cobalt trioxide catalyst according to claim 3, characterized in that: The ball milling speed of the ball milling is 2000-3000 rpm, and the ball milling time is 0.5-1 h.

5. The method for preparing a cobalt trioxide catalyst according to claim 3, characterized in that: The solid-liquid ratio of the water immersion washing is 50-100 g / L, and the time of the water immersion washing is 1-2 hours.

6. The method for preparing a cobalt trioxide catalyst according to claim 1, characterized in that: The preparation method of the positive electrode powder is as follows: dismantling waste lithium cobalt oxide batteries to obtain positive electrode sheets, subjecting the positive electrode sheets to pyrolysis treatment to remove a binder, and then separating and collecting the positive electrode sheets.

7. The method for preparing a cobalt trioxide catalyst according to claim 6, characterized in that: The pyrolysis treatment is carried out in an inert atmosphere, the temperature of the pyrolysis treatment is 450-550° C., and the time of the pyrolysis treatment is 1-2 hours.

8. A cobalt tetraoxide catalyst, characterized in that: The cobalt trioxide catalyst is prepared by the method for preparing the cobalt trioxide catalyst according to any one of claims 1 to 7.

9. Use of the cobalt tetroxide catalyst prepared by the method for preparing the cobalt tetroxide catalyst according to any one of claims 1 to 7 as a catalytic material.

10. A photocatalyst, characterized in that: The invention comprises a cobalt tetroxide catalyst prepared by the method for preparing the cobalt tetroxide catalyst according to any one of claims 1 to 7.

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