Method for preparing calcium carbonate whiskers from phosphate tailings

Abstract

The invention discloses a method for preparing calcium carbonate whiskers from phosphate tailings, which comprises the following steps: (1) grinding the phosphate tailings, sieving with a 200-mesh sieve, calcining for a certain time at a certain temperature, and naturally cooling to obtain calcined tailings; (2) reacting the calcined tailings obtained in the step (1) with ammonium salt, and filtering to obtain CaX mother liquor; (3) mixing the CaX mother liquor obtained in the step (2) with the prepared crystal form control agent to obtain a mixed solution; and (4) heating the mixed solution obtained in the step (3) to a certain temperature, slowly dropwise adding a carbonate solution, continuously keeping the temperature for a period of time after dropwise adding, cooling and aging for a certain time after keeping the temperature, carrying out suction filtration, repeatedly washing with distilled water for several times, precipitating, and drying to obtain the calcium carbonate whisker product. The method is characterized in that the calcium element in the phosphate tailings is extracted and utilized, the calcium carbonate whiskers with the length-diameter ratio of 20-25 are prepared, the process is simple, and the product uniformity is good.

Description

Technical Field

[0001] The invention relates to the field of calcium carbonate whisker preparation, and in particular to a method for preparing calcium carbonate whiskers by utilizing phosphate tailings. Background Art

[0002] Phosphate tailings, a major solid waste, have enormous stockpiles, and their disposal and utilization are a hot topic. Phosphate tailings contain over 40% calcium, offering significant potential for utilization.

[0003] Calcium carbonate whiskers are a new type of inorganic filler with a high aspect ratio, showing promising application prospects in plastics, papermaking, coatings, and other fields. In plastics, calcium carbonate whiskers can effectively improve the impact and tensile strength of plastics. In coatings, they can significantly enhance crack resistance, adhesion, and bond strength. In papermaking, they can effectively improve the hiding power and tear resistance of paper.

[0004] Patent CN116024646A discloses a method for preparing calcium carbonate whiskers with a high aspect ratio and chain-like morphology. This method utilizes double decomposition to prepare calcium carbonate whiskers. A double injection reaction is performed in a deionized water / anhydrous ethanol system to produce calcium carbonate whiskers with an aspect ratio of 15-25. This invention simultaneously injects Ca2+ and CO2-3, resulting in uneven morphology, poor dispersibility, and limited practicality.

[0005] Patent CN111926386B discloses a method for producing calcium carbonate whiskers. This method uses high-purity nano-calcium oxide as a raw material, silk fibroin, and gum arabic as crystal form control agents, and produces the calcium carbonate whiskers through a carbonization reaction in a high-gravity carbonization reactor. While this method can produce good calcium carbonate whiskers, the high-purity nano-calcium oxide used as a raw material is expensive and is not suitable for large-particle calcium oxide.

[0006] Patent CN104480529A discloses a method for producing calcium carbonate whiskers using industrial waste phosphogypsum as a raw material. This method uses industrial waste phosphogypsum as the raw material, mixes it with water, then drips sodium carbonate and filters it to produce precipitated calcium carbonate whiskers. This invention directly reacts with phosphogypsum, and other impurities in the phosphogypsum can affect the product morphology and yield. The disclosed invention also lacks conclusive information on the product.

[0007] Patent CN110029396A discloses a method for preparing functional calcium carbonate whiskers. This method uses a carbonization method to prepare a Ca(OH)2 suspension, followed by the introduction of CO2 to produce the calcium carbonate whisker product. However, this invention suffers from a lengthy digestion process during the Ca(OH)2 suspension preparation stage, which limits its practicality.

[0008] Patent CN112723403B discloses a method for preparing calcium carbonate whiskers. This method uses calcium oxide as a raw material, the reaction product of CO2 and potassium hydroxide, and one or two of strontium chloride, sodium phosphate, and sodium citrate as crystal form control agents, and introduces lime kiln gas to undergo a carbonation reaction to produce the calcium carbonate whisker product. This invention requires the calcium hydroxide suspension to age for 40-60 hours, which is excessively long.

[0009] Summarize the problems existing in the prior art and thus have the present invention.

[0010] In summary, compared to similar patents, this invention extracts and enriches calcium from bulk solid waste phosphate tailings using calcination activation and ammonium salt leaching. By combining a double decomposition reaction with a certain amount of crystal form control agent, a high aspect ratio calcium carbonate whisker product is produced. The product has good morphology and uniform dispersion. The magnesium and phosphorus in the phosphate tailings can also be used for subsequent product development, thus achieving high-quality utilization of solid waste. Summary of the Invention

[0011] In order to fully utilize the calcium element in phosphate tailings and increase the added value of solid waste utilization, the present invention provides a method for preparing calcium carbonate whiskers using phosphate tailings.

[0012] To achieve the above object, the technical solution adopted by the present invention consists of the following steps: A method for preparing calcium carbonate whiskers using phosphate tailings comprises the following steps: 1) Grind the phosphate tailings through a 200-mesh sieve, calcine at a certain temperature for a certain period of time, and then cool naturally to obtain calcined tailings; 2) reacting the calcined tailings obtained in step 1) with ammonium salt and filtering to obtain a CaX mother liquor; 3) mixing the CaX mother liquor obtained by the treatment in step 2) with the prepared crystal form control agent to obtain a mixed solution; 4) After the mixed solution in step 3) is heated to a certain temperature, the carbonate solution is slowly added dropwise, and the temperature is kept for a period of time after the addition is completed. After the temperature is kept for a period of time, the solution is cooled and aged for a certain period of time, filtered, washed with distilled water repeatedly for several times, and dried to obtain a calcium carbonate whisker product.

[0013] Furthermore, the temperature in step 1) is 600-1200° C., and the calcination time is 0.5-4 h.

[0014] Furthermore, the ammonium salt in step 2) is one or more of ammonium chloride, ammonium nitrate, and ammonium sulfate.

[0015] Furthermore, the ratio of the ammonium salt to the calcined tailings in step 2) is converted into a molar ratio of ammonium salt to actual calcium oxide, which is 1-2.5:1, the liquid-solid ratio is 6-10:1, the reaction time is 20-60 min, and the reaction temperature is 25-55°C.

[0016] Furthermore, the crystal form controlling agent in step 3) includes one or more of glucose, ethanol, and magnesium chloride.

[0017] Furthermore, the amount of the crystal form control agent added in step 3) accounts for 6-15% of the molar amount of Ca2+ in the solution.

[0018] Furthermore, the carbonate addition rate in step 4) is maintained at 5-10 mL / min.

[0019] Furthermore, the temperature of the mixed solution in step 4) is 70-100°C.

[0020] Furthermore, the molar ratio of the introduced CO2- 3 to Ca2+ described in step 4) is 1-1.5:1, and the concentration of the carbonate solution is 0.1-0.3 mol / L.

[0021] Furthermore, the holding time in step 4) is 0.5-2h.

[0022] Furthermore, the cooling in step 4) refers to cooling to room temperature, and the aging time is 0.5-2 hours.

[0023] Compared with the prior art, this technical solution has the following technical effects:

[0024] The present invention activates calcium and magnesium in the mineral phase by calcining in the pretreatment stage of the phosphate tailings at the front end, and then controls the step-by-step leaching of calcium and magnesium by adjusting various conditions of ammonium salt. The leaching rate of calcium can reach 82%, thereby fully utilizing the elemental calcium in the phosphate tailings.

[0025] The present invention controls the whisker morphology and uniformity by adding or compounding a crystal form control agent in the back-end calcium carbonate whisker preparation stage, thereby obtaining a product with good morphology and uniform dispersion. The prepared product can be applied to coatings, rubber and other fields, providing a way to effectively dispose of phosphorus tailings, a large amount of solid waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a SEM scanning electron microscope image of the calcium carbonate whisker of Example 1.

[0027] Figure 2 This is a SEM scanning electron microscope image of the calcium carbonate whisker of Example 2.

[0028] Figure 3This is a SEM scanning electron microscope image of the calcium carbonate whisker of Example 3.

[0029] Figure 4 This is a SEM scanning electron microscope image of the calcium carbonate whisker of Example 4.

[0030] Figure 5 This is the SEM scanning electron microscope image of the calcium carbonate whisker of Comparative Example 1.

[0031] Figure 6 This is the SEM scanning electron microscope image of the calcium carbonate whisker of Comparative Example 2. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to embodiments. Example

[0033] The phosphate tailings were ground through a 200-mesh sieve, calcined in a muffle furnace at 900°C for 0.5h, and then naturally cooled to obtain calcined tailings; Weigh 10 g of calcined tailings and 9.75 g of NH4Cl in a round-bottom flask, add 197.5 mL of H2O, and react at 45 °C for 30 min to obtain CaCl2 mother liquor; Take 200 mL of CaCl2 mother liquor and mix it with 0.296 g of MgCl2 to obtain a mixed solution; The mixed solution was heated to 90°C, and 0.2 mol / L sodium carbonate solution was slowly dripped into the mixed solution described in step 3). The mixture was kept warm for 2 hours after the addition was completed. After the heat preservation was completed, the mixture was cooled and aged for 1 hour, filtered, and washed with distilled water several times to precipitate. The mixture was dried to obtain a calcium carbonate whisker product with a length of 15 μm. Example

[0034] The phosphate tailings were ground through a 200-mesh sieve, calcined in a muffle furnace at 900°C for 2 h, and then naturally cooled to obtain calcined tailings; Weigh 10 g of calcined tailings and 9.75 g of NH4Cl in a round-bottom flask, add 197.5 mL of H2O, and react at 45 °C for 30 min to obtain CaCl2 mother liquor; Take 200 mL of CaCl2 mother solution and mix it with 0.559 g of glucose to obtain a mixed solution; The mixed solution was heated to 80°C, and a sodium carbonate solution with a concentration of 0.2 mol / L was slowly dripped into the mixed solution described in step 3). The mixture was kept warm for 2 h after the addition was completed. After the heat preservation was completed, the mixture was cooled and aged for 1 h, filtered, and washed with distilled water repeatedly for several times to precipitate. The mixture was dried to obtain a calcium carbonate whisker product with a length of 20 μm. Example

[0035] The phosphate tailings were ground through a 200-mesh sieve, calcined in a muffle furnace at 900°C for 2 h, and then naturally cooled to obtain calcined tailings; Weigh 10 g of calcined tailings and 9.75 g of NH4Cl in a round-bottom flask, add 197.5 mL of H2O, and react at 45 °C for 30 min to obtain CaCl2 mother liquor; Take 200 mL of CaCl2 mother solution and mix it with 0.933 g of glucose to obtain a mixed solution; The mixed solution was heated to 90°C, and a sodium carbonate solution with a concentration of 0.2 mol / L was slowly dripped into the mixed solution described in step 3). The mixture was kept warm for 2 h after the addition was completed. After the heat preservation was completed, the mixture was cooled and aged for 1 h, filtered, and washed with distilled water several times to precipitate. The mixture was dried to obtain a calcium carbonate whisker product with a length of 22 μm.

[0036] Example 4 The phosphate tailings were ground through a 200-mesh sieve, calcined in a muffle furnace at 600°C for 4 hours, and then naturally cooled to obtain calcined tailings; Weigh 10 g of calcined tailings and 9.75 g of NH4Cl in a round-bottom flask, add 197.5 mL of H2O, and react at 45 °C for 30 min to obtain CaCl2 mother liquor; Take 200 mL of CaCl2 mother liquor and mix it with 0.493 g of MgCl2 to obtain a mixed solution; The mixed solution was heated to 90°C, and a sodium carbonate solution with a concentration of 0.2 mol / L was slowly dripped into the mixed solution described in step 3). The mixture was kept warm for 2 hours after the addition was completed. After the heat preservation was completed, the mixture was cooled and aged for 1 hour, filtered, and washed with distilled water several times to precipitate. The mixture was dried to obtain a calcium carbonate whisker product with a length of about 15 μm.

[0037] Comparative Example 1 The phosphate tailings were ground through a 200-mesh sieve, calcined in a muffle furnace at 500°C for 0.5h, and then naturally cooled to obtain calcined tailings; Weigh 10 g of calcined tailings and 9.75 g of NH4Cl in a round-bottom flask, add 197.5 mL of H2O, and react at 45 °C for 30 min to obtain CaCl2 mother liquor; Take 200 mL of CaCl2 mother liquor and mix it with 0.146 g of MgCl2 to obtain a mixed solution; The mixed solution was heated to 90°C, and a sodium carbonate solution with a concentration of 0.2 mol / L was slowly dripped into the mixed solution described in step 3). The mixture was kept warm for 2 hours after the addition was completed. After the heat preservation was completed, the mixture was cooled and aged for 1 hour, filtered, and washed with distilled water repeatedly for several times to precipitate. The mixture was dried to obtain a calcium carbonate whisker product with a length of about 5 μm.

[0038] Comparative Example 2 The phosphate tailings were ground through a 200-mesh sieve, calcined in a muffle furnace at 900°C for 2 h, and then naturally cooled to obtain calcined tailings; Weigh 10 g of calcined tailings and mix with 0.146 g of MgCl2 to obtain a mixed sample, and measure 197.5 mL of H2O to mix to obtain a mixed liquid; The mixed liquid was heated to 90°C, and a sodium carbonate solution with a concentration of 0.2 mol / L was slowly dripped into the mixed liquid described in step 2). The mixture was kept warm for 2 h after the addition was completed. After the heat preservation was completed, the mixture was cooled and aged for 1 h, filtered, washed repeatedly with distilled water for several times, and dried to obtain calcium carbonate products with different morphologies, most of which were vaterite morphologies.

Claims

1. A method for preparing calcium carbonate whiskers using phosphate tailings, comprising the following steps: 1) Grind the phosphate tailings through a 200-mesh sieve, calcine at a certain temperature for a certain period of time, and then cool naturally to obtain calcined tailings; 2) reacting the calcined tailings obtained in step 1) with ammonium salt and filtering to obtain a CaX mother liquor; 3) mixing the CaX mother liquor obtained by the treatment in step 2) with the prepared crystal form control agent to obtain a mixed solution; 4) After the mixed solution in step 3) is heated to a certain temperature, the carbonate solution is slowly added dropwise, and the temperature is kept for a period of time after the addition is completed. After the temperature is kept for a period of time, the solution is cooled and aged for a certain period of time, filtered, washed with distilled water repeatedly for several times, and dried to obtain a calcium carbonate whisker product.

2. a kind of method utilizing phosphate tailings to prepare calcium carbonate whiskers as claimed in claim 1, is characterized in that, The temperature in step 1) is 600-1200° C., and the calcination time is 0.5-4 h.

3. a kind of method utilizing phosphate tailings to prepare calcium carbonate whiskers as claimed in claim 1, is characterized in that, The ammonium salt in step 2) is one or more of ammonium chloride, ammonium nitrate and ammonium sulfate.

4. a kind of method utilizing phosphate tailings to prepare calcium carbonate whiskers as claimed in claim 1, is characterized in that, The ratio of the ammonium salt to the calcined tailings in step 2) is converted into a molar ratio of ammonium salt to actual calcium oxide, which is 1-2.5:1, the liquid-solid ratio is 6-10:1, the reaction time is 20-60 minutes, and the reaction temperature is 25-55°C.

5. a kind of method utilizing phosphate tailings to prepare calcium carbonate whiskers as claimed in claim 1, is characterized in that, The crystal form controlling agent in step 3) includes one or more of glucose, ethanol, and magnesium chloride.

6. a kind of method utilizing phosphate tailings to prepare calcium carbonate whiskers as claimed in claim 1, is characterized in that, The amount of the crystal form control agent added in step 3) accounts for 1% of the Ca 2+ 6-15% of the molar weight.

7. a kind of method utilizing phosphate tailings to prepare calcium carbonate whiskers as claimed in claim 1, is characterized in that, The carbonate addition rate in step 4) is maintained at 5-10 mL / min.

8. a kind of method utilizing phosphate tailings to prepare calcium carbonate whiskers as claimed in claim 1, is characterized in that, The temperature of the mixed solution in step 4) is 70-100°C.

9. a kind of method utilizing phosphate tailings to prepare calcium carbonate whiskers as claimed in claim 1, is characterized in that, The CO2-3 introduced in step 4) and Ca 2+ The molar ratio is (1-1.5):1, and the concentration of the carbonate solution is 0.1-0.3 mol / L.

10. A method for preparing calcium carbonate whiskers using phosphate tailings as claimed in claim 1, characterized in that: The holding time in step 4) is 0.5-2h.

11. A method for preparing calcium carbonate whiskers using phosphate tailings as claimed in claim 1, characterized in that: The cooling mentioned in step 4) refers to cooling to room temperature, and the aging time is 0.5-2h.

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