A geopolymer-based composite microsphere, a preparation method thereof, and application thereof in treating mixed dye wastewater

Abstract

The invention discloses a geopolymer-based composite microsphere for treating mixed dye wastewater. First, an alkali activator is reacted with a geopolymer synthesis raw material such as metakaolin to generate a geopolymer precursor, which is then compounded with zinc oxide to generate a geopolymer-based composite precursor, and then the obtained geopolymer-based composite precursor is extruded into polyethylene glycol 200 to form the composite microsphere. The obtained geopolymer-based composite microsphere has high treatment efficiency for mixed dyes, simple application and recovery methods, and can be repeatedly applied; and the involved synthesis process is simple, the raw material cost is low, and it has strong industrial application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of functional materials, and in particular relates to a geopolymer-based composite microsphere, a preparation method thereof, and application thereof in treating mixed dye wastewater. Background Art

[0002] With the rapid development of industrial technology, the discharge of various sewage has also increased, resulting in the deterioration of water quality. Among them, dye wastewater has complex components and high concentrations of pollutants, which has caused great harm to the environment and human health. Therefore, it is necessary to develop a treatment method for dye wastewater.

[0003] Geopolymer is a new type of green and environmentally friendly material that has developed rapidly in recent years. The raw materials for preparing geopolymer include metakaolin, fly ash and industrial waste residue, etc., which have the advantages of low cost, energy saving and environmental protection. The structure of geopolymer is three-dimensional porous, similar to zeolite (porosity and chemistry), and can be used in related fields of wastewater treatment. Because geopolymer is negatively charged, it has a better treatment effect on cationic dyes. However, dyes include three types: cationic dyes, anionic dyes and non-ionic dyes. Therefore, a single geopolymer cannot treat anionic dyes and non-ionic dyes. Therefore, it is critical to prepare geopolymers that can treat mixed dye wastewater. For example, patent CN111320425 A discloses a fly ash geopolymer / g-C3N4 composite catalyst, the raw materials used include: 1000 parts of fly ash, 15 parts of urea, 6 parts of melamine, and 300 parts of alkaline activator; the preparation steps include: first, urea and melamine are placed in a crucible and calcined to obtain g-C3N4; the weighed fly ash, g-C3N4 and alkaline activator are placed in a pure slurry mixer, water is added, and mixing is formed into a slurry; solidification and molding, demolding; curing; removing the plastic film and placing it to obtain a composite gelling material; then the obtained composite gelling material is broken and passed through a 120-mesh sieve to obtain the composite catalyst. Although the obtained composite catalyst can treat mixed dye wastewater, there are several problems: first, the catalyst is a gel particle with a particle size of 0.125 mm, which is not easy to recycle, easily produces secondary pollution and is not easy to be continuously treated, limiting its large-scale application; second, a pore-forming agent is added to the composite catalyst during the preparation process, and the gelled particles need to be placed in a muffle furnace at 600°C for calcination for 2 hours. High-temperature calcination makes the preparation process of the composite catalyst complicated, places high requirements on equipment, and increases the preparation cost and energy consumption; third, the degradation rate of methyl orange and methylene blue by the catalyst is less than 80%. Summary of the invention

[0004] The purpose of the present invention is to provide a geopolymer-based composite microsphere and a preparation method thereof and an application in treating mixed dye wastewater in view of the deficiencies in the prior art; the microsphere can efficiently remove the composite dye in the wastewater, and the preparation method involved is simple, does not require high-temperature calcination, has low raw material cost, and is suitable for industrial large-scale production.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing geopolymer-based composite microspheres for treating mixed dye wastewater comprises the following steps:

[0007] 1) mixing the geopolymer synthesis raw material and the alkali activator, stirring, and obtaining a geopolymer precursor;

[0008] 2) adding zinc oxide powder to the obtained geopolymer precursor and continuing stirring to obtain a composite geopolymer precursor;

[0009] 3) The composite geopolymer precursor is extruded and injected into the liquid phase PEG-200, allowed to stand, washed, and solidified to obtain the geopolymer-based composite microspheres.

[0010] In the above scheme, the raw materials for synthesizing the geopolymer are one or more of metakaolin, fly ash, clay and slag.

[0011] Preferably, the geopolymer synthesis raw material is metakaolin, wherein the SiO2 content is 50-58wt%, and the Al2O3 content is 40-45wt%.

[0012] In the above scheme, the alkaline activator is prepared by using sodium silicate, NaOH and water in a mass ratio of 100:(18-24):(106-142).

[0013] In the above scheme, the preparation method of the alkaline activator comprises the following steps: mixing the weighed sodium silicate, NaOH and water evenly, and standing at 40-50° C. for 24-36 hours to obtain the alkaline activator.

[0014] In the above solution, the particle size of the zinc oxide powder is 5 to 10 μm.

[0015] In the above scheme, the mass ratio of the geopolymer synthesis raw material, the alkali activator and zinc oxide is (90-110):(247-294):(37-54).

[0016] In the above scheme, the stirring rate in step 1) is 600-900 r / min, and the time is 10-30 min; the stirring rate in step 2) is 600-900 r / min, and the time is 10-30 min.

[0017] In the above scheme, the extrusion injection step in step 3) is performed by a syringe or the like; the diameter of the composite polymer precursor injected is 0.3-0.6 mm; the needle tip diameter of the syringe is 0.3-0.6 mm.

[0018] In the above scheme, the standing time in PEG-200 is 20 to 30 minutes, the curing temperature in the oven is 60 to 80° C., and the curing time is 24 to 60 hours.

[0019] The geopolymer-based composite microspheres prepared according to the above scheme have a diameter of about 1 to 3 mm, are milky white, are relatively uniform in size, have micropores on the surface, are relatively hard in texture and are insoluble in water.

[0020] The geopolymer-based composite microspheres obtained according to the above scheme are applied to treat mixed dye wastewater, and the specific steps are as follows: adding the geopolymer-based composite microspheres to the mixed dye solution, performing photocatalytic treatment, and removing the dyes in the mixed dye wastewater.

[0021] In the above scheme, the chemical components and their concentrations in the mixed dye solution include: rhodamine B 1-5 mg / L, methylene blue 3-8 mg / L.

[0022] In the above scheme, the solid-liquid ratio of the geopolymer-based composite microspheres to the mixed dye wastewater is 0.3-0.4 g:100 mL.

[0023] Preferably, the photocatalytic treatment time is 90 to 120 minutes.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1) The present invention utilizes an alkaline activator to react with a geopolymer synthesis raw material such as metakaolin to generate a geopolymer precursor, which is then compounded with zinc oxide to generate a geopolymer-based composite precursor, and then the obtained geopolymer-based composite precursor is extruded into polyethylene glycol 200 to form the composite microspheres; the synthesis process involved is simple and easy to operate, and the zinc oxide powder used is micron-grade, PEG-200 can be reused, the raw material cost is low, and it has a strong industrial application prospect;

[0026] 2) The geopolymer-based composite microspheres of the present invention effectively combine geopolymer and micron-sized zinc oxide to achieve the purpose of simultaneously and efficiently treating multiple dyes; they are easy to use when treating mixed dyes in wastewater, have good fluidity and dispersibility, and are easy to recycle and reuse;

[0027] 3) The geopolymer-based composite microspheres obtained by the present invention have a small particle size and a high efficiency in treating dye wastewater; different types of mixed dyes including rhodamine B and methylene blue can be treated simultaneously, with a treatment rate of about 90%. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The morphology of the geopolymer-based composite microspheres obtained in Example 1;

[0029] Figure 2 This is the X-ray diffraction diagram of the geopolymer-based composite microspheres and metakaolin obtained in Example 1. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0031] In the following examples, the sodium silicate used is a commercially available agent, wherein the components and their mass percentages are Na2O·3.35SiO2 80wt%, H2O 20wt%.

[0032] The metakaolin used was provided by Dandong Tianci Flame Retardant Material Technology Co., Ltd., which contained 54wt% SiO2, 43wt% Al2O3 and other oxide impurities.

[0033] The zinc oxide powder used was provided by Sinopharm Chemical Reagent Co., Ltd. and had a particle size of 5 to 10 μm.

[0034] Example 1

[0035] A geopolymer-based composite microsphere for treating mixed dye wastewater, the preparation method of which comprises the following steps:

[0036] 1) Weigh 20 g of sodium silicate, 3.9 g of NaOH and 22.3 g of deionized water, mix them evenly and place them in an oven at 40° C. for 24 hours to obtain a transparent alkaline activator;

[0037] 2) Weigh 10.3 g of the above-mentioned alkaline activator and 4.4 g of metakaolin, mix the two in a stirrer at a stirrer speed of 900 r / min for 15 min, and the mixture obtained after mixing evenly is a geopolymer precursor;

[0038] 3) Weigh 1.6 g of zinc oxide powder and mix it with the geopolymer precursor in a stirrer, and continue stirring at a stirrer speed of 900 r / min for 15 min. The mixture obtained after mixing evenly is a composite geopolymer precursor;

[0039] 4) The obtained composite geopolymer precursor was poured into a syringe with a needle tip diameter of 0.5 mm, and then injected into the liquid phase PEG-200. After standing for 20 minutes, it was washed with acetone and placed in an oven at 80°C for curing for 48 hours to obtain geopolymer-based composite microspheres.

[0040] Figure 1 This is a morphology diagram of the geopolymer-based composite microspheres obtained in this example. It can be seen from the figure that the average diameter of the obtained microspheres is about 2 mm, the size is relatively uniform, there are micropores on the surface; and the texture is relatively hard and insoluble in water.

[0041] Figure 2 The X-ray diffraction diagram of the geopolymer-based composite microspheres and metakaolin obtained in this example shows that the amorphous peak of the geopolymer-based composite microspheres is significantly offset compared to the amorphous peak of metakaolin, confirming the formation of geopolymers. In addition, an obvious ZnO diffraction peak can be seen in the XRD diagram of the geopolymer-based composite microspheres, indicating that no chemical reaction occurs between the geopolymer raw material and ZnO during the preparation process.

[0042] Application Examples

[0043] The geopolymer-based composite microspheres obtained in this example are applied to treat mixed dye wastewater, and the specific steps include:

[0044] 1) Prepare a mixed dye solution containing 1 mg / L rhodamine B and 5 mg / L methylene blue;

[0045] 2) 0.35 g of the obtained geopolymer-based composite microspheres were added to 100 ml of the mixed dye solution for photocatalytic treatment. After 90 min of treatment, the mixed dyes in the wastewater were simultaneously treated.

[0046] The test shows that the geopolymer-based composite microspheres obtained in this embodiment have a good treatment effect on mixed dyes, and the treatment efficiency of mixed dyes is about 90%; and the obtained microspheres are easy to recycle and reuse, and are suitable for promotion and application.

[0047] Example 2

[0048] A geopolymer-based composite microsphere for treating mixed dye wastewater, the preparation method of which comprises the following steps:

[0049] 1) Weigh 20 g of sodium silicate, 3.9 g of NaOH and 27.5 g of deionized water, mix them evenly and place them in an oven at 40° C. for 24 hours to obtain a transparent alkaline activator;

[0050] 2) Weigh 10 g of the above-mentioned alkaline activator and 3.8 g of metakaolin, mix the two in a stirrer at a stirrer speed of 800 r / min for 20 min, and the mixture obtained after mixing evenly is the geopolymer precursor;

[0051] 3) Weigh 2.2 g of zinc oxide powder and mix it with the geopolymer precursor in a stirrer, continue stirring, the stirrer speed is 800 r / min, the stirring time is 20 min, and the mixture obtained after mixing evenly is the geopolymer-based composite precursor;

[0052] 4) Pour the geopolymer-based composite precursor into a 0.5 mm syringe, inject into the liquid phase PEG-200, let stand for 30 min, wash with acetone and put into a 75° C. oven for curing for 54 h to obtain geopolymer-based composite microspheres.

[0053] Application Examples

[0054] The geopolymer-based composite microspheres obtained in this example are applied to treat mixed dye wastewater, and the specific steps include:

[0055] 1) Prepare a mixed dye solution containing 1 mg / L rhodamine B and 5 mg / L methylene blue;

[0056] 2) 0.3 g of the obtained geopolymer-based composite microspheres was added to 100 ml of the mixed dye solution for photocatalytic treatment. After 120 min of treatment, the mixed dyes in the wastewater were simultaneously treated.

[0057] The test shows that the geopolymer-based composite microspheres obtained in this embodiment have a good treatment effect on the mixed dye.

[0058] Comparative Example

[0059] A geopolymer-based composite microsphere for treating mixed dye wastewater, the preparation method of which comprises the following steps:

[0060] 1) Weigh 20 g of sodium silicate, 3.9 g of NaOH and 22.3 g of deionized water, mix them evenly and place them in an oven at 40° C. for 24 hours to obtain a transparent alkaline activator;

[0061] 2) Weigh 10.3 g of the above-mentioned alkaline activator and 4.4 g of metakaolin, mix the two in a stirrer at a stirrer speed of 900 r / min for 15 min, and the mixture obtained after mixing evenly is a geopolymer precursor;

[0062] 3) Weigh 1.6 g of zinc oxide powder and mix it with the above geopolymer precursor in a stirrer, continue stirring, the stirrer speed is 900 r / min, the stirring time is 15 min, and the mixture obtained after mixing evenly is the geopolymer-based composite precursor;

[0063] 4) The geopolymer-based composite precursor was poured into a syringe with a needle tip diameter of 0.5 mm, and then injected into the liquid phase PEG-2000. After standing for 20 minutes, it was washed with acetone and placed in an oven at 80° C. for curing for 48 hours to obtain geopolymer-based composite microspheres.

[0064] The experiment found that the geopolymer-based composite microspheres obtained in this comparative example had a fast sedimentation rate during the injection of liquid phase PEG-2000, and it was difficult to obtain full microspheres during molding, and they were flat; in the subsequent treatment of mixed dye wastewater, they were easily broken during stirring and difficult to recycle.

[0065] Obviously, the above embodiments are merely examples for clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the protection scope of the invention.

Claims

1. A method for preparing geopolymer-based composite microspheres, characterized in that: The steps include: 1) Mixing the geopolymer synthesis raw materials and the alkaline activator, stirring, and obtaining a geopolymer precursor; 2) adding zinc oxide powder to the obtained geopolymer precursor and continuing stirring to obtain a composite geopolymer precursor; 3) extruding the obtained composite geopolymer precursor into the liquid phase PEG-200, standing, washing, and curing to obtain the geopolymer-based composite microspheres; The particle size of the zinc oxide powder is 5-10 μm; The standing time in PEG-200 was 20–30 min; The mass ratio of the geopolymer synthesis raw material, the alkaline activator and zinc oxide is (90-110):(247-294):(37-54); The geopolymer-based composite microspheres are used to treat mixed dye wastewater, wherein the dye wastewater includes rhodamine B and methylene blue; wherein the concentration of rhodamine B is 1-5 mg / L, and the concentration of methylene blue is 3-8 mg / L.

2. The preparation method according to claim 1, characterized in that: The geopolymer synthesis raw materials are one or more of metakaolin, fly ash, clay and slag.

3. The preparation method according to claim 1, characterized in that: The alkaline activator is prepared by using sodium silicate, NaOH and water in a mass ratio of 100:(18-24):(106-142).

4. The preparation method according to claim 3, characterized in that: The preparation method of the alkaline activator comprises the following steps: mixing weighed sodium silicate, NaOH and water evenly, and standing at 40-50° C. for 24-36 hours to obtain the alkaline activator.

5. The preparation method according to claim 1, characterized in that: The outlet diameter of the composite geopolymer precursor for extrusion injection in step 3) is 0.3-0.6 mm; the extrusion injection step adopts a syringe method.

6. Geopolymer-based composite microspheres prepared by the preparation method according to any one of claims 1 to 5, characterized in that: Its diameter is 1~3 mm.

7. The use of the geopolymer-based composite microspheres according to claim 6 in the field of mixed dye wastewater treatment, characterized in that: The dye wastewater comprises rhodamine B and methylene blue; wherein the concentration of rhodamine B is 1-5 mg / L, and the concentration of methylene blue is 3-8 mg / L.

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