A method for preparing fibrous hydroxyapatite using phosphogypsum

Abstract

The application provides a method for preparing fibrous hydroxyapatite by using phosphogypsum, and the phosphogypsum is pretreated as follows: the phosphogypsum is mixed with a purifying agent and stirred uniformly, and the obtained suspension is filtered; under stirring, the filtrate is added dropwise into a phosphorus source solution, and an ammonia water solution is slowly added dropwise into the solution, the pH value of the mixed solution is adjusted to be alkaline, and then continuous stirring is carried out to obtain a mixed solution; a morphology control agent is added into the obtained mixed solution, and after uniform stirring, hydrothermal reaction is carried out; after the hydrothermal reaction is completed, the filtrate is filtered out, and the obtained filter residue is fibrous hydroxyapatite. The method has simple process, low cost and low energy consumption, the obtained hydroxyapatite has high purity and high crystallinity, and the morphology presents clear fibrous shape.

Description

Technical Field

[0001] This invention relates to the field of separation science and technology, to the treatment of industrial solid waste, and particularly to the treatment and resource utilization of phosphogypsum. Background Technology

[0002] Phosphogypsum is an unavoidable solid byproduct of the wet-process phosphoric acid production and phosphate fertilizer industry, and its main component is calcium sulfate dihydrate. Currently, over 90% of existing phosphoric acid is produced using the wet process. Approximately 5 tons of phosphogypsum are generated for every ton of phosphoric acid produced.

[0003] Currently, the actual comprehensive utilization rate of phosphogypsum in my country is approximately 30%, mainly including the preparation of industrial gypsum and gypsum building materials; its use as a cement retarder; and its co-production of cement and sulfuric acid through secondary calcination. However, phosphogypsum retains impurities such as phosphorus, fluorine, aluminum, iron, potassium, sodium, silicon, and trace amounts of radioactive elements from phosphate rock, as well as impurities introduced from flotation reagents in the wet-process phosphoric acid process. These impurities cannot be completely removed, affecting and limiting the application of phosphogypsum as industrial gypsum. Furthermore, the low industrial value of gypsum itself means that the cost of processing and recovering gypsum from phosphogypsum is far higher than the value of the industrial gypsum itself. In particular, soluble phosphorus and fluorine impurities limit the use of phosphogypsum in the building materials field. Therefore, the vast majority of phosphogypsum processing globally currently relies on stockpiling. Simple, efficient, and low-cost phosphogypsum treatment and purification technologies are the core steps for the resource-based reuse of phosphogypsum. Summary of the Invention

[0004] Currently, a composite solvent is used to mix with phosphogypsum to convert the calcium-containing compounds in phosphogypsum into soluble substances, transforming the solid-liquid reaction in the previous hydroxyapatite preparation process into a more extensive liquid-phase reaction. Through a hydrothermal reaction with a composite phosphorus source in the liquid phase at high temperature, calcium sulfate in phosphogypsum is converted into high-value hydroxyapatite.

[0005] This invention provides a method for preparing fibrous hydroxyapatite using phosphogypsum. This method is simple, and the prepared hydroxyapatite has high purity, high crystallinity, and exhibits a regular fibrous morphology.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for preparing fibrous hydroxyapatite using phosphogypsum, characterized by comprising the following steps:

[0007] S1: Phosphogypsum pretreatment: Mix phosphogypsum with a composite solvent, stir evenly, and filter the resulting suspension;

[0008] S2: Under stirring conditions, the filtrate from S1 is added dropwise to the phosphorus source solution, while ammonia solution is slowly added dropwise to the solution. After adjusting the pH of the mixed solution to alkaline, the mixture is stirred continuously to obtain the mixed solution.

[0009] S3: Add the morphology control agent to the mixed solution obtained in S2, stir evenly, and then carry out a hydrothermal reaction;

[0010] S4: After the hydrothermal reaction is completed, filter off the filtrate, and the resulting filter residue is fibrous hydroxyapatite.

[0011] The purifying agent in step S1 includes one or more of methylamine, ethylamine, ethylenediamine, triethanolamine, ethylenediaminetetraacetic acid, propylenediaminediaacetic acid, ethylenediaminediaacetic acid, ethylene glycol diethyl ether diaminetetraacetic acid, triethylenetetraaminehexaacetic acid, cyclohexanediaminetetraacetic acid, and sulfosalicylic acid. The concentration of the purifying agent is 0.5~1 mol / L.

[0012] In this case, the purifying agent is used to convert the calcium sulfate in phosphogypsum from a sparingly soluble solid into a liquid. After mixing and stirring the phosphogypsum with the purifying agent, the calcium sulfate in the phosphogypsum dissolves in the purifying agent. After filtration, the calcium sulfate is transferred to the filtrate. The addition of the purifying agent makes the reaction of calcium sulfate more complete, which helps to reduce the calcium-to-phosphorus ratio of the prepared hydroxyapatite and reduce the impurity content in the product.

[0013] The phosphorus source solution in step S2 includes one or more of the following: sodium phosphate, sodium hydrogen phosphate, sodium dihydrogen phosphate, calcium phosphate, calcium hydrogen phosphate, potassium phosphate, potassium hydrogen phosphate, potassium dihydrogen phosphate, ammonium phosphate, ammonium hydrogen phosphate, and ammonium dihydrogen phosphate. The concentration of the phosphorus source solution is 0.5~1 mol / L.

[0014] In this application, phosphate ions in the phosphorus source solution react with calcium sulfate in the dissolved purification agent and hydroxide ions in the solution in a hydrothermal reactor under high temperature and high pressure according to the following equation to generate hydroxyapatite:

[0015] 10Ca 2+ + 6PO4 3- + 2OH - → Ca 10 (PO4)6(OH)2

[0016] The concentration of the phosphorus source solution, as a reaction raw material, directly affects the calcium-to-phosphorus ratio of the prepared product.

[0017] In step S2, the dropping rate is between 0.01 and 2 mL / min, so that the pH of the mixed solution is between 11 and 13.

[0018] The morphology control agent in step S3 includes one or more of glucose, polyethylene glycol, hexadecyl ammonium bromide, ammonium citrate, sodium citrate, potassium citrate, calcium citrate, sodium salicylate, ethylenediaminetetraacetic acid, and oleyl alcohol polyoxyethylene ether. The concentration of the morphology control agent is between 0.01 and 20 g / L.

[0019] The hydrothermal reaction temperature in step (3) is 120~200℃, and the reaction time is 2~24h.

[0020] At lower temperatures, the reaction may not occur or may not be complete. The reaction can proceed completely between 120 and 200°C, so the temperature setting does not need to be too high.

[0021] This invention solves the process and cost defects existing in the prior art, and has the following beneficial effects:

[0022] This invention achieves the transfer of calcium sulfate from phosphogypsum to the liquid phase by adding a purification agent, and then reacts it with a composite phosphorus source solution in a hydrothermal reactor. Simultaneously, a morphology control agent is used to control the morphology of the resulting product, thus preparing fibrous hydroxyapatite.

[0023] It has achieved the transformation of industrial by-product phosphogypsum into high-value-added hydroxyapatite; high-purity preparation of hydroxyapatite; and directional control of product morphology.

[0024] This method is simple to operate, requires minimal equipment, and can process phosphogypsum in batches. The resulting hydroxyapatite can be used in bone repair, artificial bones, toothpaste additives, protein separation, and other fields. Attached Figure Description

[0025] Figure 1 The image shown is a SEM image of the product obtained in Example 2.

[0026] Figure 2 The image shown is a SEM image of the product obtained in Example 6. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] This invention first involves mixing phosphogypsum with a composite solvent, stirring and filtering, reacting at high temperature, and then vacuum filtering. The invention will be further described in detail below with reference to specific examples.

[0029] Example 1

[0030] Phosphogypsum, a byproduct of the calcium sulfate dihydrate process in the wet-process phosphoric acid workshop of Yidu Xingfa Chemical Co., Ltd. in Yichang City, Hubei Province, was treated by dissolving 20g of the phosphogypsum in 500mL of deionized water. 200mL of 0.5mol / L purification agent (ethylenediaminetetraacetic acid + ethylenediamine, mixed in equal volumes) was added. After stirring for 1 hour, the solution was filtered. The filtrate was then pumped into 250mL of 0.5mol / L phosphorus source composite solution (sodium hydrogen phosphate + sodium dihydrogen phosphate, mixed in equal masses) using a peristaltic pump at a rate of 2mL / min. During the process, 0.1g / L ammonia water was used to stabilize the pH of the solution at 11.5. After the addition was complete, the solution was stirred continuously for 1 hour. 1 g of morphology control agent (glucose + hexadecylammonium bromide, equimass) was added to the solution, and the mixture was stirred at 400 rpm for 15 min. The mixture was then transferred to a hydrothermal reactor and reacted at 120 °C for 24 h. The solution was then filtered, and the filter residue was characterized. The results showed that the obtained product was fibrous hydroxyapatite with a purity of 99.21% and a calcium-to-phosphorus ratio of 1.67. Figure 1 The image shows the prepared fibrous hydroxyapatite.

[0031] Example 2

[0032] Phosphogypsum, a byproduct of the calcium sulfate dihydrate process in the wet-process phosphoric acid workshop of Yidu Xingfa Chemical Co., Ltd. in Yichang City, Hubei Province, was treated by dissolving 20g of the phosphogypsum in 500mL of deionized water. 200mL of 0.5mol / L purification agent (ethylenediaminetetraacetic acid + sulfosalicylic acid, mixed in equal volumes) was added. After stirring for 1 hour, the solution was filtered. The filtrate was then pumped into 250mL of 0.5mol / L phosphorus source composite solution (potassium phosphate + potassium hydrogen phosphate + potassium dihydrogen phosphate, mixed in equal masses) using a peristaltic pump at a rate of 2mL / min. During the process, 0.1g / L ammonia water was used to stabilize the pH of the solution at 12. After the addition was complete, the solution was stirred continuously for 1 hour. 1 g of morphology control agent (hexadecylammonium bromide + ammonium citrate, mixed in equal masses) was added to the solution. After stirring at 400 rpm for 15 min, the mixture was transferred to a hydrothermal reactor and reacted at 140 °C for 24 h. The solution was then filtered, and the filter residue was characterized. The results showed that the obtained product was fibrous hydroxyapatite with a purity of 99.16% and a calcium-to-phosphorus ratio of 1.69. Its morphology and structure are similar to... Figure 1 resemblance.

[0033] Example 3

[0034] Phosphogypsum, a byproduct of the calcium sulfate dihydrate process in the wet-process phosphoric acid workshop of Yidu Xingfa Chemical Co., Ltd. in Yichang City, Hubei Province, was treated by dissolving 20g of the phosphogypsum in 500mL of deionized water. 200mL of 0.5mol / L purification agent (ethylenediaminetetraacetic acid + sulfosalicylic acid + ethylenediaminediacetic acid, mixed in equal volumes) was added. After stirring for 1 hour, the solution was filtered. The filtrate was then pumped into 250mL of 0.5mol / L phosphorus source composite solution (potassium hydrogen phosphate + sodium phosphate, mixed in equal masses) using a peristaltic pump at a rate of 2mL / min. During the process, 0.1g / L ammonia water was used to stabilize the pH of the solution at 12. After the addition was complete, the solution was stirred continuously for 1 hour. 1 g of morphology control agent (hexadecyl ammonium bromide + sodium salicylate, mixed in equal masses) was added to the solution. After stirring at 400 rpm for 15 min, the mixture was transferred to a hydrothermal reactor and reacted at 150 °C for 24 h. The solution was then filtered, and the filter residue was characterized. The results showed that the obtained product was fibrous hydroxyapatite with a purity of 99.42% and a calcium-to-phosphorus ratio of 1.67. Its morphology and structure are similar to... Figure 1 resemblance.

[0035] Example 4

[0036] Phosphogypsum, a byproduct of the calcium sulfate dihydrate process in the wet-process phosphoric acid workshop of Yidu Xingfa Chemical Co., Ltd. in Yichang City, Hubei Province, was treated by dissolving 20g of the phosphogypsum in 500mL of deionized water. 200mL of 0.5mol / L purification agent (propylenediamine diacetic acid + ethylenediamine diacetic acid, mixed in equal volumes) was added. After stirring for 1 hour, the solution was filtered. The filtrate was then pumped into 250mL of 0.5mol / L phosphorus source composite solution (sodium phosphate + sodium hydrogen phosphate + sodium dihydrogen phosphate, mixed in equal masses) using a peristaltic pump at a rate of 2mL / min. During the process, 0.1g / L ammonia water was used to stabilize the pH of the solution at 12. After the addition was complete, the solution was stirred continuously for 1 hour. 1 g of morphology control agent (hexadecyl ammonium bromide + calcium citrate, mixed in equal mass) was added to the solution. After stirring at 400 rpm for 15 min, the mixture was transferred to a hydrothermal reactor and reacted at 180 °C for 24 h. The solution was then filtered and the filter residue was characterized. The results showed that the obtained product was fibrous hydroxyapatite with a purity of 99.60% and a calcium-to-phosphorus ratio of 1.67.

[0037] Example 5

[0038] Phosphogypsum, a byproduct of the calcium sulfate dihydrate process in the wet-process phosphoric acid workshop of Yidu Xingfa Chemical Co., Ltd. in Yichang City, Hubei Province, was treated by dissolving 20g of the phosphogypsum in 500mL of deionized water. After stirring for 1 hour, the solution was filtered. The filtrate was pumped into a 0.5mol / L 250mL phosphorus source composite solution (sodium hydrogen phosphate and sodium dihydrogen phosphate, mixed in equal masses) using a peristaltic pump at a rate of 2mL / min. During the process, the pH of the solution was stabilized at 11.1 using 0.1g / L ammonia water. After the addition was complete, the solution was stirred continuously for 1 hour. 1g of morphology control agent (glucose and hexadecyl ammonium bromide, mixed in equal masses) was added to the solution, and the mixture was stirred at 400rpm for 15 minutes. The solution was then transferred to a hydrothermal reactor and reacted at 120℃ for 24 hours. The solution was then filtered, and the filter residue was characterized. The results showed that the obtained product was a mixture of hydroxyapatite and calcium sulfate, with the hydroxyapatite exhibiting a fibrous structure and a purity of 95.25%. The calcium-to-phosphorus ratio of the product was 1.79. Compared with Example 1, it can be seen that the addition of the purifying agent can significantly improve the purity of the product and increase the degree of reaction of calcium-containing compounds in phosphogypsum.

[0039] Example 6

[0040] Phosphogypsum, a byproduct of the calcium sulfate dihydrate process in the wet-process phosphoric acid workshop of Yidu Xingfa Chemical Co., Ltd. in Yichang City, was treated by dissolving 20g of the phosphogypsum in 500mL of deionized water. 200mL of 0.5mol / L purification agent (ethylenediaminetetraacetic acid + ethylenediamine, mixed in equal volumes) was added. After stirring for 1 hour, the mixture was filtered. The filtrate was pumped into 250mL of 0.5mol / L phosphorus source composite solution (sodium hydrogen phosphate + sodium dihydrogen phosphate, mixed in equal masses) using a peristaltic pump at a rate of 2mL / min. During the process, 0.1g / L ammonia water was used to stabilize the pH of the solution at 11.5. After the addition was complete, stirring was continued for 1 hour. After stirring at 400rpm for 15 minutes, the mixture was transferred to a hydrothermal reactor and reacted at 120℃ for 24 hours. The solution was then filtered, and the filter residue was characterized. The results showed that the obtained product was amorphous hydroxyapatite with a purity of 99.22% and a calcium-to-phosphorus ratio of 1.65. Figure 2 As can be seen, the product does not have a distinct fibrous morphology, but rather presents as an amorphous, blocky aggregate. Compared with Example 1, it is evident that the addition of the morphology control agent can directionally regulate the morphology of the prepared hydroxyapatite. Figure 2 The amorphous hydroxyapatite obtained is shown.

[0041] Example 7

[0042] Phosphogypsum, a byproduct of the calcium sulfate dihydrate process in the wet-process phosphoric acid workshop of Yidu Xingfa Chemical Co., Ltd. in Yichang City, Hubei Province, was treated by dissolving 20g of the phosphogypsum in 500mL of deionized water. 200mL of 0.5mol / L purification agent (ethylenediaminetetraacetic acid + ethylenediamine, mixed in equal volumes) was added, and the mixture was stirred for 1 hour before filtration. The filtrate was then pumped into 250mL of 0.5mol / L sodium phosphate solution using a peristaltic pump at a rate of 2mL / min. During the process, 0.1g / L ammonia water was used to stabilize the pH of the solution at 11.5. After the addition was complete, stirring was continued for 1 hour. 1g of morphology control agent (glucose + hexadecylammonium bromide, mixed in equal masses) was added to the solution, and the mixture was stirred at 400rpm for 15min. The solution was then transferred to a hydrothermal reactor and reacted at 120℃ for 24 hours. The solution was then filtered, and the filter residue was characterized. The results showed that the obtained product was fibrous hydroxyapatite with a purity of 97.36% and a calcium-to-phosphorus ratio of 1.71. Compared with Example 1, it can be seen that the phosphorus source composite solution can effectively improve the degree of reaction of raw materials, improve product purity, and thereby reduce the calcium-phosphorus ratio of the product.

[0043] Example 8

[0044] Phosphogypsum, a byproduct of the calcium sulfate dihydrate process in the wet-process phosphoric acid workshop of Yidu Xingfa Chemical Co., Ltd. in Yichang City, Hubei Province, was treated by dissolving 20g of the phosphogypsum in 500mL of deionized water. 200mL of 0.5mol / L purification agent (ethylenediaminetetraacetic acid + ethylenediamine, mixed in equal volumes) was added. After stirring for 1 hour, the solution was filtered. The filtrate was then pumped into 250mL of 0.5mol / L phosphorus source composite solution (sodium hydrogen phosphate + sodium dihydrogen phosphate, mixed in equal masses) using a peristaltic pump at a rate of 2mL / min. During the process, 0.1g / L ammonia water was used to stabilize the pH of the solution at 11.5. After the addition was complete, the solution was stirred continuously for 1 hour. 1g of morphology control agent (glucose + hexadecylammonium bromide, mixed in equal masses) was added to the solution. After stirring at 400rpm for 15min, the mixture was transferred to a hydrothermal reactor and reacted at 80℃ for 24h. The solution was then filtered, and the filter residue was characterized. The results showed that the obtained product was a mixture of calcium sulfate and hydroxyapatite, with a purity of 94.21% and a calcium-to-phosphorus ratio of 1.80. Compared with Example 1, it can be seen that when the reaction temperature is lower, the degree of reaction of the raw materials is lower, resulting in a lower purity and a higher calcium-to-phosphorus ratio of the obtained product.

[0045] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for preparing fibrous hydroxyapatite using phosphogypsum, characterized in that, The method includes the following steps: S1: Pretreatment of phosphogypsum: Mix phosphogypsum with the purifying agent, stir evenly, and filter the resulting suspension. The purifying agent is selected from one or more of methylamine, ethylamine, ethylenediamine, triethanolamine, ethylenediaminetetraacetic acid, propylenediaminediaacetic acid, ethylenediaminediaacetic acid, ethylene glycol diethyl ether diaminetetraacetic acid, triethylenetetraaminehexaacetic acid, cyclohexanediaminetetraacetic acid, and sulfosalicylic acid. S2: Under stirring conditions, the filtrate from S1 is added dropwise to the phosphorus source solution, while ammonia solution is slowly added dropwise to the solution. After adjusting the pH of the mixed solution to alkaline, the mixture is stirred continuously to obtain the mixed solution. S3: Add the morphology control agent to the mixed solution obtained in S2, stir evenly, and then carry out a hydrothermal reaction. The morphology control agent is selected from one or more of glucose, polyethylene glycol, hexadecyl ammonium bromide, ammonium citrate, sodium citrate, potassium citrate, calcium citrate, sodium salicylate, ethylenediaminetetraacetic acid, and oleyl alcohol polyoxyethylene ether. S4: After the hydrothermal reaction is completed, filter off the filtrate, and the resulting filter residue is fibrous hydroxyapatite.

2. The method for preparing fibrous hydroxyapatite using phosphogypsum according to claim 1, characterized in that: The concentration of the purifying agent is 0.1~1 mol / L.

3. The method for preparing fibrous hydroxyapatite using phosphogypsum according to claim 1, characterized in that: The phosphorus source solution in step S2 includes one or more of the following: sodium phosphate, sodium hydrogen phosphate, sodium dihydrogen phosphate, calcium phosphate, calcium hydrogen phosphate, potassium phosphate, potassium hydrogen phosphate, potassium dihydrogen phosphate, ammonium phosphate, ammonium hydrogen phosphate, and ammonium dihydrogen phosphate.

4. The method for preparing fibrous hydroxyapatite using phosphogypsum according to claim 3, characterized in that: The concentration of the phosphorus source solution is 0.001~1 mol / L.

5. The method for preparing fibrous hydroxyapatite using phosphogypsum according to claim 1, characterized in that: In step S2, the pH of the mixed solution is between 11 and 13.

6. The method for preparing fibrous hydroxyapatite using phosphogypsum according to claim 1, characterized in that: The concentration of morphology control agent is between 0.01 and 20 g / L.

7. The method for preparing fibrous hydroxyapatite using phosphogypsum according to claim 1, characterized in that: The hydrothermal reaction temperature in step (3) is 100~200℃ and the reaction time is 2~24h.

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