Method for efficiently leaching nickel in wet treatment tailings of waste power battery positive electrode material

Abstract

The invention discloses a method for efficiently leaching nickel in waste power battery positive electrode material wet treatment tailings, which comprises the following steps: collecting the tailings generated by waste power battery positive electrode material wet treatment, and pretreating the tailings to obtain nickel slag; and the mixed bacterial liquid is put into an improved culture medium to form a leaching system, the pH value of the leaching system is adjusted to 1.8-2.2, the temperature of the leaching system is adjusted to 40-45 DEG C, then the nickel slag is added for leaching treatment, and a nickel-rich solution and leaching slag with the nickel content smaller than or equal to 0.1% are obtained through leaching. According to the method, the nickel slag is efficiently leached by using the mixed bacterial liquid compounded by thiobacillus ferrooxidans, leptospirillum ferriphilum, thiobacillus thiooxidans, thiobacillus caldus and temperature-resistant thiobacillus oxydans, nickel can be fully recycled, and the problems of waste of nickel resources and potential environmental pollution of nickel slag treatment are avoided.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of bio-metallurgy, in particular to a method for efficiently leaching nickel in tailings of wet treatment of abandoned power battery positive electrode material. BACKGROUND

[0002] The current wet treatment process of strong acid leaching is usually adopted for recycling of retired power batteries and other nickel-containing waste materials, nickel elements cannot be completely recycled, and about 1% of nickel elements remain in the wet treatment tailings generated in the recycling process, which brings the risk of metal exceeding the standard and belongs to hazardous waste.

[0003] For the wet treatment tailings generated in the recycling of retired power batteries and other materials, the current treatment method is to carry out hazardous waste landfill, which on the one hand wastes the nickel resources in the tailings, and on the other hand causes environmental risk hidden dangers. If the wet recycling (acid leaching) is continued, the cost is high, the efficiency is low, the benefit is small, and even the income is not enough to pay the expenses. SUMMARY

[0004] To solve the above technical problems, the application provides a method for efficiently leaching nickel in tailings of wet treatment of abandoned power battery positive electrode material.

[0005] The technical scheme of the application is: a method for efficiently leaching nickel in tailings of wet treatment of abandoned power battery positive electrode material, comprising the following steps:

[0006] S1, collecting tailings generated in the wet treatment of abandoned power battery positive electrode material, pretreating the tailings to obtain nickel residue;

[0007] S2, putting mixed bacteria liquid into modified culture medium to form a leaching system, adjusting the pH of the leaching system to 1.8-2.2 and the temperature to 40-45 DEG C, then adding the nickel residue for leaching treatment, and leaching to obtain a nickel-rich solution and a leaching residue with a nickel content of less than or equal to 0.1%;

[0008] Wherein, the adding ratio of the nickel residue to the leaching system is 100-200g:1L, and the adding ratio of the mixed bacteria liquid to the modified culture medium is 0.1L:0.9-1L;

[0009] The pretreatment is: putting the tailings into a ball milling system for wet milling and irradiation treatment, the ball-to-material ratio is 3-7:1, the wet milling and irradiation treatment is wet milling for 2-3 minutes after adding an active agent to the ball milling system according to a solid-liquid ratio of 1g:0.05-0.08mL, and microwave irradiation is applied to the ball milling system to dry it to a water content of less than 20%, and the wet milling and irradiation treatment is repeated for several times to complete the pretreatment, wherein the microwave irradiation power is 600-800W.

[0010] Further, the wet treatment of the positive electrode material of the waste power battery is: after the waste power battery is disassembled and sorted, it enters the production line of the wet recovery treatment, and after extraction and recovery, tailings containing about 1% nickel are obtained.

[0011] Description: After the above-mentioned wet recovery treatment, tailings with low nickel content are obtained. At the same time, resource recycling enterprises generally not only collect waste power batteries, but also collect related waste materials from upstream disassembly enterprises. Before entering the wet production line, relevant classification will be carried out. For example, for the wet production of nickel recovery, the enterprise will screen the waste materials with high nickel content from the front end and enter the wet production line for recovery together. Therefore, the tailings mentioned here are not limited to the nickel slag produced by waste power batteries.

[0012] Further, the improved culture medium comprises: (NH4)2SO4, 2.5-3.5 g / L; MgSO4·7H2O, 0.3-0.6 g / L; K2HPO4, 0.3-0.7 g / L; KCl, 0.1-0.3 g / L; and Ca(NO3)2, 0.01-0.05 g / L.

[0013] Description: By optimizing the original culture medium, the improved culture medium can better meet the metabolic needs of Thiobacillus ferroxidans, Leptospirillum ferriphilum, Thiobacillus thiooxidans, Acidithiobacillus caldus and Sulfobacillus, thereby improving the leaching effect of nickel in nickel slag.

[0014] Further, the mixed bacteria solution is composed of Thiobacillus ferroxidans, Leptospirillum ferriphilum, Thiobacillus thiooxidans, Acidithiobacillus caldus and Sulfobacillus. The single bacteria is cultured to the same cell concentration of 1-1.5 x 10 8 CFU / mL, and is compounded according to the unit volume cell concentration ratio: 20±3% of Thiobacillus ferroxidans, 20±3% of Leptospirillum ferriphilum, 20±3% of Thiobacillus thiooxidans, 20±3% of Acidithiobacillus caldus, and 20±3% of Sulfobacillus.

[0015] Description: By using Thiobacillus ferroxidans, Leptospirillum ferriphilum, Thiobacillus thiooxidans, Acidithiobacillus caldus and Sulfobacillus, the biological leaching effect of nickel in nickel slag can be significantly improved, and the nickel content in nickel slag can be reduced to below 0.1%.

[0016] Further, the preservation number of the Acidithiobacillus ferrooxidans is: Acidithiobacillus ferrooxidans, ATCC 23270; the preservation number of the Leptospirillum ferriphilum is: Leptospirillum ferriphilum, AS1.6358; the preservation number of the Thiobacillus thiooxidans is: Thiobacillus thiooxidans, BJMCC 01101; the preservation number of the Acidithiobacillus caldus is: Acidithiobacillus caldus, CGMCC1.15711; and the preservation number of the Sulfobacillus thermotolerans is: Sulfobacillus thermotolerans, DSM17362.

[0017] Description: The strains with the above preservation numbers can provide strong support for the method for efficiently leaching nickel in tailings of wet treatment of positive material of waste power battery, so that the biological leaching effect of nickel in the nickel slag is more stable and efficient.

[0018] Further, the active agent is a mixed solution of a biological surfactant and water, and the mixing ratio of the biological surfactant and water is 0.1-0.5 g: 1 L, and the biological surfactant is composed of rhamnolipid and sophorolipid in a mass ratio of 3:0.5-0.8.

[0019] Description: The combined biological surfactant composed of rhamnolipid and sophorolipid in a certain proportion can reduce the surface tension of the tailings when introduced into the tailings pretreatment, and promote the adhesion of microorganisms during subsequent biological leaching; and combined with microwave radiation treatment, the tailings can be selectively heated, so that the structure of the tailings is loose, which can reduce the surface tension of the tailings in cooperation with the biological surfactant such as rhamnolipid, and on the other hand, the nickel can be more easily leached, thereby improving the biological leaching effect.

[0020] The beneficial effects of the present application are:

[0021] (1) The method for efficiently leaching nickel in tailings of wet treatment of positive material of waste power battery can efficiently leach the nickel slag by using the mixed bacterial solution composed of Acidithiobacillus ferrooxidans, Leptospirillum ferriphilum, Thiobacillus thiooxidans, Acidithiobacillus caldus and Sulfobacillus thermotolerans, so that the nickel can be fully recovered, the waste of nickel resources and the potential environmental pollution problem of nickel slag treatment are avoided, and the treatment cost is lower than that of wet recovery.

[0022] (2) The method for efficiently leaching nickel from tailings of wet treatment of positive material of waste power battery of the application reduces the surface tension of the tailings by introducing the combined biosurfactant composed of rhamnolipid and sophorolipid in a certain proportion into the nickel slag pretreatment, promotes the adhesion of microorganisms during subsequent biological leaching, and combines microwave radiation treatment to improve the effect of biological leaching, so that the nickel content in the leaching residue is reduced to below 0.1%. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a functional relationship diagram of the biological leaching kinetics and single bacterial species (CK, Af, Lf, Tt, Ac, St) and nickel slag.

[0024] Figure 2 is a functional relationship diagram of the kinetics of biological leaching of nickel from sludge of acid leaching of waste lithium batteries and MC type.

[0025] Figure 3 is a functional relationship diagram of the kinetics of biological leaching of nickel from sludge of acid leaching of waste lithium batteries and the ratio of Ac and St in MC.

[0026] Figure 4 is a functional relationship diagram of the biological leaching kinetics and the solid-liquid ratio of nickel in MC45-40AS.

[0027] Figure 5 is a diagram of determining the nickel form in biological leaching sludge using various types of bacteria (single bacteria).

[0028] Figure 6 is a diagram of determining the nickel form in biological leaching sludge using various types of bacteria (different types of MC).

[0029] Figure 7 is a diagram of determining the nickel form in biological leaching sludge using various types of bacteria (MC with different AS contents).

[0030] Figure 8 is a diagram of determining the nickel form in biological leaching sludge using various types of bacteria (different solid-liquid ratios). DETAILED DESCRIPTION

[0031] The application will be described in further detail below in conjunction with specific embodiments to better embody the advantages of the application.

[0032] Example 1: The method for efficiently leaching nickel from tailings of wet treatment of positive material of waste power battery, comprising the following steps:

[0033] S1. After the waste power battery is dismantled and sorted, it enters the wet recycling production line. After extraction and recycling, tailings containing 1% nickel are obtained. The tailings are pretreated to obtain nickel slag. It should be noted that the wet recycling production line refers to the wet production line of the recycling company in the existing technology. The nickel content of the tailings produced is about 1%.

[0034] S2. The mixed bacterial solution is added to the modified culture medium to form a leaching system, and the pH of the leaching system is adjusted to 1.9 and the temperature to 45°C. Then the nickel slag is added for leaching treatment, and the leaching yields a nickel-rich solution and leaching residue with a nickel content ≤0.1%.

[0035] The modified culture medium comprises: (NH4)2SO4, 3.0 g / L; MgSO4·7H2O, 0.5 g / L; K2HPO4, 0.5 g / L; KCl, 0.1 g / L; and Ca(NO3)2, 0.01 g / L; the addition ratio of the nickel slag to the leaching system is 100 g: 1 L, and the addition ratio of the mixed bacterial solution to the modified culture medium is 0.1 L: 0.9 L.

[0036] The mixed bacterial culture consisted of *Thiobacillus ferrooxidans*, *Leptospira* ferrophila, *Thiobacillus thiooxidans*, *Thiobacillus acidophilus*, and *Thiobacillus thiooxidans*; single bacteria were cultured to a uniform cell concentration of 1.5 × 10⁻⁶. 8 The concentration was CFU / mL and formulated according to the following proportions per unit volume of cell concentration: 20% *Acidithiobacillus ferrooxidans*, 20% *Leptospirillum ferriphilum*, 20% *Thiobacillus thiooxidans*, 20% *Leptospirillum ferriphilum*, and 20% *Sulfobacillus thermotolerans*. The preservation number for *Acidithiobacillus ferrooxidans* (Af) is ATCC 23270; the preservation number for *Leptospirillum ferriphilum* (Lf) is AS1.6358; the preservation number for *Thiobacillus thiooxidans* (Tt) is BJMCC 01101; the preservation number for *Acidithiobacillus caldus* (Ac) is CGMCC 1.15711; and the preservation number for *Sulfobacillus thermotolerans* (St) is DSM 17362.

[0037] The pretreatment process is as follows: the tailings are fed into a ball milling system for wet milling and irradiation treatment, with a ball-to-material ratio of 3 to 7:1. The wet milling and irradiation treatment involves adding an active agent to the ball milling system at a solid-liquid ratio of 1 g: 0.07 mL, followed by wet milling for 150 seconds. The ball milling system is then dried by microwave irradiation until the moisture content is <20% (18% in this embodiment). The wet milling and irradiation treatment is repeated three times to complete the pretreatment. The microwave irradiation power is 720 W. The active agent is a mixture of biosurfactant and water, with a mixing ratio of 0.4 g: 1 L. The biosurfactant is composed of rhamnolipid and sophorolipid in a mass ratio of 5:1.

[0038] It should be noted that when the aforementioned *Thiobacillus ferrooxidans* or *Leptospira ferrophila* are cultured alone, an external energy substance, FeSO4·7H2O, at a concentration of 44.7 g / L, is added, and the culture temperature is 30°C.

[0039] When Thiobacillus thiooxidans is cultured alone, sulfur powder (5 g / L) is added as an energy source, and the culture temperature is 30℃.

[0040] When culturing *Thiopyroximate* alone, add sulfur powder (20 g / L) as an energy source and culture at 40°C.

[0041] When thermostable sulfur-oxidizing bacteria were cultured alone, 44.7 g / L of the energy substance FeSO4·7H2O and 0.1 g / L of yeast extract were added, and the culture temperature was 40℃.

[0042] When combining individually cultured *Thiobacillus ferrooxidans*, *Leptospira ferrooxidans*, *Thiobacillus thiooxidans*, *Thiobacillus thiooxidans*, and *Thiobacillus thiooxidans*, a modified culture medium was also used. The composition of the modified culture medium was fine-tuned according to the concentration of the strains. At the same time, the energy substance FeSO4·7H2O, 26.8 g / L and sulfur powder, 5 g / L were added; and yeast extract, 0.02 g / L was also added.

[0043] Since the type and concentration of the added energy substance directly affect the growth rate of the bacteria, by using the above-mentioned limited added energy substances, the required added energy substances can be provided for *Thiobacillus ferrooxidans*, *Leptospira ferrooxidans*, *Thiobacillus thiooxidans*, *Thiobacillus thiooxidans*, and *Thiobacillus thiooxidans*, thereby ensuring the subsequent efficient bioleaching of nickel from nickel slag and improving the efficiency of nickel leaching from nickel slag.

[0044] Example 2: This example differs from Example 1 in that the pH of the leaching system is adjusted to 1.8 and the temperature is 40°C.

[0045] Example 3: This example differs from Example 1 in that the pH of the leaching system is adjusted to 2.2 and the temperature is 42°C.

[0046] Example 4: This example differs from Example 1 in that the modified culture medium includes: (NH4)2SO4, 2.5 g / L; MgSO4·7H2O, 0.3 g / L; K2HPO4, 0.3 g / L; KCl, 0.2 g / L and Ca(NO3)2, 0.03 g / L.

[0047] Example 5: This example differs from Example 1 in that the modified culture medium includes: (NH4)2SO4, 3.5 g / L; MgSO4·7H2O, 0.6 g / L; K2HPO4, 0.7 g / L; KCl, 0.3 g / L and Ca(NO3)2, 0.05 g / L.

[0048] Example 6: This example differs from Example 1 in that the ratio of nickel slag to leaching system is 200g:1L, and the ratio of mixed bacterial solution to modified culture medium is 0.1L:1L.

[0049] Example 7: This example differs from Example 1 in that the single-cell culture reached the same cell concentration of 1.0 × 10⁻⁶. 8 CFU / mL, compounded according to the cell concentration ratio per unit volume: 20% ferrooxidizing thiobacillus, 17% iron-loving Leptospira, 17% thiobacillus sulfooxidizing, 23% thermophilic acid-thiobacillus, and 23% thermostable thiooxidizing thiobacillus.

[0050] Example 8: This example differs from Example 1 in that the single-cell culture reached the same cell concentration of 1.2 × 10⁻⁶. 8 CFU / mL, compounded according to the cell concentration ratio per unit volume: 20% ferrooxidizing thiobacillus, 23% iron-loving Leptospira, 23% thiobacillus sulfooxidizing, 17% thermophilic acid-thiobacillus, and 17% thermostable thiooxidizing thiobacillus.

[0051] Example 9: This example differs from Example 1 in that the pretreatment is as follows: the tailings are fed into a ball milling system for wet milling and irradiation treatment. The wet milling and irradiation treatment involves adding an activator to the ball milling system at a solid-liquid ratio of 1g:0.07mL, wet milling for 2 minutes, and then applying microwave irradiation to the ball milling system to dry it until the moisture content is 18%. The wet milling and irradiation treatment is repeated twice to complete the pretreatment. The ball-to-material ratio is 5:1, and the microwave irradiation power is 600W.

[0052] Example 10: This example differs from Example 1 in that the pretreatment is as follows: the tailings are fed into a ball milling system for wet milling and irradiation treatment. The wet milling and irradiation treatment is performed by adding an activator to the ball milling system at a solid-liquid ratio of 1g:0.08mL, followed by wet milling for 3 minutes, and then applying microwave irradiation to the ball milling system to dry it to a moisture content of 18%. The wet milling and irradiation treatment is repeated five times to complete the pretreatment. The ball-to-material ratio is 5:1, and the microwave irradiation power is 800W.

[0053] Example 11: The difference between this example and Example 1 is that the surfactant is a mixture of biosurfactant and water, and the mixing ratio of biosurfactant to water is 0.1g:1L. The biosurfactant is composed of rhamnolipin and sophorolipid in a mass ratio of 3:0.5.

[0054] Example 12: The difference between this example and Example 1 is that the surfactant is a mixture of biosurfactant and water, and the mixing ratio of biosurfactant to water is 0.5g:1L. The biosurfactant is composed of rhamnolipin and sophorolipid in a mass ratio of 3:0.8.

[0055] Experimental example:

[0056] I. Test Samples:

[0057] Waste power battery cathode materials and other recycled waste are crushed and sorted, and then enter an independent wet recycling production line to leach nickel and cobalt, producing nickel slag and cobalt slag. In this invention, we collect nickel slag for testing. The concentration of nickel in the nickel slag is measured by a handheld X-ray fluorescence spectrometer (XRF), and the measured concentration of nickel in the nickel slag is 0.8214%.

[0058] It should be noted that other recycled waste refers to the waste materials collected by resource recycling companies from upstream dismantling companies. Before entering the hydrometallurgical production line, the waste materials will be sorted. For example, in hydrometallurgical production for nickel recovery, the company will select waste materials with high nickel content from the front end and send them into the hydrometallurgical production line for recycling, based on the technical characteristics of the production line.

[0059] II. Test strains:

[0060] Five typical bioleaching strains were used, including *Thiobacillus ferrooxidans* (Af, ATCC 23270), *Helicobacter ferrooxidans* (Lf, AS1 6358), *Thiobacillus thiooxidans* (Tt, BJMCC 01101), *Thiobacillus castoris* (Ac, CGMCC 1.15711), and *Thiobacillus thermophilus* (St, DSM 17362), as well as their mixed microbial complex (MC). These five bacteria were cultured in a modified medium (pH 1.9).

[0061] The modified culture medium consisted of (NH₄)₂SO₄ (3.0 g / L), KCl (0.1 g / L), K₂HPO₄ (0.5 g / L), MgSO₄·7H₂O (0.5 g / L), and Ca(NO₃)₂ (0.01 g / L). FeSO₄·7H₂O (44.7 g / L) was added as an energy source to Af, Lf, and St. Sulfur powder (5 g / L) was added as an energy source to Tt. Sulfur powder (20 g / L) was added as an energy source to Ac. MC was also cultured in the modified medium (pH = 1.9) with optimized energy sources of sulfur powder and ferrous sulfate heptahydrate added.

[0062] III. Experimental Methods:

[0063] Bioleaching experiments were conducted in 3.0L glass beakers. A 2L leaching system (modified medium, pH 1.9) containing 200mL of bacterial liquid was established in the 3L glass beakers. After pre-culturing, samples were added for bioleaching. The beakers were stirred on a thermostatic magnetic stirrer to fully suspend the waste residue, the suspension position was marked, and water was added daily to replenish the leaching solution. Sampling method for the leaching experiment: During the experiment, 5mL of suspension was taken, filtered, and stored with added nitric acid. Samples were taken at 2 hours, 6 hours, and 12 hours within one day of the start of the experiment, then every other day thereafter, from day 4 to day 12, after which the leaching experiment was stopped. The nickel content in all samples was determined. The thermostatic conditions were set at 30℃, 40℃, and 45℃. The mass content of nickel in the liquid of all samples was determined using inductively coupled plasma mass spectrometry (NexION 2000, PerkinElmer). Specifically, bioleaching experiments on nickel slag were conducted using a single bacterial species and synthetic MC. A detailed list of MC species is provided in Table 1.

[0064] Table 1. Nomenclature of bacterial MC specimens

[0065]

[0066] The effects of bacterial species (control (CK), Af, Lf, Tt, Ac, St, and MC), kinetics (0.08–12.0 days), and solid-liquid ratio (10%, 20%, 30%, 40%, and 50%) on the efficiency of nickel bioleaching from acid-leached waste lithium-ion battery sludge were investigated. To assess the effect of MC type, several MC groups, including MC30-0AS, AS, MC40-25Ac, and MC40-25St, were applied. To assess the ratio of Ac to St in the MC, MC40-40AS, MC45-40AS, MC45-50AS, and MC45-75AS were also applied for nickel bioleaching from nickel slag. To assess the effect of the solid-liquid ratio, 200, 400, 600, 800, and 1000 g of acid-leached sludge were added to a 2 L leaching system.

[0067] IV. Determination of Nickel Speciation

[0068] The modified four-step extraction method recommended by the European Community Reference Bureau (BCR) was used to determine the speciation of nickel, which mainly includes the following four parts.

[0069] 1) Acid-soluble fraction (F1). Add 0.5 g of sample to a 50.0 mL centrifuge tube and add 20.0 mL of 0.11 mol / L CH3COOH for leaching. Shake at 180 rpm for 16 hours at room temperature (25°C). Centrifuge the mixture at 3000 rpm for 20 minutes. The supernatant obtained by filtration is the acid-soluble fraction, which is then tested in a refrigerator at 4°C.

[0070] 2) Reducible fraction (F2). The solid residue obtained after F1 extraction was added to 20.0 ml of 0.5 mol / L NH2OH·HCl, and the mixture was shaken at 180 rpm for 16 hours at room temperature (25°C), followed by centrifugation at 3000 rpm for 20 minutes. The supernatant obtained by filtration was F2, which was then tested at 4°C.

[0071] 3) Oxidizable fraction (F3). Add 5.0 mL of 30% H2O2 (pH = 2.0) to the remaining solid of F2, cover, and keep at room temperature for 1 hour. Then place the mixture in a water bath at 85°C for 1 hour. Remove the lid and continue digestion until 3.0 mL of liquid remains. Then add 5.0 mL of H2O2 to cover it and continue cooking for 1 hour. Remove the lid and cook until the liquid is approximately 1.0 mL. After cooling to room temperature, add 25.0 mL of 1.0 mol / L CH3COONH4, shake at 180 rpm for 16 hours at 25°C, and centrifuge at 3000 rpm for 20 minutes. Filter the supernatant to F3 and test it in a refrigerator at 4°C.

[0072] 4) Residual fraction (F4). The dried F3 residue was digested in a sand bath with a mixed acid to determine the total amount of heavy metals.

[0073] V. Experimental Investigation

[0074] The present invention explores the method for efficiently leaching nickel from waste power battery cathode material wet treatment tailings from the following aspects:

[0075] (1) Relationship between bioleaching kinetics and the function of single bacteria

[0076] Figure 1 The efficiency of nickel bioleaching from sludge of acid-leached spent lithium-ion batteries is shown. Without the addition of any bacteria, the bioleaching rate reached equilibrium at 28.7% in 8 days. The bioleaching rate of *Lf* reached equilibrium at 66.7% in 10 days. The bioleaching rates of the other four bacteria reached equilibrium in 8 days. Specifically, their equilibrium ratios were 75.5% for *Af*, 66.1% for *Ac*, 69.7% for *St*, and 69.9% for *Tt*. This indicates that *Af* exhibited the highest bioleaching rate and the fastest equilibrium compared to other single bacteria.

[0077] (2) Functional relationship between bioleaching kinetics and MC types

[0078] Figure 2 The kinetics of nickel bioleaching from sludge of acid-leached spent lithium batteries are shown for various MC types (including MC30-0AS, AS, MC40-25AS, MC40-25St, MC40-40AS, and MC45-40AS). Figure 2 The bioleaching of nickel shown in the figure indicates that the bioleaching rates of the six types of MCs continuously increased and reached equilibrium at 8 days. The equilibrium values ​​were 80.7% for MC30-0AS, 78.4% for AS, 83.6% for MC40-25AS, 82.4% for MC40-25St, 84.5% for MC40-40AS, and 88.4% for MC45-40AS. This demonstrates that MC45-40AS exhibited the highest nickel bioleaching rate compared to the other five types of MCs and a single bacterial species.

[0079] (3) Functional relationship between bioleaching kinetics and the ratio of Ac and St in MC

[0080] As mentioned above, the optimal MC type for bioleaching nickel from the sludge of acid-leached traction batteries is MC45-40AS. From a practical application perspective, it is best to adjust the detailed ratio of thermophilic bacteria (i.e., Ac and St) in the MC. Figure 3As shown, MCs containing three volumetric concentrations of Ac and St (including MC45-40AS, MC45-50AS, and MC45-75AS) were used for the bioleaching of nickel from sludge. The equilibrium ratios were 88.4% for MC45-40AS, 82.9% for MC45-50AS, and 80.7% for MC45-75AS, indicating that MC45-40AS containing 20% ​​Ac and 20% St is more suitable for nickel bioleaching. Increasing the proportion of Ac or St in MC from 25% to 75% is detrimental to bioleaching.

[0081] (4) Functional relationship between bioleaching kinetics and solid-liquid ratio

[0082] There is an equilibrium between dissolved heavy metal ions in the solution and heavy metals in the solid. Before reaching the threshold, a higher solid-liquid ratio induces a higher concentration of heavy metals to be extracted into the liquid, which favors shifting the equilibrium towards leaching, thereby reducing the amount of heavy metals remaining in the solid and increasing the leaching rate.

[0083] Here, five solid-liquid ratios of MC45-40AS, including 10%, 20%, 30%, 40%, and 50%, are applied to leach nickel. For example... Figure 4 As shown, the equilibrium ratios for leaching nickel from sludge of acid-leached waste lithium batteries are 88.4% at 10% MC45-40AS, 85.2% at 20%, 73.2% at 30%, 70.6% at 40%, and 63.5% at 50%. Therefore, a solid-liquid ratio of 10% is more suitable for bioleaching nickel using MC45-40AS.

[0084] (5) Nickel speciation determination

[0085] BCR analysis was used to determine the nickel speciation in bioleached sludge, such as Figures 5-8 As shown. Typically, nickel exists in five forms: leached, residual, oxidizable, reducible, and acid-soluble. Bioleaching BCR analysis using a single type of bacteria is shown below. Figure 5As shown. Without bacterial addition, the leached and residual portions of nickel in the bioleached sludge were 30.9% and 58.6%, respectively. For nickel bioleaching using a single bacterium, the leaching percentages were 76.6% for Af, 68.3% for Lf, 74.0% for Tt, 69.2% for Ac, and 73.3% for St, significantly higher than the CK group. The residual percentages were 18.4% for Af, 26.8% for Lf, 23.5% for Tt, 22.7% for Ac, and 19.6% for St, significantly lower than the CK group. The fractions for the other three forms ranged from 0.6% to 4.5%, indicating that the majority of nickel in the bioleached sludge was leached and transformed by a single bacterial species. Bioleaching BCR analysis using various types of MCs is shown below. Figure 6 As shown, the bioleaching efficiency was significantly improved. Specifically, the leaching fraction was 84.8% for MC30-0AS, 80.9% for AS, 86.0% for MC40-25As, 87.6% for MC40-25St, 88.1% for MC40-40AS, and 90.3% for MC45-40AS. The residue fraction was 13.3% for MC30-0AS, 15.8% for AS, 11.8% for MC40-25As, 10.6% for MC40-25St, 9.5% for MC40-40AS, and 5.9% for MC45-40AS. The fractions for the other three forms ranged from 0.4% to 1.8%. It was verified that the residue fraction of nickel in sludge bioleaching by adding MC was significantly less than that by adding a single bacterium. The lowest values ​​exhibited by MC45-40AS are also consistent with the highest bioleaching efficiencies of MC45-40AS discussed in the sections above. For example... Figure 7 As shown, the bioleaching BCR analysis of nickel in bioleached sludge was performed using various Ac and St ratios in MC45-40AS. The bioleaching efficiency was significantly improved. Specifically, the leaching fraction was 85.5% for MC45-50AS and 82.9% for MC45-75AS. The residual fraction was 9.7% for MC45-50AS and 11.9% for MC45-75AS. The fractions for the other three forms ranged from 1.8% to 2.4%. Furthermore, Figure 8 BCR analysis of nickel in bioleached sludge is shown. As the solid-liquid ratio of MC45-40AS increased from 10% to 50%, the leached portion of nickel steadily decreased from 90.3% to 65.8%, while the residual portion monotonically increased from 5.9% to 19.3%. In conclusion, these results indicate that MC45-40AS is the optimal adapted microbial consortium for efficient bioleaching of nickel from bioleached sludge.

[0086] (6) Functional relationship between bioleaching kinetics and tailings state

[0087] The nickel slag collected above (nickel concentration of 0.8214%) was designated as Sample 1. Pretreatment was performed on the nickel slag (nickel concentration of 0.8214%). Specifically, the nickel slag was added to a ball milling system, and an activator was added at a solid-liquid ratio of 1:0.07 (by weight). The system was then wet-milled for 150 seconds, and microwave irradiation was applied to the ball milling system until the moisture content reached 18%. This pretreatment was repeated three times. The microwave irradiation power was 720W. The activator was a mixture of biosurfactant and water, with a biosurfactant-to-water mixing ratio of 0.4 g / L. The biosurfactant consisted of rhamnolipin and sophorolipid in a mass ratio of 5:1. The treated nickel slag was then designated as Sample 2. Simultaneously, a control group (CK) was set up, in which the activator in Sample 2 was replaced with an equal amount of water, while all other parameters remained unchanged. This group was designated as Sample 3.

[0088] Bioleaching experiments were conducted on samples 1, 2, and 3 using MC45-40AS with a solid-liquid ratio of 10%. The equilibrium ratios of nickel leached from the sludge were 88.4% for sample 1, 92.7% for sample 2, and 90.2% for sample 3. These results indicate that pretreatment of the nickel slag makes it more suitable to use MC45-40AS for nickel bioleaching.

Claims

1. A method for efficient leaching of nickel from tailings of wet processing of spent power battery cathode material, characterized in that, The method comprises the following steps: S1, collecting tailings generated in wet treatment of positive electrode material of waste power battery, and performing pretreatment on the tailings to obtain nickel slag; S2, putting mixed bacteria liquid into modified medium to form leaching system, adjusting pH of the leaching system to 1.8-2.2 and temperature to 40-45℃, and then adding the nickel slag to perform leaching treatment, and obtaining nickel-rich solution and leaching residue with nickel content ≤0.1%; The adding ratio of the nickel slag to the leaching system is 100-200g:1L, and the adding ratio of the mixed bacteria liquid to the modified medium is 0.1L:0.9-1L. The pretreatment is: putting the tailings into a ball milling system to perform wet milling and irradiation treatment, the ball-material ratio is 3-7:1, the wet milling and irradiation treatment is: adding active agent to the ball milling system according to a solid-liquid ratio of 1g:0.05-0.08mL, wet milling for 2-3min, and applying microwave irradiation to the ball milling system to dry until the water content is less than 20%, and repeating the wet milling and irradiation treatment for several times to complete the pretreatment, wherein the microwave irradiation power is 600-800W.

2. The method for high-efficiency leaching of nickel from the tailings of wet treatment of spent power battery positive electrode material according to claim 1, characterized in that, The wet treatment of the positive electrode material of the waste power battery is: after disassembling and sorting, the waste power battery enters the production line of the wet recovery treatment, and after extraction and recovery, tailings are obtained.

3. The method for high-efficiency leaching of nickel from the tailings of wet treatment of spent power battery positive electrode material according to claim 1, characterized in that, The modified medium comprises (NH4)2SO4, 2.5-3.5g / L; MgSO4·7H2O, 0.3-0.6g / L; K2HPO4, 0.3-0.7g / L; KCl, 0.1-0.3g / L; and Ca(NO3)2, 0.01-0.05g / L.

4. The method for high-efficiency leaching of nickel from the tailings of wet treatment of spent power battery positive electrode material according to claim 1, characterized in that, The mixed bacteria liquid is composed of Thiobacillus ferrooxidans, Leptospirillum ferriphilum, Thiobacillus thiooxidans, Acidithiobacillus caldus and Sulfobacillus thermophilus; single bacteria is cultured to the same cell concentration of 1-1.5*10 8 CFU / mL, and is compounded according to the proportion of unit volume cell concentration: Thiobacillus ferrooxidans 20±3%, Leptospirillum ferriphilum 20±3%, Thiobacillus thiooxidans 20±3%, Acidithiobacillus caldus 20±3%, and Sulfobacillus thermophilus 20±3%.

5. The method for high-efficiency leaching of nickel from the tailings of wet treatment of spent power battery positive electrode material according to claim 4, characterized in that, The preservation number of the Acidithiobacillus ferrooxidans is ATCC23270, the preservation number of the Leptospirillum ferriphilum is AS1.6358, the preservation number of the Thiobacillus thiooxidans is BJMCC 01101, the preservation number of the Acidithiobacillus caldus is CGMCC 1.15711, and the preservation number of the Sulfobacillus thermotolerans is DSM 17362.

6. The method for high-efficiency leaching of nickel from the tailings of wet treatment of spent power battery positive electrode material according to claim 1, characterized in that, The microwave irradiation power is 600-800W; the active agent is a mixed liquid of biological surfactant and water, and the mixing ratio of the biological surfactant to water is 0.1-0.5g:1L, the biological surfactant is composed of rhamnolipid and sophorolipid according to a mass ratio of 3:0.5-0.8.

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