Method for preparing aluminum dihydrogen phosphate and comprehensively recovering lithium salt from lithium phosphorus aluminum ore

Abstract

The invention provides a method for preparing aluminum dihydrogen phosphate and comprehensively recovering lithium salt from lithium phosphorus aluminum ore, and relates to the technical field of metal recovery, the method comprises the following steps: S1, ball-milling the lithium phosphorus aluminum ore; s2, carrying out nitric acid pressure leaching to obtain phosphorus lithium aluminum ore powder, and carrying out solid-liquid separation to obtain a leaching solution and leaching residues; s3, adjusting the pH value of the leachate to obtain an aluminum dihydrogen phosphate precipitate and a filtrate; s4, deeply removing impurities from the filtrate, adding Na2CO3, and precipitating to obtain Li2CO3 and lithium precipitation mother liquor; and S5, the lithium precipitation mother liquor is returned to the step S3 to be used for adjusting the pH of the leachate. According to the method, after the lithium phosphate aluminum ore is subjected to ball milling, a roasting section is omitted, the production cost is saved, valuable elements in the lithium phosphate aluminum ore are comprehensively recycled, other impurity ions are not introduced, only inert substances mainly containing silicon are contained in leaching residues, the environment pollution is reduced, meanwhile, the comprehensive economic value of the ore is improved, and the method has the advantages of being short in process route, low in cost and the like. The extraction rate of valuable elements is high, and the purity of aluminum dihydrogen phosphate and lithium carbonate is high.

Description

Technical Field

[0001] The invention relates to the technical field of metal recovery, and in particular to a method for preparing aluminum dihydrogen phosphate from lithium aluminum phosphate ore and comprehensive recovery of lithium salts. Background Art

[0002] With the rapid development of the lithium battery industry, many upstream companies have been driven to develop and utilize lithium-containing minerals. As the lithium extraction technology of lithium-containing resources such as salt lakes, spodumene, and lepidolite becomes more and more mature, the high-quality mineral of phosphate lithium aluminum ore has attracted widespread attention. Phosphorus lithium aluminum ore can be further divided into fluorophosphate lithium aluminum ore and hydroxyphosphate lithium aluminum ore, both of which contain a large amount of phosphorus and aluminum, and the LiO2 taste is far higher than the currently widely used spodumene and lepidolite. Up to now, according to the results of mineral resource exploration, the mine mostly exists in the form of associated minerals, mainly distributed in African countries such as Congo, South Africa, and Nigeria, and has also been found in southern Jiangxi, Jiuling in northwestern Jiangxi, and Nanping, Fujian. With the increasing maturity of lithium extraction technology of lithium-containing resources such as spodumene and lepidolite, some personnel have been invested in the development and utilization of phosphate lithium aluminum ore.

[0003] The process of extracting lithium from phosphate-lithium aluminum ore to prepare high-purity aluminum dihydrogen phosphate disclosed in the prior art usually uses excess acid and phosphate-lithium aluminum ore to extract lithium slag for three times of acid leaching, and after washing and desulfurization, high-temperature drying is used to obtain the aluminum dihydrogen phosphate product. This method has problems such as long process flow, high energy consumption, large amount of water, and introduction of foreign drugs such as desulfurizers and chelating agents. Alternatively, lithium is extracted from phosphate-lithium aluminum ore and iron-containing phosphate is prepared, and a lithium-containing solution and an aluminum phosphate precipitate are obtained by leaching after high-temperature roasting, and then the aluminum phosphate precipitate is leached with an acid solution, and an iron source and an alkaline substance are added to the leachate to adjust the pH to prepare an iron-containing phosphate. This method has problems such as low comprehensive resource utilization, high energy consumption, and environmental pollution.

[0004] The prior art also discloses a method for extracting lithium from phosphate lithium aluminum stone, which either uses sulfuric acid and raw ore to roast at high temperature and then soak in water, and after purification and impurity removal, lithium sulfate is obtained by evaporation and concentration, resulting in problems such as high process energy consumption and low resource utilization. Or, concentrated sulfuric acid and raw ore are roasted at high temperature and then soaked in water, and lithium carbonate products are obtained after purification and impurity removal. This results in problems such as long process flow, high energy consumption, low comprehensive resource utilization, and environmental pollution.

[0005] Therefore, a method for preparing aluminum dihydrogen phosphate from lithium aluminum ore and comprehensive recovery of lithium salts is developed, which shortens the process flow, increases the comprehensive utilization rate of resources, and reduces energy consumption, which is of great significance to the field. Summary of the invention

[0006] The purpose of the method of the present invention is to solve the problems of difficulty in comprehensive recovery of valuable ions in the leaching solution of lithium aluminum phosphate, low ore utilization rate, poor economic benefits, environmental pollution, etc. Specifically:

[0007] A method for preparing aluminum dihydrogen phosphate from lithium aluminum phosphate ore and comprehensive recovery of lithium salts, comprising:

[0008] Step S1, ball-milling the phosphate-lithium-aluminum ore to a certain particle size to obtain phosphate-lithium-aluminum ore powder;

[0009] Step S2, leaching the phosphate-lithium-aluminum ore powder with nitric acid under pressure, and obtaining a leaching solution containing P, Al, and Li and a leaching residue mainly containing silicon dioxide after solid-liquid separation;

[0010] Step S3, adjusting the pH of the leaching solution to obtain aluminum dihydrogen phosphate precipitate and a filtrate mainly composed of LiNO3, NaNO3, and KNO3;

[0011] Step S4, adding Na2CO3 to the filtrate after chemical impurity removal and resin deep adsorption to precipitate Li2CO3 and lithium precipitation mother liquor;

[0012] Step S5, returning the lithium precipitation mother liquor to step S3 for adjusting the pH of the leaching solution.

[0013] Preferably, in step S1, the particle size of the phosphate lithium aluminum ore powder is D90≤0.18mm; preferably D90≤0.045mm.

[0014] Preferably, in step S2, the conditions for nitric acid pressure leaching are: the amount of nitric acid added is 80-150%, preferably 100-150%, of the theoretical amount required to convert all metal cations in the phosphate lithium aluminum ore into corresponding nitrates; the liquid-solid ratio is 1-5:1; the leaching temperature is 130-170°C, preferably 160°C; the leaching pressure is 0.3-0.7Mpa; and the leaching time is 1-4h.

[0015] Preferably, in step S3, the lithium precipitation mother liquor is used entirely when adjusting the pH of the leaching solution.

[0016] Preferably, in step S3, the pH value of the leaching solution is adjusted to an end point of 1-3, the precipitation reaction temperature is 40-110° C., and the reaction time is 0.5-3 h.

[0017] Preferably, in step S4, the mass of sodium carbonate used is 80-150% of the theoretical value of lithium precipitation, preferably 110%.

[0018] The beneficial effects brought about by the technical solution provided by the present invention include at least:

[0019] The present invention utilizes the lithium precipitation mother liquor in this set of processes as a precipitant to realize the comprehensive recovery of phosphorus and aluminum ions in the process. First, the process adopts nitric acid pressure leaching to reduce the process section of mineral roasting, saves production costs, and can leach most of the valuable elements into the leachate. At the same time, the lithium precipitation mother liquor generated in the process is used to adjust the pH value of the system, and phosphorus and aluminum can be precipitated in the form of aluminum dihydrogen phosphate at the same time, and comprehensive recovery is high in economic benefits. In addition, the lithium precipitation mother liquor generated in the process is used as a precipitant, which reduces the risk of introducing other impurity ions, while recycling the valuable ions such as lithium in the system to improve the yield and reduce the subsequent purification and recovery process of the lithium precipitation mother liquor. Therefore, the process realizes the separation and comprehensive recovery of valuable ions in the system in the form of circulating lithium precipitation mother liquor, without the need to use additional precipitants, avoiding the introduction of new impurity ions, and reducing the subsequent separation of impurities. The process flow of the present invention is short, the process is simple, the feasibility is strong, it is green and environmentally friendly, the valuable ions are comprehensively recycled, and the production cost is reduced, while the output value of the corresponding by-products is increased, and it is easy to realize large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. 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 creative work.

[0021] Figure 1 The present invention is a process flow chart for preparing aluminum dihydrogen phosphate and comprehensive recovery of lithium salts from phosphate-lithium aluminum ore. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the present invention more clear, the technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] The results of the analysis of the components of the pyrophosphate used in the examples are shown in Table 1.

[0024] Table 1 Analysis results of lithium aluminum phosphate composition

[0025]

[0026] Example 1

[0027] like Figure 1 As shown, it is a process flow chart of a method for preparing aluminum dihydrogen phosphate and comprehensive recovery of lithium salt from a phosphate-lithium aluminum ore of the present invention, and the detailed steps are as follows:

[0028] S1: crushing and ball-milling the phosphate-lithium aluminum ore to make the output particle size D90≤0.075mm;

[0029] S2: The phosphate-lithium aluminum ore fraction obtained in S1 was leached at 160°C for 3h with nitric acid having a theoretical acid amount of 115%, a liquid-to-solid ratio of 3:1, and a leaching pressure of 0.45 MPa to obtain a leaching solution containing P, Al, and Li and a leaching residue mainly composed of silicon dioxide;

[0030] S3: The leaching solution prepared in S2 is adjusted to pH = 2 at 60°C, and reacted for 2h to obtain aluminum dihydrogen phosphate and a filtrate mainly composed of LiNO3, NaNO3, and KNO3;

[0031] S4: After deep impurity removal, the filtrate obtained in S3 is added with 110% of the theoretical amount (calculated according to the multivalent ions in the liquid after impurity removal) of Na2CO3 to precipitate Li2CO3 and a lithium precipitation mother liquor.

[0032] In this embodiment, the yield of lithium is 93.67%, the yield of aluminum is 66.32%, the yield of phosphorus is 58.69%, and the purity of aluminum dihydrogen phosphate is 82.31%.

[0033] Example 2

[0034] A method for preparing aluminum dihydrogen phosphate from lithium aluminum phosphate ore and comprehensive recovery of lithium salts is implemented according to the method described in Example 1, except that:

[0035] S3: The leaching solution prepared in S2 is adjusted to pH = 2 by adding the lithium precipitation mother solution obtained in Example 1 at 110°C, and the reaction is carried out for 2 hours to obtain aluminum dihydrogen phosphate and a filtrate mainly composed of LiNO3, NaNO3, and KNO3.

[0036] In this embodiment, the yield of lithium is 94.10%, the yield of aluminum is 72.37%, the yield of phosphorus is 80.54%, and the purity of aluminum dihydrogen phosphate is 85.41%.

[0037] Example 3

[0038] A method for preparing aluminum dihydrogen phosphate from lithium aluminum phosphate ore and comprehensive recovery of lithium salts is implemented according to the method described in Example 1, except that:

[0039] S3: The leaching solution prepared in S2 is added with the lithium precipitation mother solution obtained in Example 1 at 60°C to adjust the pH value of the system to 1, and react for 2 hours to obtain aluminum dihydrogen phosphate and a filtrate mainly composed of LiNO3, NaNO3, and KNO3;

[0040] In this embodiment, the yield of lithium is 92.17%, the yield of aluminum is 60.29%, the yield of phosphorus is 54.92%, and the purity of aluminum dihydrogen phosphate is 80.27%.

[0041] Example 4

[0042] A method for preparing aluminum dihydrogen phosphate from lithium aluminum phosphate ore and comprehensive recovery of lithium salts is implemented according to the method described in Example 1, except that:

[0043] S3: The leaching solution prepared in S2 is added with the lithium precipitation mother solution obtained in Example 1 at 60°C to adjust the pH value of the system to 1, and the reaction is carried out for 0.5h to obtain aluminum dihydrogen phosphate and a filtrate mainly composed of LiNO3, NaNO3 and KNO3.

[0044] In this embodiment, the yield of lithium is 91.31%, the yield of aluminum is 63.11%, the yield of phosphorus is 55.21%, and the purity of aluminum dihydrogen phosphate is 81.19%.

[0045] Example 5

[0046] A method for preparing aluminum dihydrogen phosphate from lithium aluminum phosphate ore and comprehensive recovery of lithium salts is implemented according to the method described in Example 1, except that:

[0047] S3: The leaching solution prepared in S2 was added with the lithium precipitation mother solution obtained in Example 1 at 60°C to adjust the pH value of the system to 3, and reacted for 2 hours to obtain aluminum dihydrogen phosphate and a filtrate mainly composed of LiNO3, NaNO3, and KNO3.

[0048] In this embodiment, the yield of lithium is 94.16%, the yield of aluminum is 80.76%, the yield of phosphorus is 79.95%, and the purity of aluminum dihydrogen phosphate is 81.19%.

[0049] Example 6

[0050] A method for preparing aluminum dihydrogen phosphate from lithium aluminum phosphate ore and comprehensive recovery of lithium salts is implemented according to the method described in Example 1, except that:

[0051] S2: The phosphate-lithium aluminum ore fraction obtained in S1 was leached at 120°C for 3h with nitric acid containing 110% of the theoretical acid amount, a liquid-to-solid ratio of 3:1, and a leaching pressure of 0.3 MPa to obtain a leaching solution containing P, Al, and Li and a leaching residue mainly composed of silicon dioxide;

[0052] In this embodiment, the yield of lithium is 85.10%, the yield of aluminum is 60.21%, the yield of phosphorus is 48.33%, and the purity of aluminum dihydrogen phosphate is 78.23%.

[0053] Comparative Example 1

[0054] A method for preparing aluminum dihydrogen phosphate from lithium aluminum phosphate ore and comprehensive recovery of lithium salts is implemented according to the method described in Example 1, except that:

[0055] S3: The leaching solution prepared in S2 is added with the lithium precipitation mother solution obtained in Example 1 at room temperature to adjust the pH value of the system to 2, and the reaction is carried out for 2 hours to obtain aluminum dihydrogen phosphate and a filtrate mainly composed of LiNO3, NaNO3 and KNO3;

[0056] In this embodiment, the yield of lithium is 88.31%, the yield of aluminum is 58.22%, the yield of phosphorus is 54.11%, and the purity of aluminum dihydrogen phosphate is 69.97%.

[0057] Comparative Example 2

[0058] A method for preparing aluminum dihydrogen phosphate from lithium aluminum phosphate ore and comprehensive recovery of lithium salts is implemented according to the method described in Example 1, except that:

[0059] S3: The leaching solution prepared in S2 is added with the lithium precipitation mother solution obtained in Example 1 at 60°C to adjust the pH value of the system to 4, and react for 2h to obtain aluminum dihydrogen phosphate and a filtrate mainly composed of LiNO3, NaNO3 and KNO3;

[0060] The yield of lithium in this embodiment is 92.91%, and a large amount of precipitation is generated in step S3, which becomes a paste after stirring for a period of time. The yield of aluminum is 71.22%, the yield of phosphorus is 51.48%, and the purity of aluminum dihydrogen phosphate is 43.92%.

[0061] Comparative Example 3

[0062] A method for preparing aluminum dihydrogen phosphate from lithium aluminum phosphate ore and comprehensive recovery of lithium salts is implemented according to the method described in Example 1, except that:

[0063] S3: The leaching solution prepared in S2 is added with the lithium precipitation mother solution obtained in Example 1 at 60°C to adjust the pH value of the system to 2, and react for 5 hours to obtain aluminum dihydrogen phosphate and a filtrate mainly composed of LiNO3, NaNO3 and KNO3;

[0064] In this embodiment, the yield of lithium is 78.21%, the yield of aluminum is 59.72%, the yield of phosphorus is 52.31%, and the purity of aluminum dihydrogen phosphate is 78.23%.

[0065] Comparative Example 4

[0066] A method for preparing aluminum dihydrogen phosphate from lithium aluminum phosphate ore and comprehensive recovery of lithium salts is implemented according to the method described in Example 1, except that:

[0067] S2: The phosphate-lithium aluminum ore fraction obtained in S1 was leached at 90°C for 0.5h with nitric acid having a theoretical acid amount of 115%, a liquid-to-solid ratio of 3:1, and a leaching pressure of 0.2 MPa to obtain a leaching solution containing P, Al, and Li and a leaching residue mainly composed of silicon dioxide;

[0068] In this embodiment, the yield of lithium is 52.11%, the yield of aluminum is 42.19%, the yield of phosphorus is 32.99%, and the purity of aluminum dihydrogen phosphate is 41.11%.

[0069] Comparative Example 5

[0070] A method for preparing aluminum dihydrogen phosphate from lithium aluminum phosphate ore and comprehensive recovery of lithium salts is implemented according to the method described in Example 1, except that:

[0071] S2: The phosphate-lithium aluminum ore fraction obtained in S1 was leached at 160°C for 3h with hydrochloric acid having a theoretical acid amount of 115%, a liquid-to-solid ratio of 3:1, and a leaching pressure of 0.45 MPa to obtain a leaching solution containing P, Al, and Li and a leaching residue mainly composed of silicon dioxide;

[0072] In this embodiment, the yield of lithium is 62.11%, the yield of aluminum is 40.19%, the yield of phosphorus is 41.22%, and the purity of aluminum dihydrogen phosphate is 52.12%.

[0073] Comparative Example 6

[0074] A method for preparing aluminum dihydrogen phosphate from lithium aluminum phosphate ore and comprehensive recovery of lithium salts is implemented according to the method described in Example 1, except that:

[0075] S2: The phosphate-lithium aluminum ore fraction obtained in S1 was leached at 160°C for 3h with sulfuric acid containing 115% of the theoretical acid amount and a liquid-to-solid ratio of 3:1, and a leaching pressure of 0.45 MPa to obtain a leaching solution containing P, Al, and Li and a leaching residue mainly composed of silicon dioxide;

[0076] In this embodiment, the yield of lithium is 72.11%, the yield of aluminum is 59.23%, the yield of phosphorus is 55.77%, and the purity of aluminum dihydrogen phosphate is 71.23%.

[0077] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing aluminum dihydrogen phosphate from lithium aluminum phosphate ore and comprehensive recovery of lithium salts, characterized in that: include: Step S1, ball-milling the phosphate-lithium-aluminum ore to a certain particle size to obtain phosphate-lithium-aluminum ore powder; Step S2, leaching the phosphate-lithium-aluminum ore powder with nitric acid under pressure, and obtaining a leaching solution containing P, Al, and Li and a leaching residue mainly containing silicon dioxide after solid-liquid separation; Step S3, adjusting the pH of the leaching solution to obtain aluminum dihydrogen phosphate precipitate and a filtrate mainly composed of LiNO3, NaNO3, and KNO3; Step S4, adding Na2CO3 to the filtrate after chemical impurity removal and resin deep adsorption to precipitate Li2CO3 and lithium precipitation mother liquor; Step S5, returning the lithium precipitation mother liquor to step S3 for adjusting the pH of the leaching solution.

2. The method according to claim 1, characterized in that: In step S1, the particle size of the phosphate lithium aluminum ore powder is D90≤0.18mm; preferably D90≤0.045mm.

3. The method according to claim 1, characterized in that In step S2, the conditions for nitric acid pressure leaching are: the amount of nitric acid added is 80-150% of the theoretical amount, preferably 100-150%; the liquid-to-solid ratio is 1-5:1; the leaching temperature is 130°C-180°C; the leaching pressure is 0.3-0.7MPa; and the leaching time is 1-4h.

4. The method according to claim 1, characterized in that: In step S3, the lithium precipitation mother solution is used entirely when adjusting the pH of the leaching solution.

5. The method according to claim 1, characterized in that In step S3, the pH value of the leaching solution is adjusted to an end point of 1-3, the precipitation reaction temperature is 40-110° C., and the reaction time is 0.5-3 h.

6. The method according to claim 1, characterized in that In step S4, the mass of sodium carbonate used is 80-150% of the theoretical value of lithium precipitation.

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