A method for stabilizing fly ash heavy metals using natural extract

Abstract

The present application relates to the field of fly ash heavy metal stabilization, and relates to a method for stabilizing fly ash heavy metal using natural extract, comprising the following steps: mixing biomass tar generated by pyrolysis of seed plants with an organic solvent to obtain a mixed solution; drying seed plants, bryophytes and algae plants to constant weight, then mixing them with each other and with the obtained mixed solution to carry out a mixing reaction, and then filtering a liquid phase; taking the obtained liquid phase, extracting and concentrating, and then immersing fly ash in the concentrated solution and stirring to carry out heavy metal stabilization. Compared with the prior art, the present application has the advantages of good metal stabilization effect, green environmental protection and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fly ash heavy metal stabilization, in particular to a method for stabilizing fly ash heavy metals using natural extracts. BACKGROUND

[0002] With the rapid development of the world economy, urbanization and industrialization process intensifies, the production of household garbage is rising, compared with the traditional compost, landfill disposal method, waste incineration disposal technology gradually becomes more economic and environmental choice. But waste incineration will produce a large number of fly ash, fly ash contains a large number of heavy metals and dioxin substances, which are listed as hazardous waste, therefore, harmless resource disposal of fly ash has become an extremely important environmental problem. Generally, the common disposal method for heavy metal solidification and stabilization in fly ash is the traditional inorganic chemical agent and organic chelating agent, which has unstable heavy metal solidification effect and increases the demand for municipal waste disposal, therefore, from the perspective of environmental protection and resource conservation, it is of great significance and value to develop new green environmental protection heavy metal solidification and stabilization agent. SUMMARY

[0003] The purpose of the present application is to overcome the defects of the prior art and provide a method for stabilizing fly ash heavy metals using natural extracts, which is rich in functional group complexing sites, which is conducive to forming chelate structure with heavy metals in fly ash, and then fixing heavy metals deeply, so that this method can realize the solidification and stabilization of heavy metals in fly ash, and reduce the heavy metal content in fly ash leaching solution.

[0004] The purpose of the present application can be realized by the following technical scheme:

[0005] A method for stabilizing fly ash heavy metals using natural extracts, comprising the following steps:

[0006] S1: mixing biomass tar generated by pyrolysis of seed plants with organic solvent to obtain a mixed solution;

[0007] S2: drying seed plants, bryophytes and algae plants to constant weight, then mixing them with each other and mixing with the mixed solution obtained in S1, and then filtering the liquid phase;

[0008] S3: taking the liquid phase obtained by filtering in S2, extracting and concentrating, and then immersing fly ash in the concentrated solution and stirring to stabilize heavy metals.

[0009] Further, in step S1, the seed plants include one of corn stalks, wheat stalks and rice stalks; the organic solvent includes one of methanol, dimethylformamide and ethyl acetate.

[0010] Further, in step S1, the pyrolysis temperature of the seed plants is 430-460 DEG C.

[0011] Further, in step S1, the volume ratio of the biomass tar mixed with the organic solvent is (1-2):5.

[0012] Further, in step S2, the seed plants include one of corn stalks, wheat stalks, and rice stalks; the bryophytes include one of Funaria hygrometrica, Marchantia polymorpha, and Thuidium cymbifolium; and the algae include one of Cyanophyta, Chlorophyta, and Ulva pertusa.

[0013] Further, in step S2, the mass ratio of the seed plants, the bryophytes, and the algae mixed together is (1-3):0.6:0.8.

[0014] Further, in step S2, after the seed plants, the bryophytes, and the algae are mixed together, the liquid-solid ratio of the mixed solution obtained in S1 is 6:(1-3).

[0015] Further, in step S2, the reaction is performed by a solvothermal method at (80-130) DEG C for (3-5) hours.

[0016] Further, in step S3, the concentrated solution is mixed with the fly ash at a liquid-solid ratio of (8-10):1.

[0017] Further, in step S3, the impregnation is stirred for (30-60) minutes.

[0018] In the present application, the biomass tar generated by pyrolysis of seed plants is mixed with an organic solvent to extract the hydroxyl derivatives of benzene in the biomass tar, and the seed plants, the bryophytes, and the algae are mixed with the solvent to perform a solvothermal reaction, which can well concentrate the active ingredients in the plants, and thus the liquid phase obtained by the solvothermal reaction has a good solidification effect on the heavy metals in the fly ash.

[0019] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0020] (1) The present application provides a method for stabilizing heavy metals in fly ash using natural extracts, and after impregnation and stirring of the fly ash, the heavy metal content in the leaching solution of the fly ash is reduced by 90.72% compared with impregnation with deionized water, and after drying of the solidified and stabilized fly ash, the heavy metal content in the leaching solution is reduced by 95.37% compared with the original fly ash, so the natural extracts prepared by this method can effectively stabilize the heavy metals in the fly ash.

[0021] (2) Compared with the traditional heavy metal stabilizing solidifying agent, the heavy metal in the fly ash is stabilized by the method provided in the application, after being immersed by deionized water, the content of the heavy metal in the leaching solution is reduced by 84.79% (using the solidifying method provided in the application) from 74.56% (using the traditional heavy metal solidifying agent), which is increased by nearly 10%, and the effect is better than that of the traditional heavy metal solidifying agent. DETAILED DESCRIPTION

[0022] The application will be described in detail below with specific examples.

[0023] The following examples are implemented on the basis of the technical solutions of the application described above, and detailed implementation modes and specific operation processes are given, but the protection scope of the application is not limited to the following examples.

[0024] The following are more detailed implementation cases, which further illustrate the technical solutions of the application and the technical effects that can be obtained.

[0025] In the following examples, if there is no special description of raw materials or processing technology, it means that they are all conventional commercially available products or conventional processing technologies in the art.

[0026] Example 1

[0027] The present embodiment provides a method for stabilizing heavy metals in fly ash using natural extracts, comprising the following steps:

[0028] 1) Pyrolyze the seed plant (corn stalk) at 450℃ for 2 hours to produce biomass tar, and then mix the biomass tar with methanol at a volume ratio of 1:5;

[0029] 2) Dry the seed plant (corn stalk), the bryophyte (hederacea), and the algal plant (cyanophyta) to constant weight, and then mix them with each other at a mass ratio of 1:0.6:0.8, mix the mixed solution obtained in step 1) at a liquid-solid ratio of 6:1, and heat at 80℃ for 3 hours by using the solvothermal method;

[0030] 3) Take the liquid phase obtained by filtering the solvothermal product of step 2), add deionized water to extract and concentrate to 2 times the original concentration, and immerse and stir with fly ash at a liquid-solid ratio of 8:1 for 30 minutes.

[0031] Example 2

[0032] The present embodiment provides a method for stabilizing heavy metals in fly ash using natural extracts, comprising the following steps:

[0033] 1) Pyrolyze the seed plant (corn stalk) at 450℃ for 2 hours to produce biomass tar, and then mix the biomass tar with methanol at a volume ratio of 1:5;

[0034] 2) corn stalks, sphagnum, blue algae were dried to constant weight and mixed with each other, the mixing mass ratio was 2:0.6:0.8, the mixed solution obtained in step 1) was heated at 130℃ for 5 hours by solvothermal method at a liquid-solid ratio of 6:2;

[0035] 3) the liquid phase obtained by filtering the solvothermal product of step 2) was added with deionized water, extracted and concentrated to 2 times the original concentration, and then immersed and stirred with fly ash at a liquid-solid ratio of 10:1 for 60 minutes.

[0036] Example 3

[0037] The example provides a method for stabilizing heavy metals in fly ash using natural extracts, comprising the following steps:

[0038] 1) biomass tar produced by pyrolysis of corn stalks at 600℃ for 3 hours was mixed with methanol at a volume ratio of 2:5;

[0039] 2) corn stalks, sphagnum, blue algae were dried to constant weight and mixed with each other, the mixing mass ratio was 2:0.6:0.8, the mixed solution obtained in step 1) was heated at 100℃ for 5 hours by solvothermal method at a liquid-solid ratio of 6:2;

[0040] 3) the liquid phase obtained by filtering the solvothermal product of step 2) was added with deionized water, extracted and concentrated to 3 times the original concentration, and then immersed and stirred with fly ash at a liquid-solid ratio of 10:1 for 60 minutes.

[0041] Example 4

[0042] The example provides a method for stabilizing heavy metals in fly ash using natural extracts, comprising the following steps:

[0043] 1) biomass tar produced by pyrolysis of corn stalks at 600℃ for 3 hours was mixed with methanol at a volume ratio of 2:5;

[0044] 2) corn stalks, sphagnum, blue algae were dried to constant weight and mixed with each other, the mixing mass ratio was 3:0.6:0.8, the mixed solution obtained in step 1) was heated at 130℃ for 5 hours by solvothermal method at a liquid-solid ratio of 6:3;

[0045] 3) the liquid phase obtained by filtering the solvothermal product of step 2) was added with deionized water, extracted and concentrated to 3 times the original concentration, and then immersed and stirred with fly ash at a liquid-solid ratio of 10:1 for 60 minutes.

[0046] Comparative Example 1

[0047] Comparative Example 1 differs from Example 1 only in that the biomass tar produced by pyrolysis of corn stalks at 600℃ for 2 hours was mixed with methanol at a volume ratio of 1:5, and the other preparation methods and preparation conditions were consistent with those of Example 1.

[0048] Comparative Example 2

[0049] Comparative Example 2 differs from Example 1 only in that the biomass tar produced by pyrolysis of the corn stalks at 600°C for 2 hours is mixed with methanol in a volume ratio of 2:5, and the other preparation methods and preparation conditions are consistent with those of Example 1.

[0050] Comparative Example 3

[0051] Comparative Example 3 differs from Example 1 only in that the corn stalks, sphagnum moss, and blue-green algae are dried to a constant weight, and then mixed in a mass ratio of 3:0.6:0.8, and the liquid-solid ratio of the mixed solution obtained in step 1) is 6:3, and the other preparation methods and preparation conditions are consistent with those of Example 1.

[0052] Comparative Example 4

[0053] Comparative Example 4 differs from Example 1 only in that the corn stalks, sphagnum moss, and blue-green algae are subjected to solvothermal treatment at 130°C for 5 hours, and the other preparation methods and preparation conditions are consistent with those of Example 1.

[0054] Comparative Example 5

[0055] Comparative Example 5 differs from Example 1 only in that the liquid phase obtained by filtering the solvothermal product is extracted with deionized water to a concentration of 3 times the original concentration, and then impregnated with fly ash at a liquid-solid ratio of 10:1 and stirred for 60 minutes, and the other preparation methods and preparation conditions are consistent with those of Example 1.

[0056] Comparative Example 6

[0057] ADD (industrial grade, content 95%, produced by Qingdao Luchang Mining Auxiliary Co., Ltd.) is impregnated with fly ash at a liquid-solid ratio of 10:1 and stirred for 60 minutes.

[0058] Comparative Example 7

[0059] Sodium sulfide is impregnated with fly ash at a liquid-solid ratio of 10:1 and stirred for 60 minutes.

[0060] For Examples 1-4 and Comparative Examples 1-7, the reduction A in the mass concentration of heavy metals in the fly ash leachate after impregnating the fly ash with the natural extract prepared is determined, as compared to the mass concentration of heavy metals in the fly ash leachate after impregnating the fly ash with an equal amount of deionized water, and the reduction B in the mass concentration of heavy metals in the fly ash leachate after impregnating the fly ash with deionized water, after the natural extract obtained in Examples 1-4 is solidified and stabilized, is determined, as compared to the mass concentration of heavy metals in the fly ash leachate before solidification and stabilization. The determination results are shown in Table 1.

[0061] Table 1 A(％) B(％) Example 1 80.13 84.79 Example 2 80.46 85.35 Example 3 88.34 91.81 Example 4 90.72 95.37 Comparative Example 1 82.42 86.14 Comparative Example 2 84.33 88.14 Comparative Example 3 83.65 87.25 Comparative Example 4 83.13 86.93 Comparative Example 5 87.77 90.42 Comparative Example 6 73.34 75.55 Comparative Example 7 70.22 74.56

[0062] The changes of Cd, Pb and Zn, which are the components with high content in the original fly ash, are most significant after the fly ash is impregnated with the prepared natural extract. The mass concentrations of Cd, Pb and Zn in the fly ash leaching solution are reduced compared to the mass concentrations of Cd, Pb and Zn in the fly ash leaching solution impregnated with the same amount of deionized water. The determination results are shown in Table 2.

[0063]

[0064]

[0065] The mass concentrations of Cd, Pb and Zn in the leaching solution are reduced compared to the mass concentrations of Cd, Pb and Zn in the leaching solution of the original fly ash without solidification and stabilization after the fly ash solidified and stabilized by the method of Examples 1-4 and Comparative Examples 1-7 is impregnated with deionized water. The determination results are shown in Table 3.

[0066] Table 3 Cd (%) Pb (%) Zn (%) Example 1 84.55 83.97 83.56 Example 2 86.66 85.27 84.78 Example 3 93.46 92.58 92.74 Example 4 96.77 95.35 94.60 Comparative Example 1 86.17 85.34 85.94 Comparative Example 2 89.27 88.34 87.14 Comparative Example 3 87.11 88.54 88.12 Comparative Example 4 87.03 85.32 86.99 Comparative Example 5 91.29 91.66 90.47 Comparative Example 6 76.58 74.38 75.03 Comparative Example 7 75.67 73.24 73.46

[0067] As can be seen from the comparison of Examples 1-4 and Comparative Examples 1-5, the higher the pyrolysis temperature and the longer the pyrolysis time, the higher the volume ratio of the biomass tar produced by the pyrolysis of the seed plants to the organic solvent, which is more conducive to the extraction of the hydroxyl derivatives of benzene in the biomass tar, so that the active ingredients in the plants can be better concentrated during the autogenous heating of the mixed solvent of the seed plants, the bryophytes and the algae. The higher the mixing mass ratio of the seed plants and the smaller the liquid-solid ratio, the better the solidification effect of the liquid phase on the heavy metals in the fly ash. At the same time, the higher the concentration ratio of the extraction and concentration of the liquid phase obtained by the autogenous heating with deionized water, the better the solidification and stabilization of the heavy metals in the fly ash. Since the natural extract is rich in functional group complexing sites, it is conducive to the formation of chelate structure with the heavy metals in the fly ash, thereby deeply fixing the heavy metals. Therefore, after the fly ash is impregnated and stirred with the natural extract, the heavy metal content in the fly ash leaching solution can be reduced by more than 80% compared to the impregnation with deionized water, and the best effect can reach 90.72%. After the fly ash is solidified and stabilized by the natural extract, and then impregnated with deionized water, the heavy metal content in the leaching solution can be reduced by more than 84% compared to the original fly ash, and the best effect can reach 95.37%. As can be seen from Comparative Examples 6-7, the heavy metal solidification effect of the traditional organic chelating agent and inorganic chemical agent is far inferior to that of the natural extract, which shows that the natural extract prepared by this method can effectively stabilize the heavy metals in the fly ash.

[0068] The foregoing description of the embodiments has been presented for the purpose of illustration and description. It is not intended to be exhaustive or to limit the application to the precise form disclosed. Modifications and variations are possible in light of the above teachings or can be acquired from practice of the application. As well, the description is presented in the context of the preferred embodiments as a number of alternatives. It is not intended to limit the application to the precise form described.

Claims

1. A method for stabilizing fly ash heavy metals using natural extractives, characterized by, The method comprises the following steps: S1: mixing biomass tar generated by pyrolysis of seed plants with an organic solvent to obtain a mixed solution; the temperature of the pyrolysis of the seed plants is 400-650 DEG C; the volume ratio of the biomass tar to the organic solvent is (1-2):5; S2: mixing seed plants, bryophytes and algae plants after drying to constant weight with each other, and mixing with the mixed solution obtained in S1 to react, and then filtering to obtain a liquid phase; the mass ratio of the dry mixture of the seed plants, the bryophytes and the algae plants is (1-3):0.6:0.8; the liquid-solid ratio of the dry mixture of the seed plants, the bryophytes and the algae plants to the mixed solution obtained in S1 is 6:(1-3); S3: extracting and concentrating the liquid phase obtained by filtering in S2, and then immersing fly ash in the concentrated solution and stirring to stabilize heavy metals; The seed plants are selected from one of corn stalks, wheat stalks and rice stalks; the bryophytes are selected from one of Funaria hygrometrica, Marchantia polymorpha and Hypnum plumaeforme; and the algae plants are selected from one of Cyanophyta, Chlorophyta and Sargassum fusiforme.

2. The method for stabilizing fly ash heavy metals using natural extractives according to claim 1, characterized by, In step S1, the organic solvent is selected from one of methanol, dimethylformamide and ethyl acetate.

3. The method for stabilizing fly ash heavy metals using natural extractives according to claim 1, characterized by, In step S2, the reaction is performed by solvothermal method at (80-130) DEG C for (3-5) hours.

4. The method for stabilizing fly ash heavy metals using natural extractives according to claim 1, characterized by, In step S3, the concentrated solution and the fly ash are fed at a liquid-solid ratio of (8-10):

1.

5. The method for stabilizing fly ash heavy metals using natural extractives according to claim 1, characterized by, In step S3, the immersion and stirring are performed for (30-60) minutes.

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