A method for removing impurities from industrial-grade lithium carbonate based on vegetable tanned leather scraps

Abstract

The invention discloses a method for removing impurities in industrial-grade lithium carbonate based on vegetable-tanned leather scraps, relating to the technical field of lithium carbonate purification, including: leather making, soaking leather scraps in a vegetable tanning agent for treatment, then washing and drying to obtain vegetable-tanned leather; preparing vegetable-tanned leather filter cloth; sizing, dispersing industrial-grade lithium carbonate in water to obtain a slurry; hydrogenation, introducing carbon dioxide into the slurry to obtain a hydrogenated feed liquid; filtering, filtering the hydrogenated feed liquid using a vegetable-tanned leather filter cloth; thermal decomposition, heating the lithium bicarbonate solution; solid-liquid separation, obtaining a mother liquor and battery-grade wet lithium carbonate; powdering, crushing the battery-grade wet lithium carbonate after drying to obtain battery-grade lithium carbonate dry powder. The present invention prepares vegetable-tanned leather by reacting leather scraps with glutaraldehyde and tannin, and then making a vegetable-tanned leather filter cloth for the impurity removal process of industrial-grade lithium carbonate, which can effectively filter and remove impurities, has good economy, and has high impurity removal efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of lithium carbonate purification, and in particular to a method for removing impurities in industrial-grade lithium carbonate based on vegetable tanned leather scraps. Background Art

[0002] The existing method of using industrial-grade lithium carbonate to prepare battery-grade lithium carbonate usually requires the filtrate and filter residue to be treated for the removal of metal ion impurities such as calcium and magnesium, as well as the enrichment of lithium, which makes the operation steps cumbersome and consumes a lot of time; or it is necessary to add a large amount of reagents such as sodium carbonate and sodium hydroxide to the system, which has problems such as complicated waste liquid treatment and large reagent consumption; or it is necessary to use resins, ion exchange membranes, extraction technology and other means, which not only has a lot of post-processing waste, but is also prone to the adsorption of lithium salts and clogging of filter membranes, requiring frequent replacement of consumables, resulting in high production costs. The above difficulties have caused the existing method of using industrial-grade lithium carbonate to prepare battery-grade lithium carbonate to have the problems of complex operation and high cost. Summary of the Invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art. The present invention provides a method for removing impurities in industrial-grade lithium carbonate based on vegetable-tanned leather scraps. The method comprises the following steps: preparing vegetable-tanned leather by reacting the leather scraps with glutaraldehyde and tannin; and preparing the vegetable-tanned leather filter cloth. The vegetable-tanned leather filter cloth is used in the impurity removal process of industrial-grade lithium carbonate. The impurities can be effectively filtered out, and the method has simple operation, good economy and high impurity removal efficiency.

[0004] The present invention provides a method for removing impurities in industrial-grade lithium carbonate based on vegetable tanned leather scraps, comprising the following steps:

[0005] Leather making, wherein the cleaned leather scraps are soaked in a vegetable tanning agent for treatment, followed by washing and drying to obtain vegetable tanned leather; the vegetable tanning agent comprises glutaraldehyde and tannin;

[0006] preparing a filter cloth by thinning, cutting and assembling the vegetable tanned leather to obtain a vegetable tanned leather filter cloth;

[0007] Slurry preparation: dispersing industrial-grade lithium carbonate in water to obtain a slurry;

[0008] hydrogenation, introducing carbon dioxide into the slurry for hydrogenation treatment to obtain a hydrogenated feed liquid;

[0009] Filtering, using the vegetable tanned leather filter cloth to filter the hydrogenated feed liquid, wherein insoluble impurities are obtained in the solid phase and a lithium bicarbonate solution is obtained in the liquid phase;

[0010] Thermal decomposition, heating the lithium bicarbonate solution to obtain a solid-liquid mixture;

[0011] solid-liquid separation, filtering the solid-liquid mixture to obtain mother liquor and battery-grade wet lithium carbonate;

[0012] Powdering: drying the battery-grade wet lithium carbonate and then crushing it to obtain battery-grade lithium carbonate dry powder.

[0013] Specifically, the mass ratio of the leather scraps to the tannin is in the range of 1.5 to 2.5:1, the concentration of the glutaraldehyde is in the range of 15 to 25 g / L, and the pH value of the vegetable tanning agent is in the range of 5.5 to 6.5.

[0014] Specifically, the step of soaking the washed leather scraps in a vegetable tanning agent comprises:

[0015] Soak the cleaned leather scraps in vegetable tanning agent, first treat at 20-30℃ for 0.5-1.5h, then heat to 45-55℃ for 2.5-3.5h.

[0016] Specifically, the vegetable tanned leather filter cloth is composed of three layers of the vegetable tanned leather, and the thickness of each layer of the vegetable tanned leather is in the range of 0.8 to 1.2 mm.

[0017] Specifically, in the slurry, the mass ratio of the industrial-grade lithium carbonate to water is in the range of 1:20 to 25.

[0018] Specifically, in the hydrogenation step, the purity of the carbon dioxide is greater than 35%.

[0019] Specifically, in the filtration step, the vegetable tanned leather filter cloth is used to filter the hydrogenated feed liquid under normal pressure.

[0020] Specifically, in the thermal decomposition step, the temperature range of the heating treatment is 80-100°C.

[0021] Specifically, the mother liquor is recycled to the slurry preparation step.

[0022] Specifically, in the industrial-grade lithium carbonate, lithium carbonate is less than 98.5 wt %, calcium is greater than 500 ppm, and magnesium is greater than 1000 ppm.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The discarded leather scraps in the tanning industry are used to make vegetable tanned leather filter cloth, which realizes the recycling of resources. In addition, the vegetable tanned leather filter cloth is simple to make, and the required raw materials are easy to obtain, cheap and can be reused, which can effectively reduce costs.

[0025] (2) Vegetable tanned leather is made by reacting leather scraps with tannin under the condition of glutaraldehyde as a cross-linking agent. The cross-linking effect of glutaraldehyde solidifies the tannin on the collagen fibers of the leather scraps in the form of covalent bonds, so that the tannin will not be eluted by water, organic solvents, etc., and the molecular structure of tannin contains multiple ortho-phenolic hydroxyl groups that can react with metal ions. Therefore, the vegetable tanned leather filter cloth can efficiently and massively adsorb metal ion impurities such as calcium and magnesium, thereby achieving good impurity removal effect and low cost.

[0026] (3) It has a high degree of compatibility with the existing process of preparing battery-grade lithium carbonate using industrial-grade lithium carbonate and is simple to operate.

[0027] In summary, the present invention prepares vegetable tanned leather by reacting leather scraps with glutaraldehyde and tannin, and then makes vegetable tanned leather filter cloth, which is used in the impurity removal process of industrial-grade lithium carbonate. The impurities can be effectively filtered out, the operation is simple, the economy is good, and the impurity removal efficiency is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 It is a flow chart of a method for removing impurities from industrial-grade lithium carbonate based on vegetable tanned leather scraps in an embodiment of the present invention. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0031] The present invention provides a method for removing impurities from industrial-grade lithium carbonate based on vegetable tanned leather scraps. Figure 1 A schematic flow chart of a method for removing impurities from industrial-grade lithium carbonate based on vegetable-tanned leather scraps according to an embodiment of the present invention is shown, comprising the following steps:

[0032] S1, leather making;

[0033] The washed leather scraps are soaked in a vegetable tanning agent for treatment, and then washed and dried to obtain vegetable tanned leather;

[0034] Typically, in order to ensure that the vegetable tanning agent is evenly infiltrated into the leather scraps, sufficient stirring is required. Preferably, a rotary drum is used for auxiliary tanning. During the tanning process, the vegetable tanning agent penetrates into the leather scraps and combines with the collagen fibers, transforming the leather scraps into the target product.

[0035] Specifically, the vegetable tanning agent includes glutaraldehyde and tannin. Leather scraps contain a large amount of collagen fibers, and the molecular structure of tannin has multiple phenolic hydroxyl groups, which can be combined with the collagen fibers of leather scraps through hydrogen bonds and hydrophobic bonds. Then, through the cross-linking effect of glutaraldehyde, the tannin can be solidified on the collagen fibers of leather scraps in the form of covalent bonds, which is firm and reliable, so that the tannin will not be eluted by water, organic solvents, etc.; at the same time, the molecular structure of tannin has multiple ortho-phenolic hydroxyl groups, which can be complexed with metal ions such as calcium and magnesium with two coordinating atoms, which is the basis for the subsequent adsorption and removal of impurities in industrial-grade lithium carbonate.

[0036] Furthermore, the area of ​​a single piece of leather scrap is ≥150cm 2 , which is convenient for subsequent processing.

[0037] In some specific embodiments, the mass ratio of the leather scraps and the tannin is in the range of 1.5 to 2.5:1, the concentration of the glutaraldehyde is in the range of 15 to 25 g / L, and the pH value of the vegetable tanning agent is in the range of 5.5 to 6.5, which can ensure that the obtained vegetable tanned leather is firmly bound with sufficient tannins. At the same time, the appropriate pH value environment is conducive to shortening the reaction time and improving the cross-linking effect. Preferably, the mass ratio of the leather scraps and the tannin is 2:1, the concentration of the glutaraldehyde is 20 g / L, and the pH value of the vegetable tanning agent is 6, which has high reaction efficiency and good cross-linking effect.

[0038] In some specific embodiments, the soaking of the cleaned leather scraps in a vegetable tanning agent comprises: soaking the cleaned leather scraps in a vegetable tanning agent, first treating at 20-30°C for 0.5-1.5h, and then heating to 45-55°C for 2.5-3.5h. The first treatment at about 25°C is conducive to cross-linking glutaraldehyde with the collagen fibers of the leather scraps, and to combining tannins with the collagen fibers of the leather scraps through hydrogen bonds and hydrophobic bonds, thereby reducing the occurrence of side reactions; and then heating to about 50°C for treatment is conducive to accelerating the reaction, fully cross-linking glutaraldehyde and tannins, and solidifying the tannins on the collagen fibers of the leather scraps in the form of covalent bonds, which is firm and reliable.

[0039] Preferably, the washed leather scraps are soaked in a vegetable tanning agent, first treated at 25° C. for 1 hour, and then heated to 50° C. for 3 hours.

[0040] S2, preparing filter cloth;

[0041] thinning, cutting and assembling the vegetable tanned leather to obtain a vegetable tanned leather filter cloth;

[0042] According to the size of the required filter cloth area, several thinned and cut vegetable tanned leathers are spliced ​​together and fixed with glue; and the spliced ​​parts are thinned to ensure that the vegetable tanned leather filter cloth is flat as a whole.

[0043] In some specific embodiments, the vegetable tanned leather filter cloth is composed of three layers of the vegetable tanned leather, and the thickness of each layer of the vegetable tanned leather ranges from 0.8 to 1.2 mm, so that the vegetable tanned leather filter cloth has good filtering ability and sufficient adsorption area, and is strong and durable; preferably, the thickness of each layer of the vegetable tanned leather is 1 mm, which is easy to process and cost-effective.

[0044] S3, slurry preparation;

[0045] Dispersing industrial grade lithium carbonate in water to obtain a slurry;

[0046] In the industrial-grade lithium carbonate, lithium carbonate is less than 98.5wt%, calcium is greater than 500pm, and magnesium is greater than 1000ppm; the formed slurry mainly contains solid lithium carbonate, insoluble impurities, calcium ions, magnesium ions, water, and the like.

[0047] In some specific embodiments, industrial-grade lithium carbonate is dispersed in water using a stirring paddle, which is simple to operate and cost-effective. In the slurry, the mass ratio of the industrial-grade lithium carbonate to water is in the range of 1:20 to 25, which allows the industrial-grade lithium carbonate to be thoroughly dispersed, facilitates subsequent hydrogenation, and fully dissolves metal ion impurities such as calcium and magnesium, which is beneficial for the subsequent removal of impurities. Preferably, the mass ratio of the industrial-grade lithium carbonate to water is 1:20, which saves water on the one hand and improves the efficiency of subsequent hydrogenation on the other.

[0048] S4, hydrogenation;

[0049] introducing carbon dioxide into the slurry for hydrogenation to obtain a hydrogenated feed liquid;

[0050] The solid lithium carbonate in the slurry is converted into water-soluble lithium bicarbonate, which facilitates subsequent filtration to remove insoluble impurities.

[0051] In some specific embodiments, the carbon dioxide has a purity greater than 35%. Pure carbon dioxide is not required, which can improve carbon dioxide utilization and reduce production costs. Specifically, the carbon dioxide can be diluted with air to a purity greater than 35%. Furthermore, dilution with air can reduce the pressure requirement for use, making the carbon dioxide safer and more reliable.

[0052] S5, filtering;

[0053] The hydrogenated feed liquid is filtered using the vegetable tanned leather filter cloth, wherein insoluble impurities are obtained in the solid phase and a lithium bicarbonate solution is obtained in the liquid phase;

[0054] Insoluble impurities cannot pass through the vegetable tanned leather filter cloth, while metal ion impurities such as calcium and magnesium will be adsorbed in large quantities by the vegetable tanned leather filter cloth, thereby obtaining a highly pure lithium bicarbonate solution.

[0055] Specifically, the vegetable tanned leather filter cloth is used to filter the hydrogenated liquid at normal pressure, so that the hydrogenated liquid slowly passes through the vegetable tanned leather filter cloth, so that metal ion impurities such as calcium and magnesium are fully adsorbed by the vegetable tanned leather filter cloth, which is beneficial to improving the purity of the obtained lithium bicarbonate solution.

[0056] In some specific embodiments, each square decimeter of vegetable tanned leather filter cloth can process 5 to 10 L of hydrogenated liquid, with a large processing capacity, high impurity removal efficiency, and good cost performance.

[0057] Specifically, after use, the vegetable-tanned leather filter cloth can be easily eluted with a dilute acid solution to remove adsorbed metal ion impurities such as calcium and magnesium, allowing the vegetable-tanned leather filter cloth to be regenerated and reused. Furthermore, the vegetable-tanned leather filter cloth can maintain good adsorption performance after at least 10 regenerations, resulting in high economic efficiency and effectively reducing usage costs. Optionally, the dilute acid solution is a 0.1 mol / L HCl solution, 0.1 mol / L H2SO4, or 0.1 mol / L HNO3 solution.

[0058] S6, thermal decomposition;

[0059] heating the lithium bicarbonate solution to obtain a solid-liquid mixture;

[0060] The lithium bicarbonate in the solution will decompose when heated to produce lithium carbonate, carbon dioxide and water, and the regenerated lithium carbonate will crystallize out of the solution.

[0061] In some specific embodiments, the temperature range of the heat treatment is 80-100°C, which is conducive to accelerating the thermal decomposition rate of lithium bicarbonate and shortening the thermal decomposition time; preferably, the temperature of the heat treatment is 100°C, and the crystallization efficiency of lithium carbonate is very high.

[0062] S7, solid-liquid separation;

[0063] filtering the solid-liquid mixture to obtain a mother liquor and battery-grade wet lithium carbonate;

[0064] Simple filtration can separate the lithium carbonate from the solid-liquid mixture to obtain battery-grade wet lithium carbonate; the remaining mother liquor can be reused in the slurry preparation step to save water resources.

[0065] S8, flour making;

[0066] drying the battery-grade wet lithium carbonate and then crushing it to obtain battery-grade lithium carbonate dry powder;

[0067] Testing of battery-grade lithium carbonate dry powder showed that the content of lithium carbonate was >99.5wt%, calcium was <50ppm, and magnesium was <80ppm. It can be seen that the purity of lithium carbonate has been effectively improved, and the content of calcium and magnesium has been significantly reduced. The contents of other impurities also met the requirements, with sulfate <800ppm, chlorine <30ppm, sodium <250ppm, and potassium <10ppm.

[0068] In the present invention, leather scraps discarded in the leather industry are utilized to make vegetable tanned leather filter cloth, thus realizing resource recycling. In addition, the vegetable tanned leather filter cloth is simple to manufacture, and the required raw materials are readily available, cheap and reusable, thereby effectively reducing costs. Vegetable tanned leather is prepared by reacting leather scraps with tannin under the condition of glutaraldehyde as a cross-linking agent. The cross-linking effect of glutaraldehyde solidifies the tannin on the collagen fibers of the leather scraps in the form of covalent bonds, so that the tannin will not be eluted by water, organic solvents, etc., and the molecular structure of the tannin contains a plurality of ortho-phenolic hydroxyl groups that can undergo complexation reactions with metal ions, so that the vegetable tanned leather filter cloth can efficiently and in large quantities adsorb metal ion impurities such as calcium and magnesium, has a good effect in removing impurities, and has a low cost of use. The vegetable tanned leather filter cloth can replace traditional decalcifying agents, adsorption columns, etc., is more convenient to use, and has a lower cost of use. It has a high degree of compatibility with the existing process of preparing battery-grade lithium carbonate using industrial-grade lithium carbonate and is simple to operate. The present invention prepares vegetable tanned leather by reacting leather scraps with glutaraldehyde and tannin, and then prepares the vegetable tanned leather filter cloth. The vegetable tanned leather filter cloth is used in the impurity removal process of industrial-grade lithium carbonate, can effectively filter and remove impurities, is simple to operate, has good economy and high impurity removal efficiency.

[0069] Example 1

[0070] (1) The cleaned leather scraps are soaked in a vegetable tanning agent for treatment, first at 25°C for 1 hour, then heated to 50°C for 3 hours; then washed and dried to obtain vegetable tanned leather; the vegetable tanning agent includes glutaraldehyde and tannin; the mass ratio of the leather scraps to the tannin is 1.5:1, the concentration of glutaraldehyde is 15 g / L, and the pH value of the vegetable tanning agent is 5.5;

[0071] (2) The vegetable tanned leather is thinned, cut and assembled to obtain a first vegetable tanned leather filter cloth; the first vegetable tanned leather filter cloth is composed of three layers of vegetable tanned leather, and the thickness of each layer of vegetable tanned leather is in the range of 1 mm; the first vegetable tanned leather filter cloth is a circular structure with a diameter of 20 cm.

[0072] Example 2

[0073] (1) The cleaned leather scraps are soaked in a vegetable tanning agent for treatment, first at 25°C for 1 hour, then heated to 50°C for 3 hours; then washed and dried to obtain vegetable tanned leather; the vegetable tanning agent includes glutaraldehyde and tannin; the mass ratio of the leather scraps to the tannin is 2:1, the concentration of glutaraldehyde is 20 g / L, and the pH value of the vegetable tanning agent is 6;

[0074] (2) The vegetable tanned leather is thinned, cut and assembled to obtain a second vegetable tanned leather filter cloth; the second vegetable tanned leather filter cloth is composed of three layers of vegetable tanned leather, and the thickness of each layer of vegetable tanned leather is in the range of 1 mm; the second vegetable tanned leather filter cloth is a circular structure with a diameter of 20 cm.

[0075] Example 3

[0076] (1) The cleaned leather scraps are soaked in a vegetable tanning agent for treatment, first at 25°C for 1 hour, then heated to 50°C for 3 hours; then washed and dried to obtain vegetable tanned leather; the vegetable tanning agent includes glutaraldehyde and tannin; the mass ratio of the leather scraps to the tannin is 2.5:1, the concentration of glutaraldehyde is 25 g / L, and the pH value of the vegetable tanning agent is 6.5;

[0077] (2) The vegetable tanned leather is thinned, cut and assembled to obtain a third vegetable tanned leather filter cloth; the third vegetable tanned leather filter cloth is composed of three layers of vegetable tanned leather, and the thickness of each layer of vegetable tanned leather is in the range of 1 mm; the third vegetable tanned leather filter cloth is a circular structure with a diameter of 20 cm.

[0078] Example 4

[0079] (1) The cleaned leather scraps are soaked in a vegetable tanning agent for treatment, first at 25°C for 1 hour, then heated to 50°C for 3 hours; then washed and dried to obtain vegetable tanned leather; the vegetable tanning agent includes glutaraldehyde and tannin; the mass ratio of the leather scraps to the tannin is 2:1, the concentration of glutaraldehyde is 20 g / L, and the pH value of the vegetable tanning agent is 6;

[0080] (2) The vegetable tanned leather is thinned, cut and assembled to obtain a fourth vegetable tanned leather filter cloth; the fourth vegetable tanned leather filter cloth is composed of three layers of vegetable tanned leather, and the thickness of each layer of vegetable tanned leather is in the range of 0.8 mm; the fourth vegetable tanned leather filter cloth is a circular structure with a diameter of 20 cm.

[0081] Example 5

[0082] (1) The cleaned leather scraps are soaked in a vegetable tanning agent for treatment, first at 25°C for 1 hour, then heated to 50°C for 3 hours; then washed and dried to obtain vegetable tanned leather; the vegetable tanning agent includes glutaraldehyde and tannin; the mass ratio of the leather scraps to the tannin is 2:1, the concentration of glutaraldehyde is 20 g / L, and the pH value of the vegetable tanning agent is 6;

[0083] (2) The vegetable tanned leather is thinned, cut and assembled to obtain a fifth vegetable tanned leather filter cloth; the fifth vegetable tanned leather filter cloth is composed of three layers of vegetable tanned leather, and the thickness of each layer of vegetable tanned leather is in the range of 1.2 mm; the fifth vegetable tanned leather filter cloth is a circular structure with a diameter of 20 cm.

[0084] Impurity removal performance test of vegetable tanned leather filter cloth

[0085] (1) Taking 1 unit of industrial grade lithium carbonate raw material, wherein lithium carbonate <98.5wt%, calcium >500pm, magnesium >1000ppm, sulfate >4000ppm, chlorine >200ppm, sodium >1000ppm, potassium >300ppm; dispersing the industrial grade lithium carbonate in water, with the mass ratio of industrial grade lithium carbonate to water being 1:20, to obtain a slurry;

[0086] (2) introducing carbon dioxide into the slurry for hydrogenation to obtain a hydrogenated liquid;

[0087] (3) using a first vegetable tanned leather filter cloth, a second vegetable tanned leather filter cloth, a third vegetable tanned leather filter cloth, a fourth vegetable tanned leather filter cloth, and a fifth vegetable tanned leather filter cloth to filter 30 L of hydrogenated feed liquid, respectively, and then subjecting the filter cloth to the same thermal decomposition, solid-liquid separation, and powdering steps to obtain a first battery-grade lithium carbonate dry powder, a second battery-grade lithium carbonate dry powder, a third battery-grade lithium carbonate dry powder, a fourth battery-grade lithium carbonate dry powder, and a fifth battery-grade lithium carbonate dry powder, respectively;

[0088] (4) The first battery-grade lithium carbonate dry powder, the second battery-grade lithium carbonate dry powder, the third battery-grade lithium carbonate dry powder, the fourth battery-grade lithium carbonate dry powder and the fifth battery-grade lithium carbonate dry powder were tested respectively. The results are as follows:

[0089]

[0090] It can be seen from the above table that the vegetable tanned leather filter cloth can effectively remove calcium and magnesium, and can also effectively remove impurities such as sulfate, chlorine, sodium and potassium, thereby effectively purifying industrial-grade lithium carbonate to obtain battery-grade lithium carbonate; from Example 1, Example 2 and Example 3, compared with the first vegetable tanned leather filter cloth, the second vegetable tanned leather filter cloth and the third vegetable tanned leather filter cloth have better impurity removal effects, and preferably, the second vegetable tanned leather filter cloth is better; from Example 2, Example 4 and Example 5, compared with the fourth vegetable tanned leather filter cloth, the second vegetable tanned leather filter cloth and the fifth vegetable tanned leather filter cloth have better impurity removal effects. Taking into account factors such as efficiency and cost, the second vegetable tanned leather filter cloth is better.

[0091] The present invention removes impurities from industrial-grade lithium carbonate based on vegetable tanned leather scraps, and the obtained finished product meets the standards of battery-grade lithium carbonate. Compared with the existing technology, the method of the present invention is simple to operate, has good economy, and has high impurity removal efficiency.

[0092] The above is a detailed introduction to a method for removing impurities in industrial-grade lithium carbonate based on vegetable tanned leather scraps provided in an embodiment of the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for those skilled in the art, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A method for removing impurities from industrial-grade lithium carbonate based on vegetable tanned leather scraps, characterized in that: The following steps are involved: Leather making, wherein the cleaned leather scraps are soaked in a vegetable tanning agent for treatment, followed by washing and drying to obtain vegetable tanned leather; the vegetable tanning agent comprises glutaraldehyde and tannin; preparing a filter cloth by thinning, cutting and assembling the vegetable tanned leather to obtain a vegetable tanned leather filter cloth; Slurry preparation: dispersing industrial-grade lithium carbonate in water to obtain a slurry; hydrogenation, introducing carbon dioxide into the slurry for hydrogenation treatment to obtain a hydrogenated feed liquid; Filtering, using the vegetable tanned leather filter cloth to filter the hydrogenated feed liquid, wherein insoluble impurities are obtained in the solid phase and a lithium bicarbonate solution is obtained in the liquid phase; Thermal decomposition, heating the lithium bicarbonate solution to obtain a solid-liquid mixture; solid-liquid separation, filtering the solid-liquid mixture to obtain mother liquor and battery-grade wet lithium carbonate; Powdering: drying the battery-grade wet lithium carbonate and then crushing it to obtain battery-grade lithium carbonate dry powder.

2. The method for removing impurities from industrial-grade lithium carbonate based on vegetable tanned leather scraps as claimed in claim 1, wherein The mass ratio of the leather scraps to the tannin is in the range of 1.5 to 2.5:1, the concentration of the glutaraldehyde is in the range of 15 to 25 g / L, and the pH value of the vegetable tanning agent is in the range of 5.5 to 6.

5.

3. The method for removing impurities in industrial-grade lithium carbonate based on vegetable tanned leather scraps as claimed in claim 1, wherein The step of soaking the washed leather scraps in a vegetable tanning agent for treatment comprises: Soak the cleaned leather scraps in vegetable tanning agent, first treat at 20-30℃ for 0.5-1.5h, then heat to 45-55℃ for 2.5-3.5h.

4. The method for removing impurities in industrial-grade lithium carbonate based on vegetable tanned leather scraps as claimed in claim 1, wherein The vegetable tanned leather filter cloth is composed of three layers of vegetable tanned leather, and the thickness of each layer of vegetable tanned leather is in the range of 0.8 to 1.2 mm.

5. The method for removing impurities in industrial-grade lithium carbonate based on vegetable tanned leather scraps as claimed in claim 1, wherein In the slurry, the mass ratio of the industrial-grade lithium carbonate to water is in the range of 1:20 to 25.

6. The method for removing impurities in industrial-grade lithium carbonate based on vegetable tanned leather scraps as claimed in claim 1, wherein In the hydrogenation step, the purity of the carbon dioxide is >35%.

7. The method for removing impurities in industrial-grade lithium carbonate based on vegetable tanned leather scraps as claimed in claim 1, characterized in that In the filtration step, the hydrogenated feed liquid is filtered at normal pressure using the vegetable tanned leather filter cloth.

8. The method for removing impurities in industrial-grade lithium carbonate based on vegetable tanned leather scraps as claimed in claim 1, wherein In the thermal decomposition step, the temperature range of the heating treatment is 80-100°C.

9. The method for removing impurities in industrial-grade lithium carbonate based on vegetable tanned leather scraps as claimed in claim 1, wherein The mother liquor is recycled to the slurry preparation step.

10. The method for removing impurities in industrial-grade lithium carbonate based on vegetable tanned leather scraps according to claim 1, characterized in that In the industrial grade lithium carbonate, lithium carbonate is less than 98.5 wt%, calcium is greater than 500 ppm, and magnesium is greater than 1000 ppm.

Images