A method for removing arsenic in water by using a natural polyphenol to mediate a pyrite-persulfate system

Abstract

The present application belongs to the technical field of arsenic-containing wastewater treatment, and particularly relates to a method for removing arsenic in water by using a natural polyphenol-mediated pyrite-sulfate system. The method mixes an As(III)-containing water body with a natural polyphenol, pyrite, Fe(II) salt and persulfate for reaction, promotes the Fe(III) / Fe(II) cycle at the interface of the pyrite by using the chelation-reduction characteristics of the polyphenol, rapidly activates the persulfate to generate free radicals, and removes As(III) by the synergistic effect of the oxidation to generate Fe2O3 flocs and the adsorption of the pyrite. The removal rate of As(III) is as high as 99.4% within 10 minutes of the mixed reaction. The method provided by the present application has the advantages of fast reaction speed and no secondary pollution, and is suitable for the treatment of arsenic-containing wastewater.

Description

Technical Field

[0001] This invention belongs to the field of arsenic-containing wastewater treatment technology, specifically relating to a method for removing arsenic from water using a natural polyphenol-mediated pyrite-persulfate system. Background Technology

[0002] Arsenic is a toxic and harmful element, widely found in water and soil in nature. Arsenic in water exists primarily in two forms: trivalent and pentavalent arsenic. Trivalent arsenic is more toxic and more difficult to remove from water. Long-term consumption of arsenic-contaminated water can lead to skin lesions, organ damage, and even cancer. Therefore, countries worldwide have strict limits on the arsenic content in drinking water. Currently, commonly used arsenic removal methods include adsorption, precipitation, and membrane separation. However, these methods are either inefficient, expensive, or prone to secondary pollution, making them unsuitable for practical applications.

[0003] Ferrous-activated persulfate advanced oxidation technology is one of the methods for the deep treatment of trace and persistent organic pollutants in water, characterized by its simple operation and rapid process. This technology uses persulfate as an oxidant to generate SO4. - ·、·OH、O2 - ·and 1 O2 and other reactive oxygen species can oxidize and degrade pollutants. However, this method has a key problem: Fe(II) is quickly oxidized to Fe(III) during the reaction, and Fe(III) is difficult to further activate persulfate, leading to a rapid decline in reaction efficiency. To solve this problem, researchers have tried adding reducing agents such as hydroxylamine and ascorbic acid to reduce Fe(III) back to Fe(II), but these chemical reducing agents are used in large quantities, expensive, and may cause secondary pollution. Pyrite is a natural iron-bearing mineral that is inexpensive and can replace chemical iron salts for activating persulfate, while also adsorbing some arsenic. However, when pyrite is used alone, the iron ion recycling efficiency is low, the oxidation rate is slow, and the arsenic removal effect is not ideal. Summary of the Invention

[0004] To address the aforementioned issues, this invention provides a method for removing arsenic from water using a natural polyphenol-mediated pyrite-persulfate system. Through a system of "natural polyphenol-ferrous ion synergistic enhancement of pyrite," rapid oxidation, efficient adsorption, and green fixation of trivalent arsenic are achieved, with an As(III) removal rate of up to 99.4% within 10 minutes.

[0005] To achieve the above objectives, the specific technical solution of the present invention is as follows: The first aspect of this invention provides a method for removing arsenic from water using a natural polyphenol-mediated pyrite-persulfate system, comprising the following steps: The water containing trivalent arsenic is mixed with natural polyphenols, pyrite, ferrous salts and persulfate to react, so that the trivalent arsenic is oxidized to pentavalent arsenic. The pentavalent arsenic is then adsorbed and fixed, thus removing arsenic from the water. The natural polyphenol is at least one of epigallocatechin gallate, gallic acid, tea polyphenols, proanthocyanidins, or luteolin.

[0006] Furthermore, in the reaction system, the concentration of natural polyphenols is 0.01mM~0.1mM, the dosage of pyrite is 0.1g / L~1g / L, the concentration of ferrous salt is 0.05mM~0.2mM, and the concentration of persulfate is 0.1mM~1mM.

[0007] Furthermore, the natural polyphenol is epigallocatechin gallate, with a concentration of 0.01 mM to 0.1 mM.

[0008] Epigallocatechin gallate contains six ortho- and para-phenolic hydroxyl groups. These hydroxyl groups accelerate the Fe(III) / Fe(II) cycle by promoting electron shuttle, thereby enhancing PS activation and free radical generation. Mechanistically, epigallocatechin gallate is oxidized to quinones through a series of single-electron transfer steps, forming highly reactive semiquinone radicals (SQ·), which further enhance the oxidative transformation process.

[0009] Furthermore, the ferrous salt is ferrous sulfate or ferrous chloride, with a concentration of 0.05 mM to 0.1 mM.

[0010] Furthermore, the persulfate is sodium persulfate, potassium persulfate, or ammonium persulfate.

[0011] Furthermore, the reaction time is 2 min to 10 min, and the reaction temperature is 24℃ to 26℃.

[0012] During the reaction, ferrite flocs are generated in situ. These ferrite flocs form a bidentate binuclear or monodentate monouclear coordination structure with pentavalent arsenic, thereby achieving the adsorption and fixation of arsenic.

[0013] Furthermore, the water containing trivalent arsenic is acidic mine drainage, arsenic-containing groundwater, or metallurgical industrial wastewater.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a method for removing arsenic from water using a natural polyphenol-mediated pyrite-persulfate system. The method involves mixing and reacting As(III)-containing water with natural polyphenols, pyrite, Fe(II) salts, and persulfate. The chelation-reduction properties of polyphenols promote the Fe(III) / Fe(II) cycle at the pyrite interface, rapidly activating persulfate to generate free radicals. As(III) is then removed synergistically through the oxidation to form Fe2O3 flocs and the adsorption of pyrite. The specific removal mechanism is as follows: coexisting ferrous ions and Fe(II) leached from pyrite itself promote the activation of polyphenols (PS) to generate reactive oxygen species (ROS) ·OH and SO42-. - • O2 produced by the reduction of Fe(II) by oxygen in the air - • By rapidly activating S2O8 2- Generate SO4 - Simultaneously, Fe(II) is oxidized to Fe(III), while Fe(III) is relatively difficult to activate PS. However, natural polyphenols, through chelation reduction of Fe(III), can increase the rate of Fe(III) to Fe(II) conversion, thereby enhancing the activity and availability of Fe(II) and strengthening PS activation to generate more reactive oxygen free radicals. Pyrite surface S 2- S2 2- and S n 2- Low-valence sulfur species with strong reducing properties can promote the reduction of Fe(III), achieve Fe(II) cycle regeneration, and enhance the continuous activation of PS in the system. In the heterogeneous Fenton system, the generated active free radicals ·OH and SO42- with strong oxidation potentials... - · and O2 - • It rapidly oxidizes As(III) into As(V), which is less toxic and easier to fix. The iron aggregates produced by the complexation reaction between pyrite and phenolic hydroxyl groups and Fe(III) can serve as a good adsorption and precipitation carrier for As(V), thereby efficiently removing As(III) from water.

[0015] This invention achieves rapid oxidation, efficient adsorption, and green fixation of trivalent arsenic through a system of "natural polyphenols-ferrous ions synergistic enhancement of pyrite". It solves the technical bottlenecks of slow reaction rate and unsustainable iron source in the prior art, and provides a low-cost, easy-to-operate, and environmentally friendly solution for the treatment of arsenic-containing wastewater. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 Statistics on the removal efficiency of As(III) in natural polyphenol-mediated oxidation systems; Figure 1 In the figure, (a) represents the removal efficiency of As(III) in different natural polyphenol-mediated oxidation systems; Figure 1 (b) shows the concentration changes of epigallocatechin gallate, Fe(II) and Fe(III) in the FeS2 / Fe(II) / persulfate system fortified with epigallocatechin gallate.

[0018] Figure 2 The impact of various environmental factors on As(III) removal efficiency; Figure 2 The environmental factors corresponding to (a), (b), (c), and (d) in the table are persulfate, Fe(II), epigallocatechin gallate, and coexisting anions, respectively.

[0019] Figure 3 The effects of tert-butanol and methanol on the oxidative removal of As(III); Figure 3 (a) in the figure represents the statistical effect of different concentrations of tert-butanol on the oxidative removal of As(III); Figure 3 (b) in the figure shows the statistical effect of different concentrations of methanol on the oxidation and removal of As(III).

[0020] Figure 4 To detect characteristic active substances using DMPO as an optical scavenger, electron paramagnetic resonance technology was employed. Figure 4 (a) in the text represents DMPO-OH and DMPO-SO4. - The electron paramagnetic resonance spectral analysis spectrum; Figure 4 (b) in the text represents DMPO-O2. .- The spectrum obtained from electron paramagnetic resonance spectroscopy analysis.

[0021] Figure 5 The effect of dissolved oxygen on the removal efficiency of As(III) is investigated.

[0022] Figure 6 Scanning electron microscope and X-ray energy dispersive spectroscopy images of pyrite; Figure 6 Image (a) in the image is a scanning electron microscope image of pyrite before the reaction. Figure 6 (c) in the image is the X-ray energy spectrum of pyrite before the reaction; Figure 6 (b) in the image is a scanning electron microscope image of pyrite after the reaction; Figure 6 (d) in the image is the X-ray energy spectrum of pyrite after the reaction.

[0023] Figure 7The X-ray photoelectron spectra of S2p, Fe2p, and As3d in pyrite before and after the reaction are used to analyze the changes in the chemical states of sulfur, iron, and arsenic during the reaction. Figure 7 In the figure, 'a' represents the XPS spectra of S2p of pyrite before and after the reaction. The top figure shows the XPS spectra of S2p before the reaction, the middle figure shows the XPS spectra of S2p of the recovered materials after the reaction, namely pyrite and iron flocs, and the bottom figure shows the XPS spectra of S2p of the recovered pyrite after the reaction. Figure 7 In the figure, b represents the XPS spectrum of Fe2p. The top figure shows the XPS spectrum of Fe2p before the reaction, the middle figure shows the XPS spectrum of Fe2p of the recovered materials after the reaction, namely pyrite and iron flocs, and the bottom figure shows the XPS spectrum of Fe2p of the recovered pyrite after the reaction. Figure 7 In the figure, c represents the XPS spectrum of As3d. The top figure shows the XPS spectrum of As3d before the reaction, the middle figure shows the XPS spectrum of As3d in the recovered materials after the reaction, namely pyrite and iron flocs, and the bottom figure shows the XPS spectrum of As3d in the recovered pyrite after the reaction.

[0024] Figure 8 This is a schematic diagram showing the oxidation and adsorption capabilities of FeS2 and Fe2O3 for As(III).

[0025] Figure 9 A schematic diagram of the oxidation and adsorption mechanism of As(III) in the FeS2 / Fe(II) / PS system promoted by EGCG. Detailed Implementation

[0026] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods, and the materials and reagents used in the following embodiments are commercially available unless otherwise specified.

[0027] The list of abbreviations for this invention is shown in Table 1.

[0028] Table 1. List of Abbreviations Example 1: Comparison of As(III) removal efficiency in different natural polyphenol-mediated systems Solutions containing 25 μM gallic acid, tea polyphenols, proanthocyanidins, luteolin, and epigallocatechin gallate were prepared separately and mixed with 0.1 mM Fe(II), 0.1 g / L FeS2, and 0.2 mM PS, respectively. These solutions were then added to 300 mL of a 1 mg / L As(III) solution. The experiment was conducted at 25 °C with mechanical stirring at 200 rpm. Three parallel samples were set up, and samples were taken at 0 min, 1 min, 2 min, 4 min, 6 min, 8 min, and 10 min of reaction to investigate the effect of different natural polyphenols on the As(III) removal efficiency in the FeS2 / Fe(II) / PS system.

[0029] Table 2. Basic characteristics of typical natural polyphenols and their removal efficiency for As(III) The results are as follows Figure 1 As shown, within a 10-minute reaction time, the removal efficiencies of trivalent arsenic in the systems mediated by epigallocatechin gallate, tea polyphenols, proanthocyanidins, luteolin, and gallic acid were 89.3%, 74.7%, 72.6%, 63.7%, and 63.5%, respectively. Epigallocatechin gallate showed significantly higher removal efficiency than other natural polyphenols, making it the most effective promoter for removing trivalent arsenic. This significant improvement highlights the role of the natural polyphenol structure in the electron transfer process and As(III) oxidation adsorption efficiency in the FeS2 / Fe(II) / PS system.

[0030] Among natural polyphenols, EGCG exhibits high As(III) oxidation adsorption efficiency due to its unique molecular structure. Unlike other polyphenols, as shown in Table 2, EGCG contains six ortho- and para-phenolic hydroxyl groups, significantly enhancing its redox activity. These ortho- and para-phenolic hydroxyl groups accelerate the Fe(III) / Fe(II) cycle by promoting electron shuttle, thereby enhancing PS activation and free radical generation. Mechanistically, EGCG is oxidized to quinones through a series of single-electron transfer steps, forming highly reactive semiquinone radicals (SQ·), further strengthening the oxidative transformation process.

[0031] Example 2: The Influence of Various Environmental Factors on As(III) Removal Efficiency 1. Effect of PS concentration Under the conditions of Fe(II) concentration of 0.1 mM, FeS2 concentration of 0.1 g / L, initial As(III) concentration of 1 mg / L, and EGCG concentration of 25 μM, the effect of PS concentration in the range of 0.1 mM to 1 mM on the efficiency of As(III) removal mediated by EGCG in the FeS2 / Fe(II) / PS system was investigated. The experiment was conducted at 25 °C with a mechanical stirring speed of 200 rpm. Three parallel samples were set up, and samples were taken and analyzed at predetermined time points of 0 min, 1 min, 2 min, 4 min, 6 min, 8 min, and 10 min.

[0032] like Figure 2 As shown in (a), when the amount of PS added increased from 0.1 mM to 1 mM, the removal efficiency of As(III) only decreased slightly from 86.82% to 78.3%. This small change indicates that the system has reached a limiting saturation point, after which increasing the amount of PS does not improve the oxidation of As(III). On the contrary, excess PS may participate in the quenching reaction, in which excess sulfate radicals (SO42-) are released. - •) They may recombine or react with non-target substances, thereby reducing their effective participation in the As(III) oxidation process.

[0033] 2. Effect of coexisting Fe(II) The effect of Fe(II) concentration in the range of 0.05 mM to 0.2 mM on the efficiency of As(III) removal mediated by EGCG in the FeS2 / Fe(II) / PS system was investigated under the conditions of FeS2 concentration of 0.1 g / L, initial As(III) concentration of 1 mg / L, EGCG concentration of 25 μM, and PS concentration of 0.2 mM. The experiment was conducted at 25 °C with mechanical stirring at 200 rpm. Three parallel samples were set up, and samples were taken at predetermined time points of 0 min, 1 min, 2 min, 4 min, 6 min, 8 min, and 10 min for analysis.

[0034] like Figure 2 As shown in (b), increasing the Fe(II) concentration from 0.05 mM to 0.1 mM significantly improved the As(III) removal rate, increasing it from 85.1% to 99.4%. This result indicates that relatively high concentrations of Fe(II) can continuously activate PS, thereby generating more reactive oxygen species, such as sulfate radicals (SO42-). -The reactive oxygen species (ROS) such as · and hydroxyl radicals (·OH) accelerate the oxidative removal of As(III). However, when the Fe(II) concentration is greater than 0.1 mM, the removal rate of As(III) drops sharply from 99.4% to 67.1%, indicating that there is a threshold beyond which excess Fe(II) leads to radical quenching.

[0035] 3. Effects of EGCG concentration EGCG plays a crucial role as a promoter of the Fe(II) / Fe(III) redox cycle in this system. This study investigated the effect of EGCG concentrations ranging from 10 μM to 100 μM on the efficiency of As(III) removal mediated by the EGCG-mediated FeS2 / Fe(II) / PS system under the conditions of 0.1 mM Fe(II) concentration, 0.1 g / L FeS2 concentration, 1 mg / L initial As(III) concentration, and 0.2 mM PS concentration. The experiment was conducted at 25 °C with a mechanical stirring speed of 200 rpm. Three parallel samples were set up, and samples were collected and analyzed at predetermined time points of 0 min, 1 min, 2 min, 4 min, 6 min, 8 min, and 10 min.

[0036] like Figure 2 As shown in (c), increasing the EGCG concentration from 10 μM to 25 μM increased the As(III) removal rate from 57.0% to 86.4%, demonstrating that EGCG possesses chelating and reducing properties as well as the ability to promote the continuous activation of PS. However, when the EGCG concentration increased to 100 μM, the As(III) removal rate decreased to 71.4%, indicating that EGCG has both the function of chelating Fe(III) and the function of scavenging free radicals, and there is a certain balance in performance between these dual functions.

[0037] 4. The influence of coexisting anions Select Cl - SO4 2- HCO3 - and H2PO4 - The effects of four typical inorganic anions on the removal efficiency of As(III) in an EGCG-mediated FeS2 / Fe(II) / PS system were investigated. The concentration range of each anion was set from 0.1 mM to 10 mM. Other reaction conditions were as follows: Fe(II) concentration 0.1 mM, FeS2 concentration 0.1 g / L, initial As(III) concentration 1 mg / L, EGCG concentration 25 μM, and PS concentration 0.2 mM. The experiment was conducted at 25 °C with a mechanical stirring speed of 200 rpm. Three parallel samples were prepared, and samples were taken for analysis at the 10 min time point of the reaction.

[0038] like Figure 2 As shown in (d) in the figure, Cl - and SO4 2- The impact on the removal efficiency of As(III) is relatively small, while that on HCO3 is relatively small. - and H2PO4 - The presence of [a substance] led to a significant decrease in the removal rate of As(III), from 93.1% to 19.6% and 19.2%, respectively. This inhibitory effect stems from two mechanisms: first, free radical scavenging, HCO3- […]. - and H2PO4 - It can be used as SO4 - Scavengers of · and ·OH free radicals, converting them into less reactive substances, such as CO3. - · and HPO4 - Its oxidation potential is significantly lower than that of SO4. - · and ·OH. Second, iron precipitate forms, HCO3. - and H2PO4 - It forms a precipitate with Fe(III), reducing the effective iron concentration in the system.

[0039] Example 3: Investigation into the electron transport mechanism enhanced by EGCG 1. Oxidation mechanism To identify the main free radicals involved in the oxidative removal of As(III), free radical quenching experiments and electron paramagnetic resonance (EPR) spectroscopy were conducted. The specific experimental procedure was as follows: In an optimized EGCG-mediated FeS2 / Fe(II) / PS system, the Fe(II) concentration was 0.1 mM, the FeS2 concentration was 0.1 g / L, the initial As(III) concentration was 1 mg / L, the EGCG concentration was 25 μM, and the PS concentration was 0.2 mM. Tert-butanol or methanol at concentrations of 25 mM, 50 mM, and 100 mM were added, respectively. The experiment was conducted at 25 °C with a mechanical stirring speed of 200 rpm. Three parallel samples were set up, and samples were taken and analyzed at predetermined time points of 0 min, 1 min, 2 min, 4 min, 6 min, 8 min, and 10 min.

[0040] The results are as follows Figure 3 As shown, both tert-butanol and methanol inhibited the oxidative removal of As(III), but methanol's inhibitory effect was significantly stronger than that of tert-butanol. Specifically, increasing the concentration of tert-butanol from 0 mM to 100 mM reduced the As(III) removal rate from 89.3% to 76.1%. Meanwhile, within the same concentration range, methanol reduced the As(III) removal rate to 66.1%. These results indicate that in the EGCG-promoted system, SO42- - · and ·OH are likely the main oxidizing agents that enable the As(III) transformation.

[0041] To further clarify the dominant active substances in the EGCG-mediated FeS2 / Fe(II) / PS system, DMPO was used as an optical scavenger, and EPR technology was employed to detect characteristic active substances. The specific experimental steps were as follows: DMPO was used as SO42-... - Spin trapping agents for · and ·OH radicals were used. 30 μL of sample was added to 30 mL of DMPO solution with a concentration of 100 mM and a solvent of 10 v / v% methanol aqueous solution. After mixing, a quantitative mixture was drawn in using a capillary tube. A quartz tube was then fitted and inserted into the EPR sample chamber to begin radical analysis. The test conditions were: central magnetic field of 3500 G, scan width of 100 G, microwave energy of -6.33 mW, microwave attenuation of 15 dB, resonant frequency of 9.82 GHz, scan time of 30 s, modulation amplitude of 1 G, and modulation frequency of 100 kHz.

[0042] like Figure 4 As shown, the two characteristic spectra detected correspond to DMPO-OH with an intensity ratio of 1:2:2:1 and the DMPO-SO4 adduct, respectively. Notably, the DMPO-OH signal is significantly stronger than that of DMPO-SO4. This difference is attributed to the rapid conversion of DMPO-SO4 and its high rate constant. k From 9.1×10 5 M -1 s -1 Converted to 6.0×10 8 M -1 s -1 These results are consistent with free radical quenching experiments, confirming that EGCG promotes SO42- quenching. - The formation of · and ·OH radicals plays a key role, and these free radicals are the main oxidants driving the removal of As(III).

[0043] Besides SO4 - In addition to · and ·OH, the role of molecular oxygen in the reaction system was also evaluated. The specific experimental procedure was as follows: 0.1 mM Fe(II), 0.1 g / L FeS2, 1 mg / L As(III), 0.2 mM PS, and 25 μM EGCG were added sequentially to a 1 mg / L As(III) solution pre-purged with nitrogen for 30 min. The experiment was conducted at 25 °C with mechanical stirring at 200 rpm. Three parallel samples were set up, and samples were taken for analysis at the 10 min time point of the reaction.

[0044] like Figure 5 As shown, under saturated air conditions, the removal rate of As(III) reached 98.5% within 10 minutes, while in a nitrogen environment, the removal efficiency dropped to 87.4%. This decrease indicates that O2 actively participated in the reaction and was one of the contributors to the oxidation and removal of As(III).

[0045] 2. Adsorption mechanism study like Figure 6 As shown, SEM-EDS analysis revealed that the mass percentage of arsenic in pyrite increased tenfold after treatment compared to before treatment, confirming the effective removal and fixation of arsenic on FeS2. Meanwhile, Figure 7 The As3d signal intensity in the ferrite flocs was significantly higher than that in FeS2 alone, indicating that arsenic was mainly absorbed through the ferrite flocs, while a small amount was directly adsorbed on the FeS2 surface.

[0046] To further investigate the binding properties of arsenic on the surfaces of FeS2 and Fe2O3, this invention performed density functional theory calculations to evaluate the adsorption energy and Gibbs free energy of different arsenic species.

[0047] like Figure 8 As shown, the adsorption energies of As(III) and As(V) in the dicoordinated binuclear configuration of FeS2 are... E ads The values ​​were -1.432 eV and -1.427 eV, respectively, indicating moderate adsorption affinity. However, on Fe2O3, the monocoordinate mononuclear complex... E ads The value is even better, at -1.894 eV, while the value of the two-coordinated binuclear complex is... E ads The value is -1.421 eV. This indicates that the adsorption of As(III) on Fe2O3 in the monodentate mononuclear structure is more energy-favorable than that on FeS2.

[0048] Based on the above results, this invention proposes an oxidative removal mechanism for As(III) in the EGCG-enhanced FeS2 / Fe(II) / PS system, see [link to relevant documentation]. Figure 9 The oxidation process involves the synergistic effect between Fe(II), FeS2, PS and EGCG, in which the oxidation-adsorption coupling mechanism jointly achieves the efficient removal of As(III).

[0049] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

[0050] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for removing arsenic from water using a natural polyphenol-mediated pyrite-persulfate system, characterized in that, Includes the following steps: The water containing trivalent arsenic is mixed with natural polyphenols, pyrite, ferrous salts and persulfate to react, so that the trivalent arsenic is oxidized to pentavalent arsenic. The pentavalent arsenic is then adsorbed and fixed, thus removing arsenic from the water. The natural polyphenol is at least one of epigallocatechin gallate, gallic acid, tea polyphenols, proanthocyanidins, or luteolin.

2. The method according to claim 1, characterized in that, In the reaction system, the concentration of natural polyphenols is 0.01mM~0.1mM, the dosage of pyrite is 0.1g / L~1g / L, the concentration of ferrous salt is 0.05mM~0.2mM, and the concentration of persulfate is 0.1mM~1mM.

3. The method according to claim 1, characterized in that, The natural polyphenol is epigallocatechin gallate, with a concentration of 0.01 mM to 0.1 mM.

4. The method according to claim 1, characterized in that, The ferrous salt is ferrous sulfate or ferrous chloride, with a concentration of 0.05 mM to 0.1 mM.

5. The method according to claim 1, characterized in that, The persulfate is sodium persulfate, potassium persulfate, or ammonium persulfate.

6. The method according to claim 1, characterized in that, The reaction time is 2 min to 10 min.

7. The method according to claim 1, characterized in that, The reaction temperature is 24℃~26℃.

8. The method according to any one of claims 1-7, characterized in that, The water containing trivalent arsenic is acidic mine drainage, arsenic-containing groundwater, or metallurgical industrial wastewater.

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