Method for preparing high-purity aluminum phosphate and high-purity aluminum dihydrogen phosphate using lithium-extracted slag from lithium aluminum sulfate

Abstract

A method for preparing high-purity aluminum phosphate and high-purity aluminum dihydrogen phosphate using lithium-extracted slag from lithium phosphate alumina is disclosed. The lithium phosphate alumina slag is re-pulped and acid-leached with concentrated sulfuric acid to obtain a leached residue and an aluminum sulfate solution. The leached residue is washed to recover the aluminum phosphate; the aluminum sulfate solution is treated with a desulfurizer and a chelating agent, and then precipitated with alkaline solution to form aluminum phosphate dihydrate. The aluminum phosphate dihydrate is washed, dried, and calcined to obtain high-purity anhydrous aluminum phosphate that exceeds the group standard; the anhydrous aluminum phosphate is further dissolved in purified phosphoric acid to obtain high-purity aluminum dihydrogen phosphate. The present invention solves the problem of processing and utilizing lithium-extracted slag from lithium phosphate alumina and obtains high-value aluminum phosphate and aluminum dihydrogen phosphate, which can be widely used as fluxes in glass production, adhesives for ceramics or teeth, and as additives in materials such as emollients, fire retardant coatings, and conductive cements.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical material preparation, and specifically relates to a method for preparing high-purity aluminum phosphate exceeding group standards from lithium extraction slag of lithium aluminum sulfate and further obtaining high-purity aluminum dihydrogen phosphate, and recovering the aluminum phosphate in the lithium extraction slag. Background Art

[0002] With the development of new energy vehicles and energy storage, the demand for lithium resources is increasing. The current process for extracting lithium from lithium phosphate is generally to acidify and calcine the lithium phosphate ore with concentrated sulfuric acid. The calcined product is then leached with water, filtered, and the filtrate is used to extract lithium. The resulting lithium extraction slag is primarily composed of AlPO4 and has a high recycling value. However, the current treatment method for lithium extraction slag is to use excess sulfuric acid to leach out the phosphorus and aluminum in a single step. The sulfuric acid usage is as high as a sulfur-to-aluminum molar ratio of 2:1, resulting in high unit consumption and a high sulfate content in the product. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for preparing aluminum phosphate and aluminum dihydrogen phosphate that are superior to group standards by using lithium phosphate extraction slag from lithium aluminum phosphate, and to obtain aluminum phosphate and aluminum dihydrogen phosphate products with high market value by using the lithium extraction slag.

[0004] The technical solution adopted by the present invention is as follows:

[0005] The method for preparing high-purity aluminum phosphate and high-purity aluminum dihydrogen phosphate by using lithium phosphate extraction slag from lithium aluminum phosphate includes the following steps:

[0006] S1. Preparation of a spare acid leaching solution: Take lithium aluminum sulfate extracting slag and add water to make a slurry, then add an excess of 20% concentrated acid, heat to 70-90 ° C and react for 1-3h, filter and separate to obtain a spare acid leaching solution and acid leaching residue, add 3-5 times the amount of water to wash for 1-2h to obtain the leaching residue and the washing water;

[0007] S2 preparation of lithium slag slurry: lithium aluminum sulfate lithium slag slurry obtained by adding the slag washing water slurry obtained in step S1 to prepare a lithium slag slurry;

[0008] S3. Extraction of lithium slag primary acid leaching: The lithium slag slurry is added to half of the spare acid leaching solution obtained in step S1 or the secondary acid leaching solution obtained in the subsequent step S4, heated to 70-90 ° C for 1-3h, and a flocculant is added to separate the solid and liquid to obtain a primary acid leaching solution and a primary slag;

[0009] S4. Lithium slag secondary acid leaching: adding the remaining half of the spare acid leaching solution obtained in step S1 to the primary slag or the subsequent step S5 to obtain the tertiary acid leaching solution, heating to 70-90 ° C for 1-3h, adding a flocculant to separate the solid and liquid to obtain a secondary acid leaching solution and a secondary slag;

[0010] S5. Lithium slag tertiary acid leaching: Add concentrated acid to the secondary slag, raise the temperature to 70-90°C, react for 1-3 hours, and filter to separate the tertiary acid leaching solution and tertiary slag;

[0011] S6 washing: the tertiary slag is washed with 3-5 times water for 1-2h to obtain the leaching residue and the slag washing water;

[0012] S7 desulfurization: Steps S3-S6 were cycled three times, and the first acid extract obtained after the second step S3 was mixed, a desulfurizing agent was added to a pH of 1.8-2.2, the temperature was raised to 40-60 ° C for 1-3h, and the desulfurized extract was filtered to obtain a desulfurized extract;

[0013] S8. Preparation of aluminum phosphate: Add a chelating agent to the desulfurized solution, heat to 30-50 ° C and stir until completely dissolved, then add alkali solution to adjust the pH to 2.8-3.2, heat to 50-80 ° C and react for 1-2h, and filter to obtain an aluminum phosphate filter cake;

[0014] S9. Preparation of aluminum phosphate dihydrate: The aluminum phosphate filter cake was washed 3-5 times with pure water, and the washed cake was dried at 200-300 ° C for 2-4h to remove free water to obtain aluminum phosphate dihydrate;

[0015] S10. Preparation of high-purity anhydrous aluminum phosphate: drying aluminum phosphate dihydrate at 800-900°C for 2-4 hours to remove crystal water and sulfate, thereby obtaining high-purity anhydrous aluminum phosphate.

[0016] Furthermore, the high-purity anhydrous aluminum phosphate obtained in the above step S10 is added to purified phosphoric acid to dissolve, and after the solution becomes clear, it is filtered to obtain high-purity aluminum dihydrogen phosphate.

[0017] Furthermore, the purified phosphoric acid is phosphoric acid with a mass concentration of not less than 75%, and the amount of purified phosphoric acid added is 2.0-2.1 times the molar amount of anhydrous aluminum phosphate.

[0018] Furthermore, when adding water to the lithium phosphate aluminum slag for slurrying in step S1, the slag washing water from step S6 is used to return to prepare the lithium extraction slag slurry, and the slurry concentration is 50-70% solid content.

[0019] Furthermore, the flocculant used in steps S3 and S4 is 5%-10 wt.% polyacrylamide, and the added amount is 1-5‰ of the mass of the slurry.

[0020] Furthermore, the concentrated acid in step S5 is industrial sulfuric acid with a mass concentration of 98%, and the amount of concentrated acid added is based on a molar ratio of sulfur in sulfuric acid to aluminum in lithium extraction slag (0.8-1.1):1.

[0021] Furthermore, the washing water used in step S6 is deionized water with a resistivity of less than 15 μs / cm, and the amount of water used for each washing is 3 to 5 times the mass of the filter cake.

[0022] Furthermore, the desulfurizing agent in step S7 is one or both of calcium oxide and calcium hydroxide.

[0023] Furthermore, the chelating agent in step S8 is ethylenediaminetetraacetic acid or disodium ethylenediaminetetraacetic acid.

[0024] Furthermore, the alkali solution in step S8 is one of 5-10 wt.% sodium hydroxide, 5-10 wt.% sodium carbonate, and 10-15 wt.% ammonia water.

[0025] The present invention uses waste residue generated after lithium extraction from lithium aluminum phosphate and employs a three-stage acid leaching process, reducing the amount of acid and alkali used by 30%. This also reduces the need for subsequent washing with sulfate and sodium for aluminum phosphate, resulting in lower impurities in the aluminum phosphate and lowering production costs. Desulfurization and impurity removal further reduce impurities in the aluminum phosphate.

[0026] The high-purity aluminum phosphate and high-purity aluminum dihydrogen phosphate prepared by the present invention are both superior to the group standard. They can be used as flux in the glass production process, as adhesives for ceramics or teeth, and as additives to materials such as emollients, fire-retardant coatings, and conductive cements, and have good market application prospects. DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to the embodiments.

[0028] A method for preparing high-purity aluminum phosphate exceeding group standards by using lithium phosphate extraction slag from lithium aluminum phosphate and further preparing high-purity aluminum dihydrogen phosphate, the specific steps of which are as follows:

[0029] S1. Preparation of a spare acid leaching solution: Take lithium aluminum sulfate extracting slag and add water to prepare a solid content of 50-70% slurry, then press the sulfur in sulfuric acid and the aluminum in the lithium extracting slag in a molar ratio (1.2-1.5): 1 to add 98% concentrated sulfuric acid, warm to 70-90 ° C for 1-3h, filter and separate to obtain a spare acid leaching solution and acid leaching residue, add 3-5 times the amount of water to wash 1-2h to obtain the leaching residue and the washing water;

[0030] S2 preparation of lithium slag slurry: lithium aluminum sulfate lithium slag plus step S1 obtained by washing water or subsequent step S6 slag water slurry, prepared from lithium slag slurry;

[0031] S3. Extraction of lithium slag primary acid leaching: The lithium slag slurry was added to half of the spare acid leaching solution obtained in step S1 or the secondary acid leaching solution prepared in the subsequent step S4, and the temperature was raised to 70-90 ° C for 1-3h, and 5% to 10% polyacrylamide was added to the total mass of the slurry at 1-5‰, and the solid-liquid separation was performed to obtain a primary acid leaching solution and a primary slag;

[0032] S4. Extraction of lithium slag secondary acid leaching: adding the remaining half of the spare acid leaching solution obtained in step S1 to the primary slag or the tertiary acid leaching solution prepared in the subsequent step S5, heating to 70-90 ° C for 1-3h, adding 5% to 10% polyacrylamide of 1-5‰ of the total slurry mass, and separating the solid and liquid to obtain a secondary acid leaching solution and a secondary slag;

[0033] S5. Tertiary acid leaching of lithium slag: Add 98% concentrated sulfuric acid at a molar ratio of sulfur in sulfuric acid to aluminum in lithium slag (0.8-1.1):1 to the secondary slag, heat to 70-90°C, react for 1-3 hours, and filter to obtain a tertiary acid leaching solution and tertiary slag;

[0034] S6 washing: the three-stage slag plus 3-5 times the water washing 1-2h, to obtain the leaching residue and slag washing water, the slag washing water can be returned to step S2 pulping;

[0035] S7 desulfurization: Steps S3-S6 were cycled three times, and the first acid extract obtained after the second step S3 was mixed, a desulfurizing agent was added to a pH of 1.8-2.2, the temperature was raised to 40-60 ° C for 1-3h, and the desulfurized extract was filtered to obtain a desulfurized extract;

[0036] S8. Disodium EDTA was added to the desulfurized leaching solution in an amount of 1-1.4:1 molar ratio of disodium EDTA to iron in the acid leaching solution, and the mixture was heated to 30-50 ° C and stirred until completely dissolved. 5-10% sodium hydroxide or 5-10% sodium carbonate was then added to adjust the pH to 2.8-3.2, and the mixture was heated to 50-80 ° C for 1-2 h. The aluminum phosphate filter cake was filtered;

[0037] S9 Preparation of aluminum phosphate dihydrate: The aluminum phosphate filter cake was washed with pure water 3-5 times, the washing water temperature was controlled at 40-60 ℃, and the washing time was 0.5-1h / time; the washed cake was dried in an oven at 200-300 ℃ for 2-4h to obtain aluminum phosphate dihydrate;

[0038] S10. Preparation of high-purity anhydrous aluminum phosphate: Aluminum phosphate dihydrate is dried in a muffle furnace at 800-900°C for 2-4 hours to remove water of crystallization and sulfate groups, resulting in high-purity anhydrous aluminum phosphate that exceeds the group standard "T / ZJCX 0002-2022 Aluminum Phosphate";

[0039] S11. Preparation of high-purity aluminum dihydrogen phosphate: Anhydrous aluminum phosphate is further dissolved in purified phosphoric acid, wherein the purified phosphoric acid has a mass concentration of not less than 75%. The amount of purified phosphoric acid added is 2.0-2.1 times the molar amount of the anhydrous aluminum phosphate. After the solution becomes clear, high-purity aluminum dihydrogen phosphate is obtained. Example 1

[0040] A method for preparing high-purity aluminum phosphate and aluminum dihydrogen phosphate that exceeds group standards by using lithium phosphate extraction slag from lithium aluminum phosphate, comprising the following steps:

[0041] S1. Take 1000g of lithium aluminum sulfate extracting slag and add water to prepare a slurry with a solid content of 50%, then add 98% concentrated sulfuric acid at a molar ratio of 1.2:1 between sulfur in sulfuric acid and aluminum in lithium extracting slag, and heat to 70 ° C for 3h. The reaction was separated by filtration to obtain a spare acid leaching solution and acid leaching residue. The acid leaching residue was washed with 3 times water for 1h to obtain the leaching residue and the washing water;

[0042] S2 take 1000g lithium aluminum sulfate lithium slag plus step S1 slag water slurry, prepared from lithium slag slurry;

[0043] S3. The lithium slag slurry was added to half of the spare acid leaching solution obtained in step S1, heated to 70 ° C for 3h, 10% polyacrylamide was added to the total mass of the slurry 1‰, and the solid-liquid separation was performed to obtain a primary acid leaching solution and a primary slag;

[0044] S4. Add the other half of the spare acid leaching solution obtained in step S1 to the primary slag, heat to 70 ° C and react for 3h, add 1‰ of 10% polyacrylamide by mass of the total slurry, and separate the solid and liquid to obtain a secondary acid leaching solution for the secondary slag;

[0045] S5. Add 98% concentrated sulfuric acid in a molar ratio of 1.1:1 of sulfur in sulfuric acid and aluminum in lithium slag to the secondary slag, raise the temperature to 70 ° C and react for 3h, filter and separate to obtain a tertiary acid leaching solution of tertiary slag;

[0046] S6. The tertiary slag was washed with 3 times the amount of water for 2h to obtain the remaining slag and slag washing water, and the slag washing water was returned to step S2 for pulping;

[0047] S7. Steps S3-S6 were cycled three times, and the primary acid extract obtained in step S3 was taken two times, mixed, and 10% calcium hydroxide was added to pH 1.8, heated to 40 ° C for 3 h, and filtered to obtain a desulfurized extract;

[0048] S8. Disodium EDTA was added to the desulfurized leaching solution in an amount of 1.4:1 molar ratio of disodium EDTA to iron in the acid leaching solution, heated to 30 ° C and stirred until completely dissolved, then 5% sodium hydroxide was added to adjust the pH to 2.8, heated to 50 ° C and reacted for 2h, and filtered to obtain an aluminum phosphate filter cake;

[0049] S9. The aluminum phosphate filter cake was washed three times with pure water, the washing water temperature was controlled at 60 ° C, and the washing time was 0.5h / time; the washed cake was dried in an oven at 200 ° C for 4h to obtain aluminum phosphate dihydrate;

[0050] S10. Drying aluminum phosphate dihydrate in a muffle furnace at 800°C for 4 h to remove water of crystallization and sulfate groups yields high-purity anhydrous aluminum phosphate that exceeds the group standard "T / ZJCX 0002-2022 Aluminum Phosphate";

[0051] S11. Anhydrous aluminum phosphate is further added to purified phosphoric acid to dissolve, wherein the purified phosphoric acid has a mass concentration of not less than 75% and the added amount is 2.0 times the molar amount of anhydrous aluminum phosphate. After the solution becomes clear, high-purity aluminum dihydrogen phosphate is obtained. Example 2

[0052] A method for preparing high-purity aluminum phosphate and high-purity aluminum dihydrogen phosphate that exceed group standards by using lithium phosphate extraction slag from lithium aluminum phosphate, comprising the following steps:

[0053] S1. Take 1000g of lithium aluminum sulfate extracting slag and add water to prepare a solid content of 60% slurry, then press sulfur in sulfuric acid and aluminum in lithium extracting slag in a molar ratio of 1.4: 1, add 98% concentrated sulfuric acid, warm to 80 ° C for 2h, filter and separate to obtain a spare acid leaching solution and acid leaching residue, the acid leaching residue was washed with 3 times water for 1h to obtain the leaching residue and the washing water;

[0054] S2 take 1000g lithium aluminum sulfate extracting lithium slag plus pre-sequence production step S6 obtained in the slag washing water, prepared to extract lithium slag slurry;

[0055] S3. The lithium slag slurry was added to the secondary acid leaching solution obtained in the previous step S4 of the production process, and the reaction temperature was raised to 80 ° C for 2h. 7.5% polyacrylamide was added to the total mass of the slurry at 2.5‰, and the solid-liquid separation was performed to obtain a primary acid leaching solution and a primary slag;

[0056] S4 was added to the first slag in the previous step S5 obtained in the production of the three-stage acid leaching solution, heated to 80 ℃ reaction 2h, added 2.5‰ of the total slurry mass of 7.5% polyacrylamide, solid-liquid separation to obtain a secondary acid leaching solution secondary slag;

[0057] S5. 98% concentrated sulfuric acid was added to the secondary slag in a molar ratio of 1:1 between sulfur in sulfuric acid and aluminum in the lithium slag, and the temperature was raised to 80 ° C for 2 h, and the tertiary acid leaching solution was separated by filtration to obtain the tertiary slag;

[0058] S6. The tertiary slag was washed with 4 times the amount of water for 1.5h to obtain the remaining slag and slag washing water, and the slag washing water was returned to step S2 for pulping;

[0059] S7. Steps S3-S6 were cycled three times, and the primary acid extract obtained in step S3 was taken two times, mixed, and 15% calcium hydroxide was added to pH 2.0, heated to 50 ° C for 2 h, and filtered to obtain a desulfurized extract;

[0060] S8. Disodium EDTA was added to the desulfurized leaching solution in an amount of 1.2:1 molar ratio of disodium EDTA and iron in the acid leaching solution, heated to 40 ° C and stirred until completely dissolved, then 5% sodium carbonate was added to adjust the pH to 3.0, heated to 65 ° C and reacted for 1.5h, and filtered to obtain an aluminum phosphate filter cake;

[0061] S9. The aluminum phosphate filter cake was washed four times with pure water, the washing water temperature was controlled at 50 ° C, and the washing time was 0.75h / time; the washed cake was dried in an oven at 250 ° C for 3h to obtain aluminum phosphate dihydrate;

[0062] S10. Dry the aluminum phosphate dihydrate in a muffle furnace at 850°C for 3 h to remove the crystal water and sulfate, obtaining high-purity anhydrous aluminum phosphate that exceeds the group standard;

[0063] S11. Anhydrous aluminum phosphate is further added to purified phosphoric acid to dissolve, wherein the purified phosphoric acid has a mass concentration of not less than 75% and the added amount is 2.05 times the molar amount of the anhydrous aluminum phosphate. After the solution becomes clear, high-purity aluminum dihydrogen phosphate is obtained. Example 3

[0064] A method for preparing high-purity aluminum phosphate and high-purity aluminum dihydrogen phosphate that exceed group standards from lithium-ion slag extracted from lithium aluminum sulfate, comprising the following steps:

[0065] S1. Take 1000g of lithium aluminum sulfate extracting slag and add water to prepare a slurry with a solid content of 70%, then add 98% concentrated sulfuric acid at a molar ratio of 1.5:1 between sulfur in sulfuric acid and aluminum in lithium extracting slag, and heat to 90 ° C for 1h. The reaction was separated by filtration to obtain a spare acid leaching solution and acid leaching residue. The acid leaching residue was washed with 3 times water for 1h to obtain the leaching residue and the washing water;

[0066] S2 take 1000g lithium aluminum sulfate lithium slag plus step S1 slag water slurry, prepared from lithium slag slurry;

[0067] S3. The lithium slag slurry was added to the secondary acid leaching solution obtained in step S4, and the temperature was raised to 90 ° C for 1h, 5% polyacrylamide was added to the total mass of the slurry by 5‰, and the solid-liquid separation was performed to obtain a primary acid leaching solution and a primary slag;

[0068] S4. Add the three-stage acid leaching solution obtained in step S5 to the primary slag, heat to 90 ° C and react for 1h, add 5‰ of 5% polyacrylamide by mass of the total slurry, and separate the solid and liquid to obtain a secondary acid leaching solution for the secondary slag;

[0069] S5. Add 98% concentrated sulfuric acid to the secondary slag in a molar ratio of 0.8:1 of sulfur in sulfuric acid and aluminum in lithium slag, raise the temperature to 90 ° C and react for 1h, filter and separate to obtain a tertiary acid leaching solution of tertiary slag;

[0070] S6. The tertiary slag was washed with 5 times the amount of water for 1 hour to obtain the remaining slag and slag washing water, and the slag washing water was returned to step S2 for pulping;

[0071] S7. Steps S3-S6 were cycled three times, and the primary acid extract obtained in step S3 was taken two times, mixed, and 20% calcium hydroxide was added to pH 2.2, heated to 60 ° C for 1 h, and filtered to obtain a desulfurized extract;

[0072] S8. Disodium EDTA was added to the desulfurized leaching solution in an amount of 1:1 molar ratio of disodium EDTA to iron in the acid leaching solution, heated to 50 ° C and stirred until completely dissolved, then 10% sodium carbonate was added to adjust the pH to 3.2, heated to 80 ° C and reacted for 1 h, and filtered to obtain an aluminum phosphate filter cake;

[0073] S9. The aluminum phosphate filter cake was washed 5 times with pure water, the washing water temperature was controlled at 40 ° C, and the washing time was 1h / time; the washed cake was dried in an oven at 300 ° C for 2h to obtain aluminum phosphate dihydrate;

[0074] S10. Dry the aluminum phosphate dihydrate in a muffle furnace at 900°C for 2 h to remove the crystal water and sulfate, obtaining high-purity anhydrous aluminum phosphate that exceeds the group standard;

[0075] S11. Anhydrous aluminum phosphate is further added to purified phosphoric acid to dissolve, wherein the purified phosphoric acid has a mass concentration of not less than 75% and the added amount is 2.1 times the molar amount of anhydrous aluminum phosphate. After the solution becomes clear, high-purity aluminum dihydrogen phosphate is obtained.

[0076] The analytical indicators of the lithium extraction slag used in the above examples and the resulting high-purity anhydrous aluminum phosphate are shown in Table 1; the analytical indicators of the resulting high-purity aluminum dihydrogen phosphate are shown in Table 2. Table 3 is a comparison table of the indicator values ​​of the T / ZJCX 0002-2022 aluminum phosphate group standard and Example 1.

[0077] Table 1 Analysis indexes of lithium extraction slag and anhydrous aluminum phosphate

[0078] index Lithium extraction slag Example 1 Example 2 Example 3 Moisture / % 0.92 0.30 0.25 0.22 pH 4.2 5.4 5.6 5.7 <![CDATA[P2O5 / %]]> 43.08 54.82 54.53 54.87 <![CDATA[Al2O3 / %]]> 33.55 39.46 39.44 39.81 Ba / ppm 109.5 13.3 14.3 13.4 Ca / ppm 5147 183.7 194.4 213.2 Cd / ppm 0.8 0.3 0.4 0.5 Mg / ppm 360.3 9.0 10.8 12.7 Na / ppm 1287 251 247 307 K / ppm 2511 41.2 39.5 38.6 Fe / ppm 5962 518 496 523 Cr / ppm 83.7 10.4 11.4 12.3 Cu / ppm 19.6 4.6 5.1 6.6 Zn / ppm 19.1 3.6 4.5 5.5 Mn / ppm 55.2 11.4 10.6 13.1 Ni / ppm 34.8 1.3 1.7 1.9 Ti / ppm 2516 249 274 257 <![CDATA[SO4 2- / ppm]]> 28700 772 814 695

[0079] Table 2 Analysis indexes of aluminum dihydrogen phosphate

[0080] index Example 1 Example 2 Example 3 Moisture / % 0.30 0.25 0.22 <![CDATA[P2O5 / %]]> 34.95 34.77 34.98 <![CDATA[Al2O3 / %]]> 12.50 12.49 12.61 Ba / ppm 4.4 4.8 4.5 Ca / ppm 61.1 64.7 70.9 Cd / ppm 0.1 0.1 0.2 Mg / ppm 3.0 3.6 4.2 Na / ppm 83.5 82.2 102.1 K / ppm 13.7 13.1 12.8 Fe / ppm 172.3 165.0 174.0 Cr / ppm 3.5 3.8 4.1 Cu / ppm 1.5 1.7 2.2 Zn / ppm 1.2 1.5 1.8 Mn / ppm 3.8 3.5 4.4 Ni / ppm 0.4 0.6 0.6 Ti / ppm 82.8 91.1 85.5 <![CDATA[SO4 2- / ppm]]> 256.8 270.7 231.2

[0081] Table 3 Comparison of index values ​​of the group standard "T / ZJCX 0002-2022 Aluminum Phosphate" and Example 1

[0082] project Group standard index value Example 1 Water w / % ≤5 0.3 pH 5-7 5.4 <![CDATA[Phosphorus pentoxide (P2O5) w / %]]> 30-48 54.82 <![CDATA[Aluminum Oxide (Al2O3) w / %]]> 15-35 39.46 Mercury (Hg) w / % ≤0.003 Not detected Arsenic (As) w / % ≤0.003 Not detected Selenium (Se)w / % ≤0.003 Not detected Manganese (Mn) w / % ≤0.1 0.00114 Nickel (Ni)w / % ≤0.05 0.00013 Copper (Cu) w / % ≤0.1 0.00046 Zinc (Zn) w / % ≤0.1 0.00036 Lead (Pb) w / % ≤0.003 Not detected Chromium (Cr) w / % ≤0.05 0.00104 Cadmium (Cd)w / % ≤0.003 0.00003

[0083] In the table above, w / % = 1x10 4 ppm

[0084] As can be seen from the table, the aluminum phosphate prepared by the present invention has higher purity and lower harmful impurities than the group standard. Furthermore, the raw material cost of the traditional aluminum sulfate + phosphoric acid + alkali synthesis process is approximately 10,300 yuan / ton, while the raw material cost of the present invention is approximately 6,100 yuan / ton, a 40% cost reduction, making it more competitive in the market.

[0085] Craftsmanship Prices of main raw materials Raw material costs Cost reduction Aluminum sulfate + phosphoric acid + alkali Aluminum sulfate 1,000 yuan / ton 55% crude phosphoric acid 5,000 yuan / ton Soda ash 2,500 yuan / ton 10300 Lithium extraction slag + sulfuric acid + alkali Lithium slag 3000 yuan / ton Sulfuric acid 600 yuan / ton Soda ash 2500 yuan / ton 6100 40%

[0086] Unless otherwise specified, all percentages described in the present invention are by mass.

[0087] The above embodiments are only some specific embodiments of the present invention, and are not intended to limit the present invention. Any modification, deformation, replacement, and improvement of the embodiments made by those skilled in the art without departing from the scope of protection of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing high-purity aluminum phosphate and high-purity aluminum dihydrogen phosphate by using lithium phosphate slag extracted from lithium aluminum phosphate, characterized in that: The following steps are involved: S1. Preparation of a spare acid leaching solution: Take lithium aluminum sulfate extracting slag and add water to make a slurry, then add an excess of 20% concentrated acid, heat to 70-90 ° C and react for 1-3h, filter and separate to obtain a spare acid leaching solution and acid leaching residue, add 3-5 times the amount of water to wash for 1-2h to obtain the leaching residue and the washing water; S2 preparation of lithium slag slurry: lithium aluminum sulfate lithium slag slurry obtained by adding the slag washing water slurry obtained in step S1 to prepare a lithium slag slurry; S3. Extraction of lithium slag primary acid leaching: The lithium slag slurry is added to half of the spare acid leaching solution obtained in step S1 or the secondary acid leaching solution obtained in the subsequent step S4, heated to 70-90 ° C for 1-3h, and a flocculant is added to separate the solid and liquid to obtain a primary acid leaching solution and a primary slag; S4. Lithium slag secondary acid leaching: adding the remaining half of the spare acid leaching solution obtained in step S1 to the primary slag or the subsequent step S5 to obtain the tertiary acid leaching solution, heating to 70-90 ° C for 1-3h, adding a flocculant to separate the solid and liquid to obtain a secondary acid leaching solution and a secondary slag; S5. Lithium slag tertiary acid leaching: Add concentrated acid to the secondary slag, heat to 70-90°C, react for 1-3 hours, and filter to separate the tertiary acid leaching solution and tertiary slag; S6 washing: the tertiary slag is washed with 3-5 times water for 1-2h to obtain the leaching residue and the slag washing water; S7 desulfurization: Steps S3-S6 were cycled three times, and the first acid extract obtained after the second step S3 was mixed, a desulfurizing agent was added to a pH of 1.8-2.2, the temperature was raised to 40-60 ° C for 1-3h, and the desulfurized extract was filtered to obtain a desulfurized extract; S8. Preparation of aluminum phosphate: Add a chelating agent to the desulfurized solution, heat to 30-50 ° C and stir until completely dissolved, then add alkali solution to adjust the pH to 2.8-3.2, heat to 50-80 ° C and react for 1-2h, and filter to obtain an aluminum phosphate filter cake; S9. Preparation of aluminum phosphate dihydrate: The aluminum phosphate filter cake was washed 3-5 times with pure water, and the washed cake was dried at 200-300 ° C for 2-4h to remove free water to obtain aluminum phosphate dihydrate; S10. Preparation of high-purity anhydrous aluminum phosphate: drying aluminum phosphate dihydrate at 800-900°C for 2-4 hours to remove crystal water and sulfate, thereby obtaining high-purity anhydrous aluminum phosphate.

2. The method for preparing high-purity aluminum phosphate and high-purity aluminum dihydrogen phosphate by using lithium phosphate extracting slag from lithium aluminum phosphate according to claim 1, wherein: The high-purity anhydrous aluminum phosphate obtained in step S10 is added to purified phosphoric acid and dissolved. After the solution becomes clear, it is filtered to obtain high-purity aluminum dihydrogen phosphate.

3. The method for preparing high-purity aluminum phosphate and high-purity aluminum dihydrogen phosphate by using lithium phosphate extracting slag according to claim 2, characterized in that: The purified phosphoric acid is phosphoric acid having a mass concentration of not less than 75%, and the amount of purified phosphoric acid added is 2.0-2.1 times the molar amount of anhydrous aluminum phosphate.

4. The method for preparing high-purity aluminum phosphate and high-purity aluminum dihydrogen phosphate by using lithium phosphate extracting slag according to claim 1, characterized in that: In step S1, lithium aluminum sulfate slag is added with water to prepare slurry, and the slag washing water of step S6 is used to return to prepare lithium slag slurry, and the slurry concentration is 50-70% solid content.

5. The method for preparing high-purity aluminum phosphate and high-purity aluminum dihydrogen phosphate by using lithium phosphate extracting slag from lithium aluminum phosphate according to claim 1, characterized in that: The flocculant used in steps S3 and S4 is 5%-10wt.% polyacrylamide, and the added amount is 1-5‰ of the slurry mass.

6. The method for preparing high-purity aluminum phosphate and high-purity aluminum dihydrogen phosphate by using lithium phosphate extracting slag from lithium aluminum phosphate according to claim 1, characterized in that: The concentrated acid in step S5 is industrial sulfuric acid with a mass concentration of 98%, and the amount of concentrated acid added is based on the molar ratio of sulfur in sulfuric acid to aluminum in lithium extraction slag (0.8-1.1):

1.

7. The method for preparing high-purity aluminum phosphate and high-purity aluminum dihydrogen phosphate by using lithium phosphate extracting slag according to claim 1, characterized in that: The washing water used in step S6 is deionized water with a resistivity of less than 15 μs / cm, and the amount of water used for each washing is 3 to 5 times the mass of the filter cake.

8. The method for preparing high-purity aluminum phosphate and high-purity aluminum dihydrogen phosphate by using lithium phosphate extracting slag from lithium aluminum phosphate according to claim 1, characterized in that: The desulfurizing agent in step S7 is one or both of calcium oxide and calcium hydroxide.

9. The method for preparing high-purity aluminum phosphate and high-purity aluminum dihydrogen phosphate by using lithium phosphate extracting slag from lithium aluminum phosphate according to claim 1, characterized in that: The chelating agent described in step S8 is ethylenediaminetetraacetic acid or disodium ethylenediaminetetraacetic acid.

10. The method for preparing high-purity aluminum phosphate and high-purity aluminum dihydrogen phosphate by using lithium phosphate extracting slag according to claim 1, characterized in that: The alkali solution in step S8 is one of 5-10 wt.% sodium hydroxide, 5-10 wt.% sodium carbonate, and 10-15 wt.% ammonia water.