A method for removing chlorine by self-electro-flocculation based on catalysis

Abstract

The present invention discloses a method for chlorine removal by self-electro-flocculation based on catalysis. Addressing the industry challenge of removing high-concentration chloride ions from industrial wastewater, the present invention proposes a catalysis-driven self-electro-flocculation process for chlorine removal. The process utilizes the self-generation of electricity and ion storage characteristics of aluminum-air batteries to provide electrical energy reserves and ion support for the subsequent electro-flocculation dechlorination process, effectively alleviating the problem of electrode passivation while also achieving "self-power" supply. The process also utilizes the catalytic activity of a bifunctional HER / ORR catalyst to catalytically drive the rate-control steps in both the aluminum-air battery system and the electro-flocculation system, reducing the required overpotential for the reaction and thereby achieving a rapid self-electro-flocculation dechlorination process.

Description

Technical Field

[0001] The invention belongs to the field of sewage treatment, and in particular relates to a method for removing chlorine by self-electro-flocculation based on catalysis drive. Background Art

[0002] In recent years, the petrochemical, pharmaceutical, coal chemical, and thermal power generation industries have flourished, but this has also led to a series of environmental problems, particularly the large amounts of high-chloride ion wastewater generated during production. Direct discharge of this wastewater not only damages the surrounding ecosystem but also impacts the living environment and health of nearby residents. Therefore, finding appropriate methods to treat this wastewater is crucial for protecting public health and promoting the green and sustainable development of key industries.

[0003] At present, the methods for removing chloride ions from wastewater mainly include adsorption, oxidation, membrane separation, chemical coagulation and electrocoagulation. However, due to the characteristics of high chloride ion concentration and many interfering substances (organic matter, cations and anions, etc.) in the actual wastewater of relevant key industries, the existing treatment methods are difficult to meet the comprehensive requirements of green, economical and sustainable aspects.

[0004] In comparison, the electroflocculation method combines the advantages of chemical coagulation and electrochemical methods. It has the advantages of simple operation, no need for chemical reagents, stable and easy separation of flocs, high safety, and no secondary pollution. It has greater potential for removing high-concentration chloride ions in wastewater. Its mechanism of action is as follows: With metal aluminum as the double electrode, an oxidation reaction occurs at the anode after power is applied to produce highly active Al 3+ , the hydrogen evolution reaction (HER) occurs at the cathode to produce H2 and OH - , then, the highly active Al 3+ and OH - Through hydrolysis and polymerization, flocs with high specific surface area and abundant surface hydroxyl radicals are generated. The flocs then capture and remove chloride ions through adsorption, bridging, and sweeping net capture. However, the electroflocculation method also has the following problems that seriously restrict its industrial application:

[0005] (1) The electrocoagulation process consumes a lot of electricity, which makes the operation cost of the traditional electrocoagulation process high;

[0006] (2) Due to the poor hydrogen evolution activity of the cathode aluminum electrode, the traditional electrocoagulation process has a low efficiency;

[0007] (3) Traditional electrocatalysts with high HER activity are expensive, which limits their industrial applications;

[0008] (4) Since high-chloride ion wastewater contains a large amount of chloride ions, traditional electrocoagulation catalysts may be poisoned by chlorine. Summary of the Invention

[0009] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0010] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0011] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for removing chlorine by self-electro-flocculation based on catalytic drive.

[0012] In order to solve the above technical problems, the present invention provides the following technical solutions: a method for removing chlorine based on catalytic driven self-electro-flocculation, comprising:

[0013] Prepare an electrolysis device: This device consists of an electrolytic cell and two separate anode Al electrodes and cathode catalyst electrodes. The cell has a liquid inlet and outlet at the top and bottom, respectively, and a vent at the top. The anode Al electrode and cathode electrode are connected by wires and connected and disconnected by a switch.

[0014] Treatment of chlorine in wastewater: wastewater is injected into the electrolytic cell, and the anode metal Al electrode and the cathode catalyst electrode are connected to construct an aluminum-air battery system, in which the anode Al undergoes oxidation reaction to generate Al 3+ , oxygen reduction reaction ORR occurs at the cathode to generate OH - ,At the same time, chemical energy is converted into electrical energy, completing the power generation-ion storage process;

[0015] After the reaction, the switch is disconnected and the anode metal Al electrode and the cathode catalyst are connected to construct an electro-flocculation system. Driven by the electricity stored in the aluminum-air battery system, the anode Al undergoes an oxidation reaction to generate Al 3+ , hydrogen evolution reaction HER occurs at the cathode to generate H2 and OH - ,Al 3+ and OH - Combined to form Al(OH)3 flocs;

[0016] Al(OH)3 flocs remove chloride ions through adsorption, bridging, and sweeping.

[0017] As a preferred embodiment of the method of the present invention, the cathode electrode is composed of a gas diffusion layer substrate and a catalyst, wherein the cathode catalyst is a HER / ORR bifunctional catalyst.

[0018] As a preferred embodiment of the method of the present invention, the preparation method of the HER / ORR bifunctional catalyst is as follows:

[0019] Synthesis of Ni nanoflowers: NiCl2·6H2O, hexamethylenetetramine, and polypyrrolidone were fully dissolved in a mixed solution of water and ethanol, and then the solution was transferred to a reactor and heated for reaction. After the reaction, the product was washed alternately with anhydrous ethanol and water three times and dried to obtain the synthesized Ni nanoflowers.

[0020] Synthesis of NiSSe / NC HER / ORR bifunctional catalyst: The synthesized Ni nanoflowers were calcined under Ar atmosphere to obtain Ni / NC. Subsequently, sulfur powder and selenium powder were evenly mixed and loaded into a porcelain boat and placed at the front end of a tube furnace. Ni / NC was then loaded into a porcelain boat and placed at the front end of a tube furnace. The temperature was then raised to 500°C under Ar atmosphere at a heating rate of 1°C / min and reacted for 5 hours to obtain the synthesized NiSSe / NC HER / ORR bifunctional catalyst.

[0021] As a preferred embodiment of the method of the present invention, the ratio of NiCl2·6H2O, hexamethylenetetramine and polypyrrolidone is 0.2-0.4 mol: 0.6-1 mol: 4-10 g.

[0022] As a preferred embodiment of the method of the present invention, the heating reaction has a reaction temperature of 100 to 140° C. and a reaction time of 24 to 48 hours.

[0023] As a preferred embodiment of the method of the present invention, wherein: the calcination to obtain Ni / NC is performed at a temperature of 800 to 900° C. and a calcination time of 1 to 4 hours.

[0024] As a preferred embodiment of the method of the present invention, the ratio of the sulfur powder, selenium powder and Ni / NC is 100-200 mg: 300-400 mg: 50-150 mg.

[0025] As a preferred embodiment of the method of the present invention, the wastewater comprises desulfurization high-concentration chloride ion wastewater from a thermal power plant.

[0026] Beneficial effects of the present invention:

[0027] (1) The present invention addresses the industry's difficult problem of removing high-concentration chloride ions in industrial wastewater and proposes a catalytically driven self-electro-coagulation dechlorination process. The self-generation of electricity and ion storage characteristics of aluminum-air batteries are utilized to provide power reserves and ion guarantees for the subsequent electro-coagulation dechlorination process, effectively alleviating the problem of electrode passivation while also achieving "self-power" supply. At the same time, the catalytic activity of the bifunctional HER / ORR catalyst is utilized to catalytically drive the rate-control steps in the aluminum-air battery system and the electro-coagulation system, respectively, and reduce the required overpotential of the reaction, thereby achieving a rapid self-electro-coagulation dechlorination process.

[0028] (2) The NiSSe / NC bifunctional HER / ORR catalyst of the present invention is simultaneously sulfurized and selenized, which can induce the delocalization of electrons in the catalytic active sites of NiSSe / NC, thereby facilitating the adsorption of H*, a key intermediate in the HER reaction, and *OOH, a key intermediate in the ORR reaction. At the same time, NC can improve the conductivity of the catalyst and the resistance of the catalyst to chloride ion poisoning. Therefore, NiSSe / NC exhibits good stability and excellent HER activity (110 mV, 10 mA / cm 2 ) and ORR activity (half-wave potential 0.9 V), and the open circuit voltage (1.8 V) of the aluminum-air battery constructed based on NiSSe / NC can realize self-power supply in the electrocoagulation process.

[0029] (3) The catalytically driven self-electro-flocculation dechlorination process proposed in the present invention can be applied to the removal of high-concentration chloride ions in desulfurization wastewater from thermal power plants. It has the advantages of simple operation, no operating energy consumption, good treatment effect, etc., and has good market competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0031] Figure 1 This is a schematic diagram of the chlorine removal process based on catalytic drive and self-electro-flocculation in an embodiment of the present invention.

[0032] Figure 2 HER activity test curve of NiSSe / NC and commercial Pt / C in the embodiment of the present invention.

[0033] Figure 3 This is a graph showing the ORR activity test of NiSSe / NC and commercial Pt / C in an embodiment of the present invention.

[0034] Figure 4 Figure 2 is a diagram of chlorine removal by self-electro-coagulation based on NiSSe / NC HER / ORR bifunctional catalyst in an embodiment of the present invention, wherein (a) chlorine removal by self-electro-coagulation based on NiSSe / NC HER / ORR bifunctional catalyst, (b) XRD spectrum of flocs, and (c) element distribution diagram of flocs.

[0035] Figure 5 These are the test results of the chlorine poisoning resistance of NiSSe / NC and commercial Pt / C catalysts in the examples of the present invention.

[0036] Figure 6 This is the SEM image of the NiSSe / NC HER / ORR bifunctional catalyst in the embodiment of the present invention.

[0037] Figure 7 Element distribution diagram of the NiSSe / NC HER / ORR bifunctional catalyst in an embodiment of the present invention. DETAILED DESCRIPTION

[0038] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0039] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0040] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0041] Example 1

[0042] Synthesis of NiSSe / NC bifunctional catalyst:

[0043] (1) Synthesis of Ni nanoflowers: 0.3 mol NiCl2·6H2O, 0.8 mol hexamethylenetetramine, and 6 g polypyrrolidone were fully dissolved in a mixed solution of 40 mL water and 80 mL ethanol. The solution was then transferred to a 250 mL reactor and reacted at 120°C for 36 h. After the reaction, the product was washed three times with anhydrous ethanol and water alternately and dried to obtain the synthesized Ni nanoflowers.

[0044] (2) Synthesis of NiSSe / NC HER / ORR bifunctional catalyst: The Ni nanoflowers synthesized in (1) were calcined at 850 °C for 2 h in an Ar atmosphere to obtain Ni / NC;

[0045] Subsequently, 140 mg of sulfur powder and 360 mg of selenium powder were evenly mixed and loaded into a porcelain boat and placed at the front end of a tube furnace. Then, 100 mg of Ni / NC was loaded into a porcelain boat and placed at the front end of a tube furnace. The temperature was then raised to 500 °C at a heating rate of 1 °C / min under an Ar atmosphere and reacted for 5 h to obtain the synthesized NiSSe / NC HER / ORR bifunctional catalyst.

[0046] The SEM images of NiSSe / NC HER / ORR bifunctional catalysts are shown in Figure 6 , the element distribution diagram of NiSSe / NC HER / ORR bifunctional catalyst is shown in Figure 7 ,Depend on Figure 6 and Figure 7 It can be seen that the NiSSe / NC HER / ORR bifunctional catalyst presents a cubic nanoflower structure, and the Ni, S, Se, N, N, and C elements are evenly distributed in the catalyst. Combined with the ICP-OES and elemental analysis results, the Ni:S:Se atomic ratio is 1:1:1. These structural surfaces successfully prepared the NiSSe / NC HER / ORR bifunctional catalyst.

[0047] Comparative Example 1

[0048] Commercial Pt / C was used as a comparison (brand: Anaiji Special; Pt loading 5%)

[0049] HER and ORR activity test results:

[0050] The prepared electrode material was coated on a rotating disk working electrode, Ag / AgCl was used as a reference electrode, platinum wire was used as a counter electrode, and the electrolyte was 0.1 M KOH to investigate the hydrogen evolution performance (HER) and oxygen reduction performance (ORR) of the catalyst.

[0051] The HER activity test curves of NiSSe / NC and commercial Pt / C are shown in Figure 2 , the ORR activity test curves of NiSSe / NC and commercial Pt / C are shown in Figure 3 .

[0052] from Figure 2 and Figure 3 It can be seen that the HER activity of the NiSSe / NC HER / ORR bifunctional catalyst prepared by the present invention (110mV, 10mA / cm 2 ) and ORR activity (half-wave potential 0.9V), the open circuit voltage (1.8V) of the aluminum-air battery constructed based on NiSSe / NC, good HER and ORR activity and high open circuit voltage provide a guarantee for self-electro-coagulation chlorine removal based on NiSSe / NC HER / ORR bifunctional catalyst.

[0053] Further observation reveals that the HER and ORR activities of the NiSSe / NC HER / ORR bifunctional catalyst of the present invention are comparable to those of commercial Pt / C, but its synthesis raw material cost is low, which can significantly reduce the catalyst synthesis cost.

[0054] Example 2

[0055] Take the treatment of desulfurization wastewater (chloride ion concentration = 5000ppm) from a thermal power plant in Shanxi as an example:

[0056] (1) Electrolysis device: See the schematic diagram Figure 1 The electrolysis device consists of a 3L electrolytic cell with an anode Al electrode and a cathode catalyst electrode on the left and right sides. The upper and lower ends of the electrolytic cell are respectively provided with a liquid outlet and a liquid inlet, and the upper end of the electrolytic cell is provided with an exhaust hole. The anode Al electrode and the cathode electrode are connected by a wire and connected and disconnected by a switch.

[0057] (2) Treatment of chlorine in wastewater: 2L of desulfurization wastewater from a thermal power plant in Shanxi with a chloride ion concentration of 5000ppm was injected into the electrolytic cell, and the anode metal Al electrode and the cathode catalyst electrode were connected to construct an aluminum-air battery system, in which the anode Al underwent oxidation reaction to generate Al 3+ , oxygen reduction reaction ORR occurs at the cathode to generate OH - ,At the same time, chemical energy is converted into electrical energy, completing the power generation-ion storage process;

[0058] Then the switch is disconnected, and the anode metal Al electrode and the cathode catalyst are connected to construct an electro-flocculation system. Driven by the electricity stored in the aluminum-air battery system, the anode Al undergoes an oxidation reaction to generate Al 3+ , hydrogen evolution reaction HER occurs at the cathode to generate H2 and OH - ,Al 3+ Combined with OH- to form Al(OH)3 flocs;

[0059] Al(OH)3 flocs remove chloride ions through adsorption, bridging, and sweeping.

[0060] (3) The results of the process of the present invention are as follows Figure 4 , including: (a) chlorine removal results based on self-electro-flocculation of NiSSe / NC HER / ORR bifunctional catalyst, (b) XRD spectrum of flocs, and (c) element distribution diagram of flocs.

[0061] Depend on Figure 4 (a) It can be seen that the process of the present invention can be used to treat high-concentration chloride ions, and the chloride ion concentration in the desulfurization wastewater can reach the desulfurization wastewater recycling standard of 2000ppm within 19 minutes;

[0062] Figure 4 (b) and 4(c) indicate that the flocs contain Cl element. The above results verify that the process of the present invention does not require energy consumption and can achieve rapid self-electroflocculation and chlorine removal.

[0063] Example 3

[0064] According to Example 2, 5 batches were run continuously, each batch running for 1500 min. The results of the treatment time reaching the target using NiSSe / NC and commercial Pt / C catalysts are as follows: Figure 5 .

[0065] Depend on Figure 5 The time it took for the NiSSe / NC catalyst to reach the chloride ion standard remained basically unchanged after 5 consecutive batches of treatment, while the time it took for the Pt / C catalyst to reach the standard increased significantly after 2 batches of treatment, indicating that the NiSSe / NC catalyst has good resistance to chloride poisoning.

[0066] Comparative Example 2

[0067] On the basis of Example 1, sulfur powder is not added in step (2), and the specific difference is:

[0068] 500 mg of selenium powder was mixed evenly and loaded into a porcelain boat, which was placed at the front end of a tube furnace. Then 100 mg of Ni / NC was loaded into a porcelain boat, which was placed at the front end of a tube furnace. The temperature was then raised to 500 °C at a heating rate of 1 °C / min under an Ar atmosphere and reacted for 5 h to obtain the catalyst.

[0069] The system was operated according to Example 2 to treat high concentration chloride ions. After 121 minutes, the chloride ion concentration in the desulfurization wastewater reached 2000 ppm, which is the desulfurization wastewater recycling standard.

[0070] Comparative Example 3

[0071] On the basis of Example 1, no selenium powder is added in step (2), and the specific difference is:

[0072] 500 mg of sulfur powder was mixed evenly and loaded into a porcelain boat and placed in the front end of a tube furnace. Then 100 mg of Ni / NC was loaded into a porcelain boat and placed in the front end of a tube furnace. The temperature was then raised to 500 °C at a heating rate of 1 °C / min under an Ar atmosphere and reacted for 5 h to obtain the catalyst.

[0073] The system was operated according to Example 2 to treat high concentration chloride ions, and the chloride ion concentration in the desulfurization wastewater reached the desulfurization wastewater recycling standard of 2000 ppm in 162 minutes.

[0074] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, and all of these should be included in the scope of the present invention.

Claims

1. A method for removing chlorine by self-electro-flocculation driven by catalysis, characterized in that: include, Prepare an electrolysis device: This device consists of an electrolytic cell and two separate anode Al electrodes and cathode catalyst electrodes. The cell has a liquid inlet and outlet at the top and bottom, respectively, and a vent at the top. The anode Al electrode and cathode electrode are connected by wires and connected and disconnected by a switch. Treatment of chlorine in wastewater: wastewater is injected into the electrolytic cell, and the anode metal Al electrode and the cathode catalyst electrode are connected to construct an aluminum-air battery system, in which the anode Al undergoes oxidation reaction to generate Al 3+ , oxygen reduction reaction ORR occurs at the cathode to generate OH - ,At the same time, chemical energy is converted into electrical energy, completing the power generation-ion storage process; After the reaction, the switch is disconnected and the anode metal Al electrode and the cathode catalyst are connected to construct an electro-flocculation system. Driven by the electricity stored in the aluminum-air battery system, the anode Al undergoes an oxidation reaction to generate Al 3+ , hydrogen evolution reaction HER occurs at the cathode to generate H2 and OH - , Al 3+ and OH - Combined to form Al(OH)3 flocs; Al(OH)3 flocs remove chloride ions through adsorption, bridging, and sweeping net capture. The cathode electrode is composed of a gas diffusion layer matrix and a catalyst, wherein the cathode catalyst is a HER / ORR dual-function catalyst; The preparation method of the HER / ORR bifunctional catalyst is as follows: Synthesis of Ni nanoflowers: NiCl2•6H2O, hexamine, and polypyrrolidone were fully dissolved in a mixed solution of water and ethanol, and then the solution was transferred to a reactor and heated for reaction. After the reaction, the product was washed alternately with anhydrous ethanol and water three times and dried to obtain the synthesized Ni nanoflowers. Synthesis of NiSSe / NC HER / ORR bifunctional catalyst: The synthesized Ni nanoflowers were calcined under Ar atmosphere to obtain Ni / NC. Subsequently, sulfur powder and selenium powder were evenly mixed and loaded into a porcelain boat and placed at the front end of a tube furnace. Ni / NC was then loaded into a porcelain boat and placed at the front end of a tube furnace. The temperature was then raised to 500°C under Ar atmosphere at a heating rate of 1°C / min for 5 h to obtain a NiSSe / NC HER / ORR bifunctional catalyst.

2. The method according to claim 1, wherein: The ratio of NiCl2•6H2O, hexamethylenetetramine and polypyrrolidone is 0.2-0.4 mol: 0.6-1 mol: 4-10 g.

3. The method according to claim 1, wherein: The heating reaction has a reaction temperature of 100-140° C. and a reaction time of 24-48 hours.

4. The method according to claim 1, wherein: The Ni / NC is obtained by calcining, wherein the calcination temperature is 800-900° C. and the calcination time is 1-4 h.

5. The method according to claim 1, wherein: The ratio of the sulfur powder, selenium powder and Ni / NC is 100-200 mg: 300-400 mg: 50-150 mg.

6. The method according to claim 1, wherein: The wastewater includes desulfurization high-concentration chloride ion wastewater from thermal power plants.

Images