Melamine-glutaraldehyde polycondensate microspheres and their adsorption and separation applications

Abstract

This invention discloses melamine-glutaraldehyde condensate microspheres and their adsorption and separation applications. The melamine-glutaraldehyde condensate microspheres are prepared by a one-pot aqueous phase mixing reaction of 100 parts by weight of acidic water, 0.3-2.0 parts by weight of a water-soluble polymer, 0-1.5 parts by weight of a pore-forming agent, 2.02-5.05 parts by weight of melamine, and 5.06-20.18 parts by weight of an aqueous glutaraldehyde solution. The acidic water refers to an aqueous solution containing a hydrogen proton concentration of 0.001-0.01 mol / L, and the glutaraldehyde aqueous solution contains 25-50% glutaraldehyde by mass. The method of this invention adopts an acid-catalyzed one-pot aqueous phase polycondensation process, which has the advantages of simple process, green energy saving, and easy control of polycondensation progress. Moreover, the obtained melamine-glutaraldehyde polycondensate microspheres do not contain free formaldehyde and have flexible methylene chain and triazine ring structure that are not found in ordinary melamine resins. It has a bright application prospect in the adsorption and separation of micro-pollutants such as organic small molecules and metal ions.

Description

Technical Field

[0001] This invention relates to the field of polymer materials engineering, and in particular to a melamine-glutaraldehyde condensate microsphere and its adsorption and separation application. Background Technology

[0002] Imine condensation is a crucial organic reaction used to synthesize amino resins, covalent organic compounds, and nanopolymer microspheres. The imine condensation of melamine and formaldehyde is commonly used to prepare melamine-formaldehyde resin, or simply melamine resin. Due to its excellent flame retardancy, heat resistance, and media stability, melamine resin has wide and important applications in electronic and electrical components, building insulation and flame retardancy, and wood-plastic composites. However, both the preparation and application of melamine resin present the problem of free formaldehyde pollution. Formaldehyde is chemically reactive; its carbonyl group can undergo imine condensation with the amino group of amino acids, exhibiting teratogenic and mutagenic properties and has been listed as a Group 1 carcinogen by the International Agency for Research on Cancer (IARC) of the World Health Organization. Furthermore, formaldehyde molecules have weak intermolecular attraction and are colorless gases at room temperature; once released from melamine resin materials used in construction, they pollute indoor air, seriously threatening human health. In recent years, as green and healthy living has become increasingly important, the application scope of melamine resin has become increasingly limited.

[0003] Glutaraldehyde is a broad-spectrum bactericide with low toxicity and rapid and strong bactericidal action. It is a highly effective disinfectant recommended by the World Health Organization and is widely used as a biocidal agent (Advanced Materials Research, 2013, 785-786: 38-41). Due to its large molecular weight, glutaraldehyde has strong intermolecular attraction, resulting in a boiling point of 187-189℃, significantly higher than formaldehyde's -19.5℃. It is liquid at room temperature and difficult to volatilize; compared to free formaldehyde, its volatile pollution is almost negligible. Therefore, some researchers have used glutaraldehyde to replace some formaldehyde in the preparation of urea-formaldehyde and melamine amino resins to reduce free formaldehyde content (Polymer Engineering and Science, 2023, 63: 499–508; Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2022, 648: 129019). However, this does not completely eliminate formaldehyde volatile pollution. The preparation of formaldehyde-free melamine-glutaraldehyde resin materials has become a research hotspot in this field for over a decade. Although both are based on imine condensation reactions, different structures and properties of melamine-glutaraldehyde polymer materials can be flexibly obtained under different process conditions and parameters, and related research has shown promising application prospects in many fields. For example, the ternary copolymer condensate of sodium aminosulfonate, glutaraldehyde, and melamine can be used as an ideal formaldehyde-free tanning agent (Indian Journal of Chemical Technology, 2015, 22: 48–55); by repeatedly performing imine condensation reactions of melamine and glutaraldehyde on the surface of silica, hyperbranched nanodendritic macromolecules can be prepared, which can be used for drug solid-phase extraction and microseparation (Journal of Molecular Liquids, 2023, 371: 121142). Loading zero-valent iron onto porous polymers of melamine and glutaraldehyde is suitable for the treatment of uranium-containing wastewater (Journal of Radioanalytical and Nuclear Chemistry, 2020, 326: 845–855). However, the aforementioned materials based on the condensation reaction of melamine and glutaraldehyde imine have not yet achieved industrial application due to complex processes, immature technology, and difficulties in mass production. In 2012, Lanzhou University disclosed a melamine-dialdehyde condensate and its synthesis method (CN 201210478103.X). This condensate has great application potential in fluorescent nanomaterials and dye-sensitized solar cells; however, due to the use of a non-aqueous phase high-temperature condensation process, this method is characterized by high energy consumption and organic solvent volatilization pollution.In 2019, Dalian University of Technology disclosed a stepwise acid-base catalytic low-temperature (10–50°C) co-condensation process (CN 201910556107.7), which can be used to prepare cavity nanospheres of "aromatic amine-melamine-dialdehyde condensate". This process has advantages such as low energy consumption and large specific surface area of ​​the product. However, the aromatic amine raw material used is highly toxic, and the stepwise acid-base catalytic process is complex, making one-pot preparation difficult. In addition, in 2014, Heilongjiang University disclosed a method for preparing melamine-dialdehyde porous spherical materials based on ultraviolet radiation (CN 201410169633.5). This method effectively overcomes the problems of low pore order, poor structural stability, and easy collapse of products obtained by solvothermal or water bath heating methods. However, this method has drawbacks such as radiation pollution and difficulty in controlling the condensation progress. Summary of the Invention

[0004] The purpose of this invention is to provide melamine-glutaraldehyde condensate microspheres and their adsorption and separation applications. The melamine-glutaraldehyde condensate microspheres are prepared using an acid-catalyzed one-pot aqueous phase condensation process, which features simple procedures, energy efficiency, and easy control of the condensation progress, thus overcoming the shortcomings of existing technologies.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A melamine-glutaraldehyde condensate microsphere is prepared from the following components by mass fraction:

[0007]

[0008] The acidic water refers to an aqueous solution with a hydrogen proton concentration of 0.001 to 0.01 mol / L, and the glutaraldehyde aqueous solution contains 25% to 50% glutaraldehyde by mass.

[0009] The preparation method of the melamine-glutaraldehyde condensate microspheres is as follows: A one-pot aqueous phase mixing reaction is used. Specifically, at room temperature, acidic water is injected into the reaction equipment. Under continuous stirring, water-soluble polymer, pore-forming agent, and melamine are added sequentially to the acidic water. After stirring and mixing evenly, the mixture is heated until the resulting suspension becomes transparent and clear. Then, the transparent and clear solution is cooled to 40–60°C, and stirring continues. Glutaraldehyde aqueous solution is added to the solution, mixed evenly, and the system is kept at a constant temperature of 40–60°C for 8–12 hours. The solution is then cooled, discharged, centrifuged, purified, filtered, washed, and dried to obtain melamine-glutaraldehyde condensate microspheres.

[0010] Furthermore, the water-soluble polymer is one or a mixture of several of the following: starch, dextrin, polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl acid, polymethyl methacrylate, polymethacrylic acid, polyN-isopropylacrylamide, carboxymethyl cellulose, polyacrylamide, polyacrylic acid, polyacrylate, ammonium polyacrylate, sodium polyacrylate, and potassium polyacrylate.

[0011] Further, the porogen is one or a mixture of several of the following: alkyl alcohol, cycloalkyl alcohol, alkyl diol, alkyl ammonium, alkyl diamine, alkyl ammonium salt, alkyl diamine salt, alkyl acid, alkyl diacid, alkyl salt, alkyl diacid, alkyl benzoic acid, alkyl phthalic acid, alkyl benzoate, alkyl phthalic acid, alkyl sulfonic acid, alkyl sulfonate, alkyl benzene sulfonic acid, alkyl benzene sulfonate, amino acid, betaine, glucoside, Triton, Span, quaternary ammonium salt.

[0012] Furthermore, the heating temperature is 95–100°C, and the stirring speed is 100–300 rpm.

[0013] The melamine-glutaraldehyde condensate microspheres provided by this invention can be used to adsorb and separate pollutants, such as for treating industrial wastewater, for purifying, regenerating or compounding wet electronic chemicals, or for recycling, regenerating or treating wastewater from the leather industry.

[0014] For example, the melamine-glutaraldehyde condensate microspheres are used for the adsorption and separation of organic micropollutants, and the steps are as follows:

[0015] (1) Fill melamine-glutaraldehyde condensate microspheres into a fluidized bed column, and install single beds, multiple beds in parallel or multiple beds in series according to the needs and application scenarios to build an adsorption separation operation system.

[0016] (2) Nitrogen gas at 100-200℃ is introduced into the resulting adsorption separation system for pretreatment;

[0017] (3) The sample to be treated is passed through the adsorption separation system at a flow rate of 0.1 to 0.3 L / h at room temperature to obtain an eluent in which organic micropollutants have been adsorbed and separated;

[0018] (4) After regenerating and activating the fluidized bed column with water vapor at 100-200℃, the adsorption separation system is recycled.

[0019] For example, the melamine-glutaraldehyde condensate microspheres are used for the adsorption and separation of metal ions or their derivatives, and the steps are as follows:

[0020] (1) Fill melamine-glutaraldehyde condensate microspheres into a fluidized bed column, and install single beds, multiple beds in parallel or multiple beds in series according to the needs and application scenarios to build an adsorption separation operation system.

[0021] (2) Pretreatment is performed by introducing gas at 100-200℃ into the resulting adsorption separation system;

[0022] (3) The sample to be treated is passed through the adsorption separation system at a flow rate of 0.02 to 0.2 L / h at room temperature to obtain an eluent in which metal ions and derivatives have been adsorbed and separated.

[0023] (4) After regenerating and activating the fluidized bed column with nitric acid, hydrochloric acid, phosphoric acid or sulfuric acid solution, the adsorption separation system is recycled.

[0024] The significant advantages of this invention are: (1) It adopts an acid-catalyzed one-pot aqueous phase polycondensation process, which has the characteristics of simple process, green environmental protection, and easy control of polycondensation progress; (2) It uses the method of switching between room temperature, high temperature (95~100℃), and low temperature (40~60℃) to control the temperature, which can effectively balance the contradiction between material mixing and energy consumption reduction, so that the overall energy consumption is lower than the traditional method of continuous high temperature mixing and reaction; (3) The melamine-glutaraldehyde polycondensate microspheres obtained by implementing the method of this invention do not contain free formaldehyde and have flexible methylene chain and triazine ring structure that ordinary melamine resin does not have, which has a bright application prospect in the adsorption and separation of small organic molecules, metal ions and other micro pollutants; (4) The application of the melamine-glutaraldehyde polycondensate microspheres "unitized or modularized" filling into fluidized bed columns and then combining them in series or parallel, compared with the traditional packed column method, can not only improve its flexibility and adaptability in different application scenarios, but also facilitate parallel operation and save time and energy consumption for recycling and regeneration. Attached Figure Description

[0025] Figure 1 This is an optical microscope image of the monodisperse melamine-glutaraldehyde condensate microspheres obtained in Example 1.

[0026] Figure 2 This is an optical microscope image of the monodisperse melamine-glutaraldehyde condensate microspheres obtained in Example 2.

[0027] Figure 3 This is an optical microscope image of the monodisperse melamine-glutaraldehyde condensate microspheres obtained in Example 3.

[0028] Figure 4 This is an optical microscope image of the monodisperse melamine-glutaraldehyde condensate microspheres obtained in Example 4.

[0029] Figure 5 This is an optical microscope image of the monodisperse melamine-glutaraldehyde condensate microspheres obtained in Example 5.

[0030] Figure 6 This is an optical microscope image of the monodisperse melamine-glutaraldehyde condensate microspheres obtained in Example 6.

[0031] Figure 7 This is an optical microscope image of the monodisperse melamine-glutaraldehyde condensate microspheres obtained in Example 7.

[0032] Figure 8 This is an optical microscope image of the monodisperse melamine-glutaraldehyde condensate microspheres obtained in Example 8.

[0033] Figure 9 This is an optical microscope image of the monodisperse melamine-glutaraldehyde condensate microspheres obtained in Example 9.

[0034] Figure 10 This is an optical microscope image of the monodisperse melamine-glutaraldehyde condensate microspheres obtained in Example 10.

[0035] Figure 11 The infrared absorption spectrum of the melamine-glutaraldehyde condensate microspheres obtained in Example 1 is shown.

[0036] Figure 12 These are the structural units of melamine-glutaraldehyde condensate microspheres. Detailed Implementation

[0037] The present invention will be described in more detail below through specific embodiments, but this is not intended to limit the present invention.

[0038] Example 1

[0039] At 25°C, 1000g of acidic water with a hydrogen proton concentration of 0.001mol / L (pH 3) was poured into a 3L round-bottom three-necked flask. While stirring continuously at 100rpm, 6g of polyvinyl alcohol, 1g of n-butanol, and 20.2g of melamine were added sequentially. After thorough mixing and dispersion, the solution was heated to 95°C until the resulting suspension became transparent and clear. The solution was then cooled to a set temperature of 55°C, and while continuing stirring, 101.2g (95.2mL) of 50% glutaraldehyde (density 1.063g / cm³) was added. 3 The aqueous solution was mixed evenly and the system was kept at the set temperature for 12 hours. After cooling and discharging, the mixture was centrifuged, purified, filtered, washed and dried to obtain melamine-glutaraldehyde condensate microspheres 1 (MA-GA condensate microspheres 1).

[0040] Example 2

[0041] At 25°C, 1000g of acidic water with a hydrogen proton concentration of 0.01mol / L (pH 2) was poured into a 3L round-bottom three-necked flask. While stirring continuously at 300rpm, 6g of polyvinyl alcohol and 20.2g of melamine were added sequentially. After thorough mixing and dispersion, the mixture was heated to 100°C until the resulting suspension became transparent and clear. The clear suspension was then cooled to a set temperature of 60°C, and while continuing stirring, 118.0g (111mL) of 50% glutaraldehyde (density 1.063g / cm³) was added. 3 The aqueous solution was mixed evenly and the system was kept at the set temperature for 8 hours. After cooling and discharging, the mixture was centrifuged, purified, filtered, washed and dried to obtain melamine-glutaraldehyde condensate microspheres 2 (MA-GA condensate microspheres 2).

[0042] Example 3

[0043] At 25°C, 1000g of acidic water with a hydrogen proton concentration of 0.0036mol / L (pH 2.5) was poured into a 3L round-bottom three-necked flask. While stirring continuously at a set speed of 200rpm, 3g of polyvinyl alcohol, 0.001g of Triton, and 20.2g of melamine were added sequentially. After thorough mixing and dispersion, the mixture was heated to 97.5°C until the resulting suspension became transparent and clear. The clear suspension was then cooled to a set temperature of 57.5°C, and while continuing stirring, 118.0g (111mL) of 50% glutaraldehyde (density 1.063g / cm³) was added. 3 The aqueous solution was mixed evenly and the system was kept at the set temperature for 10 hours. After cooling and discharging, the mixture was centrifuged, purified, filtered, washed and dried to obtain melamine-glutaraldehyde condensate microspheres 3 (MA-GA condensate microspheres 3).

[0044] Example 4

[0045] At room temperature (28°C), 1000 g of acidic water with a hydrogen proton concentration of 0.0036 mol / L (pH 2.5) was poured into a 3-liter round-bottom three-necked flask. While continuously stirring at a set speed of 200 rpm, a mixture of 4 g polyvinyl alcohol, 0.1 g polyethylene glycol, and 0.4 g β-cyclodextrin, 15 g sodium dodecylbenzenesulfonate, and 20.2 g melamine were added sequentially. After thorough mixing and dispersion, the mixture was heated to 95°C until the resulting suspension became transparent and clear. The clear suspension was then cooled to a set temperature of 57.5°C, and while continuing to stir, 109.7 g (103.2 mL) of 50% glutaraldehyde (density 1.063 g / cm³) was added. 3The aqueous solution was mixed evenly and the system was kept at the set temperature for 10 hours. After cooling and discharging, the mixture was centrifuged, purified, filtered, washed and dried to obtain melamine-glutaraldehyde condensate microspheres 4 (MA-GA condensate microspheres 4).

[0046] Example 5

[0047] At 35°C, 1000g of acidic water containing 0.001mol / L hydrogen protons (pH 3) was poured into a 3L round-bottom three-necked flask. While continuously stirring at a set speed of 100rpm, 6g of polyvinyl alcohol, a porogen composed of 0.3g aspartic acid, 0.2g p-toluic acid, and 0.1g hexadecyltrimethylammonium bromide, and 20.2g melamine were added sequentially. After stirring and dispersing evenly, the mixture was heated to 95°C until the resulting suspension became transparent and clear. The clear suspension was then cooled to a set temperature of 55°C, and while continuing to stir, 101.2g (95.2mL) of 50% glutaraldehyde (density 1.063g / cm³) was added. 3 The aqueous solution was mixed evenly and the system was kept at the set temperature for 12 hours. After cooling and discharging, the mixture was centrifuged, purified, filtered, washed and dried to obtain melamine-glutaraldehyde condensate microspheres 5 (MA-GA condensate microspheres 5).

[0048] Example 6

[0049] At 30°C, 1000g of acidic water with a hydrogen proton concentration of 0.002mol / L (pH 2.7) was poured into a 3L round-bottom three-necked flask. 20g of polyvinyl alcohol and 30.8g of melamine were added sequentially to the acidic water while continuously stirring at a set speed of 250rpm. After thorough mixing and dispersion, the solution was heated to 98°C until the resulting suspension became transparent and clear. The solution was then cooled to a set temperature of 40°C, and while continuing to stir, 201.8g (190.4mL) of 25% glutaraldehyde (density 1.06g / cm³) was added. 3 The aqueous solution was mixed evenly and the system was kept at the set temperature for 24 hours. After cooling and discharging, the mixture was centrifuged, purified, filtered, washed and dried to obtain melamine-glutaraldehyde condensate microspheres 6 (MA-GA condensate microspheres 6).

[0050] Example 7

[0051] At room temperature (20°C), 1000 g of acidic water with a hydrogen proton concentration of 0.001 mol / L (pH 3) was poured into a 3-liter round-bottom three-necked flask. While stirring continuously at a set speed of 100 rpm, 12 g of polyvinyl alcohol, 2.2 g of Triton, and 50.5 g of melamine were added sequentially. After stirring and dispersing evenly, the mixture was heated to 95°C until the resulting suspension became transparent and clear. The clear suspension was then cooled to a set temperature of 50°C, and while continuing to stir, 189.3 g (178.6 mL) of 25% glutaraldehyde (density 1.06 g / cm³) was added. 3 The aqueous solution was mixed evenly and the system was kept at the set temperature for 16 hours. After cooling and discharging, the mixture was centrifuged, purified, filtered, washed and dried to obtain melamine-glutaraldehyde condensate microspheres 7 (MA-GA condensate microspheres 7).

[0052] Example 8

[0053] At room temperature (28°C), 1000 g of acidic water with a hydrogen proton concentration of 0.001 mol / L (pH 3) was poured into a 3-liter round-bottom three-necked flask. While stirring continuously at a set speed of 200 rpm, 6 g of polyvinyl alcohol, 0.9 g of lauryl dimethylamine oxide, and 20.2 g of melamine were added sequentially. After stirring and dispersing evenly, the mixture was heated to 95°C until the resulting suspension became transparent and clear. The clear suspension was then cooled to a set temperature of 55°C, and while continuing to stir, 201.8 g (190.4 mL) of 25% glutaraldehyde (density 1.06 g / cm³) was added. 3 The aqueous solution was mixed evenly and the system was kept at the set temperature for 12 hours. After cooling and discharging, the mixture was centrifuged, purified, filtered, washed and dried to obtain melamine-glutaraldehyde condensate microspheres 8 (MA-GA condensate microspheres 8).

[0054] Example 9

[0055] At room temperature (20°C), 1000 g of acidic water with a hydrogen proton concentration of 0.01 mol / L (pH 2) was poured into a 3-liter round-bottom three-necked flask. While stirring continuously at a set speed of 300 rpm, 6 g of polyvinyl alcohol, 3 g of sodium dodecyl sulfonate, and 20.2 g of melamine were added sequentially. After thorough mixing and dispersion, the mixture was heated to 95°C until the resulting suspension became transparent and clear. The clear suspension was then cooled to a set temperature of 60°C, and while continuing stirring, 117.7 g (111.0 mL) of 25% glutaraldehyde (density 1.06 g / cm³) was added. 3The aqueous solution was mixed evenly and the system was kept at the set temperature for 8 hours. After cooling and discharging, the mixture was centrifuged, purified, filtered, washed and dried to obtain melamine-glutaraldehyde condensate microspheres 9 (MA-GA condensate microspheres 9).

[0056] Example 10

[0057] At 25°C, 1000g of acidic water with a hydrogen proton concentration of 0.01mol / L (pH 2) was poured into a 3L round-bottom three-necked flask. While continuously stirring at a set speed of 300rpm, a mixture of 5.7g polyvinyl alcohol, 0.1g sodium polyacrylate, and 0.2g polyethylene glycol, 3g hexadecyltrimethylammonium bromide, and 20.2g melamine were added sequentially. After thorough mixing and dispersion, the mixture was heated to 97.5°C until the resulting suspension became transparent and clear. The solution was then cooled to a set temperature of 60°C, and while continuing to stir, 117.7g (111.0mL) of 25% glutaraldehyde (density 1.06g / cm³) was added. 3 The aqueous solution was mixed evenly and the system was kept at the set temperature for 8 hours. After cooling and discharging, the mixture was centrifuged, purified, filtered, washed and dried to obtain melamine-glutaraldehyde condensate microspheres 10 (MA-GA condensate microspheres 10).

[0058] The morphology of the melamine-glutaraldehyde condensate microspheres obtained in Examples 1-10 was observed using an optical microscope (XSP-10CA, Shanghai Youke Instrument Co., Ltd.). The results are shown in the figure. Figures 1-10 As shown in these figures, melamine-glutaraldehyde condensation microspheres can be obtained by carrying out acid-catalyzed one-pot aqueous phase polycondensation reactions according to the process parameters described in Examples 1-10 of the present invention. Furthermore, the particle size of the obtained microspheres varies with the different process parameters in each example, fluctuating between 2 and 12 μm. This result indicates that the method of the present invention can flexibly adjust the process parameters to control the polycondensation reaction progress, thereby preparing melamine-glutaraldehyde condensation microspheres with different particle sizes.

[0059] The infrared absorption activity of melamine-glutaraldehyde condensate microspheres 1 was investigated using a Fourier transform infrared spectrometer (NICOLET iS50, Thermo Fisher Scientific). Typical infrared spectra are shown below. Figure 11 At 3370cm -1 The OH stretching of hydroxyl groups and the NH stretching of amino groups overlap with each other; at 2945 cm⁻¹ -1 2958cm -1 1458cm -1 and 1354cm -1The absorption peaks at 1578 cm⁻¹ are sequentially attributed to the antisymmetric stretching, symmetric stretching, antisymmetric bending, and symmetric bending vibrations of the methylene group (-CH₂-); -1 1564cm -1 and 813cm -1 The characteristic absorption peak at 2738 cm⁻¹ belongs to the triazine ring; -1 1721cm -1 and 591cm -1 The absorption peaks at 1497 cm⁻¹ are successively attributed to the CH stretching, C=O stretching, and in-plane bending absorption peaks of the aldehyde group connected to the CC(CO) group; -1 There is an NH denaturation absorption peak for aromatic secondary amines at 1164 cm⁻¹. -1 and 1007cm -1 Two stretching absorption peaks, attributed to CN and CO bonds respectively, were observed. Infrared spectroscopy results indicate that melamine-glutaraldehyde condensate microspheres 1 possess... Figure 12 The structural unit shown.

[0060] Application examples

[0061] Melamine-glutaraldehyde condensate microspheres (MA-GA condensate microspheres) were used to adsorb and separate methylene blue and chromium ions. The experimental results are shown in Table 1.

[0062] The adsorption separation test of methylene blue was carried out as follows: 2–5 g of MA-GA condensation microspheres were packed into a fluidized bed column with a diameter of 2–5 cm and a height of 2–4 cm; 3–12 fluidized bed columns of the same size were prepared in parallel and connected in series or parallel according to actual needs to build an adsorption separation system for organic micropollutants; nitrogen gas at 100–200 °C was introduced into the built adsorption separation system for heat treatment for 12–4 hours, and then cooled to room temperature; 0.8–4.2 L of 100 mg / L methylene blue sample was passed through the built adsorption separation system at room temperature at a flow rate of 0.1–0.3 L / h, the eluent was collected, and the concentration of methylene blue was detected by a UV-Vis spectrophotometer (T6 New Century, Beijing Purkinje General Instrument Co., Ltd.). The concentration of methylene blue in the eluent was examined to see if it was lower than the detection limit of the spectrophotometer. If it was lower than the detection limit, it was considered that methylene blue was not detected. After regenerating and activating the fluidized bed column with 3-12 L of steam at 100-200℃, perform the same methylene blue elution experiment in the same adsorption separation system as described above, repeat 3 times, and test and determine whether methylene blue is detected in the eluent.

[0063] The chromium ion adsorption separation experiment was conducted as follows: 2–5 g of MA-GA condensation microspheres were packed into a fluidized bed column with a diameter of 2–5 cm and a height of 2–4 cm; 3–12 fluidized bed columns of the same size were prepared in parallel and connected in series or parallel according to actual needs to construct a metal ion micro-pollutant adsorption separation system; nitrogen gas at 100–200°C was passed through the constructed adsorption separation system for heat treatment for 12–4 hours, followed by cooling to room temperature; 0.8–4.7 L of a 10 mg / L potassium dichromate (AR, Sinopharm Chemical Reagent Co., Ltd.) aqueous solution with a pH of 1–10, referred to as the chromium solution sample, was passed through the constructed adsorption separation system at a flow rate of 0.02–0.2 L / h, and the eluent was collected and analyzed using ICP-MS (ICAP Qc, Thermo Fisher). The chromium content was detected by scientific analysis, and the chromium removal rate (R) was calculated using the following formula: R = (C0 - C) / C0 × 100%, where C0 is the chromium concentration (mg / L) before the chromium solution sample was injected and before elution; C is the chromium concentration (mg / L) after the chromium solution sample was injected and eluted. After regenerating and activating the fluidized bed column by rinsing with 0.05–0.2 mol / L nitric acid, hydrochloric acid, phosphoric acid, or sulfuric acid solution, the adsorption separation system was recycled. The same chromium elution experiment was performed in the same adsorption separation system according to the aforementioned method, repeated 3 times. The chromium content before and after elution was detected by ICP-MS, and the chromium removal rate (R) was calculated.

[0064] Table 1. Experimental results of adsorption and separation of methylene blue and chromium ions by melamine-glutaraldehyde condensate microspheres.

[0065]

[0066]

[0067] As shown in Table 1, the melamine-glutaraldehyde condensate microspheres 1-10 (MA-GA condensate microspheres 1-10) obtained by the method of this invention, when applied according to the application method provided by this invention, not only exhibit a removal rate of 74.9-99.9% for 10 mg / L chromium ions, but also a near 100% adsorption and removal rate for 100 mg / L methylene blue, meaning the residual amount of methylene blue in the eluent is below the detection limit of the UV-Vis spectrophotometer. Furthermore, the removal capacity of MA-GA condensate microspheres 1-10 for 10 mg / L chromium ions after one or two regenerations is no different from their initial use, and the removal capacity for 100 mg / L methylene blue after one, two, or three regenerations is also no different from their initial use. These results indicate that the MA-GA condensate microspheres provided by the method of this invention have excellent adsorption and separation performance for methylene blue and chromium ions, two simulated industrial micro-pollutants, and this performance can be regenerated and activated multiple times without significant deterioration.

Claims

1. A melamine-glutaraldehyde condensate microsphere, characterized in that, It is prepared from the following components by mass fraction: 100 parts acidic water 0.3~2.0 parts of water-soluble polymer 0-1.5 parts of pore-forming agent Melamine 2.02~5.05 parts 5.06–20.18 parts of glutaraldehyde aqueous solution; The acidic water refers to an aqueous solution with a hydrogen proton concentration of 0.001~0.01 mol / L, and the glutaraldehyde aqueous solution contains 25~50% glutaraldehyde by mass. The water-soluble polymer is one or a mixture of several of the following: starch, dextrin, polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl acid, polymethacrylic acid, polyN-isopropylacrylamide, carboxymethyl cellulose, polyacrylamide, polyacrylic acid, ammonium polyacrylate, sodium polyacrylate, and potassium polyacrylate. The pore-forming agent is one or a mixture of several of the following: n-butanol, Triton, sodium dodecylbenzenesulfonate, aspartic acid, p-methylbenzoic acid, hexadecyltrimethylammonium bromide, lauryl dimethylamine oxide, and sodium dodecyl sulfonate.

2. The method for preparing melamine-glutaraldehyde condensate microspheres as described in claim 1, characterized in that, At room temperature, acidic water is injected into the reaction equipment. Under continuous stirring, water-soluble polymer, pore-forming agent and melamine are added to the acidic water in sequence. After stirring and mixing evenly, the mixture is heated until the resulting suspension becomes transparent and clear. Then, the transparent and clear solution is cooled to 40-60°C, and stirring is continued. Glutaraldehyde aqueous solution is added to the solution, and the mixture is stirred evenly. The system is then kept at a constant temperature of 40-60°C for 8-12 hours. After cooling and discharging, the mixture is centrifuged, purified and filtered, washed and dried to obtain melamine-glutaraldehyde condensate microspheres.

3. The method for preparing melamine-glutaraldehyde condensate microspheres according to claim 2, characterized in that, The heating temperature is 95~100℃.

4. The method for preparing melamine-glutaraldehyde condensate microspheres according to claim 2, characterized in that, The stirring speed is 100~300 rpm.

5. The application of melamine-glutaraldehyde condensate microspheres obtained by the preparation method according to any one of claims 2 to 4 in the adsorption and separation of pollutants.

6. The application according to claim 5, characterized in that, The melamine-glutaraldehyde condensate microspheres were used for adsorption and separation of organic micropollutants, and the steps are as follows: (1) Fill melamine-glutaraldehyde condensate microspheres into a fluidized bed column, and install single beds, multiple beds in parallel or multiple beds in series to build an adsorption separation operation system according to the needs and application scenarios; (2) Nitrogen gas at 100~200℃ is introduced into the resulting adsorption separation system for pretreatment; (3) The sample to be treated is passed through the adsorption separation system at a flow rate of 0.1~0.3 L / h at room temperature to obtain the eluent in which the organic micro-pollutants have been adsorbed and separated; (4) After regenerating and activating the fluidized bed column with steam at 100~200℃, the adsorption separation system is recycled.

7. The application according to claim 5, characterized in that, The melamine-glutaraldehyde condensate microspheres are used for the adsorption and separation of metal ions or their derivatives, as follows: (1) Fill melamine-glutaraldehyde condensate microspheres into a fluidized bed column, and install single beds, multiple beds in parallel or multiple beds in series to build an adsorption separation operation system according to the needs and application scenarios; (2) Nitrogen gas at 100~200℃ is introduced into the resulting adsorption separation system for pretreatment; (3) The sample to be treated is passed through the adsorption separation system at a flow rate of 0.02~0.2 L / h at room temperature to obtain an eluent in which metal ions and derivatives have been adsorbed and separated; (4) After regenerating and activating the fluidized bed column with nitric acid, hydrochloric acid, phosphoric acid or sulfuric acid solution, the adsorption separation system is recycled.

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