Water treatment method, substance recovery method, resource recovery method, and resource recovery plant

Abstract

A water treatment method comprising electrochemically adsorbing, by using a working electrode formed of an organic redox substance having selective adsorption ability with respect to a specific substance dissolved in water to be treated, the specific substance on the working electrode, wherein the specific substance is ammonium ion, the organic redox substance is a polymer of 2,5-diamino-1,4-benzoquinone, and the ammonium ion is electrochemically adsorbed on the working electrode by applying, to the working electrode immersed in the water to be treated, a first prescribed voltage determined by using the minimum current value of a cyclic voltammogram with respect to the ammonium ion as an index.

Description

Water treatment method, substance recovery method, resource recovery method, and resource recovery plant

[0001] This invention relates to a water treatment method, a substance recovery method, a resource recovery method, and a resource recovery plant.

[0002] Ammonia is industrially essential as a raw material for fertilizers and chemical products, and demand is expected to increase further in the future due to global population growth. For example, existing manufacturing methods such as the Haber-Bosch process described in Patent Document 1 have the challenge of consuming large amounts of fossil fuels, and there is a need for environmentally friendly ammonia production and procurement methods.

[0003] Furthermore, it is known that once ammonia is released as exhaust gas or wastewater, it causes various environmental problems such as foul odors, PM2.5, eutrophication, and nitrate pollution. Currently, various types of wastewater containing ammonia, such as sewage, are treated by converting it to nitrogen and other substances through biological water treatment, but the ammonia in the wastewater is not effectively utilized as a resource. In addition, nitrous oxide (N) is released during the biological water treatment process, which is an environmental problem. ２ Because greenhouse gases such as oxygen are sometimes released, there is a need to establish nitrogen recycling technologies that recover and reuse ammonia in wastewater in order to create a sustainable society.

[0004] Furthermore, Non-Patent Document 1 discloses that the blue pigment Prussian blue can selectively recover ammonium ions. According to this method, there was a possibility that Prussian blue, which is a cyanide compound, would decompose during thermal desorption of ammonia and release hydrogen cyanide gas.

[0005] Special table 2022-552632 publication

[0006] T. Kawamoto et al., RSC Adv., 2018, 8, 34573-34581.

[0007] There is a need for a technology that can safely recover ammonia contained in wastewater without significantly increasing the environmental burden, without relying on conventional Haber-Bosch processes that consume large amounts of fossil fuels, such as those described in Patent Document 1, or ammonia recovery methods that may generate toxic gases, such as those described in Non-Patent Document 1.

[0008] The object of the present invention is to provide a water treatment method, a substance recovery method, a resource recovery method, and a resource recovery plant that can safely and efficiently recover ammonium ions contained in wastewater.

[0009] To achieve the above objective, the first characteristic configuration of the water treatment method according to the present invention is a water treatment method in which a working electrode composed of an organic oxidation-reduction substance having selective adsorption capacity for a specific substance dissolved in water to be treated is used to electrochemically adsorb the specific substance onto the working electrode, wherein the specific substance is ammonium ions, the organic oxidation-reduction substance is a polymer of 2,5-diamino-1,4-benzoquinone, and the ammonium ions are electrochemically adsorbed onto the working electrode by applying a first predetermined voltage, indicated by the minimum current value of a cyclic voltammogram for the ammonium ions, to the working electrode immersed in the water to be treated.

[0010] As a result of diligent research, the inventors of this invention discovered quinones as organic redox substances possessing selective adsorption capacity for ammonium ions dissolved in the water to be treated. It was hypothesized that by using such quinones as the electrode material to construct the working electrode, ammonium ions dissolved in the water to be treated could be selectively adsorbed. By applying a first predetermined voltage to the working electrode, using the minimum current value of the cyclic voltammogram for ammonium ions as an indicator, it becomes possible to selectively adsorb a specific substance from among multiple substances dissolved in the water to be treated onto the working electrode using an electrochemical reaction, i.e., a reduction reaction.

[0011] However, using quinones with low hydrophilicity results in a low reaction rate with water-soluble ammonium ions (amount of ammonia adsorbed per electrode material), making high adsorption efficiency unattainable. Therefore, by using the monomer of 2,5-diamino-1,4-benzoquinone, a highly hydrophilic quinone, as the working electrode and utilizing the electrochemical reaction between the ammonium ions and the working electrode as described above, it was found that ammonium ions could be selectively adsorbed onto the working electrode with high efficiency. However, the monomer of 2,5-diamino-1,4-benzoquinone is water-soluble, and the electrode material dissolves in the treated water during the ammonium ion recovery process, making ammonium ion adsorption difficult over time.

[0012] Therefore, the inventors of this application have found that polymerizing the monomer of 2,5-diamino-1,4-benzoquinone results in a material that is hydrophilic yet water-insoluble, enabling highly efficient adsorption of ammonium ions over a long period of time. By using such an organic oxidation-reduction substance as the working electrode, the organic oxidation-reduction substance does not dissolve in the treated water, and selective adsorption and recovery of ammonium ions dissolved in the treated water can be performed stably over a long period of time, enabling the recycling of ammonia, a valuable resource.

[0013] The second characteristic configuration, in addition to the first characteristic configuration described above, is that the first predetermined voltage applied to the working electrode is -0.9 ± 0.05 V vs. [Fe(CN) ６ ] ３－ / [Fe(CN) ６ ] ４－ The point is that...

[0014] By applying a first predetermined voltage to a working electrode using a polymer of 2,5-diamino-1,4-benzoquinone as an organic oxidation-reduction substance, ammonium ions can be selectively adsorbed from among multiple substances dissolved in the water to be treated.

[0015] The third characteristic configuration is that, in addition to the first characteristic configuration described above, a second predetermined voltage is applied to the working electrode that has been immersed in the recovery solution and adsorbed with ammonium ions, with the maximum current value of the cyclic voltammogram for the ammonium ions as an index, thereby electrochemically releasing the ammonium ions from the working electrode into the recovery solution.

[0016] By immersing the working electrode adsorbed with ammonium ions in the recovery solution and applying a second predetermined voltage with the maximum current value of the cyclic voltammogram for the ammonium ions as an index, a specific substance can be released from the working electrode into the recovery solution by utilizing an electrochemical reaction, that is, an oxidation reaction.

[0017] The fourth characteristic configuration is that, in addition to the third characteristic configuration described above, the second predetermined voltage applied to the working electrode is -0.15 ± 0.05 V vs. ６ ３－ / [Fe(CN) ６ ４－ This is the point.

[0018] By applying a second predetermined voltage to the working electrode using a polymer of 2,5-diamino-1,4-benzoquinone as the organic redox substance, ammonium ions can be released from the working electrode into the recovery solution.

[0019] The first characteristic configuration of the substance recovery method according to the present invention is a substance recovery method in which a working electrode composed of an organic redox substance having a selective adsorption ability for a specific substance dissolved in the treated water is used, and the specific substance is electrochemically adsorbed and recovered on the working electrode. The specific substance is ammonium ions, the organic redox substance is a polymer of 2,5-diamino-1,4-benzoquinone, and a first predetermined voltage with the minimum current value of the cyclic voltammogram for the ammonium ions as an index is applied to the working electrode immersed in the treated water, thereby electrochemically adsorbing the ammonium ions on the working electrode.

[0020] ​​The second characteristic configuration, in addition to the first characteristic configuration described above, is that the first predetermined voltage applied to the working electrode is -0.9 ± 0.05 V vs. [Fe(CN) ６ ３－ / [Fe(CN) ６ ４－ .

[0021] The third characteristic configuration, in addition to the first characteristic configuration described above, is that the working electrode immersed in the recovery solution and adsorbing the ammonium ions is applied with a second predetermined voltage based on the maximum current value of the cyclic voltammogram for the ammonium ions, thereby electrochemically releasing the ammonium ions from the working electrode into the recovery solution.

[0022] The fourth characteristic configuration, in addition to the third characteristic configuration described above, is that the second predetermined voltage applied to the working electrode is -0.15 ± 0.05 V vs. [Fe(CN) ６ ３－ / [Fe(CN) ６ ４－ .

[0023] The first characteristic configuration of the resource recovery method according to the present invention is a resource recovery method in which a working electrode using an organic redox substance having a selective adsorption ability for a specific substance from a plurality of types of substances dissolved in the water to be treated is immersed in the water to be treated, and the specific substance is electrochemically adsorbed on the working electrode, wherein the specific substance is ammonium ions, the organic redox substance is a polymer of 2,5-diamino-1,4-benzoquinone, and a first predetermined voltage based on the minimum current value of the cyclic voltammogram for the ammonium ions is applied to the working electrode immersed in the water to be treated, thereby electrochemically adsorbing the ammonium ions on the working electrode.

[0024] The second characteristic configuration, in addition to the first characteristic configuration described above, is that a second predetermined voltage based on the maximum current value of the cyclic voltammogram for the ammonium ions is applied to the working electrode immersed in the recovery solution and adsorbing the ammonium ions, thereby electrochemically releasing the ammonium ions from the working electrode.​​​​

[0025] The first characteristic configuration of the resource recovery plant according to the present invention is a resource recovery plant that selectively recovers a specific substance from water to be treated in which multiple types of substances including the specific substance are dissolved, comprising: a treatment tank filled with the water to be treated; a working electrode immersed in the treatment tank and using an organic oxidation-reduction substance having selective adsorption capacity for the specific substance; and a power supply device that applies a predetermined voltage to the working electrode, wherein the specific substance is ammonium ions, the organic oxidation-reduction substance is a polymer of 2,5-diamino-1,4-benzoquinone, and the ammonium ions are electrochemically adsorbed onto the working electrode by applying a first predetermined voltage, indicated by the minimum current value of a cyclic voltammogram for the ammonium ions, to the working electrode immersed in the water to be treated via the power supply device.

[0026] The second characteristic configuration, in addition to the first characteristic configuration described above, includes a processing tank filled with a recovery solution, a working electrode immersed in the processing tank and having the specific substance adsorbed onto it, and a second predetermined voltage applied to the working electrode, which is indicated by the maximum current value of the cyclic voltammogram for the ammonium ions, thereby electrochemically releasing the ammonium ions from the working electrode into the recovery solution.

[0027] As described above, the present invention makes it possible to provide a water treatment method, a substance recovery method, a resource recovery method, and a resource recovery plant that can safely and efficiently recover useful specific substances such as ammonia contained in wastewater.

[0028] Figure 1 is an explanatory diagram of the recovery mechanism of ammonia resources, which are useful specific substances from wastewater according to the present invention, to the working electrode. Figure 2 is an explanatory diagram of the release mechanism of ammonia resources, which are useful specific substances from wastewater according to the present invention, from the working electrode. Figure 3 is an explanatory diagram of the process of recovering ammonia by reduction reaction with an organic redox substance (polymer of 2,5-diamino-1,4-benzoquinone), and the mechanism of releasing the recovered ammonia by oxidation reaction. Figure 4 is an explanatory diagram of cyclic voltammograms for multiple types of cations of the organic redox substance (polymer of 2,5-diamino-1,4-benzoquinone). Figure 5 is an explanatory diagram of voltammetry. Figure 6 is a chemical formula showing the process of producing a monomer of 2,5-diamino-1,4-benzoquinone using the oxidation method. Figure 7 is a characteristic diagram of the monomer of 2,5-diamino-1,4-benzoquinone produced using the oxidation method and the reduction method, obtained by nuclear magnetic resonance (NMR). Figure 8 is a chemical formula showing the process of producing a polymer from the monomer 2,5-diamino-1,4-benzoquinone. Figure 9 is an explanatory diagram of the process conditions for polymerizing 2,5-diamino-1,4-benzoquinone using an acid catalyst. Figure 10 is a characteristic diagram obtained by FT-IR (Fourier transform infrared spectroscopy) of 2,5-diamino-1,4-benzoquinone polymerized using different acid catalysts. Figure 11 is a characteristic diagram of the weight loss method obtained by thermogravimetric analysis (TG method). Figure 12 is an explanatory diagram of a resource recovery plant showing the ammonium ion recovery process. Figure 13 is an explanatory diagram of a resource recovery plant showing the ammonium ion release process.

[0029] The following describes a water treatment method, a substance recovery method, a resource recovery method, and a resource recovery plant that can safely and efficiently recover ammonium ions as a useful specific substance contained in wastewater.

[0030] [Water Treatment Method] The water treatment method according to the present invention is a water treatment method that uses ammonia as the specific substance and a working electrode composed of an organic oxidation-reduction substance having selective adsorption capacity for the specific substance, to electrochemically adsorb the specific substance onto the working electrode, thereby recovering the specific substance dissolved in the wastewater to be treated.

[0031] An organic oxidation-reduction substance with selective adsorption capacity for specific substances dissolved in the water to be treated is used as the working electrode, and by utilizing the electrochemical reaction between the specific substance and the working electrode, the specific substance is selectively adsorbed onto the working electrode.

[0032] Specifically, as shown in Figure 5, a working electrode W, a reference electrode R, and a counter electrode C are immersed in a treatment tank 1 filled with water to be treated containing multiple substances including a specific substance. Each electrode is connected to a potentiostat, and a first predetermined voltage is applied to the working electrode W while monitoring the voltage of the reference electrode R, thereby electrochemically adsorbing the specific substance onto the working electrode. The first predetermined voltage is a voltage determined using the minimum current value of the cyclic voltammogram for the specific substance as an indicator.

[0033] A potentiostat is a device that controls a three-electrode cell consisting of a working electrode W, a counter electrode C, and a reference electrode R, allowing for arbitrary control of the electrode potential level regardless of the state of the electrolyte (water being treated). The working electrode W performs electron transfer with a specific substance. As the working electrode W, an organic oxidation-reduction substance with selective adsorption capacity for a specific substance is used. For example, it can be constructed by coating a carbon (glassy carbon substrate) with an organic oxidation-reduction substance using a binder (such as Nafion). The reference electrode R is a silver / silver chloride electrode or [Fe(CN)] which exhibits a stable electrode potential. ６ ] ３ - / [Fe(CN) ６ ] ４－ Electrodes are used. The counter electrode C is an electrode that feeds back the same current value to the system as that generated by the working electrode W, and a platinum coil is used for this purpose.

[0034] By applying a first predetermined voltage to the working electrode, which is indicated by the minimum current value of the cyclic voltammogram for a specific substance, the specific substance is selectively adsorbed onto the working electrode W from among multiple substances dissolved in the water to be treated, using electrochemical, or reduction, reactions.

[0035] When the specific substance is ammonia, a polymer of 2,5-diamino-1,4-benzoquinone can be suitably used as the organic oxidation-reduction substance. Furthermore, other quinones besides 2,5-diamino-1,4-benzoquinone can also be used, provided they are hydrophilic and insoluble polymers.

[0036] Figure 3 shows the chemical formula based on the redox reaction of the 2,5-diamino-1,4-benzoquinone polymer. The 2,5-diamino-1,4-benzoquinone polymer has the molecular formula (C ６ H ６ N ２ O ２ ) ｎ It is an organic compound represented by [formula]. It is a compound obtained by replacing the two hydrogen atoms bonded to the carbocyclic ring of 1,4-benzoquinone with amino groups.

[0037] As shown in Figure 4, ammonium ions NH ４ ＋ Potassium ion K ＋ Sodium ions Na ＋ Cyclic voltammetry is applied to the solution containing the dissolved material, sweeping the voltage applied to the working electrode W from the positive potential side to the negative potential side. When the voltage applied to the working electrode W reaches approximately -0.90V, a large current flows, and a reduction reaction proceeds in which ammonium ions are selectively attracted to the working electrode W. At approximately -1.0V, a large current flows, and a reduction reaction proceeds in which potassium ions are attracted to the working electrode W. At approximately -1.1V, a large current flows, and a reduction reaction proceeds in which sodium ions are attracted to the working electrode W.

[0038] As shown in Figure 1, a working electrode W made of 2,5-diamino-1,4-benzoquinone polymer is immersed in a treatment tank filled with wastewater to be treated, and a first predetermined voltage V1 of -0.9 ± 0.05 V vs. [Fe(CN) ６ ] ３－ / [Fe(CN) ６ ] ４－By applying a voltage near or to the vicinity of (see Figure 4) to the working electrode W, ammonium ions are selectively adsorbed onto the working electrode W. As described above, this value is determined using the minimum current value of the cyclic voltammogram for ammonium ions as an indicator. In other words, when the first predetermined voltage is applied, sodium ions and potassium ions are not actively adsorbed, so ammonium ions can be selectively adsorbed onto the working electrode W from wastewater containing multiple types of solutes.

[0039] As shown in Figure 2, a working electrode W with adsorbed ammonium ions is immersed in a treatment tank filled with the recovery solution, and a second predetermined voltage V2 is applied to the working electrode W, specifically -0.15 ± 0.05 V vs. [Fe(CN)], using the maximum current value of the cyclic voltammogram for ammonium ions as an indicator. ６ ] ３－ / [Fe(CN) ６ ] ４－ By applying a voltage near the working electrode W (see Figure 4), ammonium ions are released from the working electrode W electrochemically, i.e., by an oxidation reaction, into the recovery solution. Tap water, preferably pure water, can be used as the recovery solution.

[0040] By immersing the working electrode W, which has adsorbed ammonium ions, in the recovery solution and applying a second predetermined voltage V2, which is indicated by the maximum current value of the cyclic voltammogram for ammonium ions, ammonium ions can be released from the working electrode W into the recovery solution using an electrochemical, or oxidation, reaction.

[0041] By repeatedly performing a process in which ammonium ions are electrochemically adsorbed onto a working electrode W immersed in wastewater, and then electrochemically released from the working electrode W immersed in a recovery solution, ammonium ions can be efficiently recovered into the recovery solution, and a high concentration of ammonia water can be obtained by concentrating the recovery solution.

[0042] [Method for recovering substances] The method for recovering substances according to the present invention is a method for recovering substances by electrochemically adsorbing a specific substance onto a working electrode, which is composed of an organic oxidation-reduction substance having selective adsorption capacity for a specific substance dissolved in the water to be treated. The specific substance is ammonium ions, and the organic oxidation-reduction substance is a polymer of 2,5-diamino-1,4-benzoquinone. The method for recovering substances involves applying a first predetermined voltage, indicated by the minimum current value of a cyclic voltammogram for ammonium ions, to a working electrode immersed in the water to be treated, thereby electrochemically adsorbing ammonium ions onto the working electrode.

[0043] The first predetermined voltage applied to the working electrode is -0.9 ± 0.05 V vs. [Fe(CN) ６ ] ３－ / [Fe(CN) ６ ] ４－ It is preferable that this be the case.

[0044] The substance recovery method involves applying a second predetermined voltage, indicated by the maximum current value of the cyclic voltammogram for the specific substance, to a working electrode that has been immersed in the recovery solution and has adsorbed the specific substance, thereby electrochemically releasing the specific substance from the working electrode into the recovery solution.

[0045] The second predetermined voltage applied to the working electrode is -0.15 ± 0.05 V vs. [Fe(CN) ６ ] ３－ / [Fe(CN) ６ ] ４－ It is preferable that this be the case.

[0046] [Resource Recovery Method] The resource recovery method according to the present invention is a resource recovery method in which a working electrode made of an organic oxidation-reduction substance having selective adsorption capacity for a specific substance from among multiple types of substances dissolved in the water to be treated is immersed in the water to be treated, and the specific substance is electrochemically adsorbed onto the working electrode. The specific substance is ammonium ions, and the organic oxidation-reduction substance is a polymer of 2,5-diamino-1,4-benzoquinone. The resource recovery method is in which ammonium ions are electrochemically adsorbed onto the working electrode by applying a first predetermined voltage, which is indicated by the minimum current value of the cyclic voltammogram for ammonium ions, to the working electrode immersed in the water to be treated.

[0047] By applying a second predetermined voltage, indicated by the maximum current value of the cyclic voltammogram for ammonium ions, to the working electrode, which is immersed in the recovery solution and has adsorbed ammonium ions, ammonium ions are electrochemically released from the working electrode.

[0048] Figures 12 and 13 show a resource recovery plant that embodies the resource recovery method described above. The resource recovery plant selectively recovers a specific substance from treated water containing multiple types of dissolved substances, including the specific substance. The resource recovery plant comprises a treatment tank filled with treated water, a working electrode immersed in the treatment tank and using an organic oxidation-reduction substance with selective adsorption capacity for the specific substance, and a power supply device that applies a predetermined voltage to the working electrode.

[0049] The specific substance is ammonium ions, the organic oxidation-reduction substance is a polymer of 2,5-diamino-1,4-benzoquinone, and the resource recovery plant is configured to electrochemically adsorb ammonium ions onto the working electrode, which is immersed in the water to be treated, by applying a first predetermined voltage, indicated by the minimum current value of the cyclic voltammogram for ammonium ions, via a power supply device.

[0050] The resource recovery plant is configured to further include a treatment tank filled with a recovery solution, a working electrode immersed in the treatment tank and having a specific substance adsorbed onto it, and to electrochemically release ammonium ions from the working electrode into the recovery solution by applying a second predetermined voltage to the working electrode, which is indicated by the maximum current value of the cyclic voltammogram for the ammonium ions.

[0051] In the embodiments described above, sewage wastewater containing ammonium ions was used as an example of the water to be treated to which the present invention is applied. However, the water to be treated is not limited to sewage wastewater, and the invention can be applied to any wastewater containing ammonium ions that are to be recovered.

[0052] For example, it can be applied to wastewater containing high concentrations of ammonia, such as digestate from methane fermentation facilities, return water from the sludge treatment process at sewage treatment plants, wastewater from private factories, and livestock wastewater. It is preferable to fill the treatment tank with the separated liquid after solid-liquid separation of the digestate or wastewater using a membrane separator or the like.

[0053] In the embodiments described above, a water treatment method was described in which a specific substance is electrochemically adsorbed onto a working electrode using an organic oxidation-reduction substance having selective adsorption capacity for a specific substance. However, when the specific substance is electrochemically released from the working electrode on which it has been electrochemically adsorbed, the organic oxidation-reduction substance does not need to have selective release capacity for the specific substance.

[0054] In the embodiments described above, a water treatment method was explained in which a specific substance is electrochemically adsorbed onto a working electrode using a working electrode composed of a polymer of 2,5-diamino-1,4-benzoquinone, an organic redox substance having selective adsorption capacity for ammonium ions, which is a specific substance. However, it is also possible to selectively recover a specific substance by using a water treatment method in which a working electrode composed of an organic redox substance that does not have selective adsorption capacity for a specific substance but has selective release capacity for a specific substance, adsorbs multiple types of substances onto the organic redox substance, and electrochemically selectively releases the specific substance from the working electrode on which multiple types of substances have been electrochemically adsorbed.

[0055] [Method for producing polymer of 2,5-diamino-1,4-benzoquinone] The method for producing polymer of 2,5-diamino-1,4-benzoquinone, which is used as the organic redox substance described above, will now be explained. The method for producing the organic redox substance is a method for producing an organic redox substance having selective adsorption capacity for a specific substance dissolved in water to be treated, and comprises: a first step of generating a monomer of 2,5-diamino-1,4-benzoquinone from 2,5-diaminohydroquinone dihydrochloride using an oxidation method or a reduction method; and a second step of polymerizing the monomer of 2,5-diamino-1,4-benzoquinone using an acid catalyst.

[0056] Figure 6 shows the reaction equation for the first step using the oxidation method. In the first step, 2,5-diaminohydroquinone dihydrochloride is added while stirring water (100 ml) in an air atmosphere, followed by triethylamine (Et ３ Add N). No special heating or cooling is required in the first step; room temperature (18°C) is sufficient. After stirring for about 2 hours, the precipitated solid is filtered to obtain the monomer of 2,5-diamino-1,4-benzoquinone. The temperature of the aqueous solution can be in the range of 5 to 60°C, preferably 10 to 40°C, and the reaction time can be 1 to 24 hours.

[0057] The reduction method will be explained. In the first step, 2,3,5,6-tetrabromobenzoquinone is added while stirring 2-methoxyethyl acetate (40 ml) in an air atmosphere, and the mixture is heated to 60°C, and 25% ammonium aqueous solution (NH₃) is added. ４ Add OH. In the first step, it is preferable to heat at 80°C, stir for 2 hours, cool to room temperature (18°C), then add water (100 mL), and filter the precipitated solid to obtain 2,5-dibromo-3,6-diaminobenzoquinone. The temperature of the aqueous solution during stirring can be in the range of 60 to 100°C, preferably 70 to 80°C, and the reaction time can be 1 to 24 hours.

[0058] In the second step, no special heating or cooling is necessary; room temperature (18°C) is sufficient. After confirming that hydrogen absorption has stopped, triethylamine is added, followed by water (40 mL). The precipitated solid is filtered to obtain the monomer of 2,5-diamino-1,4-benzoquinone. The temperature of the aqueous solution can be in the range of 5 to 60°C, preferably 10 to 40°C, and the reaction time can be 1 to 24 hours.

[0059] Figure 7 shows the results of nuclear magnetic resonance (NMRI) measurements of the monomer 2,5-diamino-1,4-benzoquinone, a solid obtained in the first step using oxidation and reduction methods. The two peaks at 7-8 ppm are due to hydrogen atoms of the amino group. The single peak around 5.3 ppm is due to hydrogen atoms of benzoquinone. A peak due to impurities is observed in the reduction method, but no peak due to impurities is observed in the oxidation method.

[0060] The above example showed that employing the oxidation method yielded a higher purity 2,5-diamino-1,4-benzoquinone monomer than the reduction method. It is also possible to employ the reduction method after further investigation of the experimental conditions.

[0061] Figure 8 shows the reaction equation for the second step. In the second step, the monomer of 2,5-diamino-1,4-benzoquinone is added while stirring an organic solvent in the presence of an acid catalyst. Dimethylformamide (DMF), dimethyl sulfoxide (DMSO), or dimethylformamide (DMA) can be used as the organic solvent, and aluminum chloride or hydrochloric acid can be used as the acid catalyst. By using an acid catalyst, a solid insoluble in water, methanol, and the aforementioned organic solvents can be obtained.

[0062] Figure 9 shows the process conditions for polymerizing 2,5-diamino-1,4-benzoquinone obtained in the first step, using dimethylformamide (DMF) as the solvent and aluminum chloride or hydrochloric acid as the acid catalyst. In the experiment, the reaction temperature was room temperature (18°C), but it can be in the range of 0 to 100°C, preferably 10 to 50°C, and the reaction time can be in the range of 12 to 24 hours.

[0063] Figure 10 shows the characteristic maps obtained by Fourier transform infrared spectroscopy (FT-IR) of 2,5-diamino-1,4-benzoquinone polymerized using different acid catalysts. (1500 cm⁻¹) －１ The peak represents the stretching motion of the carbonyl group, at 1650 cm. －１ The peak represents the stretching motion of the C=C double bond, at 3400 cm. －１ The peak indicates the expansion and contraction of the amino group. 3150 cm－１ The C-H stretching motion of benzoquinone was observed, with a peak in 1, but not in 2 and 3.

[0064] Figure 11 shows the characteristic diagram of the weight loss process by thermogravimetric analysis (TG method). In sample 1, a mass loss occurs from around 220°C, indicating the decomposition of sample 1. In samples 2 and 3, a mass loss occurs from around 30°C, indicating the evaporation of the remaining solvent. From around 200°C, the mass loss occurs gradually, indicating the gradual decomposition of the polymer. The reason for the gradual mass loss is that the thermal durability of the sample improved due to polymerization.

[0065] The various embodiments described above are merely examples of the present invention, and the scope of the invention is not limited by this description. It goes without saying that the design can be modified as appropriate within the scope in which the effects and benefits of each invention are achieved.

[0066] 1: Processing tank W: Working electrode R: Reference electrode C: Counter electrode Bat: Power supply

Claims

1. A water treatment method comprising an organic oxidation-reduction substance having selective adsorption capacity for a specific substance dissolved in water to be treated, wherein the specific substance is ammonium ions, the organic oxidation-reduction substance is a polymer of 2,5-diamino-1,4-benzoquinone, and the ammonium ions are electrochemically adsorbed onto the working electrode by applying a first predetermined voltage, indicated by the minimum current value of a cyclic voltammogram for the ammonium ions, to the working electrode immersed in the water to be treated.

2. The first predetermined voltage applied to the working electrode is -0.9 ± 0.05 V vs. [Fe(CN) ６ ] ３－ / [Fe(CN) ６ ] ４－ The water treatment method according to claim 1.

3. The water treatment method according to claim 1, wherein the ammonium ions are electrochemically released from the working electrode into the recovery solution by applying a second predetermined voltage, which is indicated by the maximum current value of a cyclic voltammogram for the ammonium ions, to the working electrode, which is immersed in the recovery solution and has adsorbed the ammonium ions.

4. The second predetermined voltage applied to the working electrode is -0.15 ± 0.05 V vs. [Fe(CN) ６ ] ３－ / [Fe(CN) ６ ] ４－ The water treatment method according to claim 3.

5. A method for recovering a substance by electrochemically adsorbing a specific substance dissolved in water to be treated onto a working electrode composed of an organic oxidation-reduction substance having selective adsorption capacity for the specific substance, wherein the specific substance is ammonium ions, the organic oxidation-reduction substance is a polymer of 2,5-diamino-1,4-benzoquinone, and the method involves applying a first predetermined voltage, indicated by the minimum current value of a cyclic voltammogram for the ammonium ions, to the working electrode immersed in the water to be treated, thereby electrochemically adsorbing the ammonium ions onto the working electrode.

6. The first predetermined voltage applied to the working electrode is -0.9 ± 0.05 V vs. [Fe(CN) ６ ３－ / [Fe(CN) ６ ４－ , and the substance recovery method according to claim 5 ４－ which is such 7. A method for recovering a substance according to claim 5, wherein the working electrode, which is immersed in the recovery solution and has adsorbed ammonium ions, is subjected to a second predetermined voltage, which is indicated by the maximum current value of a cyclic voltammogram for the ammonium ions, thereby electrochemically releasing the ammonium ions from the working electrode into the recovery solution.

8. The second predetermined voltage applied to the working electrode is -0.15 ± 0.05 V vs. [Fe(CN) ６ ] ３－ / [Fe(CN) ６ ] ４－ The method for recovering a substance according to claim 7.

9. A resource recovery method comprising immersing a working electrode, which is an organic oxidation-reduction substance having selective adsorption capacity for a specific substance from among multiple types of substances dissolved in water to be treated, into the water to be treated, and electrochemically adsorbing the specific substance onto the working electrode, wherein the specific substance is ammonium ions, the organic oxidation-reduction substance is a polymer of 2,5-diamino-1,4-benzoquinone, and applying a first predetermined voltage, which is indicated by the minimum current value of a cyclic voltammogram for the ammonium ions, to the working electrode immersed in the water to be treated, thereby electrochemically adsorbing the ammonium ions onto the working electrode.

10. A resource recovery method according to claim 9, wherein the ammonium ions are electrochemically released from the working electrode by applying a second predetermined voltage, which is indicated by the maximum current value of a cyclic voltammogram for the ammonium ions, to the working electrode which is immersed in a recovery solution and has adsorbed the ammonium ions.

11. A resource recovery plant for selectively recovering a specific substance from treated water in which multiple types of substances including the specific substance are dissolved, comprising: a treatment tank filled with the treated water; a working electrode immersed in the treatment tank and using an organic oxidation-reduction substance having selective adsorption capacity for the specific substance; and a power supply device for applying a predetermined voltage to the working electrode, wherein the specific substance is ammonium ions, the organic oxidation-reduction substance is a polymer of 2,5-diamino-1,4-benzoquinone, and the resource recovery plant electrochemically adsorbs the ammonium ions onto the working electrode by applying a first predetermined voltage, indicated by the minimum current value of a cyclic voltammogram for the ammonium ions, to the working electrode immersed in the treated water via the power supply device.

12. A resource recovery plant according to claim 11, comprising: a treatment tank filled with a recovery solution; a working electrode immersed in the treatment tank and having the specific substance adsorbed on it; and a second predetermined voltage applied to the working electrode, with the maximum current value of a cyclic voltammogram for the ammonium ions as an indicator, thereby electrochemically releasing the ammonium ions from the working electrode into the recovery solution.

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