Capacitive deionization device for selectively removing nitrate radicals in water

Abstract

The invention discloses a capacitive deionization device for selectively removing nitrate radicals in water, which comprises a device outer frame and an electrode plate fixing frame, the device outer frame is sealed by a cover plate, the device further comprises an active electrode plate, a conductive copper sheet and an electrode connector, the active electrode plate comprises an anode plate and a cathode plate which are alternately arranged, a treatment chamber is formed between every two adjacent active electrode plates, each active electrode plate comprises a current collector and an active material coated outside the current collector, the active material coated on the anode plate is bamboo-based activated carbon, and the active material coated on the cathode plate is coconut shell activated carbon. The preparation method has the beneficial effects that the preparation process of the material is simplified, the cost required by material preparation is reduced, the waste of resources is reduced, and meanwhile, the preparation of the electrode material for efficiently and selectively removing nitrate radicals is realized. The efficient adsorption of nitrate radicals can be realized. The selective adsorption of nitrate radicals can be realized. The selectivity coefficient on chloride ions and sulfate radicals is high, and the removal efficiency on nitrate radicals is greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater deep treatment, and in particular to a capacitive deionization device for selectively removing nitrate from water. Background Art

[0002] Capacitive deionization (CDI) is an emerging water treatment technology. When working, a low voltage (1.2V) is applied to its positive and negative electrodes. The electric field force between the electrode plates causes the charged ions in the water to migrate to the two electrodes and thus be removed. When the electrodes are regenerated, the two plates are short-circuited or reversed. The charged ions adsorbed on the electrodes are released back into the solution under the action of the electric field force, and the electrode plates are regenerated, while a higher concentration of desorption solution is obtained. CDI technology has been widely studied in the fields of seawater desalination and water purification. It is gradually developing in the removal of nitrates from water bodies. Compared with biological methods, physical adsorption methods and other technical methods, CDI has the advantages of high efficiency and low energy consumption; at the same time, it can avoid the addition of additional carbon sources in the biological denitrification process, which is more environmentally friendly; compared with reverse osmosis membrane technology, CDI has greater potential in achieving selective removal of ions.

[0003] CDI technology mainly includes the preparation of bamboo-based activated carbon and capacitive deionization device. For the preparation of bamboo-based activated carbon, the existing bamboo-based activated carbon preparation process is relatively complicated and the preparation cost is high. Moreover, the existing capacitive deionization device has poor selective adsorption capacity for nitrate ions. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a capacitive deionization device for selectively removing nitrate from water, and the present invention is achieved through the following technical solutions.

[0005] A capacitive deionization device for selectively removing nitrate from water comprises a device outer frame and an electrode plate fixing frame, each side of the device outer frame is sealed by a cover plate, and also comprises an active electrode plate, a conductive copper sheet and an electrode connector; a drainage bottom valve is fixedly connected to the bottom cover plate of the device outer frame, the active electrode plate is fixed to the device outer frame by the electrode plate fixing frame, the left and right ends of the active electrode plate abut against the cover plates on the left and right sides of the device outer frame, the active electrode plate comprises an anode plate and a cathode plate arranged alternately, a processing chamber is formed between two adjacent active electrode plates, the anode plate is used to adsorb nitrate ions, the conductive copper sheet is located above the active electrode plate, two conductive copper sheets are provided, the conductive copper sheets on the left and right sides are respectively electrically connected to the anode plate and the cathode plate through the electrode connector, the two conductive copper sheets on the left and right sides are respectively electrically connected to the anode and the cathode of an external power supply, the left and right sides of the active electrode plate are fixedly connected to water distribution strips, and the water distribution strips on the left and right sides are respectively connected to a water inlet and a water outlet.

[0006] Preferably, the active electrode plate is made of a current collector, the current collector is made of graphite paper or graphite plate, and the outside of the current collector is coated with an active material.

[0007] Preferably, the active material coated on the outside of the anode plate is bamboo-based activated carbon, and the active material coated on the outside of the cathode plate is coconut shell activated carbon.

[0008] Preferably, the raw materials for preparing the active material include, by weight: 1 to 4 parts of an adhesive, N,N-dimethylformamide, 1 to 4 parts of acetylene black, and 4 to 40 parts of an active material; the coating steps of the active material are as follows: dissolving the adhesive in N,N-dimethylformamide to prepare an adhesive solution, wherein the solid-liquid ratio of the adhesive to N,N-dimethylformamide is 20 to 40 g / ml, adding acetylene black and the active material to the adhesive solution to prepare a slurry; and coating the slurry on both sides of the current collector.

[0009] Preferably, the method for preparing the bamboo-based activated carbon comprises the following steps:

[0010] S1, cleaning and drying the bamboo pieces;

[0011] S2, immersing the dried bamboo slices in a KOH solution and heating them in a water bath;

[0012] S3, the impregnated bamboo slices are carbonized and activated at 600-900° C. to prepare bamboo-based activated carbon.

[0013] Preferably, in step S2, the ratio of the solute mass of the KOH solution to the mass of the bamboo chips is 0.3-10.

[0014] Preferably, in step S3, N2 and CO2 are introduced alternately during the carbonization and activation process of the bamboo chips.

[0015] Preferably, the coconut shell activated carbon is coconut shell activated carbon with impurities removed, which is formed by boiling in 80-100° C. water for 3-5 hours.

[0016] Preferably, the water distribution strip on the left is located at the lower part, and the water distribution strip on the right is located at the upper part.

[0017] The beneficial effects of the present invention are as follows:

[0018] 1. The material preparation process is simplified, the cost of material preparation is reduced, resource waste is reduced, and the preparation of electrode materials for efficient and selective removal of nitrate is achieved. The bamboo-based activated carbon has a high specific surface area, specific capacitance and micropore ratio.

[0019] 2. It can achieve efficient adsorption of nitrate. Since the anode active material has a high specific surface area and a suitable pore size distribution, it exhibits excellent nitrate adsorption capacity. Multiple anode plates and cathode plates are configured to form multiple processing chambers, which has a high removal rate for nitrate.

[0020] 3. It can realize the selective adsorption of nitrate ions. It has a high selectivity coefficient for chloride ions and sulfate ions, which greatly improves the removal efficiency of nitrate ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the description of the specific implementation methods will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 : A top view of a capacitive deionization device for selectively removing nitrate from water according to the present invention;

[0023] Figure 2 : A three-dimensional schematic diagram of a capacitive deionization device for selectively removing nitrate from water according to the present invention.

[0024] The reference numerals are as follows:

[0025] 1-device frame, 2-active electrode plate, 21-anode plate, 22-cathode plate, 3-electrode plate fixing frame, 4-conductive copper sheet, 5-electrode connector, 6-drainage bottom valve, 7-processing chamber, 8-water distribution strip, 9-water inlet, 10-water outlet. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] like Figure 1-2As shown, a capacitive deionization device for selectively removing nitrate from water comprises a device outer frame 2 and an electrode plate fixing frame 3. The sides of the device outer frame 1 are sealed by a cover plate, and also comprise an active electrode plate 2, a conductive copper sheet 4 and an electrode connector 5. A drainage bottom valve 6 is fixedly connected to the bottom cover plate of the device outer frame 1. The active electrode plate 2 is fixed in the device outer frame 1 through the electrode plate fixing frame 3. The left and right ends of the active electrode plate 2 abut against the cover plates on the left and right sides of the device outer frame 1. The active electrode plate 2 comprises an anode plate 21 and a cathode plate 22 which are alternately arranged. 2, a processing chamber 7 is formed between two adjacent active electrode plates 2, an anode plate 21 is used to adsorb nitrate ions, a conductive copper sheet 4 is located above the active electrode plate 2, two conductive copper sheets 4 are provided, the conductive copper sheets 4 on the left and right sides are respectively electrically connected to the anode plate 21 and the cathode plate 22 through the electrode connector 5, the two conductive copper sheets 4 on the left and right sides are respectively electrically connected to the anode and cathode of the external power supply, water distribution strips 8 are fixedly connected to the left and right sides of the active electrode plate 2, and the water distribution strips 8 on the left and right sides are respectively connected to the water inlet 9 and the water outlet 10.

[0028] Furthermore, the active electrode plate 2 is made of a current collector made of graphite paper or graphite plate, and the exterior of the current collector is coated with an active material.

[0029] Furthermore, the active material coated on the outside of the anode plate 21 is bamboo-based activated carbon, and the active material coated on the outside of the cathode plate 22 is coconut shell activated carbon.

[0030] Bamboo-based activated carbon has a high-efficiency and selective adsorption capacity for nitrate, and coconut shell activated carbon has a strong physical activation ability.

[0031] Furthermore, the raw materials for preparing the active material include, by weight: 1 to 4 parts of an adhesive, N,N-dimethylformamide, 1 to 4 parts of acetylene black, and 4 to 40 parts of an active material; the coating steps of the active material are as follows: dissolving the adhesive in N,N-dimethylformamide to prepare an adhesive solution, wherein the solid-liquid ratio of the adhesive to N,N-dimethylformamide is 20 to 40 g / ml, adding acetylene black and the active material to the adhesive solution to prepare a slurry; and coating the slurry on both sides of the current collector.

[0032] The current collector is made of graphite paper or graphite plate. 1 to 4 g of adhesive polyvinylidene fluoride is dissolved in 24 to 160 ml of N, N-dimethylformamide; then 1 to 4 g of conductive acetylene black and 4 to 40 g of active material are added to make slurry; after 2 hours, the slurry is coated on the front and back sides of the current collector with a coating machine, and the coating thickness is 0.2 to 5 mm.

[0033] Furthermore, the preparation method of bamboo-based activated carbon comprises the following steps:

[0034] S1, cleaning and drying the bamboo pieces;

[0035] After removing the skin of the bamboo slices, place them in a 1 mol / L NaOH solution and cook them in a water bath at 60°C to 80°C for 6 hours. After cooking, wash the bamboo slices with deionized water and dry them.

[0036] S2, immersing the dried bamboo pieces in a KOH solution and heating them in a water bath, wherein the ratio of the solute mass of the KOH solution to the mass of the bamboo pieces is 0.3-10.

[0037] Dissolve 6-200g KOH in 200ml deionized water to prepare a solution, weigh 20g bamboo slices and immerse them in the solution, and heat them in a water bath at 80℃ for 3h. The corresponding alkali-to-solid ratio is 0.3-10.

[0038] S3, the impregnated bamboo chips are carbonized and activated at 600-900° C. to produce bamboo-based activated carbon, and N2 and CO2 are introduced alternately during the carbonization and activation process of the bamboo chips.

[0039] The bamboo pieces treated with KOH were placed in a tubular furnace, the heating rate was maintained between 1℃ / min and 10℃ / min, N2 and CO2 were introduced alternately, and a one-step carbonization activation treatment was performed at a temperature of 600℃ to 900℃. The active material with a richer microporous structure was obtained by a more simplified treatment process, and the treatment time was 1h to 5h. In particular, the ventilation process of N2 and CO2 has three modes: "N2-CO2", "CO2-N2" and "N2-CO2-N2", and the ventilation time of each section is equal.

[0040] The carbonized and activated bamboo-based activated carbon was thoroughly washed with 0.1 mol / L to 1 mol / L hydrochloric acid solution and deionized water and dried, then crushed with a grinder and sieved with a 75 μm pore size sieve to obtain an active material that can selectively remove nitrate from water.

[0041] Furthermore, the coconut shell activated carbon is coconut shell activated carbon with impurities removed after being boiled in 80-100° C. water for 3-5 hours.

[0042] The coconut shell activated carbon was boiled at 90°C for 4 h, washed with deionized water to remove impurities, crushed with a grinder and passed through a 200-mesh sieve.

[0043] The coconut shell activated carbon prepared by this method has smaller pore size and denser pores.

[0044] Furthermore, the left water distribution strip 8 is located at the lower part, and the right water distribution strip 8 is located at the upper part.

[0045] A specific embodiment of the present invention is:

[0046] In the present application, the size of the active electrode plates 2 can be set as required, and the number and spacing of the active electrode plates 2 can be adjusted by replacing electrode plate fixing frames 3 of different specifications.

[0047] The prepared bamboo-based activated carbon and coconut shell activated carbon are coated on the anode plate 21 and the cathode plate 22 respectively. Each anode plate 21 is electrically connected to the conductive copper sheet 4 on the left side through the electrode connector 5, and each cathode plate 22 is electrically connected to the conductive copper sheet 4 on the right side through the electrode connector 5.

[0048] During adsorption treatment, an external power supply is turned on so that a voltage of 1.2V is connected between the two conductive copper sheets 4. The wastewater to be treated is pumped in from the water inlet 9, and each treatment chamber 7 is filled with the water distribution strip 8 on the left side. The nitrate ions in the wastewater are selectively adsorbed on the anode plate 21 and removed. The purified water is discharged from the water outlet 10, and the water distribution strip 8 is also set at the water outlet 10. The water inlet 9 is set at the lower left part, and the water outlet 10 is set at the upper right part. During the treatment process, the wastewater "enters from the bottom and exits from the top".

[0049] When the electrode is regenerated, the solution in the device is first drained through the drain bottom valve 6, the two conductive copper sheets 4 are connected, the anode plate 21 and the cathode plate 22 are "short-circuited", the desorption liquid is pumped in from the water inlet 9, the nitrate ions adsorbed on the anode plate 21 are released into the desorption liquid, the desorption liquid is pumped out from the water outlet 10, and the active electrode plate 2 is regenerated. The desorption liquid in the device should be drained through the drain bottom valve 6 before the next adsorption.

[0050] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A capacitive deionization device for selectively removing nitrate from water, comprising a device outer frame (1) and an electrode plate fixing frame (3), wherein each side of the device outer frame (1) is sealed by a cover plate, characterized in that: The device also comprises an active electrode plate (2), a conductive copper sheet (4) and an electrode connector (5); a drainage bottom valve (6) is fixedly connected to the bottom cover plate of the device outer frame (1); the active electrode plate (2) is fixed in the device outer frame (1) through an electrode plate fixing frame (3); the left and right ends of the active electrode plate (2) are in contact with the cover plates on the left and right sides of the device outer frame (1); the active electrode plate (2) comprises an anode plate (21) and a cathode plate (22) which are alternately arranged; a processing chamber (7) is formed between two adjacent active electrode plates (2); the anode plate (2 1) for adsorbing nitrate ions, the conductive copper sheet (4) is located above the active electrode plate (2), two conductive copper sheets (4) are provided, the conductive copper sheets (4) on the left and right sides are respectively electrically connected to the anode plate (21) and the cathode plate (22) through the electrode connector (5), the two conductive copper sheets (4) on the left and right sides are respectively electrically connected to the anode and cathode of an external power supply, and water distribution strips (8) are fixedly connected to the left and right sides of the active electrode plate (2), and the water distribution strips (8) on the left and right sides are respectively connected to a water inlet (9) and a water outlet (10).

2. A capacitive deionization device for selectively removing nitrate from water according to claim 1, characterized in that: The active electrode plate (2) is made of a current collector, which is made of graphite paper or graphite plate, and the outside of the current collector is coated with active material.

3. A capacitive deionization device for selectively removing nitrate from water according to claim 2, characterized in that: The active material coated on the outside of the anode plate (21) is bamboo-based activated carbon, and the active material coated on the outside of the cathode plate (22) is coconut shell activated carbon.

4. A capacitive deionization device for selectively removing nitrate from water according to claim 3, characterized in that: The raw materials for preparing the active material include, by weight, 1 to 4 parts of an adhesive, N,N-dimethylformamide, 1 to 4 parts of acetylene black, and 4 to 40 parts of an active material; the coating steps of the active material are as follows: dissolving the adhesive in N,N-dimethylformamide to prepare an adhesive solution, wherein the solid-liquid ratio of the adhesive to N,N-dimethylformamide is 20 to 40 g / ml, adding acetylene black and the active material to the adhesive solution to prepare a slurry; and coating the slurry on both sides of the current collector.

5. A capacitive deionization device for selectively removing nitrate from water according to claim 3, characterized in that: The preparation method of the bamboo-based activated carbon comprises the following steps: S1, cleaning and drying the bamboo pieces; S2, immersing the dried bamboo slices in a KOH solution and heating them in a water bath; S3, the impregnated bamboo slices are carbonized and activated at 600-900° C. to prepare bamboo-based activated carbon.

6. A capacitive deionization device for selectively removing nitrate from water according to claim 5, characterized in that: In the step S2, the ratio of the solute mass of the KOH solution to the mass of the bamboo chips is 0.3-10.

7. A capacitive deionization device for selectively removing nitrate from water according to claim 5, characterized in that: In step S3, N2 and CO2 are alternately introduced during the carbonization and activation process of the bamboo chips.

8. A capacitive deionization device for selectively removing nitrate from water according to claim 3, characterized in that: The coconut shell activated carbon is coconut shell activated carbon with impurities removed after being boiled in water at 80 to 100° C. for 3 to 5 hours.

9. A capacitive deionization device for selectively removing nitrate from water according to claim 1, characterized in that: The water distribution strip (8) on the left side is located at the lower part, and the water distribution strip (8) on the right side is located at the upper part.

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