Magnetic nano composite material for adsorbing noble metal ions as well as preparation method and application of magnetic nano composite material

Abstract

The invention discloses a magnetic nano composite material for adsorbing precious metal ions as well as a preparation method and application thereof, and belongs to the technical field of precious metal recovery. The magnetic nano composite material disclosed by the invention is composed of Fe, FeS, a carbon layer and porous carbon, the Fe, the FeS, the carbon layer and the porous carbon have nanoscale sizes and structures; the magnetic nano composite material has the following structure: embedded nanospheres are uniformly distributed in a network structure formed by porous carbon; the nanosphere has a core-shell structure, the core is Fe, the shell is FeS, and the nanosphere is wrapped with a carbon layer. The magnetic nano composite material can highly selectively adsorb more than 99% of Au (III), Ag (I) and Pd (II) from more than 20 kinds of metal ions within 10 min, and precious metal separation can be rapidly achieved in a mode of externally applying a magnetic field.

Description

Technical Field

[0001] This invention relates to the field of precious metal adsorption, enrichment, separation and recovery technology, specifically to a magnetic nanocomposite material for adsorbing precious metal ions, its preparation method and application. Background Technology

[0002] Precious metals such as gold (Au), silver (Ag), and palladium (Pd) are used in various fields, including catalysis, electronics, fuel cells, and medicine, due to their unique physical and chemical properties. Because precious metals are limited in supply, non-renewable, and have high economic value, efforts have been made to recover precious metal ions from nature or industrial waste. Currently, the main collection methods include extraction, precipitation, electroreduction, adsorption, and ion exchange. Among these, adsorption is considered the most economical and effective method for precious metal ion recovery due to its high efficiency, low energy consumption, and simple operation. Adsorption materials are a key factor in the adsorption method for precious metal recovery. Numerous materials, including porous organic polymers, metal-organic frameworks, graphene, and bio-derived materials, have been designed for the adsorption, enrichment, and separation of precious metal ions.

[0003] However, conventional adsorbents lack selectivity and suffer from slow adsorption rates and low efficiency. They cannot adsorb and enrich trace (ppb-level) noble metal ions from natural water bodies, nor can they overcome the interference of high-concentration competing ions (such as Cu(II), Ni(II), Zn(II), Pb(II), Ca(II), Al(III), etc.) in industrial wastewater on the adsorption of Au(III), Ag(I), and Pd(II). Furthermore, from a practical application perspective, the synthesis route and cost of the adsorbent, as well as the separation and recovery methods and their effectiveness, are also important factors to consider. Therefore, it is essential to invent an adsorbent that can be prepared in batches using a simple method, possessing high efficiency and selectivity for adsorbing noble metal ions, and a simple, low-cost method for the adsorption and enrichment of noble metal ions. Summary of the Invention

[0004] To achieve efficient and highly selective adsorption, enrichment, and separation of Au(III), Ag(I), and Pd(II) in water, this invention provides a magnetic nanocomposite material for adsorbing noble metal ions, its preparation method, and its applications. The magnetic nanocomposite material provided by this invention can selectively adsorb over 99% of Au(III), Ag(I), and Pd(II) from more than 20 metal ions within 10 minutes, and can rapidly achieve the separation of noble metals by applying an external magnetic field.

[0005] This invention first provides a magnetic nanocomposite material, which is composed of Fe, FeS, carbon layers and porous carbon; The Fe, FeS, carbon layers, and porous carbon all have nanoscale dimensions and structures. The magnetic nanocomposite material has the following structure: embedded nanospheres are uniformly distributed in the porous carbon network structure; the nanospheres have a core-shell structure, with the core being Fe, the shell being FeS, and the outside being wrapped with a carbon layer.

[0006] In the above-mentioned magnetic nanocomposite materials, the diameter of Fe is 5~80 nm, specifically 10 nm; The thickness of the FeS is 2~400 nm, specifically 5 nm; The thickness of the carbon layer is 1~20 nm, specifically 1~2 nm; The specific surface area of ​​the magnetic nanocomposite material is 200~800 m². 2 / g, specifically 387.7 m 2 / g.

[0007] In the aforementioned magnetic nanocomposite material, the porous carbon has mesopores and micropores of 0.5~30 nm, wherein the micropore diameter is 1~2 nm.

[0008] In the above-mentioned magnetic nanocomposite materials, the mesopore diameter is 4~30 nm.

[0009] Furthermore, the present invention provides a method for preparing the above-mentioned magnetic nanocomposite material, comprising the following steps: (1) A hydrogel was obtained by mixing and crosslinking a carrageenan solution and an ethanol solution of FeCl3; the hydrogel was then freeze-dried under vacuum to obtain an iron-containing aerogel. (2) The iron-containing aerogel is carbonized at high temperature to obtain the magnetic nanocomposite material.

[0010] In the above preparation method, step (1) specifically includes the following steps: adding carrageenan solution dropwise to FeCl3 ethanol solution, crosslinking to obtain hydrogel; freezing the hydrogel in liquid nitrogen, and then freeze-drying it under vacuum to obtain iron-containing aerogel; Specifically, the freezing time in liquid nitrogen is 10-30 minutes, specifically 15 minutes; Before freezing in liquid nitrogen, the hydrogel is washed; more specifically, the washing is done with distilled water, and the washing is performed 3 to 5 times.

[0011] In the above preparation method, the carrageenan is at least one of κ-type carrageenan, ι-type carrageenan, and λ-type carrageenan; The concentration of the carrageenan solution is 1 wt% to 10 wt%, specifically 4 wt%. The concentration of the FeCl3 ethanol solution is 1 wt% to 10 wt%, specifically 3 wt%. The volume ratio of the carrageenan solution to the FeCl3 ethanol solution is 1:1 to 10, specifically 15:100.

[0012] In the above preparation method, the crosslinking time is 20 min to 24 h, specifically 5 h; The vacuum freeze-drying time is 12 h-48 h, specifically 24 h.

[0013] In the above preparation method, the high-temperature carbonization is carried out in an inert atmosphere; specifically, the inert atmosphere includes, but is not limited to, nitrogen, argon and mixed gases. The high-temperature carbonization temperature is 600~1000 ℃, specifically 700 ℃; the high-temperature carbonization time is 1~4 h, specifically 2 h. The heating rate for high-temperature carbonization is 1~10℃ / min, specifically 5℃ / min.

[0014] The application of the above-mentioned magnetic nanocomposite materials in the adsorption, enrichment and / or separation and recovery of precious metal ions in water is also within the scope of protection of this invention; In the above applications, the noble metal ion may be at least one of Au(III), Ag(I), and Pd(II); The concentration of Au(III), Ag(I), or Pd(II) in the water body is 0.001~1000 mg / L; the amount of adsorbent used is 0.01~100 mg / mL; and the pH value of the water body is 1~7. The water body also contains at least one ion selected from Mg(II), Al(III), Ca(II), Cr(VI), Mn(II), Co(II), Ni(II), Cu(II), Zn(II), As(V), Cd(II), Pb(II), V(V), Ga(III), Rb(I), Sr(II), In(III), Cs(I), Ba(II), Tl(I), Bi(III), Ru(VI), Rh(III), Sn(II), Sb(V) and Ir(III).

[0015] Finally, the present invention provides a method for recovering precious metal ions in water, comprising the following steps: dispersing the above-mentioned magnetic nanomaterials in water containing at least one of Au(III), Ag(I) and Pd(II), and separating them after adsorption and enrichment.

[0016] In the above-mentioned recycling methods, the dispersion method includes, but is not limited to, shaking, stirring or ultrasonic treatment; The adsorption and enrichment time is 1~60 min, specifically 3~10 min; The concentration of Au(III), Ag(I) or Pd(II) is 0.001~1000 mg / L, specifically 100 μg / L or 10 mg / L; The adsorbent dosage is 0.01~100 mg / mL, specifically 0.2 or 0.3 mg / mL; the pH value of the water body is 1~7; The separation methods include, but are not limited to, magnetic separation, filtration separation, and centrifugal separation.

[0017] The water body also contains at least one ion selected from Mg(II), Al(III), Ca(II), Cr(VI), Mn(II), Co(II), Ni(II), Cu(II), Zn(II), As(V), Cd(II), Pb(II), V(V), Ga(III), Rb(I), Sr(II), In(III), Cs(I), Ba(II), Tl(I), Bi(III), Ru(VI), Rh(III), Sn(II), Sb(V) and Ir(III).

[0018] The present invention has the following beneficial effects: (1) The magnetic nanocomposite material provided by the present invention has high affinity and high selectivity for Au(III), Ag(I) and Pd(II), and is also magnetic, which can be quickly separated and recovered from the solution. It is convenient to use and low in cost. (2) The raw materials used in the preparation method of magnetic nanocomposite materials provided by the present invention are readily available, and the synthesis route is simple and economical; (3) The magnetic nanocomposite material provided by the present invention can selectively adsorb trace amounts of Au(III), Ag(I) and Pd(II) from a solution containing more than 20 metal ions within 10 min, and has the characteristics of fast adsorption speed, high adsorption rate and good adsorption selectivity. At the same time, the adsorption enrichment and separation method of the present invention is simple to operate and has a wide range of applications. Attached Figure Description

[0019] Figure 1 The image shows an XRD pattern of the magnetic nanocomposite material prepared in Example 1.

[0020] Figure 2 The image shows the Raman spectrum of the magnetic nanocomposite material prepared in Example 1.

[0021] Figure 3 These are morphological characterization images of the magnetic nanocomposite material prepared in Example 1, wherein... Figure 3 In the image, 'a' is the SEM image and 'b' is the TEM image.

[0022] Figure 4The nitrogen adsorption / desorption isotherms and pore size distribution of the magnetic nanocomposite material prepared in Example 1 are shown.

[0023] Figure 5 The kinetic process of Au(III) adsorption in solution by the magnetic nanocomposite material in Example 2 is shown in the curve of the relationship between the concentration of Au(III) in solution and the adsorption enrichment time.

[0024] Figure 6 The kinetic process of Ag(I) adsorption in solution by the magnetic nanocomposite material in Example 3 is shown in the curve of the relationship between the concentration of Ag(I) in solution and the adsorption enrichment time.

[0025] Figure 7 The kinetic process of Pd(II) adsorption in solution by the magnetic nanocomposite material in Example 4 is shown in the curve of the relationship between the concentration of Pd(II) in solution and the adsorption enrichment time.

[0026] Figure 8 The kinetics of the adsorption of trace Ag(I) in the solution by the magnetic nanocomposite material in Example 5 is shown in the curve of the relationship between the concentration of Ag(I) in the solution and the adsorption enrichment time.

[0027] Figure 9 The adsorption enrichment rate of Ag(I) in different water bodies by the magnetic nanocomposite material in Example 6 is shown.

[0028] Figure 10 The adsorption enrichment rate of Ag(I) in water at different pH values ​​for the magnetic nanocomposite material in Example 7 is shown.

[0029] Figure 11 This demonstrates the selective adsorption and enrichment of different metal ions in water by the magnetic nanocomposite material in Example 8.

[0030] Figure 12 The magnetic separation performance of the magnetic nanocomposite material in water in Example 9 is shown. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to specific embodiments. The embodiments given are only for illustrating the present invention and are not intended to limit the scope of the present invention.

[0032] Unless otherwise specified, the experimental methods described in the following examples are conventional methods.

[0033] In the quantitative experiments in the following examples, three replicate experiments were set up, and the average value of the results was taken.

[0034] Unless otherwise specified, the materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0035] The ι-type carrageenan used in the following examples was purchased from Aladdin Reagents (Shanghai) Co., Ltd., CAS No.: 9062-07-1.

[0036] Example 1: Preparation of magnetic nanocomposite materials (1) Preparation of iron-containing aerogel: 15 mL of 4 wt% ι-type carrageenan solution was added dropwise to 100 mL of 3 wt% FeCl3 ethanol solution, and the mixture was stirred continuously for 5 h to fully crosslink and form a hydrogel. The hydrogel was washed three times with distilled water, frozen in liquid nitrogen for 15 min, and then freeze-dried in a vacuum freeze dryer for 24 h. The product was then collected.

[0037] (2) High-temperature carbonization: After the dehydrated sample obtained in step (1) is restored to room temperature, it is placed in a tube furnace and heated to 700 ℃ at a heating rate of 5 ℃ / min under Ar atmosphere and maintained for 2 h. After cooling to room temperature, it is taken out to obtain Fe@FeS@C magnetic nanocomposite material.

[0038] The crystal structure of the obtained magnetic nanocomposite material is as follows: Figure 1 As shown, it is located at 44.7. o and 65.2 o The two strong, sharp peaks at 29.9° perfectly match the (110) and (200) crystal planes of Fe (JCPDS No. 06-0696). o 33.7 o 35.5 o 43.1 o and 53.1 o The diffraction peaks at these locations correspond to the (110), (112), (201), (114), and (300) crystal planes of FeS (JCPDS No. 37-0477), respectively. These diffraction peaks indicate that the composite material contains Fe and FeS. The Raman spectrum of the obtained magnetic nanocomposite material is as follows: Figure 2 As shown, at 1330 cm -1 and 1590 cm -1 Two peaks were observed, belonging to the in-plane vibrations of disordered amorphous carbon and crystalline graphitic carbon, respectively, confirming the existence of carbon materials. Scanning electron microscopy and transmission electron microscopy images of the magnetic nanocomposite material are shown below. Figure 3 As shown, embedded nanospheres are uniformly distributed within a three-dimensional interconnected porous carbon network structure. These nanospheres possess a core-shell structure, with a 10 nm diameter Fe core and a 5 nm thick FeS shell, further encapsulated by a 1-2 nm carbon layer. The nitrogen adsorption / desorption isotherms and pore size distribution of the resulting magnetic nanocomposite material are shown in the figure. Figure 4 As shown, its specific surface area is 387.7 m². 2 / g, with a wide pore distribution (0.5 nm~30 nm), mainly including micropores of about 1 nm and mesoporous structures of 4 nm and 26 nm.

[0039] Example 2: Adsorption and enrichment efficiency of magnetic nanocomposite materials for Au(III) in water 10 mg of the magnetic nanocomposite material prepared in Example 1 was dispersed in 50 mL of an aqueous solution containing Au(III) at a concentration of 10 mg / L and a pH of 2 (the Au(III)-containing aqueous solution was obtained by diluting a 1000 ppm gold standard solution with deionized water; the gold standard solution was purchased from the National Institute of Metrology, China). After adsorption and enrichment for 30 s, 1 min, 3 min, 5 min, 7.5 min, 10 min, 15 min, 20 min, and 30 min, the magnetic nanocomposite material adsorbed with Au(III) was separated from the water. The relationship between the Au(III) concentration in the water and the adsorption reaction time is shown below. Figure 5 As shown, calculations showed that after 30 s, 1 min, 3 min, and 5 min of the adsorption reaction, the adsorption enrichment rates of Au(III) in the water by the magnetic nanocomposite material were 73.5%, 96.3%, 97.1%, and 99.2%, respectively. Therefore, the magnetic nanocomposite material can complete the adsorption enrichment of Au(III) within 5 min, with an adsorption enrichment rate exceeding 99%.

[0040] Example 3: Adsorption and enrichment efficiency of magnetic nanocomposite materials for Ag(I) in water 10 mg of the magnetic nanocomposite material prepared in Example 1 was dispersed in 50 mL of an aqueous solution containing Ag(I) at a concentration of 10 mg / L and a pH of 2 (the aqueous solution containing Ag(I) was obtained by diluting a 1000 ppm silver standard solution with deionized water). After adsorption and enrichment for 30 s, 1 min, 3 min, 5 min, 7.5 min, 10 min, 15 min, 20 min, 30 min, and 45 min, the Ag(I)-adsorbed magnetic nanocomposite material was separated from the water. The relationship between the Ag(I) concentration in the water and the adsorption reaction time is shown below. Figure 6 As shown, calculations revealed that after 30 s, 1 min, 3 min, 5 min, 7.5 min, and 10 min of the adsorption reaction, the adsorption enrichment rates of Ag(I) in the water by the magnetic nanocomposite material were 75.4%, 84.1%, 92.5%, 96.1%, 97.6%, and 99.2%, respectively. Therefore, the magnetic nanocomposite material can complete the adsorption enrichment of Ag(I) within 10 min, with an adsorption enrichment rate exceeding 99%.

[0041] Example 4: Adsorption and enrichment efficiency of magnetic nanocomposite materials for Pd(II) in water 10 mg of the magnetic nanocomposite material prepared in Example 1 was dispersed in 50 mL of an aqueous solution containing Pd(II) at a concentration of 10 mg / L and a pH of 2 (the aqueous solution containing Pd(II) was obtained by diluting a 1000 ppm palladium standard solution with deionized water). After adsorption and enrichment for 30 s, 1 min, 3 min, 5 min, 7.5 min, 10 min, 15 min, 20 min, 30 min, and 45 min, the magnetic nanocomposite material adsorbed with Pd(II) was separated from the water. The relationship between the concentration of Pd(II) in the water and the adsorption reaction time is as follows. Figure 7 As shown, calculations revealed that after 30 s, 1 min, 3 min, 5 min, 7.5 min, and 10 min of the adsorption reaction, the adsorption enrichment rates of Pd(II) in the water by the magnetic nanocomposite material were 81.1%, 88.7%, 95.0%, 96.2%, 98.5%, and 99.1%, respectively. Therefore, the magnetic nanocomposite material can complete the adsorption and enrichment of Pd(II) within 10 min, with an adsorption enrichment rate exceeding 99%.

[0042] Example 5: Adsorption and enrichment efficiency of magnetic nanocomposite materials for trace Ag(I) in water 10 mg of the magnetic nanocomposite material prepared in Example 1 was dispersed in 50 mL of an aqueous solution containing Ag(I) at a concentration of 100 μg / L and a pH of 2 (the aqueous solution containing Ag(I) was obtained by diluting a 1000 ppm silver standard solution with deionized water). After adsorption and enrichment for 30 s, 1 min, 3 min, 5 min, 7.5 min, 10 min, 15 min, 20 min, and 30 min, the Ag(I)-adsorbed magnetic nanocomposite material was separated from the water. The relationship between the Ag(I) concentration in the water and the adsorption reaction time is as follows. Figure 8 As shown, calculations show that after 30 s, 1 min, and 3 min of adsorption reaction, the adsorption enrichment rates of Ag(I) in water by the magnetic nanocomposite material were 69.0%, 87.1%, and 99.1%, respectively. Therefore, the magnetic nanocomposite material can complete the adsorption enrichment of trace Ag(I) within 3 min, with an adsorption enrichment rate exceeding 99%.

[0043] Example 6: Adsorption and enrichment efficiency of magnetic nanocomposite materials for Ag(I) in different water bodies 10 mg of the magnetic nanocomposite material prepared in Example 1 was dispersed in 50 mL of an aqueous solution containing Ag(I). The water sources were river water (from Xiba River in Beijing), tap water (from Beijing), and deionized water (from the laboratory). The Ag(I) concentration was 100 μg / L, and the pH of the water was 2. (The aqueous solution containing Ag(I) was obtained by diluting a 1000 ppm silver standard solution with water. The water used for dilution was deionized water, tap water, and natural water from Xiba River. The Xiba River water and tap water were pre-filtered through a 0.22 μm polyethersulfone membrane). After adsorption and enrichment for 10 min, the magnetic nanocomposite material with adsorbed Ag(I) was separated from the water. The residual Ag(I) concentration in the solution was tested by ICP-MS. The adsorption and enrichment rates of the magnetic nanocomposite material for Ag(I) in river water, tap water, and deionized water were calculated to be 99.5%, 99.3%, and 99.5%, respectively. Figure 9 Therefore, magnetic nanocomposites can be used for the adsorption and enrichment of Ag(I) in different water quality environments, with an adsorption and enrichment rate exceeding 99%.

[0044] Example 7: Adsorption and enrichment efficiency of magnetic nanocomposite materials for Ag(I) in water with different pH values The pH of a solution with an Ag(I) concentration of 10 mg / L was adjusted to 2, 3, 4, 5, 6, and 7 respectively using 1 wt% NaOH and 1 wt% HNO3 (the aqueous solution containing Ag(I) was obtained by diluting a 1000 ppm silver standard solution with deionized water). 15 mg of the magnetic nanocomposite material prepared in Example 1 was dispersed in 50 mL of the above solutions. After adsorption and enrichment for 10 min, the Ag(I)-adsorbed magnetic nanocomposite material was separated from the water. The residual Ag(I) concentration in the solution was tested by ICP-MS. The adsorption and enrichment rate of the magnetic nanocomposite material for Ag(I) in water at different pH values ​​all exceeded 99%. Figure 10 This indicates that magnetic nanocomposites can be used for the adsorption and enrichment of Ag(I) in water bodies with different pH values.

[0045] Example 8: Adsorption and enrichment selectivity of magnetic nanocomposites for Au(III), Ag(I), and Pd(II) in water Ten mg of the magnetic nanocomposite material prepared in Example 1 was dispersed in 50 mL of an aqueous solution containing 29 metal ions, namely Mg(II), Al(III), Ca(II), V(V), Cr(VI), Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Ga(III), As(V), Rb(I), Sr(II), Cd(II), In(III), Cs(I), Ba(II), Tl(I), Pb(II), Bi(III), Ru(VI), Rh(III), Sn(II), Sb(V), Ir(III), Ag(I), Pd(II), and Au(III). The concentration of each metal ion was 100 μg / L, and the pH of the water was 2 (the aqueous solution of metal ions was obtained by diluting the standard solution with deionized water). After adsorption and enrichment for 10 min, the magnetic nanocomposite material with adsorbed metal ions was separated from the water. The concentration of residual metal ions in the solution was measured by ICP-MS, and the adsorption and enrichment efficiency of the magnetic nanocomposite material for different metal ions was calculated. The results are as follows: Figure 11 As shown, the magnetic nanocomposite material exhibits adsorption and enrichment rates exceeding 99% for Ag(I), Au(III), and Pd(II) in water, while its adsorption and enrichment efficiencies for other metal ions are all below 5%. This result demonstrates that the magnetic nanocomposite material exhibits extremely high selectivity for the adsorption and enrichment of Ag(I), Au(III), and Pd(II) in water even when other metal ions coexist.

[0046] Example 9: Magnetic separation capability of magnetic nanocomposites in water 10 mg of the magnetic nanocomposite material prepared in Example 1 was dispersed in 50 mL of an aqueous solution containing Ag(I) at a concentration of 10 ppm. The beaker or centrifuge tube containing the magnetic nanocomposite material was left to stand, and a 10 cm × 20 cm × 10 cm neodymium magnet was placed on the side or bottom. Note: The type and size of the magnet are not important; any magnet that can provide a magnetic field is sufficient. The magnetic nanocomposite material was separated from the water by applying an external magnetic field. The magnetic separation performance of the magnetic nanocomposite material is as follows: Figure 12 As shown. This separation operation is simple, energy-free, and can rapidly separate magnetic nanomaterials from solution.

Claims

1. A magnetic nanocomposite material, characterized in that: The magnetic nanocomposite material is composed of Fe, FeS, carbon layers, and porous carbon; The Fe, FeS, carbon layers, and porous carbon all have nanoscale dimensions and structures. The magnetic nanocomposite material has the following structure: embedded nanospheres are uniformly distributed in the porous carbon network structure; the nanospheres have a core-shell structure, with the core being Fe, the shell being FeS, and the outside being wrapped with a carbon layer.

2. The magnetic nanocomposite material according to claim 1, characterized in that: The diameter of the Fe is 5~80 nm; The thickness of the FeS is 2~400 nm; The thickness of the carbon layer is 1~20 nm; The specific surface area of the magnetic nanocomposite is 200-800 m 2 / g.

3. The magnetic nanocomposite material according to claim 1 or 2, characterized in that: The porous carbon has mesopores and micropores with a diameter of 0.5~30 nm, wherein the micropore diameter is 1~2 nm.

4. The method for preparing the magnetic nanocomposite material according to any one of claims 1-3, comprising the following steps: (1) A hydrogel was obtained by mixing and crosslinking a carrageenan solution and an ethanol solution of FeCl3; the hydrogel was then freeze-dried under vacuum to obtain an iron-containing aerogel. (2) The iron-containing aerogel is carbonized at high temperature to obtain the magnetic nanocomposite material.

5. The preparation method according to claim 4, characterized in that: Step (1) includes the following: adding carrageenan solution dropwise to FeCl3 ethanol solution to crosslink and obtain hydrogel; freezing the hydrogel in liquid nitrogen and then freeze-drying it under vacuum to obtain iron-containing aerogel.

6. The preparation method according to claim 4 or 5, characterized in that: The carrageenan is at least one of κ-type carrageenan, ι-type carrageenan, and λ-type carrageenan; The concentration of the carrageenan solution is 1 wt% to 10 wt%. The concentration of the FeCl3 ethanol solution is 1 wt%~10 wt%; The volume ratio of the carrageenan solution to the FeCl3 ethanol solution is 1:1~10.

7. The preparation method according to any one of claims 4-6, characterized in that: The crosslinking time is 20 min to 24 h; The vacuum freeze-drying time is 12 h to 48 h.

8. The preparation method according to any one of claims 4-7, characterized in that: The high-temperature carbonization is carried out in an inert atmosphere; The high-temperature carbonization temperature is 600~1000℃; the high-temperature carbonization time is 1~4 h; The heating rate for high-temperature carbonization is 1~10℃ / min.

9. The application of the magnetic nanocomposite material according to any one of claims 1-3 in the recovery of precious metal ions from water; Specifically, the noble metal ion may be at least one of Au(III), Ag(I), and Pd(II).

10. A method for recovering precious metal ions from water, comprising the following steps: dispersing the magnetic nanomaterials of any one of claims 1-3 in water containing at least one of Au(III), Ag(I) and Pd(II), and separating them after adsorption and enrichment; Specifically, the adsorption and enrichment time can be 1 to 60 min; the concentration of Au(III), Ag(I) or Pd(II) can be 0.001 to 1000 mg / L; the amount of adsorbent can be 0.01 to 100 mg / mL; and the pH value of the water can be 1 to 7.

Images