Preparation method and application of RS-HAP composite material

Abstract

The invention discloses a preparation method and application of an RS-HAP composite material, the RS-HAP composite material is risedronate nano-functionalized hydroxyapatite, and the risedronate nano-functionalized hydroxyapatite is prepared by adopting risedronate sodium, diammonium hydrogen phosphate and calcium chloride as raw materials. The risedronate and the hydroxyapatite are tightly combined through a coprecipitation method by utilizing the excellent chelation effect of the risedronate on cations, so that the problem of loose reactant combination in traditional physical mixing or modification is effectively avoided. Meanwhile, the adsorption performance of RS-HAP on heavy metal ions such as Pb < 2 + > and Co < 2 + > is greatly improved through the strong chelating capacity of oxygen atoms of a risedronate phosphonite group on cations, and the breakthrough improvement of the adsorption performance of traditional HAP is achieved; the adsorbent has the advantages of large adsorption capacity, high adsorption efficiency, simple and controllable preparation process, stable material structure, wide application scene, excellent regeneration performance and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water treatment materials, in particular to a preparation method of RS-HAP composite material and application thereof. BACKGROUND

[0002] With the discharge of a large amount of industrial and agricultural wastewater, environmental and ecological problems are becoming increasingly serious. Studies have shown that heavy metal ions and antibiotic pollutants in these industrial and agricultural wastewater are difficult to be effectively degraded and removed due to their chemical properties and stability. Once absorbed by aquatic organisms and plants, these pollutants will change their living habits, seriously affecting their reproductive capacity and survival rate. At the same time, these pollutants will also accumulate in aquatic organisms and eventually enter the human body through the food chain, causing great harm to the human digestive system and immune system. It is particularly important to note that the interaction between antibiotics and heavy metal ions will form more toxic complexes, posing a major threat to human health. Therefore, it is of great scientific significance and practical value to research and develop efficient removal methods.

[0003] Hydroxyapatite (HAP) is an important inorganic mineral and one of the main components of human bones and teeth; HAP has a large specific surface area and pore structure, and thus has good adsorption capacity for pollutants; at the same time, HAP contains a large number of active functional groups on its surface, such as hydroxyl and phosphate groups, which can chemically adsorb pollutant molecules and interact with pollutants through electrostatic interaction, hydrogen bonding or coordination bonding; in addition, HAP has good chemical stability and thermal stability, and its chemical structure will not be significantly damaged under general acidic or alkaline environments and conventional environmental temperature ranges; HAP also has the advantages of low cost, wide source of acquisition, recyclability and high biological safety.

[0004] However, the surface porosity, adsorption rate, adsorption capacity, stability and renewability of traditional HAP need to be further improved when it is used for water adsorption treatment. Therefore, physical mixing or ion doping modification is usually used in the prior art to improve the adsorption effect of HAP by adjusting the crystal structure or changing the surface properties. However, some preparation methods and composite / modification means in the prior art are too complex, resulting in excessive cost investment but limited effect improvement. At the same time, the HAP obtained by modification in the prior art generally has the problem of loose combination, which reduces its mass transfer efficiency and leads to poor treatment effect on wastewater and difficulty in regeneration.

[0005] Risedronate (RS) is the third generation of nitrogen-containing bisphosphonate with heterocyclic structure, and its R1substituent is hydroxyl group. Therefore, it has strong affinity to hydroxyapatite-based materials, and it also has strong chelation with electrophilic reagents such as heavy metal ions. Therefore, it is of great significance to introduce RS into suitable HAP materials to synthesize RS-HAP and study its adsorption capacity for heavy metal ions. SUMMARY

[0006] In order to solve the above problems, the application provides a preparation method of RS-HAP composite material and application thereof.

[0007] A preparation method of RS-HAP composite material, comprising the following steps: S1, taking a CaCl2 aqueous solution with a concentration of 0.05-0.2 mol / L, denoted as a first solution; S2, mixing sodium risedronate and diammonium hydrogen phosphate according to a ratio of 0.0381-0.2721 g:1.0564-1.2875 g to obtain a mixed solid, and then adding the mixed solid into deionized water according to a ratio of 1-2 g:100 mL to obtain a second solution; S3, opening constant temperature stirring of the first solution under a temperature condition of 30-50℃, and adding an equal volume of the second solution dropwise into the first solution during stirring, and maintaining the pH value at 8.0-10.0 during the dropwise adding process; after the dropwise adding is completed, stirring for 30 min, and then carrying out microwave treatment to obtain a mixed solution; S4, after the stirring is completed, naturally settling and aging the mixed solution at room temperature for 20-30 h, and carrying out solid-liquid separation to obtain a solid product, and carrying out cleaning, drying, grinding and sieving on the solid product to obtain the RS-HAP composite material.

[0008] Description: The above method utilizes the excellent chelation of risedronate to cations, so that risedronate and hydroxyapatite are closely combined by the coprecipitation method, effectively avoiding the problem of loose combination of reactants in traditional physical mixing or modification. At the same time, through the strong chelation of the oxygen atom of the phosphite group of risedronate to cations, the adsorption performance of RS-HAP to Pb 2+ , Co 2+ and other heavy metal ions is greatly improved, which realizes a breakthrough improvement in the adsorption performance of traditional HAP, and has many advantages such as large adsorption capacity, high adsorption efficiency, simple and controllable preparation process, stable material structure, wide application scenarios, excellent regeneration performance and the like.

[0009] Further, in S2, sodium risedronate and diammonium hydrogen phosphate are mixed according to a ratio of 0.0763 g:1.2545 g to obtain a mixed solid.

[0010] Note: The above ratio ensures that the phosphorus element accounts for 5% of the total phosphorus in the composite material. At this ratio, the adsorption performance of the RS-HAP composite material is optimal. This may be because adding an appropriate amount of RS promotes the formation of spherical hydroxyapatite with a smaller average diameter and a larger specific surface area. Conversely, excessively high levels of sodium risedronate will inhibit the nucleation and crystal growth of hydroxyapatite, while excessively low levels of sodium risedronate may not fully promote the growth of the raw materials.

[0011] Further, in S2, sodium risedronate and diammonium hydrogen phosphate are mixed in a ratio of 0.1526g:1.1885g to obtain a mixed solid.

[0012] Furthermore, in S3, the microwave processing time is 8~12 minutes; the microwave processing power is 600~800W.

[0013] Explanation: Microwave treatment allows energy to be transferred instantaneously to the entire solution, enabling the reaction system to reach the required temperature in a very short time; this, in turn, allows the ions (Ca) in the solution to... 2+ PO4 3- The RS molecules move and collide at extremely high speeds, leading to an instantaneous high degree of supersaturation in the solution. This triggers homogeneous nucleation, resulting in a massive number of tiny crystal nuclei forming rapidly. More importantly, during this rapid kinetic process, the RS molecules are simultaneously "involved" in the nucleation step, achieving "co-assembly" with the HAP precursor. This mechanism ensures that the RS molecules achieve molecular-level uniform dispersion in the HAP matrix. The surfaces of the newly formed massive number of microcrystal nuclei are rapidly adsorbed and passivated by RS molecules, effectively inhibiting further crystal growth. Simultaneously, the differentiated adsorption of RS molecules on each crystal facet is evenly distributed in the uniform microwave thermal field, thus smoothing out the differences in growth rates between crystal facets and promoting isotropic crystal growth. Ultimately, spherical RS-HAP composite materials with smaller dimensions, larger specific surface area, and regular morphology were successfully prepared.

[0014] Furthermore, in S3, the dropping rate is 3 drops / s, and the stirring speed is 200~400 rpm.

[0015] Note: Under the above-mentioned parameters, the prepared product exhibits good adsorption effect on heavy metal ions in wastewater.

[0016] Furthermore, in S3, the pH value is maintained by adjusting with diluted ammonia or hydrochloric acid.

[0017] Note: By maintaining the pH value to avoid drastic fluctuations, it can be ensured that RS-HAP crystals can grow uniformly and orderly.

[0018] Furthermore, in S4, the cleaning process involves sequentially washing with deionized water and an organic solvent; the washing is performed three times with water and three times with the organic solvent; the organic solvent is anhydrous ethanol or methanol.

[0019] Furthermore, in S4, the drying temperature is 50~80℃, and the drying time is 12~36h.

[0020] The present invention also discloses an application of an RS-HAP composite material, which is used to adsorb heavy metal ions in water.

[0021] Note: The above method demonstrates that the RS-HAP composite material achieves good results in the adsorption treatment of pollutants in water. Experiments show that the RS-HAP composite material effectively adsorbs Co. 2+ The adsorption capacity can reach 137.62 mg / g; the RS-HAP composite material has a high adsorption capacity for Pb. 2+ The adsorption capacity can reach 1259.21 mg / g.

[0022] The beneficial effects of this invention are: This invention utilizes the superior chelating effect of risephosphonate on cations to achieve a tight bond between risephosphonate and hydroxyapatite via co-precipitation, effectively avoiding the problem of loose reactant bonding in traditional physical mixing or modification. Simultaneously, the strong chelating ability of the oxygen atoms in the phosphonite group of risephosphonate on cations significantly enhances the adsorption performance of RS-HAP for heavy metal ions such as Pb²⁺ and Co²⁺, achieving a breakthrough improvement over traditional HAP adsorption performance. It boasts numerous advantages, including large adsorption capacity, high adsorption efficiency, simple and controllable preparation process, stable material structure, wide applicability, and excellent regeneration performance. Furthermore, this invention discovers that, unlike conventional techniques, the higher the amount of RS used in the synthesis of RS-HAP composite materials, the worse the crystallinity and the more amorphous components. This invention, by carefully controlling the amount of RS added, can ensure the aforementioned performance while avoiding any negative impact of RS on the HAP material. Attached Figure Description

[0023] Figure 1 These are the XRD spectra of the HAP obtained in Comparative Example 1 and the RS-HAP obtained in Example 1 of this invention; Figure 2 The images show the N2 adsorption-desorption isotherms (A) and the corresponding pore size distribution diagram (B) for Example 1 and Comparative Example 1 of this invention. Figure 3 These are SEM / EDS images of HAP (AC) in Comparative Example 1 and RS-HAP (BD) in Example 1 of this invention; Figure 4 This describes the effect of the optimal dosage ratio of the modifier on the adsorption effect in Example 1 of the present invention. Figure 5 This relates to the effect of solution pH on the adsorption capacity in Example 1. Figure 6 This invention describes the effect of different initial concentrations on the adsorption capacity of RS-HAP in Example 1 and HAP in Comparative Example 1. Figure 7 These are the isothermal fitting curves of the HAP of Comparative Example 1 and the RS-HAP of Example 1 for pollutants in this invention; Figure 8 This invention describes the effect of contact time on adsorption performance of HAP in Comparative Example 1 and RS-HAP in Example 1, as well as related pseudo-first-order kinetics, pseudo-second-order kinetics simulations, Elovich equation simulations (AB), and internal diffusion kinetics simulations (CD). Figure 9 This is a fitting graph of the thermodynamic linear equations for pollutant adsorption by HAP in Comparative Example 1 and RS-HAP in Example 1 of the present invention; Figure 10 These are the XRD patterns of different heavy metal ions before and after adsorption in Example 1 of this invention; Figure 11 These are the XPS full spectrum (A) and Ca 2p (B) of RS-HAP before and after adsorption of pollutants in Example 1 of the present invention; Figure 12 This refers to the O before and after RS-HAP adsorption in Example 1 of the present invention. 1s XPS energy spectrum; Figure 13 These are the extreme points of ESP (A) and ALIE (B) on the surface of ionized RS molecules in Experimental Example 3 of this invention; HOMO (C) and LUMO (D) of ionized RS (C-cyan, O-red, H-white, N-blue, P-brown); Figure 14 These are the initial visualization snapshot (A) of the system constructed in Experimental Example 3 of this invention and the visualization snapshot (BCD) after the completion of the MD simulation; (C-gray, Ca-green, O-red, H-white, N-blue, P-pink, Pb-black, Co-orange). Detailed Implementation

[0024] To further illustrate the methods and effects of this invention, the technical solution of this invention will be clearly and completely described below in conjunction with experiments.

[0025] Example 1: A method for preparing an RS-HAP composite material, comprising the following steps: S1. Take a CaCl2 aqueous solution with a concentration of 0.167 mol / L, and denote it as the first solution; S2. Sodium risedronate and diammonium hydrogen phosphate were mixed at a ratio of 0.0763 g: 1.2545 g to obtain a mixed solid; then the mixed solid was added to deionized water at a ratio of 1.3206 g: 100 mL, and this was referred to as the second solution. S3. The first solution is kept at a constant temperature of 40°C with stirring. While stirring, an equal volume of the second solution is added dropwise to the first solution. During the dropwise addition, the pH value is maintained at 8.0~10.0. After the dropwise addition is completed, the mixture is stirred for another 30 minutes, and then microwaved to obtain a mixed solution. The microwave treatment time is 10 minutes, and the microwave power is 700W. The dropwise addition rate is 3 drops / s, and the stirring speed is 300 rpm (to avoid excessive stirring and liquid splashing). The pH value is maintained by adjusting with 1% ammonia solution. S4. After stirring, the mixture is allowed to settle naturally at room temperature and aged for 24 hours; then solid-liquid separation is performed to obtain a solid product. The solid product is then washed, dried, ground, and sieved to obtain the RS-HAP composite material. The washing is performed sequentially with deionized water and an organic solvent. The washing is repeated three times with water and organic solvent respectively. The organic solvent is anhydrous ethanol or methanol. The drying temperature is 60°C, and the drying time is 24 hours.

[0026] Example 2: The difference between this example and Example 1 is that the mixing ratio of sodium risedronate and diammonium hydrogen phosphate is different. Sodium risedronate and diammonium hydrogen phosphate are mixed in a ratio of 0.0381g:1.2875g (so that the proportion of P element in sodium risedronate in the total P element is 2.5%) to obtain a mixed solid.

[0027] Example 3: The difference between this example and Example 1 is that the mixing ratio of sodium risedronate and diammonium hydrogen phosphate is different. Sodium risedronate and diammonium hydrogen phosphate are mixed in a ratio of 0.1526g:1.1885g (so that the proportion of P element in sodium risedronate in the total P element is 10%) to obtain a mixed solid.

[0028] Example 4: The difference between this example and Example 1 is that the mixing ratio of sodium risedronate and diammonium hydrogen phosphate is different. Sodium risedronate and diammonium hydrogen phosphate are mixed in a ratio of 0.2721g:1.0564g (so that the proportion of P element in sodium risedronate in the total P element is 20%) to obtain a mixed solid.

[0029] Example 5: This example differs from Example 1 in that: S1, a 0.05 mol / L CaCl2 aqueous solution is taken; S2, the mixed solid is added to deionized water at a ratio of 1 g: 100 mL; S3, the first solution is stirred at a constant temperature of 30°C; the microwave treatment time is 8 min; the microwave power is 600 W; the stirring speed is 200 rpm; S4, after stirring, the mixture is allowed to settle naturally at room temperature and aged for 20 h; the drying temperature is 50°C and the drying time is 12 h.

[0030] Example 6: This example differs from Example 1 in that: S1, a 0.2 mol / L CaCl2 aqueous solution is taken; S2, the mixed solid is added to deionized water at a ratio of 2 g: 100 mL; S3, the first solution is stirred at a constant temperature of 50°C; the microwave treatment time is 12 min; the microwave power is 800 W; the stirring speed is 400 rpm; S4, after stirring, the mixture is allowed to settle naturally at room temperature and aged for 30 h; the drying temperature is 80°C and the drying time is 36 h.

[0031] This invention also provides an application of the RS-HAP composite material, which is used to adsorb heavy metal ions in water.

[0032] Comparative Example 1: Unlike Example 1, this example did not use sodium risedronate, but only used solid diammonium hydrogen phosphate to prepare the second solution, and the product obtained was HAP material.

[0033] The RS-HAP composite material prepared in Example 1 and the HAP material obtained in Comparative Example 1 were characterized and analyzed, and compared through experimental adsorption (the process is described in Experiments 1-3 below) to highlight the advantages of the embodiments of the present invention. Experimental studies revealed that, compared to Comparative Example 1, the adsorption capacity of Example 1 in the water treatment adsorption process increased from 105.09 mg / g (Co) in Comparative Example 1. 2+ ) and 980.21 mg / g (Pb 2+ Increased to 137.62 mg / g (Co) 2+ ) and 1259.21 mg / g (Pb 2+Kinetic results show that the adsorption process conforms more closely to a pseudo-second-order kinetic model, indicating that the main rate-limiting steps of these adsorption processes are more likely to be controlled by chemisorption. In all adsorption processes, intraparticle diffusion is not the main rate-limiting factor. Adsorption thermodynamics indicates that increasing ambient temperature favors the adsorption process. Based on electrostatic potential and average local ionization energy analysis, the sites where RS readily undergoes nucleophilic / electropophilic reactions were identified. MD simulations were performed using MS in the Forcite module to obtain the interaction between RS and HAP, specifically the PO3H in RS. - The strong interaction between the O atom and the Ca atom in HAP is dominant, and RS affects Pb. 2+ and Co 2+ The interaction strength of RS-HAP is stronger than that of HAP, which is why RS-HAP is more effective against Pb than HAP. 2+ and Co 2+ The reason for its stronger adsorption effect.

[0034] RS-Na appears as a fine white to grayish-white crystalline powder with a melting point of 252-262°C and a boiling point of 692.3°C (760 mmHg). It has a heterocyclic structure and its R1 substituent is a hydroxyl group. Therefore, it has a strong affinity for hydroxyapatite-based materials. In the synthesis process of this invention embodiment, the proportion of P element in RS-Na to the total P element was 2.5%, 5%, 10%, and 20%, respectively. That is, 0.0381 g, 0.0763 g, 0.1526 g, and 0.2721 g of RS-Na samples were weighed and mixed with 1.2875 g, 1.2545 g, 1.1885 g, and 1.0564 g of (NH4)2HPO4 to obtain a mixed solution of organophosphonic acid and inorganic phosphorus. The prepared samples were named according to the proportion of P element in RS-Na to the total P element: 2.5RS-HAP (RS-HAP composite material prepared in Example 2), 5RS-HAP (RS-HAP composite material prepared in Example 1), 10RS-HAP (RS-HAP composite material prepared in Example 3), and 20RS-HAP (RS-HAP composite material prepared in Example 4).

[0035] Experimental Example 1: Sample Characterization (1) XRD analysis; Figure 1The XRD patterns of the prepared HAP and RS-HAP with different modifier ratios are shown. The figures show that the prepared HAP is highly crystalline, with sharp and separable characteristic peaks at 2θ = 31.80°, 32.85°, and 34.04°, corresponding to its (211), (300), and (202) crystal planes, respectively. Other characteristic diffraction peaks can also be observed using Ca... 10 (PO4)6(OH)2 (JCPDS No. 97-015-74811, space group P63 / m (176)) is indexed by the standard card. As the proportion of modifier RS ​​increases, its crystallinity deteriorates, impurity peaks gradually increase, and the peak intensity of characteristic peaks decreases. When the content of modifier RS ​​is 2.5%, it can be seen from 2.5RS-HAP that the diffraction peaks of its (211) and (300) crystal planes have overlapped into a broad peak. When the content of modifier RS ​​is 5%, in addition to the two main diffraction peaks overlapping into a broad peak, the diffraction peak at the (202) crystal plane also disappears. When the content of modifier RS ​​is 10%, the main diffraction broad peak also disappears, and the crystallinity is so poor that it is difficult to see Ca. 10 Characteristic peak of (PO4)6(OH)2.

[0036] In the preparation of RS-HAP composite materials, the deprotonated riseronic acid groups can strongly chelate with calcium ions in solution to form calcium riseronic acid, thereby occupying lattice positions in the nucleation and growth stages of HAP crystals. This inhibits the nucleation and crystal growth of hydroxyapatite to some extent, thus synthesizing an amorphous material containing a certain amount of calcium riseronic acid. Therefore, in the synthesis of RS-HAP composite materials, the higher the amount of RS used, the worse the crystallinity and the more amorphous components.

[0037] (2) BET analysis; The 5RS-HAP composite material obtained in Example 1 was used as a representative of RS-HAP and compared with the original HAP for N2 adsorption-desorption, SEM, and EDS tests. The results of the N2 adsorption-desorption curves and pore size distribution diagrams are as follows. Figure 2 As shown in Table 1, relevant parameters such as specific surface area, pore volume, and average pore size are presented.

[0038] Table 1. Specific surface area, average pore size, and pore volume parameters of HAP and RS-HAP

[0039] pass Figure 2As can be seen from Figure A, the adsorption isotherms of RS-HAP and HAP belong to type IV isotherms. At low relative pressures (P / P0), the adsorption and desorption curves almost overlap, indicating that both adsorbents have relatively few micropores. With increasing relative pressure, both materials exhibit H3-type hysteresis loops at higher relative pressures due to capillary condensation. This significant hysteresis indicates that both adsorbents possess mesoporous structures. Furthermore, according to the relevant parameters in Table 1, the average pore size of the modified RS-HAP decreased from 82.13 nm to 55.21 nm, but the specific surface area increased from 63.24 m² / s². 2 / g increased to 123.21 m 2 / g, and the total pore volume also increased from 0.36 to 0.48 cm³. 3 / g. Furthermore, this study used the JBH method to investigate the pore size distribution of the two adsorbents, and the results are as follows: Figure 2 As shown in Figure B, the pore size distribution of both RS-HAP and HAP is dominated by macropores larger than 50 nm.

[0040] (3) SEM and EDS analysis; Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) results of the two adsorbents in Example 1 and Comparative Example 1 are shown in the figure. Figure 3 From the SEM image of the sample (in the middle). Figure 3 (AB) It can be clearly observed that the addition of the modifier RS ​​significantly altered the morphology of HAP. The synthesized HAP exhibited a slender rod-like structure; however, the morphology of RS-HAP modified with RS changed significantly, exhibiting a spherical structure. Eds results for both materials ( Figure 3 As shown in CD), the calcium-to-phosphorus ratio of the synthesized HAP is approximately 31.52 / 19.10 = 1.65. Considering experimental and instrumental errors, the test result is basically consistent with the theoretical calcium-to-phosphorus ratio of 1.67. The calcium-to-phosphorus ratio of the modified RS-HAP is approximately 18.26 / 10.69 = 1.71, indicating that the addition of the modifier did not change the calcium-to-phosphorus ratio of RS-HAP. The modified RS-HAP contains nitrogen (N) compared to the original HAP, which proves that RS-HAP was successfully prepared.

[0041] Experiment Example 2: Adsorption Experiment (I) Investigation of adsorption experimental conditions; (1) Investigating the effect of the optimal dosage ratio of the modifier on the adsorption capacity of the adsorbent: Experiments were conducted using prepared HAP, 2.5RS-HAP, 5RS-HAP, 10RS-HAP, and 20RS-HAP. The mass of the adsorbent... m = 20 mg; volume of pollutant solutionV =40 mL; initial concentration of pollutant solution C 0 = 1200 mg / L (Pb) 2+ ) C 0 = 250 mg / L (Co 2+ ) C 0 = 80 mg / L (TC); initial pH of pollutant solution = 5; ambient temperature of adsorption experiment T = 25 ℃; adsorption time t = 24 h; (2) Study on the effect of initial solution pH on adsorption capacity during adsorption: The initial pH of the solution was adjusted using different concentrations of NaOH or HCl (0.01M, 0.1M, and 1M) to ensure the initial pH of the heavy metal solution was within the range of 2.5-5. The mass of the adsorbent... m = 20 mg; volume of pollutant solution V = 40 mL; Initial concentration of pollutant solution C 0 = 1200 mg / L (Pb) 2+ ), C 0 = 250 mg / L (Co 2+ ); Ambient temperature of the adsorption experiment T = 25 ℃; adsorption time t = 24 hours.

[0042] (3) Study the initial concentration of heavy metal ions during the adsorption process C Effect of 0 on the adsorption capacity of the adsorbent: mass of the adsorbent m = 20 mg; volume of pollutant solution V =40mL; Initial concentration of pollutant solution C 0 = 100-1400 mg / L (Pb) 2+ ) C 0 = 25-300 mg / L (Co 2+ ); Initial pH of the pollutant solution = 5; Ambient temperature for the adsorption experiment. T= 25 ℃; adsorption time t = 24 hours.

[0043] (4) Investigate the effect of adsorption time t on adsorption capacity: mass of adsorbent m = 20 mg; volume of pollutant solution V =40 mL; initial concentration of pollutant solution C 0 = 1200 mg / L (Pb)2+ ), C 0 = 250 mg / L (Co 2+ ); Initial pH of the pollutant solution = 5; Ambient temperature of the adsorption experiment. T= 25℃.

[0044] (5) Study the effect of ambient temperature on adsorption capacity: adsorbent mass m = 20 mg; volume of pollutant solution V =40 mL; initial concentration of pollutant solution C 0 = 1000 mg / L (Pb) 2+ ) C 0 = 50 mg / L (Co 2+ ); Initial pH of the pollutant solution = 5; Ambient temperature T = 25-65℃. Adsorption time. t = 24 hours.

[0045] II. Investigation into the optimal dosage ratio of the modifier; The prepared HAP and RS-HAP with different modifier ratios were added to Pb. 2+ and Co 2+ Adsorption tests were conducted in the solution, and the experimental results are as follows: Figure 4 As shown in the figure, it can be observed that the adsorption capacity of the RS-HAP composite material for the two pollutants increases with the increase of the modifier content. However, when the modifier ratio reaches 5%, the adsorption capacity for the two different pollutants reaches its maximum value, and further increasing the modifier content leads to a decrease in adsorption capacity. This may be because RS inhibits the nucleation and crystal growth of hydroxyapatite. To a certain extent, adding an appropriate amount of RS promotes the formation of spherical hydroxyapatite with a smaller average diameter and a larger specific surface area. However, excessive RS will destroy the structure of hydroxyapatite, causing it to lose its adsorption capacity.

[0046] The modifier significantly improved the adsorption performance of the composite material. The adsorption capacity increased from the initial 105.09 mg / g (Co) 2+ ) and 980.21 mg / g (Pb 2+ Increased to 137.62 mg / g (Co) 2+ ) and 1259.21 mg / g (Pb 2+ Therefore, in subsequent studies, to achieve the best adsorption effect, 5% RS-HAP with a 5% modifier ratio will continue to be used as the optimal adsorbent material, and a comparative study will be conducted with HAP. 5% RS-HAP will be abbreviated as RS-HAP.

[0047] III. Investigating the effect of solution pH on adsorption capacity; The initial pH of the solution affects Co 2+ and Zn 2+ The adsorption of Pb is significantly affected. Therefore, the effects of HAP and RS-HAP on Pb adsorption at different pH values ​​were investigated. 2+ and Co 2+ The adsorption of Pb. 2+ and Co 2+ Hydroxide precipitates are formed under highly alkaline conditions. Experiments were conducted with initial solution pH ranging from 2.5 to 5. The experimental results are as follows: Figure 5 As shown in Figure AB, it can be seen that as the pH value increases, RS-HAP affects Pb. 2+ and Co 2+ The adsorption capacity gradually increases, while for HAP, only the adsorption capacity for Co increases with the increase of the initial solution pH. 2+ The adsorption capacity of Pb was significantly improved. 2+ An abnormal phenomenon occurred. Because the higher the pH value, the more charged neutral ≡Ca-OH and negatively charged ≡PO in the HAP... - The higher the concentration of HAP, the stronger the electrostatic interaction between HAP and heavy metal ions, which is beneficial to the PO4 group of HAP. 3- Complexation with heavy metal ions. However, HAP has a negative effect on Pb. 2+ The adsorption capacity of the hydroxyapatite-based material did not increase with increasing pH; instead, it first increased and then decreased. This anomaly may be due to the hydroxyapatite-based material's adsorption capacity for Pb. 2+ The adsorption mechanism, in addition to ion substitution and surface complexation, also involves dissolution and the formation of new Ca. 2.5 Pb 7.5 (PO4)6(OH)2 and Pb 10 (PO4)6(OH)2 precipitate is more readily dissolved by HAP and forms new precipitates in low pH solutions. Therefore, HAP has a positive effect on Pb. 2+ The adsorption capacity does not simply increase with the increase of solution pH.

[0048] Compared to HAP, RS-HAP showed decreased resistance to Co with increasing pH. 2+ The adsorption capacity changes more significantly because RS in RS-HAP can form stable complexes with heavy metal ions. As the solution pH increases, the complexation of RS with metal ions becomes stronger, further facilitating the formation of stable complexes between RS and heavy metal ions. This also leads to an increase in Pb adsorption capacity. 2+ The adsorption rate on RS-HAP increased with increasing initial pH. At the same initial solution pH, RS-HAP showed higher adsorption capacity for both metal ions compared to HAP. This was confirmed by zeta potential plots of HAP and RS-HAP.Figure 5 C) It can be seen that the pH of HAP and RS-HAP pzc The zeta potentials were 2.85 and 2.59, respectively, with the negative value increasing with increasing pH. Furthermore, at the same pH, the zeta potential of RS-HAP was lower than that of HAP, making RS-HAP more conducive to binding with positively charged heavy metal cations. Additionally, due to the abundance of adsorption active sites for heavy metal ions in the porous and amorphous RS-HAP, it exhibits a strong chelation ability with metal ions. Moreover, RS can act as a bridge between metal ions and HAP, forming a HAP-RS-metal ion ternary surface complex. All of these factors contribute to the enhanced affinity of RS-HAP for Pb. 2+ and Co 2+ The adsorption capacity of [a substance] is higher than that of HAP.

[0049] IV. Study on the effect of initial concentration on adsorption capacity; This section of the study investigated the effects of different initial concentrations on the adsorption capacity of RS-HAP and HAP. Both adsorbents, Pb, were added to pollutant solutions of varying concentrations. 2+ The initial concentration range is 100-1400 mg / L, Co 2+ It ranges from 25-300 mg / L. (From Pb) 2+ Adsorption results Figure 6 As observed in A, within the low heavy metal ion concentration range (100-600 mg / L), HAP and RS-HAP have a significant effect on Pb. 2+ The adsorption amounts are almost equal, and increase almost linearly with increasing initial concentration. When Pb 2+ As the initial concentration continued to increase, the adsorption capacity of RS-HAP gradually exceeded that of HAP. Finally, at initial concentrations of 1200 and 1000 mg / L, RS-HAP and HAP reached equilibrium adsorption capacities of 1259.21 mg / g and 980.21 mg / g, respectively. For Co... 2+ As an adsorbate ( Figure 6 B) Within the initial concentration range of the experiment, the adsorption capacity of RS-HAP was consistently higher than that of HAP. When Co 2+ When the initial concentration was 250 mg / L, the equilibrium adsorption capacities of RS-HAP and HAP were 137.62 mg / g and 105.09 mg / g, respectively.

[0050] V. Adsorption isotherm study; Table 2 Adsorption isotherm constants of RS-HAP and HAP for different pollutants in Example 1

[0051] Figure 7The fitting data of the Langmuir and Freundlich models obtained by nonlinear fitting of the experimental results are presented. The relevant fitting parameters are shown in Table 2. From the relevant data, it can be concluded that the Langmuir isotherm model fits the adsorption process of the two heavy metal ions on RS-HAP and HAP. R 2 The value is higher than the fit of the Freundlich model. R 2 This means that all adsorption processes in the study tended to be monolayer adsorption, and the adsorbent surface was relatively uniform. Based on the fitting results of the Langmuir isotherm model, RS-HAP and HAP for Pb... 2+ Theoretical maximum adsorption capacity q m The concentrations were 1310.06 mg / g and 984.36 mg / g, respectively. Regarding Co... 2+ Adsorption, two adsorbents q m The concentrations were 167.86 mg / g and 126.58 mg / g, respectively, which are basically consistent with the experimental results. The adsorption process obtained by fitting the Langmuir isotherm model... R L The values ​​are all in the range of 0-1, indicating that the adsorption of pollutants by the adsorbent is positive under these conditions. The values ​​obtained from fitting the Freundlich isotherm model... n The values ​​are all between 1 and 10, indicating that various adsorption processes can proceed well.

[0052] VI. Adsorption time and adsorption kinetics studies; Figure 8 The data shows the changes in the adsorption capacity of RS-HAP and HAP for two heavy metal pollutants in solution with adsorption time. It can be observed that the adsorption process of the two adsorbents for the two heavy metal ions in solution can be divided into three stages: a rapid adsorption stage, a slow adsorption stage, and an adsorption equilibrium stage. In the rapid adsorption stage, the adsorption capacity increases rapidly and linearly. This is because there are a large number of active adsorption sites on the adsorbent surface, which can quickly bind to the pollutants in the solution, leading to a rapid increase in adsorption capacity. Next, in the slow adsorption stage, the adsorption rate begins to slow down. This is likely because in the rapid adsorption stage, the adsorbent has already bound to a large amount of pollutants, so the remaining active adsorption sites gradually decrease, resulting in a decrease in the adsorption rate. After completing the first two stages, the adsorption capacity gradually stabilizes, entering the adsorption equilibrium stage. In this stage, the active sites of the adsorbent are almost saturated, and only a few remaining active sites can continue to adsorb pollutants. Even if the adsorption time continues to increase, the adsorption capacity will only change slightly.

[0053] Based on the experimental data, the quasi-first-order kinetic model, quasi-second-order kinetic model, and Elovich model were used for fitting, and the relevant fitting results were obtained as follows: Figure 8 As shown in AB. Table 3 lists the parameters of each fitting result. The fitting parameters are obtained by comparing the various dynamic models. R 2 Value and χ 2 The values ​​revealed that in the adsorption fitting results of RS-HAP and HAP for the two heavy metal pollutants, except for RS-HAP for Co, the adsorption of Co was relatively consistent. 2+ Apart from adsorption, other cases obtained using a pseudo-second-order kinetic model R 2 The value is relatively high, and at the same time χ 2 The values ​​are relatively low. The above results indicate that the pseudo-second-order kinetic model is more consistent with reality in most adsorption processes, suggesting that the main rate-limiting steps of these adsorption processes are more likely to be controlled by chemisorption. Using the pseudo-second-order kinetic model for fitting, the obtained RS-HAP and HAP values ​​for Pb... 2+ Adsorption equilibrium adsorption capacity q e The concentrations were 1296.10 mg / g and 1064.02 mg / g, respectively, for Co. 2+ of q e The values ​​were 137.77 mg / g and 107.38 mg / g, respectively. These were obtained through fitting calculations. q e The numerical value is close to the actual adsorption capacity of the adsorbent for pollutants.

[0054] Table 3 Adsorption kinetic parameters of pollutants by RS-HAP and HAP

[0055] Based on the kinetic experimental data, an intraparticle diffusion model was used to fit the data, and the corresponding fitting results were obtained, such as... Figure 8 As shown in CD, the relevant parameters are also listed in Table 4. Observing the fitting results, it can be seen that the adsorption processes of RS-HAP and HAP for the two heavy metal pollutants can be divided into three stages. Furthermore, the three stages corresponding to each adsorption process... k i The value satisfies k 1 >k 2 >k 3 The order, and the intercept of each line obtained by fitting. C iNone of them are equal to 0. Based on the above experimental results, it can be concluded that in this experiment, intraparticle diffusion is not the main rate-limiting factor for adsorption.

[0056] Table 4 shows the kinetic parameters obtained by fitting the intraparticle diffusion kinetic model.

[0057] VII. Adsorption thermodynamics studies; The linear fitting results of the RS-HAP in Example 1 and the HAP in Comparative Example 1 for the thermodynamic experiments of the two heavy metal ions are as follows: Figure 9 As shown in Table 5, the relevant thermodynamic parameters are presented. From the table, the ΔE values ​​for the adsorption processes of the two adsorbents for the two heavy metal pollutants, calculated through fitting, can be observed. H o The values ​​are all greater than zero, indicating that the adsorption process is accompanied by an exothermic reaction, and that an increase in ambient temperature is beneficial to the adsorption of the two heavy metals by the two adsorbents. The Δ values ​​for all adsorption processes... S o The values ​​are all greater than zero, indicating that the disorder of the system increases as the adsorption process proceeds. At different temperatures, the values ​​for all adsorption processes... △G o The values ​​are all negative, indicating that all adsorption processes occur spontaneously. Furthermore, △G o The lower the value, the stronger the spontaneity of the adsorption process. The table shows that, compared to the original HAP, the adsorption of the two heavy metal ions... △G o Value, adsorption process of two heavy metal ions by RS-HAP △G o The values ​​are all relatively small, indicating that under the same conditions, RS-HAP exhibits stronger spontaneity in the adsorption of the two heavy metals. As the temperature increases, the adsorption processes... △G o The value gradually decreased, indicating that higher ambient temperatures are more conducive to the adsorption process. This can be explained by the fact that as the temperature rises, the activity of heavy metal ions in the pollutant solution increases, their movement speed accelerates, and thus more pollutants are adsorbed by the adsorbent.

[0058] Table 5 Thermodynamic parameters of pollutants adsorbed by RS-HAP and HAP

[0059] Experiment 3: Study on the adsorption mechanism; The study of adsorption mechanisms typically requires the integration of multiple characterization techniques and simulations to obtain comprehensive information. By comprehensively utilizing various characterization techniques and simulation methods, the interaction between the adsorbent and adsorbate during the adsorption process can be investigated from multiple perspectives, revealing key links and influencing factors in the adsorption mechanism, and providing important theoretical guidance and experimental basis for the design and optimization of adsorption materials. Here, RS-HAP will be used to adsorb Co. 2+ and Pb 2+ The samples were then designated RS-HAP-Co and RS-HAP-Pb.

[0060] according to Figure 10 The XRD patterns shown reveal the effect of RS-HAP material on Pb. 2+ and Co 2+ Characteristics after adsorption. From Figure 10 A can be observed that RS-HAP adsorbs Co. 2+ Its crystallinity decreased afterward, but the main diffraction peak of the (211) crystal plane could still be clearly observed. Furthermore, the 2θ value of the main diffraction peak also changed slightly, decreasing from 31.95° to 31.82°. This change may be due to the Ca inside RS-HAP during adsorption. 2+ The ion (ionic radius of 0.99 Å) is affected by Co with a smaller ionic radius. 2+ The adsorption of ions with an ionic radius of 0.75 Å results in a slight change in the cell size of the RS-HAP after adsorption.

[0061] In addition, through Figure 10 B can be observed that RS-HAP adsorbs Pb. 2+ A new phase, Pb, was subsequently formed. 10 (PO4)6(OH)2. Therefore, based on the characterization results and previous studies, it can be concluded that on RS-HAP, Co 2+ The adsorption-driven mechanism mainly involves Co 2+ The complex reactions between the RS-HAP surface and multiple active sites, and Co 2+ It diffuses into the internal structure of RS-HAP and reacts with the Ca in the solution. 2+ Perform a substitution. And for Pb... 2+ The adsorption driving force includes the adsorption of Co. 2+ Similar surface complexing and ion exchange interactions, as well as in Pb 2+ Rapid dissolution of RS-HAP in solution leads to the formation of more difficult-to-dissolve Pb. 10 (PO4)6(OH)2. These mechanisms work together to drive Pb 2+ Adsorption process on RS-HAP.

[0062] ①XPS analysis; Figure 11 A shows the XPS scan total spectra of three samples. Each total spectrum shows the presence of Ca, P, and O elements, representing the basic elemental composition of HAP. Furthermore, adsorbed Co... 2+ and Pb 2+ Co 2p and Pb 4f peaks were also observed in the subsequent samples, which provided evidence for the successful adsorption of heavy metal ions by RS-HAP. Figure 11 B shows the Ca element peaks of the three samples. It can be seen that the binding energies of the Ca 2p1 / 2 and Ca 2p3 / 2 peaks of RS-HAP are 351.09 eV and 347.44 eV, respectively. RS-HAP adsorbs Co. 2+ Subsequently, the binding energies of its Ca 2p1 / 2 and Ca 2p3 / 2 peaks decreased to 351.48 eV and 347.77 eV, respectively. This may be due to the presence of Co in the contaminant solution. 2+ With Ca in RS-HAP 2+ Ion exchange occurred. It is noteworthy that when RS-HAP adsorbed Pb... 2+ Subsequently, besides the changes in the binding energies of the Ca 2p1 / 2 and Ca 2p3 / 2 peaks due to ion exchange, the intensity of the Ca peak also became lower and more disordered. This may be due to the adsorption of Pb by RS-HAP. 2+ New Pb was subsequently formed. 10 This is caused by the (PO4)6(OH)2 phase. RS-HAP and O in both samples 1s XPS spectra, such as Figure 12 As shown, the spectrum can be decomposed into three peaks: 533.24 eV, representing oxygen in bound water; 532.91 eV, representing oxygen in the hydroxyl group (OH) on RS-HAP; and 530.86 eV, representing oxygen in the phosphate group of phosphonate or oxygen in the metal oxide (MO).

[0063] from Figure 12 As can be seen from AB, when RS-HAP adsorbs Co 2+ Subsequently, the content of OH functional groups decreased from 46.55% to 30.74%, while the content of MO functional groups increased from 50.13% to 66.56%. This may be because Co... 2+ Surface complexation adsorption occurs on the RS-HAP surface, which greatly reduces the number of OH groups on the RS-HAP surface and forms a large number of (≡PO) groups. n Co (2-n)+ Or (≡CaO) n Co (2-n)+ .

[0064] However, in Pb2+ Regarding adsorption, O 1s The XPS results, however, differed from Co. 2+ There are significant differences, although related studies have shown that Pb can also undergo surface complexation adsorption on RS-HAP. From Figure 12 As can be seen from BC, Pb adsorption 2+ O after 1s The XPS results changed significantly, likely due to the adsorption of Pb by RS-HAP. 2+ New Pb was subsequently generated. 10 (PO4)6(OH)2, which leads to a significant change in the number and ratio of MO and OH functional groups.

[0065] ② Visualization studies based on DFT and MD; Here, the extreme point distributions of ESP and ALIE on the surface of RS molecules with two negative charges at pH 9 are shown, along with their HOMO and LUMO plots. Figure 13 ),from Figure 13 As can be seen from ABC, the minimum point of ESP on RS, the minimum point of ALIE, and the site where HOMO contributes significantly are all located near the O of the phosphonate group on RS. This indicates that the electron cloud density is lowest at this location, and the electron binding is weakest, making it the preferred site for electrophilic reactions. Similarly, according to... Figure 13 As can be seen from ABD, the maximum value of ESP and the site where LUMO contributes significantly are both near the N end of the RS carbon chain, indicating that this is the preferred site for nucleophilic reactions.

[0066] To further analyze the possible mechanisms of the interaction between RS and HAP surfaces, molecular dynamics (MD) simulations were performed using MS in the Forcite module. Figure 14 A is the initial snapshot before the MD simulation; RS is far from HAP. Figure 14 B is a snapshot after the MD simulation is completed. It can be seen that RS is very close to the HAP surface, and a small portion of Ca in the HAP... 2+ It has been released from HAP and is now in the solution. The radial distribution function (RDF) is often used to show interactions between different species, where O... RS -Ca HAP This refers to the interaction between O in RS and Ca in HAP. Other identifiers are similar, and the corresponding RDF results are as follows. Figure 14 As shown in Figure C. The figure clearly shows the O atom of the phosphonite group in RS and the PO4 atom of HAP. 3− The O atoms and Ca atoms of the group (O and Ca respectively) RS -Ca HAP and O HAP -Ca HAP They all have strong interactions.RS -Ca HAP and O HAP -Ca HAP The strongest peaks appeared in the same location ( r =2.36 Å), but the relative intensities (g(r)) of the former and the latter are 28.9 and 13.5, respectively, indicating that the organophosphine group and phosphonite group of RS are related to Ca 2+ The chelation effect is stronger than that of HAP's PO4 3− With Ca 2+ The complexation effect of RS. Therefore, during the preparation of RS-modified HAP composites, some of the phosphonite groups in RS will combine with Ca in HAP, thus affecting the crystallinity of HAP, which is consistent with the XRD results. Meanwhile, according to N... RS -O HAP and H RS -O HAP The calculations revealed that the NO bond and hydrogen bond interactions between RS and HAP are very weak. Therefore, the interaction between RS and HAP is primarily due to the presence of PO3H in RS. - The strong interaction between the O atoms and the Ca atoms in HAP is the main factor.

[0067] Add Pb 2+ and Co 2+ Then, and a snapshot after the MD simulation is completed, such as... Figure 14 DE, from which we can see that Co 2+ It was adsorbed near RS, while Pb 2+ It is adsorbed at the interface between the RS and HAP forces. The corresponding RDF results also show that RS influences Pb. 2+ and Co 2+ The effects of RS-HAP on Pb are all stronger than those of HAP, which confirms the experimental results showing that RS-HAP has a stronger effect on Pb than HAP. 2+ and Co 2+ The adsorption effect is better.

[0068] In summary, this embodiment provides a method for synthesizing RS-HAP and using it for Pb removal. 2+ and Co 2+ Based on the comprehensive experimental results and theoretical calculations, the following conclusions can be drawn: (1) The modifier significantly improved the adsorption performance of the composite material. The adsorption capacity increased from the initial 105.09 mg / g (Co) 2+ ) and 980.21 mg / g (Pb 2+ Increased to 137.62 mg / g (Co) 2 + ) and 1259.21 mg / g (Pb 2+(2) Fitting of Langmuir isotherm model during the adsorption of two heavy metal ions on RS-HAP and HAP. R 2 The value is higher than the fit of the Freundlich model. R 2 Value. This means that all adsorption processes in the study tend to be monolayer adsorption, and the adsorbent surface is relatively uniform. Adsorption thermodynamics studies show that an increase in ambient temperature is more conducive to the adsorption process. (3) Kinetic results show that among the adsorption fitting results of RS-HAP and HAP for the two heavy metal pollutants, except for RS-HAP for Co 2+ Apart from adsorption, other cases obtained using a pseudo-second-order kinetic model R 2 The value is relatively high, and at the same time χ 2 The values ​​are relatively low. The above results indicate that the pseudo-second-order kinetic model is more consistent with reality in most adsorption processes, suggesting that the main rate-limiting steps in these adsorption processes are more likely to be controlled by chemisorption. Furthermore, intraparticle diffusion was not the primary rate-limiting factor in any of the adsorption processes tested.

Claims

1. A method for preparing an RS-HAP composite material, characterized in that, Includes the following steps: S1. Take an aqueous solution of CaCl2 with a concentration of 0.05~0.2mol / L, and denote it as the first solution; S2. Sodium risedronate and diammonium hydrogen phosphate are mixed in a ratio of 0.0381~0.2721 g: 1.0564~1.2875 g to obtain a mixed solid; then the mixed solid is added to deionized water in a ratio of 1~2 g: 100 mL, and this is referred to as the second solution. S3. The first solution is kept at a constant temperature of 30~50℃ with constant temperature stirring. While stirring, an equal volume of the second solution is added dropwise to the first solution. During the dropwise addition, the pH value is maintained at 8.0~10.

0. After the dropwise addition is completed, the solution is stirred for another 30 minutes and then microwaved to obtain a mixed solution. S4. After stirring, allow the mixture to settle naturally at room temperature and age for 20-30 hours; then perform solid-liquid separation to obtain a solid product. Clean, dry, grind, and sieve the solid product to obtain the RS-HAP composite material.

2. The method for preparing an RS-HAP composite material as described in claim 1, characterized in that, In S2, sodium risedronate and diammonium hydrogen phosphate were mixed in a ratio of 0.0763g:1.2545g to obtain a mixed solid.

3. The method for preparing an RS-HAP composite material as described in claim 1, characterized in that, In S2, sodium risedronate and diammonium hydrogen phosphate are mixed in a ratio of 0.1526g:1.1885g to obtain a mixed solid.

4. The method for preparing an RS-HAP composite material as described in claim 1, characterized in that, In S3, the microwave processing time is 8~12 minutes; the microwave processing power is 600~800W.

5. The method for preparing an RS-HAP composite material as described in claim 1, characterized in that, In S3, the dropping rate is 3 drops / s, and the stirring speed is 200~400 rpm.

6. The method for preparing an RS-HAP composite material as described in claim 1, characterized in that, In S3, the pH value is maintained by adjusting the diluted ammonia or hydrochloric acid.

7. The method for preparing an RS-HAP composite material as described in claim 1, characterized in that, In S4, the cleaning process involves sequentially washing with deionized water and an organic solvent; the washing is performed three times with water and three times with the organic solvent; the organic solvent is anhydrous ethanol or methanol.

8. The method for preparing an RS-HAP composite material as described in claim 1, characterized in that, In S4, the drying temperature is 50~80℃ and the drying time is 12~36h.

9. The application of the RS-HAP composite material as described in claim 1, characterized in that, The RS-HAP composite material is used to adsorb heavy metal ions in water.

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