Preparation and application of FeS2-coated FeOOH three-dimensional particles

Abstract

The invention relates to the field of advanced treatment of industrial wastewater, in particular to preparation and application of FeS2-coated FeOOH three-dimensional particles, a certain amount of FeS2 is added into a Na2SO4 solution and hydrogen peroxide to be subjected to an electrolytic reaction in an electrolytic tank, an anode ruthenium iridium titanium plate and a cathode plate are carbon cloth or a gas diffusion electrode GDE, and FeS2-coated FeOOH of a core-shell structure is prepared. According to the invention, the advanced treatment of the high-salt industrial wastewater by the FeS2-coated FeOOH three-dimensional particle electrode can be realized. FeS < 2-> FeOOH is used as a three-dimensional particle, and the three-dimensional particle electrode can generate OH, O2 <->, < 1 > O2, active chlorine free radicals and the like. And efficient removal of TOC and TN is realized by utilizing the synergistic effect of free radicals and electron transfer on the surface of the FeS2-coated FeOOH material.

Description

Technical Field

[0001] The present invention relates to the field of deep treatment of industrial wastewater, and in particular to the preparation and application of FeS2@FeOOH three-dimensional particles. Background Art

[0002] The biochemical treatment of industrial wastewater aims to reduce total organic carbon (TOC) and total nitrogen (TN), but after conventional secondary biochemical treatment, the effluent still contains a large amount of toxic and harmful, difficult-to-degrade organic pollutants, and the suspended solids, chromaticity, and salt content are still high. Total organic carbon (TOC) and total nitrogen (TN) are commonly found in industrial biochemical effluent, which makes the treated wastewater unable to meet the discharge standards of coking wastewater and causes pollution to subsequent membrane treatment. In recent years, water purification processes based on electrocatalytic oxidation technology have attracted worldwide attention due to their strong oxidation ability, simple operation, and no secondary pollution. However, some shortcomings of traditional electrochemical processes, such as low current efficiency, mass transfer limitations, and high costs, limit their practical application. The three-dimensional electrode method is to fill granular electrodes between the anode and the cathode, which can not only improve the solution conductivity and accelerate the mass transfer rate in the reactor, but also produce and utilize a series of strong oxidants (·OH, ·O2, etc.), making the three-dimensional electrode method superior to traditional electrocatalytic methods in terms of pollutant removal efficiency. These advantages of three-dimensional particle electrodes provide a superior solution for the removal of organic pollutants in wastewater.

[0003] Patent CN110064408B invented an α-crystalline iron oxyhydroxide catalyst loaded with iron sulfide, which was prepared by hydrothermal method to form a doped material for photocatalytic degradation of organic matter and heavy metals. The FeS2 in this doped material can effectively remove the difficult-to-degrade organic pollutants in wastewater as a catalyst or particle electrode, but the reacted FeS2 will mostly dissolve in the electrolyte, releasing Fe 3+ and SO4 2- , thus generating sludge pollution. Summary of the invention

[0004] In order to solve the problem that FeS2 as a catalyst or particle electrode is easily soluble in electrolyte, generates sludge pollution, and cannot achieve the denitrification function, the present invention provides a preparation and application of FeS2@FeOOH three-dimensional particles.

[0005] This patent is to prepare a stable material of FeS2@FeOOH after processing FeS2, forming a three-dimensional particle electrode system of a three-dimensional electrode. This three-dimensional system achieves efficient removal of TOC and TN. This patent uses electrochemical in-situ preparation of FeS2@FeOOH core-shell structure, with mild reaction conditions, suitable for large-scale preparation, and the obtained material is stable, with the goal of removing TOC and TN.

[0006] The present invention is achieved through the following technical scheme: a method for preparing three-dimensional FeS2@FeOOH particles, comprising the following steps: A certain amount of FeS2 is added to Na2SO4 solution and hydrogen peroxide, and electrolyzed in an electrolytic cell, wherein the anode is a ruthenium iridium titanium plate and the cathode plate is a carbon cloth or a gas diffusion electrode GDE, to obtain FeS2@FeOOH with a core-shell structure.

[0007] As a further improvement of the technical solution of the present invention, in the electrolytic cell, the amount of FeS2 added is 3 g, the amount of Na2SO4 solution added is 200 mL, the amount of hydrogen peroxide added is 200 μL, the concentration of Na2SO4 solution is 1.5 g / L, and the concentration of hydrogen peroxide is 0.4 g / L.

[0008] As a further improvement of the technical solution of the present invention, the current density of the electrolysis reaction is 25 mA / cm 2 .

[0009] The present invention further provides an application of FeS2@FeOOH with a core-shell structure prepared by a method for preparing FeS2@FeOOH three-dimensional particles in the treatment of high-salt wastewater.

[0010] As a further improvement of the above-mentioned application technical solution, the concentration of NaCl in the high-salt wastewater is not less than 1000 mg / L.

[0011] As a further improvement of the above-mentioned application technical solution, the core-shell structured FeS2@FeOOH adopts the method of electrolysis treatment of high-salinity wastewater in the treatment of high-salinity wastewater.

[0012] As a further improvement of the above-mentioned application technology solution, when electrolyzing high-salinity wastewater, the anode used is an iridium-ruthenium-coated titanium plate, the cathode used is a carbon cloth or a gas diffusion electrode GDE, the dosage of the core-shell structured FeS2@FeOOH is 10-20 mg / L, and the current density is 10-30 mA / cm 2 .

[0013] As a further improvement of the above-mentioned application technical solution, the pH range of the high-salinity wastewater is 3.0-10, the initial concentration of Na2SO4 is not less than 1000 mg / L, the COD concentration of organic pollutants is 0-200 mg / L, and the NO3 - The concentration is 0~50mg / L.

[0014] The technical solution provided by the present invention has the following advantages compared with the prior art: 1) The present invention prepares FeS2@FeOOH three-dimensional particles with core-shell structure and stable material, which solves the problem of easy leaching of iron metal ions and loss of active sulfur in the prior art, and realizes Fe 2+ / Fe 3+ effective cycle.

[0015] 2) The present invention can realize the deep treatment of high-salt industrial wastewater with FeS2@FeOOH three-dimensional particle electrode. FeS2@FeOOH is used as a three-dimensional particle. The three-dimensional particle electrode can produce • OH, O2 •－ , 1 O2, active chlorine free radicals, etc. The synergistic effect of free radicals and electron transfer on the FeS2@FeOOH surface was used to achieve efficient removal of TOC and TN. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 This is a schematic TEM diagram of the core-shell structured FeS2@FeOOH prepared in Example 1. EDS mapping of TEM proves that an oxide with a thickness of 10 nm is formed on the surface of the particle electrode, generating a material with a core-shell structure.

[0019] Figure 2 The FTIR spectrum of FeS2@FeOOH with a core-shell structure prepared from FeS2 and Example 1 shows that a peak is observed at 3371 cm⁻¹, which is the characteristic peak of the –OH group in the carboxyl group. At approximately 2972 ​​cm⁻¹ and 1385 cm⁻¹, the stretching vibration of the CO bond and the stretching vibration of the CO bond correspond, respectively. FTIR analysis reveals the presence of a variety of functional groups on the surface of the original and used FeS2, which are important active catalytic sites for the particle electrode to participate in the degradation reaction. The appearance of the –OH peak after the reaction indicates that hydroxyl radicals are generated during the reaction and participate in the degradation process.

[0020] Figure 3 The XPS spectra of FeS2 and the core-shell structure FeS2@FeOOH prepared in Example 1 (ad is FeS2, eg is FeS2@FeOOH). From a and e, it can be seen that S, Fe and O are present. In the 2p energy spectrum of S (Figure b), the binding energy peaks of 162.7 and 161.9 eV belong to S in FeS2. 2-The binding energy peak of 168.9 eV corresponds to SO4 2- In FeS2@FeOOH, S 2- The characteristic peaks of SO4 2- The characteristic peak of FeS2 at 163.9 eV increases after the reaction, indicating that more hydrophobic substances such as S n 2- The accumulation of n 2- It is bound to FeS2 through covalent or ionic bonds and therefore remains on the surface of FeS2. The two peaks at 161.3 and 161.9 eV correspond to the disulfide of the reaction. The reason is that the SS bond is not as strong as the Fe-S bond, which makes the SS bond easier to break in the FeS2 lattice. The Fe2p spectrum of FeS2 shows a peak at a binding energy of 707.1 eV, corresponding to Fe(II)-S in FeS2, and the obvious peaks at 711.5 eV and 720.4 eV belong to Fe 3+ 2p3 / 2 and Fe 3+ 2p1 / 2, which means that Fe 3+ The difference between FeOOH, FeS2 and FeS2@FeOOH at 711.5 eV is attributed to the Fe-O and Fe-OOH bonds, further proving the formation of Fe2O3 and Fe-OOH amorphous phases. In addition, in the O 1s region, two main peaks can be observed in FeS2@FeOOH at 532 and 533 eV, corresponding to the Fe-O-Fe bond and the Fe-OH bond, respectively. No peak was observed at 530 eV, indicating the absence of Fe2O3, indicating the accumulation of OOH bonds.

[0021] Figure 4 Schematic diagram of the treatment results of Experimental Example 1. The results show that the amount of iron component dissolved during the reaction is negligible, which further confirms that the constructed three-dimensional electrode system has excellent reusability.

[0022] Figure 5 This is a schematic diagram of the processing results of Experimental Example 2. DETAILED DESCRIPTION

[0023] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0024] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all of the embodiments.

[0025] The specific embodiments of the present invention are described in detail below. Example 1

[0026] A method for preparing three-dimensional FeS2@FeOOH particles comprises the following steps: A certain amount of FeS2 was added to Na2SO4 solution and hydrogen peroxide, and electrolyzed in an electrolytic cell, where the anode was a ruthenium iridium titanium plate and the cathode was a carbon cloth, to obtain FeS2@FeOOH with a core-shell structure. In the electrolytic cell, the amount of FeS2 added was 3g, the amount of Na2SO4 solution added was 200mL, the amount of hydrogen peroxide added was 200μL, the concentration of Na2SO4 solution was 1.5g / L, and the concentration of hydrogen peroxide was 0.4g / L. Example 2

[0027] 1. Material Characterization Specific results such as Figures 1 to 3 shown.

[0028] 2. Test Example 1 The effluent from the secondary sedimentation tank after biochemical treatment of coking wastewater (high-salt wastewater) was taken as the treatment object, ruthenium-iridium-titanium plate was used as the anode, carbon cloth electrode was used as the cathode, the electrode plate spacing was 1 cm, the core-shell structure FeS2@FeOOH dosage was 15 g / L, and the current density was 20 mA / cm 2 ; The high-salt wastewater components are shown in the following table as initial values. After testing, the content of iron components in the simulated wastewater changed after 6 hours of reaction. Figure 4 shown. 3. Test Example 2 The effluent from the secondary sedimentation tank after biochemical treatment of coking wastewater (high-salt wastewater) was taken as the treatment object, ruthenium-iridium-titanium plate was used as the anode, carbon cloth electrode was used as the cathode, the electrode plate spacing was 4 cm, the dosage of FeS2@FeOOH with core-shell structure was 15 g / L, and the current density was 15 mA / cm 2 ; The water quality of the inlet and outlet water is as follows. After testing, the reaction results are shown in Figure 5 a, TOC, NO3 after 6 hours - The removal rates of -N and TN were 92.2%, 92.7% and 93.3% respectively (see the final values ​​and removal rates in the table above). Figure 5 b. After 5 tests, the removal rate was still high.

[0029] The above is only a specific implementation of the present invention, which enables those skilled in the art to understand or implement the present invention. Although detailed descriptions are given with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments, and they should all be covered by the protection scope of the claims.

Claims

1. A method for preparing three-dimensional FeS2@FeOOH particles, characterized in that: The steps include: A certain amount of FeS2 is added to Na2SO4 solution and hydrogen peroxide, and electrolyzed in an electrolytic cell, wherein the anode is a ruthenium iridium titanium plate and the cathode plate is a carbon cloth or a gas diffusion electrode GDE, to obtain FeS2@FeOOH with a core-shell structure.

2. A method for preparing three-dimensional FeS2@FeOOH particles according to claim 1, characterized in that: In the electrolytic cell, the amount of FeS2 added was 3 g, the amount of Na2SO4 solution added was 200 mL, the amount of hydrogen peroxide added was 200 μL, the concentration of Na2SO4 solution was 1.5 g / L, and the concentration of hydrogen peroxide was 0.4 g / L.

3. The method for preparing three-dimensional FeS2@FeOOH particles according to claim 1, characterized in that: The current density of the electrolysis reaction is 25 mA / cm 2 .

4. Application of FeS2@FeOOH with a core-shell structure prepared by the method for preparing three-dimensional FeS2@FeOOH particles as described in any one of claims 1 to 3 in the treatment of high-salt wastewater.

5. The use according to claim 4, characterized in that: The concentration of NaCl in the high-salt wastewater is not less than 1000 mg / L.

6. The use according to claim 5, characterized in that The core-shell structured FeS2@FeOOH adopts the electrolytic treatment method for high-salinity wastewater in the treatment of high-salinity wastewater.

7. The use according to claim 6, characterized in that When electrolyzing high-salinity wastewater, the anode used is an iridium-ruthenium-coated titanium plate, the cathode used is a carbon cloth or a gas diffusion electrode GDE, the dosage of the core-shell structure FeS2@FeOOH is 10-20 mg / L, and the current density is 10-30 mA / cm 2 .

8. The use according to claim 7, characterized in that The pH range of the high-salinity wastewater is 3.0-10, the initial concentration of Na2SO4 is not less than 1000 mg / L, the COD concentration of organic pollutants is 0-200 mg / L, and the NO3 - The concentration is 0~50mg / L.

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