A treatment method for removing total nickel and COD from nickel-containing wastewater

Abstract

The present invention belongs to the field of water treatment technology, and specifically relates to a method for removing total nickel and COD from nickel-containing wastewater, comprising the following steps: (1) the nickel-containing wastewater enters a modified tea residue biochar adsorption tower, and modified tea residue biochar is placed in the modified tea residue biochar adsorption tower, wherein the surface area of ​​the modified tea residue biochar is 124.7 to 165.8 m 2 / g; (2) After passing through the modified tea residue biochar adsorption tower, the nickel-containing wastewater enters the resin adsorption tower, which is equipped with a malonic acid-modified polystyrene resin, with the malonic acid-modified polystyrene resin accounting for 75-90% of the entire adsorption tower by volume; (3) After passing through the resin adsorption tower, the nickel-containing wastewater meets the discharge standards. The present invention proposes a complete technical solution for the deep treatment of nickel-containing wastewater for the first time, and uses biochar and other processes to solve the problem of heavy metal and organic matter pollution in nickel-containing wastewater. Therefore, the present invention belongs to a green and low-carbon steel production process system.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment, and in particular relates to a treatment process for removing total nickel and COD from nickel-containing wastewater. Background Art

[0002] During the cold-rolled nickel plating process, nickel ingots are dissolved in sulfuric acid for electroplating. After electroplating, multiple cleaning steps are performed. The resulting cleaning wastewater contains nickel ions and organic matter, known as nickel-containing wastewater. At the wastewater treatment plant, this nickel-containing wastewater undergoes two stages of sedimentation treatment, making it unsuitable for discharge.

[0003] The newly promulgated "Pollutant Emission Standards for the Iron and Steel Industry" (GB13456-2012) stipulates that the chromium content in cold rolling wastewater should be less than 1.0 mg / L; the Environmental Protection Bureau's testing requires that the COD of nickel-containing wastewater should be less than 30 mg / L.

[0004] Currently, the main treatment process for nickel-containing wastewater is lime or sodium hydroxide precipitation technology, but the effluent quality is difficult to meet the requirements of the new national standard.

[0005] Application number CN202110952044.4 discloses a wastewater treatment technology device for nickel-containing wastewater, including a purification cylinder and a cylinder cover. The upper end surface of the purification cylinder is annularly and evenly spaced with four groups of limit blocks. The ground of the cylinder cover is annularly and evenly spaced and fixedly connected with four groups of limit rods. The block heavy metal adsorbent above the bottom of the I-plate slowly dissolves slowly on its outer surface due to water, and moves up and down as the I-plate moves up and down, so that the heavy metal particles dissolved on the outer surface of the block heavy metal adsorbent are rapidly diffused outward by the agitation of water, thereby adsorbing heavy metal ions such as nickel ions in the water, and finally fall on the upper surface of the first soft film through the filter holes of the I-plate. The water flows out from the gap between the first soft film and the purification bin, and leaves the device through the water outlet. The heavy metal adsorbent particles adsorbed with heavy metal ions such as nickel ions slowly accumulate on the first soft film, thereby completing the collection of heavy metal ions such as nickel ions.

[0006] Application number CN201811132444.5 discloses a method for removing total nickel and dissolved organic matter (DOM) from cold-rolling nickel-containing wastewater. The method comprises the following steps: the cold-rolling nickel-containing wastewater enters a modified converter slag adsorption tower, where it remains for 16 to 32 minutes; the modified converter slag adsorbent occupies 75 to 88% of the internal volume of the modified converter slag adsorption tower; the wastewater then enters a pH adjustment tank, where dilute hydrochloric acid is added for a residence time of 12 to 18 minutes, resulting in an effluent pH of 6.6 to 8.2. After the adjustment tank, the wastewater enters a modified resin adsorption tower containing an ethanolamine-modified chelating resin. After passing through the modified resin adsorption tower, the wastewater meets discharge standards. The effluent quality after treatment by the present method is: total nickel of 0.06 to 0.09 mg / L, DOM of 9 to 13 mg / L, and a pH of 6.8 to 8.1.

[0007] However, to date, there is no treatment method or process for simultaneously removing total nickel and COD from nickel-containing wastewater, and the water quality indicators after treatment meet the "Pollutant Emission Standards for the Iron and Steel Industry" (GB13456-2012). Summary of the Invention

[0008] In view of the above, the purpose of the present invention is to develop an economical and efficient pollutant treatment process based on the water quality and quantity of nickel-containing wastewater, with recycling, energy conservation and emission reduction as the main tasks, to reduce environmental pollution and actively respond to increasingly stringent environmental protection regulations.

[0009] The present invention proposes for the first time a complete technical solution for removing total nickel and COD from nickel-containing wastewater, and belongs to a green and environmentally friendly steel production process system.

[0010] To achieve the purpose of the present invention, the technical solution adopted in the present invention is as follows:

[0011] A method for removing total nickel and COD from nickel-containing wastewater, wherein the nickel-containing wastewater is effluent from a lime precipitation process and has water quality characteristics of: total nickel of 3.4 to 7.1 mg / L and COD of 45 to 53 mg / L, comprising the following steps:

[0012] (1) The nickel-containing wastewater enters the modified tea residue biochar adsorption tower, and the modified tea residue biochar is placed in the modified tea residue biochar adsorption tower, and the modified tea residue biochar occupies 80-95% of the volume of the entire modified tea residue biochar adsorption tower; the surface area of ​​the modified tea residue biochar is 124.7-165.8m 2 / g;

[0013] (2) After passing through the modified tea residue biochar adsorption tower, the nickel-containing wastewater enters the resin adsorption tower, which is equipped with a malonic acid-modified polystyrene resin. The malonic acid-modified polystyrene resin accounts for 75-90% of the entire adsorption tower by volume. The saturated adsorption capacity of the malonic acid-modified polystyrene resin for total nickel ions is 1.2-1.7 mg / g.

[0014] (3) Nickel-containing wastewater passes through a resin adsorption tower and is discharged in compliance with discharge standards.

[0015] Furthermore, the residence time of the nickel-containing wastewater in the modified tea residue biochar adsorption tower in step (1) is 27 to 45 minutes.

[0016] Furthermore, the modified tea residue biochar described in step (1) is specially synthesized and prepared according to the water quality characteristics of nickel-containing wastewater, comprising the following steps: 1) raw material selection: using tea residue waste as biochar raw material, preparing a sodium chloride solution with a mass ratio of 1 to 3%, soaking the tea residue waste in the sodium chloride solution, drying, baking, and cooling; 2) carbonization: placing the tea residue waste in a muffle furnace, heating it to 655 to 695°C at a rate of 5 to 7°C / min, pyrolyzing it for 90 to 105 minutes, cooling it, forming tea residue biochar, and placing the tea residue biochar in a muffle furnace. Grind into fine powder with a grinder; 3) secondary modification: screen chitosan with 100-200 mesh, mix tea residue biochar and chitosan in a mass ratio of (5-8):1 to form a mixture, and prepare an aluminum sulfate solution with a mass ratio of 4-7%; immerse the mixture in the aluminum sulfate solution in a liquid-to-solid ratio (volume ratio) of (4-5):1, immerse, dry, place in a muffle furnace, heat at 7-9°C / min to 465-495°C, maintain the temperature for 65-85 minutes, cool, and perform two modifications to form modified tea residue biochar.

[0017] Furthermore, in the above step 1), the tea residue waste is soaked in a sodium chloride solution for 100 to 115 minutes, taken out and dried, placed in a 105° C. oven for 2 to 4 hours, and cooled naturally.

[0018] Furthermore, in the above step 2), the tea residue biochar is ground and then screened to obtain tea residue biochar with a mesh size of 100 to 200.

[0019] Furthermore, in the above step 3), the immersion time is 9 to 12 hours.

[0020] According to the method for removing total nickel and COD from nickel-containing wastewater of the present invention, further, the modified tea residue biochar adsorption tower in step (1) is backwashed after stable operation for 678 to 782 hours, and the backwash time is 10 to 15 minutes.

[0021] According to the method for removing total nickel and COD from nickel-containing wastewater of the present invention, further, after treatment in step (1), the total nickel content of the nickel-containing wastewater is 2.5-6.2 mg / L, and the COD content is 19-27 mg / L.

[0022] According to the method for removing total nickel and COD from nickel-containing wastewater of the present invention, further, in step (2), the residence time of the nickel-containing wastewater in the resin adsorption tower is 25 to 37 minutes.

[0023] According to the method for removing total nickel and COD from nickel-containing wastewater of the present invention, further, in step (2), the malonic acid-modified polystyrene resin is specially prepared according to the water quality characteristics of the nickel-containing wastewater, comprising the following steps: 1) adding tetrahydrofuran to a reactor, adding 789-945 g of diethyl malonate per liter of tetrahydrofuran solution, stirring for 15-22 minutes, and then adding 2.1-3.4 g of sodium hydride and 450-630 g of chloromethylated polystyrene after complete dissolution, heating the reactor to 68-72° C., and reflux for 18-20 hours; 2) after the reaction is completed, cooling, filtering the resin, washing with petroleum ether 2-4 times, acetone 2-4 times, and clean water 2-4 times, respectively, and drying at 65° C. for 2-3 hours to obtain malonic acid-modified polystyrene. Detailed description of the invention:

[0025] A technical solution for removing total nickel and COD from nickel-containing wastewater includes a water inlet pump, a biochar adsorption tower, modified tea residue biochar, a lifting pump, a resin adsorption tower, malonic acid-modified polystyrene resin, and a drainage pump.

[0026] The nickel-containing wastewater is effluent from a lime precipitation process, and the water quality characteristics of the nickel-containing wastewater are: total nickel is 3.4-7.1 mg / L, and COD is 45-53 mg / L.

[0027] The nickel-containing wastewater enters the modified tea residue biochar adsorption tower via an inlet pump. Modified tea residue biochar is placed in the tower. The modified tea residue biochar accounts for 80-95% of the tower's volume. The nickel-containing wastewater resides in the tower for 27-45 minutes. After 678-782 hours of stable operation, the tower is backwashed for 10-15 minutes. After treatment, the total nickel content is 2.5-6.2 mg / L, and the COD content is 19-27 mg / L.

[0028] The modified tea residue biochar is specially synthesized and prepared according to the water quality characteristics of nickel-containing wastewater: 1) Raw material selection: Using tea residue waste as biochar raw material, prepare a sodium chloride solution with a mass ratio of 1-3%, soak the tea residue waste in the sodium chloride solution for 100-115 minutes, take it out and dry it, place it in a 105°C oven for 2-4 hours, and cool it naturally; 2) Carbonization: Place the tea residue waste in a muffle furnace, heat it to 655-695°C at 5-7°C / min, pyrolyze it for 90-105 minutes, cool it naturally to form tea residue biochar, put the tea residue biochar into a grinder and grind it into fine powder, and screen the tea residue biochar with a mesh size of 100-200. 3) Secondary modification: Screen chitosan with a mesh size of 100-200, mix the tea residue biochar and chitosan in a mass ratio of (5-8):1 to form a mixture, and prepare an aluminum sulfate solution with a mass ratio of 4-7%. The mixture was immersed in aluminum sulfate solution at a liquid-solid ratio (volume ratio) of (4-5):1 for 9-12 hours, filtered and dried, placed in a muffle furnace, heated to 465-495°C at 7-9°C / min, kept at a constant temperature for 65-85 minutes, and cooled naturally. The modified tea residue biochar was formed after two modifications. The surface area of ​​the modified tea residue biochar catalyst was 124.7-165.8m 2 / g, the prepared modified tea residue biochar has good adsorption performance and greatly improves the ability to adsorb total nickel and COD.

[0029] After passing through the modified tea residue biochar adsorption tower, the nickel-containing wastewater enters the resin adsorption tower via a lift pump. The malonic acid-modified polystyrene resin accounts for 75-90% of the adsorption tower (by volume). The nickel-containing wastewater resides in the resin adsorption tower for 25-37 minutes.

[0030] The malonic acid-modified polystyrene resin is specially prepared according to the water quality characteristics of nickel-containing wastewater. 1) Tetrahydrofuran is added to a reactor, and 789-945g of diethyl malonate is added to each liter of tetrahydrofuran solution. The mixture is stirred for 15-22 minutes. After complete dissolution, 2.1-3.4g of sodium hydride and 450-630g of chloromethylated polystyrene are added. The reactor is heated to 68-72°C and refluxed for 18-20 hours. 2) After the reaction is completed, the mixture is cooled, filtered, and the resin is washed with petroleum ether 2-4 times, acetone 2-4 times, and clean water 2-4 times, and dried at 65°C for 2-3 hours to obtain malonic acid-modified polystyrene. The saturated adsorption capacity of the malonic acid-modified polystyrene resin for total nickel ions is 1.2-1.7mg / g.

[0031] The nickel-containing wastewater passes through the resin adsorption tower and is discharged through the drainage pump to meet the standards.

[0032] Beneficial technical effects of the present invention:

[0033] This invention, for the first time, proposes a comprehensive technical solution for the advanced treatment of nickel-containing wastewater. Using biochar and other processes, it addresses the environmental pollution issues associated with heavy metals and organic matter in nickel-containing wastewater. Therefore, the invention represents a green, low-carbon steel production process system. After treatment using this process, the effluent contains 0.1-0.2 mg / L of total nickel and 14-24 mg / L of COD. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 : Diagram of a treatment system for simultaneously removing total nickel and COD from nickel-containing wastewater.

[0035] Among them: water inlet pump-1, biochar adsorption tower-2, modified tea residue biochar-3, lifting pump-4, resin adsorption tower-5, malonic acid modified polystyrene resin-6, drainage pump-7. DETAILED DESCRIPTION

[0036] In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

[0037] Embodiment 1:

[0038] A technical solution for removing total nickel and COD from nickel-containing wastewater includes a water inlet pump, a biochar adsorption tower, modified tea residue biochar, a lifting pump, a resin adsorption tower, malonic acid-modified polystyrene resin, and a drainage pump.

[0039] The nickel-containing wastewater is the effluent from the lime precipitation process, and the water quality characteristics of the nickel-containing wastewater are: total nickel is 7.1 mg / L, and COD is 53 mg / L.

[0040] The nickel-containing wastewater enters the modified tea residue biochar adsorption tower via an inlet pump. Modified tea residue biochar is placed in the tower. The modified tea residue biochar accounts for 95% of the total tower volume. The nickel-containing wastewater resides in the tower for 45 minutes. After 678 hours of stable operation, the tower is backwashed for 15 minutes. After treatment, the total nickel content is 6.2 mg / L and the COD content is 25 mg / L.

[0041] The modified tea residue biochar is specially synthesized and prepared according to the water quality characteristics of nickel-containing wastewater: 1) Raw material selection: tea residue waste is used as the biochar raw material, and a sodium chloride solution with a mass ratio of 3% is prepared. The tea residue waste is placed in the sodium chloride solution and soaked for 100 minutes. After being taken out and dried, it is placed in a 105°C oven for 4 hours and cooled naturally. 2) Carbonization: The tea residue waste is placed in a muffle furnace, heated to 695°C at 7°C / min, pyrolyzed for 90 to 105 minutes, and cooled naturally to form tea residue biochar. The tea residue biochar is placed in a grinder and ground into fine powder. The 200-mesh tea residue biochar is screened. 3) Secondary modification: 200-mesh chitosan is screened, and the tea residue biochar and chitosan are mixed in a mass ratio of 5:1 to form a mixture. A 7% aluminum sulfate solution is prepared. The mixture was immersed in aluminum sulfate solution at a liquid-solid ratio (volume ratio) of 5:1 for 12 hours, filtered and dried, placed in a muffle furnace, and heated to 495°C at 7°C / min, kept at this temperature for 85 minutes, and cooled naturally to form modified tea residue biochar. The surface area of ​​the modified tea residue biochar catalyst is 161.8m 2 / g, the prepared modified tea residue biochar has good adsorption performance and greatly improves the ability to adsorb total nickel and COD.

[0042] After passing through the modified tea residue biochar adsorption tower, the nickel-containing wastewater enters the resin adsorption tower via a lift pump. The malonic acid-modified polystyrene resin accounts for 90% of the total adsorption tower volume (by volume). The nickel-containing wastewater resides in the resin adsorption tower for 37 minutes.

[0043] The malonic acid-modified polystyrene resin is specially prepared according to the water quality characteristics of nickel-containing wastewater. 1) Tetrahydrofuran is added to the reactor, and 945g of diethyl malonate is added to each liter of tetrahydrofuran solution, stirred for 22 minutes, and after complete dissolution, 3.4g of sodium hydride and 630g of chloromethylated polystyrene are added. The reactor is heated to 72°C and refluxed for 20 hours. 2) After the reaction is completed, the resin is cooled and filtered, and washed with petroleum ether 4 times, acetone 4 times, and clean water 4 times, respectively. It is dried at 65°C for 3 hours and cooled to obtain malonic acid-modified polystyrene. The saturated adsorption capacity of the malonic acid-modified polystyrene resin for total nickel ions is 1.7mg / g.

[0044] The nickel-containing wastewater passes through the resin adsorption tower and is discharged through the drainage pump to meet the standards.

[0045] After the nickel-containing wastewater is treated by the process of the present invention, the total nickel content of the effluent is 0.1 mg / L and the COD content is 15 mg / L.

[0046] Example 2:

[0047] A technical solution for removing total nickel and COD from nickel-containing wastewater includes a water inlet pump, a biochar adsorption tower, modified tea residue biochar, a lifting pump, a resin adsorption tower, malonic acid-modified polystyrene resin, and a drainage pump.

[0048] The nickel-containing wastewater is the effluent from the lime precipitation process, and the water quality characteristics of the nickel-containing wastewater are: total nickel is 4.5 mg / L, and COD is 47 mg / L.

[0049] The nickel-containing wastewater enters the modified tea residue biochar adsorption tower via an inlet pump. Modified tea residue biochar is placed in the tower. The modified tea residue biochar accounts for 85% of the total tower volume. The nickel-containing wastewater resides in the tower for 34 minutes. After 678 to 782 hours of stable operation, the tower is backwashed for 10 to 15 minutes. After treatment, the total nickel content is 4.2 mg / L and the COD content is 24 mg / L.

[0050] The modified tea residue biochar is specially synthesized and prepared according to the water quality characteristics of nickel-containing wastewater: 1) Raw material selection: Using tea residue waste as biochar raw material, prepare a sodium chloride solution with a mass ratio of 1 to 3%, soak the tea residue waste in the sodium chloride solution for 100 minutes, take it out and dry it, place it in a 105°C oven for 3 hours, and cool it naturally; 2) Carbonization: Put the tea residue waste into a muffle furnace, heat it to 678°C at 6°C / min, pyrolyze it for 98 minutes, cool it naturally to form tea residue biochar, put the tea residue biochar into a grinder and grind it into fine powder, and screen the 200-mesh tea residue biochar. 3) Secondary modification: Screen 200-mesh chitosan, mix the tea residue biochar and chitosan in a mass ratio of 6:1 to form a mixture, and prepare a 5% aluminum sulfate solution by mass. The mixture was immersed in aluminum sulfate solution at a liquid-solid ratio (volume ratio) of 4:1 for 10 hours, filtered and dried, placed in a muffle furnace, heated to 478°C at 7°C / min, kept constant for 75 minutes, and cooled naturally. The modified tea residue biochar was formed after two modifications. The surface area of ​​the modified tea residue biochar catalyst was 139.2m 2 / g, the prepared modified tea residue biochar has good adsorption performance and greatly improves the ability to adsorb total nickel and COD.

[0051] After passing through the modified tea residue biochar adsorption tower, the nickel-containing wastewater enters the resin adsorption tower via a lift pump. The malonic acid-modified polystyrene resin accounts for 83% of the total adsorption tower volume (by volume). The nickel-containing wastewater resides in the resin adsorption tower for 29 minutes.

[0052] The malonic acid-modified polystyrene resin is specially prepared according to the water quality characteristics of nickel-containing wastewater. 1) Tetrahydrofuran is added to the reactor, and 811g of diethyl malonate is added to each liter of tetrahydrofuran solution, stirred for 19 minutes, and after complete dissolution, 2.6g of sodium hydride and 498g of chloromethylated polystyrene are added. The reactor is heated to 72°C and refluxed for 20 hours. 2) After the reaction is completed, the resin is cooled and filtered, and washed with petroleum ether 3 times, acetone 3 times, and clean water 3 times, and dried at 65°C for 2 hours to obtain malonic acid-modified polystyrene. The saturated adsorption capacity of the malonic acid-modified polystyrene resin for total nickel ions is 1.3mg / g.

[0053] The nickel-containing wastewater passes through the resin adsorption tower and is discharged through the drainage pump to meet the standards.

[0054] After the nickel-containing wastewater is treated by the process of the present invention, the total nickel content of the effluent is 0.2 mg / L and the COD content is 17 mg / L.

[0055] In summary, the present invention proposes for the first time a complete technical solution for deep treatment of nickel-containing wastewater, and adopts biochar and other processes to solve the problem of heavy metal and organic matter pollution of the environment in nickel-containing wastewater. Therefore, the present invention belongs to a green and low-carbon steel production process system.

[0056] Of course, those skilled in the art should realize that the above embodiments are only used to illustrate the present invention and are not used to limit the present invention. As long as they are within the scope of the essential spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A method for removing total nickel and COD from nickel-containing wastewater, wherein the nickel-containing wastewater is effluent from a lime precipitation process, and the water quality characteristics of the nickel-containing wastewater are: total nickel of 3.4-7.1 mg / L, and COD of 45-53 mg / L, characterized in that: The steps include: (1) The nickel-containing wastewater enters the modified tea residue biochar adsorption tower, and the modified tea residue biochar is placed in the modified tea residue biochar adsorption tower. The modified tea residue biochar occupies 80-95% of the volume of the entire modified tea residue biochar adsorption tower; the surface area of ​​the modified tea residue biochar is 124.7-165.8 m 2 / g; The modified tea residue biochar is specially synthesized and prepared according to the water quality characteristics of nickel-containing wastewater, comprising the following steps: 1) selecting raw materials: using tea residue waste as the biochar raw material, preparing a sodium chloride solution with a mass ratio of 1-3%, soaking the tea residue waste in the sodium chloride solution, drying, baking, and cooling; 2) Carbonization: tea residue waste is placed in a muffle furnace, heated to 655-695°C at a rate of 5-7°C / min, pyrolyzed for 90-105 min, cooled to form tea residue biochar, and the tea residue biochar is placed in a grinder and ground into fine powder; 3) Modification: 100-200 mesh chitosan is screened, tea residue biochar and chitosan are mixed in a mass ratio of (5-8):1 to form a mixture, and an aluminum sulfate solution with a mass ratio of 4-7% is prepared; the mixture is immersed in the aluminum sulfate solution in a liquid-solid ratio (volume ratio) of (4-5):1, immersed, dried, placed in a muffle furnace, heated to 465-495°C at 7-9°C / min, kept at a constant temperature for 65-85 min, cooled, and formed modified tea residue biochar; (2) After passing through the modified tea residue biochar adsorption tower, the nickel-containing wastewater enters the resin adsorption tower. The resin adsorption tower is equipped with a malonic acid-modified polystyrene resin, which accounts for 75-90% of the entire adsorption tower by volume. The saturated adsorption capacity of the malonic acid-modified polystyrene resin for total nickel ions is 1.2-1.7 mg / g. The malonic acid-modified polystyrene resin is specially prepared according to the water quality characteristics of nickel-containing wastewater, comprising the following steps: 1) adding tetrahydrofuran to a reactor, adding 789-945 g of diethyl malonate per liter of tetrahydrofuran solution, stirring for 15-22 minutes, and adding 2.1-3.4 g of sodium hydride and 450-630 g of chloromethylated polystyrene after complete dissolution, heating the reactor to 68-72° C., and reflux for 18-20 hours; 2) after the reaction is completed, cooling, filtering the resin, washing with petroleum ether 2-4 times, acetone 2-4 times, and clean water 2-4 times, respectively, and drying at 65° C. for 2-3 hours to obtain the malonic acid-modified polystyrene; (3) Nickel-containing wastewater passes through a resin adsorption tower and is discharged in compliance with discharge standards.

2. a method for removing total nickel and COD in nickel-containing wastewater according to claim 1, characterized in that, In step (1), the residence time of nickel-containing wastewater in the modified tea residue biochar adsorption tower is 27 to 45 minutes.

3. a method for removing total nickel and COD in nickel-containing wastewater according to claim 1, characterized in that, In step 1), the tea residue waste is soaked in sodium chloride solution for 100-115 min, taken out and dried, placed in a 105°C oven for 2-4 h, and cooled naturally.

4. a method for removing total nickel and COD in nickel-containing wastewater according to claim 1, characterized in that, In step 2), the tea residue biochar is ground and then screened to 100-200 mesh.

5. a method for removing total nickel and COD in nickel-containing wastewater according to claim 1, characterized in that, In step 3), the immersion time is 9 to 12 hours.

6. a method for removing total nickel and COD in nickel-containing wastewater according to claim 1, characterized in that, In step (1), the modified tea residue biochar adsorption tower was backwashed after stable operation for 678 to 782 hours, and the backwash time was 10 to 15 minutes.

7. a method for removing total nickel and COD in nickel-containing wastewater according to claim 1, characterized in that, After treatment in step (1), the total nickel content of the nickel-containing wastewater is 2.5-6.2 mg / L, and the COD content is 19-27 mg / L.

8. a method for removing total nickel and COD in nickel-containing wastewater according to claim 1, characterized in that, In step (2), the residence time of the nickel-containing wastewater in the resin adsorption tower is 25 to 37 minutes.

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