Iron-doped hydroxyapatite composite material as well as preparation method and application thereof

Abstract

The invention discloses an iron-doped hydroxyapatite composite material as well as a preparation method and application thereof, and belongs to the technical field of environmental science and engineering. The preparation method of the iron-doped hydroxyapatite composite material comprises the following steps: firstly dispersing hydroxyapatite in an alkali solution, then adding soluble iron salt into a dispersion system, generating brownish red precipitate, and then heating to remove moisture, so as to obtain the iron-doped hydroxyapatite composite material. The iron-doped hydroxyapatite composite material is rapidly synthesized through a coprecipitation method, Cd, As and Pb are synchronously fixed through hydroxyapatite, meanwhile, leached As is oxidized and adsorbed through minerals formed by doped iron elements, insoluble iron-arsenic mineral precipitates are formed, the mobility and bioavailability of arsenic are reduced, and synchronous repair of arsenic-cadmium-lead co-pollution is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental science and engineering, and particularly relates to an iron-doped hydroxyapatite composite material, a preparation method thereof, and an application thereof. Background Art

[0002] Soil heavy metal pollution is characterized by concealment, accumulation, persistence, irreversibility, and difficulty in treatment. Cd, As, and Pb are significantly toxic to most organisms, and the International Agency for Research on Cancer classifies all three as Group 1 carcinogens. Composite pollution of Cd, As, and Pb is commonly found in the soil of non-ferrous metal mining areas, and the combined toxicity of Cd, As, and Pb may be greater than that of single or other heavy metals, increasing their ecological risk. Therefore, the treatment of soil contaminated with Cd, As, and Pb in combination is urgently needed.

[0003] Phosphorus-containing materials are one of the most commonly used fixatives in the stabilization and remediation of heavy metals. Phosphorus-containing materials can be divided into soluble phosphates (such as phosphate fertilizers and calcium hydrogen phosphate) and insoluble phosphates (such as hydroxyapatite and phosphate rock powder). It has been confirmed by many research scholars that they have good adsorption properties and stabilization effects on cationic metals in soil or solution media. However, existing studies have also shown that the application of phosphorus-containing materials may promote a strong competitive relationship between arsenic, antimony, selenium and other homologous elements and phosphates at adsorption sites in the soil, thereby promoting their leaching and causing secondary pollution of toxic elements such as arsenic, which limits the application of phosphorus-containing materials in the treatment of soil contaminated with Cd, As, and Pb in combination. Summary of the Invention

[0004] To solve the above problems, the present invention provides an iron-doped hydroxyapatite composite material, a preparation method thereof, and an application thereof. By a co-precipitation method, an iron-doped hydroxyapatite composite material is rapidly synthesized. While simultaneously fixing Cd, As, and Pb by hydroxyapatite, the minerals formed by the doped iron element oxidize and adsorb the leached As to form insoluble iron-arsenic mineral precipitates, reducing the mobility and bioavailability of arsenic, and achieving synchronous remediation of co-pollution of arsenic, cadmium, and lead.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention: provides a preparation method of an iron-doped hydroxyapatite composite material, comprising the following steps:

[0007] First, disperse hydroxyapatite in an alkaline solution, and then add a soluble iron salt to the dispersion system. After generating a brownish-red precipitate, heat to remove moisture to obtain the iron-doped hydroxyapatite composite material.

[0008] Preferably, the alkaline solution is a 5 mol / L KOH solution.

[0009] Preferably, the dosage ratio of the hydroxyapatite to OH - in the alkali solution is 1.2 - 1.7 g: 0.5 mol.

[0010] Preferably, the dosage ratio of Fe 3+ in the soluble iron salt to the hydroxyapatite is 89.5 mmol: 1.2 - 1.7 g.

[0011] Preferably, the temperature for heating to remove moisture is 70 - 80 °C, and the time is 60 - 65 h.

[0012] Preferably, after heating to remove moisture, it further includes the steps of washing, drying, and pulverizing.

[0013] More preferably, the washing liquid used for washing is an equal - volume mixture of ethanol and water; the drying temperature is 60 °C; the pulverizing is to pulverize the sample to a particle size not exceeding 0.15 mm.

[0014] The second technical solution of the present invention: Provide an iron - doped hydroxyapatite composite material prepared by the preparation method of the above - mentioned iron - doped hydroxyapatite composite material.

[0015] The third technical solution of the present invention: Provide an application of the above - mentioned iron - doped hydroxyapatite composite material in the synchronous remediation of arsenic - cadmium - lead co - contaminated soil.

[0016] The beneficial technical effects of the present invention are as follows:

[0017] Cadmium and lead often exist in the form of cations in water and soil, while arsenic exists in the form of opposite oxygen - containing anions, and its chemical behavior is completely opposite to the former two. It is very difficult to simultaneously reduce the activity of these three heavy metals or simultaneously stabilize these three heavy metals only by changing the physical and chemical properties of water bodies and soils to achieve the remediation of arsenic - cadmium - lead co - pollution. The iron - doped hydroxyapatite composite material prepared by the coprecipitation method in the present invention overcomes the disadvantages of conventional materials in the practical application of arsenic - cadmium - lead co - pollution remediation, such as difficulty in achieving synchronous remediation and high detoxification difficulty, and realizes the synchronous remediation of arsenic - cadmium - lead co - pollution in water and soil. The preparation method provided by the present invention has a short time - consuming, simple operation, low cost, and is of great significance for the remediation of multi - metal composite pollution. Description of the Drawings

[0018] Figure 1 For the pseudo - first - order and pseudo - second - order adsorption kinetic fitting models of FH - 3 in Test Example 2, where (a) is the adsorption kinetic fitting model of As(III) on FH - 3, (b) is the adsorption kinetic fitting model of Cd(II) on FH - 3, and (c) is the adsorption kinetic fitting model of Pb(II) on FH - 3.

[0019] Figure 2For the dynamic changes in the available contents and reduction rates of As, Cd, and Pb under different treatment conditions in Test Example 3, where (a) is the available content of As, (b) is the reduction rate of available As, (c) is the available content of Cd, (d) is the reduction rate of available Cd, (e) is the available content of Pb, and (f) is the reduction rate of available Pb. Detailed implementation manners

[0020] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention. It should be understood that the terms used in the present invention are only for describing specific implementation manners and are not used to limit the present invention.

[0021] It should be noted that the operations not described in detail in the present invention are all conventional operation means in the art and are not the focus of the present invention.

[0022] In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0023] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention.

[0024] Regarding the terms "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0025] Example 1

[0026] Preparation of iron-doped hydroxyapatite composite material:

[0027] Disperse 1.67 g of hydroxyapatite (HAP) in 5 mol / L KOH solution (100 mL), and stir it with a magnetic stirrer at 60 °C for 1 h. Then add 89.5 mL of 1 mol / L Fe(NO3)3·9H2O solution to the above mixture. After generating a brownish-red precipitate, place it in an oven at 70 °C for 60 h. After drying, rinse the sample with an equal-volume mixture of water and ethanol multiple times, centrifuge it, and dry it in an oven at 60 °C. Grind it with an agate mortar and pass it through a 0.15 mm sieve to obtain the iron-doped hydroxyapatite composite material, denoted as FH-3.

[0028] Comparative Example 1

[0029] Compared with Example 1, the difference is only that the raw material hydroxyapatite is omitted, and other operations are the same. The pure iron mineral thus prepared is denoted as IM.

[0030] Test Example 1

[0031] Adsorption study of As(III), Cd(II) and Pb(II) composite solution system:

[0032] Using FH-3 prepared in Example 1, IM prepared in Comparative Example 1 and the raw material hydroxyapatite (HAP, ground through a 0.15 mm sieve) as adsorbents, respectively add them into a mixed solution of As(III), Cd(II) and Pb(II) with a concentration of 50 mg / L each, and the material addition amount is 1 g / L. The solution pH is adjusted to 5 using a 0.01 M HNO3 solution or NaOH solution. Using 0.01 mol / L NaNO3 solution as the background electrolyte solution, the mixture is shaken in a constant temperature shaker at room temperature of 25 °C and a rotation speed of 180 rpm for 24 h. After the reaction is completed, the suspension is centrifuged at 4000 rpm for 10 min using a centrifuge to obtain the supernatant. Then it is filtered through a 0.45 μm cellulose acetate filter membrane, and the residual concentrations of arsenic, cadmium and lead in the filtrate are measured by inductively coupled plasma-optical emission spectrometry (ICP-OES). All adsorption treatments are repeated 3 times to study the treatment effects of different materials. The adsorption rates (the percentage value of the reduction of heavy metals in the solution) of different materials for 50 mg / L As(III), Cd(II) and Pb(II) are shown in Table 1.

[0033] Table 1 Adsorption rates of different materials for 50 mg / L As(III), Cd(II) and Pb(II)

[0034] As(Ⅲ) Cd(Ⅱ) Pb(Ⅱ) IM 84.58％ 63.94％ 90.23％ HAP 0.00％ 73.14％ 95.56％ FH-3 89.01％ 96.92％ 99.36％

[0035] It can be seen from the data in Table 1 that the iron-doped hydroxyapatite composite material FH-3 overcomes the disadvantage that hydroxyapatite cannot adsorb As(III), and at the same time, compared with the iron mineral IM, the adsorption capacity for the three heavy metals is also significantly improved, and it can effectively adsorb As(III), Cd(II) and Pb(II) synchronously.

[0036] Test Example 2

[0037] Study on the adsorption kinetics of FH-3 for arsenic, cadmium and lead in a single aqueous solution system:

[0038] Method: Add 0.02 g of FH-3 into a 50 mL centrifuge tube, and then add 20 mL of solutions containing 50 mg / L of As(III), Cd(II), and Pb(II) (single pollution system) respectively. Adjust the pH of the solution to 5 using 0.01 M HNO3 solution or NaOH solution. Use 0.01 mol / L NaNO3 solution as the background electrolyte solution, and shake the mixture in a constant temperature shaker at 25 °C and 180 rpm for 24 h. After the reaction is completed, centrifuge the suspension at 4000 rpm for 10 min to obtain the supernatant. Then filter it through a 0.45 μm cellulose acetate filter membrane, and measure the residual concentrations of arsenic, cadmium, and lead in the filtrate by inductively coupled plasma-optical emission spectrometry (ICP-OES). All adsorption treatments are repeated 3 times.

[0039] The pseudo-first-order and pseudo-second-order models were used to fit the adsorption data of FH-3. The results of the pseudo-first-order and pseudo-second-order kinetic models are as Figure 1 and Table 2 show that Figure 1 Among them, (a) is the adsorption kinetic fitting model of As(III) on FH-3, (b) is the adsorption kinetic fitting model of Cd(II) on FH-3, and (c) is the adsorption kinetic fitting model of Pb(II) on FH-3.

[0040] Table 2 Fitting parameters of kinetic models for the adsorption of As(III), Cd(II), and Pb(II) by FH-3

[0041]

[0042] Figure 1 And the results in Table 2 show that the adsorption kinetics of As(III), Cd(II), and Pb(II) on FH-3 are all applicable to the description by the pseudo-second-order kinetic model. This indicates that FH-3 has the ability to adsorb As(III), Cd(II), and Pb(II), and the adsorption process of these three heavy metals is mainly chemical adsorption rather than physical adsorption.

[0043] Test Example 3

[0044] Field remediation application of FH-3, HAP, and IM in contaminated soil from a certain arsenic factory in Guangdong:

[0045] Method: Weigh 200 g of contaminated soil from a certain arsenic factory in Guangdong after pretreatment (ground through a 1 mm sieve) and place it in a polyethylene plastic basin. Add 80 mL of water to make the water content reach 70% of the field capacity. Select HAP, IM, and FH-3 in Test Example 1 as passivators for soil culture experiments. Considering the passivation effect and usage cost of the materials in the previous experiments comprehensively, the application rates are set at 10 g / kg and 30 g / kg. A total of 5 treatments are set according to whether the materials are added and the material addition levels, namely blank control (CK), hydroxyapatite - 30 g / kg (HAP-30), iron mineral - 30 g / kg (IM-30), iron-doped hydroxyapatite - 10 g / kg (FH-3-10), and iron-doped hydroxyapatite - 30 g / kg (FH-3-30). Stir the weighed quantitative materials evenly with the site-contaminated soil and then load them into plastic basins. Set 2 blank groups for each soil treatment, and conduct three parallel tests for each treatment. Record the initial total mass of the culture pots, keep the soil in a loose, moist but non-significantly aggregated state, place it in an incubator at room temperature, and cover it with a porous nylon membrane to maintain gas circulation. Sampling is carried out on the 5th, 15th, 30th, 50th, 70th, and 90th days respectively. Each time, take 20 g of fresh soil samples, air-dry them and sieve them, and analyze the available concentrations of arsenic, cadmium, and lead. During the cultivation period, use the weighing method to always maintain 70% of the field capacity of the remaining soil every 2 days.

[0046] When measuring the available Cd and Pb contents in the soil, add 0.1 mol / L of CaCl2 under the condition of a soil-water ratio of 1:10 (w / v), and shake at a constant temperature of 25 °C on a shaking table at a speed of 180 rpm for 2 h to extract the available Cd and Pb; for the available As content in the soil, use 0.5 mol / L of NH4H2PO4 under the condition of a soil-water ratio of 1:30 (w / v), and shake at a constant temperature of 25 °C on a shaking table at a speed of 180 rpm for 16 h to extract the available As.

[0047] The dynamic changes in the available contents and reduction rates of As, Cd, and Pb under different treatment conditions are shown in Figure 2 , where (a) is the available content of As, (b) is the reduction rate of available As, (c) is the available content of Cd, (d) is the reduction rate of available Cd, (e) is the available content of Pb, and (f) is the reduction rate of available Pb.

[0048] It can be seen from Figure 2 that the available arsenic concentration in the blank control group CK increased significantly during the mid-term of remediation (5 - 50 days), with the highest increase of 31.45% compared to the initial value ( Figure 2-a). The concentration of available arsenic in the IM-30 group did not show an obvious decrease in the early stage, and then showed a downward trend from 15 to 30 days. The arsenic concentration in the HAP-30 group increased in the initial stage. Both iron-doped hydroxyapatite composites significantly reduced the available arsenic concentration in the initial stage and remained relatively stable over time in the later stage. The final reduction of FH-3-10 with a low addition amount was 31.14%. In the FH-3-30 group with a high addition amount, the available arsenic concentration decreased to 25.06 mg / kg at 90 days, with a reduction rate as high as 67.88%.

[0049] The concentration of available cadmium in the CK group changed little during the entire remediation period ( Figure 2 -c). The cadmium concentration in both the IM-30 group and the HAP-30 group decreased in the initial stage, and the HAP-30 group had a faster decrease rate and a larger reduction range. However, after 15 days, cadmium redissolved, and the available cadmium concentration increased significantly. Both the FH-3-10 group and the FH-3-30 group showed a fast solidification rate and long-term stability. Especially in the FH-3-30 group, the available cadmium concentration decreased to only 0.80 mg / kg at 90 days, with a reduction rate of 78.68%.

[0050] There was no obvious change trend in the available lead concentration in the CK group. After adding iron minerals, the IM-30 group had a certain fixation effect on lead, and the final concentration decreased to about 25.72 mg / kg. The trend of available lead in the HAP-30 group was similar to that of cadmium, and the concentration decreased rapidly in the initial stage. But in the later stage, cadmium redissolved and the concentration increased, which was not suitable for long-term solidification remediation. The available lead concentration in both the FH-3-10 group and the FH-3-30 group continued to decrease during the entire experiment, and finally decreased to 18.98 mg / kg and 13.13 mg / kg respectively, with a maximum reduction rate of 61.56%.

[0051] The above results indicate that the composite material FH-3 can effectively reduce the available concentrations of arsenic, cadmium, and lead and maintain stability within a 90-day cycle, and has the remediation effect of long-term effectiveness and stability for arsenic, cadmium, and lead multi-metal contaminated soil.

[0052] The embodiments described above are only used to describe the preferred mode of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention should fall within the protection scope determined by the claims of the present invention.

Claims

1. A preparation method of an iron-doped hydroxyapatite composite material, characterized in that, It includes the following steps: First, disperse hydroxyapatite in an alkali solution, then add a soluble iron salt to the dispersion system. After generating a brownish-red precipitate, remove the moisture by heating to obtain the iron-doped hydroxyapatite composite material.

2. The preparation method of the iron-doped hydroxyapatite composite material according to claim 1, characterized in that, The alkali solution is a 5 mol / L KOH solution.

3. The preparation method of the iron-doped hydroxyapatite composite material according to claim 1, characterized in that, The dosage ratio of the hydroxyapatite to OH in the alkali solution - is 1.2 - 1.7 g: 0.5 mol.

4. The preparation method of the iron-doped hydroxyapatite composite material according to claim 1, wherein, The Fe in the soluble iron salt 3+ has a dosage ratio to the hydroxyapatite of 89.5 mmol: 1.2 - 1.7 g.

5. The preparation method of the iron-doped hydroxyapatite composite material according to claim 1, characterized in that The temperature for removing moisture by heating is 70 - 80 °C, and the time is 60 - 65 h.

6. The preparation method of the iron-doped hydroxyapatite composite material according to claim 1, characterized in that, After removing moisture by heating, it further includes the steps of washing, drying, and pulverizing.

7. The preparation method of the iron-doped hydroxyapatite composite material according to claim 6, characterized in that, The washing liquid used for washing is an equal-volume mixture of ethanol and water; the drying temperature is 60 °C; the pulverizing is to pulverize the sample to a particle size not exceeding 0.15 mm.

8. An iron-doped hydroxyapatite composite material prepared by the preparation method of the iron-doped hydroxyapatite composite material according to any one of claims 1 to 7.

9. The application of the iron-doped hydroxyapatite composite material according to claim 8 in simultaneously repairing arsenic-cadmium-lead co-polluted soil.

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