Nitrate adsorption reaction device as well as use method and application thereof

Abstract

The invention provides a nitrate adsorption reaction device and a using method and application thereof.The nitrate adsorption reaction device comprises a direct-current power source and a columnar reaction device, and the columnar reaction device comprises an electrode layer, an aluminum modified activated carbon layer and a conductive material penetrating through the aluminum modified activated carbon layer; the electrode layer and the aluminum modified activated carbon layer are insulated from each other; and the conductive material and the electrode layer are respectively connected with two electrodes of a direct-current power supply. According to the method, strong adsorption and electrochemical oxidation reduction are combined, so that the removal efficiency of nitrate is improved, and the risk of secondary pollution is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of wastewater treatment, specifically relates to the technical field of nitrate wastewater treatment, and in particular relates to a nitrate adsorption reaction device and a use method and application thereof. Background Art

[0002] Against the backdrop of increasingly severe water pollution problems, nitrate pollution has attracted much attention due to its harm to human health and the ecological environment. Traditional methods for nitrate removal include ion exchange and biological denitrification. The ion exchange method uses ion exchange resins to exchange nitrate ions, but there are problems with high resin costs and frequent regeneration. The biological denitrification method requires a specific microbial growth environment, harsh reaction conditions, long treatment cycles, and is sensitive to changes in water quality, which is subject to certain limitations in practical applications. These problems have prompted the development of more efficient, economical, environmentally friendly and adaptable nitrate degradation technologies. Electrochemical nitrate removal technology has achieved some results in laboratory research, and some small-scale equipment has also been put into use. The electric field is used to induce nitrate redox reactions, and the electrochemical principle is used to reduce nitrates to less toxic or harmless substances. This method has the advantages of faster reaction speed. In addition, some studies have focused on the modification and optimization of activated carbon. By changing the physicochemical properties of activated carbon, its adsorption capacity for nitrates is improved. This method has improved the nitrate removal effect to a certain extent.

[0003] CN110104833A discloses a water nitrate purifier and its application, including preparing biochar by grinding and sieving biomass, adding FeCl3 solution to prepare iron-modified biochar, and adding acrylamide, N,N-methylenebisacrylamide and ammonium persulfate to prepare water nitrate purifier. This patent improves the adsorption capacity of nitrate in the preparation and modification process of activated carbon, solves the problems of limited application and secondary pollution, but the selectivity of modified activated carbon for nitrate is relatively weak. In a complex water quality environment, it is easily affected by other ions, resulting in a decrease in the removal rate of nitrate. In addition, the regeneration problem of activated carbon has not been fundamentally solved, and the long-term operating cost is high.

[0004] CN110204062A discloses a nitrate removal reactor, which enables denitrifying Thiobacillus to denitrify nitrate in water by loading an activated carbon layer of denitrifying Thiobacillus in a micron membrane assembly of the nitrate removal reactor, and nitrate in water bodies at different heights can be purified by denitrifying Thiobacillus at the same time, and the nitrate removal efficiency is high. However, the nitrate removal effect of the nitrate removal reactor disclosed in the patent depends on the activity of denitrifying Thiobacillus, and the stability is poor.

[0005] CN116462280A discloses a preparation method and use of a novel ternary metal electrode, wherein the electrode is doped with metals Cu, Bi, and Pd. The prepared ternary metal Cu-Bi-Pd electrode has strong nitrate adsorption capacity, high catalytic activity, high nitrogen selectivity, stable corrosion resistance, and can be widely used in the treatment of nitrate wastewater. However, this patent pays too much attention to the innovation of electrode materials, but ignores the stability and cost control of the overall system. In practical applications, although the removal rate of nitrate is improved to a certain extent, the suppression of electrode side reactions and the improvement of current efficiency are not fully considered, resulting in excessive energy consumption, which is difficult to promote and apply on a large scale.

[0006] Therefore, it is of great significance to provide a nitrate removal reactor with high nitrate removal efficiency, low secondary pollution risk and cost-friendly. Summary of the invention

[0007] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a nitrate adsorption reaction device and its use method and application. The present invention designs the structure of the nitrate adsorption reaction device and performs aluminum modification on the activated carbon. The obtained aluminum-modified activated carbon layer serves as both an adsorbent and an anode in the adsorption process. The excellent adsorption performance and electrochemical oxidation-reduction conversion ability of the aluminum-modified activated carbon are utilized to combine strong adsorption with electrochemical oxidation-reduction, thereby enhancing the removal ability of nitrates and greatly improving the removal efficiency of nitrates. The nitrates are converted into nitrogen gas through electrochemical oxidation-reduction, thereby reducing the risk of secondary pollution.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a nitrate adsorption reaction device, the nitrate adsorption reaction device comprising a DC power supply and a columnar reaction device, the columnar reaction device comprising an electrode layer and a modified activated carbon layer arranged in sequence from top to bottom, the electrode layer and the modified activated carbon layer being insulated from each other;

[0010] The columnar reaction device further comprises a conductive material penetrating the aluminum-modified activated carbon layer, wherein the top of the conductive material is not higher than the top of the aluminum-modified activated carbon layer;

[0011] The conductive material and the electrode layer are respectively connected to two electrodes of a direct current power source.

[0012] The present invention designs the structure of the nitrate adsorption reaction device and performs aluminum modification on the activated carbon. The obtained aluminum-modified activated carbon layer is used as an adsorbent and an anode in the adsorption process at the same time. The excellent adsorption performance and electrochemical oxidation-reduction conversion ability of the aluminum-modified activated carbon are utilized to combine strong adsorption with electrochemical oxidation-reduction, thereby enhancing the removal ability of nitrates and greatly improving the removal efficiency of nitrates. The nitrates are converted into nitrogen gas through electrochemical oxidation-reduction, thereby reducing the risk of secondary pollution. By performing aluminum modification on the activated carbon, the adsorption ability of nitrates is enhanced, and the nitrates in the solution can be quickly enriched. At the same time, the electrochemical oxidation-reduction action causes the nitrates to be reduced to nitrogen gas at the cathode, thereby greatly improving the degradation efficiency of nitrates.

[0013] The present invention selects common and relatively cheap metal materials as electrodes and activated carbon as adsorption material and electrode material, which is conducive to cost saving.

[0014] Preferably, the electrode layer comprises a metal electrode.

[0015] Preferably, the electrode comprises a mesh metal electrode.

[0016] Preferably, the mesh metal electrode includes any one of a mesh titanium electrode, a mesh stainless steel electrode, a mesh copper electrode, a mesh silver electrode or a mesh aluminum electrode, or a combination of at least two thereof.

[0017] The purpose of providing the conductive material is to conduct current to the aluminum-modified activated carbon layer to achieve adsorption or desorption of nitrates and to achieve electrochemical oxidation-reduction reaction of nitrates between the aluminum-modified activated carbon layer and the electrode layer.

[0018] Preferably, the conductive material comprises a graphite rod, a carbon fiber rod, a carbon fiber filament or a titanium filament, and a typical but non-limiting combination comprises a combination of a graphite rod and a carbon fiber filament or a combination of a graphite rod and a titanium filament.

[0019] Preferably, the titanium wire comprises a spiral titanium wire.

[0020] Preferably, the surface of the spiral titanium wire includes a coating.

[0021] Preferably, the coating comprises any one of a metal oxide coating, a Pt coating or an Au coating, or a combination of at least two of them.

[0022] Preferably, the metal oxide coating includes any one of titanium oxide, ruthenium oxide or iridium oxide, or a combination of at least two of them.

[0023] In the present invention, the electrode layer and the aluminum-modified activated carbon layer are insulated from each other, including setting a gap between the electrode layer and the aluminum-modified activated carbon layer to prevent contact short circuit between the electrode layer and the aluminum-modified activated carbon layer, and the smaller the gap, the more conducive it is to reducing ohmic resistance and improving the removal efficiency of nitrates.

[0024] Preferably, an insulating layer is provided between the electrode layer and the aluminum-modified activated carbon layer.

[0025] The present invention utilizes an insulating layer to separate the electrode layer and the aluminum-modified activated carbon layer, aiming at reducing the gap between the electrode layer and the aluminum-modified activated carbon layer to reduce the resistance, but without contact to cause a short circuit.

[0026] The provision of the insulating layer can ensure mutual insulation between the electrode layer and the aluminum-modified activated carbon layer, and the insulating layer allows water to flow through the aluminum-modified activated carbon layer to reach the mesh electrode layer. The material of the insulating layer is not specifically limited.

[0027] Preferably, the insulating layer has a porous structure, preferably a honeycomb insulating material layer or a mesh insulating material layer.

[0028] Preferably, a water outlet is provided at the top of the columnar reaction device, and a water inlet is provided at the bottom of the columnar reaction device; the water inlet is connected to a water inlet unit, and the water outlet is connected to a water outlet unit.

[0029] Preferably, the water inlet unit comprises an adsorption water inlet device and a desorption water inlet device.

[0030] Preferably, the water outlet unit comprises an adsorption water outlet device and a desorption water outlet device.

[0031] Preferably, the adsorption water inlet device comprises an adsorption water inlet check valve, an adsorption water inlet pump station and an adsorption water inlet reservoir.

[0032] Preferably, the desorption water inlet device comprises a desorption water inlet check valve, a desorption water inlet pump station and a desorption water inlet reservoir.

[0033] Preferably, the adsorption water outlet device includes an adsorption water outlet water stop valve, an adsorption water outlet pump station and an adsorption water outlet reservoir.

[0034] Preferably, the desorption water outlet device comprises a desorption water outlet water stop valve, a desorption water outlet pump station and a desorption water outlet reservoir.

[0035] Preferably, the aluminum-modified activated carbon in the aluminum-modified activated carbon layer is obtained by the following preparation method, which comprises the following steps:

[0036] The activated carbon and the aluminum salt solution are mixed to obtain a mixed solution, the mixed solution is heated to obtain an aluminum-modified activated carbon precursor, and the aluminum-modified activated carbon precursor is calcined under an inert atmosphere to obtain the aluminum-modified activated carbon.

[0037] Preferably, the particle size of the activated carbon is less than 10 mm, for example, it can be 0.1 mm, 0.2 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm or 10 mm, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably less than 5 mm.

[0038] In the process of aluminum modification of activated carbon according to the present invention, it is necessary to ensure that the metal aluminum is fully loaded in the pores of the activated carbon and that the surface loading has no effect on the adsorption of nitrates.

[0039] Preferably, in the mixed liquid, according to the content of metallic aluminum, the mass ratio of the activated carbon to metallic aluminum is 1:(0.01-0.1), for example, it can be 1:0.01, 1:0.02, 1:0.03, 1:0.035, 1:0.04, 1:0.045, 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09 or 1:0.1, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably 1:(0.03-0.05).

[0040] Preferably, the aluminum salt solution comprises aluminum chloride and / or aluminum nitrate.

[0041] Preferably, in the aluminum salt solution, the molar ratio of aluminum chloride to aluminum nitrate is 1:(0.02-0.25), for example, it can be 1:0.02, 1:0.04, 1:0.06, 1:0.08, 1:0.1, 1:0.12, 1:0.14, 1:0.16, 1:0.18, 1:0.2, 1:0.21, 1:0.22, 1:0.23, 1:0.24 or 1:0.25, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0042] The method of mixing the dried activated carbon and the aluminum salt solution includes stirring.

[0043] Preferably, the stirring time is 5h-20h, for example, it can be 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h or 20h, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] Preferably, the temperature of the heated mixed liquid is 60°C-100°C, for example, it can be 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably 70°C-90°C.

[0045] In the present invention, the time for heating the mixed solution is based on the time for all the solvents to evaporate, and no specific limitation is given.

[0046] Preferably, the inert atmosphere comprises nitrogen and / or an inert gas.

[0047] Preferably, the inert atmosphere comprises nitrogen and / or argon.

[0048] Preferably, the calcination temperature is 300°C-600°C, for example, it can be 300°C, 350°C, 400°C, 450°C, 500°C, 550°C or 600°C, including but not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 400°C-500°C.

[0049] In a second aspect, the present invention provides a method for using the nitrate adsorption reaction device according to the first aspect, the method comprising:

[0050] When the adsorption reaction is carried out, the nitrate wastewater flows in from the bottom of the columnar reaction device, passes through the aluminum-modified activated carbon layer and the electrode layer, and flows out from the top of the columnar reaction device.

[0051] When the desorption reaction is carried out, the desorption liquid flows in from the bottom of the columnar reaction device, passes through the aluminum-modified activated carbon layer and the electrode layer, and flows out from the top of the columnar reaction device.

[0052] In the present invention, when the nitrate adsorption reaction device performs an adsorption reaction, the electrode layer is connected to the negative electrode of the DC power supply, and the conductive material is connected to the positive electrode of the DC power supply.

[0053] During the adsorption reaction, the electrode layer is connected to the negative electrode of the DC power supply as a cathode, and the conductive material is connected to the positive electrode to conduct the current to the aluminum-modified activated carbon layer. The aluminum-modified activated carbon layer acts as an anode to achieve the adsorption of nitrates. When the unadsorbed nitrates flow to the surface of the electrode layer, an electrochemical oxidation-reduction reaction occurs and they are converted into nitrogen, thereby achieving the electrochemical removal of nitrates.

[0054] When the nitrate adsorption reaction device performs a desorption reaction, the electrode layer is connected to the positive electrode of the DC power supply, and the conductive material is connected to the negative electrode of the DC power supply.

[0055] During the desorption process, the electrode layer is connected to the positive electrode of the DC power supply, and the conductive material is connected to the negative electrode, so that the current is conducted to the aluminum-modified activated carbon layer to desorb the nitrate adsorbed in the aluminum-modified activated carbon layer, thereby realizing the recycling of the aluminum-modified activated carbon layer.

[0056] Preferably, the DC power supply is a DC power supply with adjustable positive and negative poles.

[0057] Preferably, the voltage of the DC power supply is 2V-15V, for example, it can be 2V, 3V, 4, 5V, 6V, 7V, 8V, 9V, 10V, 11V, 12V, 13V, 14V or 15V, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0058] In the present invention, the DC power supply is set as a DC power supply with adjustable positive and negative poles. By converting the positive and negative poles of the DC power supply, the conversion of the adsorption and desorption processes is achieved, thereby improving the working efficiency of the nitrate adsorption reaction device.

[0059] Preferably, the method of use further comprises adjusting the Cl content in the nitrate wastewater before the nitrate wastewater enters the nitrate adsorption reaction device. - The mass concentration can be between 20 mg / L and 100 mg / L, for example, 20 mg / L, 30 mg / L, 40 mg / L, 50 mg / L, 60 mg / L, 70 mg / L, 80 mg / L, 90 mg / L or 100 mg / L, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably 40 mg / L-60 mg / L.

[0060] In the present invention, during the adsorption process, nitrate is reduced to ammonia under the action of electrochemical oxidation-reduction, and Cl in the nitrate wastewater is reduced to ammonia. - It can promote the further reaction of ammonia to produce nitrogen.

[0061] Preferably, the desorption liquid is a chloride salt solution.

[0062] Preferably, the chloride salt solution comprises any one of NaCl, KCl or NH4Cl or a combination of at least two thereof, and typical but non-limiting combinations include a combination of NaCl and KCl, a combination of NaCl and NH4Cl or a combination of KCl and NH4Cl.

[0063] Preferably, the chloride salt solution contains Cl -The mass concentration is 0.5g / L-10g / L, for example, it can be 0.5g / L, 1g / L, 1.5g / L, 2g / L, 2.5g / L, 3g / L, 3.5g / L, 4g / L, 4.5g / L, 5g / L, 5.5g / L, 6g / L, 6.5g / L, 7g / L, 7.5g / L, 8g / L, 8.5g / L, 9g / L, 9.5g / L or 10g / L, including but not limited to the listed values, other unlisted values ​​within the numerical range are also applicable, preferably 4g / L-8g / L.

[0064] In a third aspect, the present invention provides an application of the nitrate adsorption reaction device as described in the first aspect, wherein the nitrate adsorption reaction device is applied to remove nitrate from wastewater.

[0065] The nitrate adsorption reaction device provided by the present invention is divided into two processes, adsorption and desorption, during application, to achieve the recycling of the nitrate adsorption reaction device, wherein:

[0066] During adsorption, the electrode layer is connected to the negative electrode of the DC power supply as the cathode, and the conductive material is connected to the positive electrode of the DC power supply to conduct the current to the aluminum-modified activated carbon layer. The aluminum-modified activated carbon layer serves as the anode. The adsorption water inlet check valve is opened, and the pretreated nitrate wastewater enters the columnar reaction device from the adsorption water inlet reservoir under the action of the adsorption water inlet pump station, flows from bottom to top through the aluminum-modified activated carbon layer, and reaches the electrode layer. The nitrate in the wastewater is fully adsorbed by the aluminum-modified activated carbon, and the unadsorbed nitrate is electrochemically oxidized and reduced to ammonia in the electrode layer and is converted into ammonia in the Cl - It is further converted into nitrogen under the action of nitrate removal. After the water reaches the standard, the water stop valve is opened and enters the adsorption water reservoir through the adsorption water pump station.

[0067] During desorption, the electrode layer is connected to the positive pole of the DC power supply as the anode, and the conductive material is connected to the negative pole of the DC power supply to conduct the current to the aluminum-modified activated carbon layer, and the aluminum-modified activated carbon is used as the cathode, that is, the relative adsorption process, the electrode is reversed. The desorption water inlet check valve is opened, and the desorption liquid enters the columnar reaction device from the desorption water inlet reservoir under the action of the desorption water inlet pump station, flows from bottom to top through the aluminum-modified activated carbon layer, reaches the electrode layer, and the nitrate adsorbed by the aluminum-modified activated carbon is separated from the modified activated carbon and enters the desorption liquid. After desorption is completed, the desorption water outlet check valve is opened, and the desorbed nitrate enters the desorption water outlet reservoir with the desorption liquid through the desorption water outlet pump station.

[0068] The present invention can complete the transition between adsorption and desorption by reversing the electrode, thereby realizing the recycling of the nitrate adsorption reaction device. The desorption liquid with high concentration of nitrate obtained by desorption can be reused for a second time, and can also be used to pretreat nitrate wastewater.

[0069] Compared with the prior art, the present invention has the following beneficial effects:

[0070] (1) The present invention designs the structure of the nitrate adsorption reaction device, and the transition between adsorption and desorption can be completed by electrode reversal, thereby realizing the recycling of the nitrate adsorption reaction device.

[0071] (2) The present invention modifies activated carbon with aluminum, and the obtained aluminum-modified activated carbon layer is used as an adsorbent and an anode in the adsorption process. The excellent adsorption performance and electrochemical oxidation-reduction conversion capacity of the aluminum-modified activated carbon are utilized to combine strong adsorption with electrochemical oxidation-reduction, thereby enhancing the removal capacity of nitrates and greatly improving the removal efficiency of nitrates. The nitrates are converted into nitrogen gas through electrochemical oxidation-reduction, thereby reducing the risk of secondary pollution. By modifying the activated carbon with aluminum, the adsorption capacity of nitrates is enhanced, and the nitrates in the solution can be quickly enriched. At the same time, the electrochemical oxidation-reduction effect causes the nitrates to be reduced to nitrogen gas at the cathode, greatly improving the degradation efficiency of nitrates. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 It is a schematic diagram of the structure of the nitrate adsorption reaction device in Example 1 of the present invention.

[0073] Among them, 1-DC power supply; 2-mesh titanium electrode; 3-aluminum modified activated carbon layer; 4-spiral titanium wire conductive material; 5-mesh insulating material layer; 6-adsorption water inlet stop valve; 7-desorption water inlet stop valve; 8-adsorption water outlet stop valve; 9-desorption water outlet stop valve; 10-adsorption water inlet pump station; 11-desorption water inlet pump station; 12-adsorption water outlet pump station; 13-desorption water outlet pump station; 14-adsorption water inlet reservoir; 15-desorption water inlet reservoir; 16-adsorption water outlet reservoir; 17-desorption water outlet reservoir.

[0074] Figure 2 Adsorption curves of the nitrate adsorption reaction devices provided for Example 1, Comparative Example 2, Comparative Example 4 and Comparative Example 5.

[0075] Figure 3 Adsorption curves of the nitrate adsorption reaction devices provided in Example 1, Comparative Example 1 and Comparative Example 3. DETAILED DESCRIPTION

[0076] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0077] Example 1

[0078] This embodiment provides a nitrate adsorption reaction device, the structure of which is as follows: Figure 1 As shown, it includes a mesh titanium electrode 2 and an aluminum-modified activated carbon layer 3 arranged in sequence from top to bottom, and a spiral titanium wire conductive material 4 penetrating the aluminum-modified activated carbon layer; the spiral titanium wire conductive material 4 and the mesh titanium electrode 2 are respectively connected to two electrodes of a DC power supply 1. The top of the spiral titanium wire conductive material 4 is flush with the top of the aluminum-modified activated carbon layer 3, and a mesh insulating material layer 5 is arranged between the aluminum-modified activated carbon layer and the mesh titanium electrode.

[0079] The adsorption water inlet device includes an adsorption water inlet check valve 6, an adsorption water inlet pump station 10 and an adsorption water inlet reservoir 14; the adsorption water outlet device includes an adsorption water outlet check valve 8, an adsorption water outlet pump station 12 and an adsorption water outlet reservoir 16; the desorption water inlet device includes a desorption water inlet check valve 7, a desorption water inlet pump station 11 and a desorption water inlet reservoir 15; the desorption water outlet device includes a desorption water outlet check valve 9, a desorption water outlet pump station 13 and a desorption water outlet reservoir 17.

[0080] During the application process, the transition between adsorption and desorption is completed by reversing the electrodes, where:

[0081] During adsorption, the mesh titanium electrode 2 is connected to the negative electrode of the DC power supply 1 as a cathode, and the spiral titanium wire conductive material 4 is connected to the positive electrode of the DC power supply 1 to conduct current to the aluminum-modified activated carbon layer 3. The aluminum-modified activated carbon layer 3 serves as an anode. The adsorption water inlet stop valve 6 is opened, and the pretreated nitrate wastewater enters the columnar reaction device from the adsorption water inlet reservoir 14 under the action of the adsorption water inlet pump station 10, flows from bottom to top through the anode layer of the aluminum-modified activated carbon layer, and reaches the mesh titanium electrode. The nitrate in the wastewater is fully adsorbed by the aluminum-modified activated carbon, and the unadsorbed nitrate is electrochemically oxidized and reduced to ammonia in the titanium electrode layer, and is converted into ammonia in the Cl - After the water has been nitrate-removed and reaches the standard, the adsorption water stop valve 8 is opened and the water enters the adsorption water reservoir 16 through the adsorption water pump station 12.

[0082] During desorption, the mesh titanium electrode 2 is connected to the positive electrode of the DC power supply 1, and the spiral titanium wire conductive material 4 is connected to the negative electrode of the DC power supply 1, and the current is conducted to the aluminum-modified activated carbon layer 3. The desorption water inlet stop valve 7 is opened, and the desorption liquid enters the columnar reaction device from the desorption water inlet reservoir 15 under the action of the desorption water inlet pump station 11, flows from bottom to top through the aluminum-modified activated carbon layer, reaches the mesh titanium electrode, and the nitrate adsorbed by the aluminum-modified activated carbon is separated from the modified activated carbon and enters the desorption liquid. After desorption is completed, the desorption water outlet stop valve 9 is opened, and the desorbed nitrate enters the desorption water outlet reservoir 17 with the desorption liquid through the desorption water outlet pump station 13.

[0083] In this embodiment, the preparation method of aluminum-modified activated carbon includes:

[0084] 1) Grind the dried activated carbon and pass it through a 4-mesh sieve to control the particle size to less than 5 mm;

[0085] 2) mixing the ground activated carbon with an aluminum salt solution having a molar ratio of aluminum chloride to aluminum nitrate of 1:0.11 to obtain a mixed solution, wherein the mass ratio of activated carbon to metal aluminum in the mixed solution is 1:0.04 based on the content of metal aluminum;

[0086] 3) The mixed solution is stirred at room temperature for 10 hours, and then dried by evaporation concentration at 80° C. to obtain a dry powder, so that the aluminum salt remains in the pores of the activated carbon.

[0087] 4) The dried powder is placed in a tubular furnace and calcined under a nitrogen environment at a calcination temperature of 450° C. After calcination, aluminum-modified activated carbon is obtained.

[0088] Example 2

[0089] This embodiment provides a nitrate adsorption reaction device, which is the same as Example 1 except that the mesh titanium electrode is a mesh copper electrode, the conductive material is a graphite rod, and the preparation method of aluminum-modified activated carbon is different from that of Example 1.

[0090] In this embodiment, the preparation method of aluminum-modified activated carbon includes:

[0091] 1) Grind the dried activated carbon and pass it through a 3-mesh sieve to control the particle size to less than 6 mm;

[0092] 2) mixing the ground activated carbon with an aluminum salt solution having a molar ratio of aluminum chloride to aluminum nitrate of 1:0.25 to obtain a mixed solution, wherein the mass ratio of activated carbon to metal aluminum in the mixed solution is 1:0.1 based on the content of metal aluminum;

[0093] 3) The mixed solution is stirred at room temperature for 20 hours, and then dried by evaporation concentration at 100° C. to obtain a dry powder, so that the aluminum salt remains in the pores of the activated carbon.

[0094] 4) The dried powder is placed in a tubular furnace and calcined in a nitrogen environment at a calcination temperature of 600° C. After calcination, aluminum-modified activated carbon is obtained.

[0095] Example 3

[0096] This embodiment provides a nitrate adsorption reaction device, which is the same as Example 1 except that the insulating material layer is a porous insulating material layer and the preparation method of aluminum-modified activated carbon is different from that of Example 1.

[0097] In this embodiment, the preparation method of aluminum-modified activated carbon includes:

[0098] 1) Grind the dried activated carbon and pass it through a 5-mesh sieve to control the particle size to be less than 4 mm;

[0099] 2) mixing the ground activated carbon with an aluminum salt solution having a molar ratio of aluminum chloride to aluminum nitrate of 1:0.2 to obtain a mixed solution, wherein the mass ratio of the activated carbon to the metal aluminum in the mixed solution is 1:0.05 based on the content of metal aluminum;

[0100] 3) The mixed solution is stirred at room temperature for 15 hours, and then dried by evaporation concentration at 90° C. to obtain a dry powder, so that the aluminum salt remains in the pores of the activated carbon.

[0101] 4) The dried powder is placed in a tubular furnace and calcined under a nitrogen environment at a calcination temperature of 500° C. After calcination, aluminum-modified activated carbon is obtained.

[0102] Example 4

[0103] This embodiment provides a nitrate adsorption reaction device, which is the same as Example 1 except that the mesh titanium electrode is a mesh aluminum electrode, the conductive material is carbon fiber filaments, and the preparation method of aluminum-modified activated carbon is different from that of Example 1.

[0104] In this embodiment, the preparation method of aluminum-modified activated carbon includes:

[0105] 1) Grind the dried activated carbon and pass it through a 7-mesh sieve to control the particle size to less than 3 mm;

[0106] 2) mixing the ground activated carbon with an aluminum salt solution having a molar ratio of aluminum chloride to aluminum nitrate of 1:0.08 to obtain a mixed solution, wherein the mass ratio of activated carbon to metal aluminum in the mixed solution is 1:0.03 based on the content of metal aluminum;

[0107] 3) The mixed solution is stirred at room temperature for 8 hours, and then dried by evaporation concentration at 70° C. to obtain a dry powder, so that the aluminum salt remains in the pores of the activated carbon.

[0108] 4) The dried powder is placed in a tubular furnace and calcined in a nitrogen environment at a calcination temperature of 400° C. After calcination, aluminum-modified activated carbon is obtained.

[0109] Example 5

[0110] This embodiment provides a nitrate adsorption reaction device, in which the conductive material is a carbon fiber rod, and the preparation method of the aluminum-modified activated carbon is different from that in Example 1, and the rest is the same as that in Example 1.

[0111] In this embodiment, the preparation method of aluminum-modified activated carbon includes:

[0112] 1) Grind the dried activated carbon and pass it through a 10-mesh sieve to control the particle size to less than 2 mm;

[0113] 2) mixing the ground activated carbon with an aluminum salt solution having a molar ratio of aluminum chloride to aluminum nitrate of 1:0.02 to obtain a mixed solution, wherein the mass ratio of activated carbon to metal aluminum in the mixed solution is 1:0.01 based on the content of metal aluminum;

[0114] 3) The mixed solution is stirred at room temperature for 5 hours, and then dried by evaporation concentration at 60° C. to obtain a dry powder, so that the aluminum salt remains in the pores of the activated carbon.

[0115] 4) The dried powder is placed in a tubular furnace and calcined under a nitrogen environment at a calcination temperature of 300° C. After calcination, aluminum-modified activated carbon is obtained.

[0116] Example 6

[0117] This embodiment provides a nitrate adsorption reaction device, which is the same as Embodiment 1 except that the molar ratio of aluminum chloride to aluminum nitrate is adjusted to 1:0.3 during the preparation of aluminum-modified activated carbon.

[0118] Example 7

[0119] This embodiment provides a nitrate adsorption reaction device, which is the same as that of Embodiment 1 except that the mass ratio of activated carbon to metal aluminum in the mixed solution is adjusted to 1:0.15 during the preparation of aluminum-modified activated carbon.

[0120] Comparative Example 1

[0121] This comparative example provides a nitrate adsorption reaction device, which is the same as Example 1 except that an equimolar amount of aluminum chloride is used to replace aluminum nitrate during the preparation of aluminum-modified activated carbon.

[0122] Comparative Example 2

[0123] This comparative example provides a nitrate adsorption reaction device, which is the same as Example 1 except that unmodified activated carbon with equivalent particle size is used to replace the aluminum-modified activated carbon in equal volume.

[0124] Comparative Example 3

[0125] This comparative example provides a nitrate adsorption reaction device, which is the same as Example 1 except that in the preparation process of aluminum-modified activated carbon, aluminum chloride and aluminum nitrate are replaced by equimolar amounts of ferric chloride and ferric nitrate to prepare iron-modified activated carbon.

[0126] Comparative Example 4

[0127] This comparative example provides a nitrate adsorption reaction device, which is the same as Example 1 except that the DC power supply is not powered.

[0128] Comparative Example 5

[0129] This comparative example provides a nitrate adsorption reaction device, which is the same as Example 1 except that unmodified activated carbon with equivalent particle size is used to replace the aluminum-modified activated carbon in equal volume and the DC power supply is not energized.

[0130] Performance Testing:

[0131] The present invention selects nitrate wastewater with an N element concentration of 15 mg / L as the treatment object, and tests the adsorption and degradation capacity of nitrates by the nitrate adsorption reaction devices provided in all embodiments of the present invention and the comparative examples. It should be noted that the present invention selects nitrate wastewater with an N element concentration of 15 mg / L as the treatment object, the purpose of which is to provide a unified evaluation standard for the adsorption capacity of the nitrate adsorption reaction devices provided in all embodiments and the comparative examples, and it is not used as a limitation on the degradation capacity of nitrate wastewater by the nitrate adsorption reaction device in the present invention.

[0132] Using NaCl solution to adjust Cl in nitrate wastewater - The mass concentration was adjusted to 50 mg / L, the voltage of the DC power supply was set to 5 V, the current was about 4 mA to 5 mA, and the empty bed contact time was 8 min.

[0133] Taking 10% of the nitrate concentration in the pretreated nitrate wastewater as the breakthrough point, the test results are shown in Table 1.

[0134] Table 1

[0135] Activated carbon adsorption breakthrough point / BV in nitrate adsorption reaction device Example 1 82 Example 2 85 Example 3 80 Example 4 81 Example 5 79 Example 6 58 Example 7 56 Comparative Example 1 54 Comparative Example 2 19 Comparative Example 3 27 Comparative Example 4 45 Comparative Example 5 10

[0136] According to the data results in Table 1, it can be found that the nitrate adsorption reaction device provided by the present invention combines aluminum-modified activated carbon with electrochemical redox reaction, and the adsorption penetration effect is significantly improved compared with the adsorption of nitrate by activated carbon alone, and when the penetration point is reached, the nitrate removal rate can still reach 99%, which is almost completely adsorbed and removed, greatly improving the removal efficiency of nitrate and achieving efficient removal of nitrate.

[0137] According to the data results of Example 1 and Comparative Examples 1 to 3, the present invention greatly increases the active sites for adsorbing nitrates in the activated carbon by selecting aluminum to modify the activated carbon, and uses aluminum chloride and aluminum nitrate to modify the activated carbon at the same time, thereby achieving more efficient removal of nitrates. However, according to the data results of Example 1 and Example 7, when too much aluminum salt is added, that is, when the loading amount of metallic aluminum in the obtained aluminum-modified activated carbon is too much, it will block the adsorption of nitrates by the active sites, thereby affecting the adsorption effect of nitrates.

[0138] According to the data results of Example 1 and Comparative Example 4, the present invention significantly enhances the degradation effect of nitrate under the action of electrochemical redox reaction and increases the adsorption penetration points of activated carbon. At the same time, according to the data results of Example 1 and Comparative Example 2, the adsorption sites of the activated carbon modified by aluminum in the present invention are significantly increased compared with the unmodified activated carbon, achieving efficient adsorption and removal of nitrate.

[0139] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A nitrate adsorption reaction device, characterized in that: The nitrate adsorption reaction device comprises a DC power supply and a columnar reaction device, wherein the columnar reaction device comprises an electrode layer and an aluminum-modified activated carbon layer arranged in sequence from top to bottom, and the electrode layer and the aluminum-modified activated carbon layer are insulated from each other; The columnar reaction device further comprises a conductive material penetrating the aluminum-modified activated carbon layer, wherein the top of the conductive material is not higher than the top of the aluminum-modified activated carbon layer; The conductive material and the electrode layer are respectively connected to two electrodes of a direct current power source.

2. The nitrate adsorption reactor according to claim 1, characterized in that: The electrode layer includes a metal electrode; Preferably, the electrode comprises a mesh metal electrode; Preferably, the mesh metal electrode includes any one of a mesh titanium electrode, a mesh stainless steel electrode, a mesh copper electrode, a mesh silver electrode or a mesh aluminum electrode, or a combination of at least two thereof; Preferably, the conductive material comprises a graphite rod, a carbon fiber rod, a carbon fiber wire or a titanium wire; Preferably, the titanium wire comprises a spiral titanium wire; Preferably, the surface of the titanium wire includes a coating; Preferably, the coating comprises any one of a metal oxide coating, a Pt coating or an Au coating, or a combination of at least two thereof; Preferably, the metal oxide coating includes any one of titanium oxide, ruthenium oxide or iridium oxide, or a combination of at least two of them.

3. The nitrate adsorption reaction device according to claim 1 or 2, characterized in that: An insulating layer is provided between the electrode layer and the aluminum-modified activated carbon layer; Preferably, the insulating layer has a porous structure; Preferably, the insulating layer is a honeycomb insulating layer or a mesh insulating layer.

4. The nitrate adsorption reaction device according to any one of claims 1 to 3, characterized in that: The top of the columnar reaction device is provided with a water outlet, and the bottom of the columnar reaction device is provided with a water inlet; the water inlet is connected to the water inlet unit, and the water outlet is connected to the water outlet unit; Preferably, the water inlet unit comprises an adsorption water inlet device and a desorption water inlet device; Preferably, the water outlet unit comprises an adsorption water outlet device and a desorption water outlet device; Preferably, the adsorption water inlet device comprises an adsorption water inlet check valve, an adsorption water inlet pump station and an adsorption water inlet reservoir; Preferably, the desorption water inlet device comprises a desorption water inlet check valve, a desorption water inlet pump station and a desorption water inlet reservoir; Preferably, the adsorption water outlet device comprises an adsorption water outlet water stop valve, an adsorption water outlet pump station and an adsorption water outlet reservoir; Preferably, the desorption water outlet device comprises a desorption water outlet water stop valve, a desorption water outlet pump station and a desorption water outlet reservoir.

5. The nitrate adsorption reaction device according to any one of claims 1 to 4, characterized in that: The aluminum-modified activated carbon in the aluminum-modified activated carbon layer is obtained by the following preparation method, which comprises the following steps: The activated carbon and the aluminum salt solution are mixed to obtain a mixed solution, the mixed solution is heated to obtain an aluminum-modified activated carbon precursor, and the aluminum-modified activated carbon precursor is calcined under an inert atmosphere to obtain the aluminum-modified activated carbon.

6. The nitrate adsorption reaction device according to claim 5, characterized in that: The particle size of the activated carbon is less than 10 mm, preferably less than 5 mm; Preferably, in the mixed solution, according to the content of metallic aluminum, the mass ratio of the activated carbon to the metallic aluminum is 1:(0.01-0.1), preferably 1:(0.03-0.05); Preferably, the aluminum salt solution includes aluminum chloride and / or aluminum nitrate; Preferably, in the aluminum salt solution, the molar ratio of aluminum chloride to aluminum nitrate is 1:(0.02-0.25).

7. The nitrate adsorption reaction device according to claim 5 or 6, characterized in that: The method of mixing the activated carbon and the aluminum salt solution includes stirring; Preferably, the stirring time is 5h-20h; Preferably, the temperature of the heated mixed liquid is 60°C-100°C, preferably 70°C-90°C; Preferably, the inert atmosphere comprises nitrogen and / or an inert gas; Preferably, the inert atmosphere comprises nitrogen and / or argon; Preferably, the calcination temperature is 300°C-600°C, preferably 400°C-500°C.

8. A method for using the nitrate adsorption reaction device according to any one of claims 1 to 7, characterized in that: The method of use includes: During the adsorption reaction, the nitrate wastewater flows in from the bottom of the columnar reaction device, passes through the aluminum-modified activated carbon layer and the electrode layer, and flows out from the top of the columnar reaction device; When the desorption reaction is carried out, the desorption liquid flows in from the bottom of the columnar reaction device, passes through the aluminum-modified activated carbon layer and the electrode layer, and flows out from the top of the columnar reaction device.

9. The method of use according to claim 8, characterized in that: The method of use also includes adjusting the Cl in the nitrate wastewater before it enters the nitrate adsorption reaction device. - The mass concentration is 20mg / L-100mg / L, preferably 40mg / L-60mg / L; Preferably, after the adjustment, the nitrogen and Cl in the nitrate wastewater are - The mass concentration ratio is 1:2.5-1:3.5; Preferably, the desorption liquid is a chloride salt solution; Preferably, the chloride salt solution includes any one of NaCl, KCl or NH4Cl or a combination of at least two thereof; Preferably, the chloride salt solution contains Cl - The mass concentration is 0.5g / L-10g / L, preferably 4g / L-8g / L.

10. An application of the nitrate adsorption reaction device according to any one of claims 1 to 7, characterized in that: The nitrate adsorption reaction device is used for removing nitrate in wastewater.

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