CN114538575A - Electrochemical reduction device and method for high nitrate nitrogen wastewater - Google Patents
Electrochemical reduction device and method for high nitrate nitrogen wastewater Download PDFInfo
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Abstract
An electrochemical reduction device for high nitrate nitrogen wastewater, comprising: the device comprises an anode chamber, a cathode chamber, an anion-cation exchange tank, a proton exchange membrane, a cathode, a platinum sheet anode, a reference electrode, a power supply system and a stirring system; the cathode chamber and the anode chamber are connected through an anion and cation exchange tank and are separated by a proton exchange membrane fixed in the middle of the anion and cation exchange tank; the cathode is fixed in the cathode chamber, the platinum sheet anode is fixed in the anode chamber, and the cathode and the platinum sheet anode are arranged on two sides of the proton exchange membrane in parallel; a reference electrode is fixed in the cathode chamber; the power supply system is respectively connected with the cathode and the platinum sheet anode; the stirring system comprises a magnetic stirrer and a rotor, wherein the magnetic stirrer is arranged at the bottom of the outer side of the cathode chamber, and the rotor is arranged at the bottom of the inner side of the cathode chamber. The method meets the requirement stability by adjusting the reaction voltage and the operation time to obtain 1:1, the ammonia nitrogen and the nitrite nitrogen are used as reaction substrates in the anaerobic ammonia oxidation process, have high flexibility and high catalytic efficiency, and have important significance for realizing the deep denitrification of the anaerobic ammonia oxidation subsequently.
Description
Technical Field
The invention relates to the technical field of electrochemical reduction of nitrate nitrogen, in particular to a device and a method for electrochemical reduction of high nitrate nitrogen wastewater.
Background
When the nitrogen content of the water body exceeds the environmental threshold (TN is more than 0.2mg/L), a great amount of blue algae explodes, and the water body eutrophication is caused. High nitrate nitrogen drinking water threatens human health and induces various diseases such as blue-infant syndrome, infant hemorrhagic erythropoiesis, adult gastric cancer, methemoglobinemia and the like. Excessive nitrate nitrogen in water body can also induce toxic symptoms such as tachypnea, apoplexy and the like of livestock.
The biological nitrification/denitrification process is most widely used as a traditional denitrification technology, wherein the nitrification reaction is energy-intensive, and the subsequent denitrification usually requires an external organic carbon source to completely reduce nitrate nitrogen. The removal of nitrate nitrogen requires a proper carbon-nitrogen ratio (C/N) of 2.7-3. For wastewater with low C/N ratio, the need for additional organic carbon addition results in a dramatic increase in cost.
The anaerobic ammonia oxidation denitrification technology is a novel energy-saving and consumption-reducing sewage biological treatment technology, and realizes autotrophic denitrification by oxidizing ammonia nitrogen through nitrite nitrogen. The denitrification technology based on anaerobic ammonia oxidation is concerned by the advantages of no need of extra carbon source, low sludge yield, low energy consumption, low cost, high denitrification rate, no greenhouse gas emission and the like.
The electrochemical nitrogen reduction method is a nitrate nitrogen reduction method with high catalytic efficiency, strong flexibility and high selectivity, and selectively reduces nitrate nitrogen into ammonia nitrogen, nitrite nitrogen, nitrogen and the like by utilizing electrons (serving as green reducing agents) provided by a power supply. Therefore, it is an urgent technical problem to be solved by those skilled in the art to provide an electrochemical reduction apparatus and method for high nitrate nitrogen wastewater.
Disclosure of Invention
In view of the above, the present invention provides an electrochemical reduction apparatus and method for high nitrate nitrogen wastewater, which can meet the requirements by adjusting the reaction voltage and the operation time to stably obtain 1:1, the ammonia nitrogen and nitrite nitrogen are used as reaction substrates in the anaerobic ammonia oxidation process, so that the method has high flexibility and high catalytic efficiency, the direct current power supply is used for providing electrons (used as a green reducing agent), the operation is simple and easy, the method has important significance for realizing the deep denitrification of the anaerobic ammonia oxidation subsequently, and the method is more suitable for actual wastewater treatment.
The invention provides a high nitrate nitrogen wastewater electrochemical reduction device, which comprises:
the device comprises an anode chamber, a cathode chamber, an anion-cation exchange tank, a proton exchange membrane, a cathode, a platinum sheet anode, a reference electrode, a power supply system and a stirring system;
the anode chamber and the cathode chamber are connected through an anion-cation exchange tank and are separated through a proton exchange membrane fixed in the middle of the anion-cation exchange tank;
the cathode is fixed on the cathode chamber, the platinum sheet anode is fixed on the anode chamber, and the cathode and the platinum sheet anode are arranged on two sides of the proton exchange membrane in parallel;
the reference electrode is fixed on the cathode chamber;
the power supply system is respectively connected with the cathode and the platinum sheet anode;
the stirring system comprises a magnetic stirrer and a rotor, wherein the magnetic stirrer is arranged at the bottom of the outer side of the cathode chamber, and the rotor is arranged at the bottom of the inner side of the cathode chamber.
Preferably, the reaction volume of the anode chamber is 300-500 mL, the inner diameter is 60-80 mm, and the effective height is 110-150 mm; the reaction volume of the cathode chamber is 300-500 mL, the inner diameter is 60-80 mm, and the effective height is 110-150 mm.
Preferably, the proton exchange membrane is a Nafion 117 membrane;
the proton exchange membrane is arranged at the middle end of the anion and cation exchange tank and is fixed by a fixing clamp, so that the tightness of the device is ensured.
Preferably, the cathode is a brass mesh deposition Cu cathode or a stainless steel mesh deposition Cu cathode;
the brass net is an H65 brass net with 50 meshes to 150 meshes, the wire thickness is 0.1mm to 0.15mm, and the aperture is 0.1mm to 0.2 mm;
the stainless steel net is a 304 stainless steel net with 50-150 meshes, the wire thickness is 0.1-0.15 mm, and the hole diameter is 0.1-0.2 mm.
Preferably, the deposited Cu cathode is between 0.4M and 0.6M CuSO4、pH<3, controlling the cathode potential to be-2V by an electrochemical workstation, and depositing for 20 min-40 min at 300 rpm-500 rpm.
Preferably, the distance between the cathode and the platinum sheet anode is 4.5 cm-5.5 cm.
Preferably, the power supply system is a direct current power supply, and the applicable voltage is 15V-25V.
The invention also provides an electrochemical reduction method for the high nitrate nitrogen wastewater, and the electrochemical reduction device for the high nitrate nitrogen wastewater adopting the technical scheme comprises the following steps:
a) placing the high nitrate nitrogen wastewater in a cathode chamber with a built-in rotor, and adding electrolyte into an anode chamber; washing the surface of the cathode with ethanol, blowing the cathode with inert gas, weighing the cathode, fixing the cathode on a cathode chamber, and introducing the inert gas for deoxidation; placing a platinum sheet anode in the anode chamber, placing a reference electrode in the cathode chamber, and opening the magnetic stirrer;
b) connecting the positive electrode of a power supply system with the anode of a platinum sheet, connecting the negative electrode of the power supply system with the cathode, and starting to operate after the reaction voltage is adjusted; after the operation is carried out until the nitrite nitrogen and the ammonia nitrogen have specific reduction proportion, the reaction is terminated, and the electrochemical reduction of the high nitrate nitrogen wastewater is completed; the specific reduction ratio is as follows: NO3 --N/NH4 +-N≈1。
Preferably, the water quality of the high nitrate nitrogen wastewater in the step a) is as follows: NO3 --N is 100mg/L to 500mg/L, conductivity is 20mS/cm to 100 mS/cm;
the conductivity of the electrolyte is 30 mS/cm-80 mS/cm;
the rotating speed of the opened magnetic stirrer is 200-600 rpm.
Preferably, the reaction voltage in the step b) is 15V-25V; the running time is 3.5-7 h.
The invention provides a device and a method for electrochemically reducing high nitrate nitrogen wastewater; the device includes: the device comprises an anode chamber, a cathode chamber, an anion-cation exchange tank, a proton exchange membrane, a cathode, a platinum sheet anode, a reference electrode, a power supply system and a stirring system; the anode chamber and the cathode chamber are connected through an anion-cation exchange tank and are separated through a proton exchange membrane fixed in the middle of the anion-cation exchange tank; the cathode is fixed on the cathode chamber, the platinum sheet anode is fixed on the anode chamber, and the cathode and the platinum sheet anode are arranged on two sides of the proton exchange membrane in parallel; the reference electrode is fixed on the cathode chamber; the power supply system is respectively connected with the cathode and the platinum sheet anode; the stirring system comprises a magnetic stirrer and a rotor, wherein the magnetic stirrer is arranged at the bottom of the outer side of the cathode chamber, and the rotor is arranged at the bottom of the inner side of the cathode chamber. The electrochemical reduction device and the electrochemical reduction method for the high nitrate nitrogen wastewater provided by the invention meet the requirements by adjusting the reaction voltage and the operation time to stably obtain the following components: 1, the ammonia nitrogen and nitrite nitrogen are used as reaction substrates in the anaerobic ammonia oxidation process, so that the method has high flexibility and high catalytic efficiency, the direct current power supply is used for providing electrons (used as a green reducing agent), the operation is simple and easy, the method has important significance for realizing the deep denitrification of the anaerobic ammonia oxidation subsequently, and the method is more suitable for actual wastewater treatment.
Drawings
Fig. 1 is a schematic structural diagram of a high nitrate nitrogen wastewater electrochemical reduction device provided in embodiment 1 of the present invention.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a high nitrate nitrogen wastewater electrochemical reduction device, which comprises:
the device comprises an anode chamber, a cathode chamber, an anion-cation exchange tank, a proton exchange membrane, a cathode, a platinum sheet anode, a reference electrode, a power supply system and a stirring system;
the anode chamber and the cathode chamber are connected through an anion-cation exchange tank and are separated through a proton exchange membrane fixed in the middle of the anion-cation exchange tank;
the cathode is fixed on the cathode chamber, the platinum sheet anode is fixed on the anode chamber, and the cathode and the platinum sheet anode are arranged on two sides of the proton exchange membrane in parallel;
the reference electrode is fixed on the cathode chamber;
the power supply system is respectively connected with the cathode and the platinum sheet anode;
the stirring system comprises a magnetic stirrer and a rotor, wherein the magnetic stirrer is arranged at the bottom of the outer side of the cathode chamber, and the rotor is arranged at the bottom of the inner side of the cathode chamber.
In the invention, the electrochemical reduction device for high nitrate nitrogen wastewater comprises: anode chamber, cathode chamber, anion and cation exchange tank, proton exchange membrane, cathode, platinum sheet anode, reference electrode, power supply system and stirring system.
In the invention, the anode chamber and the cathode chamber are connected through an anion-cation exchange tank to form an H-shaped electrolytic cell which is the main body configuration of the electrochemical reduction device for the high nitrate nitrogen wastewater; the cathode chamber is internally provided with a columnar cavity, one side below the cavity is connected with the anion-cation exchange tank, the top end of the cavity is provided with a sealing cover, and the sealing cover is provided with two gas ports and two electrode ports; the inside of the anode chamber is a columnar cavity, one side below the cavity is connected with a cation-anion exchange tank, the top end of the cavity is provided with a sealing cover, and the sealing cover is provided with two gas ports and an electrode port; the interior of the anion and cation exchange tank is a columnar cavity, the middle of the anion and cation exchange tank is separated by a proton exchange membrane, and the tightness of the device is ensured by a fixing clamp. In the present invention, the reaction volume of the anode chamber is preferably 300mL to 500mL, more preferably 400mL, the inner diameter is preferably 60mm to 80mm, more preferably 70mm, and the effective height is preferably 110mm to 150mm, more preferably 130 mm; the cathode chamber preferably has a reaction volume of 300mL to 500mL, more preferably 400mL, an inner diameter of 60mm to 80mm, more preferably 70mm, and an effective height of 110mm to 150mm, more preferably 130 mm.
In the invention, the anode chamber and the cathode chamber are connected through an anion and cation exchange tank and are separated by a proton exchange membrane fixed in the middle of the anion and cation exchange tank. In the present invention, the proton exchange membrane is preferably a Nafion 117 membrane; commercially available products well known to those skilled in the art may be used. In the invention, the proton exchange membrane is preferably arranged at the middle end of the anion and cation exchange tank and is fixed by a fixing clamp, so that the tightness of the device is ensured.
In the present invention, the cathode is fixed in the cathode compartment, preferably by means of an electrode clamp; the platinum sheet anode is fixed on the anode chamber, preferably by an electrode clamp; the electrode clamp is preferably a platinum electrode; the cathode and the platinum sheet anode are arranged on two sides of the proton exchange membrane in parallel; from this, it is known that the cathode and the platinum sheet anode approach the proton exchange membrane from both sides thereof, respectively. In the invention, the distance between the cathode and the platinum sheet anode is preferably 4.5 cm-5.5 cm.
In the present invention, the cathode is preferably a brass mesh deposited Cu cathode or a stainless steel mesh deposited Cu cathode, more preferably a brass mesh deposited Cu cathode. In the invention, the brass net is preferably an H65 brass net with 50 meshes to 150 meshes, more preferably an H65 brass net with 100 meshes, the wire thickness is preferably 0.1mm to 0.15mm, and the pore diameter is preferably 0.1mm to 0.2mm, more preferably 0.15 mm; the stainless steel net is preferably a 304 stainless steel net with 50 meshes to 150 meshes, more preferably a 304 stainless steel net with 100 meshes, the thickness of the wire is preferably 0.1mm to 0.15mm, and the aperture is preferably 0.1mm to 0.2mm, more preferably 0.15 mm.
In the present invention, the deposited Cu cathode is preferably between 0.4M and 0.6M CuSO4、pH<3 is prepared by controlling the cathode potential to be-2V and 300-500 rpm by an electrochemical workstation and depositing for 20-40 min, more preferably 0.5M CuSO4、pH<2, controlling the cathode potential to be-2V by an electrochemical workstation, and depositing for 30min at 400 rpm. In the preferred embodiment of the invention, the pretreated brass mesh or stainless steel mesh is firstly fixed by a platinum electrode clamp, and is put into a 500mL single-chamber electrochemical cell together with a platinum sheet electrode and a reference electrode for electrodeposition to obtain a deposited Cu cathode.
In the present invention, the reference electrode is fixed to the cathode chamber, and the present invention is not particularly limited thereto.
In the present invention, the power supply system is connected to the cathode and the platinum sheet anode, respectively, preferably, via electrode clamps.
In the present invention, the power supply system is preferably a direct current power supply, such as a model VC3003(30V/5A single-circuit) direct current electric box known to those skilled in the art, and the applicable voltage is preferably 15V-25V.
In the invention, the stirring system comprises a magnetic stirrer and a rotor, wherein the magnetic stirrer is arranged at the bottom of the outer side of the cathode chamber, and the rotor is arranged at the bottom of the inner side of the cathode chamber.
The electrochemical reduction device for high nitrate nitrogen wastewater provided by the invention is suitable for high nitrate nitrogen wastewater treatment, and has the characteristics of stable accumulation of ammonia nitrogen and nitrite nitrogen, additional carbon source saving and easy flexible regulation.
The invention also provides an electrochemical reduction method for the high nitrate nitrogen wastewater, and the electrochemical reduction device for the high nitrate nitrogen wastewater adopting the technical scheme comprises the following steps:
a) placing the high nitrate nitrogen wastewater in a cathode chamber with a built-in rotor, and adding electrolyte into an anode chamber; washing the surface of the cathode with ethanol, blowing the cathode with inert gas, weighing the cathode, fixing the cathode on a cathode chamber, and introducing the inert gas for deoxidation; placing a platinum sheet anode in the anode chamber, placing a reference electrode in the cathode chamber, and opening the magnetic stirrer;
b) connecting the positive electrode of a power supply system with the anode of a platinum sheet, connecting the negative electrode of the power supply system with the cathode, and starting to operate after the reaction voltage is adjusted; after the operation is carried out until the nitrite nitrogen and the ammonia nitrogen have specific reduction proportion, the reaction is terminated, and the electrochemical reduction of the high nitrate nitrogen wastewater is completed; the specific reduction ratio is as follows: NO3 --N/NH4 +-N≈1。
According to the electrochemical reduction device for the high nitrate nitrogen wastewater, provided by the invention, firstly, the high nitrate nitrogen wastewater is placed in a cathode chamber with a built-in rotor, and electrolyte is added into the anode chamber; washing the surface of the cathode with ethanol, blowing the cathode with inert gas, weighing the cathode, fixing the cathode in a cathode chamber, and introducing the inert gas for deoxidation; the anode chamber is provided with a platinum sheet anode, the cathode chamber is provided with a reference electrode, and the magnetic stirrer is started.
In the present invention, the high nitrateThe water quality of the nitrogen wastewater is preferably: NO3 --N is 100mg/L to 500mg/L, more preferably: NO (nitric oxide)3 --N-300 mg/L; the conductivity of the high nitrate nitrogen wastewater is preferably 20-100 mS/cm, and more preferably 50-70 mS/cm.
In the present invention, the conductivity of the electrolyte is preferably 30mS/cm to 80mS/cm, more preferably 50mS/cm to 60mS/cm, and an aqueous potassium sulfate solution well known to those skilled in the art may be used.
In the invention, the process that the high nitrate nitrogen wastewater is placed in the cathode chamber with the built-in rotor and the electrolyte is added into the anode chamber is preferably realized by a pump outside the device; in addition, after the reaction is terminated, the effluent from the cathode chamber is also pumped out by the pump, and the present invention is not limited thereto.
In the present invention, the rotation speed of the turning-on magnetic stirrer is preferably 200rpm to 600rpm, more preferably 400 rpm.
Then, the anode of a power supply system is connected with the anode of a platinum sheet, the cathode of the power supply system is connected with the cathode, and the power supply system starts to operate after the reaction voltage is adjusted; and after the operation is carried out until the nitrite nitrogen and the ammonia nitrogen have a specific reduction ratio, the reaction is terminated, and the electrochemical reduction of the high nitrate nitrogen wastewater is completed.
In the present invention, the reaction voltage is preferably 15V to 25V; the running time is preferably 3.5 h-7 h.
In the present invention, the specific reduction ratio is: NO3 --N/NH4 +-N≈1。
The electrochemical specific reduction method for the high nitrate nitrogen wastewater provided by the invention has the advantages of high reaction rate, high treatment efficiency and large reaction scale, and is more suitable for wastewater treatment; the areas of the cathode electrode plate and the anode electrode plate are increased, and the activation point positions are increased; the cathode is simply modified, so that the specific surface area is enlarged, the electron transfer rate is accelerated, the electrode surface reduction reaction is promoted, the cathode deposition substance can effectively control the required product, and nitrite nitrogen and ammonia nitrogen in the required proportion can be obtained by simply adjusting the voltage and the reaction time; the direct current power supply control is more convenient to be applied to wastewater treatment and is simple and easy to regulate.
Around the treatment difficulty that the high nitrate nitrogen wastewater is difficult to stably reach the standard at the present stage and the bottleneck problem that ammonia nitrogen and nitrite nitrogen are difficult to stably obtain in a ratio of 1:1 by anaerobic ammonia oxidation, the invention provides a high nitrate nitrogen wastewater electrochemical reduction device and method; the device includes: the device comprises an anode chamber, a cathode chamber, an anion-cation exchange tank, a proton exchange membrane, a cathode, a platinum sheet anode, a reference electrode, a power supply system and a stirring system; the anode chamber and the cathode chamber are connected through an anion-cation exchange tank and are separated through a proton exchange membrane fixed in the middle of the anion-cation exchange tank; the cathode is fixed on the cathode chamber, the platinum sheet anode is fixed on the anode chamber, and the cathode and the platinum sheet anode are arranged on two sides of the proton exchange membrane in parallel; the reference electrode is fixed on the cathode chamber; the power supply system is respectively connected with the cathode and the platinum sheet anode; the stirring system comprises a magnetic stirrer and a rotor, wherein the magnetic stirrer is arranged at the bottom of the outer side of the cathode chamber, and the rotor is arranged at the bottom of the inner side of the cathode chamber. The electrochemical reduction device and the electrochemical reduction method for the high nitrate nitrogen wastewater provided by the invention meet the requirements by adjusting the reaction voltage and the operation time to stably obtain the following components: 1, the ammonia nitrogen and nitrite nitrogen are used as reaction substrates in the anaerobic ammonia oxidation process, so that the method has high flexibility and high catalytic efficiency, the direct current power supply is used for providing electrons (used as a green reducing agent), the operation is simple and easy, the method has important significance for realizing the deep denitrification of the anaerobic ammonia oxidation subsequently, and the method is more suitable for actual wastewater treatment.
To further illustrate the present invention, the following examples are provided for illustration.
Example 1
The structural schematic diagram of the electrochemical reduction device for high nitrate nitrogen wastewater provided in embodiment 1 of the present invention is shown in fig. 1, wherein 1 is an anode chamber, 2 is a cathode chamber, 3 is an anion-cation exchange tank, 4 is a proton exchange membrane, 5 is a brass mesh (or stainless steel mesh) deposited Cu cathode, 6 is a platinum sheet anode, 7 is a reference electrode, 8 is a direct current power supply, and 9 is a stirring system.
The working process of the electrochemical reduction device for the high nitrate nitrogen wastewater is as follows:
a double-chamber H-shaped electrolytic cell with the effective volumes of an anode chamber 1 and a cathode chamber 2 of 400mL respectively is adopted, and the middle of a cation-anion exchange tank 3 is separated by a proton exchange membrane 4 and fixed by a fixing clamp; cu deposited by a brass net (or a stainless steel net) of 4cm multiplied by 6cm is taken as a cathode 5, a platinum sheet of 2.5cm multiplied by 2.5cm is taken as an anode 6, and a saturated calomel electrode (model-232) is taken as a reference electrode 7; the platinum electrode clamp for fixing the cathode plate is used for connecting an external circuit; a direct current power supply 8 with external voltage of 15V-25V; the cathode chamber is provided with a rotor inside and is placed on a magnetic stirrer 9.
High nitrate nitrogen wastewater (2.166 g/L potassium nitrate, 43.565g/L potassium sulfate) is simulated by a potassium nitrate solution and is used as inflow water.
Using a 100 mesh H65 brass mesh (4 cm. times.6 cm) as the substrate, at 0.5M CuSO4、pH<2 in 500mL of the electrodeposition solution, applying a voltage of-2V by an electrochemical workstation, and depositing for 30 minutes at 400 rpm; the material was weighted from an initial 1.1569g to 2.5079 g.
400mL of electrolyte (300mg/L NO) is introduced into the cathode chamber3 --N、0.25M K2SO4) 400mL of electrolyte (0.25M K) was introduced into the anode chamber2SO4) Conductivity of about 55 mS/cm; under the conditions that the external voltage of the direct current power supply is 15V and the rotating speed is 400rpm, the current is 0.157A and the current density is 6.54mA/cm2。
Taking a water sample every half hour, and testing the nitrogen conversion condition; when the reaction is carried out for the 2h, a small amount of ammonia nitrogen begins to appear in the water sample, and the nitrite nitrogen reaches 140 mg/L; with the increase of the reaction time, the nitrite nitrogen still rapidly increases, the ammonia nitrogen concentration slowly increases, and the nitrite nitrogen concentration reaches 190mg/L at the peak in 4.5h, and the ammonia nitrogen increases to 70 mg/L; then the concentration of nitrate nitrogen and nitrite nitrogen is synchronously reduced, and the concentration ratio of ammonia nitrogen to nitrite nitrogen reaches about 1:1, the concentration of the residual nitrate nitrogen is about 130mg/L, and the concentration of the residual nitrate nitrogen is about 40 mg/L.
Example 2
The electrochemical reduction device for high nitrate nitrogen wastewater provided in example 1 is adopted to follow the working process provided in example 1, and the difference is that: increasing the voltage applied by the DC power supply to 25V at 400rpm, the current is 0.282A, and the current density is 11.75mA/cm2(ii) a When the reaction is carried out for 1h, a small amount of ammonia nitrogen begins to appear in the water sample, and at the momentNitrite nitrogen is accumulated to 100 mg/L; then, in 2.5h, the concentration of nitrite nitrogen reaches the peak value of 175mg/L, and the ammonia nitrogen reaches 82 mg/L; along with the synchronous reduction of the concentrations of the nitrate nitrogen and the nitrite nitrogen, the concentrations of the ammonia nitrogen and the nitrite nitrogen reach the same concentration of about 130mg/L and the concentration of the residual nitrate nitrogen is about 40mg/L in 3.5 h.
Example 3
The electrochemical reduction device for high nitrate nitrogen wastewater provided in example 1 is adopted to follow the working process provided in example 1, and the difference is that: replacing the substrate with 100 mesh H65 brass mesh (4cm × 6cm) with 100 mesh 304 stainless steel mesh (4cm × 6cm) substrate in 0.5M CuSO4、pH<2 in 500mL of the electrodeposition solution, applying a voltage of-2V by an electrochemical workstation, and depositing for 30 minutes at 400 rpm; the material was weighted from an initial 1.1231g to 2.4653 g. Under the conditions of the external voltage of the direct current power supply of 25V and the rotation speed of 400rpm, the current is 0.281A and the current density is 11.71mA/cm2(ii) a The ammonia nitrogen slowly accumulates after the reaction is still 1h, and the concentration of the nitrite nitrogen is 105 mg/L; after 2h, the content of nitrite nitrogen begins to decrease, the concentration of nitrite nitrogen is 150mg/L, and the ammonia nitrogen reaches 60 mg/L; and when the ammonia nitrogen concentration exceeds the nitrite nitrogen concentration by 150mg/L, the nitrite nitrogen concentration is 100mg/L, and the residual nitrate nitrogen is about 50mg/L in 3.5 h.
The experimental result shows that the reaction time required in experimental example 3 is between 3 and 3.5 hours, but compared with experimental example 2, the residual concentration of nitrate nitrogen in the reaction system of the cathode material using the stainless steel mesh as the substrate is slightly higher than that of the reaction system of the cathode material using the brass mesh as the substrate; the stainless steel mesh has good selectivity to ammonia nitrogen due to the fact that the material of the stainless steel mesh mainly contains substances such as iron, nickel and the like, and the phenomenon is expressed in that the ammonia nitrogen accumulation rate is high; the stability of the two substrate materials is relatively consistent, and the uniformity and deposition amount of Cu on electrodeposition under the same condition are relatively consistent; the electrical conductivity of the two materials is relatively consistent, and the current density can reach 11mA/cm under the voltage of-25V2The above.
In conclusion, the reaction voltage and the reaction time can be adjusted according to the proportion of the required products, the nitrate nitrogen is promoted to be converted into ammonia nitrogen and nitrite, the concentration ratio is close to 1, and the reaction conditions in the embodiment 2 meet the requirements.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. An electrochemical reduction device for high nitrate nitrogen wastewater, comprising:
the device comprises an anode chamber, a cathode chamber, an anion-cation exchange tank, a proton exchange membrane, a cathode, a platinum sheet anode, a reference electrode, a power supply system and a stirring system;
the anode chamber and the cathode chamber are connected through an anion-cation exchange tank and are separated through a proton exchange membrane fixed in the middle of the anion-cation exchange tank;
the cathode is fixed on the cathode chamber, the platinum sheet anode is fixed on the anode chamber, and the cathode and the platinum sheet anode are arranged on two sides of the proton exchange membrane in parallel;
the reference electrode is fixed on the cathode chamber;
the power supply system is respectively connected with the cathode and the platinum sheet anode;
the stirring system comprises a magnetic stirrer and a rotor, wherein the magnetic stirrer is arranged at the bottom of the outer side of the cathode chamber, and the rotor is arranged at the bottom of the inner side of the cathode chamber.
2. The electrochemical reduction device for high nitrate nitrogen wastewater according to claim 1, wherein the reaction volume of the anode chamber is 300-500 mL, the inner diameter is 60-80 mm, and the effective height is 110-150 mm; the reaction volume of the cathode chamber is 300-500 mL, the inner diameter is 60-80 mm, and the effective height is 110-150 mm.
3. The electrochemical reduction device for high nitrate nitrogen wastewater as claimed in claim 1, wherein the proton exchange membrane is a Nafion 117 membrane;
the proton exchange membrane is arranged at the middle end of the anion and cation exchange tank and is fixed by a fixing clamp, so that the tightness of the device is ensured.
4. The electrochemical reduction device for wastewater with high nitrate nitrogen content according to claim 1, wherein the cathode is a brass mesh deposition Cu cathode or a stainless steel mesh deposition Cu cathode;
the brass net is an H65 brass net with 50 meshes to 150 meshes, the wire thickness is 0.1mm to 0.15mm, and the aperture is 0.1mm to 0.2 mm;
the stainless steel net is a 304 stainless steel net with 50-150 meshes, the wire thickness is 0.1-0.15 mm, and the hole diameter is 0.1-0.2 mm.
5. The electrochemical reduction device for wastewater with high nitrate nitrogen content according to claim 4, wherein the deposited Cu cathode is 0.4-0.6M CuSO4、pH<3, controlling the cathode potential to be-2V by an electrochemical workstation, and depositing for 20 min-40 min at 300 rpm-500 rpm.
6. The electrochemical reduction device for high nitrate nitrogen wastewater according to claim 1, wherein the distance between the cathode and the platinum sheet anode is 4.5 cm-5.5 cm.
7. The electrochemical reduction device for wastewater with high nitrate nitrogen content according to claim 1, wherein the power supply system is a direct current power supply, and the applicable voltage is 15V-25V.
8. The electrochemical reduction method for the high nitrate nitrogen wastewater is characterized by adopting the electrochemical reduction device for the high nitrate nitrogen wastewater as claimed in any one of claims 1 to 7, and comprising the following steps of:
a) placing the high nitrate nitrogen wastewater in a cathode chamber with a built-in rotor, and adding electrolyte into an anode chamber; washing the surface of the cathode with ethanol, blowing the cathode with inert gas, weighing the cathode, fixing the cathode on a cathode chamber, and introducing the inert gas for deoxidation; placing a platinum sheet anode in the anode chamber, placing a reference electrode in the cathode chamber, and opening the magnetic stirrer;
b) connecting the positive electrode of a power supply system with the anode of a platinum sheet, connecting the negative electrode of the power supply system with the cathode, and starting to operate after the reaction voltage is adjusted; after the operation is carried out until the nitrite nitrogen and the ammonia nitrogen have specific reduction proportion, the reaction is terminated, and the electrochemical reduction of the high nitrate nitrogen wastewater is completed; the specific reduction ratio is as follows: NO3 --N/NH4 +-N≈1。
9. The electrochemical reduction method for high nitrate nitrogen wastewater according to claim 8, wherein the water quality of the high nitrate nitrogen wastewater in the step a) is as follows: NO3 --N is 100mg/L to 500mg/L, conductivity is 20mS/cm to 100 mS/cm;
the conductivity of the electrolyte is 30 mS/cm-80 mS/cm;
the rotating speed of the opened magnetic stirrer is 200-600 rpm.
10. The electrochemical reduction method for high nitrate nitrogen wastewater according to claim 8, wherein the reaction voltage in the step b) is 15V to 25V; the running time is 3.5-7 h.
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