Preparation method and application of polyampholyte microgel adsorbent for removing trace thallium

Abstract

This invention discloses a method for preparing and applying a polyamphoteric electrolyte microgel adsorbent for removing trace amounts of thallium. The invention utilizes nanocellulose and polymer monomers to construct an amphoteric electrolyte microgel containing positive and negative ion pairs. Its small size contains a large amount of water, resulting in high osmotic pressure. Furthermore, the adsorption sites on the gel are fully exposed to the external environment, facilitating the easy diffusion of metal ions into the gel interior for rapid and efficient reaction with the adsorption sites, thereby effectively adsorbing heavy metal ions. The thallium ion concentration after treatment with the polyamphoteric electrolyte microgel is as low as approximately 2 μg / L, demonstrating excellent trace thallium ion treatment capability. Simultaneously, the gel can be reused more than five times while maintaining over 90% of its performance, solving the problem of deep purification treatment of thallium in smelting wastewater.

Description

Technical Field

[0001] This invention relates to the field of deep purification technology for heavy metals in wastewater, and more specifically, to a method for preparing and applying a polyampholyte microgel adsorbent for removing trace amounts of thallium. Background Technology

[0002] In 2020, my country's annual production of wastewater from lead and zinc smelting reached 70.15 million tons, of which approximately 14.57 million tons contained thallium. Thallium ions are highly toxic substances that can affect the transmission of nerve synapses in the human body. Currently, my country stipulates that the emission limit for thallium pollutants in industrial wastewater involving thallium is 5 μg / L (DB43 / 968-2014). Therefore, developing a novel material for the trace treatment of thallium ions in smelting wastewater to achieve deep purification and compliant discharge of thallium is of great significance.

[0003] Currently, the commonly used method is precipitation. However, TlOH is a strong alkali that is readily soluble in water; therefore, using lime or similar precipitants to treat thallium-containing wastewater is ineffective in removing TlOH. + Similarly, Tl₂S has a precipitation equilibrium constant pKsp of 20.30 and a solubility of approximately 95 μg / L, making it difficult to meet emission standards. Adsorption methods also have many drawbacks. For example, granular adsorbents such as activated carbon and chelating resins have small pore structures and hydrophobic frameworks, resulting in low diffusion rates of metal ions during the internal diffusion stage. While nanomaterials offer faster adsorption rates and larger adsorption capacities, they are difficult to reuse and easily generate toxic sludge. Therefore, adsorbents that simultaneously possess advantages such as low cost, high adsorption performance, easy separation, and reusability are urgently needed in water treatment processes.

[0004] Polyamphoteric electrolyte microgels contain a polymeric interpenetrating network and multiple positive and negative ion pairs, exhibiting better mechanical stability and higher osmotic pressure compared to traditional hydrogels. In recent years, they have received significant attention from fields such as chemistry, materials science, medicine, biology, and environmental science. Polyamphoteric electrolyte microgels synthesized using microfluidic technology possess characteristics such as positive and negative ion pairs, small size, high water content, and high osmotic pressure. Furthermore, the adsorption sites on the gel are fully exposed to the external environment, allowing metal ions to easily diffuse into the gel and react rapidly and efficiently with the adsorption sites. Combined with this network of two interpenetrating polymers and dynamic electrostatic interactions, the highly stable, high-adsorption-rate, and high-adsorption-capacity polyamphoteric electrolyte gels have become suitable for the trace treatment of thallium ions in water-based metallurgical wastewater.

[0005] CN106390956B, "A Method for Preparing and Applying a Dual-Network Gel Adsorbent for Treating Heavy Metal Wastewater," discloses a method using agar and acrylic acid as raw materials. A one-step sol-gel process is employed to prepare a gel, which is then modified with epichlorohydrin as a crosslinking agent and triethylenetetramine as a crosslinking compound through amino functionalization. This process yields a dual-network gel with superior mechanical properties and excellent removal efficiency for heavy metals. The gel prepared by this patent has a three-dimensional porous network structure with high osmotic pressure, enabling rapid adsorption of heavy metal ions from the solution. Furthermore, all adsorption sites in the network structure are fully exposed, resulting in a high adsorption capacity. The interpenetrating structure of the two networks and the electrostatic interaction between positive and negative ion pairs significantly enhance the mechanical properties of the gel, allowing for direct and effective separation from the adsorbed solution, thus achieving rapid and effective recovery of the adsorbent. However, the heavy metal adsorbent prepared by this method is suitable only for the adsorption of high concentrations of heavy metals such as lead, cadmium, and copper. At low concentrations, the adsorption efficiency of this type of heavy metal ions is low, making it difficult to treat trace amounts. For example, the emission limit for thallium pollutants is 5 μg / L, and wastewater using the aforementioned heavy metal adsorbents is unlikely to meet the emission standards. Summary of the Invention

[0006] The technical problem to be solved by the present invention is that the treatment of thallium ions in smelting wastewater in many existing technologies is difficult to achieve the emission standard of 5 μg / L. The present invention provides a method for preparing a polyamplitude electrolyte microgel adsorbent for removing trace amounts of thallium.

[0007] Another technical problem to be solved by the present invention is to provide the application of the prepared polyampholyte microgel adsorbent.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] A method for preparing a polyampholyte microgel adsorbent for removing trace amounts of thallium, characterized by the following steps:

[0010] S1. Add a certain mass of polymer monomer to the nanocellulose dispersion, then add a photoinitiator and a crosslinking agent, mix well to obtain a mixed solution;

[0011] S2. The mixed solution is injected into the microfluidic chip, with the mixed solution as the inner phase and mineral oil as the outer phase. A gelation reaction is carried out under ultraviolet light to obtain microgels.

[0012] S3. Add the microgel to an alkaline organic solution containing epichlorohydrin to carry out solvent replacement and grafting reaction of the gel;

[0013] S4. The grafted gel was placed in an organic solution for modification, and after the reaction, it was soaked and washed to obtain amphoteric electrolyte microgel.

[0014] The monomer mentioned in S1 is one of acrylamide, acrylic acid, hydroxymethylacrylamide, hydroxyethyl acrylate, n-butyl acrylate, methacrylic acid, and acrylonitrile;

[0015] The organic solution mentioned in S4 is an aqueous solution containing ethylenediaminetetraacetic acid, 1,2-diaminocyclohexanetetraacetic acid, or aminotriacetic acid.

[0016] Furthermore, the nanocellulose is nano-plant cellulose, which is swollen by a potassium hydroxide solution.

[0017] Furthermore, the mass fraction of nanocellulose in the mixed solution described in S1 is 2-10%, and the mass fraction of monomer is 5-20%.

[0018] Further, the photoinitiator in S1 is 0.1 to 1 mol of monomer molar concentration, and the crosslinking agent is 0.1 to 3 mol of monomer molar concentration.

[0019] Furthermore, the inner phase channel of the microfluidic chip described in S2 has a height of 500 μm and a width of 500 μm, the outer phase channel has a height of 610 μm and a width of 670 μm, and the long serpentine channel has a length of 15 cm.

[0020] Furthermore, the organic solvent mentioned in S3 is one of ethyl acetate, dimethyl sulfoxide, acetone, and DMF.

[0021] Furthermore, the amount of epichlorohydrin added in S3 is 1-10% of the organic solvent.

[0022] Furthermore, the concentration of the organic solution in S4 is 5-30%.

[0023] Furthermore, the reaction temperature in S3 is 30–70°C, and the reaction time is 1–5 hours; the reaction temperature in S4 is 50–70°C, and the reaction time is 1–3 hours.

[0024] The adsorbent obtained by the above-described method for preparing a polyampholyte microgel adsorbent for removing trace amounts of thallium is applied to the purification of heavy metals in smelting wastewater.

[0025] Compared with existing technologies, the beneficial effects are:

[0026] This invention utilizes nanocellulose and polymer monomers to construct amphoteric electrolyte microgels containing positive and negative ion pairs. These microgels contain a large amount of water within their small size, exhibiting high osmotic pressure. Furthermore, the adsorption sites on the gel are fully exposed to the external environment, facilitating the easy diffusion of metal ions into the gel interior for rapid and efficient reaction with these sites, thus effectively adsorbing heavy metal ions. Moreover, this invention employs a fluid-controlled method to prepare the gel, eliminating the need for template preparation and cutting, reducing polymer chain damage caused by gel surface cutting, and maintaining the gel's excellent mechanical properties.

[0027] The polyamphoteric electrolyte microgel material prepared by the method of this invention exhibits good purification capabilities and stable physical and chemical properties. In wastewater with a thallium ion concentration of approximately 45 μg / L, the concentration is optimally reduced to around 2 μg / L after adsorption by the polyamphoteric electrolyte microgel, demonstrating excellent trace thallium ion treatment capabilities. Furthermore, the gel can be reused more than five times while retaining over 90% of its performance. The preparation and processing methods of this invention are environmentally friendly and pollution-free. Attached Figure Description

[0028] Figure 1 This is a microscope image of the synthesis process of amphoteric electrolyte microgels prepared by microfluidic control in Example 3.

[0029] Figure 2 SEM image of the polyampholyte microgel prepared in Example 3;

[0030] Figure 3 The graph shows the effect of solution pH on the adsorption of thallium ions by the amphoteric electrolyte microgel.

[0031] Figure 4 The figure shows the effect of common ions on the adsorption of thallium ions by polyampholyte microgels.

[0032] Figure 5 The kinetic diagram of thallium ion adsorption in the polyampholyte microgel prepared in Example 3;

[0033] Figure 6 Isothermal adsorption curves of thallium ions adsorbed by the polyampholyte microgel prepared in Example 3.

[0034] Figure 7 The selective adsorption diagram of various heavy metals on the polyampholyte microgel prepared in Example 3 is shown. Detailed Implementation

[0035] The following examples further explain and clarify the invention, but the specific examples do not limit the invention in any way. Unless otherwise specified, the methods and equipment used in the examples are conventional methods and equipment in the art, and the raw materials used are all commercially available.

[0036] Example 1

[0037] This embodiment provides a method for preparing a polyampholyte microgel adsorbent for removing trace amounts of thallium, the steps of which include:

[0038] S1. Take 3g of Astragalus waste residue and swell it in the amorphous and crystalline regions with 3% potassium hydroxide solution. Then, treat it in 6% potassium hydroxide (80℃) for 2 hours to remove hemicellulose, residual starch and pectin. Soak the purified sample in 100mL of distilled water and then place it in a cell disruptor with a power of 1200W and a frequency of 25kHz for 30 minutes to disperse the nanofibers, and obtain a 3% nanocellulose dispersion.

[0039] S2. Add 1.2 g of acrylamide to 6 mL of nanocellulose dispersion, and add 0.25 mol% of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone and 1.5 mol% of N,N-methylenebisacrylamide, and mix well to obtain a mixed solution.

[0040] S3. The mixed solution, as the internal phase, and mineral oil, as the external phase, were added to a syringe pump at flow rates controlled at 0.3 ml / min and 0.9 ml / min, respectively. A gelation reaction was then carried out at a serpentine channel under 6 watts of ultraviolet light at a wavelength of 365 nm. The outflowing solution was separated into oil and water, and after centrifugation and washing three times, microgels were obtained.

[0041] S4. The microgel was then placed in 10 mL of DMF solution containing 0.1 g potassium hydroxide and 2 mL of epichlorohydrin, and reacted at 60 °C for 2 hours. The gel was then removed and transferred to 10 mL of aqueous solution containing 10% 1,2-diaminocyclohexanetetraacetic acid, and reacted at 60 °C for 2 hours. Finally, the microgel was rinsed five times with water to obtain the polyampholyte microgel.

[0042] Example 2

[0043] This embodiment provides a method for preparing a polyampholyte microgel adsorbent for removing trace amounts of thallium, the steps of which include:

[0044] S1. Take 3g of Astragalus waste residue and swell it in the amorphous and crystalline regions with 3% potassium hydroxide solution. Then, treat it in 6% potassium hydroxide (80℃) for 2 hours to remove hemicellulose, residual starch and pectin. Soak the purified sample in 100mL of distilled water and then place it in a cell disruptor with a power of 1200W and a frequency of 25kHz for 30 minutes to disperse the nanofibers, and obtain a 3% nanocellulose dispersion.

[0045] S2. Add 1.2 g of hydroxyethyl acrylate to 6 mL of nanocellulose dispersion, and add 0.5 mol% of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone and 2 mol% of N,N-methylenebisacrylamide, and mix well to obtain a mixed solution.

[0046] S3. The mixed solution, as the internal phase, and mineral oil, as the external phase, were added to a syringe pump at flow rates controlled at 0.3 ml / min and 0.9 ml / min, respectively. A gelation reaction was then carried out at a serpentine channel under 6 watts of ultraviolet light at a wavelength of 365 nm. The outflowing solution was separated into oil and water, and after centrifugation and washing three times, microgels were obtained.

[0047] S4. The microgel was then placed in 10 mL of a dimethyl sulfoxide solution containing 0.1 g potassium hydroxide and 2 mL of epichlorohydrin, and reacted at 60 °C for 2 hours. The gel was then removed and transferred to 10 mL of an aqueous solution containing 10% 1,2-diaminocyclohexanetetraacetic acid, and reacted at 60 °C for 2 hours. Finally, the microgel was rinsed five times with water to obtain the polyampholyte microgel.

[0048] Example 3

[0049] This embodiment provides a method for preparing a polyampholyte microgel adsorbent for removing trace amounts of thallium, the steps of which include:

[0050] S1. Take 3g of straw and swell it in the amorphous and crystalline regions with 3% potassium hydroxide solution. Then, treat it in 6% potassium hydroxide solution (80℃) for 2 hours to remove hemicellulose, residual starch and pectin. Soak the purified sample in 100mL of distilled water and then place it in a cell disruptor with a power of 1200W and a frequency of 25kHz. Sonicate for 30 minutes to disperse the nanofibers and obtain a 3% nanocellulose dispersion.

[0051] S2. Add 1.2 g of methacrylic acid to 6 mL of nanocellulose dispersion, and add 0.25 mol% of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone and 1.5 mol% of N,N-methylenebisacrylamide, and mix well to obtain a mixed solution.

[0052] S3. The mixed solution, as the internal phase, and mineral oil, as the external phase, were added to a syringe pump at flow rates controlled at 0.3 ml / min and 0.9 ml / min, respectively. A gelation reaction was then carried out at a serpentine channel under 6 watts of ultraviolet light at a wavelength of 365 nm. The outflowing solution was separated into oil and water, and after centrifugation and washing three times, microgels were obtained.

[0053] S4. The microgel was then placed in 10 mL of DMF solution containing 0.1 g potassium hydroxide and 3 mL of epichlorohydrin, and reacted at 60 °C for 2 hours. The gel was then removed and transferred to 10 mL of EDTA aqueous solution containing 10% EDTA, and reacted at 60 °C for 2 hours. Finally, the microgel was rinsed five times with water to obtain the polyampholyte microgel.

[0054] Example 4

[0055] This embodiment provides a method for preparing a polyampholyte microgel adsorbent for removing trace amounts of thallium, the steps of which include:

[0056] S1. Take 3g of jute and swell it in the amorphous and crystalline regions with 3% potassium hydroxide solution. Then, treat it in 6% potassium hydroxide solution (80℃) for 2 hours to remove hemicellulose, residual starch and pectin. Soak the purified sample in 100mL of distilled water and then place it in a cell disruptor with a power of 1200W and a frequency of 25kHz. Sonicate for 30 minutes to disperse the nanofibers and obtain a 3% nanocellulose dispersion.

[0057] S2. Add 1.2g of acrylic acid to 6mL of nanocellulose dispersion, and add 0.25mol% of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone and 0.5mol% of N,N-methylenebisacrylamide, and mix well to obtain a mixed solution.

[0058] S3. The mixed solution, as the internal phase, and mineral oil, as the external phase, were added to a syringe pump at flow rates controlled at 0.3 ml / min and 0.9 ml / min, respectively. A gelation reaction was then carried out at a serpentine channel under 6 watts of ultraviolet light at a wavelength of 365 nm. The outflowing solution was separated into oil and water, and after centrifugation and washing three times, microgels were obtained.

[0059] S4. The microgel was then placed in 10 mL of a dimethyl sulfoxide solution containing 0.1 g potassium hydroxide and 2 mL of epichlorohydrin, and reacted at 60 °C for 2 hours. The gel was then removed and transferred to 10 mL of an aqueous solution containing 10% 1,2-diaminocyclohexanetetraacetic acid, and reacted at 60 °C for 2 hours. Finally, the microgel was rinsed five times with water to obtain the polyampholyte microgel.

[0060] Example 5

[0061] This embodiment provides a method for preparing a polyampholyte microgel adsorbent for removing trace amounts of thallium, the steps of which include:

[0062] S1. Take 3g of Astragalus waste residue and swell it in the amorphous and crystalline regions with 3% potassium hydroxide solution. Then, treat it in 6% potassium hydroxide (80℃) for 2 hours to remove hemicellulose, residual starch and pectin. Soak the purified sample in 100mL of distilled water and then place it in a cell disruptor with a power of 1200W and a frequency of 25kHz for 30 minutes to disperse the nanofibers, and obtain a 3% nanocellulose dispersion.

[0063] S2. Add 1.2 g of acrylamide to 6 mL of nanocellulose dispersion, and add 0.5 mol% of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone and 1.5 mol% of N,N-methylenebisacrylamide, and mix well to obtain a mixed solution.

[0064] S3. The mixed solution, as the internal phase, and mineral oil, as the external phase, were added to a syringe pump at flow rates controlled at 0.2 ml / min and 0.6 ml / min, respectively. A gelation reaction was then carried out at a serpentine channel under 6 watts of ultraviolet light at a wavelength of 365 nm. The outflowing solution was separated into oil and water, and after centrifugation and washing three times, microgels were obtained.

[0065] S4. The microgel was then placed in 10 mL of DMF solution containing 0.1 g potassium hydroxide and 3 mL of epichlorohydrin, and reacted at 60 °C for 2 hours. The gel was then removed and transferred to 10 mL of EDTA aqueous solution containing 10% EDTA, and reacted at 60 °C for 2 hours. Finally, the microgel was rinsed five times with water to obtain the polyampholyte microgel.

[0066] Example 6

[0067] This embodiment provides a method for preparing a polyampholyte microgel adsorbent for removing trace amounts of thallium, the steps of which include:

[0068] S1. Take 3g of Astragalus waste residue and swell it in the amorphous and crystalline regions with 3% potassium hydroxide solution. Then, treat it in 6% potassium hydroxide (80℃) for 2 hours to remove hemicellulose, residual starch and pectin. Soak the purified sample in 100mL of distilled water and then place it in a cell disruptor with a power of 1200W and a frequency of 25kHz for 30 minutes to disperse the nanofibers, and obtain a 3% nanocellulose dispersion.

[0069] S2. Add 1.2 g of hydroxymethylacrylamide to 6 mL of nanocellulose dispersion, and add 0.25 mol% of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone and 1.5 mol% of N,N-methylenebisacrylamide, and mix well to obtain a mixed solution.

[0070] S3. The mixed solution, as the internal phase, and mineral oil, as the external phase, were added to a syringe pump at flow rates controlled at 0.2 ml / min and 0.9 ml / min, respectively. A gelation reaction was then carried out at a serpentine channel under 6 watts of ultraviolet light at a wavelength of 365 nm. The outflowing solution was separated into oil and water, and after centrifugation and washing three times, microgels were obtained.

[0071] S4. The microgel was then placed in 10 mL of DMF solution containing 0.1 g potassium hydroxide and 2 mL of epichlorohydrin, and reacted at 60 °C for 2 hours. The gel was then removed and transferred to 10 mL of aqueous solution containing 10% nitric acid triacetic acid, and reacted at 60 °C for 2 hours. Finally, the gel was rinsed five times with water to obtain the polyampholyte microgel.

[0072] Example 7

[0073] This embodiment provides a method for preparing a polyampholyte microgel adsorbent for removing trace amounts of thallium, the steps of which include:

[0074] S1. Take 3g of coconut husk and swell it in the amorphous and crystalline regions with 3% potassium hydroxide solution. Then, treat it in 6% potassium hydroxide solution (80℃) for 2 hours to remove hemicellulose, residual starch and pectin. Soak the purified sample in 100mL of distilled water and then place it in a cell disruptor with a power of 1200W and a frequency of 25kHz. Sonicate for 30 minutes to disperse the nanofibers and obtain a 3% nanocellulose dispersion.

[0075] S2. Add 1.2 g of hydroxymethylacrylamide to 6 mL of nanocellulose dispersion, and add 0.25 mol% of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone and 1.5 mol% of N,N-methylenebisacrylamide, and mix well to obtain a mixed solution.

[0076] S3. The mixed solution, as the internal phase, and mineral oil, as the external phase, were added to a syringe pump at flow rates controlled at 0.3 ml / min and 0.9 ml / min, respectively. A gelation reaction was then carried out at a serpentine channel under 6 watts of ultraviolet light at a wavelength of 365 nm. The outflowing solution was separated into oil and water, and after centrifugation and washing three times, microgels were obtained.

[0077] S4. The microgel was then placed in 10 mL of a dimethyl sulfoxide solution containing 0.1 g potassium hydroxide and 2 mL of epichlorohydrin, and reacted at 60 °C for 2 hours. The gel was then removed and transferred to 10 mL of a 10% EDTA aqueous solution, and reacted at 60 °C for 2 hours. Finally, the gel was rinsed five times with water to obtain the polyampholyte microgel.

[0078] Thallium ion adsorption experiments were conducted on the polyamplifier microgels prepared in Examples 1-7. With an initial thallium ion concentration of 45 μg / L, 1 g / L of the polyamplifier microgel (dry gel) was added for 1 h, and the thallium ion concentration was measured as shown in Table 1 below.

[0079] Table 1. Removal and recycling of thallium ions by the amphoteric electrolyte microgel.

[0080]

[0081] like Figures 3-4 As shown, the effective adsorption range of this polyampholyte microgel for thallium is between pH 3 and 7, and it also has a certain degree of resistance to common alkali metal ions and alkaline earth metal ions.

[0082] like Figure 5-6 As shown, the polyampholyte microgel exhibits a rapid adsorption rate for thallium ions, reaching adsorption equilibrium within minutes. This is attributed to the fact that the microgel synthesized using microfluidic technology has a size of 200 μm, enabling it to quickly contact thallium ions in solution. Furthermore, the microgel has a water content of approximately 80% and an internal three-dimensional network structure, allowing for rapid internal diffusion of thallium ions and adsorption onto the active sites on the gel.

[0083] The adsorption of several heavy metals by polyamphoteric electrolyte microgels in single-component and mixed-component formulations was investigated. It can be seen that, for example... Figure 7 As shown, in the single-component adsorption process, the concentration of each ion was 85.2 μg / L. Even with low concentrations of heavy metal ions, the polyamphoteric electrolyte microgel effectively adsorbed all six ions. In the competitive adsorption of mixed solutions, the six solutions were mixed in equal proportions, and the concentration of each ion decreased to 14.2 μg / L. The numerous active sites of the polyamphoteric electrolyte microgel provided sufficient adsorption capacity, and it exhibited good adsorption performance for all six ions even under competitive adsorption.

[0084] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a polyampholyte microgel adsorbent for removing trace amounts of thallium, characterized in that the steps include... include: S1. Add a certain mass of polymer monomer to the nanocellulose dispersion, then add a photoinitiator and a crosslinking agent, mix evenly to obtain a mixed solution, wherein the mass fraction of nanocellulose in the mixed solution is 2-10% and the mass fraction of monomer is 5-20%; S2. The mixed solution is injected into the microfluidic chip, with the mixed solution as the inner phase and mineral oil as the outer phase. A gelation reaction is carried out under ultraviolet light to obtain microgels. S3. Add the microgel to an alkaline organic solution containing epichlorohydrin to carry out solvent replacement and grafting reaction of the gel; S4. The grafted gel is placed in an organic solution with a mass concentration of 5-30% for modification. After the reaction, it is soaked and washed to obtain a polyampholyte microgel adsorbent. The monomer mentioned in S1 is one of acrylamide, acrylic acid, hydroxymethylacrylamide, hydroxyethyl acrylate, n-butyl acrylate, methacrylic acid, and acrylonitrile; The microfluidic chip described in S2 has an inner phase channel with a height of 500 μm and a width of 500 μm, an outer phase channel with a height of 610 μm and a width of 670 μm, and a long serpentine channel with a length of 15 cm. The organic solution mentioned in S4 is an aqueous solution containing ethylenediaminetetraacetic acid, 1,2-diaminocyclohexanetetraacetic acid, or aminotriacetic acid.

2. The method for preparing the polyampholyte microgel adsorbent for removing trace amounts of thallium according to claim 1, characterized in that, The nanocellulose is nano-plant cellulose, which is swollen by potassium hydroxide solution.

3. The method for preparing the polyampholyte microgel adsorbent for removing trace amounts of thallium according to claim 1, characterized in that, The photoinitiator in S1 is 0.1-1 mol of monomer molar concentration, and the crosslinking agent is 0.1-3 mol of monomer molar concentration.

4. The method for preparing the polyampholyte microgel adsorbent for removing trace amounts of thallium according to claim 1, characterized in that, The organic solvent in S3 is one of ethyl acetate, dimethyl sulfoxide, acetone, or DMF.

5. The method for preparing the polyampholyte microgel adsorbent for removing trace amounts of thallium according to claim 1, characterized in that, The amount of epichlorohydrin added in S3 is 1-10% of the volume of the organic solvent.

6. The method for preparing the polyampholyte microgel adsorbent for removing trace amounts of thallium according to claim 1, characterized in that, The grafting reaction in S3 is carried out at a temperature of 30-70℃ for 1-5 hours; the modification reaction in S4 is carried out at a temperature of 50-70℃ for 1-3 hours.

7. The adsorbent obtained by the preparation method of the polyampholyte microgel adsorbent for removing trace amounts of thallium according to claim 1 is applied to the purification of heavy metal thallium in smelting wastewater.

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