A nano zero-valent iron-magnetite composite material, a preparation method and application thereof

Abstract

This invention belongs to the field of magnetic nanomaterials technology, specifically relating to a nano-zero-valent iron-iron tetroxide composite material, its preparation method, and its application in treating electroplating wastewater. This invention utilizes carbon materials as a carrier and employs a rheological phase method, using an environmentally compatible low-sulfite solution as a reducing agent, to create nanoparticles with a zero-valent iron substrate. This process completes the generation of the nano-zero-valent iron substrate, the modification of its surface with sulfur, and the loading of biochar, resulting in a layered nano-zero-valent iron-iron tetroxide composite material. This composite material exhibits strong adsorption capacity and selectivity for heavy metal ions. The preparation method offers advantages such as low cost, low investment, and high yield, achieving more efficient and lower-cost heavy metal removal and wastewater purification.

Description

Technical Field

[0001] This invention belongs to the field of engineering magnetic nanomaterials technology, specifically relating to a nano-zero-valent iron-iron tetroxide composite material, its preparation method, and its application in treating electroplating wastewater. Background Technology

[0002] Electroplating wastewater refers to the wastewater generated after the use of metal in the electroplating process. Electroplating is a process that deposits metal ions onto the surface of a workpiece to form a metal film; it is widely used in many industrial fields. The main sources of electroplating wastewater include: metal surface pretreatment, electroplating solution rinsing, electroplating waste liquid, and equipment cooling water. The proper treatment and discharge of electroplating wastewater is a crucial aspect of environmental protection and sustainable development. Traditional treatment methods, such as neutralization precipitation, activated carbon adsorption, ion exchange, and flotation, often have high equipment requirements, poor long-term sterilization effects, cannot simultaneously complete disinfection and chemical degradation, and may also be accompanied by toxic byproducts and safety issues. Therefore, to more effectively treat electroplating wastewater and reduce its environmental impact, it is necessary to continuously research and apply new wastewater treatment technologies.

[0003] Biochar, also known as carbonaceous material, is a carbonaceous product obtained from organic raw materials through high-temperature pyrolysis or oxidation. In recent years, some progress has been made in utilizing biochar to remove pollutants from wastewater. Biochar possesses a large specific surface area and abundant pore structure, giving it excellent adsorption properties and effectively removing heavy metal ions, organic matter, and other pollutants from wastewater. Biochar itself has a certain bioremediation effect, promoting the growth and activity of microorganisms and aiding in the degradation of organic matter in wastewater. Biochar can usually be prepared using renewable resources such as agricultural and forestry waste, exhibiting good environmental friendliness. In existing technologies, carbon-supported enhanced heavy metal removal refers to using carbon materials (such as charcoal and graphite) as a carrier, combined with specific reinforcing agents. This involves functionally modifying the surface of the carbon material or loading other materials with high affinity and selective adsorption capacity (such as oxides and biomass) onto the carbon material surface to enhance its adsorption capacity and selectivity for heavy metal ions. Many methods exist for preparing nano-oxide-supported carbon materials, but these require expensive equipment and harsh production environments, and their heavy metal removal capacity is limited. Summary of the Invention

[0004] One objective of this invention is to overcome the aforementioned problems in traditional technologies and provide a method for preparing nano-zero-valent iron-iron tetroxide composite materials. Utilizing a rheological phase method, an environmentally compatible low-sulfite solution is used as a reducing agent to prepare the nano-zero-valent iron-iron tetroxide composite material. This material not only exhibits extremely high organic matter degradation performance but also good environmental friendliness and strong heavy metal removal activity. The preparation method is characterized by low cost, low investment, and high yield, enabling more efficient and low-cost heavy metal removal and wastewater purification for treating electroplating wastewater. Further surface modification of the nano-zero-valent iron-iron tetroxide composite material can further enhance the reactivity of the nanoparticles.

[0005] To achieve the above objectives, the present invention employs the following technical solution: a method for preparing a nano-zero-valent iron-iron tetroxide composite material, comprising the following steps:

[0006] S1. Weigh sodium hydroxide powder, sodium dithionite and sieved biochar and mix them evenly to obtain a solid mixture. Add ferrous chloride and / or ferrous sulfate to the solid mixture and stir to react to obtain a mixed reactant.

[0007] S2. Place the mixed reactants under ice bath conditions, spray deionized water into the mixed reactants while stirring, so that the mixed reactants react in a rheological phase state.

[0008] S3. After the reaction is complete, stop stirring, let it stand and cool to room temperature, then filter. The separated solid product is washed until neutral and then vacuum dried to obtain nano-zero-valent iron-iron tetroxide composite material.

[0009] Further improvements to the preparation method of nano-zero-valent iron-iron tetroxide composite materials:

[0010] Preferably, in step S1, the mass ratio of sodium hydroxide powder, sodium dithionite, and sieved biochar is 4:4:1.

[0011] Preferably, the mass ratio of the solid mixture, ferrous chloride and / or ferrous sulfate to the sprayed deionized water is 9:4:5.

[0012] Preferably, the preparation method of sieved biochar in step S1 is as follows: wash, cut and dry rice husks, put them into an anaerobic tube furnace, pyrolyze them at a high temperature of 400℃-500℃ for 3-6 hours, and after cooling, grind them through a sieve of 100 mesh or more to obtain biochar.

[0013] Preferably, the flow rate of the deionized water sprayed in step S2 is 10-15 mL / min.

[0014] Preferably, the operations in steps S1-S3 are performed in a glove box, and the temperature of the ice bath in step S2 is 0-10℃.

[0015] Preferably, the solid product separated in step S3 is washed with oxygen-free distilled water, anhydrous ethanol or dilute hydrochloric acid until neutral, and the vacuum drying temperature is 50-60°C.

[0016] Preferably, the solid product separated in step S3 is washed by ultrasonic cleaning, with a frequency of 30kHz-50kHz and a power of 600W-900W.

[0017] The second objective of this invention is to provide a method for preparing nano-zero-valent iron-iron tetroxide composite material according to any one of the above-mentioned methods, resulting in a nano-zero-valent iron-iron tetroxide composite material.

[0018] The third objective of this invention is to provide an application of the above-mentioned nano-zero-valent iron-iron tetroxide composite material in the treatment of electroplating wastewater.

[0019] The advantages of this invention compared to the prior art are as follows:

[0020] 1) This invention provides a method for preparing nano-zero-valent iron-iron tetroxide composite materials. It utilizes widely available carbon materials (such as rice husk biochar) as a carrier, and through a reaction, the substrate of the generated nanoparticles is zero-valent iron. Using a rheological phase method, an environmentally compatible low-sulfite solution is used as a reducing agent to simultaneously complete the generation of the nano-zero-valent iron substrate, the modification of its surface with sulfur, and the loading of biochar, thereby enhancing its adsorption capacity and selectivity for heavy metal ions. This preparation method is simple, avoids the disadvantages of traditional methods such as toxic byproducts and harsh conditions, has low production costs, and uses widely available raw materials, reducing the environmental hazards of traditional carbon-loaded reinforced heavy metal ion removal composite material production processes.

[0021] 2) The nano-zero-valent iron-iron tetroxide composite material prepared by this invention undergoes non-metallic and metallic modification on the surface of zero-valent iron, which enhances its reactivity and decontamination ability, making it highly effective in the treatment of electroplating wastewater. It can effectively solve problems such as high heavy metal ion content, and the difficulty in degrading organic matter and chemical residues in electroplating wastewater, thus reducing environmental pollution. The preparation method of this invention consists of multiple steps and stages. Through continuous improvement and optimization, from raw material preparation and reaction process control to product purification, the advantages of each stage can be fully utilized, making the preparation method more efficient, economical, and environmentally friendly, ultimately achieving the technical objectives. Attached Figure Description

[0022] Figure 1 This is a scanning electron microscope image of the nano-zero-valent iron-iron tetroxide composite material prepared in Example 1 of the present invention.

[0023] Figure 2 This is an X-ray diffraction pattern of the nano-zero-valent iron-iron tetroxide composite material prepared in Example 1 of the present invention.

[0024] Figure 3 This is a schematic diagram showing the relationship between the lead removal rate in simulated Pb(II) wastewater containing lead and time when using the nano-zero-valent iron-iron tetroxide composite material of Example 1 to remove lead-containing wastewater with a concentration of 20 mg / L.

[0025] Figure 4 This is a schematic diagram showing the relationship between the lead removal rate in simulated Pb(II) wastewater containing lead and time when using the nano-zero-valent iron-iron tetroxide composite material of Example 2 to remove lead-containing wastewater with a concentration of 30 mg / L.

[0026] Figure 5 This is a schematic diagram showing the relationship between the maximum lead removal rate in simulated Pb(II) wastewater and the number of cycles after using the nano-zero-valent iron-iron tetroxide composite material of Example 1 to remove lead-containing wastewater.

[0027] Figure 6 This is a schematic diagram showing the relationship between the maximum lead removal rate in simulated Pb(II) wastewater and the number of cycles after using the nano-zero-valent iron-iron tetroxide composite material of Example 2 to remove lead-containing wastewater. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0029] Example 1

[0030] This embodiment provides a method for preparing nano-zero-valent iron-iron tetroxide composite material, which specifically includes the following steps:

[0031] S1. After washing, cutting and drying the rice husks, put them into an anaerobic tube furnace and pyrolyze them at a high temperature of 450℃ for 4 hours. After cooling, grind them through a 100-mesh sieve to obtain biochar that has passed through a 100-mesh sieve.

[0032] Weigh 20g of granular NaOH, 20g of Na2S2O4 and 5g of biochar that has passed through a 100-mesh sieve in a glove box, and mix them evenly to obtain a solid mixture.

[0033] S2. In a glove box, add 20g of ferrous chloride (FeCl2) to the solid mixture under stirring. After stirring evenly, react for 2min. Then place it in an ice bath at 0-10℃ and spray 25mL of deionized water into the solid mixture at a flow rate of 10mL / min while stirring to allow the reactants to react in a rheotropic phase.

[0034] S3. After the reaction is complete, stop stirring and let the reaction solution stand for 2 hours to precipitate. Filter the cooled reaction product under nitrogen protection. The separated solid product is repeatedly ultrasonically washed with anhydrous ethanol at a frequency of 30kHz and a power of 600W until the pH is neutral. After vacuum drying, the nano-zero-valent iron-iron tetroxide composite material is obtained.

[0035] The scanning electron microscope image of the nano-zero-valent iron-iron tetroxide composite material prepared in this embodiment is as follows: Figure 1 As shown, it is a layered nano-zero-valent iron-iron tetroxide composite material with an overall core-shell structure. The core layer is composed of zero-valent iron, and the shell layer is composed of iron sulfide and biochar. The average particle size is 50-100 nm.

[0036] The X-ray diffraction results of the nano-zero-valent iron-iron tetroxide composite material prepared in this embodiment are as follows: Figure 2 As shown, it is evident that obvious α-Fe diffraction peaks appeared in the rheological reaction products, and the main phases of the nanoparticles were SiO2 and Fe.

[0037] 500 mL of water with a Pb(II) concentration of 20 mg / L was prepared as the wastewater to be treated and placed in a 1000 mL Erlenmeyer flask with a stopper. The flask was placed in a constant-temperature shaker at 25 °C and a rotation speed of 200 r / min. 0.5 g of nano-zero-valent iron-iron tetroxide composite material was added. Samples were taken at regular intervals. After filtering the water samples through a 0.22 μm filter membrane, atomic absorption spectrometry was used to determine the lead content. The adsorption was confirmed when the lead content of each water sample no longer changed. The change in lead removal rate in the wastewater over time is shown in the figure below. Figure 3 As shown, by Figure 3 It can be seen that the lead in the wastewater was completely removed after 2 hours. After standing for 2 hours, the upper layer of the wastewater became clear, and the nano-zero-valent iron-iron tetroxide composite material can be recycled and reused using a magnet.

[0038] The specific steps for recycling and reuse are as follows: First, the used nano-zero-valent iron-iron tetroxide composite material is removed using a magnet-wrapped plastic wrap method. Then, it is placed in a beaker containing deionized water, stirred and rinsed, and regenerated in hydrochloric acid. It is then used to treat wastewater with a Pb(II) concentration of 20 mg / L. The nano-zero-valent iron-iron tetroxide composite material is repeatedly used for wastewater treatment, removed, rinsed, and regenerated four times. The removal rate for each operation is calculated, and the results are as follows: Figure 5 As shown. According to Figure 5 As a result, with the increase of regeneration times, the removal rate of Pb(II) gradually decreased, and the rate of decrease gradually increased. After the 5th regeneration, the maximum removal rate of Pb(II) decreased from 96% to 75.63%, indicating that the material has outstanding recycling performance.

[0039] Example 2

[0040] This embodiment provides a method for preparing nano-zero-valent iron-iron tetroxide composite material, which specifically includes the following steps:

[0041] S1. After washing, cutting, and drying the rice husks, put them into an anaerobic tube furnace and pyrolyze them at a high temperature of 450℃ for 4 hours. After cooling, grind them through a 100-mesh sieve to obtain biochar that has passed through a 100-mesh sieve.

[0042] Weigh 20g of granular NaOH, 20g of Na2S2O4 and 5g of biochar that has passed through a 100-mesh sieve in a glove box, and mix them evenly to obtain a solid mixture.

[0043] S2. In a glove box, add 10g of ferrous chloride (FeCl2) and 10g of ferrous sulfate (FeSO4) to the solid mixture under stirring. After stirring evenly, react for 2 minutes. Then place it in an ice bath at 0-10℃ and spray 25mL of deionized water into the solid mixture with a spray bottle at a flow rate of 15mL / min while stirring to allow the reactants to react in a rheotropic phase.

[0044] S3. After the reaction is complete, stop stirring and let the reaction solution stand for 2 hours to precipitate. Filter the cooled reaction product under nitrogen protection. The separated solid product is repeatedly ultrasonically washed with oxygen-free distilled water, anhydrous ethanol or dilute hydrochloric acid. The ultrasonic cleaner has a frequency of 30kHz and a power of 600W. The product is washed until the pH is neutral and then vacuum dried to obtain the nano-zero-valent iron-iron tetroxide composite material.

[0045] 500 mL of water with a Pb(II) concentration of 30 mg / L was prepared as the wastewater to be treated and placed in a 1000 mL Erlenmeyer flask with a stopper. The flask was placed in a constant-temperature shaker at 25 °C and a rotation speed of 200 r / min. 0.5 g of nano-zero-valent iron-iron tetroxide composite material was added. Samples were taken at regular intervals. After filtering the water samples through a 0.22 μm filter membrane, atomic absorption spectrometry was used to determine the lead content. The adsorption was confirmed when the lead content of each water sample no longer changed. The change in lead removal rate in the wastewater over time is shown in the figure below. Figure 4 As shown, by Figure 4 It can be seen that the lead removal rate in the wastewater is about 70% after 2 hours. After standing for 2 hours, the upper layer of wastewater becomes clear and can be recycled and reused using a magnet.

[0046] The specific steps for recycling and reuse are as follows: First, the used nano-zero-valent iron-iron tetroxide composite material is removed using a magnet-wrapped plastic wrap method. Then, it is placed in a beaker containing deionized water, stirred and rinsed, and regenerated in hydrochloric acid. It is then used to treat wastewater with a Pb(II) concentration of 20 mg / L. The nano-zero-valent iron-iron tetroxide composite material is repeatedly used for wastewater treatment, removed, rinsed, and regenerated four times. The removal rate for each operation is calculated, and the results are as follows: Figure 6 As shown. According to Figure 6 As a result, with the increase of regeneration times, the removal rate of Pb(II) gradually decreased, and the rate of decrease gradually increased. After the 5th regeneration, the maximum removal rate of Pb(II) decreased from 71.9% to 44.99%, indicating that the material has outstanding recycling performance.

[0047] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. The selection and detailed description of these embodiments in this specification are intended to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a nano-zero-valent iron-iron tetroxide composite material, characterized in that, Includes the following steps: S1. Weigh sodium hydroxide powder, sodium dithionite and sieved biochar and mix them evenly to obtain a solid mixture. Add ferrous chloride and / or ferrous sulfate to the solid mixture and stir to react to obtain a mixed reactant. S2. Place the mixed reactants under ice bath conditions, spray deionized water into the mixed reactants while stirring, so that the mixed reactants react in a rheological phase state. S3. After the reaction is complete, stop stirring, let it stand and cool to room temperature, then filter. The separated solid product is washed until neutral and then vacuum dried to obtain nano-zero-valent iron-iron tetroxide composite material.

2. The method for preparing a nano-zero-valent iron-iron tetroxide composite material according to claim 1, characterized in that, In step S1, the mass ratio of sodium hydroxide powder, sodium dithionite, and sieved biochar is 4:4:

1.

3. The method for preparing a nano-zero-valent iron-iron tetroxide composite material according to claim 1, characterized in that, The mass ratio of the solid mixture, ferrous chloride and / or ferrous sulfate, to the sprayed deionized water is 9:4:

5.

4. The method for preparing a nano-zero-valent iron-iron tetroxide composite material according to claim 1, characterized in that, The preparation method of sieved biochar in step S1 is as follows: Wash, cut and dry rice husks, put them into an anaerobic tube furnace, pyrolyze them at a high temperature of 400℃-500℃ for 3-6 hours, and after cooling, grind them through a sieve of more than 100 mesh to obtain biochar.

5. The method for preparing a nano-zero-valent iron-iron tetroxide composite material according to claim 1, characterized in that, The flow rate of the deionized water sprayed in step S2 is 10-15 mL / min.

6. The method for preparing a nano-zero-valent iron-iron tetroxide composite material according to claim 1, characterized in that, The operations in steps S1-S3 are carried out in the glove box, and the temperature of the ice bath in step S2 is 0-10℃.

7. The method for preparing a nano-zero-valent iron-iron tetroxide composite material according to claim 1, characterized in that, The solid product separated in step S3 is washed with oxygen-free distilled water, anhydrous ethanol or dilute hydrochloric acid until neutral, and then vacuum dried at a temperature of 50-60℃.

8. The method for preparing a nano-zero-valent iron-iron tetroxide composite material according to claim 7, characterized in that, The solid product separated in step S3 is washed by ultrasonic cleaning at a frequency of 30kHz-50kHz and a power of 600W-900W.

9. A nano-zero-valent iron-iron tetroxide composite material prepared by the preparation method of any one of claims 1-8.

10. The application of the nano-zero-valent iron-iron tetroxide composite material as described in claim 9 in the treatment of electroplating wastewater.

Images