Decomposition of Ca2PO4Cl and methods for Ca / P resource utilization

Abstract

This invention belongs to the field of solid waste utilization, specifically providing a method for the decomposition and resource utilization of Ca2PO4Cl. The method involves dispersing Ca2PO4Cl in an alcohol solvent for solvothermal modification to obtain a modified material; then, the modified material is protonated in a separation solution containing an additive of formula 1 and hydrochloric acid to decompose it into phosphoric acid and calcium chloride as treatment products; subsequently, calcium chloride and phosphoric acid are separated. The method for the decomposition and resource utilization of Ca2PO4Cl is currently a gap in the industry. To fill this technological gap, this invention innovatively demonstrates that pre-modifying Ca2PO4Cl in an alcohol solvent followed by ion exchange in a hydrochloric acid solution containing formula 1 can achieve the decomposition of Ca2PO4Cl to form calcium chloride and phosphoric acid.

Description

Technical Field

[0001] This invention belongs to the field of slag recovery, specifically relating to the separation of P / Ca in Ca2PO4Cl. Background Technology

[0002] Lithium iron phosphate (LFP) batteries are gaining increasing market share in China due to their advantages such as being environmentally friendly and safe, having a long cycle life, and being cost-effective. However, a large number of retired power LFP batteries urgently need recycling. Although existing processes can recover valuable metals from LFP, some LFP recycling processes produce slag containing the Ca2PO4Cl phase. Current technologies lack effective decomposition and Ca / P selective separation methods for this phase.

[0003] For example, Chinese patent document CN104773716A discloses a method for producing feed-grade sodium calcium phosphate, specifically disclosing a method of calcining calcium chlorophosphate with salt at 800–1200°C to obtain feed-grade sodium calcium phosphate. Furthermore, Chinese patent document CN115043384A discloses a method for producing calcium pyrophosphate by hydrochloric acid decomposition of low-grade phosphate rock, specifically describing a method of calcining calcium chlorophosphate at 550±20°C to obtain calcium pyrophosphate.

[0004] In summary, there is currently no method for efficiently decomposing Ca2PO4Cl and recycling it to produce calcium chloride and phosphoric acid. Summary of the Invention

[0005] In view of the lack of existing technologies for the decomposition of Ca2PO4Cl and the utilization of calcium and phosphorus resources, the primary objective of this invention is to provide a method for the decomposition of Ca2PO4Cl, which aims to decompose the calcium and phosphorus in Ca2PO4Cl into phosphoric acid and calcium chloride.

[0006] The second objective of this invention is to provide a method for the resource utilization of Ca / P in Ca2PO4Cl, which aims to decompose and recycle calcium and phosphorus in Ca2PO4Cl to obtain calcium phosphate and calcium chloride.

[0007] The Ca2PO4Cl decomposition method involves dispersing Ca2PO4Cl in an alcohol solvent and then performing a solvothermal modification treatment to obtain a modified material.

[0008] The modified material is then protonated in a separation solution containing additive of formula 1 and hydrochloric acid to decompose it into the treatment products of phosphoric acid and calcium chloride.

[0009]

[0010] In Formula 1, at least one of R1 to R3 is substituted with an alkyl group of C1 to C3, and the remaining substituents are H.

[0011] The methods for decomposing and utilizing Ca2PO4Cl are still a gap in the industry. To fill this technological gap, this invention innovatively demonstrates that Ca2PO4Cl can be decomposed by first undergoing solvothermal transformation in an alcohol, followed by ion exchange in a hydrochloric acid solution containing Formula 1, thereby forming calcium chloride and phosphoric acid.

[0012] In this invention, the Ca2PO4Cl can be any raw material containing the Ca2PO4Cl phase in the industry. For example, it can be obtained by roasting and water leaching Ca2PO4Cl (water leaching residue) from waste battery lithium iron phosphate materials and calcium chloride and sodium salts.

[0013] In this invention, the solvotherm under the alcohol solvent is one of the keys to achieving the Ca2PO4Cl transformation, thereby facilitating the subsequent recovery of calcium and phosphorus resources. Preferably, the alcohol solvent includes C1-C4 alcohols; more preferably, at least one of methanol and ethanol; most preferably, methanol. Studies have shown that using methanol as a solvent can unexpectedly further improve the modification effect and help to further improve the calcium and phosphorus decomposition effect.

[0014] In this invention, the liquid-to-solid ratio of the alcohol solvent and Ca2PO4Cl is 10–40 mL / g, and can be further 15–35 mL / g.

[0015] In this invention, the temperature for solvothermal modification is 100–200°C, preferably 120–180°C; more preferably 125–145°C. This invention also demonstrates that at the preferred temperature, the modification effect is further optimized, and the decomposition and subsequent separation effects are further improved.

[0016] Preferably, the solvent thermal modification treatment time is 1 to 10 hours, and considering the treatment efficiency, it can be further extended to 2 to 4 hours.

[0017] In this invention, the solvothermal modified material is placed in a hydrochloric acid solution containing the additive of Formula 1 for protonation treatment, which facilitates the decomposition of Ca2PO4Cl and improves the decomposition efficiency.

[0018] In this invention, in the additive of Formula 1, R1 to R3 are methyl, ethyl, or isopropyl.

[0019] In this invention, the additive of Formula 1 can be produced by Formula 2. It is prepared by reacting with hydrochloric acid.

[0020] In this invention, the separation liquid further comprises an alcohol solvent. The alcohol solvent can be at least one of methanol and ethanol.

[0021] In this invention, the modified material can be dispersed in a mixed solution containing the additive of Formula 1 and an alcohol solvent, and then hydrochloric acid solution is added to adjust the pH of the system to complete the protonation reaction.

[0022] In this invention, the weight ratio of the additive and the modifier of Formula 1 is 1.5 to 3:1; preferably 2 to 2.5:1.

[0023] In this invention, the protonation treatment temperature is 35–65°C; more specifically, it can be 45–55°C. Studies have shown that at the preferred temperature, it helps to further optimize the decomposition effect.

[0024] The pH during the protonation process is controlled between 1 and 3, preferably between 1 and 2.

[0025] Preferably, the protonation treatment time is 0.15 to 2 hours; more preferably, it is 0.5 to 1 hour.

[0026] As part of the same inventive concept, this invention also provides a method for the resource utilization of Ca / P from Ca2PO4Cl, wherein Ca2PO4Cl is subjected to solvothermal modification and protonation treatment to obtain phosphoric acid and calcium chloride as treatment products; the treatment products are then subjected to low-temperature crystallization at 0-10°C to obtain calcium chloride product and a crystallization mother liquor enriched with phosphoric acid.

[0027] In this invention, soft water is used to extract the crystallization mother liquor to obtain a phosphoric acid solution.

[0028] Beneficial effects

[0029] This invention fills a technological gap in the decomposition and resource utilization of Ca2PO4Cl. It innovatively transforms Ca2PO4Cl through solvothermal modification in an alcohol, followed by ion exchange in a hydrochloric acid solution containing Formula 1. This process decomposes Ca2PO4Cl to form calcium chloride and phosphoric acid, achieving calcium-phosphorus separation. In this invention, the purity of H3PO4 can reach up to 99%, allowing for the preparation of products for use. CaCl2, as an important chemical product, can be used in various industries. Attached Figure Description

[0030] Figure 1 The XRD pattern of Ca2PO4Cl used in Example 1;

[0031] Figure 2 The image shows the XRD pattern of the phosphate recovered in Example 1 after conversion to ammonium molybdate. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0033] In this invention, the Ca2PO4Cl can be obtained from the tailings after the treatment of waste lithium batteries, and the method of obtaining it is as follows:

[0034] Waste LFP (lithium iron phosphate) cathode material is uniformly mixed with calcium chloride and sodium salts (such as one or more of sodium chloride, sodium carbonate, and sodium bicarbonate), then calcined, followed by water leaching to obtain lithium iron phosphate leachate and Ca2PO4Cl water leaching residue (see patent document application number 2025100576368 for details). Its XRD pattern is shown below. Figure 1 This invention demonstrates that the decomposition efficiency of the Ca2PO4Cl water-leached residue directly in a hydrochloric acid system is not high. Therefore, this invention provides a process involving alcohol-assisted solvothermal modification and decomposition assisted by an agent of Formula 1, specifically:

[0035] The steps of the method for decomposing and utilizing Ca2PO4Cl according to the present invention include, for example:

[0036] Step (1): Solvent heat treatment

[0037] Ca2PO4Cl and alcohol are placed in a high-pressure reactor at a certain volume ratio, the temperature is controlled at 120-180℃, the time is 120-600 min, and the liquid-solid ratio is 10-30 mL / g.

[0038] Step (2): Filtering

[0039] The mixture obtained above was filtered under normal pressure, and the filter residue was washed with anhydrous ethanol and dried for later use.

[0040] Step (3): Protonation treatment

[0041] Under normal pressure, the filter residue from step 2 is mixed with triethylamine hydrochloride, with the mass ratio of filter residue to triethylamine hydrochloride controlled at 1:2-2.3. Anhydrous ethanol is used as the solvent, hydrochloric acid is used to control the pH of the system at 1-2, the temperature is controlled at 40-50℃, and the reaction is carried out for 15-40 minutes.

[0042] Step (4): Low-temperature separation

[0043] The system temperature is controlled at 0-10 degrees Celsius. After CaCl2 crystals precipitate from the solution, the solution is filtered and dried to obtain the CaCl2 product. The filtrate is extracted with soft water to obtain H3PO4 and raffinate. The raffinate can be acidified with hydrochloric acid and used as an auxiliary agent, and then recycled to the protonation treatment step in step 3.

[0044] Example 1

[0045] Step 1 Solvent heat treatment: Place Ca2PO4Cl in a 50mL polytetrafluoroethylene liner, add methanol with a liquid-to-solid ratio of 20mL / g, then seal it and place it in a reaction oven at 120℃ for 140min.

[0046] Step 2 Filtration: The mixture obtained above is filtered under normal pressure. The filter residue is washed repeatedly with anhydrous ethanol 3-5 times and dried in an 80℃ oven for later use.

[0047] Step 3: Protonation treatment: Add 2.3 times its weight of triethylamine hydrochloride to the dried filter residue, using anhydrous ethanol (liquid-to-solid ratio of 20 mL / g) as solvent. -1 Disperse the mixture, then adjust the pH of the system to 1-2 with 1-2M hydrochloric acid, control the reaction temperature at 40℃, and react for 30 minutes.

[0048] Step 4: Low-temperature separation: After the reaction, the solution is cooled to between 0-10℃, and white crystals gradually appear. These are CaCl2 crystals. After filtration, the solution is dried. The filtrate is extracted with soft water to obtain dilute H3PO4 and raffinate. The raffinate is acidified with hydrochloric acid and then recycled. The dilute H3PO4 needs to be further concentrated before it can be used as a product.

[0049] The obtained phosphoric acid was first analyzed qualitatively using pH test paper, with a pH value of 1-2. Then, the ammonium phosphomolybdate method was used for more precise detection. The specific steps are as follows: Take the obtained phosphoric acid solution, add ammonium molybdate tetrahydrate, stir, and after precipitation occurs, slow down the stirring speed. Filter the resulting mixture, wash the precipitate with anhydrous ethanol, and the bright yellow precipitate is preliminarily identified as ammonium phosphomolybdate. Dry the precipitate and perform XRD to determine the phase. The XRD results are shown below. Figure 2 This indicates that the obtained product is indeed phosphoric acid, demonstrating that the method of the present invention achieves the resource-based preparation of phosphoric acid.

[0050] Example 2

[0051] Compared with Example 1, the only difference is that in step 1, methanol in the solvent heat treatment step is replaced with anhydrous ethanol, and the other operations and parameters are the same as in Example 1.

[0052] Example 3

[0053] Compared with Example 1, the only difference is that in step 1, the liquid-solid ratio of methanol to Ca2PO4Cl during the solvothermal treatment process is adjusted to 30 mL / g, and other operations and parameters are the same as in Example 1.

[0054] Example 4

[0055] Compared with Example 1, the only difference is that in step 1, the reaction temperature during the solvothermal treatment process is 180°C and the reaction time is 120 min. Other operations and parameters are the same as in Example 1.

[0056] Example 5

[0057] Compared with Example 1, the only difference is that in step 3, the reaction temperature in the protonation treatment step is 50°C and the reaction time is 40 min. Other operations and parameters are the same as in Example 1.

[0058] Comparative Example 1

[0059] Compared with Example 1, the only difference is that hydrochloric acid was not added in step 3, while the other operations and parameters are the same as in Example 1.

[0060] Comparative Example 2

[0061] Compared with Example 1, the only difference is that in step 3, the triethylamine hydrochloride in the protonation treatment step is replaced with ammonium chloride, and the other operations and parameters are the same as in Example 1.

[0062] Comparative Example 3

[0063] Compared with Example 1, the only difference is that in step 1, the solvent heat treatment is not performed, but ultrasonic pretreatment is performed instead. The type and proportion of solvent remain unchanged, and the ultrasonic treatment lasts for 60 minutes.

[0064] Comparative Example 4

[0065] Compared with Example 1, the only difference is that in step 1, the processing is carried out under normal pressure by reflux, while other operations and parameters are the same as in Example 1.

[0066] Comparative Example 5

[0067] Compared with Example 1, the only difference is that in step 1, an equal volume of water is used to replace the methanol, while other operations and parameters are the same as in Example 1.

[0068] Table 1 shows the purity and yield of the obtained products:

[0069]

[0070] This invention fills the technological gap in the efficient fractionation of Ca2PO4Cl and the separation and utilization of Ca / P. It innovatively transforms Ca2PO4Cl by solvothermal modification in alcohol, followed by ion exchange in hydrochloric acid solution containing Formula 1. This decomposes Ca2PO4Cl to form calcium chloride and phosphoric acid, thus achieving the separation of calcium and phosphorus.

Claims

1. A method for decomposing Ca2PO4Cl, characterized in that, Ca2PO4Cl is dispersed in an alcohol solvent and subjected to solvothermal modification to obtain a modified material; the alcohol solvent includes C1 to C4 alcohols; The modified material is then protonated in a separation solution containing additive of formula 1 and hydrochloric acid to decompose it into the treatment products of phosphoric acid and calcium chloride. Formula 1 In Formula 1, at least one of R1 to R3 is substituted with a C1 to C3 alkyl group, and the remaining substituents are H.

2. The Ca2PO4Cl decomposition method as described in claim 1, characterized in that, Ca2PO4Cl is prepared by the following method: waste LFP cathode material is mixed with calcium chloride and sodium salt, roasted, and leached in water, followed by solid-liquid separation to obtain Ca2PO4Cl.

3. The Ca2PO4Cl decomposition method as described in claim 1, characterized in that, The alcohol solvent is at least one of methanol and ethanol.

4. The Ca2PO4Cl decomposition method as described in claim 1, characterized in that, The liquid-to-solid ratio of the alcohol solvent and Ca2PO4Cl is 10~40mL / g.

5. The Ca2PO4Cl decomposition method as described in claim 1, characterized in that, The temperature for solvent thermal modification is 100~200℃.

6. The Ca2PO4Cl decomposition method as described in claim 5, characterized in that, The temperature for solvent thermal modification is 120~180℃.

7. The Ca2PO4Cl decomposition method as described in claim 1, characterized in that, The solvent thermal modification treatment time is 1~10h.

8. The Ca2PO4Cl decomposition method as described in claim 1, characterized in that, In the additive of Formula 1, R1 to R3 are methyl, ethyl, or isopropyl.

9. The method for decomposing Ca2PO4Cl as described in claim 1, characterized in that, The separation liquid also contains alcohol solvent.

10. The Ca2PO4Cl decomposition method as described in claim 1, characterized in that, The weight ratio of additives and modifiers in Formula 1 is 1.5 to 3:

1.

11. The Ca2PO4Cl decomposition method as described in claim 10, characterized in that, The weight ratio of the additive and the modifier in Formula 1 is 2~2.5:

1.

12. The Ca2PO4Cl decomposition method as described in claim 1, characterized in that, The protonation treatment temperature is 35~65℃.

13. The Ca2PO4Cl decomposition method as described in claim 1, characterized in that, The pH during the protonation process is controlled between 1 and 3.

14. The Ca2PO4Cl decomposition method as described in claim 1, characterized in that, The protonation treatment time is 0.15~2h.

15. The Ca2PO4Cl decomposition method as described in claim 14, characterized in that, The protonation treatment time is 0.5~1h.

16. A method for the resource utilization of Ca2PO4Cl and Ca / P, characterized in that, The Ca2PO4Cl is solvothermal modified and protonated using any one of the Ca2PO4Cl decomposition methods according to claims 1 to 15 to obtain the treated products of phosphoric acid and calcium chloride; the treated products are then crystallized at low temperature of 0 to 10°C to obtain calcium chloride product and crystallization mother liquor enriched with phosphoric acid.

17. The method for resource utilization of Ca2PO4Cl / Ca / P as described in claim 16, characterized in that, The mother liquor from crystallization was extracted with soft water to obtain a phosphoric acid solution.

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