Heavy metal wastewater treatment agent and preparation method thereof

Abstract

The invention relates to the technical field of heavy metal wastewater treatment, and discloses a heavy metal wastewater treatment agent and a preparation method thereof. The heavy metal wastewater treatment agent provided by the invention is prepared from the following raw materials in parts by mass: 5 to 10 parts of titanium dioxide / graphite phase carbon nitride composite photocatalyst, 10 to 20 parts of metal organic framework material and 20 to 30 parts of modified activated carbon. According to the heavy metal wastewater treatment agent, the removal rate of total lead can reach 99.96%, the removal rate of total chromium can reach 99.97%, the removal rate of total cadmium can reach 99.94%, the removal rate of total mercury can reach 99.96%, and the heavy metal wastewater treatment agent has a good heavy metal removal effect and can be applied to heavy metal wastewater treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of heavy metal wastewater treatment, and more particularly to a heavy metal wastewater treatment agent and a preparation method thereof. Background Art

[0002] As typical pollutants generated during industrial production processes, heavy metal wastewater mainly comes from industries such as mining, electroplating, metallurgy, chemical engineering, and electronics. This type of wastewater contains heavy metals such as mercury, cadmium, lead, and chromium that pose serious hazards to the environment and human health. Existing heavy metal wastewater treatment methods mainly include chemical precipitation, ion exchange, and adsorption. However, in actual application processes, the chemical precipitation method has problems such as secondary pollution and difficult subsequent treatment, the ion exchange method has problems such as easy pollution and poisoning of ion exchange resins, and the adsorption method has problems such as limited removal ability and difficulty in effective regeneration.

[0003] With the increasingly strict environmental protection requirements, the existing heavy metal wastewater treatment methods are difficult to meet the treatment requirements of high efficiency, low cost, and no secondary pollution. Developing new heavy metal wastewater treatment agents has become a technical problem that needs to be urgently solved by those skilled in the art. Summary of the Invention

[0004] The purpose of the present invention is to provide a heavy metal wastewater treatment agent and a preparation method thereof, and the heavy metal wastewater treatment agent has good heavy metal removal effects.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention:

[0007] A heavy metal wastewater treatment agent, comprising the following raw materials in parts by mass:

[0008] 5 - 10 parts of titanium dioxide / graphite phase carbon nitride composite photocatalyst, 10 - 20 parts of metal-organic framework material, and 20 - 30 parts of modified activated carbon.

[0009] Further, the preparation method of the titanium dioxide / graphite phase carbon nitride composite photocatalyst comprises the following steps:

[0010] 1) Calcining melamine to obtain graphite phase carbon nitride;

[0011] 2) Placing the graphite phase carbon nitride obtained in step 1) in a ferric chloride solution, impregnating and modifying, and then calcining to obtain iron-modified graphite phase carbon nitride;

[0012] 3) Mixing the iron-modified graphite phase carbon nitride obtained in step 2) with titanium dioxide, and grinding to obtain the titanium dioxide / graphite phase carbon nitride composite photocatalyst.

[0013] Further, in step 1), the calcination is carried out at 550 - 650 °C for 3 - 5 h.

[0014] Further, in step 2), the concentration of the iron chloride solution is 0.5 mol·L -1 .

[0015] Further, in step 2), the mass - to - volume ratio of the graphitic carbon nitride to the iron chloride solution is 1 g∶10 mL.

[0016] Further, in step 2), the impregnation modification is carried out at 60 - 80 °C for 1 - 3 h.

[0017] Further, in step 2), the calcination is carried out at 300 - 400 °C for 20 - 40 min.

[0018] Further, in step 3), the mass ratio of the iron - modified graphitic carbon nitride to titanium dioxide is (2 - 3)∶1.

[0019] Further, the preparation method of the metal - organic framework material includes the following steps:

[0020] 1) Put nickel nitrate and iron nitrate into N,N - dimethylformamide and disperse them by ultrasonic wave to obtain a metal mixed solution;

[0021] 2) Put 2 - methylimidazole dicarboxylic acid and 1,3 - benzenedicarboxylic acid into N,N - dimethylformamide and disperse them by ultrasonic wave to obtain an organic ligand solution;

[0022] 3) Drop the metal mixed solution obtained in step 1) into the organic ligand solution obtained in step 2), react, let it stand, and centrifuge to obtain the metal - organic framework material.

[0023] Further, in step 1), the molar ratio of nickel nitrate, iron nitrate to N,N - dimethylformamide is (1 - 2)∶(1 - 3)∶10.

[0024] Further, in step 2), the molar ratio of 2 - methylimidazole dicarboxylic acid, 1,3 - benzenedicarboxylic acid to N,N - dimethylformamide is (0.5 - 1.5)∶(0.5 - 1.5)∶10.

[0025] Further, in step 3), the volume ratio of the metal mixed solution to the organic ligand solution is 1∶(2 - 3).

[0026] Further, in step 3), the reaction is carried out at 120 - 160 °C for 2 - 3 h.

[0027] Further, in step 3), the standing is carried out at room temperature for 6 - 8 h.

[0028] Further, the preparation method of the modified activated carbon comprises the following steps:

[0029] Calcine the activated carbon to obtain the modified activated carbon.

[0030] Furthermore, the calcination is carried out at 400 - 500 °C for 20 - 40 min.

[0031] The second technical solution of the present invention:

[0032] The preparation method of the above-mentioned heavy metal wastewater treatment agent comprises the following steps:

[0033] 1) Mix the titanium dioxide / graphite phase carbon nitride composite photocatalyst, the metal-organic framework material and the modified activated carbon, grind them, and then calcine at 300 - 400 °C for 10 - 20 min to obtain the heavy metal wastewater treatment agent precursor;

[0034] 2) Place the heavy metal wastewater treatment agent precursor obtained in step 1) in a silane coupling agent and let it stand at room temperature for 1 - 3 h to obtain the heavy metal wastewater treatment agent.

[0035] The third technical solution of the present invention:

[0036] The application of the above-mentioned heavy metal wastewater treatment agent in the treatment of heavy metal wastewater.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] The heavy metal wastewater treatment agent provided by the present invention can achieve a removal rate of 99.96% for total lead, 99.97% for total chromium, 99.94% for total cadmium, and 99.96% for total mercury, has a good heavy metal removal effect, and can be applied to the treatment of heavy metal wastewater. Specific embodiments

[0039] The various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention. It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0040] In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0041] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to those documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0042] Without departing from the scope or spirit of this invention, various improvements and changes can be made to the specific embodiments of the description of this invention, which are obvious to those skilled in the art. Other embodiments obtained from the description of this invention are obvious to those skilled in the art. The description of this invention and the examples are merely exemplary.

[0043] Regarding the use of "comprising", "including", "having", "containing", etc. in this text, they are all open-ended terms, meaning including but not limited to.

[0044] In the following examples, a preparation method of a heavy metal wastewater treatment agent includes the following steps:

[0045] 1. Preparation of titanium dioxide / graphitic carbon nitride composite photocatalyst

[0046] 1) Place melamine in a crucible and calcine it at 550 - 650 °C for 3 - 5 h to obtain graphitic carbon nitride;

[0047] 2) According to the mass-volume ratio of graphitic carbon nitride to ferric chloride solution of 1 g∶10 mL, place the graphitic carbon nitride obtained in step 1) in a ferric chloride solution with a concentration of 0.5 mol·L -1 and impregnate and modify it at 60 - 80 °C for 1 - 3 h. Then, under the protection of an inert gas, calcine it at 300 - 400 °C for 20 - 40 min to obtain iron-modified graphitic carbon nitride;

[0048] 3) According to the mass ratio of iron-modified graphitic carbon nitride to titanium dioxide of (2 - 3)∶1, mix the iron-modified graphitic carbon nitride obtained in step 2) and titanium dioxide, and grind to obtain the titanium dioxide / graphitic carbon nitride composite photocatalyst;

[0049] 2. Preparation of metal-organic framework materials

[0050] 1) According to the molar ratio of nickel nitrate, iron nitrate and N,N-dimethylformamide of (1 - 2)∶(1 - 3)∶10, place nickel nitrate and iron nitrate in N,N-dimethylformamide and ultrasonically disperse for 30 min to obtain a metal mixed solution;

[0051] 2) According to the molar ratio of 2-methylimidazole dicarboxylic acid, 1,3-benzenedicarboxylic acid and N,N-dimethylformamide being (0.5-1.5):(0.5-1.5):10, place 2-methylimidazole dicarboxylic acid and 1,3-benzenedicarboxylic acid in N,N-dimethylformamide, and ultrasonically disperse for 30 min to obtain an organic ligand solution;

[0052] 3) According to the volume ratio of the metal mixed solution to the organic ligand solution being 1:(2-3), control the dropping rate to be 30 d·min -1 , drop the metal mixed solution obtained in step 1) into the organic ligand solution obtained in step 2), react at 120-160 °C for 2-3 h, then let it stand at room temperature for 6-8 h, and centrifuge to obtain the metal-organic framework material;

[0053] 3. Preparation of modified activated carbon

[0054] Place the activated carbon in a crucible and calcine at 400-500 °C for 20-40 min to obtain the modified activated carbon;

[0055] 4. Preparation of heavy metal wastewater treatment agent

[0056] 1) Weigh the raw materials according to the following mass parts:

[0057] 5-10 parts of titanium dioxide / graphitic carbon nitride composite photocatalyst, 10-20 parts of metal-organic framework material, 20-30 parts of modified activated carbon;

[0058] 2) Mix the raw materials weighed in step 1), grind, and then calcine at 300-400 °C for 10-20 min to obtain a heavy metal wastewater treatment agent precursor;

[0059] 3) Place the heavy metal wastewater treatment agent precursor obtained in step 2) in a silane coupling agent and let it stand at room temperature for 1-3 h to obtain the heavy metal wastewater treatment agent.

[0060] Example 1

[0061] A heavy metal wastewater treatment agent

[0062] 1. Preparation of titanium dioxide / graphitic carbon nitride composite photocatalyst

[0063] 1) Place melamine in a crucible and calcine at 550 °C for 3 h to obtain graphitic carbon nitride;

[0064] 2) According to the mass-volume ratio of graphitic carbon nitride to ferric chloride solution being 1 g:10 mL, place the graphitic carbon nitride obtained in step 1) in a solution with a concentration of 0.5 mol·L -1In a ferric chloride solution, it was impregnated and modified at 60 °C for 1 h, and then calcined at 300 °C for 20 min under nitrogen protection to obtain iron-modified graphitic carbon nitride;

[0065] 3) According to the mass ratio of iron-modified graphitic carbon nitride to titanium dioxide being 2:1, the iron-modified graphitic carbon nitride obtained in step 2) and titanium dioxide were mixed and ground to obtain the titanium dioxide / graphitic carbon nitride composite photocatalyst;

[0066] 2. Preparation of metal-organic framework materials

[0067] 1) According to the molar ratio of nickel nitrate, iron nitrate and N,N-dimethylformamide being 1:1:10, nickel nitrate and iron nitrate were placed in N,N-dimethylformamide and ultrasonically dispersed for 30 min to obtain a metal mixed solution;

[0068] 2) According to the molar ratio of 2-methylimidazole dicarboxylic acid, 1,3-benzenedicarboxylic acid and N,N-dimethylformamide being 0.5:0.5:10, 2-methylimidazole dicarboxylic acid and 1,3-benzenedicarboxylic acid were placed in N,N-dimethylformamide and ultrasonically dispersed for 30 min to obtain an organic ligand solution;

[0069] 3) According to the volume ratio of the metal mixed solution to the organic ligand solution being 1:2, and controlling the dropping rate to be 30 d·min -1 , the metal mixed solution obtained in step 1) was added dropwise to the organic ligand solution obtained in step 2), reacted at 120 °C for 2 h, and then left to stand at room temperature for 6 h, centrifuged to obtain the metal-organic framework material;

[0070] 3. Preparation of modified activated carbon

[0071] The activated carbon was placed in a crucible and calcined at 400 °C for 20 min to obtain the modified activated carbon;

[0072] 4. Preparation of heavy metal wastewater treatment agent

[0073] 1) Weigh the raw materials according to the following parts by mass:

[0074] 5 parts of titanium dioxide / graphitic carbon nitride composite photocatalyst, 10 parts of metal-organic framework material, 20 parts of modified activated carbon;

[0075] 2) Mix the raw materials weighed in step 1), grind them, and then calcine at 300 °C for 10 min to obtain a heavy metal wastewater treatment agent precursor;

[0076] 3) Place the heavy metal wastewater treatment agent precursor obtained in step 2) in a silane coupling agent and leave it to stand at room temperature for 1 h to obtain the heavy metal wastewater treatment agent.

[0077] Example 2

[0078] A heavy metal wastewater treatment agent

[0079] 1. Preparation of titanium dioxide / graphitic carbon nitride composite photocatalyst

[0080] 1) Place melamine in a crucible and calcine it at 500 °C for 4 h to obtain graphitic carbon nitride;

[0081] 2) According to the mass-volume ratio of graphitic carbon nitride to ferric chloride solution of 1 g∶10 mL, place the graphitic carbon nitride obtained in step 1) in a ferric chloride solution with a concentration of 0.5 mol·L -1 and impregnate and modify it at 70 °C for 2 h. Then, under nitrogen protection, calcine it at 350 °C for 30 min to obtain iron-modified graphitic carbon nitride;

[0082] 3) According to the mass ratio of iron-modified graphitic carbon nitride to titanium dioxide of 2.5∶1, mix the iron-modified graphitic carbon nitride obtained in step 2) and titanium dioxide, and grind them to obtain the titanium dioxide / graphitic carbon nitride composite photocatalyst;

[0083] 2. Preparation of metal-organic framework materials

[0084] 1) According to the molar ratio of nickel nitrate, iron nitrate and N,N-dimethylformamide of 1.5∶2∶10, place nickel nitrate and iron nitrate in N,N-dimethylformamide and ultrasonically disperse them for 30 min to obtain a metal mixed solution;

[0085] 2) According to the molar ratio of 2-methylimidazole dicarboxylic acid, 1,3-benzenedicarboxylic acid and N,N-dimethylformamide of 1∶1∶10, place 2-methylimidazole dicarboxylic acid and 1,3-benzenedicarboxylic acid in N,N-dimethylformamide and ultrasonically disperse them for 30 min to obtain an organic ligand solution;

[0086] 3) According to the volume ratio of the metal mixed solution to the organic ligand solution of 1∶2.5, control the dropping rate to 30 d·min -1 , drop the metal mixed solution obtained in step 1) into the organic ligand solution obtained in step 2), react at 140 °C for 2.5 h, then let it stand at room temperature for 7 h, and centrifuge to obtain the metal-organic framework material;

[0087] 3. Preparation of modified activated carbon

[0088] Place the activated carbon in a crucible and calcine it at 450 °C for 30 min to obtain the modified activated carbon;

[0089] 4. Preparation of heavy metal wastewater treatment agent

[0090] 1) Weigh the raw materials according to the following parts by mass:

[0091] 8 parts of titanium dioxide / graphite-phase carbon nitride composite photocatalyst, 15 parts of metal-organic framework material, and 25 parts of modified activated carbon;

[0092] 2) Mix the raw materials weighed in step 1), grind them, and then calcine at 350 °C for 15 min to obtain a heavy metal wastewater treatment agent precursor;

[0093] 3) Place the heavy metal wastewater treatment agent precursor obtained in step 2) in a silane coupling agent and let it stand at room temperature for 2 h to obtain the heavy metal wastewater treatment agent.

[0094] Example 3

[0095] A heavy metal wastewater treatment agent

[0096] 1. Preparation of titanium dioxide / graphite-phase carbon nitride composite photocatalyst

[0097] 1) Place melamine in a crucible and calcine at 650 °C for 5 h to obtain graphite-phase carbon nitride;

[0098] 2) According to the mass-volume ratio of graphite-phase carbon nitride to ferric chloride solution of 1 g∶10 mL, place the graphite-phase carbon nitride obtained in step 1) in a ferric chloride solution with a concentration of 0.5 mol·L -1 and impregnate and modify it at 80 °C for 3 h, and then calcine at 400 °C for 40 min under nitrogen protection to obtain iron-modified graphite-phase carbon nitride;

[0099] 3) According to the mass ratio of iron-modified graphite-phase carbon nitride to titanium dioxide of 3∶1, mix the iron-modified graphite-phase carbon nitride and titanium dioxide obtained in step 2) and grind them to obtain the titanium dioxide / graphite-phase carbon nitride composite photocatalyst;

[0100] 2. Preparation of metal-organic framework material

[0101] 1) According to the molar ratio of nickel nitrate, ferric nitrate, and N,N-dimethylformamide of 2∶3∶10, place nickel nitrate and ferric nitrate in N,N-dimethylformamide and ultrasonically disperse for 30 min to obtain a metal mixed solution;

[0102] 2) According to the molar ratio of 2-methylimidazole dicarboxylic acid, 1,3-benzenedicarboxylic acid, and N,N-dimethylformamide of 1.5∶1.5∶10, place 2-methylimidazole dicarboxylic acid and 1,3-benzenedicarboxylic acid in N,N-dimethylformamide and ultrasonically disperse for 30 min to obtain an organic ligand solution;

[0103] 3) According to the volume ratio of the metal mixed solution to the organic ligand solution of 1∶3, control the dropping rate to 30 d·min -1, the metal mixed solution obtained in step 1) was added dropwise to the organic ligand solution obtained in step 2), reacted at 160 °C for 3 h, then left to stand at room temperature for 8 h, and centrifuged to obtain the metal-organic framework material;

[0104] 3. Preparation of modified activated carbon

[0105] The activated carbon was placed in a crucible and calcined at 500 °C for 40 min to obtain the modified activated carbon;

[0106] 4. Preparation of heavy metal wastewater treatment agent

[0107] 1) Weigh the raw materials according to the following mass parts:

[0108] 10 parts of titanium dioxide / graphite phase carbon nitride composite photocatalyst, 20 parts of metal-organic framework material, and 30 parts of modified activated carbon;

[0109] 2) Mix the raw materials weighed in step 1), grind them, and then calcine at 400 °C for 20 min to obtain the heavy metal wastewater treatment agent precursor;

[0110] 3) Place the heavy metal wastewater treatment agent precursor obtained in step 2) in a silane coupling agent and leave it to stand at room temperature for 3 h to obtain the heavy metal wastewater treatment agent.

[0111] Comparative Example 1

[0112] A heavy metal wastewater treatment agent

[0113] 1. Preparation of titanium dioxide / graphite phase carbon nitride composite photocatalyst

[0114] 1) Place melamine in a crucible and calcine at 500 °C for 4 h to obtain graphite phase carbon nitride;

[0115] 2) According to the mass ratio of graphite phase carbon nitride to titanium dioxide being 2.5:1, mix the graphite phase carbon nitride obtained in step 1) and titanium dioxide, and grind to obtain the titanium dioxide / graphite phase carbon nitride composite photocatalyst;

[0116] 2. Preparation of metal-organic framework material

[0117] 1) According to the molar ratio of nickel nitrate, iron nitrate and N,N-dimethylformamide being 1.5:2:10, place nickel nitrate and iron nitrate in N,N-dimethylformamide, and ultrasonically disperse for 30 min to obtain a metal mixed solution;

[0118] 2) According to the molar ratio of 2-methylimidazole dicarboxylic acid, 1,3-benzenedicarboxylic acid and N,N-dimethylformamide being 1∶1∶10, place 2-methylimidazole dicarboxylic acid and 1,3-benzenedicarboxylic acid in N,N-dimethylformamide, and ultrasonically disperse for 30 min to obtain an organic ligand solution;

[0119] 3) According to the volume ratio of the metal mixed solution to the organic ligand solution being 1∶2.5, control the dropping rate to be 30 d·min -1 , drop the metal mixed solution obtained in step 1) into the organic ligand solution obtained in step 2), react at 140 °C for 2.5 h, then let it stand at room temperature for 7 h, and centrifuge to obtain the metal-organic framework material;

[0120] 3. Preparation of modified activated carbon

[0121] Place the activated carbon in a crucible and calcine at 450 °C for 30 min to obtain the modified activated carbon;

[0122] 4. Preparation of heavy metal wastewater treatment agent

[0123] 1) Weigh the raw materials according to the following mass parts:

[0124] 8 parts of titanium dioxide / graphite phase carbon nitride composite photocatalyst, 15 parts of metal-organic framework material, and 25 parts of modified activated carbon;

[0125] 2) Mix the raw materials weighed in step 1), grind, and then calcine at 350 °C for 15 min to obtain a heavy metal wastewater treatment agent precursor;

[0126] 3) Place the heavy metal wastewater treatment agent precursor obtained in step 2) in a silane coupling agent and let it stand at room temperature for 2 h to obtain the heavy metal wastewater treatment agent.

[0127] Comparative Example 2

[0128] A heavy metal wastewater treatment agent

[0129] 1. Preparation of titanium dioxide / graphite phase carbon nitride composite photocatalyst

[0130] 1) Place melamine in a crucible and calcine at 500 °C for 4 h to obtain graphite phase carbon nitride;

[0131] 2) According to the mass-volume ratio of graphite phase carbon nitride to ferric chloride solution being 1 g∶10 mL, place the graphite phase carbon nitride obtained in step 1) in a ferric chloride solution with a concentration of 0.5 mol·L -1 , and impregnate and modify at 70 °C for 2 h to obtain iron-modified graphite phase carbon nitride;

[0132] 3) Mix the iron-modified graphitic carbon nitride obtained in step 2) and titanium dioxide according to the mass ratio of iron-modified graphitic carbon nitride to titanium dioxide of 2.5:1, and grind to obtain the titanium dioxide / graphitic carbon nitride composite photocatalyst;

[0133] 2. Preparation of metal-organic framework material

[0134] 1) Place nickel nitrate and iron nitrate in N,N-dimethylformamide according to the molar ratio of nickel nitrate, iron nitrate to N,N-dimethylformamide of 1.5:2:10, and ultrasonically disperse for 30 min to obtain a metal mixed solution;

[0135] 2) Place 2-methylimidazole dicarboxylic acid and 1,3-benzenedicarboxylic acid in N,N-dimethylformamide according to the molar ratio of 2-methylimidazole dicarboxylic acid, 1,3-benzenedicarboxylic acid to N,N-dimethylformamide of 1:1:10, and ultrasonically disperse for 30 min to obtain an organic ligand solution;

[0136] 3) According to the volume ratio of the metal mixed solution to the organic ligand solution of 1:2.5, control the dropping rate to 30 d·min -1 , drop the metal mixed solution obtained in step 1) into the organic ligand solution obtained in step 2), react at 140 °C for 2.5 h, then let it stand at room temperature for 7 h, and centrifuge to obtain the metal-organic framework material;

[0137] 3. Preparation of modified activated carbon

[0138] Place the activated carbon in a crucible and calcine at 450 °C for 30 min to obtain the modified activated carbon;

[0139] 4. Preparation of heavy metal wastewater treatment agent

[0140] 1) Weigh the raw materials according to the following parts by mass:

[0141] 8 parts of titanium dioxide / graphitic carbon nitride composite photocatalyst, 15 parts of metal-organic framework material, 25 parts of modified activated carbon;

[0142] 2) Mix the raw materials weighed in step 1), grind, and then calcine at 350 °C for 15 min to obtain a heavy metal wastewater treatment agent precursor;

[0143] 3) Place the heavy metal wastewater treatment agent precursor obtained in step 2) in a silane coupling agent and let it stand at room temperature for 2 h to obtain the heavy metal wastewater treatment agent.

[0144] Comparative Example 3

[0145] A heavy metal wastewater treatment agent

[0146] 1. Preparation of metal-organic framework material

[0147] 1) According to the molar ratio of nickel nitrate, iron nitrate and N,N-dimethylformamide being 1.5∶2∶10, place nickel nitrate and iron nitrate in N,N-dimethylformamide, and ultrasonically disperse for 30 min to obtain a metal mixed solution;

[0148] 2) According to the molar ratio of 2-methylimidazole dicarboxylic acid, 1,3-benzenedicarboxylic acid and N,N-dimethylformamide being 1∶1∶10, place 2-methylimidazole dicarboxylic acid and 1,3-benzenedicarboxylic acid in N,N-dimethylformamide, and ultrasonically disperse for 30 min to obtain an organic ligand solution;

[0149] 3) According to the volume ratio of the metal mixed solution and the organic ligand solution being 1∶2.5, control the dropping rate to be 30 d·min -1 , add the metal mixed solution obtained in step 1) dropwise to the organic ligand solution obtained in step 2), react at 140 °C for 2.5 h, then let it stand at room temperature for 7 h, and centrifuge to obtain the metal-organic framework material;

[0150] 2. Preparation of modified activated carbon

[0151] Place the activated carbon in a crucible and calcine at 450 °C for 30 min to obtain the modified activated carbon;

[0152] 3. Preparation of heavy metal wastewater treatment agent

[0153] 1) Weigh the raw materials according to the following parts by mass:

[0154] 8 parts of titanium dioxide, 15 parts of metal-organic framework material, 25 parts of modified activated carbon;

[0155] 2) Mix the raw materials weighed in step 1), grind them, and then calcine at 350 °C for 15 min to obtain a heavy metal wastewater treatment agent precursor;

[0156] 3) Place the heavy metal wastewater treatment agent precursor obtained in step 2) in a silane coupling agent and let it stand at room temperature for 2 h to obtain the heavy metal wastewater treatment agent.

[0157] Comparative Example 4

[0158] A heavy metal wastewater treatment agent

[0159] 1. Preparation of titanium dioxide / graphitic carbon nitride composite photocatalyst

[0160] 1) Place melamine in a crucible and calcine at 500 °C for 4 h to obtain graphitic carbon nitride;

[0161] 2) According to the mass-volume ratio of graphitic carbon nitride to ferric chloride solution being 1 g∶10 mL, place the graphitic carbon nitride obtained in step 1) into a ferric chloride solution with a concentration of 0.5 mol·L -1 and impregnate and modify it at 70 °C for 2 h. Then, under nitrogen protection, calcine it at 350 °C for 30 min to obtain iron-modified graphitic carbon nitride;

[0162] 3) According to the mass ratio of iron-modified graphitic carbon nitride to titanium dioxide being 2.5∶1, mix the iron-modified graphitic carbon nitride and titanium dioxide obtained in step 2), and grind them to obtain the titanium dioxide / graphitic carbon nitride composite photocatalyst;

[0163] 2. Preparation of metal-organic framework material

[0164] 1) According to the molar ratio of nickel nitrate to N,N-dimethylformamide being 1.5∶10, place nickel nitrate in N,N-dimethylformamide and ultrasonically disperse it for 30 min to obtain a metal mixed solution;

[0165] 2) According to the molar ratio of 2-methylimidazole dicarboxylic acid, 1,3-benzenedicarboxylic acid to N,N-dimethylformamide being 1∶1∶10, place 2-methylimidazole dicarboxylic acid and 1,3-benzenedicarboxylic acid in N,N-dimethylformamide and ultrasonically disperse it for 30 min to obtain an organic ligand solution;

[0166] 3) According to the volume ratio of the metal mixed solution to the organic ligand solution being 1∶2.5, control the dropping rate to be 30 d·min -1 , and drop the metal mixed solution obtained in step 1) into the organic ligand solution obtained in step 2), react at 140 °C for 2.5 h, then let it stand at room temperature for 7 h, and centrifuge to obtain the metal-organic framework material;

[0167] 3. Preparation of modified activated carbon

[0168] Place the activated carbon in a crucible and calcine it at 450 °C for 30 min to obtain the modified activated carbon;

[0169] 4. Preparation of heavy metal wastewater treatment agent

[0170] 1) Weigh the raw materials according to the following parts by mass:

[0171] 8 parts of titanium dioxide / graphitic carbon nitride composite photocatalyst, 15 parts of metal-organic framework material, and 25 parts of modified activated carbon;

[0172] 2) Mix the raw materials weighed in step 1), grind them, and then calcine them at 350 °C for 15 min to obtain the heavy metal wastewater treatment agent precursor;

[0173] 3) Place the precursor of the heavy metal wastewater treatment agent obtained in step 2) in a silane coupling agent and let it stand at room temperature for 2 h to obtain the heavy metal wastewater treatment agent.

[0174] Comparative Example 5

[0175] A heavy metal wastewater treatment agent

[0176] 1. Preparation of titanium dioxide / graphite carbon nitride composite photocatalyst

[0177] 1) Place melamine in a crucible and calcine it at 500 °C for 4 h to obtain graphite carbon nitride;

[0178] 2) According to the mass-volume ratio of graphite carbon nitride to iron chloride solution of 1 g∶10 mL, place the graphite carbon nitride obtained in step 1) in an iron chloride solution with a concentration of 0.5 mol·L -1 and impregnate and modify it at 70 °C for 2 h. Then, under nitrogen protection, calcine it at 350 °C for 30 min to obtain iron-modified graphite carbon nitride;

[0179] 3) According to the mass ratio of iron-modified graphite carbon nitride to titanium dioxide of 2.5∶1, mix the iron-modified graphite carbon nitride obtained in step 2) and titanium dioxide and grind them to obtain the titanium dioxide / graphite carbon nitride composite photocatalyst;

[0180] 2. Preparation of metal-organic framework materials

[0181] 1) According to the molar ratio of iron nitrate to N,N-dimethylformamide of 2∶10, place iron nitrate in N,N-dimethylformamide and ultrasonically disperse it for 30 min to obtain a metal mixed solution;

[0182] 2) According to the molar ratio of 2-methylimidazole dicarboxylic acid, 1,3-benzenedicarboxylic acid to N,N-dimethylformamide of 1∶1∶10, place 2-methylimidazole dicarboxylic acid and 1,3-benzenedicarboxylic acid in N,N-dimethylformamide and ultrasonically disperse it for 30 min to obtain an organic ligand solution;

[0183] 3) According to the volume ratio of the metal mixed solution to the organic ligand solution of 1∶2.5, control the dropping rate to 30 d·min -1 , drop the metal mixed solution obtained in step 1) into the organic ligand solution obtained in step 2), react at 140 °C for 2.5 h, then let it stand at room temperature for 7 h, and centrifuge to obtain the metal-organic framework material;

[0184] 3. Preparation of modified activated carbon

[0185] Place the activated carbon in a crucible and calcine it at 450 °C for 30 min to obtain the modified activated carbon;

[0186] 4. Preparation of Heavy Metal Wastewater Treatment Agent

[0187] 1) Weigh the raw materials according to the following parts by mass:

[0188] 8 parts of titanium dioxide / graphitic carbon nitride composite photocatalyst, 15 parts of metal-organic framework material, and 25 parts of modified activated carbon;

[0189] 2) Mix the raw materials weighed in step 1), grind them, and then calcine at 350 °C for 15 min to obtain the precursor of the heavy metal wastewater treatment agent;

[0190] 3) Place the precursor of the heavy metal wastewater treatment agent obtained in step 2) in a silane coupling agent and let it stand at room temperature for 2 h to obtain the heavy metal wastewater treatment agent.

[0191] Comparative Example 6

[0192] A heavy metal wastewater treatment agent

[0193] 1. Preparation of titanium dioxide / graphitic carbon nitride composite photocatalyst

[0194] 1) Place melamine in a crucible and calcine at 500 °C for 4 h to obtain graphitic carbon nitride;

[0195] 2) According to the mass-volume ratio of graphitic carbon nitride to ferric chloride solution of 1 g∶10 mL, place the graphitic carbon nitride obtained in step 1) in a ferric chloride solution with a concentration of 0.5 mol·L -1 and impregnate and modify it at 70 °C for 2 h, and then calcine at 350 °C for 30 min under nitrogen protection to obtain iron-modified graphitic carbon nitride;

[0196] 3) According to the mass ratio of iron-modified graphitic carbon nitride to titanium dioxide of 2.5∶1, mix the iron-modified graphitic carbon nitride and titanium dioxide obtained in step 2) and grind them to obtain the titanium dioxide / graphitic carbon nitride composite photocatalyst;

[0197] 2. Preparation of metal-organic framework material

[0198] 1) According to the molar ratio of nickel nitrate, iron nitrate and N,N-dimethylformamide of 1.5∶2∶10, place nickel nitrate and iron nitrate in N,N-dimethylformamide and ultrasonically disperse for 30 min to obtain a metal mixed solution;

[0199] 2) According to the molar ratio of 1,3-benzenedicarboxylic acid to N,N-dimethylformamide of 1∶10, place 1,3-benzenedicarboxylic acid in N,N-dimethylformamide and ultrasonically disperse for 30 min to obtain an organic ligand solution;

[0200] 3) Control the dropping rate at 30 d·min according to the volume ratio of the metal mixed solution to the organic ligand solution being 1∶2.5 -1 , and drop the metal mixed solution obtained in step 1) into the organic ligand solution obtained in step 2), react at 140 °C for 2.5 h, then let it stand at room temperature for 7 h, and centrifuge to obtain the metal-organic framework material;

[0201] 3. Preparation of modified activated carbon

[0202] Place the activated carbon in a crucible and calcine it at 450 °C for 30 min to obtain the modified activated carbon;

[0203] 4. Preparation of heavy metal wastewater treatment agent

[0204] 1) Weigh the raw materials according to the following parts by mass:

[0205] 8 parts of titanium dioxide / graphite-phase carbon nitride composite photocatalyst, 15 parts of metal-organic framework material, and 25 parts of modified activated carbon;

[0206] 2) Mix the raw materials weighed in step 1), grind them, and then calcine them at 350 °C for 15 min to obtain the precursor of the heavy metal wastewater treatment agent;

[0207] 3) Place the precursor of the heavy metal wastewater treatment agent obtained in step 2) in a silane coupling agent and let it stand at room temperature for 2 h to obtain the heavy metal wastewater treatment agent.

[0208] Comparative Example 7

[0209] A heavy metal wastewater treatment agent

[0210] 1. Preparation of titanium dioxide / graphite-phase carbon nitride composite photocatalyst

[0211] 1) Place melamine in a crucible and calcine it at 500 °C for 4 h to obtain graphite-phase carbon nitride;

[0212] 2) According to the mass-volume ratio of graphite-phase carbon nitride to ferric chloride solution being 1 g∶10 mL, place the graphite-phase carbon nitride obtained in step 1) in a ferric chloride solution with a concentration of 0.5 mol·L -1 , impregnate and modify it at 70 °C for 2 h, and then calcine it at 350 °C for 30 min under nitrogen protection to obtain iron-modified graphite-phase carbon nitride;

[0213] 3) According to the mass ratio of iron-modified graphite-phase carbon nitride to titanium dioxide being 2.5∶1, mix the iron-modified graphite-phase carbon nitride obtained in step 2) and titanium dioxide, and grind them to obtain the titanium dioxide / graphite-phase carbon nitride composite photocatalyst;

[0214] 2. Preparation of metal-organic framework material

[0215] 1) According to the molar ratio of nickel nitrate, iron nitrate and N,N-dimethylformamide being 1.5∶2∶10, place nickel nitrate and iron nitrate in N,N-dimethylformamide, and ultrasonically disperse for 30 min to obtain a metal mixed solution;

[0216] 2) According to the molar ratio of 2-methylimidazole dicarboxylic acid and N,N-dimethylformamide being 1∶10, place 2-methylimidazole dicarboxylic acid in N,N-dimethylformamide, and ultrasonically disperse for 30 min to obtain an organic ligand solution;

[0217] 3) According to the volume ratio of the metal mixed solution and the organic ligand solution being 1∶2.5, control the dropping rate to be 30 d·min -1 , drop the metal mixed solution obtained in step 1) into the organic ligand solution obtained in step 2), react at 140 °C for 2.5 h, then let it stand at room temperature for 7 h, and centrifuge to obtain the metal-organic framework material;

[0218] 3. Preparation of modified activated carbon

[0219] Place the activated carbon in a crucible and calcine at 450 °C for 30 min to obtain the modified activated carbon;

[0220] 4. Preparation of heavy metal wastewater treatment agent

[0221] 1) Weigh the raw materials according to the following mass parts:

[0222] 8 parts of titanium dioxide / graphite phase carbon nitride composite photocatalyst, 15 parts of metal-organic framework material, 25 parts of modified activated carbon;

[0223] 2) Mix the raw materials weighed in step 1), grind, and then calcine at 350 °C for 15 min to obtain a heavy metal wastewater treatment agent precursor;

[0224] 3) Place the heavy metal wastewater treatment agent precursor obtained in step 2) in a silane coupling agent and let it stand at room temperature for 2 h to obtain the heavy metal wastewater treatment agent.

[0225] Control 8

[0226] A heavy metal wastewater treatment agent

[0227] 1. Preparation of titanium dioxide / graphite phase carbon nitride composite photocatalyst

[0228] 1) Place melamine in a crucible and calcine at 500 °C for 4 h to obtain graphite phase carbon nitride;

[0229] 2) According to the mass-volume ratio of graphite phase carbon nitride and ferric chloride solution being 1 g∶10 mL, place the graphite phase carbon nitride obtained in step 1) in a concentration of 0.5 mol·L-1 In a ferric chloride solution, it was impregnated and modified at 70 °C for 2 h, and then calcined at 350 °C for 30 min under nitrogen protection to obtain iron-modified graphitic carbon nitride;

[0230] 3) According to the mass ratio of iron-modified graphitic carbon nitride to titanium dioxide being 2.5∶1, the iron-modified graphitic carbon nitride obtained in step 2) and titanium dioxide were mixed and ground to obtain the titanium dioxide / graphitic carbon nitride composite photocatalyst;

[0231] 2. Preparation of modified activated carbon

[0232] The activated carbon was placed in a crucible and calcined at 450 °C for 30 min to obtain the modified activated carbon;

[0233] 3. Preparation of heavy metal wastewater treatment agent

[0234] 1) Weigh the raw materials according to the following parts by mass:

[0235] 8 parts of titanium dioxide / graphitic carbon nitride composite photocatalyst and 25 parts of modified activated carbon;

[0236] 2) Mix the raw materials weighed in step 1), grind them, and then calcine at 350 °C for 15 min to obtain the heavy metal wastewater treatment agent precursor;

[0237] 3) Place the heavy metal wastewater treatment agent precursor obtained in step 2) in a silane coupling agent and let it stand at room temperature for 2 h to obtain the heavy metal wastewater treatment agent.

[0238] Comparative Example 9

[0239] A heavy metal wastewater treatment agent

[0240] 1. Preparation of titanium dioxide / graphitic carbon nitride composite photocatalyst

[0241] 1) Place melamine in a crucible and calcine at 500 °C for 4 h to obtain graphitic carbon nitride;

[0242] 2) According to the mass-volume ratio of graphitic carbon nitride to ferric chloride solution being 1 g∶10 mL, place the graphitic carbon nitride obtained in step 1) in a ferric chloride solution with a concentration of 0.5 mol·L -1 In a ferric chloride solution, it was impregnated and modified at 70 °C for 2 h, and then calcined at 350 °C for 30 min under nitrogen protection to obtain iron-modified graphitic carbon nitride;

[0243] 3) According to the mass ratio of iron-modified graphitic carbon nitride to titanium dioxide being 2.5∶1, the iron-modified graphitic carbon nitride obtained in step 2) and titanium dioxide were mixed and ground to obtain the titanium dioxide / graphitic carbon nitride composite photocatalyst;

[0244] 2. Preparation of Metal-Organic Framework Materials

[0245] 1) According to the molar ratio of nickel nitrate, iron nitrate and N,N-dimethylformamide being 1.5∶2∶10, place nickel nitrate and iron nitrate in N,N-dimethylformamide and ultrasonically disperse for 30 min to obtain a metal mixed solution;

[0246] 2) According to the molar ratio of 2-methylimidazole dicarboxylic acid, 1,3-benzenedicarboxylic acid and N,N-dimethylformamide being 1∶1∶10, place 2-methylimidazole dicarboxylic acid and 1,3-benzenedicarboxylic acid in N,N-dimethylformamide and ultrasonically disperse for 30 min to obtain an organic ligand solution;

[0247] 3) According to the volume ratio of the metal mixed solution to the organic ligand solution being 1∶2.5, control the dropping rate to be 30 d·min -1 , drop the metal mixed solution obtained in step 1) into the organic ligand solution obtained in step 2), react at 140 °C for 2.5 h, then let it stand at room temperature for 7 h, and centrifuge to obtain the metal-organic framework material;

[0248] 3. Preparation of Heavy Metal Wastewater Treatment Agent

[0249] 1) Weigh the raw materials according to the following mass parts:

[0250] 8 parts of titanium dioxide / graphite-phase carbon nitride composite photocatalyst, 15 parts of metal-organic framework material, 25 parts of activated carbon;

[0251] 2) Mix the raw materials weighed in step 1), grind, and then calcine at 350 °C for 15 min to obtain a precursor of the heavy metal wastewater treatment agent;

[0252] 3) Place the precursor of the heavy metal wastewater treatment agent obtained in step 2) in a silane coupling agent and let it stand at room temperature for 2 h to obtain the heavy metal wastewater treatment agent.

[0253] Comparative Example 10

[0254] A Heavy Metal Wastewater Treatment Agent

[0255] 1. Preparation of Titanium Dioxide / Graphite-Phase Carbon Nitride Composite Photocatalyst

[0256] 1) Place melamine in a crucible and calcine at 500 °C for 4 h to obtain graphite-phase carbon nitride;

[0257] 2) According to the mass-volume ratio of graphite-phase carbon nitride to ferric chloride solution being 1 g∶10 mL, place the graphite-phase carbon nitride obtained in step 1) in a solution with a concentration of 0.5 mol·L -1In a ferric chloride solution, it was impregnated and modified at 70 °C for 2 h, and then calcined at 350 °C for 30 min under nitrogen protection to obtain iron-modified graphitic carbon nitride;

[0258] 3) According to the mass ratio of iron-modified graphitic carbon nitride to titanium dioxide being 2.5∶1, the iron-modified graphitic carbon nitride obtained in step 2) and titanium dioxide were mixed and ground to obtain the titanium dioxide / graphitic carbon nitride composite photocatalyst;

[0259] 2. Preparation of metal-organic framework materials

[0260] 1) According to the molar ratio of nickel nitrate, iron nitrate and N,N-dimethylformamide being 1.5∶2∶10, nickel nitrate and iron nitrate were placed in N,N-dimethylformamide and ultrasonically dispersed for 30 min to obtain a metal mixed solution;

[0261] 2) According to the molar ratio of 2-methylimidazole dicarboxylic acid, 1,3-benzenedicarboxylic acid and N,N-dimethylformamide being 1∶1∶10, 2-methylimidazole dicarboxylic acid and 1,3-benzenedicarboxylic acid were placed in N,N-dimethylformamide and ultrasonically dispersed for 30 min to obtain an organic ligand solution;

[0262] 3) According to the volume ratio of the metal mixed solution to the organic ligand solution being 1∶2.5, and controlling the dropping rate to be 30 d·min -1 , the metal mixed solution obtained in step 1) was dropped into the organic ligand solution obtained in step 2), reacted at 140 °C for 2.5 h, and then left to stand at room temperature for 7 h, and centrifuged to obtain the metal-organic framework material;

[0263] 3. Preparation of modified activated carbon

[0264] The activated carbon was placed in a crucible and calcined at 450 °C for 30 min to obtain the modified activated carbon;

[0265] 4. Preparation of heavy metal wastewater treatment agent

[0266] 1) Weigh the raw materials according to the following parts by mass:

[0267] 8 parts of titanium dioxide / graphitic carbon nitride composite photocatalyst, 15 parts of metal-organic framework material, 25 parts of modified activated carbon;

[0268] 2) Mix the raw materials weighed in step 1) and grind to obtain a heavy metal wastewater treatment agent precursor;

[0269] 3) Place the heavy metal wastewater treatment agent precursor obtained in step 2) in a silane coupling agent and leave it to stand at room temperature for 2 h to obtain the heavy metal wastewater treatment agent.

[0270] Comparative Example 11

[0271] A heavy metal wastewater treatment agent

[0272] 1. Preparation of titanium dioxide / graphitic carbon nitride composite photocatalyst

[0273] 1) Place melamine in a crucible and calcine it at 500 °C for 4 h to obtain graphitic carbon nitride;

[0274] 2) According to the mass-volume ratio of graphitic carbon nitride to ferric chloride solution of 1 g∶10 mL, place the graphitic carbon nitride obtained in step 1) into a ferric chloride solution with a concentration of 0.5 mol·L -1 , impregnate and modify it at 70 °C for 2 h, and then calcine it at 350 °C for 30 min under nitrogen protection to obtain iron-modified graphitic carbon nitride;

[0275] 3) According to the mass ratio of iron-modified graphitic carbon nitride to titanium dioxide of 2.5∶1, mix the iron-modified graphitic carbon nitride and titanium dioxide obtained in step 2) and grind them to obtain the titanium dioxide / graphitic carbon nitride composite photocatalyst;

[0276] 2. Preparation of metal-organic framework materials

[0277] 1) According to the molar ratio of nickel nitrate, iron nitrate and N,N-dimethylformamide of 1.5∶2∶10, place nickel nitrate and iron nitrate in N,N-dimethylformamide and ultrasonically disperse them for 30 min to obtain a metal mixed solution;

[0278] 2) According to the molar ratio of 2-methylimidazole dicarboxylic acid, 1,3-benzenedicarboxylic acid and N,N-dimethylformamide of 1∶1∶10, place 2-methylimidazole dicarboxylic acid and 1,3-benzenedicarboxylic acid in N,N-dimethylformamide and ultrasonically disperse them for 30 min to obtain an organic ligand solution;

[0279] 3) According to the volume ratio of the metal mixed solution to the organic ligand solution of 1∶2.5, control the dropping rate to 30 d·min -1 , drop the metal mixed solution obtained in step 1) into the organic ligand solution obtained in step 2), react at 140 °C for 2.5 h, then let it stand at room temperature for 7 h, and centrifuge to obtain the metal-organic framework material;

[0280] 3. Preparation of modified activated carbon

[0281] Place the activated carbon in a crucible and calcine it at 450 °C for 30 min to obtain the modified activated carbon;

[0282] 4. Preparation of heavy metal wastewater treatment agent

[0283] 1) Weigh the raw materials according to the following parts by mass:

[0284] 8 parts of titanium dioxide / graphite-phase carbon nitride composite photocatalyst, 15 parts of metal-organic framework material, and 25 parts of modified activated carbon;

[0285] 2) Mix the raw materials weighed in step 1), grind them, and then calcine at 350 °C for 15 min to obtain the heavy metal wastewater treatment agent.

[0286] Effect verification

[0287] Preparation of simulated heavy metal wastewater

[0288] Prepare simulated heavy metal wastewater according to the concentrations of total lead 10.0 mg / L, total chromium 5.0 mg / L, total cadmium 1.0 mg / L, and total mercury 0.5 mg / L;

[0289] According to the dosage of 5 g / L, add the heavy metal wastewater treatment agents prepared in Examples 1 to 3 and Comparative Examples 1 to 11 into the above-mentioned simulated heavy metal wastewater respectively. Under the condition of simulated natural light, let it stand for 2 h. Then, detect the water sample of the simulated heavy metal wastewater and calculate the heavy metal removal rate;

[0290] Heavy metal removal rate = [(initial heavy metal content - final heavy metal content) / initial heavy metal content] × 100%

[0291] The calculation results of the heavy metal removal rate are shown in Table 1;

[0292] Table 1 Heavy metal removal rate (%)

[0293]

[0294]

[0295] It can be seen from the data in Table 1 that the heavy metal wastewater treatment agent provided by the present invention can reach a removal rate of 99.96% for total lead, 99.97% for total chromium, 99.94% for total cadmium, and 99.96% for total mercury, and has good heavy metal removal effect and can be applied to the treatment of heavy metal wastewater.

[0296] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: still can modify the specific implementation manners of the present invention or make equivalent substitutions, and any modification or equivalent substitution without departing from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. A heavy metal wastewater treatment agent, characterized in that, It comprises the following raw materials in parts by mass: 5 - 10 parts of titanium dioxide / graphitic carbon nitride composite photocatalyst, 10 - 20 parts of metal-organic framework material, and 20 - 30 parts of modified activated carbon.

2. The heavy metal wastewater treatment agent according to claim 1, characterized in that The preparation method of the titanium dioxide / graphitic carbon nitride composite photocatalyst comprises the following steps: 1) Calcinate melamine to obtain graphitic carbon nitride; 2) Place the graphitic carbon nitride obtained in step 1) in a ferric chloride solution, impregnate and modify it, and then calcinate to obtain iron-modified graphitic carbon nitride; 3) Mix the iron-modified graphitic carbon nitride obtained in step 2) with titanium dioxide and grind to obtain the titanium dioxide / graphitic carbon nitride composite photocatalyst.

3. A heavy metal wastewater treatment agent according to claim 2, wherein in step 1), the calcination is carried out at 550 - 650 °C for 3 - 5 h; In step 2), the concentration of the iron chloride solution is 0.5 mol·L -1 ; the mass-volume ratio of the graphitic carbon nitride to the iron chloride solution is 1 g∶10 mL; the impregnation modification is carried out by impregnation modification at 60-80 °C for 1-3 h; the calcination is carried out at 300-400 °C for 20-40 min; in step 3), the mass ratio of the iron-modified graphitic carbon nitride to titanium dioxide is (2 - 3)∶1.

4. A heavy metal wastewater treatment agent according to claim 1, characterized in that, The preparation method of the metal-organic framework material comprises the following steps: 1) Place nickel nitrate and ferric nitrate in N,N-dimethylformamide and ultrasonically disperse to obtain a metal mixed solution; 2) Place 2-methylimidazole dicarboxylic acid and 1,3-benzenedicarboxylic acid in N,N-dimethylformamide and ultrasonically disperse to obtain an organic ligand solution; 3) Drop the metal mixed solution obtained in step 1) into the organic ligand solution obtained in step 2), react, let stand, and centrifuge to obtain the metal-organic framework material.

5. A heavy metal wastewater treatment agent according to claim 4, wherein in step 1), the molar ratio of nickel nitrate, ferric nitrate, and N,N-dimethylformamide is (1 - 2)∶(1 - 3)∶10; in step 2), the molar ratio of 2-methylimidazole dicarboxylic acid, 1,3-benzenedicarboxylic acid, and N,N-dimethylformamide is (0.5 - 1.5)∶(0.5 - 1.5)∶10; in step 3), the volume ratio of the metal mixed solution to the organic ligand solution is 1∶(2 - 3); the reaction is carried out at 120 - 160 °C for 2 - 3 h; the standing is carried out at room temperature for 6 - 8 h.

6. The heavy metal wastewater treatment agent according to claim 1, characterized in that, The preparation method of the modified activated carbon comprises the following steps: Calcinate the activated carbon to obtain the modified activated carbon.

7. A heavy metal wastewater treatment agent according to claim 6, characterized in that, The calcination is carried out at 400 - 500 °C for 20 - 40 min.

8. A preparation method of a heavy metal wastewater treatment agent as described in any one of claims 1 to 7, characterized in that, It comprises the following steps: 1) Mix the titanium dioxide / graphitic carbon nitride composite photocatalyst, metal-organic framework material, and modified activated carbon, grind, and then calcinate at 300 - 400 °C for 10 - 20 min to obtain a heavy metal wastewater treatment agent precursor; 2) Place the heavy metal wastewater treatment agent precursor obtained in step 1) in a silane coupling agent and let stand at room temperature for 1 - 3 h to obtain the heavy metal wastewater treatment agent.

9. Application of a heavy metal wastewater treatment agent according to any one of claims 1 - 7 in the treatment of heavy metal wastewater.

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