Method for recovering manganese from manganese-containing wastewater

Abstract

The invention relates to a method for recovering manganese from manganese-containing wastewater. A method for recovering manganese from manganese-containing wastewater comprises the following steps: carrying out glow discharge plasma treatment on the manganese-containing wastewater to generate precipitates; and separating, washing and drying the precipitate to obtain manganese dioxide. According to the method for recovering manganese from the manganese-containing wastewater, the recovery process is simple, the reaction time is short, the recovery rate is up to 95%, and the purity of the recovered manganese dioxide is 96%. Reaction conditions are mild, and high-temperature heating is not needed.

Description

Technical Field

[0001] The present invention belongs to the technical field of resource recovery of manganese-containing wastewater, and particularly relates to a method for recovering manganese from manganese-containing wastewater. Background Art

[0002] Since the 21st century, with the rapid development of clean energy, electrode materials mainly composed of manganese compounds have been widely used. For example, they are used as catalysts for electrocatalytic oxidation-reduction reactions, or as cathode materials for lithium-ion batteries, aqueous zinc-ion batteries, etc., thus making the electrolytic manganese metal industry develop rapidly. While developing rapidly, a large amount of manganese-containing wastewater and waste residues need to be treated, posing new challenges to the sustainable development of the electrolytic manganese industry. The development of new technologies for the treatment and resource utilization of manganese-containing wastewater can not only reduce pollution but also improve the comprehensive utilization rate of manganese resources.

[0003] In view of this, the present invention proposes a new recovery method, which can recover manganese from manganese-containing wastewater and has the advantages of simple process and high recovery rate. Summary of the Invention

[0004] The object of the present invention is to provide a method for recovering manganese from manganese-containing wastewater, which has a simple process and can selectively recover manganese from manganese-containing wastewater with high selectivity.

[0005] To achieve the above object, the technical solution adopted is as follows:

[0006] A method for recovering manganese from manganese-containing wastewater, comprising the following steps:

[0007] After the manganese-containing wastewater is treated by glow discharge plasma, precipitation is generated;

[0008] The obtained precipitate is separated, washed, and dried to obtain manganese dioxide.

[0009] Furthermore, in the manganese-containing wastewater, there is at least one of the metals Li, Na, K, Cs, Mg, Ca, Al, In, Zn, La, Ce, Ni, Cu, Co, Fe, Cr, V.

[0010] Furthermore, the pressure of the glow discharge plasma treatment is 100 - 1000 Pa

[0011] Furthermore, the discharge atmosphere of the glow discharge plasma treatment is at least one of the following gases: air, or nitrogen, or oxygen, or argon, or helium.

[0012] Furthermore, during the glow discharge plasma treatment process, the reaction temperature is room temperature - 60 °C.

[0013] Furthermore, the discharge power supply of the glow discharge plasma treatment is an AC power supply with a voltage of 5-20 kV, a current of 0.5-2 A, and a frequency of 50 Hz-80 kHz.

[0014] Furthermore, the glow discharge plasma treatment has a treatment time of 5-30 minutes.

[0015] Another object of the present invention is to provide a manganese dioxide which is recovered by the above method and is a two-dimensional amorphous manganese dioxide nanoflower.

[0016] Another object of the present invention is to provide an application of the above-mentioned manganese dioxide. Since the purity of the two-dimensional amorphous manganese dioxide nanoflowers recovered by the above-mentioned method is as high as 96%, they can be directly used.

[0017] In order to achieve the above purpose, the technical solution adopted is:

[0018] The above-mentioned application of manganese dioxide in electrode materials.

[0019] Furthermore, the manganese dioxide is used as an electrocatalytic anode material to catalyze the oxidation reaction of 5-hydroxymethylfurfural; or as an electrocatalytic cathode material to catalyze the reduction reaction of nitrate.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] Glow discharge plasma refers to a low-temperature plasma discharge phenomenon, which is usually formed by high voltage excitation at low pressure or normal pressure. When the electric field strength applied to both ends of the gas is high enough, the ionization of the gas will occur, converting the gas molecules or atoms into positively charged ions and negatively charged electrons to form plasma. In the plasma, the collision and recombination reaction between ions and electrons and neutral particles will release energy to form brilliance, which is glow plasma. Glow discharge plasma has been industrialized in the fields of material surface modification, cleaning, and coating. An important function of glow discharge plasma is to reduce precious metal ions to metal elements. This method has been reported to be used for selective recovery of precious metal ions (Au, etc.) from non-precious metal solutions. However, it is generally believed that glow discharge plasma cannot affect non-precious metal ions, and the present invention realizes the selective recovery of non-precious manganese ions by glow discharge plasma technology. The selective recovery strategy of non-precious manganese ions using glow discharge plasma technology has not been reported. The technical solution of the present invention has the following advantages:

[0022] 1. The technical solution of the present invention is to perform glow discharge plasma treatment on wastewater containing metals such as Mn, Li, Na, K, Cs, Mg, Ca, Al, In, Zn, La, Ce, Ni, Cu, Co, Fe, Cr, V, etc. Only Mn is selectively recovered, opening up a new technical approach for the resource utilization of manganese-containing wastewater.

[0023] 2. The technical solution of the present invention has high selectivity for recovering manganese ions in general industrial manganese-containing wastewater containing multiple metal ions. It does not require the addition of flocculants or precipitants, does not use strong acids or strong bases, avoids secondary pollution, and the obtained recovered product manganese dioxide has a low impurity content. At the same time, it is driven by clean energy electricity, with the advantages of a simple recovery process, short reaction time, a recovery rate as high as 95%, mild reaction conditions, and no need for high-temperature heating.

[0024] 3. The technical solution of the present invention can recover manganese from wastewater with different manganese sources. The prepared manganese dioxide has the morphological characteristics of two-dimensional nanoflowers and no obvious lattice fringes, being an amorphous material. The prepared manganese dioxide powder can be used as an electrocatalytic anode material for catalyzing the oxidation reaction of 5-hydroxymethylfurfural, or manganese dioxide can be used as an electrocatalytic cathode material for catalyzing the nitrate reduction reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of a glow discharge plasma reactor for the recovery method of the present invention.

[0026] Figure 2 It is a schematic diagram of the change in manganese ion concentration before and after glow plasma treatment of manganese-containing wastewater solution.

[0027] Figure 3 It is a schematic diagram of the change in the recovery amount of different metal ions before and after glow plasma treatment of manganese-containing wastewater solution.

[0028] Figure 4 It is the X-ray diffraction pattern of the recovered MnO 2 from manganese-containing wastewater.

[0029] Figure 5 The scanning electron microscope (SEM) image of the recovered MnO 2 from manganese-containing wastewater.

[0030] Figure 6 The transmission electron microscope (TEM) image of the recovered MnO 2 from manganese-containing wastewater, and the elemental mapping images of manganese and oxygen.

[0031] Figure 7 It is a schematic diagram of the XPS spectrum of Mn 2p.

[0032] Figure 8 It is for MnO 2Fourier transform infrared spectroscopy (FTIR) diagram. Detailed implementation mode

[0033] In order to further elaborate on a method for recovering manganese from manganese-containing wastewater according to the present invention and achieve the intended invention purpose, the following combines preferred embodiments to detail the specific implementation mode, structure, characteristics and functions of a method for recovering manganese from manganese-containing wastewater proposed according to the present invention. In the following description, different "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0034] Before elaborating in detail on a method for recovering manganese from manganese-containing wastewater according to the present invention, it is necessary to further explain the relevant materials mentioned in the present invention to achieve better results.

[0035] The manganese-containing wastewater in the embodiments of the present invention mainly uses nitrates and chlorides, and is specifically prepared from the following metal salts:

[0036] Manganese sulfate monohydrate, molecular formula: MnSO 4 ·H 2 O, CAS number: 10034-96-5.

[0037] Manganese chloride, molecular formula: MnCl 2 , CAS number: 7773-01-5.

[0038] Aluminum nitrate nonahydrate, molecular formula: Al(NO3) 3 ·9H 2 O, CAS number: 7784-27-2.

[0039] Zinc chloride, molecular formula: ZnCl 2 , CAS number: 7646-85-7.

[0040] Lanthanum nitrate hexahydrate, molecular formula: LaN 3 O 9 ·6H 2 O, CAS number: 10277-43-7.

[0041] Nickel nitrate, molecular formula: Ni(NO 3 ) 2 , CAS number: 13138-45-9.

[0042] Copper nitrate, molecular formula: Cu(NO 3 ) 2 , CAS number: 3251-23-8.

[0043] Potassium nitrate, molecular formula: KNO 3, CAS No.: 7757-79-1.

[0044] Calcium chloride, molecular formula: CaCl 2 , CAS No.: 10043-52-4.

[0045] Sodium chloride, molecular formula: NaCl, CAS No.: 7647-14-5.

[0046] Cerium nitrate, molecular formula: CeN 4 O 12 , CAS No.: 13093-17-9.

[0047] Magnesium chloride, molecular formula: MgCl 2 , CAS No.: 7786-30-3.

[0048] Indium nitrate, molecular formula: In(NO 3 ) 3 , CAS No.: 207398-97-8.

[0049] Cobalt nitrate hexahydrate, molecular formula: Co(NO 3 ) 2 ·6H 2 O, CAS No.: 10026-22-9.

[0050] Iron nitrate, molecular formula: Fe(NO 3 ) 3 ·9H 2 O, CAS No.: 7782-61-8.

[0051] Potassium dichromate, molecular formula: K 2 Cr 2 O 7 , CAS No.: 7778-50-9.

[0052] Vanadium chloride, molecular formula: VCl2, CAS No.: 10580-52-6.

[0053] Lithium chloride, molecular formula: LiCl, CAS No.: 7447-41-8.

[0054] Cesium chloride, molecular formula: CsCl, CAS No.: 7647-17-8.

[0055] Chromium chloride, molecular formula: Cr Cl 2 , CAS No.: 10049-05-5.

[0056] After understanding the relevant materials mentioned in the present invention, the following will further introduce in detail a method for recovering manganese from manganese-containing wastewater according to the present invention in combination with specific embodiments:

[0057] A glow plasma refers to a discharge phenomenon generated in a gas, also known as gas discharge. When the electric field strength in the gas is high enough, ionization occurs, converting gas molecules or atoms into positively charged ions and negatively charged electrons, forming a plasma. In the plasma, the collisions and recombination reactions between ions, electrons, and neutral particles release energy, forming a glow, which is the glow plasma.

[0058] The glow plasma technology is a new material synthesis, modification, and sewage treatment technology that has been widely applied in the fields of environmental remediation and material preparation in recent years. The glow plasma contains many high-energy particles and reactive species such as free radicals, which can remove various pollutants in the environment and has the advantages of being economical, practical, simple, and having no secondary pollution. The present invention uses the glow plasma technology to treat manganese-containing wastewater, and the technical solution adopted is as follows:

[0059] A method for recovering manganese from manganese-containing wastewater, comprising the following steps:

[0060] After the manganese-containing wastewater is treated by glow discharge plasma, a precipitate is generated;

[0061] The precipitate is separated, washed, and dried to obtain manganese dioxide.

[0062] Preferably, in the manganese-containing wastewater, there is at least one of the metals Li, Na, K, Cs, Mg, Ca, Al, In, Zn, La, Ce, Ni, Cu, Co, Fe, Cr, V.

[0063] Preferably, the pressure of the glow discharge plasma treatment is 100 - 1000 Pa

[0064] Preferably, the discharge atmosphere of the glow discharge plasma treatment is at least one of the following gases: air, or nitrogen, or oxygen, or argon, or helium.

[0065] Preferably, during the glow discharge plasma treatment process, the reaction temperature is room temperature.

[0066] Preferably, the discharge power supply for the glow discharge plasma treatment is an AC power supply, with a voltage of 5 - 20 kV, a current of 0.5 - 2 A, and a frequency of 50 Hz - 80 kHz.

[0067] Preferably, the treatment time of the glow discharge plasma treatment is 5 - 30 min.

[0068] Preferably, the precipitate separation process is centrifugation or filtration, the solvent used for washing is water or ethanol, and the drying process is room temperature drying or freeze drying.

[0069] A kind of manganese dioxide is obtained by recycling using the above method, and it is two-dimensional amorphous manganese dioxide nanoflowers.

[0070] The application of the above manganese dioxide in electrode materials.

[0071] Preferably, the manganese dioxide is used as an electrocatalytic anode material for catalyzing the oxidation reaction of 5-hydroxymethylfurfural; or as an electrocatalytic cathode material for catalyzing the nitrate reduction reaction.

[0072] Example 1.

[0073] Combined with Figure 1 , the specific operation steps are as follows:

[0074] (1) Place the manganese-containing wastewater solution in a quartz dish, then place it in the quartz tube of the plasma reactor, and pump the pressure in the quartz of the reactor to vacuum. Subsequently, introduce high-purity gas into the quartz tube.

[0075] The composition of the manganese-containing wastewater, in addition to Mn, may include 2-10 of the following metals, namely Li, Na, K, Cs, Mg, Ca, Al, In, Zn, La, Ce, Ni, Cu, Co, Fe, Cr, V.

[0076] The metal content of the manganese-containing wastewater is: 20 mM - 10 M.

[0077] The vacuum pressure of the reactor quartz tube is 100 - 1000 Pa.

[0078] The atmosphere is one of the following gases: air, nitrogen, oxygen, argon, helium, and the gas flow rate is 10 - 100 mL / min.

[0079] (2) At room temperature, turn on the power supply, adjust the discharge voltage to 5 - 20 kV, the discharge current is 0.5 - 2 A, the discharge frequency is 50 Hz - 80 kHz, excite the plasma and maintain continuous and stable discharge for 5 - 30 min, then turn off the AC power supply and cut off the power supply circuit. It is observed that brown precipitate is generated in the quartz dish, and the temperature is lower than 60 °C.

[0080] (3) Pour the wastewater treated by plasma in the reaction dish into a beaker, cool it naturally, centrifuge it, wash it with distilled water 5 times, and then freeze-dry the product for 12 h. After drying, manganese dioxide powder is obtained. The manganese dioxide is used as an electrocatalytic cathode material for catalyzing the nitrate reduction reaction.

[0081] Example 2: In-situ recovery of manganese element in solution using cobalt hydroxide as the substrate material

[0082] (1) Treat nickel foam (1.0 cm × 6.0 cm) with 1.0 M hydrochloric acid to remove surface oxides. Dissolve ammonium fluoride (4.0 mmol), urea (10 mmol), and cobalt nitrate hexahydrate (2.0 mmol) in 30 mL of ultrapure water. Subsequently, place the mixed solution and the treated nickel foam (2 pieces) into a 50 mL steel autoclave and maintain it at 120 °C for 12 h to obtain the Co nanowire precursor. Then use the Co precursor as a template for the growth of manganese dioxide.

[0083] (2) After placing the manganese-containing wastewater solution in a quartz dish and then in the quartz tube of the plasma reactor, subsequently place the nickel foam grown with cobalt hydroxide into the quartz dish containing the manganese-containing wastewater, and evacuate the pressure in the quartz of the reactor to 200 Pa. Then introduce high-purity gas into the quartz tube.

[0084] The composition of the manganese-containing wastewater, in addition to Mn, may include 2 - 10 of the following metals: Li, Na, K, Cs, Mg, Ca, Al, In, Zn, La, Ce, Ni, Cu, Co, Fe, Cr, V.

[0085] The pressure in the quartz tube of the reactor is 100 - 1000 Pa.

[0086] The atmosphere is at least one of the following gases: air, nitrogen, oxygen, argon, helium, and the gas flow rate is 10 - 100 mL / min.

[0087] (3) At room temperature, turn on the power supply, adjust the discharge voltage to 5 kV to 20 kV, the discharge current is 0.5 A to 2 A, the discharge frequency is 50 Hz - 80 kHz, excite the plasma and maintain continuous and stable discharge for 5 - 30 min, then turn off the AC power supply and cut off the power supply circuit. Brown substances are observed to be generated on the surface of the nickel foam, and the temperature is lower than 60 °C.

[0088] (4) After rinsing the nickel foam 5 times with deionized water, then place it in a vacuum drying oven and maintain it at 60 °C for 12 hours. Obtain the material with manganese dioxide loaded on cobalt hydroxide.

[0089] (5) Use the obtained material as an electrocatalytic anode material for catalyzing the oxidation reaction of 5-hydroxymethylfurfural.

[0090] Example 3.

[0091] The specific operation steps are as follows:

[0092] (1) First, prepare a 20 mM manganese ion solution.

[0093] (2) Place 8 mL of the manganese-containing solution in a quartz dish, then place the quartz dish in the quartz tube of the plasma reactor, and evacuate the pressure in the quartz of the reactor to a vacuum of 100 Pa. Subsequently, introduce high-purity argon gas into the quartz tube at a flow rate of 10 mL / min.

[0094] (3) At room temperature, turn on the AC power supply, adjust the discharge voltage to 5 kV, the discharge current to 0.5 A, and the discharge frequency to 50 kHz. Excite the plasma and maintain continuous and stable discharge, and the temperature during the treatment process is lower than 60 °C.

[0095] (4) Before each extraction of the solution, replenish and make up the volume of the solution in the quartz dish to the initial volume of 8 mL. Take 50 μL of the solution at different times for ICP testing.

[0096] The manganese ion contents at different times (0, 20, 30, 40, 50, 60, 120, 150, 180, 220, 260, 300, 360, 420 s) obtained by ICP testing are as follows Figure 2 shown. It can be seen from Figure 2 that the recovery rate can reach more than 95%.

[0097] (5) Pour the wastewater treated by plasma in the reaction dish into a beaker. The product after centrifugation and washing with ultrapure water 5 times is freeze-dried for 12 h to obtain manganese dioxide powder after drying.

[0098] (6) Conduct the following characterization tests on the obtained manganese dioxide powder, including: XRD, SEM, TEM, XPS, FTIR.

[0099] The XRD pattern of the prepared manganese dioxide is as shown in the appendix Figure 4 shown; the SEM image is as Figure 5 shown; the TEM image is as Figure 6 shown; the XPS pattern is as Figure 7 shown; the FTIR pattern is as Figure 8 shown.

[0100] It can be seen from Figures 4 - 8 that the recovered and prepared manganese dioxide has the morphological characteristics of two-dimensional nanoflowers and no obvious lattice fringes, and is an amorphous material.

[0101] (7) Calculate the purity of the prepared manganese dioxide powder by glow discharge mass spectrometry. The purity of manganese dioxide is 96%.

[0102] Example 4.

[0103] The specific operation steps are as follows:

[0104] (1) First, prepare simulated manganese-containing wastewater with a metal ion concentration of 20 mM, containing the following metals: Mn, Na, Co, Ca, Ni, K, La, Zn.

[0105] (2) Place 8 mL of the manganese-containing wastewater in a quartz dish, then place the quartz dish in the quartz tube of the plasma reactor, and evacuate the pressure in the quartz of the reactor to a vacuum of 100 Pa. Subsequently, introduce high-purity argon into the quartz tube at a flow rate of 10 mL / min.

[0106] (3) At room temperature, turn on the power supply, adjust the discharge voltage to 5 kV, the discharge current to 0.5 A, and the discharge frequency to 50 kHz. Excite the plasma and maintain continuous and stable discharge, then turn off the AC power supply and cut off the power supply circuit. Brown precipitate is observed to form in the quartz dish, and the temperature during the treatment process is lower than 60 °C.

[0107] (4) Before each extraction of the solution, replenish the solution in the quartz dish to a constant volume of 8 mL. Take 50 μL of the solution at different times for ICP testing.

[0108] The metal ion contents at different times (0, 40, 80, 200, 300 s) obtained by ICP testing, and the metal recovery amounts are obtained through ICP testing. The results are as Figure 3 shown. It can be Figure 3 seen that the recovery amount of manganese ions increases with time, and the recovery amount reaches 101 μmol at 300 s. The recovery amounts of other metal ions remain unchanged and are still retained in the original solution.

[0109] (5) Pour the wastewater treated by plasma in the reaction dish into a beaker. The product after centrifugation and washing with ultrapure water 5 times is freeze-dried for 12 h, and manganese dioxide powder is obtained after drying.

[0110] (6) Conduct XRD, SEM, TEM, XPS, and FTIR characterization tests on the obtained manganese dioxide powder. The test results are the same as those of the manganese dioxide in Example 3. The recovered and prepared manganese dioxide has the morphological characteristics of two-dimensional nanoflowers and no obvious lattice fringes, and is an amorphous material.

[0111] (7) Calculate the purity of the prepared manganese dioxide powder by glow discharge mass spectrometry. The purity of manganese dioxide is 94.8%.

[0112] Example 5.

[0113] The specific operation steps are as follows:

[0114] (1) First, prepare simulated manganese-containing wastewater with a metal content of 50 mM, containing the following metals: Mn, Li, Na, Ce, Co, Cr, V.

[0115] (2) Place 8 mL of manganese-containing wastewater in a quartz boat, then place the quartz dish in the quartz tube of the plasma reactor, and evacuate the pressure in the quartz of the reactor to a vacuum of 1000 Pa. Subsequently, introduce high-purity nitrogen into the quartz tube at a flow rate of 100 mL / min.

[0116] (3) At room temperature, turn on the power supply, adjust the discharge voltage to 20 kV, the discharge current to 2 A, and the discharge frequency to 80 kHz. Excite the plasma and maintain continuous and stable discharge for 5 min, then turn off the AC power supply and cut off the power supply circuit. Brown precipitate is observed to form in the quartz dish.

[0117] (4) Pour the wastewater treated by plasma in the reaction dish into a beaker. The product after centrifugation and washing with ultrapure water 5 times is freeze-dried for 12 h, and manganese dioxide powder is obtained after drying.

[0118] Example 6.

[0119] The specific operation steps are as follows:

[0120] (1) First, prepare simulated manganese-containing wastewater with a metal content of 10 M, containing the following metals: Mn, Na, Co, Mg, In, Al, Cu.

[0121] (2) Place 8 mL of manganese-containing wastewater in a quartz boat, then place the quartz dish in the quartz tube of the plasma reactor, and evacuate the pressure in the quartz of the reactor to a vacuum of 300 Pa. Subsequently, introduce high-purity oxygen into the quartz tube at a flow rate of 200 mL / min.

[0122] (3) At room temperature, turn on the power supply, adjust the discharge voltage to 5 kV, the discharge current to 0.2 A, and the discharge frequency to 50 Hz. Excite the plasma and maintain continuous and stable discharge for 30 min, then turn off the AC power supply and cut off the power supply circuit. Brown precipitate is observed to form in the quartz dish.

[0123] (4) Pour the wastewater treated by plasma in the reaction dish into a beaker. The product after centrifugation and washing with ultrapure water 5 times is freeze-dried for 12 h, and manganese dioxide powder is obtained after drying.

[0124] Example 7.

[0125] The operation steps of Example 7 are the same as those of Example 4, except that: the manganese-containing wastewater contains the following metals: Mn, Cs, Fe, Cu. The gas introduced into the quartz tube is air.

[0126] Example 8.

[0127] The operation steps of Example 8 are the same as those of Example 4, except that: the gas introduced into the quartz tube is a mixture of argon and nitrogen.

[0128] Example 9

[0129] The operating steps of Example 7 are the same as those of Example 4, except for step (3): the discharge voltage is adjusted to 10 kV, the discharge current is 1 A, the discharge frequency is 40 kHz, and the plasma is excited and continuously stable discharge is maintained for 10 min.

[0130] Brown precipitates are produced after the glow discharge plasma treatment of Examples 7 - 9. The manganese dioxide recovered from Examples 7 - 9 is characterized and tested, and the test results are the same as those of the manganese dioxide in Example 3. The recovered and prepared manganese dioxide has the morphological characteristics of two-dimensional nanoflowers and no obvious lattice fringes.

[0131] Comparative Example 1: Different plasma treatments

[0132] ① Atmospheric pressure spark discharge plasma

[0133] (1) First, prepare a manganese ion solution with a concentration of 20 mM.

[0134] (2) Place 200 mL of the manganese-containing solution in a quartz reactor and stir the reactor magnetically at a magnetic stirring speed of 500 r / min.

[0135] (3) Turn on the power supply, adjust the input voltage type to unipolar pulse voltage, adjust the discharge voltage to 15 kV, the discharge frequency to 1000 Hz, excite the plasma and maintain continuous stable discharge for 30 min, then turn off the pulse power supply and cut off the power supply circuit.

[0136] (4) Pour the wastewater treated by the spark discharge plasma in the quartz reactor into a beaker, and no precipitate is produced after standing.

[0137] (5) Take the manganese-containing solution before and after the plasma treatment for ICP testing, and the content of manganese ions does not change.

[0138] ② Dielectric barrier discharge plasma

[0139] (1) First, prepare a manganese ion solution with a concentration of 20 mM.

[0140] (2) Place 100 mL of the manganese-containing solution in a quartz reactor. Use an air compressor pump to pass air into the quartz reactor at a gas flow rate of 150 mL / min.

[0141] (3) Turn on the power supply, adjust the input voltage type to alternating current voltage, adjust the discharge voltage to 30 kV, the discharge current to 0.5 A, the discharge frequency to 40 kHz, excite the plasma and maintain continuous stable discharge for 30 min, then turn off the alternating current power supply and cut off the power supply circuit.

[0142] (4) Pour the manganese-containing solution treated by dielectric barrier discharge plasma in the quartz reactor into a beaker. After standing still, no precipitate is formed.

[0143] (5) Take the manganese-containing solutions before and after plasma treatment for ICP testing, and the content of manganese ions remains unchanged.

[0144] By comparing the example and Comparative Example 1, that is, comparing the treatment effects of glow discharge plasma, spark discharge plasma, and dielectric barrier discharge plasma on manganese-containing wastewater, only the manganese-containing wastewater treated by glow discharge plasma produced manganese dioxide precipitate.

[0145] Combining with the examples, the present invention discloses a method for selectively recovering manganese from manganese-containing wastewater by using glow plasma technology, and recovering and preparing two-dimensional amorphous manganese dioxide nanoflower materials and their electrochemical applications. The method includes the following steps: First, place the manganese-containing aqueous solution containing multiple metal ions in a quartz reaction dish, and then place the quartz reaction dish in a plasma quartz reaction tube; perform glow discharge plasma treatment; separate and wash the precipitate in the quartz reaction dish, and obtain a manganese dioxide product after drying; conduct electrochemical application tests on the manganese dioxide. The technical solution of the present invention has a simple recovery process, a short reaction time, and a recovery rate as high as 95%; the prepared manganese dioxide has a purity as high as 96%. The reaction conditions are mild and no high-temperature heating is required. Therefore, the technical solution of the present invention can be applied to general industrial manganese-containing wastewater containing multiple metal ions, has high selectivity for recovering manganese ions, does not require the addition of flocculants and precipitants, does not use strong acids or strong bases, avoids secondary pollution, the obtained recovered product manganese dioxide has a low impurity content, and at the same time has the advantage of being driven by clean energy electricity.

[0146] The above is only a preferred embodiment of the embodiments of the present invention, and does not impose any form of limitation on the embodiments of the present invention. Any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the embodiments of the present invention still fall within the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for recovering manganese from manganese-containing wastewater, characterized in that: The following steps are involved: After the manganese-containing wastewater is treated with glow discharge plasma, precipitation is produced; The precipitate is separated, washed and dried to obtain manganese dioxide.

2. The method according to claim 1, characterized in that The manganese-containing wastewater also contains at least one of the metals Li, Na, K, Cs, Mg, Ca, Al, In, Zn, La, Ce, Ni, Cu, Co, Fe, Cr, and V.

3. The method according to claim 1, characterized in that The pressure of the glow discharge plasma treatment is 100-1000Pa.

4. The method according to claim 1, characterized in that: The discharge atmosphere of the glow discharge plasma treatment is at least one of the following gases: air, nitrogen, oxygen, argon, or helium.

5. The method according to claim 1, characterized in that During the glow discharge plasma treatment process, the reaction temperature is room temperature and no heating is required.

6. The method according to claim 1, characterized in that The discharge power supply for the glow discharge plasma treatment is an AC power supply with a voltage of 5-20 kV, a current of 0.5-2 A, and a frequency of 50 Hz-80 kHz.

7. The method according to claim 1, characterized in that The glow discharge plasma treatment takes 5-30 minutes.

8. A manganese dioxide, characterized in that The method is adopted to recover the product according to any one of claims 1 to 7.

9. Use of the manganese dioxide according to claim 8 in electrode materials.

10. The use according to claim 9, characterized in that: The manganese dioxide is used as an electrocatalytic anode material to catalyze the oxidation reaction of 5-hydroxymethylfurfural; or is used as an electrocatalytic cathode material to catalyze the reduction reaction of nitrate.

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