Lithium ion electrosorbent and lithium ion recovery method

Abstract

The application discloses a lithium ion electric adsorbent and a lithium ion recovery method. The application is based on the selective adsorption of lithium ion sieves on lithium ions and the electric field reinforced adsorption process, and develops a new type of high selective adsorption material coupled with an electric field to efficiently recover lithium ions in electrolyte. The lithium ion electric adsorbent is used to realize clean and efficient recovery of waste lithium ion batteries, and has a wide industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of resource recycling and environmental protection, specifically relating to a lithium-ion electroadsorbent and a method for recovering lithium ions using waste lithium-ion battery electrolyte as raw material. Background Technology

[0002] The new energy industry is a strategic and pioneering emerging industry globally, representing the future direction of technological change and energy development. In recent years, the global markets for new energy vehicles and large-scale electrochemical energy storage have experienced rapid growth. Lithium-ion batteries, due to their performance advantages, have become the mainstream track in the national new energy industry. Lithium-ion batteries possess advantages such as small size, light weight, high energy density, no memory effect, and environmental friendliness, thus becoming a core component of new energy vehicles. In recent years, with the booming development of the new energy vehicle industry, the number of retired lithium-ion batteries has also reached a peak. If a large number of retired lithium-ion batteries are not properly disposed of, they will cause serious environmental problems and endanger human life and health.

[0003] Lithium-ion batteries consist of positive and negative electrodes, electrolyte, separator, and metal casing. The electrolyte contains up to 18% lithium metal, sometimes even exceeding the lithium content in natural ores. Recycling the lithium from retired lithium-ion batteries can alleviate the pressure of lithium resource shortages and significantly improve the economic benefits for companies. Therefore, from the perspective of resource recycling and environmental protection, the recycling and utilization of lithium from the electrolyte of retired lithium-ion batteries is of great significance.

[0004] Currently, the main methods for recycling spent lithium-ion batteries are pyrometallurgical and hydrometallurgical processes. Pyrometallurgical processes offer large throughput and are simple, but they involve high operating temperatures, high energy consumption, demanding equipment requirements, and the generation of harmful gases, while also wasting Li and Al resources. Therefore, the development of hydrometallurgical recycling processes is attracting increasing attention. Hydrometallurgical processes offer low processing costs, high metal recovery rates, and good process stability, showing great development potential, but they still suffer from long process flows and highly corrosive leaching agents. Therefore, seeking a new, green, and safe solvent to achieve clean and efficient recycling of spent lithium-ion batteries is of significant scientific importance and has broad industrial application prospects, which is also of paramount importance for resource recycling. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a lithium-ion electroadsorbent and a method for recovering lithium ions using waste lithium-ion electrolyte as raw material.

[0006] A first aspect of the present invention provides a lithium-ion electroadsorbent, which is prepared by the following steps:

[0007] (1) Compressible biomass aerogels are prepared by dissolving polysaccharides, citric acid, lithium salts, tetrabutyl titanate and optional auxiliary metal salts in a solvent and freeze-drying them.

[0008] (2) The compressible biomass aerogel was calcined in an inert gas atmosphere. After calcination, a lithium-ion electroadsorbent precursor was obtained.

[0009] (3) The lithium-ion electro-adsorbent precursor is immersed in acid solution for reaction. After the reaction is completed, the lithium-ion electro-adsorbent is obtained.

[0010] According to the lithium-ion electroadsorbent of the first aspect, in step (1), the mass ratio of the polysaccharide, citric acid, lithium salt, tetrabutyl titanate and auxiliary metal salt is 7:1.4~14:2~10:10~50:0~6;

[0011] Preferably, the polysaccharide is chitosan and / or cellulose; and / or

[0012] Preferably, the auxiliary metal salt is ZrOCl2.

[0013] According to the lithium-ion electroadsorbent of the first aspect, in step (1), the polysaccharide is chitosan and cellulose; preferably, the mass ratio of chitosan to cellulose is 1:0.2 to 1:2.

[0014] According to the lithium-ion electroadsorbent of the first aspect, in step (1), the freeze-drying conditions are -20 to -80°C.

[0015] According to the lithium-ion electroadsorbent of the first aspect, in step (1), the solvent is a mixed solvent composed of ethanol, acetic acid and DMF; and / or the mass-volume ratio of the polysaccharide to the mixed solvent is 7:90~110g / mL;

[0016] Preferably, in the mixed solvent, the volume ratio of ethanol, acetic acid, and DMF is 50–100:10–50:15–60.

[0017] According to the lithium-ion electroadsorbent of the first aspect, wherein the inert gas atmosphere in step (2) is a nitrogen or argon atmosphere;

[0018] The calcination temperature is 500–900°C, preferably 550–750°C; and / or

[0019] The calcination time is 1 to 6 hours, preferably 3 to 5 hours;

[0020] Preferably, the heating rate of the calcination process is 1 to 10 °C / min, and more preferably 2 to 7 °C / min.

[0021] According to the lithium-ion electroadsorbent of the first aspect, wherein in step (3), the acid is a protic acid, preferably selected from one or more of the following: hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid; and / or

[0022] The soaking reaction time is 0.5 to 24 hours, preferably 6 to 12 hours.

[0023] A second aspect of the present invention provides a lithium-ion recycling method, wherein the method uses waste lithium-ion battery electrolyte as raw material and includes the following steps:

[0024] (A) The electrolyte from the discharged and dismantled waste lithium-ion batteries is added to an alcohol-salt solution, heated and stirred, and then filtered to obtain the first filtrate;

[0025] (B) Pass the first filtrate into a solvent separation tower to recover alcohol and organic solvent, and recover solids from the bottom of the tower;

[0026] (C) Dissolve the solid recovered in step (B) in water to form a lithium-containing solution, and use the lithium-ion electro-adsorbent of the first aspect as the working electrode cathode to perform electro-adsorption lithium extraction;

[0027] (D) Place the adsorption-saturated working electrode into a carbonate or fluoride solution, apply a reverse voltage to release lithium ions, and obtain lithium carbonate or lithium fluoride.

[0028] According to a second aspect of the present invention, in step (A), the alcohol in the alcohol-salt solution is selected from methanol, ethanol and / or ethylene glycol, and the salt in the alcohol-salt solution is a hydrochloride salt;

[0029] Preferably, the alcohol-salt solution is a saturated alcohol solution of a salt.

[0030] According to a second aspect of the present invention, in step (B), the solvent recovery method is a reverse spray process.

[0031] According to the method of the second aspect of the present invention, the electro-adsorption lithium extraction operation step in step (C) is as follows:

[0032] Using a lithium-ion electroadsorbent as the working electrode cathode, the device is placed in a lithium-containing solution. When the electroadsorption device is powered on, it starts to work. When the conductivity of the effluent is comparable to that of the influent, the electrode adsorption reaches saturation.

[0033] Preferably, the pH of the lithium-containing solution is adjusted to 5–12, the adsorption voltage to 0.5–5V, and / or the influent flow rate to 5–50 mL / min.

[0034] The lithium-ion electroadsorbent of the present invention has, but is not limited to, the following beneficial effects:

[0035] This invention develops a novel, highly selective adsorption material coupled with an electric field to efficiently recover lithium ions from electrolytes, based on the selective adsorption of lithium ions by a lithium-ion sieve adsorbent and the electric field-enhanced adsorption process. The lithium-ion electroadsorbent of this invention has a porous structure, which increases the contact area between the adsorbent and the solution. Furthermore, the lithium-ion electroadsorbent possesses a large number of lithium vacancies, thus enabling selective adsorption of lithium ions in the solution and enhancing the adsorption effect. In addition, the carbon framework of the lithium-ion electroadsorbent of this invention is also conductive, thereby strengthening its electroadsorption performance. This invention utilizes this lithium-ion electroadsorbent to achieve clean and efficient recycling of spent lithium-ion batteries, showing broad prospects for industrial applications. Attached Figure Description

[0036] Figure 1 The lithium-ion electroadsorption curve of Example 1 is shown. Detailed Implementation

[0037] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. Through these descriptions, the features and advantages of the present application will become clearer and more apparent.

[0038] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0039] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0040] This invention provides a lithium-ion electroadsorbent, which is prepared by the following steps:

[0041] (1) Compressible biomass aerogels are prepared by dissolving polysaccharides, citric acid, lithium salts, tetrabutyl titanate and optional auxiliary metal salts in a solvent and freeze-drying them.

[0042] (2) The compressible biomass aerogel was calcined in an inert gas atmosphere. After calcination, a lithium-ion electroadsorbent precursor was obtained.

[0043] (3) The lithium-ion electro-adsorbent precursor is immersed in acid solution for reaction. After the reaction is completed, the lithium-ion electro-adsorbent is obtained.

[0044] The lithium-ion electroadsorbent prepared in this invention comprises a carbon framework and a titanium-based lithium-ion sieve. The titanium-based lithium-ion sieve, after delithiation by acid leaching, enhances the selectivity for lithium-ion adsorption during the electroadsorption process. The carbon framework not only stabilizes the structure but also possesses conductivity, thereby strengthening the electroadsorption performance of the lithium-ion electroadsorbent. Furthermore, the lithium-ion electroadsorbent of this invention has a porous structure, increasing its contact area with the solution and improving the adsorption of lithium ions in the solution. Citric acid has a cross-linking effect on polysaccharides, enabling esterification of the hydroxyl groups in polysaccharides. Under the cross-linking effect of citric acid, polysaccharides form a cross-linked structure, thereby enhancing the strength and stability of the aerogel.

[0045] In one embodiment, in step (1), the mass ratio of the polysaccharide, citric acid, lithium salt, tetrabutyl titanate and auxiliary metal salt is 7:(1.4-14):(2-10):(10-50):(0-6);

[0046] Preferably, the polysaccharide is chitosan and / or cellulose; and / or

[0047] Preferably, the auxiliary metal salt is ZrOCl2.

[0048] Doping titanium-based lithium-ion sieves with auxiliary metal salt ZrOCl2 is beneficial to improving the chemical stability of the sieve.

[0049] In one embodiment, in step (1), the polysaccharide is chitosan and cellulose; preferably, the mass ratio of chitosan to cellulose is 1:0.2 to 1:2.

[0050] In one embodiment, in step (1), the solvent is a mixed solvent composed of ethanol, acetic acid, and DMF; and / or the mass-to-volume ratio of the polysaccharide to the mixed solvent is 7:(90-110) g / mL;

[0051] Preferably, in the mixed solvent, the volume ratio of ethanol, acetic acid, and DMF is (50-100):(10-50):(15-60);

[0052] In one embodiment, in step (1), the freeze-drying conditions are -20 to -80°C. In one embodiment, the inert gas atmosphere in step (2) is a nitrogen or argon atmosphere.

[0053] The calcination temperature is 500–900°C, preferably 550–750°C; and / or

[0054] The calcination time is 1 to 6 hours, preferably 3 to 5 hours.

[0055] Preferably, the heating rate of the calcination process is 1 to 10 °C / min, and more preferably 2 to 7 °C / min.

[0056] In one embodiment, in step (3), the acid is a protic acid, preferably selected from one or more of the following: hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid; and / or

[0057] The soaking reaction time is 0.5 to 24 hours, preferably 6 to 12 hours.

[0058] This invention provides a method for recovering lithium ions using waste lithium-ion battery electrolyte as raw material, the method comprising the following steps:

[0059] (A) The electrolyte from the discharged and dismantled waste lithium-ion batteries is added to an alcohol-salt solution, heated and stirred, and then filtered to obtain the first filtrate;

[0060] (B) Pass the first filtrate into a solvent separation tower to recover alcohol and organic solvent, and recover solids from the bottom of the tower;

[0061] (C) Dissolve the solid recovered in step (B) in water to form a lithium-containing solution, and use the above-mentioned lithium-ion electro-adsorbent as the working electrode cathode to perform electro-adsorption lithium extraction;

[0062] (D) Place the adsorption-saturated working electrode into a carbonate or fluoride solution, apply a reverse voltage to release lithium ions, and obtain lithium carbonate or lithium fluoride.

[0063] Organic solvents account for over 80% of the electrolyte in lithium-ion batteries, mainly including cyclic carbonates (propylene carbonate PC, ethylene carbonate EC), chain carbonates (diethyl carbonate DEC, dimethyl carbonate DMC, ethyl methyl carbonate EMC), and carboxylic acid esters (methyl formate MF, methyl acetate MA, ethyl acetate EA, methyl propionate MP, etc.). The highly hazardous electrolyte lithium hexafluorophosphate in the electrolyte is converted into a chemically stable hexafluorophosphate using an alcohol-salt solution. The alcohol and organic solvents in the electrolyte are then recovered through solvent separation. The solid recovered at the bottom of the column dissolves in water to form a lithium-containing solution, which is then subjected to electroadsorption and desorption using the lithium-ion electroadsorbent prepared in this invention. Lithium ions are recovered from the lithium carbonate or lithium fluoride precipitate obtained after desorption.

[0064] This invention discloses a method for recovering lithium ions from waste lithium-ion electrolyte. Based on the principle of "like dissolves like" and component conversion methods, an alcohol-salt solution is added to achieve efficient extraction of organic solvents inside the battery and to convert the highly hazardous electrolyte into chemically stable hexafluorophosphate. Then, based on spray-enhanced heat transfer to promote the vaporization and recovery of organic reagents, and based on the selective adsorption of lithium ions by lithium-ion sieve adsorbents and the electric field-enhanced adsorption process, a novel highly selective adsorption material coupled with the electric field is developed to efficiently recover lithium ions from the electrolyte. A stepwise processing technology is established to achieve efficient recovery of lithium, fluorine, and phosphorus from the electrolyte.

[0065] In one embodiment, in step (A), the alcohol in the alcohol-salt solution is selected from methanol, ethanol and / or ethylene glycol, and the salt is a hydrochloride salt;

[0066] Preferably, the alcohol-salt solution is a saturated alcohol solution of a salt.

[0067] In one embodiment, in step (B), the solvent recovery method is a countercurrent spray process. In this step, the countercurrent spray method can also be combined with a low-temperature vacuum distillation process for the recovery of alcohols and organic solvents.

[0068] In one embodiment, the electro-adsorption lithium extraction operation step (C) is as follows:

[0069] Using a lithium-ion electroadsorbent as the working electrode cathode, the device is placed in a lithium-containing solution. When the electroadsorption device is powered on, it starts to work. When the conductivity of the effluent is comparable to that of the influent, the electrode adsorption reaches saturation.

[0070] Preferably, the pH of the lithium-containing solution is adjusted to 5–12, the adsorption voltage to 0.5–5V, and / or the influent flow rate to 5–50 mL / min.

[0071] The solution after lithium ion extraction can be further concentrated and crystallized to recover hexafluorophosphate.

[0072] The present invention will be further described in detail below through examples. Unless otherwise specified, all reagents and other materials used in the following examples are commercially available finished products.

[0073] Preparation Example

[0074] This preparation example illustrates the preparation method of the lithium-ion electroadsorbent of the present invention.

[0075] (1) 3.5g chitosan, 3.5g cellulose, 7g citric acid, 5g LiAc and 25g tetrabutyl titanate were dissolved in 105mL of solvent, which was a solution of ethanol:acetic acid:DMF with a volume ratio of 8:1:1.5. The mixture was stirred and mixed evenly, and then freeze-dried at -70℃ to prepare compressible biomass aerogel.

[0076] (2) The compressible biomass aerogel obtained in step (1) is heated to 600°C for 3 hours under N2 atmosphere at a heating rate of 5°C / min. After calcination, a lithium-ion electroadsorbent precursor is obtained.

[0077] (3) The lithium-ion electroadsorbent precursor was soaked in 0.2 mol / L hydrochloric acid for 12 h. After the reaction was completed, the lithium-ion electroadsorbent was obtained.

[0078] Example 1

[0079] This embodiment illustrates the adsorption capacity test of the lithium-ion electroadsorbent of the present invention. A 1L solution with a lithium-ion content of 1000mg / L was prepared, and the pH of the lithium-containing solution was adjusted to 5-12. A 5cm×5cm×2cm lithium-ion electroadsorbent was used as the working electrode cathode, and a 5cm×5cm×0.2cm titanium plate was used as the counter electrode anode. The electrode was placed in the lithium-containing solution, and the adsorption voltage was set to 0.5-5V.

[0080] In this embodiment, the voltage is set to 1.5V, the influent flow rate is 5-50 mL / min, and the electroadsorption experiment is conducted at room temperature for 40 minutes. The electroadsorption device is powered on and begins operation. When the conductivity of the effluent water is comparable to that of the influent water, the electrode adsorption reaches saturation. Then, the saturated electrode is removed and placed in a carbonate solution, such as a sodium carbonate solution. The electrode is then reversed to desorb lithium ions, yielding lithium carbonate and regenerating the lithium-ion electroadsorbent, thus completing one adsorption cycle.

[0081] The results are as follows Figure 1 As shown, the adsorption reached equilibrium after 30 minutes, and the lithium ion adsorption capacity in a single experiment was approximately 425 mg.

[0082] Example 2

[0083] This embodiment is used to illustrate the performance of the lithium-ion electroadsorbent prepared in this invention.

[0084] Prepare a 1L solution with a lithium ion concentration of 1000mg / L. Use a 5cm×5cm×2cm lithium ion electroadsorbent as the cathode and a 5cm×5cm×0.2cm titanium plate as the anode. Set the voltage to 2V. The rest is the same as in Example 1. The adsorption capacity of lithium ions in a single experiment is about 403mg.

[0085] Example 3

[0086] Prepare a 1L solution with a lithium ion concentration of 1000mg / L. The operating parameters are the same as in Example 1. Repeat the adsorption-desorption experiment in Example 1. After 3 cycles, the lithium ion recovery rate in the solution reaches 95%. Collect the lithium carbonate in the solution and test its purity to be 96%.

[0087] Example 4

[0088] This embodiment illustrates the use of the lithium-ion electroadsorbent prepared according to the present invention to recover lithium ions from the electrolyte of waste lithium-ion batteries.

[0089] (A) The electrolyte from the discharged and dismantled waste lithium-ion batteries is added to a saturated alcohol solution of salt, heated and stirred, and then filtered to obtain the first filtrate.

[0090] (B) Pass the first filtrate into a solvent separation tower to recover alcohol and organic solvent, and recover solids from the bottom of the tower;

[0091] In this embodiment, alcohol and organic solvent are recovered using two solvent separation towers connected in series. Each solvent separation tower has a volume of 10L (bottom area 0.02m²). 2 (Height 0.5m), air pressure inside the tower 1.1atm.

[0092] The first filtrate is fed into the top of the first solvent separation column and sprayed at a rate of 0.05 m / s using a countercurrent spray method. 3 Nitrogen gas is bubbled in from the bottom of the column at a rate of 0.1 m / min. 3 The solvent alcohol is separated at a rate of 0.05 m / min at a first temperature of 50°C. The second filtrate obtained at the bottom of the column is fed into the top of the second solvent separation column and sprayed at a rate of 0.05 m / min using a countercurrent spray method. 3 Nitrogen gas is bubbled in from the bottom of the column at a rate of 0.1 m / min. 3 The organic solvent is separated at a second temperature of 90°C per minute, and the solid is recovered from the bottom of the column.

[0093] (C) Dissolve the solid recovered in step (B) in water to form a lithium-containing solution, and use the lithium-ion electro-adsorbent of Example 1 as the working electrode cathode to perform electro-adsorption lithium extraction;

[0094] (D) Place the adsorption-saturated working electrode into a carbonate or fluoride solution, apply a reverse voltage to release lithium ions, and obtain lithium carbonate or lithium fluoride.

[0095] In this embodiment, steps (C) and (D) specifically include:

[0096] The solid recovered from the bottom of the tower in step (B) was dissolved in 1L of water to form a lithium-containing solution. Electro-adsorption lithium extraction was performed according to the method in Example 1. After 5 cycles, the recovery rate of lithium ions in the solution reached 89%. The lithium carbonate in the solution was collected and its purity was tested to be 90%.

[0097] The present application has been described above with reference to preferred embodiments; however, these embodiments are merely exemplary and illustrative. Various substitutions and modifications can be made to the present application based on these embodiments, all of which fall within the protection scope of the present application.

Claims

1. A lithium-ion electroadsorbent, characterized in that, The lithium-ion electroadsorbent comprises a carbon framework and a titanium-based lithium-ion sieve, and is prepared by the following steps: (1) Compressible biomass aerogels are prepared by dissolving polysaccharides, citric acid, lithium salts, tetrabutyl titanate and optional auxiliary metal salts in a solvent and freeze-drying them. (2) The compressible biomass aerogel was calcined in an inert gas atmosphere. After calcination, a lithium-ion electroadsorbent precursor was obtained. (3) The lithium-ion electro-adsorbent precursor is immersed in acid solution for reaction. After the reaction is completed, the lithium-ion electro-adsorbent is obtained.

2. The lithium-ion electroadsorbent according to claim 1, characterized in that, In step (1), the mass ratio of the polysaccharide, citric acid, lithium salt, tetrabutyl titanate and auxiliary metal salt is 7:1.4-14:2-10:10-50:0-6.

3. The lithium-ion electroadsorbent according to claim 1, characterized in that, In step (1), the polysaccharide is chitosan and / or cellulose; and / or The auxiliary metal salt is ZrOCl2.

4. The lithium-ion electroadsorbent according to claim 3, characterized in that, In step (1), the polysaccharide is chitosan and cellulose, and the mass ratio of chitosan to cellulose is 1:0.2 to 1:

2.

5. The lithium-ion electroadsorbent according to claim 1, characterized in that, In step (1), the freeze-drying conditions are -20 to -80°C.

6. The lithium-ion electroadsorbent according to claim 1, characterized in that, In step (1), the solvent is a mixed solvent composed of ethanol, acetic acid, and DMF; and / or The mass-to-volume ratio of the polysaccharide to the mixed solvent is 7:90-110 g / mL.

7. The lithium-ion electroadsorbent according to claim 1, characterized in that, In step (2), the inert gas atmosphere is a nitrogen or argon atmosphere; The calcination temperature is 500–900°C; and / or The calcination time is 1 to 6 hours.

8. The lithium-ion electroadsorbent according to claim 1, characterized in that, In step (3), the acid is a protic acid; and / or The soaking reaction time is 0.5 to 24 hours.

9. The lithium-ion electroadsorbent according to claim 8, characterized in that, In step (3), the acid is selected from one or more of the following: hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid; and / or The soaking reaction time is 6 to 12 hours.

10. A method for lithium-ion recovery, characterized in that, The method uses waste lithium-ion battery electrolyte as raw material and includes the following steps: (A) The electrolyte from the discharged and dismantled waste lithium-ion batteries is added to an alcohol-salt solution, heated and stirred, and then filtered to obtain the first filtrate; (B) Pass the first filtrate into a solvent separation tower to recover alcohol and organic solvent, and recover solids from the bottom of the tower; (C) Dissolve the solid recovered in step (B) in water to form a lithium-containing solution, and use the lithium-ion electro-adsorbent as the working electrode cathode according to any one of claims 1 to 9 to perform electro-adsorption lithium extraction; (D) Place the adsorption-saturated working electrode into a carbonate or fluoride solution, apply a reverse voltage to release lithium ions, and obtain lithium carbonate or lithium fluoride.

11. The method according to claim 10, characterized in that, In step (A), the alcohol in the alcohol-salt solution is selected from methanol, ethanol and / or ethylene glycol, and the salt in the alcohol-salt solution is a hydrochloride salt.

12. The method according to claim 10, characterized in that, In step (B), the method for recovering the alcohol and organic solvent is a reverse spray process.

13. The method according to claim 10, characterized in that, The electro-adsorption lithium extraction operation steps described in step (C) are as follows: Using a lithium-ion electroadsorbent as the working electrode cathode, placed in a lithium-containing solution, the electroadsorption device starts working when the power is turned on. When the conductivity of the effluent is comparable to that of the influent, the electrode adsorption reaches saturation.

14. The method according to claim 13, characterized in that, Adjust the pH of the lithium-containing solution to 5–12; The adsorption voltage is 0.5–5V; and / or The influent flow rate is 5-50 mL / min.

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