A method for producing active hydroxyapatite

Abstract

The application discloses a production method of active calcium hydroxyl phosphate, which comprises the following steps: heating defluorinated dilute phosphoric acid to 40-60 DEG C, adding lime milk under stirring, controlling the pH of the reaction to be 2.5-3.5, aging the reaction slurry, filtering, obtaining a first-stage neutralization liquid and fertilizer-grade calcium hydrogen phosphate, slowly adding the first-stage neutralization liquid into lime milk, controlling the molar ratio of calcium to phosphorus in the system to be 1.65-1.75, aging the calcium hydroxyl phosphate suspension, filtering after the aging is completed, washing the filter cake with deionized water, and then flash-drying the filter cake to obtain the active calcium hydroxyl phosphate product, wherein each index of the product meets the regulation of the HG / T 3583-2009 standard. The application effectively solves the technical problems of the existing defluorinated phosphoric acid, such as many impurities, low activity of the product, poor purity, and low raw material utilization rate, and realizes the resource-efficient utilization of the industrial defluorinated phosphoric acid. The process is simple, the cost is low, and the method is suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the field of inorganic phosphate material preparation technology, specifically relating to a method for preparing highly active calcium hydroxyphosphate by pretreatment of crude phosphoric acid with lime milk followed by a coupled neutralization reaction. Background Technology

[0002] Hydroxyphosphate is a functional inorganic material with excellent biocompatibility, strong adsorption capacity, and good chemical stability. It is widely used in water purification, soil improvement, food additives, biomedicine, and rubber and plastic filling modification. Compared with ordinary hydroxyphosphate, activated hydroxyphosphate has a higher specific surface area, porosity, and surface active sites, resulting in superior adsorption, chelation, and filling performance, and thus higher market application value.

[0003] Currently, industrially produced calcium hydroxyphosphate is mostly prepared by directly neutralizing purified phosphoric acid with calcium hydroxide, which results in high production costs. Using crude phosphoric acid directly leads to products with low purity, coarse grains, and poor surface activity, significantly limiting their applications. Therefore, developing an industrial production method for stable preparation of highly active, high-purity calcium hydroxyphosphate using industrial crude phosphoric acid as raw material and deep impurity removal through lime slurry pretreatment has significant practical value in production. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing active hydroxyapatite using defluorinated phosphoric acid, so as to solve the technical problems of existing defluorinated phosphoric acid having many impurities, low activity of the finished product, poor purity, and low raw material utilization.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for producing active hydroxyapatite, comprising the following steps: S1. The temperature of the defluorinated dilute phosphoric acid solution is raised to 40-60℃, and lime milk is added under stirring to carry out the reaction. The pH of the reaction is controlled at 2.5-3.5 to prepare the reaction slurry. S2. The reaction slurry prepared in step S1 is aged, filtered after aging, to obtain a neutralized liquid and fertilizer-grade dicalcium phosphate; S3. The neutralized solution obtained in step S2 is slowly added to lime milk at room temperature to react, and the calcium-to-phosphorus molar ratio of the system is controlled at 1.65~1.75. The reaction is continued for 60~90 min to generate a calcium hydroxyphosphate suspension. The calcium hydroxyphosphate suspension is then aged. S4. After the calcium hydroxyphosphate suspension has been aged, the calcium hydroxyphosphate suspension is filtered and the filter cake is washed with deionized water 3 to 5 times to remove residual soluble salt impurities. S5. Flash-dry the washed filter cake to obtain the active hydroxyapatite product.

[0006] Further, in step S1, the mass concentration of P2O5 in the defluorinated dilute phosphoric acid is 8-12%, and the mass concentration of CaO in the lime slurry is 5-10%.

[0007] Furthermore, in step S2, the aging time of the reaction slurry is 20-50 minutes.

[0008] Furthermore, in step S3, the aging time of the calcium hydroxyphosphate suspension is 6-12 h, and the aging temperature is 40-60℃.

[0009] Furthermore, in step S4, the filter cake is washed three times with deionized water, with the amount of water added each time being 0.5 times the mass of the filter cake.

[0010] The process principle of this invention is as follows: First, defluorinated dilute phosphoric acid is pretreated with lime milk, and the weakly acidic environment is precisely controlled to remove some metal impurities such as iron and aluminum in the raw materials by generating insoluble precipitates; then, by precisely controlling the calcium-to-phosphorus ratio, reaction pH, temperature and aging time, a controllable neutralization reaction between phosphoric acid and lime milk is achieved to generate hydroxycalcium phosphate.

[0011] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention uses defluorinated dilute phosphoric acid as raw material, which is readily available and inexpensive, realizing resource utilization, energy saving and environmental protection, and is suitable for industrial mass production.

[0012] 2. An additional lime slurry pretreatment and impurity removal process is added, which precisely controls the weakly acidic impurity removal environment, efficiently removes residual metal ions and other impurities from defluorinated dilute phosphoric acid, significantly improves the purity of the finished product, and solves the problems of high impurities and unstable quality of the finished product in the traditional process.

[0013] 3. By precisely controlling the calcium-to-phosphorus ratio, pH value, temperature, and aging parameters of the neutralization reaction, active hydroxyphosphate with a large specific surface area, high surface activity, and uniform grain size can be prepared, thus expanding its application range.

[0014] 4. The overall process is simple, the operation is controllable, the reaction conditions are mild, the raw material utilization rate is high, the production cost is low, and it has extremely high industrialization and promotion value. Detailed Implementation

[0015] The invention will be further described below with reference to specific embodiments. Example 1

[0016] A method for producing active hydroxyapatite, comprising the following steps: S1. Defluorinated dilute phosphoric acid with a P2O5 mass concentration of 8% is pumped to a neutralization tank and heated to 40°C. Under stirring conditions, lime slurry with a mass fraction of 10% is slowly added dropwise, and the pH value of the system is controlled at 2.5 to prepare a reaction slurry.

[0017] S2. Continue aging the reaction slurry prepared in step S1 for 30 minutes. After aging, send the slurry to a filter press for filtration via a transfer pump. The filtrate, i.e., the first-stage neutralization liquid, is the pretreatment acid. The first-stage neutralization liquid is transferred to the second-stage neutralization tank via a transfer pump. The filter residue (fertilizer-grade dicalcium phosphate) is sent to produce fertilizer-grade dicalcium phosphate.

[0018] S3. The lime slurry is pumped into a two-stage neutralization tank with stirring. The pretreated acid obtained in step S2 is slowly added dropwise at room temperature. The calcium-to-phosphorus molar ratio of the system is controlled at 1.65. The reaction is carried out for 60 min to generate a calcium hydroxyphosphate suspension.

[0019] S4. The obtained calcium hydroxyphosphate suspension is transported to an aging tank for aging for 6 hours. After aging, the slurry is sent to a filter press by a conveying pump to obtain activated calcium hydroxyphosphate filter cake and mother liquor. The mother liquor is returned to the system to dilute the defluorinated phosphoric acid.

[0020] S5. The active hydroxycalcium phosphate filter cake obtained in step S4 is washed three times with deionized water. Each time, the amount of water added is 0.5 times the mass of the active tricalcium phosphate filter cake. Then, it is sent to a rotary flash dryer for drying to obtain an active hydroxycalcium phosphate product that meets the HG / T3583-2009 standard. Example 2

[0021] A method for producing active hydroxyapatite, comprising the following steps: S1. Defluorinated dilute phosphoric acid with a P2O5 mass concentration of 9% is pumped to a neutralization tank and heated to 50°C. Under stirring conditions, lime slurry with a mass fraction of 7% is slowly added dropwise, and the pH value of the system is controlled to 3 to prepare a reaction slurry.

[0022] S2. Continue aging the reaction slurry prepared in step S1 for 45 minutes. After aging, send the slurry to a filter press via a transfer pump. The filtrate (pretreated acid) is sent to the second-stage neutralization tank via a transfer pump. The filter residue (fertilizer-grade dicalcium phosphate) is sent to produce fertilizer-grade dicalcium phosphate.

[0023] S3. The lime slurry is pumped into a two-stage neutralization tank with stirring. The pretreated acid obtained in step S2 is slowly added dropwise at room temperature. The calcium-to-phosphorus molar ratio of the system is controlled at 1.7. The reaction is carried out for 75 minutes to generate a calcium hydroxyphosphate suspension.

[0024] S4. The obtained calcium hydroxyphosphate suspension is transported to an aging tank for aging for 10 hours. After aging, the slurry is sent to a filter press by a conveying pump to obtain activated calcium hydroxyphosphate filter cake and mother liquor. The mother liquor is returned to the system to dilute the defluorinated acid.

[0025] S5. The active hydroxyapatite filter cake obtained in step S4 is washed four times with deionized water, and the amount of water added each time is 0.5 times the mass of the tricalcium phosphate filter cake. The mixture is then dried by rotary flash evaporation to obtain an active hydroxyapatite product that meets the HG / T 3583-2009 standard. Example 3

[0026] A method for producing active hydroxyapatite, comprising the following steps: S1. Defluorinated dilute phosphoric acid with a P2O5 mass concentration of 10% is pumped to a neutralization tank and heated to 60°C. Under stirring conditions, lime slurry with a mass fraction of 8% is slowly added dropwise, and the pH value of the system is controlled at 3.5 to prepare a reaction slurry.

[0027] S2. Continue aging the reaction slurry prepared in step S1 for 60 minutes. After aging, send the slurry to a filter press via a transfer pump. The filtrate (pretreated acid) is sent to the second-stage neutralization tank via a transfer pump. The filter residue (fertilizer-grade dicalcium phosphate) is sent to produce fertilizer-grade dicalcium phosphate.

[0028] S3. The lime slurry is pumped into a two-stage neutralization tank with stirring. The pretreated acid obtained in step S2 is slowly added dropwise at room temperature. The calcium-to-phosphorus molar ratio of the system is controlled at 1.75. The reaction is carried out for 90 min to generate a calcium hydroxyphosphate suspension.

[0029] S4. The obtained calcium hydroxyphosphate suspension is transported to an aging tank for aging for 12 hours. After aging, the slurry is sent to a filter press by a conveying pump to obtain activated calcium hydroxyphosphate filter cake and mother liquor. The mother liquor is returned to the system to dilute the defluorinated acid.

[0030] S5. Wash the activated hydroxyapatite filter cake obtained in step S4 with water three times, with the amount of water added each time being 0.5 times the mass of the activated hydroxyapatite filter cake. Then, dry it by rotary flash evaporation to obtain an activated hydroxyapatite product that meets the HG / T 3583-2009 standard. Example 4

[0031] A method for producing active hydroxyapatite, comprising the following steps: 12% S1.P2O5 defluorinated dilute phosphoric acid is pumped to a neutralization tank and heated to 50°C. Under stirring conditions, 5% lime slurry is slowly added dropwise, and the pH of the system is controlled to 3 to prepare a reaction slurry.

[0032] S2. Continue aging the reaction slurry prepared in step S1 for 30 minutes. After aging, send the slurry to a filter press via a transfer pump. The filtrate (pretreated acid) is sent to the second-stage neutralization tank via a transfer pump. The filter residue (fertilizer-grade dicalcium phosphate) is sent to produce fertilizer-grade dicalcium phosphate.

[0033] S3. The lime slurry is pumped into a two-stage neutralization tank with stirring. The pretreated acid obtained in step S2 is slowly added dropwise at room temperature. The calcium-to-phosphorus molar ratio of the system is controlled at 1.7. The reaction is carried out for 80 min to generate a calcium hydroxyphosphate suspension.

[0034] S4. The obtained calcium hydroxyphosphate suspension is transported to an aging tank for aging for 10 hours. After aging, the slurry is sent to a filter press by a conveying pump to obtain activated calcium hydroxyphosphate filter cake and mother liquor. The mother liquor is returned to the system to dilute the defluorinated acid.

[0035] S5. Wash the activated hydroxyapatite filter cake obtained in step S4 with water five more times, each time adding water at a rate of 0.5 times the mass of the activated hydroxyapatite filter cake. Then, dry the filter cake by rotary flash evaporation to obtain an activated hydroxyapatite product that meets the HG / T 3583-2009 standard.

[0036] The equipment and devices used in the method of this invention, such as neutralization tanks, filter presses, and rotary flash dryers, are all existing technologies.

[0037] This invention employs lime slurry to pretreat and remove impurities from defluorinated dilute phosphoric acid. By replacing the purification acid with the pretreated acid obtained from the first-stage neutralization of the defluorinated dilute phosphoric acid, production costs are significantly reduced, and the resulting active hydroxyapatite product is of excellent quality. This effectively solves the technical problems of existing defluorinated phosphoric acid processes, such as high impurity levels, low finished product activity, poor purity, and low raw material utilization, achieving efficient resource utilization of industrial defluorinated phosphoric acid. The process is simple, low-cost, and suitable for large-scale industrial production.

Claims

1. A method for producing active hydroxyapatite, characterized in that, The steps are as follows: S1. The temperature of the defluorinated dilute phosphoric acid solution is raised to 40-60℃, and lime milk is added under stirring to carry out the reaction. The pH of the reaction is controlled at 2.5-3.5 to prepare the reaction slurry. S2. The reaction slurry prepared in step S1 is aged, filtered after aging, to obtain a neutralized liquid and fertilizer-grade dicalcium phosphate; S3. The neutralized solution obtained in step S2 is slowly added to lime milk at room temperature to react, and the calcium-to-phosphorus molar ratio of the system is controlled at 1.65~1.

75. The reaction is continued for 60~90 min to generate a calcium hydroxyphosphate suspension. The calcium hydroxyphosphate suspension is then aged. S4. After the calcium hydroxyphosphate suspension has been aged, the calcium hydroxyphosphate suspension is filtered and the filter cake is washed with deionized water 3 to 5 times to remove residual soluble salt impurities. S5. Flash-dry the washed filter cake to obtain the active hydroxyapatite product.

2. The method for producing active hydroxyapatite as described in claim 1, characterized in that, In step S1, the mass concentration of P2O5 in the defluorinated dilute phosphoric acid is 8-12%, and the mass concentration of CaO in the lime slurry is 5-10%.

3. The method for producing active hydroxyapatite as described in claim 1, characterized in that, In step S2, the aging time of the reaction slurry is 20-50 minutes.

4. The method for producing active hydroxyapatite as described in claim 1, characterized in that, In step S3, the aging time of the calcium hydroxyphosphate suspension is 6-12 h, and the aging temperature is 40-60℃.

5. The method for producing active hydroxyapatite as described in claim 1, characterized in that, In step S4, the filter cake is washed three times with deionized water, and the amount of water added each time is 0.5 times the mass of the filter cake.