Method for comprehensively utilizing calcium collophanite and associated elements thereof

Abstract

The invention provides a method for comprehensively utilizing calcium collophanite and associated elements thereof, which comprises the following steps: S1, carrying out lactic acid acidolysis treatment on collophanite to obtain phosphate concentrate and mixed filtrate I; s2, crystallizing and decalcifying the mixed filtrate I circulated for multiple times in the S1 by using sulfuric acid to obtain calcium sulfate dihydrate and a mixed filtrate II; s3, performing membrane treatment on the mixed filtrate II in the S2, so that lactic acid molecules can penetrate through a nanofiltration membrane and intercept SO2-4 and Mg < 2 + > to obtain clear liquid and concentrated water; and S4, adding ammonia water into the concentrated water under a heating condition to precipitate and remove magnesium, so as to obtain a magnesium hydroxide solid and a filtrate III. And S5, concentrating the filtrate III, dissolving with alcohol, and adding acetone to promote crystallization to obtain an ammonium lactate solid. According to the method, carbonate impurities are decomposed by adopting lactic acid, then high-quality gypsum and magnesium hydroxide are prepared step by step, and calcium, magnesium and phosphorus elements are comprehensively utilized.

Description

Technical Field

[0001] The invention belongs to the field of mineral processing, and in particular relates to a method for comprehensive utilization of calcareous collophanite and its associated elements. Background Art

[0002] Calcareous collophanite refers to an aggregate of calcium fluorophosphate as the main component and a small amount of carbonate gangue minerals. The carbonate gangue minerals mainly include dolomite and calcite, among which dolomite is a hydrochloride complex salt composed of calcium carbonate and magnesium carbonate.

[0003] Most of the collophosphates containing carbonate gangue minerals cannot be used directly for processing and production, and need to be beneficiated and impurities removed before they can be used. This type of phosphate ore is generally removed by reverse flotation, and fatty acid salts are used as collectors for reverse flotation of dolomite and calcite. The concentrate obtained by flotation is used to produce phosphoric acid and phosphates, while the tailings rich in calcium and magnesium are stored in tailings ponds, which not only occupies a large amount of land resources, but also pollutes the environment, and also causes a waste of calcium and magnesium resources.

[0004] Lactic acid is a monobasic organic weak acid that can selectively decompose carbonate minerals without decomposing phosphate ore, thereby achieving phosphorus enrichment. Patent CN117645537A first calcined calcareous phosphate tailings and then gradually prepared lactates of elements such as calcium, magnesium, iron and aluminum, but the high-temperature decomposition consumes a lot of energy, which is not conducive to industrial production.

[0005] The present invention uses lactic acid to decompose carbonate impurities under low temperature conditions, and then extracts calcium, magnesium and phosphorus elements step by step, thereby achieving no tailings discharge and achieving the purpose of comprehensive utilization of associated elements. Summary of the invention

[0006] The invention provides a method for comprehensive utilization of calcareous collophosphate and its associated elements. The method has the advantages of simple process flow, low energy consumption, significant improvement of concentrate quality, high utilization rate of associated elements, high quality of by-products, and the like.

[0007] The technical solution of the present invention is a method for comprehensive utilization of calcareous collophanite and its associated elements, comprising the following steps: S1. Grind qualified calcareous collophanite and remove impurities with lactic acid. Lactic acid can selectively decompose dolomite and calcite in collophanite without decomposing apatite. This process can not only effectively remove impurities, but also enrich phosphorus, and finally obtain low-magnesium phosphate concentrate and mixed filtrate I.

[0008] S1 Calcium collophanite P 2 O 5 The grade is 3~35%, and the MgO grade is 1.0~20.0%.

[0009] The amount of lactic acid in S1 is 5-40% of the mass of the reaction slurry, and is added in a concentration of 2-20%.

[0010] The acid removal of impurities in S1 can be divided into one-step or two-step removal of impurities, the reaction temperature of the impurity removal is 20-80° C., and the reaction liquid-to-solid ratio is 3:1-10:1.

[0011] The magnesium content of the low-magnesium phosphate concentrate obtained by acid removal of magnesium in S1 is ≤0.2%.

[0012] The low-magnesium phosphate concentrate described in S1 is subjected to 4 to 8 countercurrent washings with clean water, and the washing water from the first washing is used to prepare an organic acid solution or to adjust the liquid-solid ratio of an acid hydrolysis operation.

[0013] The lactic acid in the filtrate containing lactic acid and lactate obtained by the solid-liquid separation in S1 is not completely consumed, and still needs to be returned to the next round of magnesium leaching operation, and enters the next step after 2 to 8 cycles.

[0014] In S1, lactic acid decomposes dolomite and calcite to generate calcium lactate, magnesium lactate, carbon dioxide and water. The specific chemical reaction equations involved are as follows: 2CH 3 CHOHCOOH + CaCO 3 = Ca(CH 3 CHOHCOO 2 + H 2 O + CO 2 2CH 3 CHOHCOOH + MgCO 3 = Mg(CH 3 CHOHCOO 2 + H 2 O + CO 2 In some embodiments, lactate is also added during the lactic acid hydrolysis process, and the lactate may be sodium L-lactate.

[0015] S2, the magnesium removal filtrate recycled multiple times in S1 is treated with crystallization and decalcification with sulfuric acid. The filtrate contains unconsumed lactic acid, calcium lactate, and magnesium lactate. During the sulfuric acid decalcification process, Ca 2+ It reacts with sulfate to generate calcium sulfate dihydrate, and the solid-liquid separation produces dihydrate gypsum and mixed filtrate II, and the filtrate enters the next step.

[0016] The chemical reaction equations mainly involved in the decalcification of sulfuric acid in S2 are as follows: Ca(CH 3 CHOHCOO 2 + H 2 SO 4 + 2H2 O = 2CH 3 CHOHCOOH + CaSO 4 ·2H 2 O S2 The agent for crystallization decalcification is sulfuric acid, and the added sulfuric acid is configured to a concentration of 20% to 70%. The temperature for crystallization decalcification is from the temperature at which lactic acid removes magnesium to room temperature.

[0017] The crystallization decalcification described in S2 can not only obtain lactic acid by using a strong acid to produce a weak acid, but also prepare high-purity and high-white dihydrate gypsum from the calcium element in the carbonate gangue mineral.

[0018] The grade of the dihydrate gypsum obtained in S2 is ≥98%, and the whiteness is ≥97%.

[0019] In the crystallization decalcification process of S2, ammonium oxalate is used as an indicator to determine the Ca content in the solution 2+ Is the precipitation complete? If Ca 2+ If the reaction is not complete, white calcium oxalate precipitate will be generated with oxalate ions. Barium chloride is used as an indicator to determine whether excessive sulfuric acid is added to the solution. If sulfuric acid is not added excessively, adding the filtrate after decalcification to the barium chloride solution will not produce white barium sulfate precipitate.

[0020] S3. The filtrate obtained in S2 is treated with a nanofiltration membrane. Smaller lactic acid molecules can pass through the nanofiltration membrane, while larger sulfate and magnesium ions are retained to obtain clear water and concentrated water.

[0021] The nanofiltration membrane used in the membrane treatment process in S3 is a nanofiltration membrane greater than or equal to 300D, and only one membrane treatment is adopted, and the obtained clear liquid is used for acid removal of magnesium in S1.

[0022] The lactic acid molecules described in S3 can completely pass through the nanofiltration membrane greater than or equal to 300D, sulfate and Mg 2+ The retention rate is >95%, which can efficiently separate and recover lactic acid.

[0023] S4, precipitate and recover magnesium in concentrated water, heat the concentrated water obtained in S3 and add ammonia water to precipitate the Mg released by acid decomposition 2 + , magnesium hydroxide precipitate is obtained.

[0024] The chemical reaction equations mainly involved in the recovery of magnesium by S4 ammonia precipitation are as follows: Mg(CH 3 CHOHCOO 2 + 2NH 3 + 2H 2 O = Mg(OH) 2 + 2NH 4 CH3 CHOHCOO S4 Mg 2+ The precipitant is ammonia water, which is added slowly dropwise until no white precipitate is produced in the solution.

[0025] The ammonia precipitation of Mg 2+ It can be carried out at 40~70℃, or the magnesium-containing solution can be heated and concentrated first, and then Mg is precipitated. 2+ , which can reduce the consumption of ammonia.

[0026] The magnesium hydroxide produced by the precipitation is subjected to solid-liquid separation to obtain magnesium hydroxide solid and filtrate III. The magnesium hydroxide solid is washed with clean water, dehydrated and dried at 150-250°C.

[0027] The purity of the magnesium hydroxide is greater than 99%, and the CaO content is less than 0.2%.

[0028] The filtrate III is heated and concentrated. The filtrate mainly consists of ammonia water, ammonium ions and lactate ions. Excess water is evaporated by heating, and the alcohol solution is concentrated. Then acetone is added to promote the crystallization of ammonium lactate.

[0029] The filtrate III is heated and concentrated at a temperature of 100° C. until the water content is less than 10%.

[0030] The ammonium lactate is easily soluble in alcohol. The concentrated filtrate III is dissolved in alcohol, and then acetone is added to the dissolved solution to precipitate ammonium lactate crystals. DETAILED DESCRIPTION

[0031] The embodiments of the present invention will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention.

[0032] Example 1 P 2 O 5 The calcareous collophosphate ore with a grade of 28.17% and a MgO grade of 2.11% is treated by the method of the present invention.

[0033] The ground slurry was transferred to the reactor and lactic acid was added to remove impurities. The amount was 25% of the slurry mass, the reaction temperature was 60°C, the liquid-solid ratio was 6:1, and a mixed filtrate I of phosphate concentrate with a magnesium content of 0.10% was obtained.

[0034] Sulfuric acid with a concentration of 35% was added to the mixed filtrate I for crystallization and decalcification to obtain high-purity and high-white phosphogypsum and mixed filtrate II, with a gypsum grade of 99.14% and a whiteness of 97.38%.

[0035] The mixed filtrate II is treated with a 300D nanofiltration membrane to obtain clean water and concentrated water. The clean water, which is mainly composed of lactic acid, is returned to the acid removal magnesium operation.

[0036] Ammonia water was slowly added to the concentrated water until no white precipitate was produced to obtain magnesium hydroxide precipitate. The magnesium hydroxide solid was washed with clean water, dehydrated and dried at 200°C. The purity was 99.31% and the CaO content was 0.16%.

[0037] After shrinking with water, it is dissolved in 80% ethanol, and then acetone is added to promote the crystallization of ammonium lactate to obtain calcium lactate with a purity of 99.8%.

[0038] Example 2 P 2 O 5 The calcareous phosphate tailings with a grade of 5.25% and a MgO grade of 15.49% are treated by the method of the present invention.

[0039] The slurry was transferred to the reactor and lactic acid was added for two-stage acid removal. The dosage of the first stage was 30% of the slurry mass, the reaction temperature was 70°C, the liquid-solid ratio was 6:1, and the amount of lactic acid added in the second stage was 30% of the first stage to obtain a mixed filtrate I of phosphate concentrate with a magnesium content of 0.18%.

[0040] Sulfuric acid with a concentration of 50% is added to the mixed filtrate I for crystallization and decalcification to obtain high-purity and high-white phosphogypsum and mixed filtrate II, with a gypsum grade of 99.45% and a whiteness of 97.13%.

[0041] The mixed filtrate II is treated with a 300D nanofiltration membrane to obtain clean water and concentrated water. The clean water, which is mainly composed of lactic acid, is returned to the acid removal magnesium operation.

[0042] Ammonia water was slowly added to concentrated water until no white precipitate was produced to obtain magnesium hydroxide precipitate. The magnesium hydroxide solid was washed with clean water, dehydrated and dried at 200°C. The purity was 99.45% and the CaO content was 0.18%.

[0043] After shrinking with water, it is dissolved in 80% ethanol, and then acetone is added to promote the crystallization of ammonium lactate to obtain calcium lactate with a purity of 99.4%.

[0044] Example 3 P 2 O 5 The siliceous-calcium collophanite with a grade of 30.56% and a MgO grade of 1.55% is treated by the method of the present invention, wherein the main calcic gangues are calcite and dolomite, and the siliceous gangues are quartz and feldspar.

[0045] The ground slurry was transferred to the reactor and lactic acid was added to remove impurities. The amount was 10% of the slurry mass, the reaction temperature was 50°C, the liquid-solid ratio was 6:1, and a mixed filtrate I of phosphate concentrate with a magnesium content of 0.11% was obtained.

[0046] Sulfuric acid with a concentration of 30% is added to the mixed filtrate I for crystallization and decalcification to obtain high-purity and high-white phosphogypsum and mixed filtrate II, with a gypsum grade of 99.05% and a whiteness of 97.15%.

[0047] The mixed filtrate II is treated with a 300D nanofiltration membrane to obtain clean water and concentrated water. The clean water, which is mainly composed of lactic acid, is returned to the acid removal magnesium operation.

[0048] Ammonia water was slowly added to the concentrated water until no white precipitate was produced to obtain magnesium hydroxide precipitate. The magnesium hydroxide solid was washed with clean water, dehydrated and dried at 180°C. The purity was 99.17% and the CaO content was 0.13%.

[0049] After shrinking with water, it is dissolved in 80% ethanol, and then acetone is added to promote the crystallization of ammonium lactate to obtain calcium lactate with a purity of 99.2%.

[0050] Example 4 P 2 O 5 The calcareous collophosphate ore with a grade of 27.32% and a MgO grade of 4.45% is treated by the method of the present invention.

[0051] The slurry was transferred to a reactor and lactic acid was added to remove impurities. The amount was 30% of the slurry mass, the reaction temperature was 70°C, and the liquid-solid ratio was 6:1 to obtain a mixed filtrate I of phosphate concentrate with a magnesium content of 0.18%.

[0052] Sulfuric acid with a concentration of 40% is added to the mixed filtrate I for crystallization and decalcification to obtain high-purity and high-white phosphogypsum and mixed filtrate II, with a gypsum grade of 99.65% and a whiteness of 97.44%.

[0053] The mixed filtrate II is treated with a 300D nanofiltration membrane to obtain clean water and concentrated water. The clean water, which is mainly composed of lactic acid, is returned to the acid removal magnesium operation.

[0054] Ammonia water was slowly added to concentrated water until no white precipitate was produced to obtain magnesium hydroxide precipitate. The magnesium hydroxide solid was washed with clean water, dehydrated and dried at 200°C. The purity was 99.74% and the CaO content was 0.10%.

[0055] After shrinking with water, it is dissolved in 80% ethanol, and then acetone is added to promote the crystallization of ammonium lactate to obtain calcium lactate with a purity of 99.7%.

[0056] Example 5 P 2 O5 The calcareous phosphate tailings with a grade of 20.25% and a MgO grade of 9.59% are treated by the method of the present invention.

[0057] First, lactic acid was added for two-stage acid removal. The dosage of the first stage was 25% of the slurry mass, the reaction temperature was 70°C, the liquid-solid ratio was 6:1, and the amount of lactic acid added in the second stage was 15% of that in the first stage to obtain a mixed filtrate I of phosphate concentrate with a magnesium content of 0.15%.

[0058] Sulfuric acid with a concentration of 45% is added to the mixed filtrate I for crystallization and decalcification to obtain high-purity and high-white phosphogypsum and mixed filtrate II, with a gypsum grade of 99.64% and a whiteness of 98.45%.

[0059] The mixed filtrate II is treated with a 300D nanofiltration membrane to obtain clean water and concentrated water. The clean water, which is mainly composed of lactic acid, is returned to the acid removal magnesium operation.

[0060] Ammonia water was slowly added to concentrated water until no white precipitate was produced to obtain magnesium hydroxide precipitate. The magnesium hydroxide solid was washed with clean water, dehydrated and dried at 200°C. The purity was 99.89% and the CaO content was 0.14%.

[0061] After shrinking with water, it is dissolved in 80% ethanol, and then acetone is added to promote the crystallization of ammonium lactate to obtain calcium lactate with a purity of 99.5%.

[0062] Example 6 P 2 O 5 The calcareous collophosphate ore with a grade of 28.17% and a MgO grade of 2.11% is treated by the method of the present invention.

[0063] The ground slurry was transferred to the reactor and lactic acid and sodium L-lactate were added to remove impurities. The amount of lactic acid was 24% of the slurry mass, and the amount of sodium L-lactate was 1%. The reaction temperature was 60°C, and the liquid-solid ratio was 6:1 to obtain a mixed filtrate I of phosphate concentrate with a magnesium content of 0.02%.

[0064] Sulfuric acid with a concentration of 35% is added to the mixed filtrate I for crystallization and decalcification to obtain high-purity and high-white phosphogypsum and mixed filtrate II, with a gypsum grade of 99.55% and a whiteness of 98.76%.

[0065] The mixed filtrate II is treated with a 300D nanofiltration membrane to obtain clean water and concentrated water. The clean water, which is mainly composed of lactic acid, is returned to the acid removal magnesium operation.

[0066] Ammonia water was slowly added to the concentrated water until no white precipitate was produced to obtain magnesium hydroxide precipitate. The magnesium hydroxide solid was washed with clean water, dehydrated and dried at 200°C. The purity was 99.52% and the CaO content was 0.09%.

[0067] After shrinking with water, it was dissolved in 80% ethanol, and then acetone was added to promote the crystallization of ammonium lactate to obtain calcium lactate with a purity of 99.81%.

Claims

1. A method for comprehensive utilization of calcareous collophanite and its associated elements, characterized in that: The following steps are involved: S1, grinding the calcareous colloidal phosphate ore, adding lactic acid to acidify the calcareous gangue minerals under low temperature conditions, and separating the solid and liquid to obtain low-magnesium phosphate concentrate and mixed filtrate I; S2, transfer the mixed filtrate I obtained in S1 to the reactor and add sulfuric acid to decalcify the Ca in the filtrate. 2+ Calcium sulfate dihydrate crystals are generated, and dihydrate gypsum solids and mixed filtrate II are obtained by filtration; S3, treating the mixed filtrate II obtained in S2 with a membrane, allowing small molecules to pass through the nanofiltration membrane and retain large molecules, thereby obtaining a clear solution and concentrated water; S4: Add ammonia water to the concentrated water produced in S3 to adjust the pH value of the medium and precipitate the Mg in the concentrated water 2+ , to obtain magnesium hydroxide solid and filtrate III; S5. After the filtrate III is concentrated, it is dissolved in ethanol, and then acetone is added to promote the crystallization of ammonium lactate.

2. The method according to claim 1, characterized in that: The calcareous collophosphate described in S1 has a P2O5 grade of 3-35% and a MgO grade of 1.0-20.0%.

3. The method according to claim 1, characterized in that: The amount of lactic acid in S1 is 5-40% of the mass of the reaction slurry, and the acid solution is added at a concentration of 2-20%, and the addition method is one-stage addition or multiple-stage addition.

4. The method according to claim 1, characterized in that: The lactic acid acid removal reaction temperature in S1 is 20-80° C., and the reaction liquid-to-solid ratio is 3:1-10:

1.

5. The method according to claim 1, characterized in that: S2 The crystal decalcification agent sulfuric acid is configured to be added in a concentration of 20% to 70%, and the reaction temperature is from the acid hydrolysis temperature to room temperature.

6. The method according to claim 1, characterized in that: The nanofiltration membrane used in the membrane treatment process of S3 is a nanofiltration membrane greater than or equal to 300D, and the filtrate is treated by a primary membrane.

7. The method according to claim 1, characterized in that: After adding ammonia water in S4, the reaction temperature is room temperature, and the ammonia water is added by slowly dropping until no white precipitate is produced.

8. The method according to claim 1, characterized in that: S4: After washing and dehydration, the magnesium hydroxide solid is dried at 150-250°C.

9. The method according to claim 1, characterized in that: S5 describes the use of ethanol solution III concentrate, the water content of which is less than 10%.