Graphene quantum dot-based method for solidification and stabilization of waste incineration fly ash

Abstract

The application discloses a garbage incineration fly ash solidification and stabilization treatment method based on graphene quantum dots, which comprises the following steps: step one: uniformly stirring cement and incineration fly ash to obtain a cement-fly ash mixture; step two: dissolving graphene quantum dots in mixed water, fully stirring to obtain a graphene quantum dot solution; and step three: adding the cement-fly ash mixture into the graphene quantum dot solution, uniformly stirring and hardening to obtain a solidification body. The garbage incineration fly ash solidification and stabilization treatment method based on graphene quantum dots has the characteristics of simple operation, low preparation cost, environmental protection and the like, can efficiently solidify / stabilize heavy metals in incineration fly ash, significantly reduces leaching toxicity and reduces environmental hazards; in addition, the cement-fly ash solidification body after maintenance has higher strength and meets the landfill requirements.

Description

Technical Field

[0001] This invention relates to the field of waste incineration technology, and in particular to a method for solidifying and stabilizing fly ash from waste incineration based on graphene quantum dots. Background Technology

[0002] Fly ash is produced during waste incineration, and it typically contains large amounts of heavy metals such as lead, cadmium, and zinc. Improper handling can cause serious pollution to the soil and groundwater. Currently, the main methods for solidifying and stabilizing heavy metals in fly ash include cement solidification, aggregate stabilization, melt solidification, and ceramsite firing.

[0003] Chinese patent CN115368077A discloses a method for solidifying heavy metals in fly ash. First, the fly ash after combustion is collected and pretreated by washing with water. Lime is then added and stirred evenly. Silicate is added to the cement to be used, and the stirred silicate cement is then mixed with the fly ash. The resulting cement is poured into a mold and dried to ensure thorough internal drying. While this method can improve the density and hardness of the fly ash cement to some extent, it still suffers from insufficient cement hydration. Over time, the heavy metals in the solidified cement can easily dissolve again.

[0004] Chinese patent CN114632284A discloses a chelating agent for solidifying heavy metals in fly ash. The components of the chelating agent, in the order they are mixed with the fly ash during treatment, include powder, water, a silane coupling agent, and a precursor dispersion. The powder includes a precipitating agent and an initiator. The precursor dispersion includes rubber powder, an organic solvent, and an unsaturated monomer. The initiator includes persulfate. After the components of this chelating agent are mixed with the fly ash in sequence, the heavy metal ions inside the fly ash are chelated and solidified, reducing the possibility of heavy metal leaching from the fly ash. However, the composition of the chelating agent is very complex, increasing the cost.

[0005] In summary, the above-mentioned methods for treating fly ash from waste incineration all suffer from problems such as high preparation costs, poor stability, and potential environmental pollution. Therefore, it is of great importance to develop an efficient and environmentally friendly method for solidifying fly ash from waste incineration. Summary of the Invention

[0006] The purpose of this invention is to provide a method for solidifying and stabilizing waste incineration fly ash based on graphene quantum dots, so as to solve the problems of high cost, poor stability and easy environmental pollution of the above-mentioned waste incineration fly ash treatment methods.

[0007] To achieve the above objectives, this invention provides a method for solidifying and stabilizing fly ash from waste incineration based on graphene quantum dots, comprising the following steps:

[0008] Step 1: Mix the cement and incineration fly ash evenly to obtain a cement-fly ash mixture;

[0009] Step 2: Dissolve graphene quantum dots in the mixing water and stir thoroughly to obtain a graphene quantum dot solution;

[0010] Step 3: Add cement-fly ash mixture to graphene quantum dot solution, stir evenly and harden to obtain solidified body.

[0011] Preferably, the mass ratio of cement to incineration fly ash in step one is 1:2 to 9.

[0012] Preferably, the amount of graphene quantum dots incorporated in step two is 0.01% to 1% of the cement mass.

[0013] Preferably, the liquid-to-solid ratio of the total mass of mixing water and cement-fly ash mixture in step two is 0.3 to 0.5.

[0014] Preferably, the preparation method of graphene quantum dots in step two includes the following steps:

[0015] Step S1: Disperse starch in water and stir to dissolve to obtain a starch solution;

[0016] Step S2: Pour the starch solution into an autoclave for hydrothermal reaction;

[0017] Step S3: After the reaction is complete, the supernatant is centrifuged to remove the precipitate, and the solution is then evaporated by rotary evaporation and dried to obtain graphene quantum dots.

[0018] Preferably, the mass ratio of starch to water in step S1 is 1:50 to 100.

[0019] Preferably, the hydrothermal reaction in step S2 is performed by heating at 180–200°C for 2–3 hours.

[0020] Therefore, the waste incineration fly ash solidification and stabilization treatment method based on graphene quantum dots with the above-mentioned structure has the following beneficial effects:

[0021] (1) In this invention, graphene quantum dots and cement are added to fly ash at the same time. During the cement hydration process, hydration products such as calcium silicate hydrate are generated, which encapsulate the heavy metals in fly ash. At the same time, calcium silicate hydrate adsorbs heavy metals through electrostatic forces and solidifies heavy metals through isomorphic substitution. Graphene quantum dots can promote the cement hydration process, promote the interaction between cement and fly ash, and strengthen the enrichment of heavy metals in fly ash.

[0022] (2) The graphene quantum dots added in this invention can not only promote cement hydration and solidify heavy metals, but also utilize the abundant oxygen-containing groups on their surface to chelate and adsorb heavy metals, thereby further solidifying heavy metals.

[0023] (3) The cement and graphene quantum dots in this invention simultaneously solidify the heavy metals in fly ash. The two work synergistically to solidify and stabilize the heavy metals in fly ash. This method is characterized by simple operation, low preparation cost, and environmental friendliness. It can efficiently solidify / stabilize heavy metals in incineration fly ash, significantly reduce leaching toxicity, and reduce environmental hazards. In addition, the cement-fly ash solidified body after curing has higher strength, meeting landfill requirements.

[0024] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0025] Figure 1 This is a TEM image of the graphene quantum dots prepared in Example 1;

[0026] Figure 2 This is the AFM image of the graphene quantum dots prepared in Example 1;

[0027] Figure 3 yes Figure 2 The height along the white line;

[0028] Figure 4 This is a Raman image of the graphene quantum dots prepared in Example 1;

[0029] Figure 5 This is the FTIR image of the graphene quantum dots prepared in Example 1;

[0030] Figure 6 The zinc leaching effect is shown in Example 2 and Comparative Examples 1-5 for the cured bodies.

[0031] Figure 7 The cadmium leaching effect is shown in Example 2 and Comparative Examples 1-5 for the cured bodies.

[0032] Figure 8 The lead leaching effect is shown in Example 2 and Comparative Examples 1-5 for the cured bodies. Detailed Implementation

[0033] The present invention will be further described below. It should be noted that this embodiment is based on the present technical solution and provides detailed implementation methods and specific operation processes, but the present invention is not limited to this embodiment.

[0034] Example 1

[0035] The preparation of graphene quantum dots by hydrothermal method includes the following steps:

[0036] Step S1: Disperse 0.4g of starch in 30mL of water and stir to dissolve to obtain a starch solution;

[0037] Step S2: Pour the starch solution into a Teflon-lined stainless steel high-pressure reactor and heat it in an oven at 190°C for 2.5 hours to carry out a hydrothermal reaction;

[0038] Step S3: After the reaction is complete, the supernatant is centrifuged to remove the precipitate, and the solution is then evaporated by rotary evaporation and dried to obtain graphene quantum dots.

[0039] The prepared graphene quantum dots were characterized by TEM, AFM, Raman spectroscopy, and FTIR, respectively. Figure 1 It can be seen that the average particle size of graphene quantum dots is 2.9 nm. Figure 2 and Figure 3 It can be seen that the thickness of graphene quantum dots is about 1 nm. Figure 4 It can be seen from this that graphene quantum dots have high crystallinity. Figure 5 It can be seen that graphene quantum dots contain oxygen-containing groups such as hydroxyl, carboxyl, and epoxy groups, which makes the fly ash curing effect better.

[0040] Example 2

[0041] A method for solidifying and stabilizing fly ash from waste incineration based on graphene quantum dots includes the following steps:

[0042] Step 1: Mix cement and incineration fly ash evenly to obtain a cement-fly ash mixture, wherein the amount of cement added is 20 wt% of the incineration fly ash;

[0043] Step 2: Dissolve graphene quantum dots in mixing water and stir thoroughly to obtain a graphene quantum dot solution. The amount of graphene quantum dots added is 0.1 wt% of cement, and the liquid-solid ratio of the total mass of mixing water and cement-fly ash mixture is 0.4.

[0044] Step 3: Add cement-fly ash mixture to graphene quantum dot solution, stir evenly and harden to obtain solidified body.

[0045] Comparative Example 1

[0046] The difference from Example 2 is that no graphene quantum dots were added, and the cement-fly ash mixture was directly mixed with mixing water to obtain a solidified body.

[0047] Comparative Example 2

[0048] The difference from Example 2 is that the raw material for preparing graphene quantum dots is citric acid.

[0049] Comparative Example 3

[0050] The difference from Example 2 is that the raw material for preparing graphene quantum dots is glucose.

[0051] Comparative Example 4

[0052] The difference from Example 2 is that the raw material for preparing graphene quantum dots is sucrose.

[0053] Comparative Example 5

[0054] The difference from Example 2 is that the raw material for preparing graphene quantum dots is cellulose.

[0055] Test case

[0056] After curing the solidified bodies of Examples 2 and Comparative Examples 1-5 for 28 days, heavy metal leaching was determined according to the "Solid Waste Leaching Toxicity Leaching Method - Sulfuric Acid and Nitric Acid Method" (HJ / T299-2007). The compressive strength of the cured bodies was determined according to the method specified in GB / T50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete". The test results are shown in Table 1.

[0057]

[0058] As shown in Table 1, compared to Comparative Example 1, the leaching of lead, cadmium, and zinc heavy metals in the cured body of Example 2 decreased by 71%, 83%, and 64%, respectively, and the leaching concentrations fully met the national standards. Furthermore, graphene quantum dots improved the compressive mechanical properties of the cement system by 25.6%. Due to differences in carbon sources and synthesis methods, graphene quantum dots exhibit significant differences in structural morphology. Comparative Examples 2–5 used different raw materials, and Table 1 shows that using different raw materials affects the surface groups and performance of the quantum dots. The heavy metal leaching and compressive strength of Comparative Examples 2–5 were significantly lower than those of Example 2. Figure 6-8 It can also be seen that the graphene quantum dots prepared using starch raw materials in Example 2 have the best curing and stabilization effect of zinc, cadmium and lead.

[0059] Therefore, the present invention adopts the above-mentioned graphene quantum dot-based solidification and stabilization treatment method for waste incineration fly ash. This method has the characteristics of simple operation, low preparation cost, and environmental protection. It can efficiently solidify / stabilize heavy metals in incineration fly ash, significantly reduce leaching toxicity, and reduce environmental hazards. In addition, the cement-fly ash solidified body after curing has higher strength and meets landfill requirements.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for solidifying and stabilizing fly ash from waste incineration based on graphene quantum dots, characterized in that: Includes the following steps: Step 1: Mix cement and incineration fly ash evenly to obtain a cement-fly ash mixture; the mass ratio of cement to incineration fly ash in Step 1 is 1:2 to 9. Step 2: Dissolve graphene quantum dots in mixing water and stir thoroughly to obtain a graphene quantum dot solution; the amount of graphene quantum dots added is 0.01% to 1% of the cement mass; the liquid-solid ratio of the total mass of mixing water and cement-fly ash mixture is 0.3 to 0.

5. Step 3: Add cement-fly ash mixture to graphene quantum dot solution, stir evenly and harden to obtain solidified body.

2. The method for solidifying and stabilizing fly ash from waste incineration based on graphene quantum dots according to claim 1, characterized in that: The preparation method of graphene quantum dots in step two includes the following steps: Step S1: Disperse starch in water and stir to dissolve to obtain a starch solution; Step S2: Pour the starch solution into an autoclave for hydrothermal reaction; Step S3: After the reaction is complete, the supernatant is centrifuged to remove the precipitate, and the solution is then evaporated by rotary evaporation and dried to obtain graphene quantum dots.

3. The method for solidifying and stabilizing fly ash from waste incineration based on graphene quantum dots according to claim 2, characterized in that: In step S1, the mass ratio of starch to water is 1:50 to 100.

4. The method for solidifying and stabilizing fly ash from waste incineration based on graphene quantum dots according to claim 2, characterized in that: The hydrothermal reaction in step S2 is performed by heating at 180–200°C for 2–3 hours.

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