A method for recovering heavy metals from waste

Abstract

The present invention discloses a method for recovering heavy metals from waste. First, the positive electrode material of waste lithium batteries and the co-grinding agent Tween-80 are used for ball milling. During the ball milling process, the main structure of the positive electrode material of waste lithium batteries is damaged, the particle size becomes smaller, the specific surface area increases, the number of reactive sites provided increases, which promotes the dispersion and mass transfer of the positive electrode material of waste lithium batteries in the deep eutectic solvent and improves the leaching efficiency of heavy metals. At the same time, by using Tween-80, it is beneficial to improve the wetting performance of the surface of the positive electrode material of waste lithium batteries and contribute to the subsequent leaching process of heavy metals. The present invention uses L-ascorbic acid and tea polyphenols for compounding. Since tea polyphenols have strong reducing ability, the high-valent metals are first reduced and then leached by L-ascorbic acid, avoiding the problem that the limited reducing ability of L-ascorbic acid makes it difficult to fully reduce metal elements and leads to a decrease in the metal leaching rate.

Description

Technical Field

[0001] The present invention relates to the technical field of heavy metal recovery, and particularly relates to a method for recovering heavy metals from waste. Background Art

[0002] With the continuous expansion of the government's support for new energy policies, the demand and production capacity of lithium-ion batteries (LIBs) have increased rapidly. The technological innovation and transformation and upgrading of China's LIBs industry have continued to develop, the supply capacity of advanced production capacity has been continuously improved, the output of LIBs has increased by more than 130% year-on-year, and the installed capacity of new energy power vehicles and the total export volume of LIBs in the country are 295 GW·h and 342.65 billion yuan respectively. This has accelerated the scrapping speed of power batteries. It is estimated that there will be millions of retired power batteries to be subjected to gradient utilization or scrapping treatment in the next 5 to 8 years; if the scrapped LIBs are not properly treated, there are not only potential hazards such as explosion, flammability, and corrosion, but also possible environmental problems such as the leakage of electrolytes and heavy metals inside the battery, seriously affecting personal safety and threatening the stability of the ecological environment.

[0003] In addition, power vehicle batteries contain important valuable metal resources such as nickel, cobalt, and lithium. China is extremely dependent on imports of such resources, with the proportions reaching as high as 80%, 97%, and 80% respectively. If these key resources are not recovered and utilized in an effective manner, it will greatly increase the waste of such resources in China and even affect the national security of the utilization of such resources. All in all, the recycling of waste LIBs not only conforms to China's low-carbon and green environmental protection policies, but also can alleviate the shortage of key valuable metal resources and lay a foundation for the high-quality and high-level development of China's new energy industry.

[0004] The recycling methods of waste lithium-ion batteries mainly include pyrometallurgy, biohydrometallurgy, and hydrometallurgy. Among these recycling methods, the hydrometallurgy process can more efficiently realize the recovery of metals in waste LIBs, maximize the recovery efficiency, and the purity of the obtained products is also higher, with better economic costs.

[0005] Chinese patent document CN200810178835.0 discloses a method for recovering valuable metals from lithium battery slag containing Co, Ni, and Mn. The lithium battery slag containing lithium metal salts with substantially equal amounts of Co, Ni, and Mn is stirred and leached with a hydrochloric acid solution with a concentration of 250 g / l or more, or stirred and leached with a sulfuric acid solution with a concentration of 200 g / l or more while heating to 65 - 80 °C, or stirred and leached with a solution mixed with a sulfuric acid solution with a concentration of 200 g / l or more and a hydrogen peroxide solution with a concentration of 20 g / l or more. For the leachate, more than 98% of the three metals, Mn, Co, and Ni, are extracted with an acidic extractant solvent to form solutions containing each metal, and valuable metals such as Mn, Co, Ni, and Li are recovered from these solutions and the residual solution containing Li after extraction. This method uses strong acids as leaching agents, which easily corrodes equipment and causes environmental pollution problems. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a method for recovering heavy metals from waste.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions:

[0008] A method for recovering heavy metals from waste, comprising the following steps:

[0009] S1. Mix the waste lithium battery cathode material and the co-grinding agent Tween - 80 evenly and then carry out ball milling to obtain a pretreated cathode material;

[0010] S2. Ultrasonically disperse the pretreated cathode material in a deep eutectic solvent, heat and stir, and filter while it is hot to obtain a filtrate rich in heavy metals, wherein the deep eutectic solvent is composed of L-ascorbic acid, tea polyphenols, and betaine.

[0011] Specifically, in step S1, the waste lithium battery cathode material is selected from at least one of waste lithium iron phosphate cathode material, waste lithium cobalt oxide cathode material, and waste lithium nickel cobalt manganese oxide cathode material.

[0012] Specifically, in step S1, the mass ratio of the waste lithium battery cathode material to Tween - 80 is 10 - 20:1 - 1.5. In some embodiments of the present invention, for example, it can be selected as 10:1, 10:1.5, 12:1, 12:1.5, 15:1, 15:1.5, 18:1.2, 20:1, 20:1.5, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0013] Specifically, in step S1, the ball milling speed is 500 - 1000 r / min. In some embodiments of the present invention, for example, it can be selected as 500 r / min, 600 r / min, 700 r / min, 800 r / min, 900 r / min, 1000 r / min; the ball milling time is 3 - 5 h. In some embodiments of the present invention, for example, it can be selected as 3 h, 4 h, 5 h; however, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0014] Specifically, in step S1, the mass ratio of the grinding balls to the cathode material of the waste lithium battery is 15 - 20:1. In some embodiments of the present invention, for example, it can be selected as 15:1, 16:1, 17:1, 18:1, 19:1, 20:1; however, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0015] Specifically, in step S2, the molar ratio of L - ascorbic acid, tea polyphenols, and betaine in the eutectic solvent is 5 - 8:2 - 3:1. In some embodiments of the present invention, for example, it can be selected as 5:2:1, 5:3:1, 6:2:1, 6:3:1, 8:2:1, 8:3:1, 6:2.5:1; however, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0016] Specifically, in step S2, the solid - liquid ratio of the pretreated cathode material to the eutectic solvent is 60 - 80 g:1 L. In some embodiments of the present invention, for example, it can be selected as 60 g:1 L, 65 g:1 L, 70 g:1 L, 75 g:1 L, 80 g:1 L; however, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0017] Specifically, in step S2, the ultrasonic power is 400 - 1000 W. In some embodiments of the present invention, for example, it can be selected as 400 W, 500 W, 600 W, 700 W, 800 W, 900 W, 1000 W; the ultrasonic frequency is 10 - 80 kHz. For example, it can be selected as 10 kHz, 20 kHz, 30 kHz, 40 kHz, 50 kHz, 60 kHz, 70 kHz, 80 kHz; however, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0018] Specifically, in step S2, the temperature of the heating and stirring is 40 - 80 °C. In some embodiments of the present invention, for example, it can be selected as 40 °C, 50 °C, 60 °C, 70 °C, 80 °C; the heating and stirring time is 3 - 6 h. For example, it can be selected as 3 h, 4 h, 5 h, 6 h; however, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) In the present invention, the spent lithium battery cathode material and the co-grinding agent Tween-80 are first used for ball milling. During the ball milling process, the main structure of the spent lithium battery cathode material is damaged, the particle size becomes smaller, the specific surface area increases, and the number of reactive sites provided increases, which promotes the dispersion and mass transfer of the spent lithium battery cathode material in the deep eutectic solvent and improves the leaching efficiency of heavy metals. At the same time, by using Tween-80, it is beneficial to improve the wetting performance of the surface of the spent lithium battery cathode material, thereby enhancing the dispersion performance of the spent lithium battery cathode material in the deep eutectic solvent and contributing to the subsequent leaching process of heavy metals.

[0021] (2) The deep eutectic solvent used in the present invention is composed of L-ascorbic acid, tea polyphenols and betaine. Considering the limited reducing ability of L-ascorbic acid, L-ascorbic acid and tea polyphenols are used in combination in the present invention. Since tea polyphenols have strong reducing ability, the high-valent metals are reduced and then leached by L-ascorbic acid, avoiding the problem that the leaching rate of metals is reduced due to the limited reducing ability of L-ascorbic acid and the difficulty in fully reducing metal elements.

[0022] (3) In the present invention, by using the co-grinding agent Tween-80 and the spent lithium battery cathode material for blending and ball milling, mechanical activation is first carried out to improve the dispersion and mass transfer performance of the spent lithium battery cathode material in the deep eutectic solvent, and then leaching is carried out using the deep eutectic solvent system. The two are used in combination, greatly improving the leaching rate of heavy metals in the spent lithium battery cathode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is the metal leaching rate effect diagram of the mixed spent lithium battery cathode material;

[0024] Figure 2 is the metal leaching rate effect diagram of the spent lithium nickel cobalt manganese oxide cathode material. DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention will be further described in detail below through specific preferred embodiments, but the present invention is not limited to the following embodiments.

[0026] It should be noted that unless otherwise specified, the chemical reagents involved in the present invention are all purchased through commercial channels.

[0027] Example 1

[0028] A method for recovering heavy metals from waste, characterized by comprising the following steps:

[0029] S1. Mix 5 g of waste lithium iron phosphate cathode material, 5 g of waste lithium cobalt oxide cathode material, and 1 g of co-grinding agent Tween-80 evenly, then carry out ball milling at a ball milling speed of 800 r / min for 4 h. The ratio of the mass of the grinding balls to the total mass of the waste lithium battery cathode material is 15:1. After the ball milling is completed, a pretreated cathode material is obtained.

[0030] S2. Ultrasonically disperse 10 g of the pretreated cathode material in 100 mL of a deep eutectic solvent at an ultrasonic power of 600 W and an ultrasonic frequency of 40 kHz, stir at 60 °C for 4 h, and filter while it is hot to obtain a filtrate rich in heavy metals. The deep eutectic solvent is composed of L-ascorbic acid, tea polyphenols, and betaine, and the molar ratio of L-ascorbic acid, tea polyphenols, and betaine is 6:2:1.

[0031] Example 2

[0032] A method for recovering heavy metals from waste, characterized by including the following steps:

[0033] S1. Mix 5 g of waste lithium iron phosphate cathode material, 5 g of waste lithium cobalt oxide cathode material, and 1.2 g of co-grinding agent Tween-80 evenly, then carry out ball milling at a ball milling speed of 500 r / min for 5 h. The ratio of the mass of the grinding balls to the total mass of the waste lithium battery cathode material is 18:1. After the ball milling is completed, a pretreated cathode material is obtained.

[0034] S2. Ultrasonically disperse 10 g of the pretreated cathode material in 100 mL of a deep eutectic solvent at an ultrasonic power of 800 W and an ultrasonic frequency of 60 kHz, stir at 40 °C for 6 h, and filter while it is hot to obtain a filtrate rich in heavy metals. The deep eutectic solvent is composed of L-ascorbic acid, tea polyphenols, and betaine, and the molar ratio of L-ascorbic acid, tea polyphenols, and betaine is 5:3:1.

[0035] Example 3

[0036] A method for recovering heavy metals from waste, characterized by including the following steps:

[0037] S1. Mix 15 g of waste lithium nickel cobalt manganese oxide cathode material and 1.5 g of co-grinding agent Tween-80 evenly, then carry out ball milling at a ball milling speed of 500 r / min for 5 h. The ratio of the mass of the grinding balls to the mass of the waste lithium battery cathode material is 20:1. After the ball milling is completed, a pretreated cathode material is obtained.

[0038] S2. Ultrasonically disperse 15 g of the pretreated cathode material in 100 mL of the deep eutectic solvent at an ultrasonic power of 1000 W and an ultrasonic frequency of 20 kHz, stir at 80 °C for 3 h, and filter while it is hot to obtain a filtrate rich in heavy metals. The deep eutectic solvent is composed of L-ascorbic acid, tea polyphenols, and betaine, and the molar ratio of L-ascorbic acid, tea polyphenols, and betaine is 8:2:1.

[0039] Example 4

[0040] A method for recovering heavy metals from waste, characterized by comprising the following steps:

[0041] S1. Mix 15 g of the waste lithium nickel cobalt manganese oxide cathode material and 1.0 g of the co-grinding agent Tween-80 evenly and then carry out ball milling at a ball milling speed of 800 r / min for 5 h. The ratio of the mass of the grinding balls to the mass of the waste lithium battery cathode material is 20:1. After the ball milling is completed, a pretreated cathode material is obtained;

[0042] S2. Ultrasonically disperse 15 g of the pretreated cathode material in 100 mL of the deep eutectic solvent at an ultrasonic power of 1000 W and an ultrasonic frequency of 80 kHz, stir at 60 °C for 4 h, and filter while it is hot to obtain a filtrate rich in heavy metals. The deep eutectic solvent is composed of L-ascorbic acid, tea polyphenols, and betaine, and the molar ratio of L-ascorbic acid, tea polyphenols, and betaine is 7:3:1.

[0043] Comparative Example 1

[0044] A method for recovering heavy metals from waste, characterized by comprising the following steps:

[0045] S1. Mix 5 g of the waste lithium iron phosphate cathode material and 5 g of the waste lithium cobalt oxide cathode material evenly and then carry out ball milling at a ball milling speed of 800 r / min for 4 h. The ratio of the mass of the grinding balls to the total mass of the waste lithium battery cathode material is 15:1. After the ball milling is completed, a pretreated cathode material is obtained;

[0046] S2. Ultrasonically disperse 10 g of the pretreated cathode material in 100 mL of the deep eutectic solvent at an ultrasonic power of 600 W and an ultrasonic frequency of 40 kHz, stir at 60 °C for 4 h, and filter while it is hot to obtain a filtrate rich in heavy metals. The deep eutectic solvent is composed of L-ascorbic acid, tea polyphenols, and betaine, and the molar ratio of L-ascorbic acid, tea polyphenols, and betaine is 5:2:1.

[0047] Comparative Example 2

[0048] A method for recovering heavy metals from waste, characterized by comprising the following steps:

[0049] S1. Mix 5 g of waste lithium iron phosphate cathode material, 5 g of waste lithium cobalt oxide cathode material, and 1 g of co-grinding agent sodium chloride evenly, then carry out ball milling at a ball milling speed of 800 r / min for 4 h. The ratio of the mass of the grinding balls to the total mass of the waste lithium battery cathode material is 15:1. After the ball milling is completed, a pretreated cathode material is obtained.

[0050] S2. Ultrasonically disperse 10 g of the pretreated cathode material in 100 mL of a deep eutectic solvent at an ultrasonic power of 600 W and an ultrasonic frequency of 40 kHz, stir at 60 °C for 4 h, and filter while it is hot to obtain a filtrate rich in heavy metals. The deep eutectic solvent is composed of L-ascorbic acid, tea polyphenols, and betaine, and the molar ratio of L-ascorbic acid, tea polyphenols, and betaine is 5:2:1.

[0051] Comparative Example 3

[0052] A method for recovering heavy metals from waste, characterized by comprising the following steps:

[0053] S1. Mix 5 g of waste lithium iron phosphate cathode material, 5 g of waste lithium cobalt oxide cathode material, and 1 g of co-grinding agent Tween-80 evenly, then carry out ball milling at a ball milling speed of 800 r / min for 4 h. The ratio of the mass of the grinding balls to the total mass of the waste lithium battery cathode material is 15:1. After the ball milling is completed, a pretreated cathode material is obtained.

[0054] S2. Ultrasonically disperse 10 g of the pretreated cathode material in 100 mL of a deep eutectic solvent at an ultrasonic power of 600 W and an ultrasonic frequency of 40 kHz, stir at 60 °C for 4 h, and filter while it is hot to obtain a filtrate rich in heavy metals. The deep eutectic solvent is composed of L-ascorbic acid and betaine, and the molar ratio of L-ascorbic acid and betaine is 5:1.

[0055] Perform metal ion leaching rate tests on the filtrates obtained in Examples 1-2 and Comparative Examples 1-3. The specific steps are as follows: Weigh 5 g of waste lithium iron phosphate cathode material and 5 g of waste lithium cobalt oxide cathode material, add 100 mL of aqua regia to dissolve to obtain a leaching solution, then dilute the leaching solution by 100 times, measure the concentration of each metal ion in the leaching solution using inductively coupled plasma optical emission spectrometry (ICP-OES), denoted as C0. Dilute the filtrates obtained in Examples 1-2 and Comparative Examples 1-3 by 100 times respectively, and then measure the concentration of each metal ion in the filtrate using ICP-OES, denoted as C1. Calculate the leaching rate of the metal n = C1 / C0. The obtained experimental results are as Figure 1 shown, from Figure 1It can be seen that by using the method of the present invention, the leaching rates of Li and Co reach over 99%, the leaching rate of Fe reaches over 98%. In Comparative Example 1, no co-grinding agent was added during ball milling. In Comparative Example 2, the co-grinding agent was replaced with sodium chloride during ball milling. In Comparative Example 3, tea polyphenols were not added to the eutectic solvent. The leaching rates of metals in Comparative Examples 1-3 are not as good as those in the examples of the present invention.

[0056] The filtrates obtained in Examples 3-4 were subjected to metal ion leaching rate tests. The specific steps are as follows: Weigh 15 g of waste lithium nickel cobalt manganese oxide cathode material, add 100 mL of aqua regia to dissolve it to obtain a leaching solution, then dilute the leaching solution 100 times, and measure the concentrations of various metal ions in the leaching solution using inductively coupled plasma optical emission spectrometry (ICP-OES), denoted as C0. Dilute the filtrates obtained in Examples 3-4 100 times respectively, and then measure the concentrations of various metal ions in the filtrates using ICP-OES, denoted as C1. Calculate the leaching rate of the metal n = C1 / C0. The obtained experimental results are as Figure 2 shown. It can be seen from Figure 2 that by using the method of the present invention, there are better leaching rates for metals Li, Ni, Co, and Mn; at the same time, it can be seen from Figure 1-2 that the method of the present invention has good metal leaching rates for both single waste lithium battery cathode materials and mixed waste lithium battery cathode materials.

[0057] Finally, it should be noted that the above examples do not limit the present invention in any form. For those skilled in the art, based on the present invention, some modifications and improvements can be made. Therefore, any modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection required by the present invention.

Claims

1. A method for recovering heavy metals from waste, characterized in that, It includes the following steps: S1. Mix the waste lithium battery cathode material and the co-grinding agent Tween-80 evenly and then carry out ball milling to obtain a pretreated cathode material; S2. Ultrasonically disperse the pretreated cathode material in the deep eutectic solvent, heat and stir, and filter while it is hot to obtain a filtrate rich in heavy metals, wherein the deep eutectic solvent is composed of L-ascorbic acid, tea polyphenols and betaine; Among them, in step S1, the mass ratio of the waste lithium battery cathode material to Tween-80 is 10-20:1-1.5; In step S2, the molar ratio of L-ascorbic acid, tea polyphenols and betaine in the deep eutectic solvent is 5-8:2-3:1; In step S2, the solid-liquid ratio of the pretreated cathode material to the deep eutectic solvent is 60-80 g:1 L.

2. The method for recovering heavy metals from waste according to claim 1, characterized in that, In step S1, the waste lithium battery cathode material is selected from at least one of waste lithium iron phosphate cathode material, waste lithium cobalt oxide cathode material, and waste lithium nickel cobalt manganese oxide cathode material.

3. The method for recovering heavy metals from waste according to claim 1, characterized in that, In step S1, the ball milling speed is 500-1000 r / min, and the ball milling time is 3-5 h.

4. The method for recovering heavy metals from waste according to claim 1, characterized in that, In step S1, the mass ratio of the grinding ball quality to the waste lithium battery cathode material is 15-20:

1.

5. The method for recovering heavy metals from waste according to claim 1, wherein In step S2, the ultrasonic power is 400-1000 W, and the ultrasonic frequency is 10-80 kHz.

6. The method for recovering heavy metals from waste according to claim 1, characterized in that, In step S2, the temperature of heating and stirring is 40-80 °C, and the time of heating and stirring is 3-6 h.

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