A heavy metal scavenging agent, its preparation method and application

Abstract

This invention relates to the field of wastewater treatment technology, specifically to a heavy metal scavenging agent, its preparation method, and its application. The heavy metal scavenging agent provided by this invention comprises a compound with the structure shown in formula (I) and ferrous sulfide, where R1 in formula (I) is a C1-C6 alkylene group. This invention utilizes a compound with strong chelating properties, consisting of a dual-active sulfur atom and an acrylamide group, to form a heavy metal scavenging agent with ferrous sulfide. The dual-active sulfur atom chelates the heavy metals, and the acrylamide group's excellent flocculation properties flocculate the chelated heavy metals. Simultaneously, ferrous sulfide is oxidized in water to form ferric hydroxide, which has a coagulating effect, further flocculating and settling the heavy metals, thus improving the settling rate and removal efficiency. Furthermore, the hydroxyl radicals generated by ferrous sulfide can degrade organic complexing ligands, reducing the complexing properties of the wastewater and preventing the complexing agent from continuously complexing with subsequent heavy metals.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a heavy metal scavenging agent, its preparation method, and its application. Background Technology

[0002] Heavy metals exist in water primarily in ionic and complexed forms. Ionic heavy metals can be effectively removed by alkali precipitation. However, in recent years, with the continuous advancement of surface treatment processes, the rapidly developing electroplating industry has led to the discharge of large amounts of wastewater containing heavy metals. Electroplating wastewater contains complex pollutants, including organic complexing agents such as ethylenediaminetetraacetic acid (EDTA), triethanolamine (TEA), tartaric acid, and citric acid. Heavy metal ions such as copper, nickel, and chromium in the wastewater accept electron pairs from the functional groups (such as carboxyl, amino, phenolic hydroxyl, and thiol groups) in the complexing agents, forming strong bonds and stable complexes. Due to the stable structure of complexed heavy metals, their removal is difficult. Current methods for treating complexed heavy metal wastewater include advanced oxidation, chemical precipitation, ion exchange, and chelation, but these methods are not ideal for heavy metal removal.

[0003] Existing technology provides a heavy metal scavenger that exhibits strong chelation with heavy metal ions, forming stable chelate precipitates and effectively separating heavy metals from the complex. However, the following problems still exist:

[0004] (1) For wastewater with strong complexing properties, excessive amounts of reagents are required to remove heavy metals from the wastewater. This inevitably leads to the problem of heavy metal scavenging agent residue, causing secondary pollution from the heavy metal scavenging agent and resulting in environmental problems such as increased total nitrogen and TOC in the effluent.

[0005] (2) Heavy metal capture agents remove complexed heavy metals by chelation precipitation. However, the complexing agent in the wastewater remains stable in the water, and the treated wastewater still has strong complexing properties, which will cause problems such as secondary complexing of heavy metals, thereby increasing the difficulty of operation and management.

[0006] (3) After the heavy metal chelating agent chelates the metal, the resulting flocs have poor settling properties and poor mud-water separation effect, resulting in a low heavy metal removal rate. Summary of the Invention

[0007] Therefore, the technical problem to be solved by the present invention is to overcome the defect of low removal rate of heavy metals by existing heavy metal scavenging agents, thereby providing a heavy metal scavenging agent, its preparation method and application.

[0008] Another technical problem to be solved by the present invention is to overcome the problem that the heavy metal capture agent in the prior art cannot degrade the organic complexing agent in the water, resulting in the complexing agent in the water still having a complexing effect on heavy metals, thus causing secondary complexing of heavy metals. Therefore, the present invention provides a heavy metal capture agent, its preparation method and application.

[0009] This invention also solves the problem of excessive dosage of heavy metal removal agents in the prior art, which leads to agent residue and secondary pollution. It provides a heavy metal scavenging agent, its preparation method and application, which reduces agent residue and secondary pollution.

[0010] On the one hand, the present invention provides a heavy metal scavenging agent comprising a compound with the structure shown in formula (I) and ferrous sulfide.

[0011]

[0012] Wherein, R1 is a C1-C6 alkylene group.

[0013] In some embodiments, R1 is at least one of methylene or ethylene.

[0014] For example, the structure shown in formula (I) is any one of the structures described in formula (II) or formula (III).

[0015]

[0016] On the other hand, the present invention provides a method for preparing the above-mentioned heavy metal scavenging agent, comprising the following steps,

[0017] In the presence of an inert gas, at a first temperature, an N-hydroxyalkylacrylamide solution, carbon disulfide, metal sulfide, and ferrous salt are mixed and reacted for a first time to obtain a heavy metal scavenging agent.

[0018] In this invention, the structural formula of N-hydroxyalkylacrylamide is shown in Formula (Ⅳ).

[0019]

[0020] In formula (Ⅳ), R2 is a C1-C6 alkylene group, preferably methylene or ethylene.

[0021] For example, taking N-hydroxymethylacrylamide as an example, the reaction formula of N-hydroxymethylacrylamide with carbon disulfide and ferrous salt is shown in formula (V).

[0022]

[0023] In some embodiments, the molar ratio of N-hydroxyalkylacrylamide, carbon disulfide, and ferrous salt in the N-hydroxyalkylacrylamide solution is 1:(2-3):(1-1.8).

[0024] The molar ratio of the metal sulfide to the ferrous salt is 1:(1-1.3).

[0025] In some embodiments, the ferrous salt includes at least one of ferrous sulfate, ferrous nitrate, and ferrous chloride.

[0026] In some embodiments, the metal sulfide includes at least one of sodium sulfide and potassium sulfide.

[0027] To ensure a complete reaction between carbon disulfide, ferrous salt, and N-hydroxyalkylacrylamide, carbon disulfide and ferrous salt were added dropwise to the N-hydroxyalkylacrylamide solution, respectively. The dropping rate of carbon disulfide was 200-600 μL / min, and the dropping rate of the ferrous salt solution was 800-1000 μL / min. The total dropping time for both carbon disulfide and ferrous salt was 1-3 h.

[0028] Furthermore, in order to avoid the volatilization of carbon disulfide and improve reaction efficiency, in this embodiment of the invention, the first temperature is less than or equal to 50°C, preferably 20-45°C; and the first time is 1-3 hours.

[0029] In some embodiments, the N-hydroxyalkylacrylamide solution is prepared by mixing an aqueous acrylamide solution, a polymerization inhibitor, and a hydroxyalkylating agent at a second temperature under alkaline conditions to obtain N-hydroxyalkylacrylamide.

[0030] In some embodiments, the concentration of the acrylamide aqueous solution is 50-100 g / L.

[0031] In some embodiments, the amount of the polymerization inhibitor added is 100-200 ppm of the mass of acrylamide.

[0032] In some embodiments, the molar ratio of the acrylamide to the hydroxyalkyl reagent is 1:(0.8-1.4).

[0033] In some embodiments, the polymerization inhibitor includes at least one of N-nitrosodiphenylamine, phenothiazine, hydroquinone, and p-hydroxyanisole.

[0034] Preferably, the polymerization inhibitor includes any two of N-nitrosodiphenylamine, phenothiazine, hydroquinone, and p-hydroxyanisole.

[0035] It should be noted that the polymerization inhibitor does not react with the raw materials in the reaction system, and its presence in the reaction system will not affect the formation of the heavy metal adsorbent.

[0036] In some embodiments, the hydroxyalkyl reagent includes C1-C6 hydroxyalkyl reagents.

[0037] Preferably, the hydroxyalkyl reagent is at least one of formaldehyde or ethylene oxide.

[0038] In some embodiments, the hydroxyalkyl reagent participates in the preparation of N-hydroxyalkylacrylamide in the form of a solution, wherein the hydroxyalkyl reagent in the aqueous solution is 30-40 wt%.

[0039] In some embodiments, the pH of the reaction solution in the method for preparing N-hydroxyalkylacrylamide is 9-11.

[0040] In some embodiments, the second temperature is 20-70°C. In order to avoid polycondensation of the hydroxyalkyl reagent, the second temperature is preferably 40-50°C in the embodiments of the present invention.

[0041] In some embodiments, an aqueous acrylamide solution, a polymerization inhibitor, and a hydroxyalkyl reagent are mixed under stirring at a rate of 300-500 rpm for 1-2 hours.

[0042] The heavy metal scavenging agent provided by this invention, or the heavy metal scavenging agent prepared by the above-mentioned method, can be applied to wastewater treatment. The heavy metal scavenging agent provided by this invention can chelate and precipitate insoluble flocs in wastewater. When colloids and other organic matter are present in the wastewater, the separation efficiency of organic matter in the wastewater can also be improved by applying an external magnetic field.

[0043] The technical solution of this invention has the following advantages:

[0044] 1. This invention provides a heavy metal scavenging agent comprising a compound with the structure shown in formula (I) and ferrous sulfide, wherein R1 in formula (I) is a C1-C6 alkylene group. This invention utilizes a compound with strong chelating properties, consisting of a dual-active sulfur atom and an acrylamide group, to form a heavy metal scavenging agent with ferrous sulfide. The dual-active sulfur atom chelates heavy metals, and the acrylamide group's excellent flocculation properties flocculate the chelated heavy metals. Simultaneously, the freshly prepared ferrous sulfide is oxidized in water to form ferric hydroxide, which has a coagulating effect, further flocculating and settling the heavy metals, thus improving the settling rate and removal efficiency. Furthermore, the hydroxyl radicals generated by ferrous sulfide in water degrade organic complexing ligands, reducing the complexing properties of the wastewater and preventing the complexing agent from continuously complexing with subsequent heavy metals. The heavy metal scavenging agent provided by this invention can reduce the content of complexed heavy metals from both the settling of heavy metals and the degradation of complexes.

[0045] 2. The heavy metal scavenging agent provided by this invention has a low molecular weight, high utilization rate, and low residue. It exhibits excellent effectiveness in removing complexed heavy metals. Compared to commonly available multi-branched polymer heavy metal scavenging agents, the heavy metal scavenging agent provided by this invention produces less sludge and has lower sludge disposal costs. Simultaneously, it can degrade the concentration of organic complexing agents and other organic matter in wastewater, reducing the complexing properties of the wastewater, simplifying downstream treatment, and facilitating on-site downstream operation and management.

[0046] 3. The present invention provides a method for preparing the above-mentioned heavy metal scavenging agent. In the presence of an inert gas, at a first temperature, N-hydroxyalkylacrylamide solution, carbon disulfide, metal sulfide, and ferrous salt are mixed and reacted for a first time to obtain the heavy metal scavenging agent. The preparation method provided by the present invention has simple process steps and a short synthesis time. In particular, since ferrous sulfide is easily oxidized, commercially available oxidized ferrous sulfide cannot participate in the removal of heavy metals from water. Therefore, this application utilizes metal sulfide and ferrous salt to formulate ferrous sulfide, and forms a compound with the structure shown in formula (Ⅰ) with N-hydroxyalkylacrylamide and carbon disulfide to form a scavenging agent for effective removal of heavy metals from water.

[0047] 4. This invention provides a method for preparing a heavy metal scavenging agent, wherein the N-hydroxyalkylacrylamide is prepared by mixing an aqueous solution of acrylamide, a polymerization inhibitor, and a hydroxyalkylating agent under alkaline conditions at a second temperature to obtain N-hydroxyalkylacrylamide. This invention uses acrylamide and a hydroxyalkylating agent as raw materials to prepare N-hydroxyalkylacrylamide. The N-hydroxyalkylacrylamide prepared on-site has high solubility and high reaction efficiency with carbon disulfide and ferrous salts.

[0048] 5. This invention provides a method for preparing a heavy metal scavenging agent, wherein the polymerization inhibitor comprises any two of N-nitrosodiphenylamine, phenothiazine, hydroquinone, and p-hydroxyanisole. This invention achieves better polymerization inhibition, reduces byproducts, and increases the yield of N-hydroxyalkylacrylamide by selecting two polymerization inhibitors.

[0049] 6. The heavy metal scavenging agent provided by the present invention, or the heavy metal scavenging agent prepared by the method of preparing heavy metal scavenging agent, can be applied to wastewater treatment. It has high heavy metal removal efficiency, not only without reagent residue, but also without causing an increase in total nitrogen or total organic carbon content, effectively avoiding the problem of secondary pollution. Attached Figure Description

[0050] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0051] Figure 1 This is the infrared spectrum of the organic compound in the heavy metal scavenger of Example 1 of the present invention. Detailed Implementation

[0052] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0053] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0054] Example 1

[0055] This embodiment provides a method for preparing a heavy metal scavenging agent, and the specific steps and parameters are as follows:

[0056] (1) Weigh 7g of acrylamide into a reactor and add 100mL of deionized water. Control the stirring speed at 400rpm. Add 100ppm of N-nitrosodiphenylamine (relative to the mass of acrylamide), 50ppm of phenothiazine (relative to the mass of acrylamide), and 10mL of formaldehyde solution with a formaldehyde concentration of 30wt%. Adjust the pH of the reaction to 10 with 10wt% sodium hydroxide. Control the temperature of the entire reaction system at 50℃ and react for 1.5h to prepare N-hydroxymethylacrylamide.

[0057] (2) Seal the reactor of step (1) and continuously introduce nitrogen gas into it for protection. Using a micro-syringe, add 15 mL of carbon disulfide, 55 mL of 50 wt% ferrous sulfate heptahydrate aqueous solution and 12 mL of 50% sodium sulfide at a flow rate of 800 μL / min to the reactor. Control the reaction temperature to be below 50℃. After adding the substances, continue stirring the reaction for 2 hours to obtain a light green liquid, which is the heavy metal scavenging agent.

[0058] The heavy metal scavenging agent prepared in this embodiment was subjected to infrared spectroscopy detection, see [reference needed]. Figure 1 Among them, 1900-1650cm -1 Characteristic peaks appear within the range; -C=O- is present on the surface; 1690-1500 cm⁻¹ -1 Characteristic peaks appear within the range; -C=C- exists on the surface; 1100-1000cm -1 Characteristic peaks appear within the range indicating the presence of amide groups and -CN-, -C=S- on the surface; 700-600 cm⁻¹ -1 Characteristic peaks appear within the range, and -CS- is present on the surface.

[0059] Example 2

[0060] This embodiment provides a method for preparing a heavy metal scavenging agent, and the specific steps and parameters are as follows:

[0061] (1) Weigh 7g of acrylamide into a reactor and add 100mL of deionized water. Control the stirring speed at 500rpm. Add 100ppm of hydroquinone (relative to the mass of acrylamide), 100ppm of phenothiazine (relative to the mass of acrylamide), and 10mL of formaldehyde solution with a formaldehyde concentration of 37wt%. Adjust the pH of the reaction to 11 with 10wt% sodium hydroxide. Control the temperature of the entire reaction system at 20℃ to prepare N-hydroxymethylacrylamide.

[0062] (2) Seal the reactor from step (1) and continuously purge it with nitrogen for protection. Using a microsyringe, add 15 mL of carbon disulfide dropwise into the reactor at a flow rate of 200 μL / min. Add 100 mL of a 50% ferrous sulfate heptahydrate aqueous solution and 22 mL of a 50% sodium sulfide solution dropwise into the reactor at a flow rate of 1500 μL / min, controlling the reaction temperature below 50°C. After the addition is complete, continue stirring the reaction for 1 hour to obtain a light green liquid, which is the heavy metal scavenging agent.

[0063] Example 3

[0064] This embodiment provides a method for preparing a heavy metal scavenging agent, and the specific steps and parameters are as follows:

[0065] (1) Weigh 7g of acrylamide into a reactor and add 100mL of deionized water. Control the stirring speed at 300rpm. Add 50ppm of p-hydroxyanisole (relative to the mass of acrylamide), 50ppm of N-nitrosodiphenylamine (relative to the mass of acrylamide), and 10mL of formaldehyde solution with a formaldehyde concentration of 40wt%. Adjust the pH of the reaction to 9 with 10wt% sodium hydroxide. Control the temperature of the entire reaction system at 70℃ and react for 1h to prepare N-hydroxymethylacrylamide.

[0066] (2) Seal the reactor from step (1) and continuously purge it with nitrogen gas for protection. Use a microsyringe to add carbon disulfide dropwise into the reactor at a flow rate of 200 μL / min. Add 36 mL of 50% ferrous nitrate aqueous solution and 50% potassium sulfide solution dropwise into the reactor at a flow rate of 1000 μL / min. The molar ratio of N-hydroxymethylacrylamide, carbon disulfide and ferrous nitrate is 1:3:1, and the molar ratio of potassium sulfide and ferrous nitrate is 1:1.3. Control the reaction temperature to be below 50℃. After adding the solutions, stir the reaction for 3 hours to obtain a light green liquid, which is the heavy metal scavenging agent.

[0067] Example 4

[0068] This embodiment provides a method for preparing a heavy metal scavenging agent, and the specific steps and parameters are as follows:

[0069] (1) Weigh 7g of acrylamide into a reactor and add 100mL of deionized water. Control the stirring speed at 400rpm. Add 100ppm of N-nitrosodiphenylamine (relative to the mass of acrylamide), 50ppm of phenothiazine (relative to the mass of acrylamide), and 14mL of formaldehyde solution with a formaldehyde concentration of 35wt%. Adjust the pH of the reaction to 10 with 10wt% sodium hydroxide. Control the temperature of the entire reaction system at 50℃ and react for 1.5h to prepare N-hydroxymethylacrylamide.

[0070] (2) Seal the reactor from step (1) and continuously purge it with nitrogen gas for protection. Use a microsyringe to add carbon disulfide dropwise into the reactor at a flow rate of 600 μL / min. Add a 50% ferrous chloride aqueous solution and a 50% sodium sulfide solution dropwise into the reactor at a flow rate of 900 μL / min. The molar ratio of N-hydroxymethylacrylamide, carbon disulfide and ferrous chloride is 1:3:1, and the molar ratio of sodium sulfide and ferrous chloride is 1:1. Control the reaction temperature below 50℃. After the addition, stir the reaction for 3 hours to obtain a light green liquid, which is the heavy metal scavenging agent.

[0071] Example 5

[0072] This embodiment provides a method for preparing a heavy metal scavenger. The specific steps and parameters are the same as in Example 1, except that an equal mass of phenothiazine is used instead of N-nitrosodiphenylamine, that is, the polymerization inhibitor is 150 ppm phenothiazine (compared to the mass of acrylamide).

[0073] Example 6

[0074] This embodiment provides a method for preparing a heavy metal scavenger. The specific steps and parameters are the same as in Example 1. The difference is that the temperature of the entire reaction system is controlled at 40°C in step (1).

[0075] Example 7

[0076] This embodiment provides a method for preparing a heavy metal scavenger. The specific steps and parameters are the same as in Example 1. The difference is that the temperature of the entire reaction system is controlled at 60°C in step (1).

[0077] Example 8

[0078] This embodiment provides a method for preparing a heavy metal scavenger. The specific steps and parameters are the same as in Example 1. The difference is that in step (2), the reaction temperature is controlled at 20°C.

[0079] Example 9

[0080] This embodiment provides a method for preparing a heavy metal scavenger. The specific steps and parameters are the same as in Example 1. The difference is that in step (2), the reaction temperature is controlled at 45°C.

[0081] Example 10

[0082] This embodiment provides a method for preparing a heavy metal scavenging agent. The specific steps and parameters are the same as in Example 1, except that an equal volume of 30wt% ethylene oxide aqueous solution is used to replace the formaldehyde solution in step (1).

[0083] Example 11

[0084] This embodiment provides a method for preparing a heavy metal scavenger. The specific steps and parameters are the same as in Example 1. The difference is that an equal volume of commercially available N-hydroxymethylacryl aqueous solution (concentration of 1 mol / L) is used to replace the N-hydroxymethylacryl freshly prepared in the reactor in step (2).

[0085] Comparative Example 1

[0086] This comparative example provides a method for preparing a heavy metal scavenger. The specific steps and parameters are the same as in Example 1, except that step (1) is omitted and an equimolar amount of acrylamide is used to replace N-hydroxymethylacrylamide in step (2).

[0087] Comparative Example 2

[0088] This comparative example provides a method for preparing a heavy metal scavenging agent. The specific steps and parameters are the same as in Example 1. The difference is that step (2) does not contain ferrous sulfate. That is, (2) the reactor of step (1) is sealed and nitrogen gas is continuously introduced into it for protection. 15 mL of carbon disulfide is added to the reactor at a flow rate of 200 μL / min using a microsyringe. 12 mL of sodium sulfide with a mass fraction of 50% is added to the reactor at a flow rate of 800 μL / min. The reaction temperature is controlled within 50°C. After the addition, the reaction is stirred for 2 hours to obtain a light green liquid, which is the heavy metal scavenging agent.

[0089] Comparative Example 3

[0090] This comparative example provides a method for preparing a heavy metal scavenger. The specific steps and parameters are the same as in Example 1. The difference is that step (2) does not contain carbon disulfide. That is, (2) the reactor of step (1) is sealed and nitrogen gas is continuously introduced into it for protection. A micro-syringe is used to add 55 mL of 50 wt% ferrous sulfate heptahydrate aqueous solution and 12 mL of 50% sodium sulfide at a flow rate of 800 μL / min to the reactor. The reaction temperature is controlled to be below 50°C. After the addition, the reaction is stirred for 2 hours to obtain a light green liquid, which is the heavy metal scavenger.

[0091] Experimental Example

[0092] Taking the zinc-nickel alloy wastewater from an electroplating industrial park in Ningbo as the treatment target, the wastewater contains Zn 2+ Ni 2+ The concentrations were 453 mg / L and 63.21 mg / L, respectively, with a total nitrogen concentration of 1392 mg / L and a TOC concentration of 3240 mg / L.

[0093] Take 100 mL of wastewater sample, add 0.2 mL of heavy metal scavenging agent, stir at 500 rpm for 30 min, filter with filter paper, collect the filtrate, acidify with nitric acid until the water sample is acidic and clear, and detect Zn in the water sample by ICP-OES. 2+ Ni 2+ The concentration was determined by alkaline potassium persulfate ultraviolet spectrophotometry (HJ 636-2012) for total nitrogen (TN) in the water sample, and the total organic carbon (TOC) content was detected by a total organic carbon analyzer. The heavy metal scavenging agents were the metal scavenging agents prepared in Examples 1-11 and Comparative Examples 1-3, respectively.

[0094] Table 1 Wastewater Treatment Results

[0095]

[0096] As shown in Table 1, compared with Comparative Examples 1-3, the heavy metal scavenging agent provided in this embodiment of the invention can effectively reduce the concentration of heavy metals in wastewater, has a good heavy metal removal effect, and does not increase the total nitrogen and total organic carbon content in wastewater.

[0097] The general method for detecting the content of complexed substances in water samples involves taking a treated water sample, adjusting the pH to 4, adding sufficient Ni ions to achieve a Ni ion concentration of 1 g / L, stirring continuously for 1 hour, adjusting the pH to 10.5 with lime, and then detecting the Ni ion content to characterize the content of complexed substances. However, as shown in Table 1, the heavy metal scavenging agent provided by this invention can significantly reduce the Ni ion content in water samples, further demonstrating that the heavy metal scavenging agent provided by this invention can reduce the content of complexed substances in water samples.

[0098] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A heavy metal capturing agent, characterized in that, Including compounds having the structure shown in formula (II) and ferrous sulfide, The molar ratio of the compound having the structure shown in formula (II) to ferrous sulfide is 1:1-1.8; The preparation method of the heavy metal scavenging agent includes the following steps: in the presence of an inert gas, at a first temperature, N-hydroxymethylacrylamide, carbon disulfide, metal sulfide and ferrous salt are mixed and reacted for a first time to obtain the heavy metal scavenging agent. The reaction formula for N-hydroxymethylacrylamide with carbon disulfide and ferrous salt is shown in formula (V). The method for preparing N-hydroxymethylacrylamide includes mixing an aqueous solution of acrylamide, a polymerization inhibitor, and a formaldehyde solution at a second temperature under alkaline conditions to obtain N-hydroxymethylacrylamide. The polymerization inhibitor includes any two of N-nitrosodiphenylamine, phenothiazine, hydroquinone, and p-hydroxyanisole.

2. The heavy metal capturing agent according to claim 1, characterized in that, The molar ratio of N-hydroxymethylacrylamide, carbon disulfide, and ferrous salt is 1:2-3:1-1.

8. The molar ratio of the metal sulfide to the ferrous salt is 1:1-1.

3.

3. The heavy metal capturing agent according to claim 1, characterized in that, The ferrous salt includes at least one of ferrous sulfate, ferrous nitrate, and ferrous chloride; and / or, The metal sulfide includes at least one of sodium sulfide and potassium sulfide; and / or, The first temperature is 20-45℃; and / or, The first time is 1-3 hours.

4. The heavy metal capturing agent according to claim 1, characterized in that, The concentration of the acrylamide aqueous solution is 50-100 g / L; and / or, The amount of the polymerization inhibitor added is 100-200 ppm based on the mass of acrylamide, and the molar ratio of acrylamide to formaldehyde is 1:0.8-1.

4.

5. The heavy metal scavenging agent according to claim 4, characterized in that, Formaldehyde solution can be replaced with an aqueous solution of ethylene oxide; and / or, The second temperature is 40-50℃; and / or, While stirring, an aqueous solution of acrylamide, a polymerization inhibitor, and a formaldehyde solution are mixed at a stirring rate of 300-500 rpm for 1-2 hours.

6. The application of the heavy metal capturing agent according to claim 1 in wastewater treatment.

7. The application according to claim 6, characterized in that, The ratio of the heavy metal capturing agent to wastewater is 1-3:1, in mL:L.

Images