Disclosure of Invention
Aiming at the problems of high treatment cost, difficult metal state recovery of an aluminum current collector, difficult total leaching of valuable elements and the like in the conventional process for treating the positive pole piece of the waste power lithium battery, the invention aims to provide a total recovery method of the valuable metal elements in the positive pole piece of the waste power lithium battery, which is realized under the assistance of biomass waste materials, wherein Al in the positive pole piece is completely recovered in a metal state product, and L i, Ni, Co and Mn are completely recycled in an ionic state into a solution.
A total recovery method of valuable metal elements in a positive pole piece of a waste power lithium battery comprises the following steps:
step (1): carrying out hydrothermal reaction on a mixed solution of the biomass waste and the dilute acid solution A, and then carrying out solid-liquid separation to obtain a biomass solution S1 and filter residue;
step (2): reacting the filter residue obtained in the step (1) in an alkali liquor, then carrying out solid-liquid separation, and regulating the pH of the solution obtained by separation to 3-5 to obtain a biomass solution S2;
and (3): placing the waste power lithium battery positive pole piece in a biomass solution S2, stirring and stripping, and separating to obtain an aluminum current collector and slurry dispersed with a positive pole material;
and (4) mixing the slurry obtained in the step (3), the biomass solution S1 obtained in the step (1) and the acid liquor B, carrying out reduction leaching, and then carrying out solid-liquid separation to obtain a leachate enriched with L i, Ni, Co and Mn.
According to the technical scheme, the total recovery of Al in the positive plate in the form of a metal simple substance, L i, Ni, Co and Mn in an ionic state into a solution is realized with the assistance of biomass waste materials through the process innovatively.
The invention changes the existing means for stripping Al current collectors such as roasting, organic solvents and the like, and provides a brand new idea and means for stripping Al current collectors in a simple substance form: namely, the biomass solution S2 from the biomass is innovatively obtained through the treatment of the step (1) and the step (2), and the high-efficiency stripping of the Al current collector and the positive electrode material is innovatively carried out in the biomass solution S2, so that the Al can be efficiently recovered in a metal form at low cost in an environment-friendly manner, and the metal leaching of the subsequent positive electrode material and the impurity removal difficulty are facilitated to be reduced. Moreover, the invention further researches and discovers that the positive electrode slurry obtained by stripping and the biomass solution S1 in the step (1) are subjected to reduction leaching of positive electrode components under the synergistic action of the acid liquor B, so that the leaching rate is improved, and the cost is reduced.
The biomass waste adopted by the invention is rich in components such as cellulose, hemicellulose or crude fiber, preferably at least one of straw, corn stalk or corncob, and the granularity of the biomass waste is 200-400 meshes.
Preferably, in the step (1), the dilute acid solution a and the biomass waste are mixed and soaked, then the mixture is placed in a closed reaction kettle for hydrothermal reaction, after the hydrothermal reaction, a discharge valve of the closed reaction kettle is opened, the slurry is sprayed and exploded from the inside of the reaction kettle to a spray explosion bin outside the reaction kettle to obtain slurry after hydrothermal treatment, and the biomass solution S1 and the filter residue are obtained through solid-liquid separation.
Preferably, the dilute acid solution A is a dilute acid solution, preferably dilute sulfuric acid with the volume percentage of 0.25-2%.
Preferably, the liquid-solid ratio of the dilute acid solution A to the biomass waste (on a dry basis) is 1:1 to 1.2: 1.
Preferably, the soaking time is 12-24 h.
Preferably, the temperature of the hydrothermal reaction is preferably 100-.
Preferably, the hydrothermal reaction time is preferably 30 to 60 min.
In the step (2), the alkali in the alkali liquor is at least one of NaOH or KOH.
Further preferably, the concentration of alkali in the alkali liquor is 50-100 g/L.
Preferably, in the step (2), the liquid-solid ratio of the alkali liquor to the filter residue is controlled to be (1:1) - (3: 1).
Preferably, in the step (2), the reaction temperature is preferably 150 to 300 ℃.
Preferably, in the step (2), the reaction time is preferably 30 to 90 min.
According to the invention, the obtained biomass solution S2 is innovatively used as a stripping system of the positive plate, so that Al metal can be stripped, the subsequent leaching of the positive material is facilitated, and the impurity removal difficulty of the subsequent leachate is reduced.
In the step (3), the waste power lithium battery positive pole piece is coarsely crushed to be not less than 120 meshes (not less than 120um), and then placed in a biomass solution S2 to be stirred and peeled; then sieving, wherein oversize products are aluminum current collectors; the undersize is slurry in which the positive electrode material is dispersed.
The waste power lithium battery is a nickel-cobalt-manganese ternary battery. The positive electrode material on the positive plate is a nickel-cobalt-manganese ternary positive electrode material.
Preferably, the temperature of the stripping process is 50-70 ℃.
In step (3), the liquid-solid ratio of the positive electrode sheet to the biomass solution S2 is, for example, (1:1) to (3: 1).
The stirring and stripping time is for example 30-120min,
in the invention, the anode slurry obtained by stripping, the biomass solution S1 and the acid liquor are also innovatively subjected to reduction leaching, so that the efficient recovery of all elements is facilitated.
Preferably, the acid solution B is concentrated sulfuric acid.
Preferably, the concentration of the acid (acid liquor B) in the initial solution of the reduction leaching is 1-3 mol/L.
Preferably, the temperature during the reduction leaching is 75-95 ℃.
The invention discloses a preferable total recovery method of valuable metal elements in a positive pole piece of a waste power lithium battery, which comprises the following steps:
step 1: respectively preparing biomass solutions S1 and S2 by using biomass waste as a raw material;
and a step 2: separating (stripping) the current collector aluminum from the waste positive active material to obtain a product of metal aluminum powder;
and 3, reducing and leaching to ensure that L i, Ni, Co and Mn in the waste positive electrode are totally introduced into the leaching solution to be recovered.
The process 1 comprises the following steps: step 1: adding biomass waste into volume concentration (V)Sulfuric acid/VWater (W)) 0.25-2% of dilute sulfuric acid, preparing slurry with a liquid-solid ratio of 1: 1-1.2: 1, soaking for 12-24h at room temperature, placing the slurry in a closed reaction kettle, preserving heat at 100 ℃ and 120 ℃ for 30-60min, opening a discharge valve of the reaction kettle, enabling the slurry to be sprayed and exploded from the inside of the reaction kettle to a spraying and explosion cabin outside the reaction kettle to obtain slurry after hydrothermal treatment, filtering to obtain a biomass solution S1 and filter residues, step 2, placing the obtained filter residues in a NaOH or KOH solution with the concentration of 50-100 g/L, controlling the liquid-solid ratio in (1:1) - (3:1), then heating the solution system to 150-300 ℃, preserving heat for 30-90 min, and adjusting the pH value of the obtained filtrate to 3-5 by using 5-10 mol/L of sulfuric acid after cooling to obtain the biomass solution S2.
The process 2 comprises the following steps: step 1: coarsely crushing the positive pole piece of the waste power lithium battery to be not less than 120 meshes (not less than 120 um); step 2: controlling the liquid-solid ratio to be (1:1) - (3:1), adding the coarsely crushed anode piece powder of the waste power lithium battery into a biomass solution S2 at 50-70 ℃, and continuously stirring for 30-120min so as to separate an aluminum current collector from an anode active substance, and simultaneously fully dispersing the anode active substance in the solution in a powder form. And 3, pouring the slurry in the previous step into a vibration separation sieve with a sieve with the aperture of 240-400 meshes, separating out the aluminum current collector, and allowing the slurry under the sieve to enter into subsequent reduction leaching.
And 3, the reduction leaching refers to combining the undersize slurry from which the aluminum current collector is separated with a biomass solution S1, adding concentrated sulfuric acid into the combined solution according to the proportion of 1-3 mol/L, heating the solution to 75-95 ℃, and reacting for 4-10 hours, so that the total amount of L i, Ni, Co and Mn in the waste anode enters the leaching solution to be recovered.
Compared with the prior art, the invention has the following advantages:
(1) the biomass waste is adopted, so that the full recovery of valuable metal elements in the positive pole pieces of the waste power lithium batteries is realized, and the treatment cost of the waste positive poles is reduced;
(2) a brand-new stripping idea and means of Al in a metal elementary substance form are provided, namely, a solution S2 obtained by performing combined treatment on biomass waste in the steps (1) and (2) is innovatively adopted as a stripping system to realize the separation of an aluminum current collector and an active substance, and finally, the aluminum in a metal product is recovered;
(3) the positive electrode slurry obtained by the stripping system and the biomass solution S1 are subjected to a reduction leaching process under an acid condition, so that on one hand, the full leaching of valuable components in the waste positive electrode can be promoted, and in addition, the loss of valuable elements in the leachate due to physical entrainment and the like is avoided due to the adoption of the reducing solution, and the characteristic of the invention is also realized;
(4) by adopting the method, the recovery rate of valuable elements such as lithium, nickel, cobalt, manganese and the like in the ternary anode waste can reach nearly 100%, and the aluminum current collector is recovered with low cost in the form of aluminum particles, which is another bright point of the invention.
Example 1, the total recovery of valuable metal elements in the positive electrode plate of waste power lithium batteries with the assistance of biomass waste corncobs.
The corncobs used in this example were crushed to 200 mesh before use. The specific implementation procedure of this embodiment is as follows:
step 1:
step 1: adding corn cob into volume concentration (V)Sulfuric acid/VWater (W)) Preparing slurry with a liquid-solid ratio of 1.2:1 in 2% dilute sulfuric acid, soaking for 12h at room temperature, placing the slurry in a closed reaction kettle, preserving heat at 105 ℃ for 30min, opening a discharge valve of the reaction kettle, enabling the slurry to be sprayed and exploded from the inside of the reaction kettle to a spraying and explosion bin outside the reaction kettle to obtain slurry after hydrothermal treatment, and filtering to obtain a biomass solution S1 and filter residues;
and step 2, placing the obtained filter residue in a NaOH solution with the concentration of 70 g/L, controlling the liquid-solid ratio to be 2.5:1, then heating the solution system to 280 ℃, preserving the heat for 60min, adjusting the pH value of the obtained filtrate to 4 by using 10 mol/L sulfuric acid after cooling, and obtaining the biomass solution S2.
And a step 2: and separating the current collector aluminum from the waste positive active material to obtain the product metal aluminum powder. The process comprises the following steps:
step 1: the method comprises the following steps of (1) roughly crushing a positive pole piece of a waste 523 type power lithium battery to be not less than 120 meshes (not less than 120 um);
step 2: controlling the liquid-solid ratio to be 3:1, adding the coarsely crushed waste power lithium battery positive pole piece powder into a biomass solution S2 at 60 ℃, and continuously stirring for 60min so as to separate an aluminum current collector from a positive active material, and simultaneously fully dispersing the positive active material in the solution in a powder form.
And 3, pouring the slurry in the previous step into a vibration separation sieve with a 300-mesh screen mesh, separating out the aluminum current collector, and carrying out subsequent reduction leaching on the slurry under the sieve.
And 3, reducing and leaching to enable L i, Ni, Co and Mn in the waste positive electrode to enter the leachate to be recovered, firstly, combining the undersize slurry from which the aluminum current collector is separated with a biomass solution S1, then adding concentrated sulfuric acid into the combined solution according to the proportion of 2 mol/L, heating the solution to 90 ℃, and reacting for 6 hours, so that L i, Ni, Co and Mn in the waste positive electrode enter the leachate to be recovered.
As can be seen from the picture of the pole piece after being processed in fig. 2(a), the surface of the pole piece after being processed in this embodiment is very clean, and there is almost no residual active material, which also indicates that the present invention can make all the active material on the pole piece fall off.
Tests show that 99.5% of Al in the waste positive pole piece is recovered in a metal state, and L i, 99.5% and 98.5% of Mn in the positive pole piece enter the leaching solution respectively.
Comparative example 1:
compared with example 1, the difference of the comparative example is that corncob and the anode pole piece are directly placed in a sulfuric acid solution of 3 mol/L to react for 6 hours at 90 ℃, other parameters of the example are that the mass ratio of the corncob to the anode pole piece is equivalent to that of example 1 and is about 1:0.8, the liquid-solid ratio of 2 mol/L sulfuric acid volume and the sum of the corncob and the anode pole piece mass is equivalent to that of example 1 and is about 2:1, and the test shows that:
① Al in the positive pole piece is not recovered in the form of product, but enters the leachate in the form of 100% of impurity, which increases the difficulty of subsequent impurity removal and may cause loss of valuable elements, because aluminum ions are usually removed in the form of aluminum hydroxide, and the aluminum hydroxide is colloid, so that the difficulty of filtration and the loss caused by excessive high content of attached liquid containing valuable elements in slag are inevitable;
② L i, Ni, Co and Mn leaching efficiencies are 96%, 91%, 88% and 86%, respectively, which are obviously lower than those of example 1. high leaching efficiencies of L i, Ni, Co and Mn can be obtained because the corncobs of example 1 are treated by acid-base combination in the process 1, and the components are fully released and have synergistic and accelerating effects.
Comparative example 2:
compared with example 1, the difference of the comparative example is that glucose and the anode pole piece are directly placed in a sulfuric acid solution of 3 mol/L to react for 6 hours at 90 ℃, other parameters of the example are that the mass ratio of the glucose to the anode pole piece is equivalent to that of example 1 and is about 1:0.8, the liquid-solid ratio of 2 mol/L sulfuric acid volume and the sum of the mass of the glucose and the anode pole piece is also equivalent to that of example 1 and is about 2:1, and tests show that:
① Al in the positive pole piece is not recovered in the form of product, but enters the leachate in the form of 100% of impurity, which increases the difficulty of subsequent impurity removal and may cause loss of valuable elements, because aluminum ions are usually removed in the form of aluminum hydroxide, and the aluminum hydroxide is colloid, so that the difficulty of filtration and the loss caused by excessive high content of attached liquid containing valuable elements in slag are inevitable;
② L i, Ni, Co and Mn have leaching efficiencies of 97%, 95%, 92% and 90%, respectively, although the list is significantly lower than example 1 above comparative example 1.
Comparative example 3:
the purpose of this comparative example was to examine whether a single organic acid could completely shed the positive active material on the current collector, and therefore a 5mm size positive plate was selected and placed in step 2 of example 1 for treatment. Organic acids examined are formic acid, acetic acid or malonic acid. After the treatment, it was found that a large amount of the positive electrode material remained on the aluminum current collector. Fig. 2(b) is a photograph of the electrode plate treated with a single formic acid, which shows that the positive active material on the electrode plate is difficult to completely separate due to the single organic acid treatment.
Comparative example 4:
the purpose of this comparative example was to investigate whether a single organic acid could ensure that the aluminium was not leached. This comparative example was conducted in the same manner as example 1 except that the solution S2 in the step 2 was replaced with formic acid. The test result shows that:
① about 8% of the aluminum in the aluminum current collector was dissolved into the leachate and it was found that some positive active material remained on the separated aluminum current collector;
② L i, Ni, Co and Mn were leached with efficiencies of 95%, 90%, 87% and 86%, respectively, which were significantly lower than those of example 1, for reasons related to the residual active species on the aluminum current collector.
As can be seen from the above examples and the corresponding examples, with the assistance of the biomass waste, the present invention has the advantages of almost complete recovery of the aluminum current collector in a metallic state and efficient leaching of valuable elements in the positive electrode plate.