A nano-detection material for detecting heavy metal ions in industrial sewage and a preparation method thereof

Abstract

The present invention discloses a nano-detection material for detecting heavy metal ions in industrial sewage and a preparation method thereof in the technical field of detection materials. In the present invention, the surface of gold nanoparticles is functionally modified, a modified cellulose modified by imidazole groups is introduced onto the surface of the gold nanoparticles, and disulfide bonds are introduced into the modified cellulose, so as to stabilize the gold nanoparticles through the affinity between sulfur and gold, improve the stability of the gold nanoparticles in different environments, and ensure the detection stability and sensitivity in different environments.

Description

Technical Field

[0001] The present invention belongs to the technical field of detection materials, and specifically refers to a nano-detection material for detecting heavy metal ions in industrial sewage and a preparation method thereof. Background Art

[0002] Heavy metal pollution in industrial sewage refers to the waste water discharged during industrial production containing excessive heavy metal elements such as lead (Pb), cadmium (Cd), mercury (Hg), chromium (Cr), copper (Cu), etc. Heavy metals cannot be naturally degraded and will accumulate in water bodies, soil and organisms, causing long-term ecological environmental pollution and serious health hazards; the sources of industrial sewage are extensive. For example, in the metallurgical industry, during the process of smelting metals, waste water and waste gas containing heavy metals such as lead, cadmium, chromium, copper, and zinc are often generated. These heavy metals will not only be discharged during the smelting process, but may also be released during the corrosion of production equipment, furnaces and other equipment; in the electroplating industry, heavy metals used in the electroplating process, such as chromium, nickel, zinc, etc., will cause serious pollution after being discharged into the waste water; in the chemical industry, heavy metals used and discharged in the production of chemical fertilizers, pesticides, dyes, etc.; in the battery manufacturing industry, heavy metals such as lead, cadmium, and mercury will be discharged during the production of nickel-cadmium batteries, lithium-ion batteries, etc.; in the treatment of electronic waste: improper treatment of electronic waste may lead to the release of heavy metals such as lead, mercury, and copper; in the leather and textile industries: during the leather tanning and dyeing processes, metal ions such as chromium, copper, and zinc may be discharged; heavy metal ions have biological toxicity and cumulative effects, directly affecting the water ecosystem and human health: after heavy metal ions enter the water body, they are gradually transmitted through the food chain of aquatic plants and animals, ultimately leading to ecological imbalance. They can interfere with the normal physiological activities of organisms, such as causing difficulties in the reproduction of aquatic organisms, growth stagnation or even death; through the food chain or directly drinking contaminated water, heavy metals enter the human body and accumulate in the body, causing chronic poisoning. For example, lead will damage the nervous system, mercury will cause renal failure, cadmium will cause bone softening and kidney diseases, and long-term exposure may trigger serious diseases such as cancer.

[0003] Although the existing technologies can detect and treat heavy metal ions in industrial sewage, they still face many challenges: low-concentration detection: some heavy metal ions still have biological toxicity at extremely low concentrations, so the sensitivity of detection technologies needs to be further improved; complex pollution environment: the composition of industrial sewage is complex and may contain multiple heavy metals and organic pollutants, which makes detection and treatment more difficult. Summary of the Invention

[0004] In view of the above situation, in order to overcome the defects of the prior art, the present invention provides a nano detection material for detecting heavy metal ions in industrial wastewater and a preparation method thereof. The present invention functionalizes the surface of gold nanoparticles, introduces modified cellulose modified by imidazole groups into the surface of the gold nanoparticles, and introduces disulfide bonds into the modified cellulose, thereby stabilizing the gold nanoparticles through the affinity of sulfur element and gold, improving the stability of the gold nanoparticles in different environments, and ensuring the detection stability and sensitivity in different environments.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows: The present invention proposes a method for preparing a nanometer detection material for heavy metal ion detection in industrial wastewater, which specifically comprises the following steps:

[0006] S1. Disperse cellulose in a 50 vol% methanol aqueous solution, adjust the pH to 4-4.5, place in a nitrogen environment, add AIBN and mix well to obtain a pretreated cellulose solution;

[0007] S2, dissolving N-hydroxyethyl acrylamide in DMF, adding imidazole-2-carboxylic acid methyl ester, mixing at a speed of 150-180 rpm, adding p-toluenesulfonic acid, raising the reaction temperature to 120-140° C., and performing reflux reaction for 5-7 hours. After the reaction is completed, adding deionized water for washing until the reaction system is neutral, distilling under reduced pressure, and freeze-drying to obtain imidazolyl acrylamide;

[0008] S3, adding the imidazolyl acrylamide solution to the pretreated cellulose solution prepared in step S2, mixing evenly, adding N,N'-bis(acryloyl)cystamine, placing under nitrogen conditions, raising the reaction temperature to 60-80°C, stirring at a speed of 200-250 rpm, reacting for 4-6 hours, washing with anhydrous ethanol, and vacuum drying to obtain modified cellulose;

[0009] S4, dissolving the modified cellulose prepared in step S3 in DMAC, preparing a HAuCl4 solution and dropping it into the reaction system, stirring and reacting for 30-40 minutes, adding a NaBH4 aqueous solution to ice water, continuing to stir and react for 15-25 minutes, washing with deionized water, and vacuum drying to obtain a nano detection material;

[0010] Preferably, in step S1, the mass fraction of cellulose in the methanol aqueous solution is 3%-5%;

[0011] Preferably, in step S1, the mass ratio between AIBN and cellulose is 1:8-10;

[0012] Preferably, in step S2, the mass concentration of N-hydroxyethyl acrylamide in dichloromethane is 40-50 g / L;

[0013] Preferably, in step S2, the mass ratio between N - hydroxyethyl acrylamide and methyl imidazole - 2 - carboxylate is 1:1.1 - 1.2;

[0014] Preferably, in step S2, the added mass of p - toluenesulfonic acid is 10% - 12% of the mass of N - hydroxyethyl acrylamide;

[0015] Preferably, in step S3, the imidazolyl acrylamide solution is a solution in which imidazolyl acrylamide is dissolved in an aqueous methanol solution, wherein the mass concentration of imidazolyl acrylamide is 40 - 80 g / L, and the volume fraction of methanol in the aqueous methanol solution is 60% - 80%;

[0016] Preferably, in step S3, the mass ratio between imidazolyl acrylamide and cellulose is 1:1.25 - 1.5;

[0017] Preferably, in step S3, the added mass of N,N’ - bis(acryloyl)cystamine is 10% - 20% of the mass of imidazolyl acrylamide;

[0018] Preferably, in step S4, the mass fraction of the modified cellulose in DMAC is 1% - 4%;

[0019] Preferably, in step S4, in the HAuCl4 solution, the mass concentration of HAuCl4 in DMAC is 4 - 5 g / L; the added mass of HAuCl4 is 3.6% - 5% of the mass of the modified cellulose;

[0020] Preferably, in step S4, the mass concentration of NaBH4 in the NaBH4 solution is 10 - 12 g / L; the added mass of NaBH4 is 4% - 6% of the mass of the modified cellulose.

[0021] The present invention also provides a nano - detection material for detecting heavy metal ions in industrial sewage prepared according to the above - mentioned preparation method.

[0022] The beneficial effects achieved by the present invention are as follows:

[0023] The present invention provides a nano-detection material for detecting heavy metal ions in industrial sewage and a preparation method thereof. By functionalizing the surface of gold nanoparticles, the present invention introduces modified cellulose modified by imidazole groups onto the surface of gold nanoparticles, and introduces disulfide bonds into the modified cellulose, thereby stabilizing the gold nanoparticles through the affinity between sulfur and gold, improving the stability of the gold nanoparticles in different environments, and ensuring the detection stability and sensitivity in different environments; the present invention grafts imidazole groups onto acrylamide, uses bisacrylamide with disulfide bonds as a crosslinking agent to modify cellulose; through the affinity between sulfur elements in the disulfide bonds and gold ions, the binding performance of S and Au is improved, and gold nanoparticles are in-situ synthesized. After the reaction is completed, it is washed with deionized water until neutral, and a nano-detection material for heavy metal ions is prepared; by introducing imidazole groups and S-S bonds onto the gold nanoparticles, under acidic conditions, the influence of protonation on the surface properties of the gold nanoparticles can be avoided through the imidazole groups, and the detection performance of the gold nanoparticles can be maintained. Under alkaline conditions, the S exposed by the cleavage of the S-S bond - avoids the excessive aggregation of cations on the gold nanoparticles, which affects the detection performance, thereby improving the stability of the nano-detection material in various environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The UV-vis images of the nano-detection materials prepared in Example 1 for different concentrations of Hg 2+ ;

[0025] Figure 2 The selectivity result diagram of the nano-detection material prepared in Example 1 of the present invention for heavy metal ions;

[0026] Figure 3 The sensitivity result diagram of the nano-detection materials prepared in Examples 1-3 and Comparative Examples 1-2 of the present invention;

[0027] Figure 4 The stability result diagram of the nano-detection materials prepared in Examples 1-3 and Comparative Examples 1-2 of the present invention at different pH values.

[0028] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention, and do not constitute a limitation to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

[0030] Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to the described content can be applied to the present invention. The preferred implementation methods and materials described in the text are for illustrative purposes only and do not limit the content of this application.

[0031] In the experimental methods of the following examples, unless otherwise specified, they are all conventional methods; the test materials and test strains used in the following examples, unless otherwise specified, are all purchased from commercial channels.

[0032] Example 1

[0033] This example provides a preparation method for a nano-detection material for detecting heavy metal ions in industrial sewage, specifically including the following steps:

[0034] S1. Accurately weigh 5 g of cellulose and place it in a flask. Gradually add 100 mL of 50 vol% methanol aqueous solution, and stir well at a speed of 150 rpm until the cellulose is evenly dispersed. Adjust the pH to 4.5. Accurately weigh 0.5 g of AIBN, introduce nitrogen to replace the oxygen in the reaction system, and continue to stir until the reaction system is uniform to obtain a pretreated cellulose solution.

[0035] S2. Accurately weigh 3 g of N-hydroxyethylacrylamide and place it in a new flask. Add 75 mL of DMF solvent, and stir on a magnetic stirrer at a speed of 120 rpm. After N-hydroxyethylacrylamide is completely dissolved, add 3.3 g of methyl imidazole-2-carboxylate to the reaction system, adjust the rotation speed to 180 rpm for thorough mixing, add 0.3 g of p-toluenesulfonic acid, raise the reaction temperature to 140 °C, and carry out a reflux reaction for 5 h. After the reaction system cools to room temperature, wash the reaction system with deionized water until neutral, carry out vacuum distillation to remove the reaction solvent, and then freeze-dry to obtain imidazolyl acrylamide.

[0036] S3. Accurately weigh 4 g of the imidazolyl acrylamide prepared in step S2 and dissolve it in 50 mL of 80 vol% methanol aqueous solution. Add it to the pretreated cellulose solution prepared in step S2, and stir well on a magnetic stirrer at a speed of 150 rpm. After mixing evenly, add 0.4 g of N,N'-bis(acryloyl)cystamine, introduce nitrogen into the reaction system, continue to mix, raise the reaction temperature to 70 °C, set the stirring speed to 250 rpm, and react for 5 h. After the reaction system cools to room temperature, add 500 mL of absolute ethanol for washing, centrifuge at 5000 rpm for 5 min, remove the supernatant, and then wash the lower-layer reactant with absolute ethanol and deionized water alternately three times. After vacuum drying at 30 °C for 15 h, modified cellulose is obtained.

[0037] S4. Accurately weigh 1.0 g of the modified cellulose prepared in step S3 and place it in a flask. Add 100 mL of DMAC and mix at a speed of 200 rpm to fully disperse the modified cellulose in DMAC. Accurately weigh 4.0 g of HAuCl4 and dissolve it in 10 mL of deionized water. After mixing evenly, take 1 mL of it and dilute it with 10 mL of DMAC. After the solution is mixed evenly, take 9 mL and add it dropwise to the reaction system at a speed of 1 mL / min. Stir at a speed of 200 rpm for 40 min. Transfer the reaction system to an ice-water bath. Accurately weigh 0.1 g of NaBH4 and place it in a volumetric flask and make up the volume with 10 mL of deionized water. After the reaction system is cooled, add 4 mL of NaBH4 solution dropwise to the reaction system at a speed of 0.5 mL / min. After the addition is complete, continue to stir the reaction for 20 min. After the reaction is completed, wash with deionized water until there is no chloride ion in the product, and place it at 50°C and vacuum dry for 12 h to obtain a nano detection material.

[0038] This embodiment also provides a nanometer detection material for detecting heavy metal ions in industrial wastewater, which is prepared according to the above preparation method.

[0039] Example 2

[0040] This embodiment provides a method for preparing a nanometer detection material for detecting heavy metal ions in industrial wastewater, which specifically includes the following steps:

[0041] S1. Accurately weigh 3 g of cellulose and place it in a flask. Add 100 mL of 50 vol% methanol aqueous solution in portions, stir thoroughly at 150 rpm until the cellulose is evenly dispersed, adjust the pH to 4, accurately weigh 0.35 g of AIBN, introduce nitrogen to replace the oxygen in the reaction system, and continue stirring until the reaction system is uniform to obtain a pretreated cellulose solution;

[0042] S2. Accurately weigh 5 g of N-hydroxyethyl acrylamide and place it in a new flask, add 100 mL of DMF solvent, place it on a magnetic stirrer and stir at a speed of 120 rpm. After the N-hydroxyethyl acrylamide is completely dissolved, add 6 g of imidazole-2-carboxylic acid methyl ester to the reaction system, adjust the speed to 150 rpm for thorough mixing, add 0.6 g of p-toluenesulfonic acid, increase the reaction temperature to 120° C., perform reflux reaction for 7 hours, wait for the reaction system to cool to room temperature, wash the reaction system with deionized water until it is neutral, perform vacuum distillation, remove the reaction solvent, and then freeze-dry to obtain imidazolyl acrylamide;

[0043] S3. Weigh accurately 2 g of the imidazolylacrylamide prepared in step S2 and dissolve it in 50 mL of a 70 vol% methanol aqueous solution. Add it to the pretreated cellulose solution prepared in step S2, place it on a magnetic stirrer, and stir thoroughly at a speed of 150 rpm. After mixing evenly, add 0.3 g of N,N'-bis(acryloyl)cystamine. Pass nitrogen into the reaction system, continue mixing, raise the reaction temperature to 80 °C, set the stirring speed to 200 rpm, and react for 6 h. After the reaction system cools to room temperature, add 500 mL of absolute ethanol for washing. Centrifuge at 5000 rpm for 5 min, remove the supernatant, and then wash the lower-layer reactant with absolute ethanol and deionized water alternately three times. After vacuum drying at 30 °C for 15 h, modified cellulose is obtained.

[0044] S4. Weigh accurately 1.0 g of the modified cellulose prepared in step S3 and place it in a flask. Add 25 mL of DMAC and mix at a speed of 200 rpm to disperse the modified cellulose thoroughly in DMAC. Weigh accurately 5.0 g of HAuCl4 and dissolve it in 10 mL of deionized water. After mixing evenly, take 1 mL of it and dilute it with 10 mL of DMAC. After the solution is mixed evenly, add it dropwise to the reaction system at a rate of 1 mL / min and stir at a speed of 200 rpm for 40 min. Transfer the reaction system to an ice-water bath. Weigh accurately 0.1 g of NaBH4, place it in a volumetric flask, and make up the volume to 10 mL with deionized water. After the reaction system cools, add 6 mL of NaBH4 solution dropwise to the reaction system at a speed of 0.5 mL / min. After the addition is complete, continue to stir and react for 15 min. After the reaction is completed, wash with deionized water until there is no chloride ion in the product, and vacuum dry at 50 °C for 12 h to obtain the nano-detection material.

[0045] This example also provides a nano-detection material for detecting heavy metal ions in industrial sewage prepared according to the above preparation method.

[0046] Example 3

[0047] This example provides a preparation method of a nano-detection material for detecting heavy metal ions in industrial sewage, which specifically includes the following steps:

[0048] S1. Weigh accurately 4 g of cellulose and place it in a flask. Add 100 mL of a 50 vol% methanol aqueous solution in portions, and stir thoroughly at a speed of 150 rpm until the cellulose is evenly dispersed. Adjust the pH to 4.3. Weigh accurately 0.45 g of AIBN, pass nitrogen to replace the oxygen in the reaction system, and continue to stir until the reaction system is uniform to obtain a pretreated cellulose solution.

[0049] S2. Accurately weigh 4.5 g of N - hydroxyethyl acrylamide and place it in a new flask. Add 100 mL of DMF solvent, place it on a magnetic stirrer and stir at a speed of 120 rpm. After N - hydroxyethyl acrylamide is completely dissolved, add 5 g of methyl imidazole - 2 - carboxylate to the reaction system, adjust the rotation speed to 150 rpm for thorough mixing, add 0.5 g of p - toluenesulfonic acid, raise the reaction temperature to 130 °C, carry out reflux reaction for 6 h. After the reaction system cools to room temperature, wash the reaction system with deionized water until it is neutral, carry out vacuum distillation, remove the reaction solvent, and then carry out freeze - drying to obtain imidazolyl acrylamide;

[0050] S3. Accurately weigh 3 g of the imidazolyl acrylamide prepared in step S2 and dissolve it in 50 mL of 60 vol% methanol - aqueous solution. Add it to the pretreated cellulose solution prepared in step S2, place it on a magnetic stirrer and stir thoroughly at a speed of 150 rpm. After mixing evenly, add 0.45 g of N,N’ - bis(acryloyl)cystamine, pass nitrogen into the reaction system, continuously mix, raise the reaction temperature to 60 °C, set the stirring speed to 220 rpm, react for 4 h. After the reaction system cools to room temperature, add 500 mL of absolute ethanol for washing, centrifuge at 5000 rpm for 5 min, remove the supernatant, and then wash the lower - layer reactant with absolute ethanol and deionized water successively and repeatedly three times. After vacuum drying at 30 °C for 15 h, obtain modified cellulose;

[0051] S4. Accurately weigh 1.0 g of the modified cellulose prepared in step S3 and place it in a flask. Add 50 mL of DMAC, mix at a speed of 200 rpm, and disperse the modified cellulose thoroughly in DMAC. Accurately weigh 4.0 g of HAuCl4 and dissolve it in 10 mL of deionized water. After mixing evenly, take 1 mL of it and dilute it with 10 mL of DMAC. After the solution is mixed evenly, add it drop - by - drop to the reaction system at a rate of 1 mL / min, stir at a speed of 200 rpm for 35 min. Transfer the reaction system to an ice - water bath condition. Accurately weigh 0.1 g of NaBH4 and make up the volume to 10 mL with deionized water in a volumetric flask. After the reaction system cools, add 5 mL of NaBH4 solution to the reaction system drop - by - drop at a speed of 0.5 mL / min. After dropping, continue to stir and react for 25 min. After the reaction is completed, wash with deionized water until there is no chloride ion in the product, and carry out vacuum drying at 50 °C for 12 h to obtain the nano - detection material.

[0052] This example also provides a nano - detection material for detecting heavy metal ions in industrial sewage prepared according to the above - mentioned preparation method.

[0053] Comparative Example 1

[0054] This comparative example provides a heavy metal ion nano-detection material and a preparation method thereof. The difference from Example 1 is only that step S2 is not included in the preparation method. In step S3, N-hydroxyethyl acrylamide is used to replace the imidazolyl acrylamide in the same mass ratio, and the components and component contents are the same as those in Example 1.

[0055] Comparative Example 2

[0056] This comparative example provides a heavy metal ion nano-detection material and a preparation method thereof. The difference from Example 1 is only that in step S3 of the preparation method, N,N'-vinyl bisacrylamide is used to replace N,N'-bis(acryloyl)cystamine in the same mass ratio, and the components and component contents are the same as those in Example 1.

[0057] Experimental Example 1

[0058] In this experimental example, the detection selectivity of the heavy metal ion nano-detection material prepared in Example 1 was measured. A 1×10 -5 mol / L heavy metal ion solution was prepared, including Na + , K + , Mg 2+ , Sr 2+ , Al 3+ , Mn 2+ , Co 2+ , Pb 2+ , Fe 2+ , Fe 3+ , Cr 3+ . An aqueous solution of the nano-detection material was prepared at 3 g / L. 3 mL of the aqueous solution of the nano-detection material, 1 mL of a 1×10 -5 mol / L Hg 2+ solution, and 1 mL of a 1×10 -5 mol / L solution of other heavy metal ions were added to a centrifuge tube and measured on a UV-visible spectrophotometer. Figure 1 The UV-vis image of the nano-detection material prepared in Example 1 for different concentrations of Hg 2+ is shown in the figure. When the concentration of Hg 2+ is 1.0×10 -6 M, a new absorption peak appears at 608 nm for the nano-ions. When the concentration of Hg 2+ increases to 4.0×10 -6 M, the absorption peak at 608 nm redshifts to 650 nm. Since the increase in the concentration of Hg 2+ causes a greater degree of aggregation of the nano-ions in the nano-detection material, resulting in the redshift of the absorption peak; in this example, the ratio of the absorbance at 650 nm to the absorbance at 520 nm was used as the standard for evaluating the heavy metal ion concentration. By establishing A650 / A 520 The linear relationship between the value and the concentration of Hg 2+ is used to quantitatively analyze Hg 2+ ; Figure 2 This is the selectivity result diagram of the nano-detection material prepared in Example 1 of the present invention for heavy metal ions. As shown in the figure, the nano-detection material prepared in Example 1 of the present invention has high selectivity for Hg 2+ ;

[0059] Experimental Example 2

[0060] In this experimental example, the sensitivity of the nano-detection materials prepared in Examples 1-3 and Comparative Examples 1-2 was measured. Hg 2+ solutions were prepared, and the concentrations of the Hg 2+ solutions were set to 5.0×10 -7 mol / L, 1.0×10 -6 mol / L, 2.0×10 -6 mol / L, 4.0×10 -6 mol / L, 8.0×10 -6 mol / L, 1.0×10 -5 mol / L. The nano-detection materials prepared in Examples 1-3 and Comparative Examples 1-2 were added at 2 g / L, and the mixture was shaken on a shaker at a speed of 150 rpm for 10 min. The concentration of Hg 2+ was measured using a UV-visible spectrophotometer;

[0061] Figure 3 This is the sensitivity result diagram of the nano-detection materials prepared in Examples 1-3 and Comparative Examples 1-2 of the present invention. As shown in the figure, the detection limit of the nano-detection materials prepared in Examples 1-3 is close to 1.0×10 -6 mol / L. The detection limit of the nano-detection material prepared in Comparative Example 1 is 1.13×10 -5 mol / L, and the detection limit of the nano-detection material prepared in Comparative Example 2 is 4.27×10 -6 mol / L. This shows that the detection limit of Hg 2+ detected by the examples prepared in the present invention is lower than that of the nano-detection materials prepared in the comparative examples. The nano-detection material prepared in the present invention can improve the adsorption capacity for Hg 2+ through the imidazole group, thereby improving the sensitivity to Hg 2+ . At the same time, S-S pairs of gold nanoparticles can improve the dispersion of gold nanoparticles in the detection material and the detection system, avoiding the influence of the environment on gold nanoparticles, thereby improving the sensitivity of the nano-detection material prepared in the present invention.

[0062] Experimental Example 3

[0063] In this experimental example, the stability of the nano-detection materials prepared in Examples 1-3 and Comparative Examples 1-2 was determined. A 5.0×10 -6 mol / L Hg 2+ solution was prepared, and the pH of the Hg 2+ solution was adjusted to 2.0, 4.0, 6.0, 8.0, and 10.0. According to the addition amount of 3 g / L, the nano-detection materials were placed in the Hg 2+ solution and shaken on a shaker at 150 rpm. After 10 min, the ultraviolet-visible spectrophotometer was used to measure and calculate A 650 / A 520 .

[0064] Figure 4 is the stability result diagram of the nano-detection materials prepared in Examples 1-3 and Comparative Examples 1-2 of the present invention at different pH values. As shown in the figure, in the range of pH = 3-10, Examples 1-3 can maintain the detection performance. In acidic conditions, the imidazole group can provide protonation sites, avoiding the influence of protonation in the acidic environment on the surface of gold nanoparticles. Although the decrease in the pH of the environment affects the detection performance of the nano-detection materials to a certain extent, the nano-detection materials prepared in the present invention can still maintain the detection performance. Compared with Comparative Example 1, in the absence of imidazole group modification, in an acidic environment, gold nanoparticles are affected by protonation in the environment, resulting in a competitive adsorption effect between protons and heavy metal cations, which greatly affects the detection performance of gold nanoparticles; in a basic environment, the surface of gold nanoparticles has a negative charge, which can improve the dispersion performance of gold nanoparticles in the environment. When the alkalinity gradually increases, gold nanoparticles can quickly adsorb excessive heavy metal cations, resulting in a rapid increase in particle size, promoting the excessive aggregation of gold nanoparticles, and a rapid increase in absorbance, thus affecting the detection performance of gold nanoparticles. Compared with Comparative Example 2, the nano-detection materials prepared in the present invention are modified with imidazole groups and S-S bonds on the surface of gold nanoparticles. The S-S bond maintains structural stability in acidic and weakly basic states. As the alkalinity increases, S-S breaks, and the generated S - can prevent a large amount of metal cations from undergoing excessive adsorption on the surface of gold nanoparticles, thereby maintaining the stability of the detection performance of the nano-detection materials.

[0065] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention.

[0066] The above describes the present invention and its embodiments. Such description is not restrictive. What is shown in the drawings is only one of the embodiments of the present invention, and the actual application is not limited thereto. In summary, if those of ordinary skill in the art are inspired by it and, without departing from the gist of the present invention, design in a non-creative way similar methods and embodiments to this technical solution, they shall fall within the protection scope of the present invention.

Claims

1. A method for preparing a nanometer detection material for detecting heavy metal ions in industrial wastewater, characterized in that: The specific steps include: S1. Disperse cellulose in a 50 vol% methanol aqueous solution, adjust the pH to 4-4.5, place in a nitrogen environment, add AIBN and mix well to obtain a pretreated cellulose solution; S2, dissolving N-hydroxyethyl acrylamide in DMF, adding imidazole-2-carboxylic acid methyl ester according to the mass ratio of N-hydroxyethyl acrylamide to imidazole-2-carboxylic acid methyl ester of 1:1.1-1.2, mixing at a speed of 150-180 rpm, adding p-toluenesulfonic acid according to the mass of p-toluenesulfonic acid of 10-12% of the mass of N-hydroxyethyl acrylamide, raising the reaction temperature to 120-140° C., and performing reflux reaction for 5-7 hours. After the reaction is completed, adding deionized water for washing until the reaction system is neutral, distilling under reduced pressure, and freeze-drying to obtain imidazolyl acrylamide; S3, according to the mass ratio of imidazolyl acrylamide to cellulose being 1:1.25-1.5, the imidazolyl acrylamide solution prepared in step S2 is added to the pretreated cellulose solution prepared in step S1, and after uniform mixing, N,N'-bis(acrylyl)cystamine is added at a mass of 10%-20% of the mass of imidazolyl acrylamide, the reaction temperature is raised to 60-80°C under nitrogen conditions, the reaction is stirred at a speed of 200-250rpm, the reaction is reacted for 4-6h, washed with anhydrous ethanol, and vacuum dried to obtain modified cellulose; S4, dissolving the modified cellulose prepared in step S3 in DMAC, preparing a HAuCl4 solution according to the added mass of HAuCl4 being 3.6%-5% of the mass of the modified cellulose, and dropwise adding the solution to the reaction system. After stirring for 30-40 minutes, adding a NaBH4 aqueous solution to ice water, continuing to stir for 15-25 minutes, washing with deionized water, and vacuum drying to obtain a nano detection material.

2. The method for preparing a nanometer detection material for detecting heavy metal ions in industrial wastewater according to claim 1, characterized in that: In step S1, the mass fraction of the cellulose in the methanol aqueous solution is 3-5%; the mass ratio of AIBN to cellulose is 1:8-10.

3. The method for preparing a nanometer detection material for detecting heavy metal ions in industrial wastewater according to claim 2, characterized in that: In step S2, the mass concentration of N-hydroxyethyl acrylamide in dichloromethane is 40-50 g / L.

4. The method for preparing a nanometer detection material for detecting heavy metal ions in industrial wastewater according to claim 3, characterized in that: In step S3, the imidazolyl acrylamide solution is a solution of imidazolyl acrylamide dissolved in a methanol aqueous solution, wherein the mass concentration of imidazolyl acrylamide is 40-80 g / L, and the volume fraction of methanol in the methanol aqueous solution is 60-80%.

5. The method for preparing a nanometer detection material for detecting heavy metal ions in industrial wastewater according to claim 4, characterized in that: In step S4, the mass fraction of the modified cellulose in DMAC is 1%-4%.

6. The method for preparing a nanometer detection material for detecting heavy metal ions in industrial wastewater according to claim 5, characterized in that: In step S4, in the HAuCl4 solution, the mass concentration of HAuCl4 in DMAC is 4-5 g / L.

7. The method for preparing a nanometer detection material for detecting heavy metal ions in industrial wastewater according to claim 6, characterized in that: In step S4, the mass concentration of NaBH4 in the NaBH4 solution is 10-12 g / L; the added mass of NaBH4 is 4%-6% of the mass of the modified cellulose.

8. A nanometer detection material for detecting heavy metal ions in industrial wastewater, characterized by: The preparation method according to any one of claims 1 to 7.

Images