Heavy metal passivation stabilizing material and preparation method and application thereof

Abstract

This invention discloses a heavy metal passivation and stabilization material, its preparation method, and its application. The heavy metal passivation and stabilization material provided by this invention includes iron-carbon micro / nanofibers and CeO2 nanoparticles loaded on the iron-carbon micro / nanofibers. The above-mentioned heavy metal passivation and stabilization material provided by this invention uses iron-carbon micro / nanofibers as the carrier material. The carrier material is composed of stacked nanoparticles with an uneven surface, providing uniform and abundant nucleation sites for the loaded CeO2, thus stabilizing a large number of loaded CeO2 nanoparticles. Experimental results show that the iron-carbon micro / nanofibers@CeO2 prepared by this invention have good adsorption, passivation, and stabilization effects on heavy metals, especially arsenic, in various media, and also have a good removal effect on arsenic even at low dosages.

Description

Technical Field

[0001] This invention relates to the field of composite materials technology, and more specifically, to a heavy metal passivation and stabilization material, its preparation method, and its application. Background Technology

[0002] Arsenic has existed in nature for a long time, and its toxicity has a long history, with certain levels found in soil background levels. In the International Agency for Research on Cancer's list of heavy metal carcinogens, As is classified as a Group 1 carcinogen. The toxicity of arsenic varies depending on its valence state, and is categorized into acute and chronic toxicity.

[0003] Common arsenic stabilizing materials include zeolite, attapulgite, maifanite, lime, and talc, but their drawbacks, such as low adsorption capacity, are also quite prominent. To improve the adsorption effect, some methods use these materials as basic raw materials and load them with high-valence metal ions or nanoparticles through impregnation, adsorption, sintering, etc., to achieve better arsenic removal. There are also methods that load nano-sized high-valence metal oxide particles to significantly improve the adsorption and removal effect of arsenic. However, all of these methods generally suffer from high material production costs and problems with daily use and maintenance, which to some extent limits the widespread application of these materials. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects of the prior art by providing a heavy metal passivation and stabilization material, its preparation method, and its application.

[0005] The technical problem solved by this invention is achieved by the following technical solution.

[0006] This invention provides a heavy metal passivation and stabilization material, which includes iron-carbon micro / nanofibers and CeO2 nanoparticles loaded on the iron-carbon micro / nanofibers.

[0007] The present invention also provides a method for preparing the above-mentioned heavy metal passivation and stabilization material, which includes: preparing iron-carbon micro / nanofibers by electrospinning, then mixing the iron-carbon micro / nanofibers with a cerium source solution, adding an alkali to convert cerium ions into cerium hydroxide and adsorbing them onto the iron-carbon micro / nanofibers, and then obtaining the heavy metal passivation and stabilization material by hydrothermal treatment.

[0008] The present invention also provides an application of the above-mentioned heavy metal passivation and stabilization material in the oxidation and / or passivation of heavy metals; preferably, the application in the oxidation and / or passivation of heavy metals in soil and water; preferably, the heavy metal includes any one or more of arsenic, mercury, and lead; more preferably, the heavy metal is arsenic.

[0009] The present invention has the following beneficial effects:

[0010] This invention provides a heavy metal passivation and stabilization material, its preparation method, and its application. The heavy metal passivation and stabilization material provided by this invention includes iron-carbon micro / nanofibers and CeO2 nanoparticles loaded on the iron-carbon micro / nanofibers. The heavy metal passivation and stabilization material provided above uses iron-carbon micro / nanofibers as a carrier. The carrier has advantages such as high mechanical strength, high porosity, and large specific surface area, which can provide a large number of nucleation sites for CeO2 nanoparticles, allowing them to be loaded onto the iron-carbon micro / nanofibers in large quantities. This enables CeO2 to oxidize and passivate heavy metals. Therefore, the heavy metal passivation and stabilization material provided by this invention exhibits good adsorption performance for heavy metals, especially arsenic, in water or soil across multiple media and a wide pH range, and is expected to be widely used in the treatment of heavy metal pollution, especially arsenic, in various water or soil bodies. Attached Figure Description

[0011] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 The images show SEM images of the iron-carbon micro / nanofibers and iron-carbon micro / nanofibers@CeO2 prepared in Example 1, where image a shows the iron-carbon micro / nanofibers and image b shows the iron-carbon micro / nanofibers@CeO2.

[0013] Figure 2 The image shows the @CeO2 EDS analysis spectrum of the iron-carbon micro / nanofibers prepared in Example 1.

[0014] Figure 3 The XRD spectrum of cerium dioxide;

[0015] Figure 4 The image shows the XRD spectrum of the iron-carbon micro / nanofibers@CeO2 prepared in Example 1.

[0016] Figure 5 This is a SEM image of the iron-carbon micro / nanofibers@CeO2 prepared in Example 2;

[0017] Figure 6 This is a SEM image of the iron-carbon micro / nanofibers@CeO2 prepared in Example 3;

[0018] Figure 7 SEM images of iron-carbon micro / nanofibers@CeO2 prepared under different PVP and PAN dosages in Comparative Example 1;

[0019] Figure 8SEM images of iron-carbon micro / nanofiber @CeO2 prepared at different calcination temperatures in Comparative Example 2;

[0020] Figure 9 SEM image of the iron-carbon micro / nanofibers@CeO2 prepared in Comparative Example 3;

[0021] Figure 10 A comparison chart showing the arsenic absorption effects of different materials;

[0022] Figure 11 The curves showing the effect of different aqueous solution pH values ​​on arsenic adsorption efficiency;

[0023] Figure 12 Comparison of heavy metal selectivity between iron-carbon micro / nanofibers and iron-carbon micro / nanofibers@CeO2;

[0024] Figure 13 The removal efficiency curves of arsenic by iron-carbon micro / nanofibers@CeO2 with different anion concentrations are shown.

[0025] Figure 14 A comparison of the adsorption capacities of attapulgite@MnO2 and iron-carbon micro / nanofibers@CeO2;

[0026] Figure 15 Figure 1 shows the SEM images and EDS analysis results of cerium dioxide micro / nanofiber and iron-carbon micro / nanofiber @CeO2. Figure 2a shows the SEM and EDS analysis of cerium dioxide micro / nanofiber; Figure 2b shows the SEM and EDS analysis of iron-carbon micro / nanofiber @CeO2.

[0027] Figure 16 A comparison of the adsorption capacities of cerium dioxide micro / nanofibers and iron-carbon micro / nanofibers @CeO2;

[0028] Figure 17 The curve shows the change in arsenic concentration in the leachate. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0030] In recent years, the combination of nanotechnology and adsorbents has greatly improved the arsenic removal performance of adsorbents. Artificially synthesized adsorbents are even more adaptable, capable of treating specific wastewaters and suitable for the removal of arsenic from soil and groundwater. However, how to combine adsorbents with nanotechnology, that is, to select a suitable substrate as a material for supporting nano-metal oxides, has always been a challenge.

[0031] Through long-term practice, the inventors have proposed a heavy metal passivation and stabilization material and its preparation method, which uses iron-carbon micro- and nanofibers as a carrier and loads CeO2 nanoparticles on the carrier.

[0032] CeO2 has good acid and alkali resistance and can adsorb heavy metal ions without dissolving. Cerium dioxide has a large specific surface area and adsorption sites. The presence of surface hydroxyl groups can effectively adsorb arsenic. Its adsorption and co-precipitation mechanism is that As(V) and As(III) maintain their original redox state on the surface of cerium dioxide, forming a ligand complex on its surface and slowly forming a precipitate. Moreover, cerium dioxide has a good adsorption effect on arsenic in a wide pH range.

[0033] Electrospinning is a technique that uses a high-voltage electrostatic field to prepare long fibers with diameters on the nanoscale from polymer solutions. The resulting fiber materials possess a range of advantages, including high porosity and high specific surface area, and have been widely applied in the environmental field. Most importantly, due to their modifiable nature, various structures and functions can be designed to remove pollutants in different environments, making them an excellent substrate material. Therefore, electrospun micro / nanofibers hold significant research potential and broad prospects in environmental remediation.

[0034] In this invention, iron-carbon micro-nanofibers are prepared by electrospinning. A large number of CeO2 nanoparticles are loaded on the surface of the iron-carbon micro-nanofibers to obtain a composite material with the composition of iron-carbon micro-nanofibers@CeO2. This composite material has the characteristics of high adsorption efficiency of heavy metals, especially arsenic (98%), wide applicability, low cost, simple process, strong stability and green environmental protection.

[0035] The following is a detailed description of a heavy metal passivation and stabilization material, its preparation method, and its application provided by embodiments of the present invention.

[0036] In a first aspect, embodiments of the present invention provide a heavy metal passivation stabilization material, which includes iron-carbon micro / nanofibers and CeO2 nanoparticles loaded on the iron-carbon micro / nanofibers.

[0037] This invention provides a heavy metal passivation and stabilization material, comprising iron-carbon micro / nanofibers and CeO2 nanoparticles loaded on the iron-carbon micro / nanofibers. The provided heavy metal passivation and stabilization material uses iron-carbon micro / nanofibers as a carrier. This carrier possesses advantages such as high mechanical strength, high porosity, and large specific surface area, providing numerous nucleation sites for the CeO2 nanoparticles and enabling the loading of a large number of CeO2 nanoparticles onto the iron-carbon micro / nanofibers. The heavy metal passivation and stabilization material provided by this invention exhibits excellent adsorption effects on heavy metals, especially arsenic, in water or soil across multiple media and a wide pH range, making it an superior heavy metal passivation and stabilization material.

[0038] In an optional embodiment, the heavy metal passivation and stabilization material is composed of iron-carbon micro / nanofibers@CeO2, where the CeO2 nanoparticles have a particle size of 6-9 nm and the iron-carbon micro / nanofibers have a size of 100-500 nm.

[0039] Secondly, embodiments of the present invention provide a method for preparing the above-mentioned heavy metal passivation and stabilization material, which includes: preparing iron-carbon micro / nanofibers by electrospinning, then mixing the iron-carbon micro / nanofibers with a cerium source solution, adding an alkali to convert cerium ions into cerium hydroxide and adsorbing them onto the iron-carbon micro / nanofibers, and obtaining the heavy metal passivation and stabilization material by hydrothermal treatment.

[0040] This invention provides a method for preparing the aforementioned heavy metal passivation and stabilization material, comprising: firstly, preparing iron-carbon micro / nanofibers using electrospinning. Electrospinning technology can produce micro / nano interfaces with good stability, and the micro / nanofibers are composed of stacked nanoparticles with an uneven surface, providing a uniform and abundant number of nucleation sites for the loaded metal oxide. Subsequently, the prepared iron-carbon micro / nanofibers are mixed with a cerium source solution, and an alkali is added to convert cerium ions into cerium hydroxide. The positively charged spun fibers attract the negatively charged cerium hydroxide from the aqueous phase to the fiber surface, forming a stable structure. Further, a hydrothermal method is used to uniformly and orderly grow a large number of cerium dioxide nanoparticles on the surface of the micro / nanofibers, obtaining a material composed of iron-carbon micro / nanofibers@CeO2. Furthermore, this invention utilizes the spinnability and flexibility of the fibers to create different shapes according to different application scenarios. This allows the material prepared according to this invention to be applicable to the stabilization and passivation treatment of heavy metals in various scenarios.

[0041] In an optional embodiment, the method includes the following steps: mixing a spinning aid, a solvent, and an iron source to obtain a spinning solution; loading the spinning solution into a syringe; preparing a precursor using electrospinning; annealing the precursor to obtain iron-carbon micro / nanofibers; mixing the iron-carbon micro / nanofibers with a cerium source solution; adding ammonia to convert cerium ions into cerium hydroxide and adsorb them onto the iron-carbon micro / nanofibers; adjusting the pH and continuously stirring to obtain a suspension; and subjecting the suspension to hydrothermal treatment to obtain a heavy metal passivation and stabilization material.

[0042] In an optional embodiment, one or more of polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), polyacrylic acid (PAA) and polyacrylonitrile (PAN) are used as spinning aids, N,N-dimethylformamide (DMF) is used as a solvent, and ferric chloride hexahydrate is used as an iron source to prepare the spinning solution.

[0043] Preferably, polyvinylpyrrolidone (PVP) and polyacrylonitrile (PAN) are used as spinning aids, N,N-dimethylformamide (DMF) is used as a solvent, and ferric chloride hexahydrate is used as an iron source to prepare the spinning solution. The amount of PVP and PAN added to the spinning solution is 10wt%-14wt%, and the ratio of PVP to PAN is 0.5-1:1.

[0044] Preferably, the dosage of ferric chloride hexahydrate is 8wt%-12wt%.

[0045] Excessive PVP and PAN dosages increase the interaction between micro / nanofibers, making them prone to aggregation. Conversely, insufficient dosages result in lower solution viscosity, poor morphological control of iron-carbon micro / nanofibers, and thus produce thin, isolated fibers with poor connectivity. Excessive iron source dosage leads to the dissolution of iron from the carbon-iron micro / nanofiber fibers.

[0046] In an optional implementation, the spinning parameters are set as follows: injection speed 0.5ml / h-1.5ml / h, receiving distance 8-12cm, voltage 16-18kv, and roller speed 20-40r / min;

[0047] Preferably, after electrospinning is completed, the precursor is placed in a tube furnace under an inert gas atmosphere at 2-3°C / min. -1 Heating at a rate of 300-350℃ for annealing for 2-4 hours yields iron-carbon micro / nanofibers.

[0048] In an optional embodiment, a cerium source is dissolved in water to obtain a cerium source solution, iron-carbon micro / nanofibers are added to the cerium source solution and ultrasonically dispersed, ammonia is added to convert cerium ions into cerium hydroxide and adsorb them onto the iron-carbon micro / nanofibers, the pH is adjusted to neutral again, and the mixture is continuously stirred to obtain a suspension.

[0049] Preferably, the cerium source is dissolved in deionized water and magnetically stirred for 20-30 min to obtain a cerium source solution. Iron-carbon micro / nano fibers are added to the cerium source solution and ultrasonically dispersed for 20-30 min. Ammonia water is added and magnetically stirred for 4-6 h. The pH is adjusted to neutral with nitric acid and ammonia water, and stirring is continued for 1-2 h to obtain a suspension.

[0050] Preferably, the mass ratio of cerium source to iron-carbon micro / nanofiber is 1-1.5:1;

[0051] More preferably, the cerium source is one or more of cerium nitrate hexahydrate, cerium ammonium nitrate, and cerium sulfate tetrahydrate.

[0052] In an optional embodiment, the hydrothermal treatment temperature of the suspension is 160-200°C, and the time is 2-4 hours;

[0053] Preferably, after the hydrothermal reaction is completed, the reaction solution is naturally cooled to room temperature and separated by vacuum filtration. After being washed and filtered alternately with deionized water and anhydrous ethanol, it is placed in a glass petri dish and dried at 60°C to obtain iron-carbon micro / nanofibers @CeO2.

[0054] Thirdly, embodiments of the present invention provide an application of the above-mentioned heavy metal passivation and stabilization material in the oxidation and / or passivation of heavy metals; preferably, the application in the oxidation and / or passivation of heavy metals in soil and water; preferably, the heavy metal includes any one or more of arsenic, mercury, and lead; more preferably, the heavy metal is arsenic.

[0055] In an optional embodiment, the above-mentioned heavy metal passivation and stabilization material is added to the arsenic-containing solution to be treated. For arsenic-containing solutions with arsenic concentration in the range of 0-10 mg / L, the amount of heavy metal passivation and stabilization material added is 0.3 g / L-1 g / L, and the pH of the arsenic-containing solution is 3-10.

[0056] This invention provides the application of the above-mentioned heavy metal passivation and stabilization materials in the oxidation and / or passivation of heavy metals. The heavy metal passivation and stabilization materials can exert their adsorption effect on heavy metals, especially arsenic, in a wide range of media and pH (3-10). At the same time, they can also exert a good removal effect on arsenic at low dosages. They can be widely used in the treatment of heavy metal pollution, especially arsenic, in various water bodies and soils.

[0057] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0058] Example 1

[0059] Preparation of iron-carbon micro / nanofibers@CeO2 materials

[0060] Polyvinylpyrrolidone (PVP) and polyacrylonitrile (PAN) were used as spinning aids, N,N-dimethylformamide (DMF) as a solvent, and ferric chloride hexahydrate as an iron source. The spinning solution was prepared with PVP and PAN added at 10% Wt in a 1:1 ratio. The spinning solution was loaded into a 10 ml syringe, which was then fixed to the spinning machine. A high-voltage power supply was connected to the stainless steel nozzle. The spun fibers were collected on an aluminum foil. Spinning parameters were set (injection speed 1 ml / h, receiving distance 10 cm, voltage 18 kV, roller speed 30 r / min). After electrospinning, the resulting precursor was placed in a tube furnace and protected with nitrogen gas at 2 °C·min. -1 The temperature was increased to 300℃ at a certain rate and annealed for 3 hours to obtain iron-carbon micro / nanofiber materials.

[0061] Cerium nitrate hexahydrate was dissolved in deionized water and magnetically stirred for 30 min. A certain amount of iron-carbon micro / nanofiber fibers was weighed and added to the solution, with a mass ratio of iron-carbon micro / nanofiber fibers to cerium nitrate hexahydrate of 1:1. The solution was ultrasonically dispersed for 30 min to ensure that cerium ions were fully dispersed on the iron-carbon micro / nanofiber fibers. A certain amount of ammonia water was added, and the solution was magnetically stirred for 4 h. The pH was adjusted to 7 with nitric acid and ammonia water, and mechanical stirring was continued for 2 h. The suspension was transferred to a reaction vessel lined with polytetrafluoroethylene and heat-treated at 180℃ for 2 h. After heat treatment, the solution was allowed to cool naturally to room temperature and then filtered. The solution was washed three times alternately with deionized water and anhydrous ethanol. After filtration, the material was placed in a glass petri dish and dried at 60℃. The dried material was iron-carbon micro / nanofiber fibers@CeO2.

[0062] SEM images of the iron-carbon micro / nanofibers prepared in Example 1 are shown below. Figure 1 As shown in the left-middle image, after high-temperature carbonization, the fibers are composed of stacked iron-carbon nanoparticles, and an uneven structure is formed on the surface of the micro-nanofibers, providing a uniform and abundant number of nucleation sites for the growth of cerium dioxide; the SEM image of the iron-carbon micro-nanofibers@CeO2 prepared in Example 1 is shown below. Figure 1 As shown in the middle right figure, after loading, the fiber surface changed from its original unevenness to smoothness and was completely covered by cerium dioxide, indicating that cerium dioxide was uniformly loaded onto the surface of the iron-carbon micro-nano fibers.

[0063] EDS analysis of the iron-carbon micro / nanofibers @CeO2 prepared in Example 1 yielded the following results: Figure 2 As shown in the figure, in addition to the constituent elements of iron-carbon micro-nanofibers @CeO2 such as C and O, Ce and Fe elements are accumulated on the surface of the material, with Ce content as high as 22.61%, indicating that nano-cerium oxide was successfully loaded onto the surface of iron-carbon micro-nanofibers.

[0064] By analyzing X-ray diffraction patterns, information such as the elemental structure, morphology, and crystallinity of the material was obtained. This paper uses a Bruker D8advance X-ray diffraction (XRD) instrument manufactured in Germany to determine the crystal structure of the sample within the range of 5-90°, under conditions of 40 kV voltage and 40 mA current, and analyzes the composition of the material. Figure 4 In the study, the iron-carbon micro / nanofibers@CeO2 material exhibited four identical characteristic peaks at 28.69°, 33.08°, 47.73°, and 56.59°, corresponding to the (111), (200), (220), and (311) crystal planes, respectively. These observed diffraction peaks are essentially consistent with the typical diffraction peaks of cerium oxide with a fluorite structure (see the XRD image of CeO2). Figure 3 The results show that, through hydrothermal reaction, cerium ions loaded on iron-carbon micro / nanofibers are completely converted into cerium dioxide and uniformly nucleate and grow on the iron-carbon micro / nanofibers.

[0065] Meanwhile, using the data obtained from XRD, the size of CeO2 nanoparticles can be calculated using the Scherrer formula.

[0066]

[0067] In the formula:

[0068] K—Scherrer constant, taken as 0.89;

[0069] D – Grain size;

[0070] β—Measured half-width at half-maximum of the diffraction peak in the sample (double-line correction and instrument factor correction must be performed), which needs to be converted to radians (rad) during the calculation process;

[0071] θ—Bragg diffraction angle;

[0072] γ – wavelength, typically 1.54056.

[0073] Table 1. Calculation of Cerium Dioxide Nanoparticle Size

[0074] K γ 0 COSθ β D 0.89 0.15406 14.35245 0.968789216 0.020839231 6.791550116 0.89 0.15406 23.80675 0.91491212 0.019321493 7.756393586 0.89 0.15406 28.2366 0.881001411 0.018434517 8.442509182

[0075] Calculations using the Scherrer formula show that the particle size of cerium dioxide nanoparticles is between 6 and 9 nm.

[0076] Table 2 Potential table of iron-carbon micro / nanofibers, cerium dioxide, and iron-carbon micro / nanofibers @CeO2Zeta

[0077] Material Zeta potential Iron-carbon micro / nanofibers 4.9 <![CDATA[CeO2]]> 3.8 <![CDATA[Iron-carbon micro-nanofibers @ CeO2]]> 6.1

[0078] As shown in the table above, the iron-carbon micro / nanofiber surface carries a positive charge. According to Coulomb's law, its surface readily combines with negatively charged ions. Due to the addition of ammonia in the preparation system, cerium ions form a cerium dioxide precursor—cerium hydroxide—in the solution. Cerium hydroxide is negatively charged in an alkaline environment, causing the positively charged iron-carbon micro / nanofiber to attract the negatively charged cerium dioxide precursor, resulting in a tight bond and a stable structure. Further hydrothermal reaction uniformly loads cerium dioxide onto the surface of the iron-carbon micro / nanofiber. The @CeO2 potential of the iron-carbon micro / nanofiber is significantly higher than that of the iron-carbon micro / nanofiber. This indicates that the electro-affinity between CeO2 and the iron-carbon micro / nanofiber surface increases the Zeta potential of the iron-carbon micro / nanofiber, thereby promoting the stable bonding and electro-compatibility between the two.

[0079] Example 2

[0080] In the preparation process, the hydrothermal reaction temperature was adjusted to 200℃, and other steps were the same as in Example 1. SEM images of the iron-carbon micro / nanofibers@CeO2 prepared in Example 2 are shown below. Figure 5 It can be seen that the cerium dioxide loaded onto the iron-carbon micro-nanofibers has a larger particle size and a relatively smaller specific surface area, but still maintains a high removal efficiency for arsenic.

[0081] Example 3

[0082] In the preparation process, the mass ratio of iron-carbon micro / nanofibers to cerium nitrate hexahydrate was 1:1.5, and other preparation procedures were the same as in Example 1. The SEM image of the iron-carbon micro / nanofibers@CeO2 prepared in Example 3 is shown below. Figure 6 It can be seen that the cerium dioxide loaded onto the iron-carbon micro-nanofibers is denser and more abundant, which can be used to treat high concentrations of arsenic pollution.

[0083] Comparative Example 1

[0084] Similar to the steps in Example 1, the only difference being that the dosages of PVP and PAN added during the preparation process were 16% and 8%, respectively. SEM images of the iron-carbon micro / nanofibers @CeO2 prepared in Comparative Example 1 with different PVP and PAN dosages are shown below. Figure 7 When the dosage is 16%, the interaction between carbon-iron micro- and nanofibers increases, making them prone to aggregation. When the dosage is 8%, there are fewer polymer molecules in the electrospinning solution, the solution viscosity is lower, and the fiber morphology is less controllable. Therefore, the prepared fibers are thin and isolated, and the connectivity between fibers is poor.

[0085] Comparative Example 2

[0086] Similar to the steps in Example 1, the only difference being that the annealing temperature during calcination was 500°C. SEM images of the iron-carbon micro / nanofibers @CeO2 prepared at different calcination temperatures in Comparative Example 2 are shown below. Figure 8 It can be seen that as the calcination temperature increases, the surface of carbon-iron micro- and nanofibers gradually becomes smooth, the uneven surface disappears, the specific area decreases, and the number of active sites decreases, which is not conducive to loading CeO2 nanoparticles as a substrate material.

[0087] Comparative Example 3

[0088] Similar to the steps in Example 1, the only difference being that the mass ratio of iron-carbon micro / nanofibers to cerium nitrate hexahydrate was 1:2 during the preparation process. SEM images of the iron-carbon micro / nanofibers@CeO2 prepared in Comparative Example 3 are shown below. Figure 9 It can be seen that as the cerium source increases, more cerium dioxide is loaded onto the iron-carbon micro-nanofibers. However, the cerium dioxide does not grow along the iron-carbon micro-nanofibers. A large amount of cerium dioxide blocks the gaps between the iron-carbon micro-nanofibers, destroying the original structure of the iron-carbon micro-nanofibers. Moreover, the cerium dioxide that is not attached to the iron-carbon micro-nanofibers is easy to fall off during the adsorption process, affecting its recycling.

[0089] The iron-carbon micro / nanofibers@CeO2 prepared in Example 1 were used to test their adsorption and passivation effects on heavy metals, especially arsenic.

[0090] Arsenic removal effect of iron-carbon micro / nanofibers@CeO2 materials

[0091] A 10 mg / L arsenic-containing solution was prepared, and iron-carbon micro / nanofibers, CeO2, and iron-carbon micro / nanofibers@CeO2 were added respectively, at a dosage of 0.6 g / L. The arsenic adsorption effects of the three materials were as follows: Figure 10 As shown, without cerium dioxide loading, the adsorption effect of iron-carbon micro-nanofibers on arsenic is poor, with an adsorption rate of only 10%; however, after loading cerium dioxide, its adsorption efficiency for arsenic can reach more than 98%, which is much higher than the adsorption effect of using cerium dioxide and iron-carbon micro-nanofibers alone.

[0092] A 2 mg / L arsenic-containing solution was prepared, and the adsorption efficiency of iron-carbon micro / nanofibers@CeO2 for arsenic was studied at different water body pH values ​​of 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, and 10.0. Figure 11 As shown, iron-carbon micro / nanofibers exhibit poor adsorption efficiency for arsenic over a wide pH range, reaching 31.97% at pH 3, but only 4.92% at pH 10. In contrast, iron-carbon micro / nanofibers@CeO2 demonstrate high removal efficiency for arsenic over a wide pH range, consistently exceeding 98%.

[0093] Solutions containing various heavy metal cations (each metal concentration 2 mg / L) were prepared to investigate the selective adsorption properties of iron-carbon micro / nanofibers and iron-carbon micro / nanofiber@CeO2 materials when several heavy metal cations (mercury, copper, zinc, lead, chromium, cadmium, manganese, nickel, and arsenic) were simultaneously present in the wastewater. Figure 12 It can be seen that the adsorption effect of iron-carbon micro-nanofibers on heavy metal ions other than mercury and chromium is poor, with none exceeding 10%. However, after loading cerium dioxide, the adsorption effect of iron-carbon micro-nanofibers @CeO2 on mercury, lead, arsenic, chromium and copper is significantly improved, with adsorption efficiencies of over 95% for mercury, lead and arsenic. Therefore, this material can treat various heavy metal pollution, especially arsenic, greatly increasing the application range of iron-carbon micro-nanofibers @CeO2 materials.

[0094] With an initial arsenic concentration of 2 mg / L and an addition of 30 mg of iron-carbon micro / nanofiber @CeO2, under pH 6 conditions, 50 mL of an arsenic-containing solution was transferred to a 250 mL Erlenmeyer flask to study the different SO42- anions in the solution. 2- NO3 - Cl - CO3 2- F - The effect of solution on arsenic adsorption performance. Figure 13 It can be seen that in SO4 2- NO3 - Cl - CO3 2- F - When coexisting with arsenic ions, even at high anion concentrations, the arsenic adsorption efficiency remains above 96%. Therefore, it can be concluded that these coexisting anions have almost no effect on the adsorption of arsenic by iron-carbon micro / nanofiber @CeO2.

[0095] Compared to traditional metal oxide arsenic adsorbents, iron-carbon micro / nanofibers@CeO2 exhibit better adsorption performance. For example... Figure 14 As shown, compared with the concave-convex material loaded with manganese dioxide, iron-carbon micro / nanofiber @CeO2 has a higher adsorption capacity, reaching 50 mg / g.

[0096] Loading cerium dioxide onto iron-carbon micro / nanofibers via a hydrothermal reaction offers advantages over traditional metal-doped blends. In contrast, this material is obtained by spinning cerium nitrate as a cerium source in a spinning solution followed by high-temperature calcination. Figure 15 EDS analysis revealed that the relative volume content of Ce on the surface of cerium dioxide nanofibers was only 0.54%. In contrast, the relative volume content of Ce in iron-carbon micro / nanofibers@CeO2 was approximately 3%, about six times that of the former. Figure 16As shown, comparing the arsenic adsorption efficiencies of the two, the adsorption efficiency of iron-carbon micro / nanofiber nanofibers @CeO2 for arsenic is far superior to that of cerium dioxide nanofibers. The adsorption capacity of cerium dioxide nanofibers is only 4.3 mg / g, while that of iron-carbon micro / nanofiber nanofibers @CeO2 is 50 mg / g, which is 11 times that of the former.

[0097] Passivation effect of iron-carbon micro / nanofibers@CeO2

[0098] Soil column leaching experiments were conducted to study the passivation effect of this material on arsenic in soil. The soil column used in this study was made of highly stable and corrosion-resistant PMMA acrylic material, with a height of 170 cm, a cross-sectional diameter of 20 cm, and a cross-sectional area of ​​314 cm³. 2 The base of the earthen column is connected to an iron counterweight to stabilize the column. A permeable plate is located 10cm above the base of the column. In addition to being tightened with screws, the column and base are equipped with a sealing ring to ensure water tightness. The top of the column has a piston rod assembly with graduated markings and a water inlet drilled into the rod. Six water outlet valves are evenly distributed on each side of the column from top to bottom; one side has a copper angle valve, and the other has a plastic spiral valve. A water outlet is located at the center of the column base.

[0099] Soil and iron-carbon micro / nanofibers@CeO2 were mixed and compacted in a column. An arsenic solution with a concentration of 60 μg / L was prepared and water was evenly distributed using a double-layer disc device. Before sampling, the soil column was saturated with tap water, and sampling began periodically after the effluent stabilized. A YZ1515x peristaltic pump was used for water supply in this study. The daily leaching volume was controlled at 500 ml, and the total leaching period was 120 days.

[0100] Depend on Figure 17 It can be seen that the arsenic content in the leaching solution fluctuated greatly in the early stage, but the heavy metal concentration gradually decreased and tended to stabilize as the leaching time increased, with the arsenic content stabilizing below 10 μg / L. This indicates that the iron-carbon micro-nanofibers @CeO2 have a good solidification and stabilization effect on arsenic.

[0101] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. The application of a heavy metal passivation and stabilization material in the oxidation and / or passivation of heavy metals, characterized in that, The heavy metal is arsenic. The preparation method of the heavy metal passivation and stabilization material includes the following steps: mixing a spinning aid, a solvent, and an iron source to obtain a spinning solution; loading the spinning solution into a syringe; preparing a precursor using electrospinning; and then placing the precursor in a tube furnace under an inert gas atmosphere at 2-3°C / min. -1 The temperature was increased to 300-350℃ and annealed for 2-4 hours to obtain iron-carbon micro / nanofibers. The iron-carbon micro / nanofibers were mixed with a cerium source solution, and ammonia was added to convert cerium ions into cerium hydroxide, which was then adsorbed onto the iron-carbon micro / nanofibers. The pH was adjusted and the mixture was continuously stirred to obtain a suspension. The suspension was then subjected to hydrothermal treatment at 160℃-200℃ for 2-4 hours to obtain a heavy metal passivation and stabilization material, wherein: Polyvinylpyrrolidone (PVP) and polyacrylonitrile (PAN) were used as spinning aids, N,N-dimethylformamide (DMF) was used as a solvent, and ferric chloride hexahydrate was used as an iron source to prepare a spinning solution. The dosage of PVP and PAN in the spinning solution was 10wt%-14wt%, and the ratio of PVP to PAN was 0.5-1:

1. The mass ratio of cerium source to iron-carbon micro / nanofiber was 1-1.5:

1. The prepared heavy metal passivation and stabilization material includes iron-carbon micro / nanofibers and CeO2 nanoparticles loaded on the iron-carbon micro / nanofibers. The composition of the heavy metal passivation and stabilization material is iron-carbon micro / nanofibers@CeO2, the particle size of the CeO2 nanoparticles is 6-9 nm, and the diameter of the iron-carbon micro / nanofibers is 100 nm-500 nm.

2. The application according to claim 1, characterized in that, The dosage of ferric chloride hexahydrate is 8wt%-12wt%.

3. The application according to claim 1, characterized in that, The spinning parameters are set as follows: injection speed 0.5ml / h-1.5ml / h, receiving distance 8-12cm, voltage 16-18kv, and roller speed 20-40r / min.

4. The application according to claim 1, characterized in that, The cerium source is dissolved in water to obtain a cerium source solution. The iron-carbon micro / nanofibers are added to the cerium source solution and ultrasonically dispersed. Ammonia is added to convert cerium ions into cerium hydroxide and adsorb them onto the iron-carbon micro / nanofibers. The pH is adjusted to neutral again and the mixture is stirred continuously to obtain a suspension.

5. The application according to claim 4, characterized in that, The cerium source is dissolved in deionized water and magnetically stirred for 20-30 minutes to obtain a cerium source solution. The iron-carbon micro / nanofibers are added to the cerium source solution and ultrasonically dispersed for 20-30 minutes. Ammonia water is added and magnetically stirred for 4-6 hours. The pH is adjusted to neutral with nitric acid and ammonia water, and stirring is continued for 1-2 hours to obtain a suspension.

6. The application according to claim 1, characterized in that, The cerium source is one or more of cerium nitrate hexahydrate, cerium ammonium nitrate, and cerium sulfate tetrahydrate.

7. The application according to claim 1, characterized in that, After the hydrothermal reaction was completed, the reaction solution was naturally cooled to room temperature and separated by vacuum filtration. After washing and filtering with deionized water and anhydrous ethanol alternately, the solution was placed in a glass petri dish and dried at 60°C to obtain iron-carbon micro / nanofibers @CeO2.

8. The application according to claim 1, characterized in that, The application of the heavy metal passivation and stabilization material in the oxidation and / or passivation of heavy metals in soil and water.

9. The application according to claim 1, characterized in that: The method includes the following steps: adding the heavy metal passivation and stabilization material to the arsenic-containing solution to be treated, wherein the arsenic concentration in the arsenic-containing solution is 0-10 mg / L (not 0), the amount of the heavy metal passivation and stabilization material added is 0.3 g / L-1 g / L, and the pH of the arsenic-containing solution is 3-10.

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