Preparation of coal gangue-based polymer microspheres and their application in adsorbing methylene blue and hexavalent chromium

Abstract

The application discloses coal gangue-based geopolymer microspheres, and application of the geopolymer microspheres in adsorbing methylene blue and hexavalent chromium, wherein the geopolymer microspheres are prepared by mixing coal gangue, fly ash, slag, an alkali activator, a foaming agent and a composite modifier; the geopolymer with a spherical structure is successfully prepared by modifying and utilizing industrial waste, i.e., the coal gangue, the fly ash and the slag; the prepared geopolymer has a high pore area and a large number of depressions and gullies on the surface due to the synergistic effect among the three solid powders, and can provide more adsorption active sites; the composite modifier can significantly improve the adsorption effect of the methylene blue and the hexavalent chromium, and realizes secondary utilization of the waste resources; the application effectively solves the problems of accumulation and environmental pollution of the industrial solid wastes such as the coal gangue, and provides favorable conditions for high-value utilization of the industrial solid wastes, and has a good application prospect.

Description

Technical Field

[0001] This invention relates to a geopolymer, its preparation method and application, and particularly to the preparation of coal gangue-based geopolymer microspheres and their application in adsorbing methylene blue and hexavalent chromium. Background Technology

[0002] Methylene blue is a common organic pollutant in dyeing and printing wastewater. It is widely used in dyeing hemp, silk fabrics, and paper, as well as coloring bamboo and wood. It can also be used in the manufacture of inks and lakes, and for staining biological and bacterial tissues. However, methylene blue wastewater is characterized by its high color intensity and difficulty in degradation. Discharge into rivers can severely discolor the water, impair water transparency, and affect the survival of aquatic organisms. Furthermore, methylene blue and its metabolites have teratogenic effects, and long-term exposure may pose a potential threat to human health. On the other hand, hexavalent chromium is another important inorganic pollutant in dyeing and printing wastewater. Chromium exists in nature in multiple valence states, with hexavalent chromium being the most toxic. Hexavalent chromium compounds have strong oxidizing and toxic properties and can enter the human body through various routes, such as the digestive tract, respiratory tract, skin, and mucous membranes. Long-term exposure to or ingestion of hexavalent chromium may lead to various health problems, such as skin damage, respiratory diseases, digestive system diseases, and even cancer.

[0003] Given these problems, there is an urgent need to research other effective methods to mitigate the adverse environmental impacts of methylene blue and hexavalent chromium in dyeing and printing wastewater. Developing economically feasible technologies to remove methylene blue and hexavalent chromium from the environment is of paramount importance. Methods for treating dyeing and printing wastewater fall into three main categories: physical, chemical, and biological. Physical methods, such as adsorption and membrane separation, remove suspended solids and dyes from wastewater through physical processes. Chemical methods, such as coagulation and oxidation, utilize chemical reactions to alter the properties of wastewater, reducing color and removing pollutants. Biological methods utilize the degradation effects of microorganisms to remove organic matter from wastewater. Due to its simplicity and environmental friendliness, adsorption has become a better method for treating methylene blue and hexavalent chromium.

[0004] Studies have shown that the cost and regeneration of adsorbents are the main factors limiting the development of adsorption methods, and there is an urgent need to develop economical, efficient, and regenerable adsorbents. Geopolymers, as a novel type of cementitious material, have attracted increasing attention from researchers due to their potential as adsorbents. Summary of the Invention

[0005] The purpose of this invention is to solve the aforementioned technical problems. It discloses the preparation of coal gangue-based geopolymer microspheres and their application in adsorbing methylene blue and hexavalent chromium. These geopolymer microspheres are prepared by mixing coal gangue, fly ash, slag, alkali activator, foaming agent, and composite modifier. By modifying and utilizing industrial wastes such as coal gangue, fly ash, and slag, a geopolymer with a spherical structure is successfully prepared. The prepared geopolymer, through the synergistic effect between the three solid powders, possesses a high pore area and a large number of depressions and grooves on its surface, providing more adsorption active sites. The addition of the composite modifier significantly improves the adsorption effect of methylene blue and hexavalent chromium, removing methylene blue from water while also improving the removal effect of hexavalent chromium, reducing the cost of adsorbent preparation, and realizing the resource utilization of solid waste. This effectively solves the problems of coal gangue and other industrial solid waste accumulation and environmental pollution, providing favorable conditions for the high-value utilization of industrial solid waste and showing good application prospects.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] Coal gangue base polymer microspheres, comprising the following raw materials:

[0008] Solid powder: coal gangue, fly ash, and slag; wherein, the mass fraction of coal gangue in the solid powder is 25-50%; the mass fraction of fly ash is 25-50%; the mass fraction of slag is 25-50%; and the sum of the mass fractions of the three is 100%.

[0009] Alkali activator: water glass and sodium hydroxide, wherein the mass ratio of water glass to sodium hydroxide is 53-112:10; the mass ratio of water glass to solid powder is 3-5:10;

[0010] Foaming agent: hydrogen peroxide solution, wherein the mass ratio of hydrogen peroxide solution to solid powder is 0.6-0.8:100;

[0011] Modifiers: dodecyltrimethylammonium bromide (DTAB) and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline, wherein the mass ratio of dodecyltrimethylammonium bromide (DTAB) to solid powder is 1-30:100; and the mass ratio of 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline to solid powder is 1-30:100.

[0012] Furthermore, the mass percentages of each component in the coal gangue are as follows: SiO2: 60%-70%, Al2O3: 20%-30%, CaO: 0.1%-1%, K2O: 3%-4%, TiO2: 1%-2%; the mass percentages of each component in the fly ash are as follows: SiO2: 50%-60%, Al2O3: 35%-45%, CaO: 0.01%-0.1%, K2O: 1%-2%, TiO2: 2%-3%; and the mass percentages of each component in the slag are as follows: SiO2: 30%-40%, Al2O3: 10%-20%, CaO: 30%-40%, K2O: 0.1%-1%, TiO2: 1%-2%.

[0013] Furthermore, the coal gangue has a particle size of less than 0.075 mm and needs to be calcined at 600-800℃ for 4-6 hours before use; the fly ash has a particle size of less than 0.075 mm, and the slag has a particle size of less than 0.075 mm.

[0014] Furthermore, the water glass has a modulus of 1.2-1.8, a solid content of 34 wt%, and a Baumé degree of 40; the hydrogen peroxide solution has a concentration of 10 wt%-30 wt%.

[0015] The preparation method of coal gangue-based polymer microspheres includes the following steps:

[0016] Step S1: Mix coal gangue, fly ash, slag, dodecyltrimethylammonium bromide (DTAB) and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline in a certain proportion to obtain solid mixture A;

[0017] Step S2: Water glass and sodium hydroxide are mixed in a certain proportion, stirred until well mixed, and then allowed to stand to obtain an alkaline activator;

[0018] Step S3: Hydrogen peroxide solution, remove and seal for later use, to obtain the foaming agent;

[0019] Step S4: Add the solid mixture A obtained in step S1 to the alkali activator obtained in step S2; after mixing, mechanically stir to obtain a slurry B;

[0020] Step S5: Add the foaming agent obtained in step S3 to the mixed slurry B obtained in step S4, and then mechanically stir to obtain mixed slurry C.

[0021] Step S6: Vertically drop the mixed slurry C into a dimethyl silicone oil bath to disperse and shape it;

[0022] Step S7: Collect the formed microspheres by vacuum filtration and place them in a forced-air drying oven for curing and solidification;

[0023] Step S8: Place the cured microspheres into a muffle furnace and calcine them to remove excess dimethyl silicone oil.

[0024] Furthermore, the alkali activator is allowed to stand for 12-24 hours, the dimethyl silicone oil bath temperature is 70-85℃, the dispersion molding time is 10-20 minutes, the curing temperature in the forced-air drying oven is 60-80℃, the curing time is 0.5-1.0 hours, the calcination temperature is 250-350℃, and the calcination time is 2-3 hours.

[0025] The application method of coal gangue-based polymer microspheres in the adsorption of methylene blue and hexavalent chromium includes: mixing and stirring coal gangue-based polymer microspheres with wastewater;

[0026] The wastewater contains methylene blue solution and / or hexavalent chromium solution.

[0027] Furthermore, the stirring time is 100-120 min.

[0028] Furthermore, the concentration of methylene blue and / or hexavalent chromium in the wastewater is 10-200 mg / L, the pH value is 1.5-10, and the ultraviolet spectral peak value is 500-700 nm.

[0029] Furthermore, the dosage of the coal gangue-based polymer microspheres is 1.0-10 g / L, and the stirring rate is 800-1000 r / min.

[0030] The beneficial effects of this invention are as follows:

[0031] (1) By modifying and utilizing industrial waste coal gangue, fly ash and slag, geopolymer microspheres with spherical structure were successfully prepared and used for the adsorption of methylene blue and hexavalent chromium.

[0032] (2) The various solid powders and composite modifier components of the present invention have a synergistic effect, and the prepared geopolymer has a high pore area, which can provide more adsorption sites. At the same time, it can change the surface charge of the geopolymer, so that the geopolymer microspheres can significantly improve the adsorption effect of methylene blue and hexavalent chromium.

[0033] (3) By adopting a wide range of raw material sources and implementing green and environmentally friendly preparation processes, there is no CO2 emission, which reduces production costs and effectively solves the problems of industrial solid waste accumulation and environmental pollution, providing favorable conditions for the high-value-added utilization of industrial solid waste. Attached Figure Description

[0034] Figure 1 This is a SEM image of the geopolymer microspheres prepared in Example 1 of the present invention;

[0035] Figure 2This is a surface view of the geopolymer microspheres prepared in Example 1 of the present invention;

[0036] Figure 3 This is a surface view of the geopolymer microspheres prepared in Comparative Example 1 of the present invention. Detailed Implementation

[0037] The optimized embodiments of the present invention will now be described in more detail. While optimized embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art. The scope of protection of the present invention includes, but is not limited to, the following:

[0038] In the following examples, the mass percentages of the raw materials used in the geopolymer microspheres are as follows: coal gangue: fly ash: slag = 25-50%: 25-50%: 25-50%. Water glass is a commercially available chemical reagent with a modulus of 1.2-1.8, a solid content of 34 wt%, and a Baume degree of 40. The amount of water glass added is 30 wt%-50 wt% of the solid powder. The amount of sodium hydroxide added is 3.57 wt%-7.5 wt% of the solid powder. The hydrogen peroxide used is analytical grade with a percentage of 30%, and the amount added is 0.6 wt%-0.8 wt% of the solid powder. DTAB and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline used are commercially available chemical reagents, chemically pure, and added at a rate of 30 wt% of the solid powder. The dimethyl silicone oil bath temperature was 85℃, the dispersion molding time was 15min, the curing temperature in the forced-air drying oven was 80℃, the curing time was 1.0h, the calcination temperature was 300℃, and the calcination time was 2h.

[0039] The water used in the following examples is tap water.

[0040] In this embodiment of the invention, the concentration of wastewater (methylene blue and hexavalent chromium) was determined by measuring the absorption peak intensity at 664 nm and 544 nm using a UV spectrophotometer.

[0041] Example 1

[0042] The geopolymer microspheres of this embodiment include coal gangue, fly ash, slag, alkali activator, foaming agent, and modifier. The mass fractions of coal gangue and fly ash in the solid powder are 25% (25g) and 25% (25g), respectively, and the mass fraction of slag is 50% (50g). The mass fractions of DTAB and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline in the modifier are 15% (15g) and 15% (15g), respectively. The water glass modulus of the alkali activator is 1.4, and the amount added is 40wt% (40g) of the solid powder. The amount of sodium hydroxide added is 5.81wt% (5.81g) of the solid powder. The amount of hydrogen peroxide solution added as the foaming agent is 0.8wt% (0.8g) of the solid powder.

[0043] Coal gangue, fly ash, slag, dodecyltrimethylammonium bromide (DTAB), and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline were mixed evenly in the above proportions. Water glass, sodium hydroxide, and foaming agent were added in proportion, and the mixture was mechanically stirred evenly. The mixture was then poured into a syringe and vertically dripped into an 85°C dimethyl silicone oil bath to disperse and form microspheres for 15 minutes. The formed microspheres were collected by vacuum filtration, placed in a forced-air drying oven at 80°C for curing and solidification for 1.0 h, and then calcined in a muffle furnace at 300°C for 2 h.

[0044] Using a 50 mL, 100 mg / L, 25 °C wastewater solution (methylene blue or hexavalent chromium) as the target pollutant, 500 mg of geopolymer microspheres were weighed and added to the solution, stirred for 120 min, and detected using a UV spectrophotometer.

[0045] Example 2

[0046] The geopolymer microspheres of this embodiment include coal gangue, fly ash, slag, alkali activator, foaming agent, and modifier. The mass fractions of coal gangue and fly ash in the solid powder are 30% (30g) and 30% (30g) respectively, and the mass fraction of slag is 40% (40g). The mass fractions of DTAB and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline in the solid powder are 20% (20g) and 10% (10g) respectively. The water glass modulus of the alkali activator is 1.2, and the amount added is 40wt% (40g) of the solid powder. The amount of sodium hydroxide added is 7.5wt% (7.5g) of the solid powder. The amount of hydrogen peroxide solution added as the foaming agent is 0.6wt% (0.6g) of the solid powder.

[0047] Coal gangue, fly ash, slag, dodecyltrimethylammonium bromide (DTAB), and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline were mixed evenly in the above proportions. Water glass, sodium hydroxide, and foaming agent were added in proportion, and the mixture was mechanically stirred evenly. The mixture was then poured into a syringe and vertically dripped into an 85°C dimethyl silicone oil bath to disperse and form microspheres for 15 minutes. The formed microspheres were collected by vacuum filtration, placed in a forced-air drying oven at 80°C for curing and solidification for 1.0 h, and then calcined in a muffle furnace at 300°C for 2 h.

[0048] Using a 50ml, 100mg / L, 25℃ wastewater solution (methylene blue or hexavalent chromium) as the target pollutant, 500mg of geopolymer microspheres were weighed and added to the solution, stirred for 120min, and detected using a UV spectrophotometer.

[0049] Example 3

[0050] The geopolymer microspheres of this embodiment include coal gangue, fly ash, slag, alkali activator, foaming agent, and modifier. The mass fractions of coal gangue and fly ash in the solid powder are 35% (35g) and 35% (35g), respectively, and the mass fraction of slag is 30% (30g). The mass fractions of DTAB and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline in the solid powder are 15% (15g) and 15% (15g), respectively. The water glass modulus of the alkali activator is 1.2, and the amount added is 40wt% (40g) of the solid powder. The amount of sodium hydroxide added is 7.5wt% (7.5g) of the solid powder. The amount of hydrogen peroxide solution added as the foaming agent is 0.8wt% (0.8g) of the solid powder.

[0051] Coal gangue, fly ash, slag, dodecyltrimethylammonium bromide (DTAB), and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline were mixed evenly in the above proportions. Water glass, sodium hydroxide, and foaming agent were added in proportion, and the mixture was mechanically stirred evenly. The mixture was then poured into a syringe and vertically dripped into an 85°C dimethyl silicone oil bath to disperse and form microspheres for 15 minutes. The formed microspheres were collected by vacuum filtration, placed in a forced-air drying oven at 80°C for curing and solidification for 1.0 h, and then calcined in a muffle furnace at 300°C for 2 h.

[0052] Using a 50ml, 100mg / L, 25℃ wastewater solution (methylene blue or hexavalent chromium) as the target pollutant, 500mg of geopolymer microspheres were weighed and added to the solution, stirred for 120min, and detected using a UV spectrophotometer.

[0053] Example 4

[0054] The geopolymer microspheres of this embodiment include coal gangue, fly ash, slag, alkali activator, foaming agent, and modifier. The mass fractions of coal gangue and fly ash in the solid powder are 50% (50g) and 25% (25g), respectively, and the mass fraction of slag is 25% (25g). The mass fractions of DTAB and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline in the solid powder are 10% (10g) and 20% (20g), respectively. The water glass modulus of the alkali activator is 1.4, and the addition amount is 40wt% (40g) of the solid powder. The addition amount of sodium hydroxide is 5.81wt% (5.81g) of the solid powder. The addition amount of hydrogen peroxide solution as the foaming agent is 0.6wt% (0.6g) of the solid powder.

[0055] Coal gangue, fly ash, slag, dodecyltrimethylammonium bromide (DTAB), and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline were mixed evenly in the above proportions. Water glass, sodium hydroxide, and foaming agent were added in proportion, and the mixture was mechanically stirred evenly. The mixture was then poured into a syringe and vertically dripped into an 85°C dimethyl silicone oil bath to disperse and form microspheres for 15 minutes. The formed microspheres were collected by vacuum filtration, placed in a forced-air drying oven at 80°C for curing and solidification for 1.0 h, and then calcined in a muffle furnace at 300°C for 2 h.

[0056] Using a 50ml, 100mg / L, 25℃ wastewater solution (methylene blue or hexavalent chromium) as the target pollutant, 500mg of geopolymer microspheres were weighed and added to the solution, stirred for 120min, and detected using a UV spectrophotometer.

[0057] Example 5

[0058] The geopolymer microspheres of this embodiment include coal gangue, fly ash, slag, alkali activator, foaming agent, and modifier. The mass fractions of coal gangue and fly ash in the solid powder are 25% (25g) and 50% (50g), respectively, and the mass fraction of slag is 25% (25g). The mass fractions of DTAB and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline in the solid powder are 20% (20g) and 10% (10g), respectively. The water glass modulus of the alkali activator is 1.8, and the amount added is 40wt% (40g) of the solid powder. The amount of sodium hydroxide added is 3.57wt% (3.57g) of the solid powder. The amount of hydrogen peroxide solution added as the foaming agent is 0.8wt% (0.8g) of the solid powder.

[0059] Coal gangue, fly ash, slag, dodecyltrimethylammonium bromide (DTAB), and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline were mixed evenly in the above proportions. Water glass, sodium hydroxide, and foaming agent were added in proportion, and the mixture was mechanically stirred evenly. The mixture was then poured into a syringe and vertically dripped into an 85°C dimethyl silicone oil bath to disperse and form microspheres for 15 minutes. The formed microspheres were collected by vacuum filtration, placed in a forced-air drying oven at 80°C for curing and solidification for 1.0 h, and then calcined in a muffle furnace at 300°C for 2 h.

[0060] Using a 50ml, 100mg / L, 25℃ wastewater solution (methylene blue or hexavalent chromium) as the target pollutant, 500mg of geopolymer microspheres were weighed and added to the solution, stirred for 120min, and detected using a UV spectrophotometer.

[0061] Example 6

[0062] The geopolymer microspheres of this embodiment include coal gangue, fly ash, slag, alkali activator, foaming agent, and modifier. The mass fractions of coal gangue and fly ash in the solid powder are 40% (40g) and 30% (30g), respectively, and the mass fraction of slag is 30% (30g). The mass fractions of DTAB and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline in the solid powder are 15% (15g) and 15% (15g), respectively. The water glass modulus of the alkali activator is 1.8, and the amount added is 40wt% (40g) of the solid powder. The amount of sodium hydroxide added is 3.57wt% (3.57g) of the solid powder. The amount of hydrogen peroxide solution added as the foaming agent is 0.6wt% (0.6g) of the solid powder.

[0063] Coal gangue, fly ash, slag, dodecyltrimethylammonium bromide (DTAB), and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline were mixed evenly in the above proportions. Water glass, sodium hydroxide, and foaming agent were added in proportion, and the mixture was mechanically stirred evenly. The mixture was then poured into a syringe and vertically dripped into an 85°C dimethyl silicone oil bath to disperse and form microspheres for 15 minutes. The formed microspheres were collected by vacuum filtration, placed in a forced-air drying oven at 80°C for curing and solidification for 1.0 h, and then calcined in a muffle furnace at 300°C for 2 h.

[0064] Using a 50ml, 100mg / L, 25℃ wastewater solution (methylene blue or hexavalent chromium) as the target pollutant, 500mg of geopolymer microspheres were weighed and added to the solution, stirred for 120min, and detected using a UV spectrophotometer.

[0065] Example 7

[0066] The geopolymer microspheres of this embodiment include coal gangue, fly ash, slag, alkali activator, foaming agent, and modifier. The mass fractions of coal gangue and fly ash in the solid powder are 30% (30g) and 35% (35g), respectively, and the mass fraction of slag is 35% (35g). The mass fractions of DTAB and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline in the solid powder are 10% (10g) and 20% (20g), respectively. The water glass modulus of the alkali activator is 1.2, and the amount added is 40wt% (40g) of the solid powder. The amount of sodium hydroxide added is 7.5wt% (7.5g) of the solid powder. The amount of hydrogen peroxide solution added as the foaming agent is 0.8wt% (0.8g) of the solid powder.

[0067] Coal gangue, fly ash, slag, dodecyltrimethylammonium bromide (DTAB), and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline were mixed evenly in the above proportions. Water glass, sodium hydroxide, and foaming agent were added in proportion, and the mixture was mechanically stirred evenly. The mixture was then poured into a syringe and vertically dripped into an 85°C dimethyl silicone oil bath to disperse and form microspheres for 15 minutes. The formed microspheres were collected by vacuum filtration, placed in a forced-air drying oven at 80°C for curing and solidification for 1.0 h, and then calcined in a muffle furnace at 300°C for 2 h.

[0068] Using a 50ml, 100mg / L, 25℃ wastewater solution (methylene blue or hexavalent chromium) as the target pollutant, 500mg of geopolymer microspheres were weighed and added to the solution, stirred for 120min, and detected using a UV spectrophotometer.

[0069] The degradation effect of wastewater (methylene blue or hexavalent chromium) in Examples 1-7 was tested, and the results are shown in Table 1.

[0070] Table 1 shows the degradation effect of wastewater (methylene blue or hexavalent chromium) in the examples.

[0071]

[0072]

[0073] Based on Example 1, the following comparative example is set:

[0074] Comparative Example 1

[0075] The geopolymer microspheres in this comparative example comprise coal gangue, fly ash, slag, alkali activator, foaming agent, and modifier. The coal gangue content in the solid powder is 0% (0g), while the fly ash and slag content are 50% (50g) and 50% (50g) respectively. The DTAB and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline content in the modifier are 15% (15g) and 15% (15g) respectively. The water glass modulus in the alkali activator is 1.4, and the addition amount is 40wt% (40g) of the solid powder. The sodium hydroxide addition amount is 5.81wt% (5.81g) of the solid powder. The hydrogen peroxide solution in the foaming agent is 0.8wt% (0.8g) of the solid powder.

[0076] Fly ash, slag, dodecyltrimethylammonium bromide (DTAB), and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline were mixed evenly in the above proportions. Water glass, sodium hydroxide, and foaming agent were added in proportion, and the mixture was mechanically stirred evenly. The mixture was then poured into a syringe and vertically dripped into an 85°C dimethyl silicone oil bath to disperse and form microspheres for 15 minutes. The formed microspheres were collected by vacuum filtration and placed in a forced-air drying oven at 80°C for curing for 1.0 h. After curing, the microspheres were calcined in a muffle furnace at 300°C for 2 h.

[0077] Using a 50ml, 100mg / L, 25℃ wastewater solution (methylene blue or hexavalent chromium) as the target pollutant, 500mg of geopolymer microspheres were weighed and added to the solution, stirred for 120min, and detected using a UV spectrophotometer.

[0078] Comparative Example 2

[0079] The geopolymer microspheres in this comparative example include coal gangue, fly ash, slag, alkali activator, foaming agent, and modifier. The mass fraction of coal gangue in the solid powder is 50% (50g), and the mass fractions of fly ash and slag are 0% (0g) and 50% (50g), respectively. The mass fractions of DTAB and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline in the modifier are 15% (15g) and 15% (15g), respectively. The water glass modulus in the alkali activator is 1.4, and the amount added is 40wt% (40g) of the solid powder. The amount of sodium hydroxide added is 5.81wt% (5.81g) of the solid powder. The amount of hydrogen peroxide solution added in the foaming agent is 0.8wt% (0.8g) of the solid powder.

[0080] Coal gangue, slag, dodecyltrimethylammonium bromide (DTAB), and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline were mixed evenly in the above proportions. Water glass, sodium hydroxide, and foaming agent were added in proportion, and the mixture was mechanically stirred evenly. The mixture was then poured into a syringe and vertically dropped into an 85°C dimethyl silicone oil bath to disperse and form microspheres for 15 minutes. The formed microspheres were collected by vacuum filtration, placed in a forced-air drying oven at 80°C for curing and solidification for 1.0 h, and then calcined in a muffle furnace at 300°C for 2 h.

[0081] Using a 50ml, 100mg / L, 25℃ wastewater solution (methylene blue or hexavalent chromium) as the target pollutant, 500mg of geopolymer microspheres were weighed and added to the solution, stirred for 120min, and detected using a UV spectrophotometer.

[0082] Comparative Example 3

[0083] The geopolymer microspheres in this comparative example comprise coal gangue, fly ash, slag, alkali activator, foaming agent, and modifier. The coal gangue content in the solid powder is 50% (50g) by mass, while the fly ash and slag content are 50% (50g) and 0% (0g) respectively. The DTAB and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline content in the modifier are 15% (15g) and 15% (15g) respectively. The water glass modulus in the alkali activator is 1.4, and the addition amount is 40wt% (40g) of the solid powder. The sodium hydroxide addition amount is 5.81wt% (5.81g) of the solid powder. The hydrogen peroxide solution in the foaming agent is 0.8wt% (0.8g) of the solid powder.

[0084] Coal gangue, fly ash, dodecyltrimethylammonium bromide (DTAB), and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline were mixed evenly in the above proportions. Water glass, sodium hydroxide, and foaming agent were added in proportion, and the mixture was mechanically stirred evenly. The mixture was then poured into a syringe and vertically dropped into an 85°C dimethyl silicone oil bath to disperse and form microspheres for 15 minutes. The formed microspheres were collected by vacuum filtration, placed in a forced-air drying oven at 80°C for curing and solidification for 1.0 h, and then calcined in a muffle furnace at 300°C for 2 h.

[0085] Using a 50ml, 100mg / L, 25℃ wastewater solution (methylene blue or hexavalent chromium) as the target pollutant, 500mg of geopolymer microspheres were weighed and added to the solution, stirred for 120min, and detected using a UV spectrophotometer.

[0086] Comparative Example 4

[0087] The geopolymer microspheres in this comparative example comprise coal gangue, fly ash, slag, alkali activator, foaming agent, and modifier. The solid powder contains 25% (25g) coal gangue by mass, and fly ash and slag by mass fractions of 25% (25g) and 50% (50g), respectively. The modifier contains 30% (30g) DTAB and 0% (0g) 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline by mass fractions of 0.40% (40g) water glass by modulus of 1.4, and the amount added is 40wt% (40g) of the solid powder. The amount of sodium hydroxide added is 5.81wt% (5.81g) of the solid powder. The amount of hydrogen peroxide solution added in the foaming agent is 0.8wt% (0.8g) of the solid powder.

[0088] Coal gangue, fly ash, slag, and dodecyltrimethylammonium bromide (DTAB) were mixed evenly in the above proportions. Water glass, sodium hydroxide, and foaming agent were then added in the proportions. The mixture was mechanically stirred evenly and poured into a syringe. The mixture was then vertically dripped into an 85°C dimethyl silicone oil bath and dispersed for 15 minutes. The formed microspheres were collected by vacuum filtration and placed in a forced-air drying oven at 80°C for curing for 1.0 h. After curing, the microspheres were calcined in a muffle furnace at 300°C for 2 h.

[0089] Using a 50ml, 100mg / L, 25℃ wastewater solution (methylene blue or hexavalent chromium) as the target pollutant, 500mg of geopolymer microspheres were weighed and added to the solution, stirred for 120min, and detected using a UV spectrophotometer.

[0090] Comparative Example 5

[0091] The geopolymer microspheres in this comparative example comprise coal gangue, fly ash, slag, alkali activator, foaming agent, and modifier. The solid powder contains 25% (25g) coal gangue by mass, and fly ash and slag by mass of 25% (25g) and 50% (50g), respectively. The modifier contains 0% (0g) DTAB and 30% (30g) 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline by mass of ...

[0092] Coal gangue, fly ash, slag, and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline were mixed evenly in the above proportions. Water glass, sodium hydroxide, and foaming agent were added in proportion, and the mixture was mechanically stirred evenly. The mixture was then poured into a syringe and vertically dropped into an 85°C dimethyl silicone oil bath to disperse and form microspheres for 15 minutes. The formed microspheres were collected by vacuum filtration and placed in a forced-air drying oven at 80°C for curing and solidification for 1.0 h. After that, they were calcined in a muffle furnace at 300°C for 2 h.

[0093] Using a 50ml, 100mg / L, 25℃ wastewater solution (methylene blue or hexavalent chromium) as the target pollutant, 500mg of geopolymer microspheres were weighed and added to the solution, stirred for 120min, and detected using a UV spectrophotometer.

[0094] Comparative Example 6

[0095] The geopolymer microspheres in this comparative example comprise coal gangue, fly ash, slag, alkali activator, foaming agent, and modifier. The coal gangue content in the solid powder is 100% (100g), while the fly ash and slag content are 0% (0g) and 0% (0g), respectively. The DTAB and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline content in the modifier are 15% (15g) and 15% (15g), respectively. The water glass modulus in the alkali activator is 1.4, and the addition amount is 40wt% (40g) of the solid powder. The sodium hydroxide addition amount is 5.81wt% (5.81g) of the solid powder. The hydrogen peroxide solution in the foaming agent is 0.8wt% (0.8g) of the solid powder.

[0096] Coal gangue, dodecyltrimethylammonium bromide (DTAB), and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline were mixed evenly in the above proportions. Water glass, sodium hydroxide, and foaming agent were added in proportion, and the mixture was mechanically stirred evenly. The mixture was then poured into a syringe and vertically dropped into an 85°C dimethyl silicone oil bath to disperse and form microspheres for 15 minutes. The formed microspheres were collected by vacuum filtration, placed in a forced-air drying oven at 80°C for curing and solidification for 1.0 h, and then calcined in a muffle furnace at 300°C for 2 h.

[0097] Using a 50ml, 100mg / L, 25℃ wastewater solution (methylene blue or hexavalent chromium) as the target pollutant, 500mg of geopolymer microspheres were weighed and added to the solution, stirred for 120min, and detected using a UV spectrophotometer.

[0098] Comparative Example 7

[0099] The geopolymer microspheres in this comparative example include coal gangue, fly ash, slag, alkali activator, foaming agent, and modifier. The mass fraction of coal gangue in the solid powder is 0 (0 g), and the mass fractions of fly ash and slag are 100% (100 g) and 0 (0 g), respectively. The mass fractions of DTAB and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline in the modifier are 15% (15 g) and 15% (15 g), respectively. The water glass modulus in the alkali activator is 1.4, and the amount added is 40 wt% (40 g) of the solid powder. The amount of sodium hydroxide added is 5.81 wt% (5.81 g) of the solid powder. The amount of hydrogen peroxide solution added in the foaming agent is 0.8 wt% (0.8 g) of the solid powder.

[0100] Fly ash, dodecyltrimethylammonium bromide (DTAB), and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline were mixed evenly in the above proportions. Water glass, sodium hydroxide, and foaming agent were added in proportion, and the mixture was mechanically stirred evenly. The mixture was then poured into a syringe and vertically dropped into an 85°C dimethyl silicone oil bath to disperse and form microspheres for 15 minutes. The formed microspheres were collected by vacuum filtration, placed in a forced-air drying oven at 80°C for curing and solidification for 1.0 h, and then calcined in a muffle furnace at 300°C for 2 h.

[0101] Using a 50ml, 100mg / L, 25℃ wastewater solution (methylene blue or hexavalent chromium) as the target pollutant, 500mg of geopolymer microspheres were weighed and added to the solution, stirred for 120min, and detected using a UV spectrophotometer.

[0102] Comparative Example 8

[0103] The geopolymer microspheres in this comparative example comprise coal gangue, fly ash, slag, alkali activator, foaming agent, and modifier. The mass fraction of coal gangue in the solid powder is 0 (0 g), and the mass fractions of fly ash and slag are 0 (0 g) and 100% (100 g), respectively. The mass fractions of DTAB and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline in the modifier are 15% (15 g) and 15% (15 g), respectively. The water glass modulus in the alkali activator is 1.4, and the addition amount is 40 wt% (40 g) of the solid powder. The sodium hydroxide addition amount is 5.81 wt% (5.81 g) of the solid powder. The hydrogen peroxide solution in the foaming agent is 0.8 wt% (0.8 g) of the solid powder.

[0104] After mixing the slag, dodecyltrimethylammonium bromide (DTAB), and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline in the above proportions, water glass, sodium hydroxide, and foaming agent were added in proportion. The mixture was mechanically stirred and poured into a syringe. The mixture was then vertically dropped into an 85°C dimethyl silicone oil bath and dispersed for 15 minutes. The formed microspheres were collected by vacuum filtration and cured in a forced-air drying oven at 80°C for 1.0 h. After that, they were calcined in a muffle furnace at 300°C for 2 h.

[0105] Using a 50ml, 100mg / L, 25℃ wastewater solution (methylene blue or hexavalent chromium) as the target pollutant, 500mg of geopolymer microspheres were weighed and added to the solution, stirred for 120min, and detected using a UV spectrophotometer.

[0106] Comparative Example 9

[0107] The geopolymer microspheres in this comparative example include coal gangue, fly ash, slag, alkali activator, foaming agent, and modifier. The mass fraction of coal gangue in the solid powder is 0 (0 g), and the mass fractions of fly ash and slag are 50% (50 g) and 50% (50 g), respectively. The mass fractions of DTAB and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline in the modifier are 30% (30 g) and 0 (0 g), respectively. The water glass modulus in the alkali activator is 1.4, and the amount added is 40 wt% (40 g) of the solid powder. The amount of sodium hydroxide added is 5.81 wt% (5.81 g) of the solid powder. The amount of hydrogen peroxide solution added in the foaming agent is 0.8 wt% (0.8 g) of the solid powder.

[0108] After mixing fly ash, slag, and dodecyltrimethylammonium bromide (DTAB) in the above proportions, add water glass, sodium hydroxide, and foaming agent in the proportions, stir mechanically until uniform, pour into a syringe, and vertically drop into an 85°C dimethyl silicone oil bath to disperse and form microspheres for 15 minutes. Collect the formed microspheres by vacuum filtration, place them in a forced-air drying oven at 80°C for curing and solidification for 1.0 h, and then calcine them in a muffle furnace at 300°C for 2 h.

[0109] Using a 50ml, 100mg / L, 25℃ wastewater solution (methylene blue or hexavalent chromium) as the target pollutant, 500mg of geopolymer microspheres were weighed and added to the solution, stirred for 120min, and detected using a UV spectrophotometer.

[0110] Comparative Example 10

[0111] The geopolymer microspheres in this comparative example include coal gangue, fly ash, slag, alkali activator, foaming agent, and modifier. The mass fraction of coal gangue in the solid powder is 50% (50g), and the mass fractions of fly ash and slag are 0 (0g) and 50% (50g), respectively. The mass fractions of DTAB and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline in the modifier are 30% (30g) and 0 (0g), respectively. The water glass modulus of the alkali activator is 1.4, and the amount added is 40wt% (40g) of the solid powder. The amount of sodium hydroxide added is 5.81wt% (5.81g) of the solid powder. The amount of hydrogen peroxide solution added in the foaming agent is 0.8wt% (0.8g) of the solid powder.

[0112] After mixing coal gangue, slag, and dodecyltrimethylammonium bromide (DTAB) in the above proportions, water glass, sodium hydroxide, and foaming agent are added in the proportions. The mixture is mechanically stirred and poured into a syringe. It is then vertically dripped into an 85°C dimethyl silicone oil bath and dispersed for 15 minutes. The formed microspheres are collected by vacuum filtration and placed in a forced-air drying oven at 80°C for curing for 1.0 h. After curing, they are calcined in a muffle furnace at 300°C for 2 h.

[0113] Using a 50ml, 100mg / L, 25℃ wastewater solution (methylene blue or hexavalent chromium) as the target pollutant, 500mg of geopolymer microspheres were weighed and added to the solution, stirred for 120min, and detected using a UV spectrophotometer.

[0114] Comparative Example 11

[0115] The geopolymer microspheres in this comparative example comprise coal gangue, fly ash, slag, alkali activator, foaming agent, and modifier. The solid powder contains 50% (50g) coal gangue by mass, and fly ash and slag by mass fractions of 50% (50g) and 0% (0g), respectively. The modifier contains 30% (30g) DTAB and 0% (0g) 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline by mass fractions of DTAB and 0% (0g), respectively. The alkali activator contains water glass with a modulus of 1.4, added at 40wt% (40g) of the solid powder, and sodium hydroxide added at 5.81wt% (5.81g) of the solid powder. The foaming agent contains hydrogen peroxide solution added at 0.8wt% (0.8g) of the solid powder.

[0116] Coal gangue, fly ash, and dodecyltrimethylammonium bromide (DTAB) were mixed evenly according to the above proportions. Water glass, sodium hydroxide, and foaming agent were then added in proportion. The mixture was mechanically stirred evenly and poured into a syringe. The mixture was then vertically dripped into an 85°C dimethyl silicone oil bath and dispersed for 15 minutes. The formed microspheres were collected by vacuum filtration and placed in a forced-air drying oven at 80°C for curing for 1.0 h. After curing, the microspheres were calcined in a muffle furnace at 300°C for 2 h.

[0117] Using a 50ml, 100mg / L, 25℃ wastewater solution (methylene blue or hexavalent chromium) as the target pollutant, 500mg of geopolymer microspheres were weighed and added to the solution, stirred for 120min, and detected using a UV spectrophotometer.

[0118] Comparative Example 12

[0119] The geopolymer microspheres in this comparative example comprise coal gangue, fly ash, slag, alkali activator, foaming agent, and modifier. The coal gangue content in the solid powder is 0% (0g), while the fly ash and slag content are 50% (50g) and 50% (50g) respectively. The DTAB and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline content in the modifier are 0% (0g) and 30% (30g) respectively. The water glass modulus in the alkali activator is 1.4, and the addition amount is 40wt% (40g) of the solid powder. The sodium hydroxide addition amount is 5.81wt% (5.81g) of the solid powder. The hydrogen peroxide solution in the foaming agent is 0.8wt% (0.8g) of the solid powder.

[0120] After mixing fly ash, slag, and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline in the above proportions, water glass, sodium hydroxide, and foaming agent are added in proportion. The mixture is mechanically stirred and poured into a syringe, which is then vertically dropped into an 85°C dimethyl silicone oil bath to disperse and form microspheres for 15 minutes. The formed microspheres are collected by vacuum filtration and cured in a forced-air drying oven at 80°C for 1.0 h. After that, they are calcined in a muffle furnace at 300°C for 2 h.

[0121] Using a 50ml, 100mg / L, 25℃ wastewater solution (methylene blue or hexavalent chromium) as the target pollutant, 500mg of geopolymer microspheres were weighed and added to the solution, stirred for 120min, and detected using a UV spectrophotometer.

[0122] Comparative Example 13

[0123] The geopolymer microspheres in this comparative example comprise coal gangue, fly ash, slag, alkali activator, foaming agent, and modifier. The coal gangue content in the solid powder is 50% (50g) by mass, while the fly ash and slag content are 0% (0g) and 50% (50g) by mass, respectively. The DTAB and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline content in the modifier are 0% (0g) and 30% (30g) by mass, respectively. The water glass modulus in the alkali activator is 1.4, and the addition amount is 40wt% (40g) of the solid powder. The sodium hydroxide addition amount is 5.81wt% (5.81g) of the solid powder. The hydrogen peroxide solution in the foaming agent is 0.8wt% (0.8g) of the solid powder.

[0124] Coal gangue, slag, and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline were mixed evenly in the above proportions. Water glass, sodium hydroxide, and foaming agent were added in proportion, and the mixture was mechanically stirred evenly. The mixture was poured into a syringe and vertically dropped into an 85°C dimethyl silicone oil bath to disperse and form microspheres for 15 minutes. The formed microspheres were collected by vacuum filtration and placed in a forced-air drying oven at 80°C for curing and solidification for 1.0 h. After that, they were calcined in a muffle furnace at 300°C for 2 h.

[0125] Using a 50ml, 100mg / L, 25℃ wastewater solution (methylene blue or hexavalent chromium) as the target pollutant, 500mg of geopolymer microspheres were weighed and added to the solution, stirred for 120min, and detected using a UV spectrophotometer.

[0126] Comparative Example 14

[0127] The geopolymer microspheres in this comparative example comprise coal gangue, fly ash, slag, alkali activator, foaming agent, and modifier. The solid powder contains 50% (50g) coal gangue by mass, and fly ash and slag by mass fractions of 50% (50g) and 0% (0g), respectively. The modifiers DTAB and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline by mass fractions of 0% (0g) and 30% (30g), respectively. The alkali activator contains water glass with a modulus of 1.4, added at 40wt% (40g) of the solid powder, and sodium hydroxide added at 5.81wt% (5.81g). The foaming agent contains hydrogen peroxide solution added at 0.8wt% (0.8g) of the solid powder.

[0128] Coal gangue, fly ash, and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline were mixed evenly in the above proportions. Water glass, sodium hydroxide, and foaming agent were added in proportion, and the mixture was mechanically stirred evenly. The mixture was then poured into a syringe and vertically dropped into an 85°C dimethyl silicone oil bath to disperse and form microspheres for 15 minutes. The formed microspheres were collected by vacuum filtration and placed in a forced-air drying oven at 80°C for curing and solidification for 1.0 h. After that, they were calcined in a muffle furnace at 300°C for 2 h.

[0129] Using a 50ml, 100mg / L, 25℃ wastewater solution (methylene blue or hexavalent chromium) as the target pollutant, 500mg of geopolymer microspheres were weighed and added to the solution, stirred for 120min, and detected using a UV spectrophotometer.

[0130] Comparative Example 15

[0131] The geopolymer microspheres in this comparative example include coal gangue, fly ash, slag, alkali activator, foaming agent, and modifier. The mass fraction of coal gangue in the solid powder is 100% (100g), and the mass fractions of fly ash and slag are 0 (0g) and 0 (0g), respectively. The mass fractions of DTAB and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline in the modifier are 30% (30g) and 0 (0g), respectively. The water glass modulus of the alkali activator is 1.4, and the amount added is 40wt% (40g) of the solid powder. The amount of sodium hydroxide added is 5.81wt% (5.81g) of the solid powder. The amount of hydrogen peroxide solution added in the foaming agent is 0.8wt% (0.8g) of the solid powder.

[0132] After mixing coal gangue and dodecyltrimethylammonium bromide (DTAB) in the above proportions, water glass, sodium hydroxide, and foaming agent are added in the proportions. The mixture is mechanically stirred and poured into a syringe. It is then vertically dropped into an 85°C dimethyl silicone oil bath and dispersed for 15 minutes. The formed microspheres are collected by vacuum filtration and placed in a forced-air drying oven at 80°C for curing for 1.0 h. After that, they are calcined in a muffle furnace at 300°C for 2 h.

[0133] Using a 50ml, 100mg / L, 25℃ wastewater solution (methylene blue or hexavalent chromium) as the target pollutant, 500mg of geopolymer microspheres were weighed and added to the solution, stirred for 120min, and detected using a UV spectrophotometer.

[0134] The adsorption effects of organic compounds (methylene blue or hexavalent chromium) in Comparative Examples 1-15 were tested, and the results are shown in Table 2.

[0135] Table 2. Degradation effect of comparative wastewater (methylene blue or hexavalent chromium)

[0136]

[0137]

[0138]

[0139] like Figure 1 and Figure 2 As shown in Table 1, the geopolymer microspheres exhibit significant adsorption effects on methylene blue and hexavalent chromium. In particular, in Example 1, the removal rate of methylene blue reached 94.72%. This is attributed to the excellent pore structure of the geopolymer synergistically prepared from the three solid powders and the abundant hydroxyl structure on the surface of the geopolymer microspheres, which enables both pore adsorption and electrostatic adsorption of methylene blue. Simultaneously, the abundant hydroxyl groups on the surface of the geopolymer can react with the nitrogen element in methylene blue to form hydrogen bond structures. As shown in Table 1, the geopolymer microspheres modified with both DTAB and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline achieved a maximum removal rate of 95.66% for hexavalent chromium. This is because the composite modification with DTAB and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline imparts a positive charge to the geopolymer surface, which is beneficial for adsorbing hexavalent chromium present in aqueous solution in anionic form. The synergistic modification with DTAB and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline resulted in a maximum removal rate of over 95% for hexavalent chromium, demonstrating a highly significant effect. Therefore, according to the composition of this invention, geopolymer microspheres with a high pore area and excellent adsorption capacity for both anionic and cationic pollutants can be obtained.

[0140] like Figure 3 As shown in Table 2, the adsorption effect of methylene blue and hexavalent chromium is significantly reduced when any one or more components of the present invention are missing. The main reason is that without any one or more components of the solid powder of the present invention, it is impossible to obtain a geopolymer with excellent porous structure, which makes its ability to expose active sites not prominent, the charge modification sites also decrease sharply, and it is impossible to better synergistically change the surface charge of the geopolymer microspheres, resulting in a significant decrease in the adsorption effect of methylene blue and hexavalent chromium.

[0141] In summary, this invention discloses the preparation of coal gangue-based geopolymer microspheres and their application in adsorbing methylene blue and hexavalent chromium. These geopolymer microspheres are prepared by mixing coal gangue, fly ash, slag, alkali activator, foaming agent, and composite modifier. By modifying and utilizing industrial wastes such as coal gangue, fly ash, and slag, a geopolymer with a spherical structure is successfully prepared. The prepared geopolymer, through the synergistic effect between the three solid powders, possesses a high pore area and numerous depressions and grooves on its surface, providing more adsorption active sites. The addition of the composite modifier significantly improves the adsorption effect of methylene blue and hexavalent chromium, achieving the secondary utilization of waste resources. This invention effectively solves the problems of coal gangue and other industrial solid waste accumulation and environmental pollution, providing favorable conditions for the high-value utilization of industrial solid waste and showing promising application prospects.

[0142] The various embodiments of the present invention have now been described. The above description is exemplary and not exhaustive, nor is it limited to the described embodiments. Many modifications and variations will be included within the scope and spirit of the described embodiments by those skilled in the art without departing from the scope and spirit of the invention.

Claims

1. A method for preparing coal gangue-based polymer microspheres, characterized in that, The coal gangue-based polymer microspheres comprise the following raw materials: Solid powder: coal gangue, fly ash, and slag; wherein, the mass fraction of coal gangue in the solid powder is 25-50%; the mass fraction of fly ash is 25-50%; the mass fraction of slag is 25-50%; and the sum of the mass fractions of the three is 100%. Alkali activator: water glass and sodium hydroxide, wherein the mass ratio of water glass to sodium hydroxide is 53-112:10; the mass ratio of water glass to solid powder is 3-5:10; Foaming agent: hydrogen peroxide solution, wherein the mass ratio of hydrogen peroxide solution to solid powder is 0.6-0.8:100; Modifiers: dodecyltrimethylammonium bromide (DTAB) and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline, wherein the mass ratio of dodecyltrimethylammonium bromide (DTAB) to solid powder is 1-30:100; and the mass ratio of 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline to solid powder is 1-30:

100. The coal gangue has a particle size of less than 0.075 mm and needs to be calcined at 600-800 ℃ for 4-6 h before use; the fly ash has a particle size of less than 0.075 mm and the slag has a particle size of less than 0.075 mm. The preparation method of the coal gangue-based polymer microspheres includes the following steps: Step S1: Mix coal gangue, fly ash, slag, dodecyltrimethylammonium bromide (DTAB) and 2-undecyl-N-carboxymethyl-N-hydroxyethylimidazoline in a certain proportion to obtain solid mixture A; Step S2: Water glass and sodium hydroxide are mixed in a certain proportion, stirred until well mixed, and then allowed to stand to obtain an alkaline activator; Step S3: Hydrogen peroxide solution, remove and seal for later use, to obtain the foaming agent; Step S4: Add the solid mixture A obtained in step S1 to the alkali activator obtained in step S2; after mixing, mechanically stir to obtain a slurry B; Step S5: Add the foaming agent obtained in step S3 to the mixed slurry B obtained in step S4, and then mechanically stir to obtain mixed slurry C. Step S6: Vertically drop the mixed slurry C into a dimethyl silicone oil bath to disperse and shape it; Step S7: Collect the formed microspheres by vacuum filtration and place them in a forced-air drying oven for curing and solidification; Step S8: Place the cured microspheres into a muffle furnace and calcine them to remove excess dimethyl silicone oil; The dimethyl silicone oil bath temperature is 70-85 ℃, the dispersion molding time is 10-20 min, the curing temperature in the forced-air drying oven is 60-80 ℃, the curing time is 0.5-1.0 h, the calcination temperature is 250-350 ℃, and the calcination time is 2-3 h.

2. The method for preparing coal gangue-based polymer microspheres as described in claim 1, characterized in that, The mass percentages of each component in the coal gangue are as follows: SiO2: 60%-70%, Al2O3: 20%-30%, CaO: 0.1%-1%, K2O: 3%-4%, TiO2: 1%-2%; the mass percentages of each component in the fly ash are as follows: SiO2: 50%-60%, Al2O3: 35%-45%, CaO: 0.01%-0.1%, K2O: 1%-2%, TiO2: 2%-3%; the mass percentages of each component in the slag are as follows: SiO2: 30%-40%, Al2O3: 10%-20%, CaO: 30%-40%, K2O: 0.1%-1%, TiO2: 1%-2%.

3. The method for preparing coal gangue-based polymer microspheres as described in claim 1, characterized in that, The water glass has a modulus of 1.2-1.8, a solid content of 34 wt%, and a Baumé degree of 40; the hydrogen peroxide solution has a concentration of 10 wt%-30 wt%.

4. The application of coal gangue-based polymer microspheres prepared by the preparation method according to any one of claims 1-3 in the adsorption of methylene blue and hexavalent chromium, characterized in that, Coal gangue-based polymer microspheres are mixed and stirred with wastewater; the wastewater contains methylene blue solution and / or hexavalent chromium solution.

5. The application as described in claim 4, characterized in that, The stirring time is 100-120 min.

6. The application as described in claim 4, characterized in that, The concentration of methylene blue and / or hexavalent chromium in the wastewater is 10-200 mg / L, the pH value is 1.5-10, and the ultraviolet spectral peak is 500-700 nm.

7. The application as described in claim 4, characterized in that, The dosage of the coal gangue-based polymer microspheres is 1.0-10 g / L, and the stirring rate is 800-1000 r / min.

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