Nanometer zero-valent iron-based adsorbing material as well as preparation method and application thereof
By preparing nano zero-valent iron-based adsorption materials, the problems of small adsorption capacity and poor selectivity of rare earth adsorption materials in the prior art are solved, and efficient enrichment and environmentally friendly recovery of low-concentration rare earth ions are achieved.
Patent Information
- Application Number
- CN202510523474.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-24
- Publication Date
- 2025-08-15
AI Technical Summary
The existing rare earth adsorption materials have shortcomings in adsorption capacity, selectivity and recycling efficiency, especially in low-concentration rare earth solutions, and there is a risk of secondary pollution.
Nanovalent iron materials were prepared by liquid phase reduction method, and phosphinic acid compounds were synthesized through Mannich reaction, and silane coupling agent was used to couple them with nanovalent iron materials to form nanovalent iron-based adsorption materials, enhancing their adsorption capacity and selectivity.
It achieves efficient adsorption of rare earth ions, with large adsorption capacity, good selectivity, strong anti-interference ability, and easy recycling of materials, reducing the risk of environmental pollution.
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Abstract
Description
Technical Field
[0001] The present invention relates to an adsorption material, in particular to a nanometer zero-valent iron-based adsorption material, a preparation method of the nanometer zero-valent iron-based adsorption material, and an application of the nanometer zero-valent iron-based adsorption material in adsorbing rare earth ions in aqueous solution, belonging to the field of rare earth recovery technology. Background Art
[0002] Rare earth elements are known as "industrial vitamins" because they are used in small quantities but have significant effects, significantly improving product performance and structure. They are widely used in industries such as permanent magnets, hydrogen storage, military, petrochemicals, smelting, and machinery. However, due to current over-exploitation, rare earth metals are facing an impending shortage. Against this backdrop, the enrichment and recovery of rare earth elements are becoming increasingly important.
[0003] Low concentrations of rare earth elements are present in environments such as rare earth mining wastewater and seawater. Recycling these elements would alleviate rare earth shortages to a certain extent. The most effective recovery method for low-concentration rare earth elements is adsorption using rare earth materials. Common rare earth adsorption materials include mineral-based materials (such as clay minerals like kaolinite and montmorillonite, and their modified materials), carbon-based materials (such as porous biochar, carbon nanotubes, and graphene oxide), metal-organic framework-based materials, and polymer-based materials (such as hydrogels). Mineral-based rare earth materials have the disadvantages of low adsorption capacity, easy aggregation, and difficulty in recovery. Single carbon-based adsorption materials have limited adsorption capacity, a complex modification process, and the risk of secondary contamination. Metal-organic framework-based adsorption materials are prone to metal site leakage. Therefore, the development of rare earth adsorption materials with high adsorption capacity, good selectivity, and easy removal, suitable for low-concentration rare earth elements, is urgently needed. Summary of the Invention
[0004] In view of the defects of the existing technology, the first purpose of the present invention is to provide a nano zero-valent iron-based adsorption material, which has the characteristics of large adsorption capacity, high adsorption activity, and good adsorption selectivity for rare earth ions and can be used as a rare earth ion adsorption material.
[0005] The second object of the present invention is to provide a method for preparing a nanometer zero-valent iron-based adsorption material, which is simple to operate, low in cost, mild in conditions, and is conducive to expanding production.
[0006] The third object of the present invention is to provide an application of a nano zero-valent iron-based adsorption material, which is used to adsorb rare earth ions in aqueous solutions. It exhibits the characteristics of fast adsorption rate, large adsorption capacity, good selectivity, and strong anti-interference ability. It can also achieve efficient enrichment of low-concentration rare earth ions and has application prospects in the enrichment of low-concentration rare earth ions in rare earth mining wastewater and seawater.
[0007] In order to achieve the above technical objectives, the present invention provides a method for preparing a nanometer zero-valent iron-based adsorption material, which comprises the following steps:
[0008] S1: Using iron salt as raw material, nano-zero-valent iron material was prepared by liquid phase reduction method;
[0009] S2: synthesizing a phosphonous acid compound by reacting phosphorous acid with an alkyl primary amine and formaldehyde through a Mannich reaction;
[0010] S3: The nano zero-valent iron material and the phosphinate compound are coupled by a silane coupling agent to obtain;
[0011] The molecular structural formula of the alkyl primary amine is as follows:
[0012] ;
[0013] The molecular structural formula of the phosphite compound is as follows:
[0014] ;
[0015] Among them, R is C5~C 18 Alkyl. C5~C 18 The alkyl group of R can be a straight chain alkyl group or a branched chain alkyl group or a cycloalkyl group. For example, hexyl, cyclohexyl, dodecyl, octadecyl, etc. R is further preferably C 12 ~C 18 of alkyl.
[0016] The Mannich reaction route involved in the present invention is as follows:
[0017] .
[0018] The technical solution of the present invention can obtain nano-zero-valent iron particles with uniform particle size and good dispersion through a liquid-phase reduction method. These particles have a higher specific surface area and more adsorption active sites, giving them high adsorption capacity and adsorption activity. Furthermore, the surface of the nano-zero-valent iron particles is modified with a phosphite compound. The phosphonic acid groups of the phosphite compound can improve the adsorption selectivity for rare earth ions and enhance its resistance to interference from impurity metal ions. The phosphite compound also has a long-chain alkyl group. After surface modification of the nano-zero-valent iron particles, the phosphite compound can alleviate the oxidation problem of the nano-zero-valent iron and extend the service life of the material. Furthermore, surface modification of the nano-zero-valent iron particles with the phosphite compound creates a more dispersed spatial structure, which reduces nanoparticle agglomeration, thereby increasing the contact area with rare earth ions and improving the adsorption capacity.
[0019] As a preferred method, the liquid-phase reduction method for preparing nano-zero-valent iron material involves mixing an iron salt solution with an excess NaBH4 solution, reacting at 25-40°C and a stirring rate of 200-800 rpm for 6-12 hours, followed by solid-liquid separation and freeze-drying. The liquid-phase reduction method is easy to control, and by controlling reduction conditions such as temperature and stirring rate, nano-zero-valent iron material with uniform particle size can be easily obtained.
[0020] As a preferred embodiment, the concentration of the iron salt solution is 0.1-0.5 mol / L. As a preferred embodiment, the concentration of the NaBH4 solution is 0.5-1.0 mol / L. The concentration of the iron salt solution should not be too high, as a high concentration can easily cause the generated nano-zero-valent iron particles to agglomerate. Lower iron salt concentrations are more favorable for the formation of nano-zero-valent iron particles, but lower concentrations reduce the efficiency of synthesizing nano-zero-valent iron. As a preferred embodiment, the iron salt solution and the NaBH4 solution are mixed at a molar ratio of NaBH4 to iron salt greater than 3:1. A moderate excess of NaBH4 facilitates the complete conversion of the iron salt while preventing oxidation of the generated nano-zero-valent iron. The concentration of the iron salt solution is more preferably 0.4-0.5 mol / L. The concentration of the NaBH4 solution is more preferably 0.64-0.8 mol / L. The iron salt solution and the NaBH4 solution are mixed at a molar ratio of NaBH4 to iron salt of 4-5:1.
[0021] As a more preferred solution, the iron salt contained in the iron salt solution is a water-soluble iron salt, such as ferric sulfate, ferric chloride, ferrous chloride, ferric nitrate, etc. The most preferred iron salt is ferric chloride.
[0022] As a more preferred solution, during the process of preparing the nano zero-valent iron material by the liquid phase reduction method, the temperature is further preferably 25-30° C., and the stirring rate is further preferably 600-800 rpm.
[0023] As a preferred embodiment, during the liquid-phase reduction process for preparing the nano-zero-valent iron material, the freeze-drying conditions are: vacuum drying at a temperature of -52 to -60°C for 10 to 12 hours. The freeze-drying conditions are further preferably: vacuum drying at a temperature of -58 to -60°C for 11 to 12 hours.
[0024] As a preferred embodiment, the Mannich reaction process for synthesizing a phosphite compound comprises dissolving phosphorous acid and an alkyl primary amine in a hydrochloric acid solution, heating the solution to 115-125°C, then adding formaldehyde solution dropwise for reaction. After the formaldehyde solution has been added, the reaction is refluxed for 1.5-2.5 hours to obtain the phosphite compound. The Mannich reaction is a well-known reaction type, and the present invention primarily utilizes an alkyl primary amine, phosphorous acid, and formaldehyde to form the phosphite compound through the Mannich reaction. As a more preferred embodiment, the molar ratio of phosphorous acid to the alkyl primary amine is 2-3.5:1; the molar ratio of phosphorous acid to the alkyl primary amine is more preferably 2-2.5:1. As a more preferred embodiment, the concentration of the hydrochloric acid solution is 3-8 mol / L; the concentration of the hydrochloric acid solution is more preferably 6-8 mol / L. As a more preferred embodiment, the molar ratio of formaldehyde to the alkyl primary amine is 2.0-2.5:1.
[0025] As a preferred embodiment, the nano-zero-valent iron material and the phosphite compound are coupled via a silane coupling agent. The nano-zero-valent iron material is dispersed in an acetic acid solution, followed by the addition of the silane coupling agent and the phosphite compound, and stirring for 2-8 hours. The phosphite compound is then chemically bonded to the surface of the nano-zero-valent iron particles using the coupling action of the silane coupling agent.
[0026] As a preferred solution, the concentration of the acetic acid solution is 0.1 to 1 mol / L, and more preferably 0.5 to 1 mol / L. Selecting a lower concentration of acetic acid can activate the nano-zero-valent iron, facilitating subsequent surface modification with the phosphinate compound.
[0027] As a preferred embodiment, the amount of the silane coupling agent used is 0.3% to 5% of the molar weight of the nano-zero-valent iron material. The amount of the silane coupling agent used is further preferably 3% to 5% of the molar weight of the nano-zero-valent iron material. The preferred silane coupling agent is KH-550.
[0028] As a preferred embodiment, the molar ratio of the phosphite compound to the nano-zero-valent iron is 1 to 5:1. As the molar ratio of the phosphite compound to the nano-zero-valent iron increases, the adsorption effect of the nano-zero-valent iron-based adsorption material on rare earth ions increases and tends to stabilize. Therefore, the molar ratio of the phosphite compound to the nano-zero-valent iron is further preferably 2 to 4:1.
[0029] In steps S1 and S3 of the present invention, the reactions are carried out under anaerobic conditions, mainly to prevent oxidation of nano-zero-valent iron, and excessive nitrogen is introduced into various solutions before use to remove oxygen.
[0030] The present invention also provides a nano-zero-valent iron-based adsorption material obtained by the aforementioned preparation method. The nano-zero-valent iron-based adsorption material of the present invention comprises nano-zero-valent iron particles as its active ingredient. Due to their large specific surface area and high adsorption activity, they exhibit a high adsorption capacity for rare earth ions, reaching hundreds of milligrams per gram. Their high adsorption activity and strong adsorption capacity enable efficient adsorption of low-concentration rare earth ions. The nano-zero-valent iron particles are further modified with a phosphite compound, which improves the adsorption selectivity of the nano-zero-valent iron for rare earth ions and enhances its anti-interference ability.
[0031] The nano-zero-valent iron-based adsorption material of the present invention has high adsorption capacity and adsorption selectivity for rare earth ions: the nano-zero-valent iron has a huge specific surface area and directly physically adsorbs rare earth ions. At the same time, the nano-zero-valent iron has high reactivity and can reduce and deposit free rare earth ions, showing strong chemical adsorption; in addition, the phosphite compound coupled to the surface of the nano-zero-valent iron couples with the rare earth ions to achieve highly selective adsorption of rare earth ions.
[0032] The present invention also provides an application of a nanometer zero-valent iron-based adsorption material for adsorbing rare earth ions in an aqueous solution.
[0033] As a preferred solution, the aqueous solution contains rare earth ions and Ca 2+ Mg 2+ 、Na + , K + At least one impurity metal ion in the nanometer zero-valent iron-based adsorption material 2+ Mg 2+ 、Na + , K + Rare earth ions have selective adsorption in complex solution systems where metal ions and rare earth ions coexist.
[0034] As a preferred embodiment, the rare earth ion concentration in the aqueous solution is less than 200 mg / L. In a further preferred embodiment, the rare earth ion concentration in the aqueous solution is ≤100 mg / L. The nanometer zero-valent iron-based adsorption material of the present invention is suitable for adsorption and enrichment of low-concentration rare earth ions.
[0035] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:
[0036] 1) The nano-zero-valent iron-based adsorption material of this invention uses nano-zero-valent iron as its matrix material. It possesses a high specific surface area, high reactivity, strong adsorption capacity, and large adsorption capacity, strongly adsorbing rare earth elements from low-concentration rare earth solutions. Furthermore, the large number of phosphonic acid groups coupled to the nano-zero-valent iron gives it excellent selectivity for rare earth elements, enabling targeted extraction of rare earth elements from solutions while absorbing little or no other impurities.
[0037] 2) The nano-zero-valent iron-based adsorption material of this invention, modified with a phosphite compound, forms a more dispersed spatial structure. This spatial structure reduces agglomeration, thereby increasing the contact area with the rare earth element and improving adsorption capacity. Furthermore, the phosphite-modified nano-zero-valent iron alleviates oxidation issues, extending the material's service life.
[0038] 3) The nano-zero-valent iron-based adsorption material of the present invention has good reusability, which reduces the cost of the material. Compared with traditional rare earth adsorption materials, it is more environmentally friendly and can avoid environmental pollution caused by material depolymerization. DETAILED DESCRIPTION
[0039] In order to better understand the features and usage scenarios of the products of the present invention, the present invention is further explained below in conjunction with specific embodiments, but the following embodiments are only preferred examples of the present invention, not all. Based on the embodiments in the implementation plan, those skilled in the art can obtain other embodiments without any creative work. It is worth noting that these embodiments are all within the scope of protection of the claims of the present invention.
[0040] The synthesis of the phosphite compound of the present invention is based on the literature (“Recovery of rare earth elements from mining wastewater with aminomethylphosphonic acid functionalized 3D-printed filters”, Virtanen JE, et al. Separation and Purification Technology, 2025, 353(PC): 128599-128599).
[0041] Example 1
[0042] A method for preparing a nanometer zero-valent iron-based rare earth adsorption material comprises the following steps:
[0043] (1) 16.22 g of anhydrous ferric chloride and 18.15 g of NaBH4 were placed in 200 mL and 600 mL of deionized water, respectively, to prepare solutions. Nitrogen was introduced for 10 min, and then the two solutions were poured into a 2 L three-necked flask at the same time. The mixture was stirred in a water bath at 25 °C for 8 h. Nitrogen was also introduced throughout the reaction process.
[0044] (2) After stirring, the solid product was quickly filtered, washed three times with anhydrous ethanol, and then freeze-dried. It was vacuum-dried at -58~-60℃ for 12h to obtain the nano zero-valent iron matrix material.
[0045] (3) Dissolve 16.40 g of phosphorous acid and 18.53 g of dodecylamine in 6 mol / L hydrochloric acid to obtain a mixture 1.
[0046] (4) Mixture 1 was poured into a 1 L three-necked flask, heated to 120 °C in an oil bath, and 15.21 mL of formaldehyde solution was added dropwise within 1 h. The mixture was refluxed for 2 h, and the white precipitate was collected and washed with ethanol three times to obtain a phosphite compound.
[0047] (5) 200 mL of acetic acid solution was passed through an excess of nitrogen and then poured into a 500 mL three-necked flask. The nano-zero-valent iron matrix material prepared in (2) and the phosphite compound prepared in (4) were added. Subsequently, KH-550 (5% by weight of the nano-zero-valent iron matrix material) was added and stirred for 3 h. Nitrogen was also passed through the entire reaction process.
[0048] Example 2
[0049] Different from Example 1, 24.60 g of phosphorous acid and 27.80 g of dodecylamine were added in step (3), and 22.82 mL of formaldehyde solution was added dropwise in step (4).
[0050] Example 3
[0051] Different from Example 1, 32.80 g of phosphorous acid and 37.07 g of dodecylamine were added in step (3), and 30.42 mL of formaldehyde solution was added dropwise in step (4).
[0052] Example 4
[0053] The difference from Example 1 is that 41.00 g of phosphorous acid and 46.33 g of dodecylamine are added in step (3), and 38.03 mL of formaldehyde solution is added dropwise in step (4).
[0054] Example 5
[0055] Different from Example 1, 49.20 g of phosphorous acid and 55.60 g of dodecylamine were added in step (3), and 45.64 mL of formaldehyde solution was added dropwise in step (4).
[0056] Comparative Example 1
[0057] Different from Example 1, no phosphorous acid compound is added to modify the nano zero-valent iron.
[0058] Examples 1 to 5 investigate the effects of varying the molar ratio of the phosphorous acid compound (whose molar amount is the same as that of the amine) to nZVI on the material properties.
[0059] Comparative Example 1 investigates the adsorption effect of nano-zero-valent iron of unmodified phosphite compound on rare earth.
[0060]
[0061] Application Examples 1 to 5
[0062] The adsorption materials of Examples 1 to 5 were used to adsorb rare earth elements respectively. The amount of adsorption material used was 100 mg, the pH was 6, the adsorption temperature was 25° C., and the adsorption time was 60 min. The adsorption amount of each rare earth element is shown in Table 2:
[0063]
[0064] In Table 2, the initial concentration of rare earth ions was 100 mg / L and the volume was 200 mL.
[0065] It can be seen from Table 2 that the adsorption materials of Examples 1 to 5 have a significant effect on La 3+ 、Nd 3+ 、Gd 3+ and Y 3+ All of them have good adsorption effects. The adsorption amount of rare earth elements by the adsorption materials of Examples 1 to 5 is large. As the amount of phosphite compound increases, the adsorption effect gradually increases. When the molar ratio of phosphite compound to nZVI approaches 3:1, the adsorption effect increases slowly. In summary, the adsorption materials of Examples 1 to 5 can achieve large-scale adsorption of rare earth elements, and the more the amount of phosphite compound is used, the better the adsorption effect. The best effect is achieved when the molar ratio of phosphite compound to nZVI is 3:1, and it is not meaningful to continue to increase the amount of phosphite compound.
[0066] The adsorbed material was recycled and the newly configured rare earth solution was subjected to secondary adsorption with the same operating conditions as above, and the adsorption amount could reach more than 90%; after three adsorptions, the adsorption amount could reach more than 85%, indicating that this material has good reusability.
[0067] Application Example 6
[0068] Using the adsorption materials of Examples 1 to 5 in Ca 2+ Mg 2+ 、Na + , K+ The effects of different interference conditions on La 3+ Adsorption was performed at pH = 6, adsorption temperature was 25 ° C, adsorption time was 60 min, and impurity ion concentration was 10 mM. Under the interference of the above four ions, the adsorption materials of Examples 1 to 5 had a significant effect on La 3+ The adsorption effect of Examples 1 to 5 was minimally affected, and the decrease in adsorption rate was less than 1%, which proved that the adsorption materials of Examples 1 to 5 had strong anti-interference effect, good adsorption effect and excellent performance.
[0069] Application Example 7
[0070] 100 mg of the adsorption material of Comparative Example 1 was weighed to adsorb rare earth elements at a pH of 6, an adsorption temperature of 25° C., and an adsorption time of 60 min. The results are shown in Table 3:
[0071]
[0072] In Table 3, the initial concentration of rare earth ions was 100 mg / L, and the volume was 200 mL.
[0073] It can be seen from Table 3 that the adsorption material of Comparative Example 1 has a significant effect on La 3+ 、Nd 3+ 、Gd 3+ and Y 3+ The adsorption effect of the nanometer zero-valent iron material without phosphorous acid modification is poor, and the rare earth concentration does not change significantly after a period of adsorption. In summary, the adsorption effect of the nanometer zero-valent iron material on rare earth is poor, and it cannot achieve large-scale adsorption of rare earth.
[0074] Finally, it should be noted that the above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Ordinary technicians in this field can make simple modifications or equivalent replacements to the technical solutions of the present invention without departing from the essence and scope of the technology of the present invention.
Claims
1. A method for preparing a nanometer zero-valent iron-based adsorption material, characterized by: The following steps are involved: S1: Using iron salt as raw material, nano-zero-valent iron material was prepared by liquid phase reduction method; S2: synthesizing a phosphonous acid compound by reacting phosphorous acid with an alkyl primary amine and formaldehyde through a Mannich reaction; S3: The nano zero-valent iron material and the phosphinate compound are coupled by a silane coupling agent to obtain; The molecular structural formula of the alkyl primary amine is as follows: ； The molecular structural formula of the phosphite compound is as follows: ； Among them, R is C5~C 18 of alkyl.
2. The method for preparing a nanometer zero-valent iron-based adsorption material according to claim 1, characterized in that: The process of preparing nano zero-valent iron material by the liquid phase reduction method is as follows: mixing an iron salt solution with an excess NaBH4 solution, reacting at a temperature of 25-40°C and a stirring rate of 200-800 rpm for 6-12 hours, separating the solid and the liquid, and freeze-drying.
3. The method for preparing a nanometer zero-valent iron-based adsorption material according to claim 2, characterized in that: The concentration of the iron salt solution is 0.1-0.5 mol / L; The concentration of the NaBH4 solution is 0.1~1.0mol / L; The iron salt solution and the NaBH4 solution are mixed in a ratio where the molar ratio of NaBH4 to iron salt is greater than 3:
1.
4. The method for preparing a nanometer zero-valent iron-based adsorption material according to claim 1, characterized in that: The Mannich reaction process for synthesizing the phosphite compound is as follows: phosphorous acid and an alkyl primary amine are dissolved in a hydrochloric acid solution, heated to 115-125° C., and then a formaldehyde solution is added dropwise for reaction. After the formaldehyde solution is added dropwise, the reaction is refluxed for 1.5-2.5 hours to obtain the phosphite compound.
5. The method for preparing a nanometer zero-valent iron-based adsorption material according to claim 4, characterized in that: The molar ratio of the phosphorous acid to the alkyl primary amine is 2 to 3.5:1; The molar ratio of the formaldehyde to the alkyl primary amine is 2 to 2.5:1; The concentration of the hydrochloric acid solution is 3-8 mol / L.
6. The method for preparing a nanometer zero-valent iron-based adsorption material according to claim 1, characterized in that: The process of coupling the nano zero-valent iron material and the phosphinate compound through a silane coupling agent is as follows: dispersing the nano zero-valent iron material into an acetic acid solution, then adding the silane coupling agent and the phosphinate compound, and stirring for 2 to 8 hours.
7. The method for preparing a nanometer zero-valent iron-based adsorption material according to claim 6, characterized in that: The concentration of the acetic acid solution is 0.1~1 mol / L; The amount of the silane coupling agent is 0.3% to 5% of the mass of the nano zero-valent iron material; The molar ratio of the phosphite compound to the nano-zero-valent iron is 1-5:
1.
8. A nanometer zero-valent iron-based adsorption material, characterized by: Obtained by the preparation method according to any one of claims 1 to 7.
9. The use of a nano zero-valent iron-based adsorption material according to claim 8, characterized in that: Used to adsorb rare earth ions in aqueous solutions.
10. The use of a nano zero-valent iron-based adsorption material according to claim 9, characterized in that: The aqueous solution contains rare earth ions and Ca 2+ Mg 2+ 、Na + , K + At least one impurity metal ion; The rare earth ion concentration in the aqueous solution is lower than 200 mg / L.