A method for producing titanium dioxide from waste lithium titanate batteries

Abstract

The present invention relates to the field of waste lithium-ion battery. More particularly, the present invention relates to a method for producing titanium dioxide from waste lithium titanate batteries in a commercially feasible manner. The method recovers the titanium with purity of titanium dioxide greater than 98% by following simple physical processes such as shredding, roasting, leaching and precipitation. The method is clean, green and environment friendly.

Description

[0001] “A METHOD FOR PRODUCING TITANIUM DIOXIDE FROM WASTE LITHIUM TITANATE BATTERIES”

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to the field of waste lithium-ion batteries. More particularly, the present invention relates to a method for producing titanium dioxide from waste lithium titanate batteries.

[0004] BACKGROUND OF THE INVENTION

[0005] A lithium-titanate or lithium-titanium-oxide (LTO) battery is a modified lithium-ion battery in which the anode material is lithium-titanate that enables the availability of more surface area as compared to other anode material like carbon or lithium iron phosphate. Moreover, the charging in case of lithium-titanate is faster and quicker as compared to other anode material. Since, the lithium titanate battery is free of carbon due to which it does not get overheated like those of the other batteries, which have low energy storage systems, hence the lithium titanate battery is safe and user-friendly to be used in any application.

[0006] The lithium titanate batteries are used in different applications like UPS, electrical power trains, solar-powered street lights, fast-charge stations, and forklifts. Other applications for LTO batteries include aerospace and military uses, and more

[0007] The continuous usage of lithium titanate battery may cause harm to the environment as it produces harmful gas on excessive usage, due to which the battery gets swelled up (especially at high temperatures). The gas produced by the lithium titanate battery causes environmental pollution to a large extent. Besides the advantages and disadvantages of lithium titanate battery, the recycling of waste / spent lithium titanate battery is still not explored commonly on a large scale.

[0008] Conventionally, the most commonly used method for recycling the spent lithium titanate battery involves dismantling, shredding, melting or dissolving the shredded battery in acid. Rest of the materials are recovered for the purpose of manufacturing other batteries or to be used for some other purpose. However, most of the studies that include the recycling of the lithium titanate batteries, claim to recover only the cathode part of the battery to obtain high valuable metals, while the study on recovering the anode part of the battery still remains unexplored.

[0009] CN108550946A discloses about a method of recycling lithium chloride and titanium dioxide from lithium titanate waste material, whereby the waste lithium titanate material is calcined for 1-5 hours at 200-500°C. Lithium is selectively leached in HC1+H2O2solution from the calcined mass, which is further crystallized as LiCl or precipitated as Li2CO3. Then, the residual mass is calcined at 600-1000°C to yield TiO2. The limitation of the invention is that, the process includes higher temperature ranges.

[0010] CN109546252A discloses about circulating and recycling method for valuable metal in negative pole piece of waste lithium titanate battery. The method comprises the steps of: calcining the negative pole piece of the waste lithium titanate battery to obtain a calcined product; leaching the calcined product in an alkaline solution, and then filtering the calcined product by centrifugation to remove residues, so as to obtain a first filtrate; slowly adding an acidic substance into the first filtrate to remove aluminium (Al), and then filtering the filtrate to obtain a second filtrate; performing primary extraction and purification on the second filtrate to obtain a first extracted organic phase containing impurities and a first raffmate containing valuable metal; performing secondary extraction on the first raffmate to obtain a second extracted organic phase and a second raffmate, performing acid pickling and reverse extraction on the second extracted organic phase to obtain a second strip liquor, performing concentration drying on the second strip liquor to obtain metatitanic acid, and calcining the metatitanic acid to obtain analytically pure titanium dioxide; and performing evaporation and concentration as well as cooling crystallization on the second raffmate to obtain battery -level lithium carbonate. However, the method involves the use of a large number of chemicals such as strong acids, alkaline solution, extractants like di (2 -ethylhexyl) phosphoric acid, saponifying agents and the calcination of the metatitanic acid to obtain the high-purity titanium dioxide is specifically achieved at a very high range of temperature of 500- 900°C for long duration of 10-35 hours. Hence, the method is lengthy, time consuming, complex and neither commercially feasible nor environment-friendly due to the use of harmful chemicals. CN109037722A discloses about a method of recycling lithium in waste and old lithium titanate series lithium ion battery negative electrode that involves the steps of: charging waste lithium titanate battery; disassembling the fully charged battery to obtain a negative electrode sheet, and a positive electrode sheet; placing the negative electrode plate at 150°C; heat treating at a temperature in a range of 150-550°C; adding sulfuric acid or hydrochloric acid into the aqueous solution containing lithium titanate powder and continuously stirring to adjust the pH to 1-2 and then filter to obtain a titanium- containing filter residue and a solution of a lithium-containing compound which is lithium sulfate and lithium chloride. The drawback of this invention is that it fails to recover titanium in the form of pure titanium dioxide from waste lithium titanate battery.

[0011] CN109065999A discloses about a method of recycling waste and old lithium titanate battery, which includes hydrochloric acid (HC1) leaching with controlled pH monitoring inbetween 0.5- 1.5 in order to leach all the metals except titanium. The leach residue was then chlorinated to dissolve titanium chloride (TiCl4). TiCl4is recovered as the endproduct after gaseous chlorination. The major limitation of the invention is that it discloses the use of harmful chemicals and fails to recover titanium in an environmental friendly manner in the form of titanium dioxide.

[0012] Wenjiang Tang et al. (doi: dx.doi.org / 10.1016 / j.hydromet.2014.05.013 Hydrometallurgy vol. 147-148, p. 210-216) in 2014 in their research article entitled “Recovery of Ti and Ti from spent lithium titanate cathodes by a hydrometallurgical process”, discloses about solvent extraction using primary amine N1923, employed from the sulfuric acid leached solution. Urea and sodium dodecyl benzene sulfonate (SDBS) is used for nano-precipitation of titanium and lithium is recovered as Ti2CO3. The research article discloses the use of harmful chemicals and hence, is not environment friendly.

[0013] However, the state of art does not provides any commercially feasible method of recycling the waste / spent lithium titanate batteries for the production of highly pure titanium dioxide (TiO2) with enhanced efficacy and by utilizing a simple technique.

[0014] Therefore, there is a need for an approach that resolves problems of state of art to provide a simple, commercially feasible and environment friendly method for recovery and recycling of titanium from spent lithium titanate batteries. OBJECT OF THE INVENTION

[0015] The main object of the present invention is to provide a method for producing titanium dioxide from waste / spent lithium titanate batteries.

[0016] Another object of the present invention is to provide a commercially feasible method for producing pure titanium dioxide from waste / spent lithium titanate batteries.

[0017] Yet another object of the present invention is to provide a method, which ensures greater recovery (> 95%) of titanium with titanium dioxide purity of (>98%) from waste / spent lithium titanate batteries.

[0018] Yet another object of the present invention is to provide a method, which has high recovery efficiency of titanium from waste / spent lithium titanate batteries.

[0019] Still another object of the present invention is to provide a method which is simple, clean, green and environment friendly.

[0020] SUMMARY OF THE INVENTION

[0021] The present invention relates to a method for producing titanium dioxide from waste lithium titanate batteries. The method is commercially feasible, clean green and environment friendly. The method provides recovery of titanium (> 95%) with purity of titanium dioxide (>98%).

[0022] In an embodiment, the present invention provides a method for producing titanium dioxide from waste lithium titanate batteries that comprises the steps of: (a) shredding cells obtained by dismantling discharged spent lithium titanate (TTO) batteries to obtain a shredded material; (b) removing organic matrix by roasting the shredded material of step (a) at a pre-determined temperature for 2-3 hours and obtaining a roasted material; (c) washing the roasted material of step (b) with water followed by wet sieving to collect a slurry and a metal part separately; (d) filtering the slurry of step (c) to obtain a precipitated cake and a filtrate and reusing the filtrate in next batch; (e) blending the precipitated cake of step (d) with sulphuric acid taken in a pre-defmed ratio followed by pugging at a pre-determined temperature for a pre-determined time to obtain a pugged material; (f) leaching the pugged material of step (e) with a pre-defmed concentration of dilute sulphuric acid for a pre-determined time to obtain a leach slurry; (g) filtering the leach slurry of step (f) to obtain a leach liquor and a residue; (h) precipitating selectively titanium from the leach liquor of step (g) at a pre-determined pH by adding a suitable precipitating agent under agitation for a pre-determined time to obtain a slurry and a cake; (i) filtering the slurry of step (h) to obtain a titanium cake (under wet condition) and a filtrate and taking the filtrate for base metal recovery; and (j) washing the titanium cake of step (i) with water to remove free sodium salt in the form of sodium sulphate and obtaining a washed cake of titanium carbonate followed by roasting of the washed cake at a temperature range of 600-850°C for 2-3 hours to obtain titanium dioxide.

[0023] In another embodiment, the present invention provides a method of discharging spent lithium titanate (LTO) batteries of step (a), through the steps comprising of: (i) connecting spent lithium titanate (LTO) batteries to a discharging apparatus; (ii) initiating the discharging process by monitoring ampere through ammeter and voltage through voltmeter; (iii) monitoring subsequently the discharging process until the current in ampere and voltage came down to zero; and (iv) disconnecting the spent lithium titanate (LTO) batteries from the discharging apparatus to obtain discharged batteries.

[0024] The present invention relates to a method for producing titanium dioxide from waste lithium titanate batteries in a commercially feasible manner. This method also ensures recovery of titanium in a range of 95-97% in the form of titanium dioxide with purity of titanium dioxide 98-99% by following simple physical processes shredding, roasting, leaching and precipitation.

[0025] The above objects and advantages of the present invention will become apparent from the hereinafter set forth brief description of the drawings, detailed description of the invention and claim appended herewith.

[0026] BRIEF DESCRIPTION OF THE DRAWING

[0027] An understanding of the method for producing titanium dioxide from waste lithium titanate batteries of the present invention may be obtained by reference to the following drawings: Figure 1 is a schematic representation of the process flow for method for producing titanium dioxide from spent lithium titanate batteries according to an embodiment of the present invention.

[0028] DETAILED DESCRIPTION OF THE INVENTION

[0029] The present invention will now be described hereinafter with reference to the accompanying drawings in which a preferred embodiment of the invention is shown. This invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiment set forth herein. Rather, the embodiment is provided so that this disclosure will be thorough, and will fully convey the scope of the invention to those skilled in the art.

[0030] The present invention now will be described hereinafter with reference to the detailed description, in which some, but not all embodiments of the invention are indicated. Indeed, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout. The present invention is described fully herein with non-limiting embodiments and exemplary experimentation.

[0031] The present invention relates to a method for producing titanium dioxide from waste lithium titanate batteries in a commercially feasible method. The method provides recovery of titanium with purity of titanium dioxide in a range of 98-99%.

[0032] In a preferred embodiment, the present invention provides a method for producing titanium dioxide from waste lithium titanate batteries that comprises the steps of: (a) shredding cells obtained by dismantling discharged spent lithium titanate (LTO) batteries with a twin shaft shredder having a pre-determined output size to obtain a shredded material; (b) removing organic matrix by roasting the shredded material of step (a) at a pre-determined temperature for 2-3 hours and obtaining a roasted material; (c) washing the roasted material of step (b) with water followed by wet sieving to collect a slurry and a metal part separately; (d) filtering the slurry of step (c) to obtain a precipitated cake and a filtrate and reusing the filtrate in next batch; (e) blending the precipitated cake of step (d) with sulphuric acid taken in a pre-defined ratio followed by pugging at a pre- determined temperature for a pre-determined time to obtain a pugged material; (f) leaching the pugged material of step (e) with a pre-defmed concentration of dilute sulphuric acid for a pre-determined time to obtain a leach slurry; (g) filtering the leach slurry of step (f) to obtain a leach liquor and a residue; (h) precipitating selectively titanium from the leach liquor of step (g) at a pre-determined pH by adding a suitable precipitating agent under agitation for a pre-determined time to obtain a slurry and a cake; (i) filtering the slurry of step (h) to obtain a titanium cake (under wet condition) and a filtrate and taking the filtrate for base metal recovery; and (j) washing the titanium cake of step (i) with water to remove free sodium salt in the form of sodium sulphate and obtaining a washed cake of titanium carbonate followed by roasting of the washed cake at a temperature range of 600-850°C for 2-3 hours to obtain titanium dioxide.

[0033] Additionally, a single shaft shredder or a twin shaft shredder having an output size less than 10 mm is used for shredding the cells; the pre-determined temperature in step (b) is in a range of 400-600°C; the pre-defmed ratio of the sulphuric acid in step (e) and the precipitated cake of step (d) is (0.9-1.1):1; the pre-determined temperature and the predetermined time in step (e) is in a range of 150-250°C and 2-4 hours, respectively.

[0034] Further, the pre-defmed concentration of dilute sulphuric acid of step (f) is 5-15% w / v and the pre-determined time of step (f) is 2-3 hours; the pre-determined pH in step (h) is in a range of 0.5- 1.5 and the pre-determined time of step (h) is 2-3 hours and the base metal recovery includes recovery of cobalt, nickel, copper and manganese.

[0035] The suitable precipitating agent in step (h) is selected from soda ash solution (25% w / v), calcium carbonate, calcium hydroxide, sodium hydroxide, ammonium carbonate, ammonium hydroxide or any base, preferably soda ash solution (25% w / v).

[0036] In another preferred embodiment, the present invention provides a method of discharging spent lithium titanate (LTO) batteries of step (a), through the steps comprising of: (i) connecting spent lithium titanate (LTO) batteries to a discharging apparatus; (ii) initiating the discharging process by monitoring ampere through ammeter and voltage through voltmeter; (iii) monitoring subsequently the discharging process until the current in ampere and voltage came down to zero; and (iv) disconnecting the spent lithium titanate (LTO) batteries from the discharging apparatus to obtain discharged batteries. The discharged batteries of step (a) are dismantled manually to collect cells and other components including aluminium, printed circuit board, plastic, steel, and rubber separately.

[0037] Referring to Figure 1, a schematic representation of the process flow sheet for method for producing titanium dioxide from spent lithium titanate batteries is illustrated. The method for producing titanium dioxide from waste lithium titanate batteries, recovers titanium in a range of 95-97% in the form of titanium dioxide. The purity of titanium dioxide is in a range of 98-99%.

[0038] EXAMPLE 1

[0039] Method for producing titanium dioxide from waste lithium titanate batteries Batch 1

[0040] In batch 1, 12.98 kg of spent lithium titanate (LTO) batteries were discharged and dismantled manually to get 3.738 kg of cells and 9.248 kg of other components (aluminium (Al), printed circuit boards (PCB), plastic, steel, rubber). The cells (3.738 kg) were shredded and then roasted at 500°C for 2 hours. The roasted material (2.888 kg) obtained was washed with water followed by sieving to get 1.466 kg cake of black mass (dry weight-1.1 kg) and 1.79 kg of Al-casing & foil. Table 1 represents the detailed material balance of the mechanical operation to get black mass for the process.

[0041] Table 1

[0042] Material balance of the mechanical operation of batch 1

[0043] From the obtained black mass, 1 kg of material was blended with 0.9 kg of sulphuric acid and pugged at 200°C for 4 hours. After 4 hours, the pugged material was cool and weighed and the weight of pugged material was 1.1 kg. 1 kg from the pugged material was agitated with 10% (w / v) sulphuric acid (6 L) for 3 hours and then filtered to get the leach liquor (6 L) and the residue (0.12 kg). The analysis of black mass, pugged material, leach liquor, and residue were presented in Table 2.

[0044] Table 2

[0045] Analysis of black mass, pugged material, leach liquor, and residue of batch 1 To the leach liquor (6 L), 1.5 L of soda ash solution 25% (w / v) was added under agitation for 2 hours. The slurry was filtered and the filtrate was taken for base metal recovery while the cake (0.394 kg) was further washed with water (1:5). The washed cake was roasted at 800°C for 3 hours and the titanium dioxide (129.27 g) was obtained.

[0046] Batch 2

[0047] In batch 2, 12.962 kg of spent TTO batteries were discharged and dismantled manually to get 3.729 kg of cells and 9.233 kg of other components (aluminium (Al), printed circuit boards (PCB), plastic, steel, rubber). The cells (3.729 kg) were shredded and then roasted at 500°C for 2 hours. The roasted material (2.869 kg) obtained was washed with water followed by sieving to get 1.453 kg cake of black mass (dry weight-1.09 kg) and 1.78 kg of Al-casing & foil. Table 3 represents the detailed material balance of the mechanical operation of batch 2 to get black mass for the process.

[0048] Table 3 Material balance of the mechanical operation of batch 2

[0049] From the above black mass, 1 kg was blended with 1 kg of sulphuric acid and pugged at 200°C for 4 hours. After 4 hours, the pugged material was allowed cool to 30°C and weighed and the weight of pugged material was 1.16 kg. 1 kg from the pugged material was agitated with 10% (w / v) sulphuric acid (6 L) for 3 hours and then filtered to get the leach liquor (6 L) and the residue (0.11 kg). Table 4 presents a detailed analysis of black mass, pugged material, leach liquor, and residue.

[0050] Table 4

[0051] Analysis of black mass, pugged material, leach liquor, and residue of batch 2

[0052] To the leach liquor (6 L), 1.6 L of soda ash solution 25% (w / v) was added under agitation for 2 hours. The slurry was filtered and the filtrate was taken for base metal recovery while the cake (0.413 kg) was further washed with water (1:5). The washed cake was roasted at 800°C for 3 hours and the titanium dioxide (135 g) was obtained. Purity of titanium dioxide in batch 1 and batch 2

[0053] The purity and impurity profile of the products obtained in batches 1 and 2 during the processes were determined by IS: 8862-1978 and Microwave Plasma Atomic emission spectra (MP-AES), respectively. The analysis of titanium dioxide obtained in batches 1 and 2 is presented in Table 5.

[0054] Table 5

[0055] Analysis of the products obtained in batches 1 and 2

[0056] Therefore, the present invention provides a simple, time-efficient, commercially feasible and environmentally-friendly method for producing pure titanium dioxide having purity greater than 98% from the waste lithium titanate batteries.

[0057] Many modifications and other embodiments of the invention set forth herein will readily occur to one skilled in the art to which the invention pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

CLAIMSWe claim:

1. A method for producing titanium dioxide from waste lithium titanate batteries, characterized in that, the method comprises the steps of: a) shredding cells obtained by dismantling discharged spent lithium titanate (LTO) batteries to obtain a shredded material; b) removing organic matrix by roasting the shredded material of step (a) at a predetermined temperature for 2-3 hours and obtaining a roasted material; c) washing the roasted material of step (b) with water followed by wet sieving to collect a slurry and a metal part separately; d) filtering the slurry of step (c) to obtain a precipitated cake and a filtrate and reusing the filtrate in next batch; e) blending the precipitated cake of step (d) with sulphuric acid taken in a predefined ratio followed by pugging at a pre-determined temperature for a predetermined time to obtain a pugged material; f) leaching the pugged material of step (e) with a pre-defined concentration of dilute sulphuric acid for a pre-determined time to obtain a leach slurry; g) filtering the leach slurry of step (f) to obtain a leach liquor and a residue; h) precipitating selectively titanium from the leach liquor of step (g) at a predetermined pH by adding a suitable precipitating agent under agitation for a pre-determined time to obtain a slurry and a cake; i) filtering the slurry of step (h) to obtain a titanium cake (under wet condition) and a filtrate and taking the filtrate for base metal recovery; and j) washing the titanium cake of step (i) with water to remove free sodium salt in the form of sodium sulphate and obtaining a washed cake of titaniumcarbonate followed by roasting of the washed cake at a temperature range of 600-850°C for 2-3 hours to obtain titanium dioxide.

2. The method for producing titanium dioxide from waste lithium titanate batteries as claimed in claim 1 , wherein the spent lithium titanate (LTO) batteries of step (a) are discharged through the steps comprising of: i) connecting spent lithium titanate (LTO) batteries to a discharging apparatus; ii) initiating the discharging process by monitoring ampere through ammeter and voltage through voltmeter; iii) monitoring subsequently the discharging process until the current in ampere and voltage came down to zero; and iv) disconnecting the spent lithium titanate (LTO) batteries from the discharging apparatus to obtain discharged batteries.

3. The method for producing titanium dioxide from waste lithium titanate batteries as claimed in claim 1 , wherein the discharged batteries of step (a) are dismantled manually to collect cells and other components including aluminium, printed circuit board, plastic, steel, and rubber separately.

4. The method for producing titanium dioxide from waste lithium titanate batteries as claimed in claim 1, wherein a single shaft shredder or a twin shaft shredder having an output size less than 10 mm is used for shredding the cells of step (a).

5. The method for producing titanium dioxide from waste lithium titanate batteries as claimed in claim 1, wherein the pre-determined temperature in step (b) is in a range of 400-600°C.

6. The method for producing titanium dioxide from waste lithium titanate batteries as claimed in claim 1, wherein the pre-defmed ratio of the sulphuric acid in step(e) and the precipitated cake of step (d) is (0.9-1.1):1 and the pre-determined temperature and the pre-determined time in step (e) is in a range of 150-250°C and 2-4 hours, respectively.

7. The method for producing titanium dioxide from waste lithium titanate batteries as claimed in claim 1 , wherein the pre-defmed concentration of dilute sulphuric acid of step (f) is 5-15%w / v and the pre-determined time of step (f) is 2-3 hours.

8. The method for producing titanium dioxide from waste lithium titanate batteries as claimed in claim 1 , wherein the pre-determined pH in step (h) is in a range of 0.5- 1.5, and the pre-determined time of step (h) is 2-3 hours.

9. The method for producing titanium dioxide from waste lithium titanate batteries as claimed in claim 1, wherein the suitable precipitating agent in step (h) is selected from soda ash solution (25% w / v), calcium carbonate, calcium hydroxide, sodium hydroxide, ammonium carbonate or ammonium hydroxide.

10. The method for producing titanium dioxide from waste lithium titanate batteries as claimed in claim 1, wherein the method recovers titanium in a range of 95-97% in the form of titanium dioxide.

11. The method for producing of titanium dioxide from waste lithium titanate batteries as claimed in claim 1, wherein the purity of titanium dioxide is in a range of 98-99%.

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