An ultra-small particle size MnFe2O4 / rGO nanoelectrode material, its preparation method and application

Abstract

The application discloses an ultra-small particle size MnFe2O4 / rGO nano electrode material and a preparation method and application thereof, relates to the deep treatment technical field of removing phosphorus, arsenic and antimony in water bodies, and discloses that the ultra-small particle size MnFe2O4 nanocrystals are precisely anchored on a multistage-pore, high-conductivity and defect-rich rGO carrier through a one-pot method, and a highly-dispersed MnFe2O4 / rGO multi-element superstructure nano composite electrode is obtained. The MnFe2O4 / rGO multi-element superstructure nano composite electrode is configured into an asymmetric MnFe2O4 / rGO / / AC-COOH electrode configuration, and the efficient, green, stable, sustainable and deep removal of arsenic in underground water can be realized, so that the application prospect of the MnFe2O4 / rGO multi-element superstructure nano composite electrode is good in the fields of removal of arsenic in actual underground water bodies and water purification capacity. In addition, the potential application range of the asymmetric MnFe2O4 / rGO / / AC-COOH electrochemical system can be further extended to the environmental remediation of other elements, such as phosphorus and antimony, and the asymmetric electrode system has high universality, and the practical application potential of the asymmetric electrode system is further widened.

Description

Technical Field

[0001] This invention relates to the field of efficient and in-depth treatment technology of arsenic in groundwater, specifically to an ultra-small particle size MnFe2O4 / rGO nanoelectrode material and its preparation method, and its application in the electrochemical removal of phosphorus, arsenic and antimony from water. Background Technology

[0002] Arsenic is listed by the World Health Organization (WHO) as one of the top ten environmental pollutants that can cause major public health emergencies, posing a serious threat to human health and the ecological environment. To reduce the impact of arsenic pollution on human health, the WHO has set the threshold for arsenic concentration in drinking water at 10 μg / L. -1 High-arsenic groundwater is typically found in arid / semi-arid rural and remote areas. Due to inadequate water treatment facilities, there is an urgent need to develop simple, efficient, stable, and deep arsenic removal technologies suitable for the characteristics of these areas.

[0003] In recent years, electrochemical arsenic removal technology has become a promising field due to its low energy consumption, lack of chemical additives during electrode regeneration, simple operation, recyclability, and environmental friendliness. Electrode structure is a key factor directly determining the overall performance of the electrochemical system. Carbon-based materials are widely used as electrode materials due to their low cost, large specific surface area, high conductivity, and stability; however, their strong common ion repulsion and overlap effects typically result in a saturated adsorption capacity below 10 mg / g. -1 The processing depth is difficult to reach the World Health Organization's standard of <10 μg·L⁻¹. -1 Standards. Furthermore, the non-specific adsorption of carbon electrodes results in poor electrode selectivity, significantly limiting arsenic removal performance. Transition metal materials are considered a good alternative for specific adsorption of arsenic, with iron and manganese being prime examples. Iron, manganese, and their composite anode materials can achieve arsenic adsorption capacities of tens of milligrams per gram. However, transition metal oxide particles are still relatively large, with poor interparticle dispersion; carbon supports lack sufficient pore structure; and the composite effect between metal oxides and carbon-based supports is poor. These structural defects lead to increased internal resistance and reduced intrinsic pseudocapacitance, resulting in iron / manganese-based and their composite electrodes often exhibiting slow arsenic adsorption kinetics, poor recyclability and instability, requiring NaOH assistance for regeneration, and low capacitance contribution. Moreover, the harsh operating conditions limit their practical application potential. This highlights a key gap in the field: the focus has been on improving specific aspects of performance rather than overall performance, widening the gap between theoretical exploration and practical application, and hindering the widespread implementation of this technology. Therefore, in order to comprehensively improve the adsorption capacity, processing speed, selectivity, processing depth and cycle stability of electrochemical arsenic removal, and to narrow the gap between laboratory-scale research and actual environmental applications, the innovative structural design of electrode materials is crucial. Summary of the Invention

[0004] To address the shortcomings of the aforementioned technologies, the present invention aims to provide an ultra-small particle size MnFe₂O₄ / rGO nanoelectrode material, its preparation method, and its applications. Ultra-small particle size MnFe₂O₄ nanocrystals are precisely anchored onto a hierarchical porous, highly conductive, and defect-rich rGO support using a one-pot method, resulting in a highly dispersed MnFe₂O₄ / rGO multi-element superstructured nanocomposite electrode. Constructing this electrode into an asymmetric MnFe₂O₄ / rGO / / AC-COOH electrode configuration enables efficient, green, stable, sustainable, and deep removal of arsenic from groundwater, showing promising application prospects in the field of arsenic removal from actual groundwater bodies.

[0005] The technical objective of this invention is achieved through the following technical solution:

[0006] A method for preparing ultra-small particle size MnFe2O4 / rGO nanoelectrode materials, characterized by the following specific steps:

[0007] Step 1: Preparation of hierarchical porous, wrinkled rGO

[0008] Disperse a 0.5–2.5 mg / L GO aqueous solution in a container of 50–150 mL deionized water and sonicate for 10–45 min; then add 0.075–0.18 g ascorbic acid and sonicate again for 10–45 min; place the container in an oil bath and mechanically stir and react for 1–3 h at 70–100 °C. After the solution cools to room temperature, wash with water and freeze-dry to obtain the target product rGO; the mass concentration of rGO is in the range of 0.5–1.5 mg / L.

[0009] Step 2: Preparation of MnFe2O4 / rGO nanoelectrode materials

[0010] 0.25–0.75 g of rGO obtained in step 1 was ultrasonically dispersed for 10–45 min to obtain 200 mL of highly dispersed aqueous solution. Then, FeCl3·6H2O and MnSO4·H2O were weighed and dissolved in the highly dispersed solution. The solution was stirred and reacted continuously in an oil bath at 65–95 °C for 2–8 h. Subsequently, the pH of the solution was adjusted to 9.5–11.5 by using a hot NaOH solution with a concentration of 2–4 M and a temperature of 65–95 °C. The reaction was continued for 10–30 min. After the reaction was completed, the solution was washed with water and freeze-dried to obtain the ultra-small particle size MnFe2O4 / rGO nanoelectrode material. The molar amount of FeCl3·6H2O was 2.1–6.3 mM, the molar amount of MnSO4·H2O was 1.05–3.15 mM, and the molar ratio of FeCl3·6H2O to MnSO4·H2O was 2:1.

[0011] An ultra-small particle size MnFe2O4 / rGO nanoelectrode material prepared by the above method.

[0012] An application of the aforementioned nanoelectrode material in the treatment of arsenic pollutants in groundwater, specifically including:

[0013] Step 1: Constructing the asymmetric electrochemical system MnFe2O4 / rGO-AEM / / CEM-AC-COOH

[0014] Take a pair of square PMMA (polymethyl methacrylate) shells, 8 x 8 cm. 2 The device consists of a pair of silicone gaskets, a silicone separator gasket, 0.1mm thick nonwoven fabric, and a pair of large-size titanium metal plate current collectors with an active area of ​​5x5cm. 2 The anode is MnFe2O4 / rGO as the working electrode, and the cathode is AC-COOH as the counter electrode. Anion exchange membrane (AEM) and cation exchange membrane (CEM) are installed on one side of the working electrode and the counter electrode, respectively, with a plate spacing of 0.5 mm.

[0015] Step 2: Arsenic contaminants in groundwater flow from bottom to top through the asymmetric electrochemical system constructed in Step 1 using a peristaltic pump. A potentiostat provides a constant adsorption and desorption voltage for this electrochemical system. The concentration of arsenic contaminants in the groundwater is 1–10 mg / L, the volume is 50–1000 mL, the total electrode coating amount is 30–90 mg, and the peristaltic pump flow rate is 2–50 mL / min. -1 The adsorption voltage is 0.8–1.8V; the adsorption time is 1–5h, and the adsorption efficiency is 60–100%; the desorption voltage is 1.0–2.0V; the desorption time is 0.5–2.0h, and the desorption efficiency is 80%–100%.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] 1) The raw materials for preparing the electrode materials of the present invention are abundant, inexpensive and readily available; small-particle-size, highly dispersed nano-electrode materials can be synthesized in one step.

[0018] 2) The prepared ultra-small particle size MnFe2O4 / rGO nanoelectrode material has a relatively large specific surface area and abundant pore structure, which exposes more electroadsorption active sites and enhances charge storage and mass transfer.

[0019] 3) This asymmetric MnFe2O4 / rGO / / AC-COOH electrochemical arsenic removal system is simple to operate and economical to set up. Furthermore, it features high electrode regeneration efficiency, no secondary pollution, and can achieve continuous purification of arsenic-containing groundwater.

[0020] 4) The potential applications of this asymmetric MnFe2O4 / rGO / / AC-COOH electrochemical system can be extended to the environmental remediation of other elements in the same group, demonstrating high versatility.

[0021] 5) This asymmetric MnFe2O4 / rGO / / AC-COOH electrochemical system enhances the purification capacity of arsenic-containing groundwater and further expands its potential for practical application. Attached Figure Description

[0022] Figure 1 X-ray powder diffraction patterns of the ultra-small particle size MnFe2O4 / rGO nanoelectrode and rGO prepared in Example 1 of this invention;

[0023] Figure 2 Transmission electron microscope image of multi-level porous, wrinkled rGO prepared in Example 1 of the present invention;

[0024] Figure 3 This is a high-resolution transmission electron microscope image of the ultra-small particle size MnFe2O4 / rGO nanoelectrode prepared in Example 1 of the present invention;

[0025] Figure 4 The ultra-small particle size MnFe2O4 / rGO nanoelectrode prepared in Example 1 of this invention has a lower particle size than that prepared by MnFe2O4 and rGO with a scan rate of 20 mV·s. -1 The cyclic voltammetry curve below;

[0026] Figure 5 The nitrogen adsorption-desorption curve of the ultra-small particle size MnFe2O4 / rGO nanoelectrode prepared in Example 1 of this invention;

[0027] Figure 6 The pore size distribution diagram of the ultra-small particle size MnFe2O4 / rGO nanoelectrode prepared in Example 1 of the present invention;

[0028] Figure 7 This is a schematic diagram illustrating the deep removal performance of the ultra-small particle size MnFe2O4 / rGO nanoelectrode prepared in Example 1 of the present invention in an asymmetric MnFe2O4 / rGO / / AC-COOH electrochemical system for groundwater with different arsenic concentrations of 0.1–1 mg / L.

[0029] Figure 8 This is a schematic diagram of the stability of the ultra-small particle size MnFe2O4 / rGO nanoelectrode prepared in Example 1 of the present invention in the asymmetric MnFe2O4 / rGO / / AC-COOH electrochemical system for 50 cycles of adsorption-desorption of 10 mg / L As(V) in pure water, tap water and groundwater (adsorption 2h-desorption 1h).

[0030] Figure 9A schematic diagram of the deep removal performance of the ultra-small particle size MnFe2O4 / rGO nanoelectrode prepared in Example 1 of the present invention in a 5L volume of groundwater with a concentration of 1mg / L in an asymmetric MnFe2O4 / rGO / / AC-COOH electrochemical system.

[0031] Figure 10 The diagram illustrates the removal performance of the ultra-small particle size MnFe2O4 / rGO nanoelectrode prepared in Example 1 of this invention on different concentrations of P(V), As(III), and Sb(III / V) in the asymmetric MnFe2O4 / rGO / / AC-COOH electrochemical system. Detailed Implementation

[0032] To better illustrate the technical objectives, technical parameters, and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. The present invention includes, but is not limited to, the following embodiments.

[0033] This invention provides an ultra-small particle size MnFe₂O₄ / rGO nanoelectrode material, prepared by the following method: A certain mass of 0.25–0.75 g of hierarchical porous, wrinkled rGO was prepared in a round-bottom flask containing 200 mL of deionized water and ultrasonically dispersed for 60 min to obtain a highly dispersed solution. Then, FeCl₃·6H₂O and MnSO₄·H₂O in different molar ratios were weighed and dissolved in the above solution. The mixture was stirred at a certain temperature in an oil bath and reacted continuously for several hours. Subsequently, the pH of the mixed solution was adjusted by controlling the concentration of NaOH and the temperature, and the reaction was continued for 15 min. After the reaction was completed, the mixture was washed with water and freeze-dried to obtain the final product.

[0034] Preferably, the specific steps for preparing the hierarchical porous, wrinkled rGO according to the present invention are as follows: A 1 mg / L GO aqueous solution is dispersed in a 90 mL deionized water round-bottom flask and sonicated for 30 min; then 0.075–0.18 g of ascorbic acid is added and sonicated again for 30 min. The round-bottom flask is placed in an oil bath and mechanically stirred at 70–100 °C for 1–3 h. After the solution cools to room temperature, it is washed with water and freeze-dried to obtain the target product rGO.

[0035] Furthermore, the molar amount of FeCl3·6H2O in this invention is 2.1–6.3 mM; the molar amount of MnSO4·H2O is 1.05–3.15 mM, wherein the molar ratio of FeCl3·6H2O to MnSO4·H2O is maintained at 1:2.

[0036] Furthermore, the oil bath of the present invention is maintained at a temperature of 65–95°C, stirred, and reacted continuously for 2–8 hours. Subsequently, a hot NaOH solution with a concentration of 2–4M and a temperature of 65–95°C is used to adjust the pH of the above mixed solution to 9.5–11.5.

[0037] Another technical objective of this invention is to provide an application of ultra-small particle size MnFe2O4 / rGO nanoelectrode material for arsenic removal in groundwater. Currently, in actual groundwater conditions, selective and deep removal of 0.1–10 mg / L As(V) can be achieved in 100 mL of water. Simultaneously, the potential application of this electrochemical system can be extended to the deep removal of phosphorus and antimony, among other elements in the same group. Furthermore, to further broaden the practical purification effect of this technology on arsenic-containing groundwater, a 5 L solution with a concentration of 1.0 mg·L⁻¹ was tested. -1 The As(V) solution can still achieve continuous and deep arsenic removal.

[0038] I. Preparation of Electrode Materials

[0039] Example 1

[0040] Preparation of hierarchical, wrinkled rGO: A 1 mg / L GO aqueous solution was dispersed in a 90 mL deionized water round-bottom flask and sonicated for 30 min; then 0.15 g ascorbic acid was added and sonicated for another 30 min. The round-bottom flask was placed in an oil bath and mechanically stirred at 85 °C for 1.5 h. After the solution cooled to room temperature, it was washed with water and freeze-dried to obtain the target product rGO.

[0041] Preparation of ultra-small particle size MnFe₂O₄ / rGO nanoelectrodes: 0.5 g of the prepared hierarchical, wrinkled rGO was prepared in a round-bottom flask containing 200 mL of deionized water and ultrasonically dispersed for 60 min to obtain a highly dispersed solution. Then, 4.2 mM FeCl₃·6H₂O and 2.1 mM MnSO₄·H₂O were weighed and dissolved in the above solution. The mixture was stirred in an oil bath at 80 °C for 25 hours. Subsequently, the pH of the mixed solution was adjusted to 9.5–11.5 using 4 M NaOH at 65–90 °C, and the reaction was continued for 15 min. After the reaction was completed, the mixture was washed with water and freeze-dried to obtain the ultra-small particle size MnFe₂O₄ / rGO.

[0042] The X-ray powder diffraction patterns of the above rGO and MnFe2O4 / rGO nanoelectrode materials are as follows: Figure 1 As shown, the phases of both are highly consistent with the standard spectrum. Figure 2 Transmission electron microscopy images confirmed that the synthesized rGO was hierarchically porous and wrinkled. Figure 3 High-resolution transmission electron microscopy images confirm that MnFe2O4 / rGO is a highly dispersed, ultra-small particle size nanoelectrode material with a particle size of approximately 9 nm. Figure 4 Cyclic voltammetry curves confirmed that the ultra-small particle size MnFe2O4 / rGO nanoelectrode possesses excellent electrochemical activity. Figure 5The nitrogen adsorption-desorption curve and pore size distribution of the ultra-small particle size MnFe2O4 / rGO nanoelectrode prepared in Example 1 of this invention are shown. Figure 6 The image shows the pore size distribution of the ultra-small particle size MnFe2O4 / rGO nanoelectrode prepared in Example 1 of this invention, which further confirms that the MnFe2O4 / rGO nanoelectrode has a relatively large specific surface area and abundant pore structure.

[0043] II. Performance Testing

[0044] Example 2

[0045] The ultra-small particle size MnFe2O4 / rGO nanoelectrode prepared in Example 1 was combined with AC-COOH to form an asymmetric MnFe2O4 / rGO / / AC-COOH electrochemical arsenic removal system. The total electrode coating amount was 50 mg; the peristaltic pump flow rate was 30 mL·min. -1 The depth removal performance of 100 mL of actual groundwater with a concentration of 0.1-1.0 mg / L was evaluated under the conditions of adsorption voltage 0-1.5 V and adsorption time 2 h. The test indicators for different water bodies are shown in Table 1. Figure 7 As shown, this asymmetric electrode system exhibits excellent deep removal performance for arsenic-containing groundwater with different low concentration gradients, and the effluent is far below the WHO drinking water threshold standard of 10 μg / L.

[0046] Example 3

[0047] The ultra-small particle size MnFe2O4 / rGO nanoelectrode prepared in Example 1 was combined with AC-COOH to construct an asymmetric MnFe2O4 / rGO / / AC-COOH electrochemical arsenic removal system. The experimental conditions were changed to test the stability of this asymmetric electrode system for adsorption-desorption cycles of 50 times (adsorption 2h-desorption 1h) of 10 mg / L As(V) in pure water, tap water, and groundwater. Other electrochemical adsorption conditions were the same as in Example 2. Figure 8 As shown, the asymmetric electrode system exhibits good cyclic stability for arsenic removal in the three types of water bodies during the first 20 cycles, and can still maintain nearly 40% of the adsorption capacity even after 50 cycles.

[0048] Example 4

[0049] The ultra-small particle size MnFe₂O₄ / rGO nanoelectrode prepared in Example 1 was combined with AC-COOH to construct an asymmetric MnFe₂O₄ / rGO / / AC-COOH electrochemical arsenic removal system. The experimental conditions were changed to investigate the depth removal performance and purification capacity of this asymmetric electrode system in 5 L of groundwater with a concentration of 1 mg / L; other electrochemical adsorption conditions were the same as in Example 2. Figure 9As shown, the system reduced the arsenic content of groundwater containing 5L, 1.0mg / L As(V) to below the AFS (atomic fluorescence spectroscopy) detection threshold of 0.3μg / L within a 58-hour timeframe, demonstrating its outstanding ability for continuous and deep purification.

[0050] Example 5

[0051] The ultra-small particle size MnFe₂O₄ / rGO nanoelectrode prepared in Example 1 was combined with AC-COOH to construct an asymmetric MnFe₂O₄ / rGO / / AC-COOH electrochemical arsenic removal system. The experimental conditions were changed to test the removal performance of this asymmetric electrode system for different concentrations of P(V), As(III), and Sb(III / V) from the same group; other electrochemical adsorption conditions were the same as in Example 2. Figure 10 As shown, this electrode system exhibits excellent removal performance for P(V) and Sb(III / V) in the same group, as well as a catalytic depollution effect on As(III). This demonstrates that the potential application scope of this asymmetric system can be extended to the environmental remediation of other elements in the same group, showing high universality and further broadening the potential for practical applications.

[0052] Table 1. Overview of Water Testing Indicators

[0053]

[0054] Composition and properties (mg / L) of the actual water matrix.

[0055] TOC: Total Organic Carbon.

[0056] In addition to the embodiments described above, the technical solutions of the present invention can also be implemented in other ways. Furthermore, although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention, and such modifications or substitutions are all within the protection scope of the present invention.

Claims

1. Use of an ultra-small particle size MnFe2O4 / rGO nano-electrode material, characterized in that, The preparation of the MnFe2O4 / rGO nanoelectrode material includes the following specific steps: Step A1: Preparation of hierarchical porous, corrugated rGO Take a mass concentration of 0.5-2.5 mg / L GO aqueous solution and disperse it in a container of 50-150 mL deionized water, and ultrasonic for 10-45 min; then add 0.075-0.18 g ascorbic acid and ultrasonic for 10-45 min; place the container in an oil bath pot, mechanically stir and react at a temperature of 70-100 ℃ for 1-3 h, and after the solution is cooled to room temperature, wash with water, freeze-dry to obtain the target product rGO; the mass concentration of rGO is in the range of 0.5-1.5 mg / L; Step A2: Preparation of MnFe2O4 / rGO nanoelectrode material Take 0.25-0.75 g of rGO obtained in step A1 and ultrasonic disperse for 10-45 min to obtain a highly dispersed aqueous solution of 200 mL; then weigh FeCl3·6H2O and MnSO4·H2O and dissolve them in the highly dispersed aqueous solution, keep the oil bath pot at 65-95 ℃, stir and continue to react for 2-8 h; then control the concentration of hot NaOH solution at 2-4 M and 65-95 ℃ to adjust the solution pH to 9.5-11.5; continue to react for 10-30 min; after the reaction is completed, wash with water and freeze-dry to obtain the ultra-small particle size MnFe2O4 / rGO nanoelectrode material; wherein FeCl3·6H2O is 2.1-6.3 mM; MnSO4·H2O is 1.05-3.15 mM; the molar ratio of FeCl3·6H2O to MnSO4·H2O is 2:1; The application of the prepared ultra-small particle size MnFe2O4 / rGO nanoelectrode material in the treatment of arsenic pollution in groundwater, Specifically includes: Step B1: Construction of asymmetric electrochemical system MnFe2O4 / rGO-AEM / / CEM-AC-COOH A pair of square plexiglass housings 8 x 8 cm 2 A pair of silica gel gaskets, silica gel spacer gaskets, 0.1 mm thick non-woven fabric, a pair of large size, i.e. 5 x 5 cm 2 Titanium metal plate current collector; anode MnFe2O4 / rGO as working electrode, cathode AC-COOH as counter electrode, anion exchange membrane and cation exchange membrane are respectively installed on one side of working electrode and counter electrode, and the distance between the electrodes is 0.5 mm; Step B2: the arsenic pollutants in groundwater flow from bottom to top through the asymmetric electrochemical system constructed in step B1 by using a peristaltic pump, and a constant potential instrument provides a constant adsorption / desorption voltage for the electrochemical system; wherein the concentration of arsenic pollutants in groundwater is 1-10 mg / L, the volume is 50-1000 mL, and the total amount of electrode coating is 30-90 mg; the flow rate of the peristaltic pump is 2-50 mL·min -1 , the adsorption voltage is 0.8-1.8 V; the adsorption time is 1-5 h, and the adsorption efficiency is 60-100%; the desorption voltage is 1.0-2.0 V; the desorption time is 0.5-2.0 h, and the desorption efficiency is 80%-100%.

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