Preparation method of layered double hydroxide based on waste incineration fly ash

Abstract

The application discloses a preparation method of layered double hydroxide based on waste incineration fly ash, and comprises the following steps: S1, waste incineration fly ash and leaching solution are added into a mixing container according to a liquid-solid ratio (3-15):1, and leaching is carried out after sufficient mixing, and then a filtrate is obtained after filtration; S2, an aluminum-containing reagent is added into the filtrate obtained in S1, so that the ratio of divalent cations to trivalent cations in the solution is (1.5-2.5):1, the pH range of the solution is adjusted to 10-12, and a mixed suspension is obtained after sufficient stirring; S3, the mixed suspension obtained in S2 is poured into a hydrothermal reaction kettle, and is aged and crystallized through hydrothermal reaction; and S4, the mixed solution after crystallization and aging in S3 is filtered, washed with water, and dried, so that the obtained solid is the layered double hydroxide. The method has the advantages of simple process, easy realization, low requirement on equipment, and universality, can be used for synergistic treatment of other aluminum-containing waste liquid, and the product can be used for heavy metal adsorption, so that the waste incineration fly ash can be fully utilized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of environmental chemistry and environmental engineering, and particularly relates to a preparation method of layered double hydroxides based on waste incineration fly ash. BACKGROUND

[0002] The waste incineration technology can effectively destroy organic toxic substances, greatly reduce the volume of waste, and recycle energy, and will become an important research and development direction of waste resource, harmless and volume reduction treatment technology in China.

[0003] The removal effect of combustible substances is good for domestic waste incineration, but the total amount of heavy metals does not change after incineration, and the waste incineration fly ash contains most of the heavy metals. The incineration fly ash is not a chemically inert substance, and contains a high concentration of Cd, Pb, Zn and Cr and other harmful heavy metal substances and salts that can be leached out by water. If not properly treated, it will pollute groundwater and the surrounding environment, and is a harmful substance.

[0004] Due to the presence of a certain amount of heavy metals and other toxic substances in the fly ash, the conventional disposal method consumes a large amount of resources and has certain environmental risks, and the harmless disposal and resource utilization of fly ash become a problem to be solved.

[0005] Before the treatment of fly ash, water washing or acid washing and other pretreatments are usually required, and a large amount of reagents containing calcium, aluminum, chlorine, heavy metals and the like will be produced after the treatment, which also need to be resource utilized and disposed. Therefore, it is an urgent problem to be solved to study a comprehensive disposal method for waste incineration fly ash.

[0006] Layered double hydroxides (LDHs), also known as hydrotalcite-like compounds, have a two-dimensional layered structure, and the basic structural unit is an octahedron. The center of the octahedron is a metal ion, and the six apexes are OH-. The octahedrons form a unit layer by sharing edges. Due to its unique molecular structure, LDHs have many ideal chemical and physical properties, such as high specific surface area, catalytic ability, anion exchange ability, adsorption, alkalinity, thermal stability, and tunable and flexible interlayer space.

[0007] The interlayer structure of LDHs, the exchangeability of anions, and the memory effect make them widely used in adsorption, catalysis, and flame retardant fields. However, the synthesis method of LDHs is generally complex, including coprecipitation, sol-gel method, ion exchange method, and calcination pillaring method. However, the general conditions are strict or the energy consumption is high, and large-scale production is not convenient or the cost is too high. Therefore, it is a waste utilization method to develop a method for synthesizing LDHs based on waste incineration fly ash. SUMMARY

[0008] In view of the existing technical problems, the present application aims to provide a waste incineration fly ash-based layered double hydroxide preparation method which is easy to implement and simple in process, and can achieve stable treatment of fly ash and simultaneously produce widely used layered double hydroxide (LDHs).

[0009] To achieve the object of the present application, the present application adopts the following technical solutions:

[0010] The first aspect of the present application is to provide a waste incineration fly ash-based layered double hydroxide preparation method, comprising the following steps:

[0011] S1, waste incineration fly ash and leaching solution are added into a mixing container in a liquid-solid ratio of (3-15):1, and leaching is carried out after sufficient mixing, and the filtrate is obtained after filtration;

[0012] S2, an aluminum-containing reagent is added to the filtrate obtained in S1, so that the ratio of divalent metal cations to trivalent metal cations in the solution is (1.5-2.5):1, the pH range of the solution is adjusted to 10-12, and a mixed suspension is obtained after sufficient stirring;

[0013] S3, the mixed suspension obtained in S2 is poured into a hydrothermal reaction kettle, and hydrothermal reaction is carried out at a temperature of 80-140℃ for 4-28h to allow it to age and crystallize; if the hydrothermal reaction time is too short and the temperature is too low, it may lead to insufficient crystallization, and the time process may also lead to a decrease in cleanliness; preferably, the hydrothermal reaction conditions are selected as follows: hydrothermal temperature 100℃, and hydrothermal time 24h.

[0014] S4, the mixed solution after aging and crystallization in S3 is filtered, washed and dried, and the obtained solid is the layered double hydroxide; the layered double hydroxide has sharp diffraction peaks near 2θ=10.5°, 11.3°, 22.7°, 23.4°, 31.1° and 38.9°.

[0015] The main layer of the layered double hydroxide is composed of two elements, and when there are multiple elements, a similar structure can also be formed; different fly ash components are mainly used, the divalent metal cation is Ca element, and the material prepared after adding trivalent metal cation aluminum source is mainly calcium aluminum layered double hydroxide; when other metal cations are contained in the fly ash leaching solution, layered composite metal oxide is formed, i.e., the layer contains multiple metal elements.

[0016] Further, the leaching solution is an acid solution with a concentration of 0-5mol / L, the acid solution is used to leach the elements in the fly ash, and a high acid concentration can extract more elements, but the corresponding consumed alkali when adjusting the pH will increase accordingly; preferably, the concentration of the acid solution is 5mol / L.

[0017] Further, the acid solution includes but is not limited to hydrochloric acid, nitric acid, acetic acid, citric acid, lactic acid.

[0018] Further, the aluminum-containing reagent includes but is not limited to sodium metaaluminate solution, aluminum chloride solution, aluminum hydroxide suspension, aluminum-containing waste liquid.

[0019] Further, the drying temperature in S4 is 50-105℃.

[0020] Advantages of the present application

[0021] Compared with the prior art, the present application has the following advantages: the process is simple, easy to prepare, and has low requirements for equipment, and is universal; the source of aluminum-containing reagent is wide, and the preparation method of layered double hydroxide based on waste incineration fly ash can be used for synergistic treatment with other aluminum-containing waste liquid; the fly ash residue after leaching can be used for other resourceization methods or continued leaching, and the leaching solution is used for preparing layered double hydroxide; the layered double hydroxide has sharp diffraction peaks near 2θ = 10.5°, 11.3°, 22.7°, 23.4°, 31.1°, 38.9°, and can realize full utilization of fly ash; after preparation of layered double hydroxide, due to the adsorption of layered double hydroxide, part of the heavy metals in the leaching solution can be solidified in LDHs, further, the adsorption effect of the prepared LDHs on heavy metals can replace the LDHs product prepared by pure reagent and can be used for adsorption of heavy metals in other cases, achieving full utilization of waste, generating huge economic benefits while meeting environmental protection requirements, and realizing resource recycling. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The process flow chart of Example 1 of the present application is shown;

[0023] Figure 2 The test result graph of scanning electron microscope of the product of Example 1 of the present application is shown;

[0024] Figure 3 The X-ray diffraction result graph of the product of Examples 1-3 of the present application is shown. DETAILED DESCRIPTION

[0025] In order to make the technical problems solved by the present application, technical solutions and advantages clearer, the present application will be further described in detail below in combination with examples.

[0026] Example 1

[0027] The present embodiment provides a preparation method of layered double hydroxide based on waste incineration fly ash, and the process flow chart is as shown in Figure 1 The specific steps are as follows:

[0028] S1. Dry the fly ash from the waste incineration and set it aside for later use. Take 100g of the dried fly ash and mix it with a 0.5M acetic acid solution at a water-ash ratio of 10:1. Stir for 2 hours at a speed of 700rpm to fully mix and extract the mixture. Filter the mixture and take the filtrate as the extract.

[0029] S2, add sodium aluminate to the extract obtained in S1 to make the calcium-aluminum molar ratio 2:1, and add NaOH solution until the pH stabilizes at around 11. After stirring thoroughly, a mixed suspension is obtained.

[0030] S3, pour the mixed suspension from S2 into a hydrothermal reactor and hydrotherm at 100℃ for 24 hours to obtain an aged crystalline suspension;

[0031] S4. The aged crystalline suspension from S3 is repeatedly washed, filtered, dried, ground, and passed through a 200-mesh sieve to obtain LDHs powder.

[0032] The LDHs material obtained through the above steps is approximately 20g of white solid powder.

[0033] Analysis and testing:

[0034] (1) Take a small amount of LDHs sample and observe its microstructure using a scanning electron microscope (SEM);

[0035] (2) The composition of the main crystalline phases was tested using X-ray diffraction (XRD).

[0036] (3) The elemental composition was tested using X-ray fluorescence spectroscopy (XRF).

[0037] Experimental results:

[0038] SEM results are as follows Figure 2 As shown, by Figure 2 As can be seen, LDHs have a typical hexagonal sheet-like stacked structure.

[0039] XRD results are as follows Figure 3 As shown in (a), by Figure 3 (a) It can be seen that relatively sharp peaks appear at 11.3°, 22.7°, 23.4°, 31.1°, 38.8°, 38.9°, etc., which are typical characteristic peaks of LDHs.

[0040] The XRF results are shown in Table 1. The main elements are calcium, aluminum, oxygen, sulfur, chlorine, sodium, etc.

[0041] Table 1 XRF Results

[0042]

[0043] Example 2

[0044] This embodiment provides a method for preparing layered bimetallic hydroxides based on waste incineration fly ash, and its process flow diagram is shown below. Figure 1 The specific steps are as follows:

[0045] S1. Dry the fly ash from the waste incineration and set it aside for later use. Take 100g of the dried fly ash and mix it with a 1M acetic acid solution at a water-ash ratio of 10:1. Stir for 2 hours at a speed of 700rpm to fully mix and extract the mixture. Filter the mixture and take the filtrate as the extract.

[0046] S2, add sodium aluminate to the extract obtained in S1 to make the calcium-aluminum molar ratio 3:1, and add NaOH solution until the pH stabilizes at around 12. After stirring thoroughly, a mixed suspension is obtained.

[0047] S3, pour the mixed suspension from S2 into a hydrothermal reactor and hydrotherm at 120°C for 8 hours to obtain an aged crystalline suspension;

[0048] S4. The aged crystalline suspension from S3 is repeatedly washed with water, filtered, dried, ground, and passed through a 200-mesh sieve to obtain LDHs powder.

[0049] The LDHs material obtained through the above steps is approximately 23g of white solid powder.

[0050] Analysis and testing:

[0051] The composition of the main crystalline phases was determined using X-ray diffraction (XRD).

[0052] XRD results are as follows Figure 3 As shown in (b), relatively sharp peaks appear at 10.6°, 11.3°, 22.7°, 23.4°, 31.1°, and 38.9°, which are typical characteristic peaks of LDHs.

[0053] Example 3

[0054] This embodiment provides a method for preparing layered bimetallic hydroxides based on waste incineration fly ash, and its process flow diagram is shown below. Figure 1 The specific steps are as follows:

[0055] S1. Dry the fly ash from the waste incineration and set it aside for later use. Take 100g of the dried fly ash and mix it with a 0.25M acetic acid solution at a water-ash ratio of 3:1. Stir for 2 hours at a speed of 700rpm to fully mix and extract the mixture. Filter the mixture and take the filtrate as the extract.

[0056] S2, add sodium aluminate to the extract obtained in S1 to make the calcium-aluminum molar ratio 4:1, and add NaOH solution until the pH stabilizes at around 10.5. After stirring thoroughly, a mixed suspension is obtained.

[0057] S3, pour the mixed suspension from S2 into a hydrothermal reactor and hydrotherm at 100°C for 16 hours to obtain an aged crystalline suspension.

[0058] S4. The aged crystalline suspension from S3 is repeatedly washed with water, filtered, dried, ground, and passed through a 200-mesh sieve to obtain LDHs powder.

[0059] The LDHs material obtained through the above steps is approximately 11g of white solid powder.

[0060] Analysis and testing:

[0061] The composition of the main crystalline phases was determined using X-ray diffraction (XRD).

[0062] XRD results are as follows Figure 3 As shown in (c), relatively sharp peaks appear at 10.5°, 11.3°, 22.7°, 23.4°, 31.1°, and 38.9°, which are typical characteristic peaks of LDHs.

[0063] Heavy metal adsorption experiments were conducted on the LDHs prepared in Examples 1, 2, and 3. The specific steps are as follows:

[0064] (1) Take 0.5g of the LDHs material prepared in the above steps into three conical flasks respectively. Add 1L of cadmium nitrate solution with a cadmium ion concentration of about 500ppm, 1L of copper nitrate solution with a copper ion concentration of about 200ppm, and 1L of lead nitrate solution with a lead ion concentration of about 200ppm to the conical flasks respectively. Use a shaker to shake at 200rpm at room temperature for 1h for adsorption.

[0065] (2) Take 100ml of the adsorbed liquid and filter it. Test the concentration of ions in the liquid before and after adsorption and calculate the total amount of heavy metal ions adsorbed by the corresponding LDHs.

[0066] The adsorption capacities of the LDHs prepared in this invention for different heavy metal ions are shown in Table 1.

[0067] Table 1. Adsorption capacity of LDHs heavy metals in this invention

[0068]

[0069] Example 4

[0070] This embodiment provides a method for preparing layered bimetallic hydroxides based on waste incineration fly ash, with the following specific steps:

[0071] S1. Dry the fly ash from the waste incineration and set it aside. Take 100g of the dried fly ash and mix it with pure water at a water-ash ratio of 10:1. Stir for 2 hours at a speed of 700rpm to fully mix and extract the mixture. Filter the mixture and take the filtrate as the extract.

[0072] S2, add sodium aluminate to the extract obtained in S1 to make the calcium-aluminum molar ratio 2:1, and add NaOH solution until the pH stabilizes at around 11. After stirring thoroughly, a mixed suspension is obtained.

[0073] S3, pour the mixed suspension from S2 into a hydrothermal reactor and hydrotherm at 100℃ for 24 hours to obtain an aged crystalline suspension;

[0074] S4. The aged crystalline suspension from S3 is repeatedly washed, filtered, dried, and ground to obtain LDHs powder.

[0075] S5. Take 0.5g of the LDHs material prepared in the above steps into three conical flasks respectively. Add 1L of cadmium nitrate solution with a cadmium ion concentration of about 500ppm, 1L of copper nitrate solution with a copper ion concentration of about 200ppm, and 1L of lead nitrate solution with a lead ion concentration of about 200ppm to the conical flasks respectively. Use a shaker to shake at 200rpm at room temperature for 1h for adsorption.

[0076] S6. Take 100ml of the adsorbed liquid and filter it. Test the concentration of ions in the liquid before and after adsorption. Calculate the total amount of heavy metal ions adsorbed by the corresponding LDHs.

[0077] Example 5

[0078] This embodiment provides a method for preparing layered bimetallic hydroxides based on waste incineration fly ash, with the following specific steps:

[0079] S1. Dry the fly ash from the waste incineration and set it aside for later use. Take 100g of the dried fly ash and mix it with 0.5M acetic acid at a water-ash ratio of 10:1. Stir for 2 hours at a speed of 700rpm to fully mix and extract the mixture. Filter the mixture and take the filtrate as the extract.

[0080] S2, add aluminum chloride to the extract obtained in S1 to make the calcium-aluminum molar ratio 2:1, and add NaOH solution until the pH stabilizes at around 11. After stirring thoroughly, a mixed suspension is obtained.

[0081] S3, pour the mixed suspension from S2 into a hydrothermal reactor and hydrotherm at 100℃ for 24 hours to obtain an aged crystalline suspension;

[0082] S4. The aged crystalline suspension from S3 is repeatedly washed, filtered, dried, and ground to obtain LDHs powder.

[0083] S5. Take 0.5g of the LDHs material prepared in the above steps into three conical flasks respectively. Add 1L of cadmium nitrate solution with a cadmium ion concentration of about 500ppm, 1L of copper nitrate solution with a copper ion concentration of about 200ppm, and 1L of lead nitrate solution with a lead ion concentration of about 200ppm to the conical flasks respectively. Use a shaker to shake at 200rpm at room temperature for 1h for adsorption.

[0084] S6. Take 100ml of the adsorbed liquid and filter it. Test the concentration of ions in the liquid before and after adsorption. Calculate the total amount of heavy metal ions adsorbed by the corresponding LDHs.

[0085] Example 6

[0086] This embodiment provides a method for preparing layered bimetallic hydroxides based on waste incineration fly ash, with the following specific steps:

[0087] S1. Dry the fly ash from the waste incineration and set it aside for later use. Take 100g of the dried fly ash and mix it with 0.5M acetic acid at a water-ash ratio of 10:1. Stir for 2 hours at a speed of 700rpm to fully mix and extract the mixture. Filter the mixture and take the filtrate as the extract.

[0088] S2, add aluminum nitrate to the extract obtained in S1 to make the calcium-aluminum molar ratio 2:1, and add NaOH solution until the pH stabilizes at around 11. After stirring thoroughly, a mixed suspension is obtained.

[0089] S3, pour the mixed suspension from S2 into a hydrothermal reactor and hydrotherm at 100℃ for 24 hours to obtain an aged crystalline suspension;

[0090] S4. The aged crystalline suspension from S3 is repeatedly washed, filtered, dried, and ground to obtain LDHs powder.

[0091] S5. Take 0.5g of the LDHs material prepared in the above steps into three conical flasks respectively. Add 1L of cadmium nitrate solution with a cadmium ion concentration of about 500ppm, 1L of copper nitrate solution with a copper ion concentration of about 200ppm, and 1L of lead nitrate solution with a lead ion concentration of about 200ppm to the conical flasks respectively. Use a shaker to shake at 200rpm at room temperature for 1h for adsorption.

[0092] S6. Take 100ml of the adsorbed liquid and filter it. Test the concentration of ions in the liquid before and after adsorption. Calculate the total amount of heavy metal ions adsorbed by the corresponding LDHs.

[0093] Example 7

[0094] This embodiment provides a method for preparing layered bimetallic hydroxides based on waste incineration fly ash, with the following specific steps:

[0095] S1. Dry the fly ash from the waste incineration and set it aside for later use. Take 100g of the dried fly ash and mix it with 0.5M acetic acid at a water-ash ratio of 10:1. Stir for 2 hours at a speed of 700rpm to fully mix and extract the mixture. Filter the mixture and take the filtrate as the extract.

[0096] S2, add aluminum ash extract to the extract obtained in S1 to make the calcium-aluminum molar ratio 2:1, and add NaOH solution until the pH stabilizes at around 11. After stirring thoroughly, a mixed suspension is obtained.

[0097] S3, pour the mixed suspension from S2 into a hydrothermal reactor and hydrotherm at 100℃ for 24 hours to obtain an aged crystalline suspension;

[0098] S4. The aged crystalline suspension from S3 is repeatedly washed, filtered, dried, and ground to obtain LDHs powder.

[0099] S5. Take 0.5g of the LDHs material prepared in the above steps into three conical flasks respectively. Add 1L of cadmium nitrate solution with a cadmium ion concentration of about 500ppm, 1L of copper nitrate solution with a copper ion concentration of about 200ppm, and 1L of lead nitrate solution with a lead ion concentration of about 200ppm to the conical flasks respectively. Use a shaker to shake at 200rpm at room temperature for 1h for adsorption.

[0100] S6. Take 100ml of the adsorbed liquid and filter it. Test the concentration of ions in the liquid before and after adsorption. Calculate the total amount of heavy metal ions adsorbed by the corresponding LDHs.

[0101] The cadmium ion adsorption capacity of LDHs prepared from different aluminum sources is shown in Table 2.

[0102] Table 2. Cadmium ion adsorption capacity of LDHs prepared from different aluminum sources

[0103]

[0104] The results showed that LDHs prepared using different aluminum sources all had the ability to adsorb heavy metals. Among them, LDHs prepared with aluminum nitrate had better adsorption effects on lead and copper, while LDHs prepared with sodium aluminate had better adsorption effects on cadmium.

[0105] Example 8

[0106] This embodiment provides a method for preparing layered bimetallic hydroxides based on waste incineration fly ash, with the following specific steps:

[0107] S1. Dry the fly ash from the waste incineration and set it aside for later use. Take 100g of the dried fly ash and mix it with 0.5M citric acid solution at a water-ash ratio of 10:1. Stir for 2 hours at a speed of 700rpm to fully mix and extract the mixture. Filter the mixture and take the filtrate as the extract.

[0108] S2, add sodium aluminate to the extract obtained in S1 to make the calcium-aluminum molar ratio 2:1, and add NaOH solution until the pH stabilizes at around 11. After stirring thoroughly, a mixed suspension is obtained.

[0109] S3, pour the mixed suspension from S2 into a hydrothermal reactor and hydrotherm at 100℃ for 24 hours to obtain an aged crystalline suspension;

[0110] S4. The aged crystalline suspension from S3 is repeatedly washed, filtered, dried, and ground to obtain LDHs powder.

[0111] S5. Take 0.5g of the LDHs material prepared in the above steps into three conical flasks respectively. Add 1L of cadmium nitrate solution with a cadmium ion concentration of about 500ppm, 1L of copper nitrate solution with a copper ion concentration of about 200ppm, and 1L of lead nitrate solution with a lead ion concentration of about 200ppm to the conical flasks respectively. Use a shaker to shake at 200rpm at room temperature for 1h for adsorption.

[0112] S6. Take 100ml of the adsorbed liquid and filter it. Test the concentration of ions in the liquid before and after adsorption. Calculate the total amount of heavy metal ions adsorbed by the corresponding LDHs.

[0113] Example 9

[0114] This embodiment provides a method for preparing layered bimetallic hydroxides based on waste incineration fly ash, with the following specific steps:

[0115] S1. Dry the fly ash from the waste incineration and set it aside for later use. Take 100g of the dried fly ash and mix it with 0.5M hydrochloric acid solution at a water-ash ratio of 10:1. Stir for 2 hours at a speed of 700rpm to fully mix and extract the mixture. Filter the mixture and take the filtrate as the extract.

[0116] S2, add sodium aluminate to the extract obtained in S1 to make the calcium-aluminum molar ratio 2:1, and add NaOH solution until the pH stabilizes at around 11. After stirring thoroughly, a mixed suspension is obtained.

[0117] S3, pour the mixed suspension from S2 into a hydrothermal reactor and hydrotherm at 100℃ for 24 hours to obtain an aged crystalline suspension;

[0118] S4. The aged crystalline suspension from S3 is repeatedly washed, filtered, dried, and ground to obtain LDHs powder.

[0119] S5. Take 0.5g of the LDHs material prepared in the above steps into three conical flasks respectively. Add 1L of cadmium nitrate solution with a cadmium ion concentration of about 500ppm, 1L of copper nitrate solution with a copper ion concentration of about 200ppm, and 1L of lead nitrate solution with a lead ion concentration of about 200ppm to the conical flasks respectively. Use a shaker to shake at 200rpm at room temperature for 1h for adsorption.

[0120] S6. Take 100ml of the adsorbed liquid and filter it. Test the concentration of ions in the liquid before and after adsorption. Calculate the total amount of heavy metal ions adsorbed by the corresponding LDHs.

[0121] Example 10

[0122] This embodiment provides a method for preparing layered bimetallic hydroxides based on waste incineration fly ash, with the following specific steps:

[0123] S1. Dry the fly ash from the waste incineration and set it aside for later use. Take 100g of the dried fly ash and mix it with 0.5M nitric acid solution at a water-ash ratio of 10:1. Stir for 2 hours at a speed of 700rpm to fully mix and extract the mixture. Filter the mixture and take the filtrate as the extract.

[0124] S2, add sodium aluminate to the extract obtained in S1 to make the calcium-aluminum molar ratio 2:1, and add NaOH solution until the pH stabilizes at around 11. After stirring thoroughly, a mixed suspension is obtained.

[0125] S3, pour the mixed suspension from S2 into a hydrothermal reactor and hydrotherm at 100℃ for 24 hours to obtain an aged crystalline suspension;

[0126] S4. The aged crystalline suspension from S3 is repeatedly washed, filtered, dried, and ground to obtain LDHs powder.

[0127] S5. Take 0.5g of the LDHs material prepared in the above steps into three conical flasks respectively. Add 1L of cadmium nitrate solution with a cadmium ion concentration of about 500ppm, 1L of copper nitrate solution with a copper ion concentration of about 200ppm, and 1L of lead nitrate solution with a lead ion concentration of about 200ppm to the conical flasks respectively. Use a shaker to shake at 200rpm at room temperature for 1h for adsorption.

[0128] S6. Take 100ml of the adsorbed liquid and filter it. Test the concentration of ions in the liquid before and after adsorption. Calculate the total amount of heavy metal ions adsorbed by the corresponding LDHs.

[0129] Example 11

[0130] This embodiment provides a method for preparing layered bimetallic hydroxides based on waste incineration fly ash, with the following specific steps:

[0131] S1. Dry the fly ash from the waste incineration and set it aside for later use. Take 100g of the dried fly ash and mix it with 0.5M lactic acid solution at a water-ash ratio of 10:1. Stir for 2 hours at a speed of 700rpm to fully mix and extract the mixture. Filter the mixture and take the filtrate as the extract.

[0132] S2, add sodium aluminate to the extract obtained in S1 to make the calcium-aluminum molar ratio 2:1, and add NaOH solution until the pH stabilizes at around 11. After stirring thoroughly, a mixed suspension is obtained.

[0133] S3, pour the mixed suspension from S2 into a hydrothermal reactor and hydrotherm at 100℃ for 24 hours to obtain an aged crystalline suspension;

[0134] S4. The aged crystalline suspension from S3 is repeatedly washed, filtered, dried, and ground to obtain LDHs powder.

[0135] S5. Take 0.5g of the LDHs material prepared in the above steps into three conical flasks respectively. Add 1L of cadmium nitrate solution with a cadmium ion concentration of about 500ppm, 1L of copper nitrate solution with a copper ion concentration of about 200ppm, and 1L of lead nitrate solution with a lead ion concentration of about 200ppm to the conical flasks respectively. Use a shaker to shake at 200rpm at room temperature for 1h for adsorption.

[0136] S6. Take 100ml of the adsorbed liquid and filter it. Test the concentration of ions in the liquid before and after adsorption. Calculate the total amount of heavy metal ions adsorbed by the corresponding LDHs.

[0137] The cadmium ion adsorption capacity of LDHs prepared with different extraction solutions is shown in Table 3.

[0138] Table 3. Heavy metal ion adsorption capacity of LDHs prepared from different extraction solutions

[0139]

[0140] The results showed that different leaching solutions could effectively extract the corresponding elements from fly ash to prepare LDHs. The LDHs prepared using fly ash leaching solutions all had good heavy metal adsorption effects. Compared with LDHs prepared using pure reagents, the adsorption capacity of LDHs was 775.5 mg / g for cadmium, 246.7 mg / g for copper, and 49.2 mg / g for lead. The adsorption effect on cadmium was comparable, the adsorption effect on copper was slightly weaker, and the adsorption effect on lead was better. The difference in the adsorption effect of LDHs prepared by different leaching solutions on heavy metals was due to the different anions in the different leaching solutions, resulting in different interlayer anions in the prepared LDHs.

[0141] Utilizing fly ash to prepare LDHs offers two advantages: firstly, it utilizes fly ash as a resource, reducing the costs associated with its solidification and landfill disposal; secondly, the prepared LDHs are used for heavy metal adsorption, reducing the consumption of pure reagents and generating significant economic benefits. Table 4 shows a detailed economic benefit analysis based on the production of 1 ton of LDHs.

[0142] Table 4. Economic Benefit Analysis Table

[0143]

[0144] In terms of total preparation cost, using fly ash to prepare LDHs can save 30% in economic costs.

[0145] In addition, if fly ash is not utilized but instead solidified and landfilled, the cost will be even higher. The cost of solidifying and landfilling 1 ton of fly ash is about 1,580 yuan, and the cost of landfilling 4 tons of fly ash is about 6,320 yuan. Moreover, there are no subsequent economic benefits from fly ash landfilling.

[0146] Taking the 1 ton of LDHs produced as an example, the adsorption of heavy metals using it is shown in Table 5.

[0147] Table 5. Heavy metal adsorption of 1t LDHs

[0148]

[0149] As can be seen from the table above, the LDHs consumed for treating the same amount of heavy metals are not significantly different, and fly ash-based LDHs are superior to LDHs prepared from pure reagents for lead adsorption.

[0150] Therefore, it is evident that utilizing the large amount of fly ash generated in daily life to prepare LDHs can generate significant economic benefits. Not only can fly ash be stabilized, but the process is also simple, easy to prepare, requires low equipment standards, and is universally applicable, making it suitable for widespread use.

[0151] All references to this invention are incorporated herein by reference. Furthermore, it should be understood that after reading the foregoing description of this invention, those skilled in the art can make various alterations or modifications to this invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. An application of layered bimetallic hydroxides based on waste incineration fly ash in heavy metal adsorption, characterized in that: The preparation method of layered bimetallic hydroxides includes the following steps: S1, add the waste incineration fly ash and leachate to the mixing container at a liquid-solid ratio of (3-15):1, mix and leach thoroughly, filter and take the filtrate; S2, add an aluminum-containing reagent to the filtrate obtained from S1 to make the ratio of divalent metal cations to trivalent metal cations in the solution (1.5-2.5):1, adjust the pH of the solution to 10-12, and stir thoroughly to obtain a mixed suspension; S3. Pour the mixed suspension obtained in S2 into a hydrothermal reactor and react it at a temperature of 80-140℃ for 4-28 hours to allow it to age and crystallize. S4. Filter the mixture after aging and crystallization in S3, wash with water, and dry. The solid obtained is the layered bimetallic hydroxide. The layered bimetallic hydroxide exhibits sharp diffraction peaks near 2θ = 10.5°, 11.3°, 22.7°, 23.4°, 31.1°, and 38.9°. The extract is an acid solution with a concentration of 0-5 mol / L; the acid solution includes hydrochloric acid, nitric acid, acetic acid, citric acid, and lactic acid. The aluminum-containing reagent includes aluminum-containing waste liquid; The adsorbed heavy metals include cadmium, copper, and lead.

2. The method for preparing layered bimetallic hydroxides based on waste incineration fly ash according to claim 1, characterized in that: The drying temperature in S4 is 50-105℃.

Images