Application of molybdenum sulfide intercalation modified fly ash-based layered bimetal hydroxide in adsorption of heavy metals in wastewater

Abstract

The invention discloses application of molybdenum sulfide intercalation modified fly ash-based layered double hydroxides in wastewater heavy metal adsorption. The fly ash-based layered double hydroxides are prepared by mixing washed fly ash with AlCl3 and hydrochloric acid and adding NaOH to adjust the pH value; on the basis, MoS < 2-> is coupled by a mechanochemical method to prepare a single-phase material molybdenum sulfide intercalation modified fly ash-based layered double-metal hydroxide. According to the method, the adsorption capacity of the LDHs prepared from the fly ash on heavy metals Pb < 2 + >, Ag < + >, Hg < 2 + > and Cu < 2 + > can be remarkably improved, meanwhile, heavy metal adsorption selectivity can be brought to LDHs materials, the selectivity is that Ag < + > is larger than Hg < 2 + >, Cu < 2 + > is larger than Pb < 2 + >, and the selectivity is larger than others, in addition, by adopting a mechanochemical method, precipitation of Mo can be remarkably reduced, the harmfulness of the materials is reduced, and meanwhile the cost, the energy consumption and the environmental harm are reduced.

Description

Cross-Reference to Related Applications

[0001] This application is based on the divisional application of the application number 202510087284.0, the application date is January 20, 2025, and the invention name is: a method for preparing fly ash-based layered double metal hydroxide by molybdenum sulfide intercalation modification. TECHNICAL FIELD

[0002] The application belongs to the field of environmental protection, and specifically relates to the application of fly ash-based layered double metal hydroxide modified by molybdenum sulfide intercalation in the adsorption of heavy metals in wastewater. BACKGROUND

[0003] At present, waste incineration fly ash is mainly disposed by landfill and cement kiln. However, with the continuous improvement of government policy, it is particularly important to improve the treatment and resource utilization capacity of fly ash. The traditional method has been difficult to meet the demand due to environmental risks and treatment capacity, and therefore more green resource utilization technologies with high added value and low cost need to be developed to effectively treat waste incineration fly ash. Layered double hydroxide (LDH) is an anionic clay material composed of a main layer structure, interlayer anions and water molecules. The most common synthesis method is to combine the coprecipitation method with the hydrothermal method. At present, LDHs are mainly used in the research fields of catalysts, adsorbents, flame retardants and corrosion inhibitors.

[0004] Preparation of layered double metal hydroxide from fly ash is a green resource utilization technology with high added value and low cost that can meet the needs. At present, layered double metal hydroxide has some applications in heavy metal adsorption, and the adsorption capacity of LDHs made of fly ash is not much different from that on the market. However, in some specific cases where single heavy metal needs to be adsorbed, LDHs lack selectivity, and therefore there is an urgent need to provide a modified fly ash-based layered double metal hydroxide with selective heavy metal adsorption on the market. SUMMARY

[0005] In order to solve at least one of the above problems, the application provides a method for preparing fly ash-based layered double metal hydroxide by molybdenum sulfide intercalation modification.

[0006] In order to achieve the above purpose, the application adopts the following technical means: The first aspect of the application provides a method for preparing fly ash-based layered double metal hydroxide by molybdenum sulfide intercalation modification, which comprises the following steps: S1, waste incineration fly ash is added into sodium hydroxide solution and soaked for 1-2 times, the liquid-solid ratio of sodium hydroxide solution to fly ash is (10-12) ml:1g; after solid-liquid separation, the solid is taken to obtain soaked fly ash; S2, the leaching fly ash solid, deionized water, hydrochloric acid solution and aluminum chloride are mixed, the mass ratio of the leaching fly ash solid and aluminum chloride is (5-20):1, the deionized water is added according to the liquid-solid ratio (10-14) ml:1 g, sodium hydroxide is used to adjust the pH to 11-13, and the mixture is obtained after fully stirring, the mixture is transferred to a temperature-controlled ball mill, and the solid-liquid mixture obtained after ball milling is subjected to centrifugation, water washing and drying to obtain a fly ash-based layered double hydroxide, denoted as CaAl-Cl-LDH; S3, ammonium tetrathiomolybdate is added to the fly ash-based layered double hydroxide obtained in S2, the mass ratio is (1.1-1.5):1, and deionized water is further added, and the mixture is subjected to temperature-controlled ball milling treatment. S4, the mixture in S3 is centrifuged, filtered, washed and dried to obtain a molybdenum sulfide intercalated modified fly ash-based layered double hydroxide, denoted as CaAl-MoS4-LDH.

[0007] In some embodiments of the present application, in step S1, the solid-liquid separation is suction filtration of the mixture through a 0.45 μm filter membrane.

[0008] In some embodiments of the present application, in step S1, the concentration of the sodium hydroxide solution is 0.5-1 mol / L.

[0009] In some embodiments of the present application, in step S1, the leaching method is: fully shaking for 6-8 h and standing for 22-24 h.

[0010] In some embodiments of the present application, in step S2, the concentration of the hydrochloric acid solution is 1-1.2 mol / L.

[0011] In some embodiments of the present application, in step S2, the rotation speed of the ball mill is 700-900 rpm, the ball-to-material ratio (4-7):1, the ball milling time is 4-6 h, and the ball milling temperature is controlled at 100-120℃.

[0012] In some embodiments of the present application, in step S3, the liquid-solid ratio of the deionized water to the mixture of the fly ash-based layered double hydroxide and ammonium tetrathiomolybdate is (8-12) ml:1 g.

[0013] In some embodiments of the present application, in step S3, the ball milling treatment conditions are: the ball-to-material ratio (8-10):1, the ball milling time is 6-8 h, the rotation speed is 400-500 rpm, and the ball milling temperature is controlled at 80-100℃.

[0014] In some embodiments of the present application, in step S4, the washing process is two water washings and one ethanol cleaning.

[0015] In some embodiments of the present application, the drying process in step S4 is at 80-105°C under nitrogen atmosphere.

[0016] The second aspect of the present application provides a molybdenum sulfide intercalated modified fly ash based layered double hydroxide prepared by the method of the first aspect.

[0017] The present application also provides the application of the molybdenum sulfide intercalated modified fly ash based layered double hydroxide prepared by the method of the first aspect in the adsorption of heavy metals in wastewater.

[0018] The application of the molybdenum sulfide intercalated modified fly ash based layered double hydroxide prepared by the method of the first aspect in the selective adsorption of heavy metals in wastewater.

[0019] In some embodiments of the present application, the selectively adsorbed heavy metals include Ag, Hg, Cu, Pb. In some embodiments of the present application, the selectively adsorbed heavy metals are preferably Ag, followed by Hg.

[0020] Advantages of the present application Compared with the prior art, the present application has the following advantages: (1) The present application utilizes the effective components in fly ash to synthesize fly ash based LDHs for adsorbing heavy metal ions in wastewater, achieving the purpose of waste treatment.

[0021] (2) The present application optimizes the structure of LDHs made of fly ash, generates LDHs with Cl - between the layers by using a temperature controllable ball milling process, and accelerates the spontaneous process of MoS4 2- replacing Cl - between the layers by using a temperature controllable ball milling process, inserts MoS4 2- between the layers of LDHs, achieves the purpose of increasing the heavy metal adsorption capacity of fly ash made LDHs, and brings about the adsorption selectivity of specific heavy metal ions, which can meet the adsorption of single heavy metal in specific conditions.

[0022] (3) The present application uses mechanochemical method to reduce energy consumption and shorten reaction time, and at the same time brings better adsorption performance of the material. The material made by using the performance of mechanochemical method is not easy to precipitate Mo element in the use process, which reduces the harm of the material itself. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The figure shows the electron microscope image of the LDHs obtained in Example 1 of the present application. DETAILED DESCRIPTION

[0024] The following examples are put forth so as to demonstrate preferred embodiments of the application. Those in the art will recognize that the examples set forth herein demonstrate techniques discovered by the inventor to function well in the practice of the application, and therefore can be considered to constitute preferred modes for its practice. However, one skilled in the art will appreciate that many modifications can be made to the specific embodiments described herein, and still be encompassed by the scope of the application, without parting from its spirit.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs, and the materials described herein will be referred to by the citation of the reference that first introduced such term or material into the art. In case of conflict between the citation in the specification and that of a document incorporated herein by reference, the document incorporated by reference will control. Those skilled in the art will appreciate that many of the techniques described herein can be performed by equivalents not specifically described herein. Such equivalents are considered to be within the scope of the application.

[0026] The technical solutions of the present application will be further described in detail below in conjunction with the specific embodiments.

[0027] A method for preparing fly ash-based layered double hydroxide by molybdenum sulfide intercalation modification, the process steps are as follows: S1, the waste incineration fly ash is added into a sodium hydroxide solution with a concentration of 0.5-1 mol / L and soaked for 1-2 times, the liquid-solid ratio of the sodium hydroxide solution to the fly ash is (10-12) ml:1 g; after being shaken fully for 6-8 h, the mixture is left to stand for 22-24 h, then filtered, and the solid is taken to obtain the soaked fly ash; S2, the soaked fly ash solid, deionized water, a hydrochloric acid solution with a concentration of 1-1.2 mol / L, and aluminum chloride are mixed, the mass ratio of the soaked fly ash solid to aluminum chloride is (5-20):1, deionized water is added according to a liquid-solid ratio of (10-14) ml:1 g, the pH is adjusted to 11-13 by sodium hydroxide, and the mixture is obtained after being stirred fully; the mixture is transferred to a ball mill tank, the temperature is controlled to 100-120℃, ball milling is performed, the rotation speed of the ball mill tank is 700-900 rpm, the ball-to-material ratio is (4-7):1, and the ball milling time is 4-6 h; the solid-liquid mixture obtained after ball milling is subjected to centrifugation, water washing, and drying to obtain a fly ash-based layered double hydroxide, which is denoted as CaAl-Cl-LDH; S3, ammonium tetrathiomolybdate is added into the fly ash-based layered double hydroxide obtained in S2 according to a mass ratio of (1.1-1.5):1, deionized water is added according to a liquid-solid ratio of (8-12) ml:1 g, and the temperature is controlled to 80-100℃, and then ball milling treatment is performed; the ball milling treatment conditions are as follows: the ball-to-material ratio is (8-10):1, the ball milling time is 6-8 h, and the rotation speed is 400-500 rpm; S4, centrifuging the mixed solution in S3, filtering, washing twice with water, and drying at 80-105 DEG C under nitrogen atmosphere to obtain a molybdenum sulfide intercalation modified fly ash based layered double hydroxide, denoted as: CaAl-MoS4-LDH.

[0028] The second aspect of the present application provides a molybdenum sulfide intercalation modified fly ash based layered double hydroxide prepared by the method of the first aspect.

[0029] The present application also provides the application of the molybdenum sulfide intercalation modified fly ash based layered double hydroxide prepared by the method of the first aspect in the adsorption of heavy metals in wastewater.

[0030] The application of the molybdenum sulfide intercalation modified fly ash based layered double hydroxide prepared by the method of the first aspect in the selective adsorption of heavy metals in wastewater.

[0031] In some embodiments of the present application, the selectively adsorbed heavy metals include Ag, Hg, Cu, Pb. In some embodiments of the present application, the selectively adsorbed heavy metals are preferably Ag, followed by Hg.

[0032] Example 1 A method for preparing a molybdenum sulfide intercalation modified fly ash based layered double hydroxide, comprising the following steps: S1: adding waste incineration fly ash into 1 mol / L NaOH solution, liquid-solid ratio is 10 ml:1 g, stirring for 6 h, and standing for 24 h; the obtained mixture is filtered through a 0.45 μm filter membrane to obtain a solid; S2: taking the fly ash treated in S1 and aluminum chloride according to a mass ratio of 10:1, adding 1 mol / L hydrochloric acid solution according to a liquid-solid ratio of 3 ml:1 g, supplementing with deionized water according to a liquid-solid ratio of 10 ml:1 g, adding 2M NaOH solution to adjust the pH to 12, transferring the mixture to a ball mill tank, setting the rotation speed to 900 rpm, and controlling the temperature at 110 DEG C, ball milling for 6 h, and then centrifuging and washing with water, and drying at 105 DEG C for 24 h to obtain a fly ash based layered double hydroxide, denoted as: CaAl-Cl-LDH; S3: adding the obtained fly ash based layered double hydroxide and ammonium tetrathiomolybdate into a ball mill tank according to a mass ratio of 1.2:1, adding deionized water according to a liquid-solid ratio of 8 ml:1 g, and performing mechanical chemical treatment under the conditions of a ball material ratio of 10:1 and a ball milling rotation speed of 400 rpm, ball milling for 6 h, and a ball milling temperature of 80 DEG C; S4: separating the solid phase at a centrifugal speed of 5500 rpm, washing with deionized water twice and ethanol once, and drying at 100 DEG C under nitrogen atmosphere for 12 h to obtain a molybdenum sulfide intercalation modified fly ash based layered double hydroxide.

[0033] Example 2 The preparation method steps are the same as Example 1, except that in step S2, 2M NaOH solution is added to adjust the pH to 13.

[0034] Example 3 The preparation method steps are the same as Example 1, except that in step S2, the mass ratio of fly ash to aluminum chloride is set to 15:1.

[0035] Example 4 The preparation method steps are the same as Example 1, except that in step S2, the mass ratio of fly ash to aluminum chloride is set to 20:1.

[0036] Example 5 The difference from Example 1 is that in step S2, the ball milling speed is set to 800 rpm.

[0037] Example 6 The difference from Example 1 is that in step S3, the ball milling speed is set to 500 rpm.

[0038] Example 7 The difference from Example 1 is that in step S2, the ball milling time is set to 4h.

[0039] Example 8 The difference from Example 1 is that in step S3, the ball milling time is set to 8h.

[0040] Example 9 The difference from Example 1 is that in step S2, the liquid-solid ratio is added in the proportion of 12ml:1g.

[0041] Example 10 The difference from Example 1 is that in step S3, the liquid-solid ratio is added in the proportion of 10ml:1g.

[0042] Comparative Example 1 The difference from Example 1 is that in step S2, 2M NaOH solution is added to adjust the pH to 10.

[0043] Comparative Example 2 The difference from Example 1 is that in step S2, the mass ratio of fly ash to aluminum chloride is set to 25:1.

[0044] Comparative Example 3 The difference from Example 1 is that in step S2, the ball milling speed is set to 500 rpm.

[0045] Comparative Example 4 The difference from Example 1 is that in step S3, the ball milling speed is set to 500 rpm.

[0046] Comparative Example 5 The difference from Example 1 is that the ball milling speed in step S3 is set to 900 rpm.

[0047] Comparative Example 6 The difference from Example 1 is that the ball milling time in step S2 is set to 2 h.

[0048] Comparative Example 7 The difference from Example 1 is that the ball milling temperature in step S2 is set to 80℃.

[0049] Comparative Example 8 The difference from Example 1 is that the ball milling temperature in step S3 is set to 120℃.

[0050] Comparative Example 9 The difference from Example 1 is that the liquid-solid ratio in step S3 is set to 5 ml: 1 g.

[0051] Comparative Example 10 The difference from Example 1 is that the mass ratio of fly ash-based layered double hydroxide and ammonium tetrathiomolybdate in step S3 is 2:1.

[0052] The molybdenum sulfide intercalation modified fly ash-based layered double hydroxide prepared in Examples 1 to 10 and Comparative Examples 1 to 9 was subjected to adsorption experiments, and the method was as follows: (1) 0.05 g of the above prepared molybdenum sulfide intercalation modified fly ash-based layered double hydroxide material was mixed with 100 ml of simulated liquid, and the initial concentration of silver nitrate, mercury nitrate, lead nitrate and copper nitrate in the four simulated liquids was 500 mg / L. The mixture was stirred at 400 rpm at room temperature 25℃ for 6h, and then centrifuged at 7000 rpm for 5 min to obtain supernatant and separated slurry. The supernatant was filtered through a 0.22 μm filter to obtain a filtrate, and the concentration of heavy metal ions in the liquid phase before and after adsorption was determined by ICP-OES.

[0053] The adsorption results of the materials prepared in the examples and comparative examples are shown in Table 1.

[0054] Table 1 Heavy metal adsorption results of the materials prepared in Examples 1-10 and Comparative Examples 1-10

[0055] The results show that the adsorption capacity of the product prepared by the preparation method of the present application under suitable conditions for Ag, Hg, Cu and Pb is significantly greater than that of the product prepared in the comparative examples. Among them, the unsuitable conditions affect the synthesis and structure optimization of LDHs in step S2, which leads to the replacement of Cl in the interlayer of MoS4 2- in step S3. -Forming LDHs intercalated MoS4 between layers 2- Failure, and thus greatly affect the fly ash LDHs heavy metal adsorption capacity.

[0056] The product completed step S2 in the example and the final product were tested for adsorption effect, and the results are shown in Table 2.

[0057] Table 2 MoS4 2- Adsorption effect of fly ash-based layered double hydroxide before and after intercalation modification

[0058] The results show that: waste incineration fly ash LDHs modified by MoS4 2- After intercalation modification, the adsorption capacity of heavy metals is significantly improved, and the improvement of silver ions is particularly obvious.

[0059] (2) 0.05 g of molybdenum sulfide intercalation modified fly ash-based layered double hydroxide material prepared in Example 1 and 100 ml of simulated liquid were mixed, the simulated liquid was silver nitrate, mercury nitrate, lead nitrate and copper nitrate, and the initial concentration was 500 mg / L, 400 rpm was shaken and stirred at room temperature 25℃ for 6h, 7000 rpm was centrifuged for 5min to obtain supernatant and separated slurry, and the supernatant was filtered through a 0.22μm filter to obtain a filtrate, and the concentration of heavy metal ions in the liquid phase before and after adsorption was determined by ICP-OES. The results are shown in Table 3.

[0060] Table 3 Adsorption effect of molybdenum sulfide intercalation modified fly ash-based layered double hydroxide prepared in Example 1

[0061] The results show that: waste incineration fly ash LDHs modified by MoS4 2- After intercalation modification, the adsorption of heavy metals has selectivity, and the selectivity is Ag + >Hg 2+ >Cu 2+ >Pb 2+ .

[0062] (3) 0.1 g of molybdenum sulfide intercalation modified fly ash-based layered double hydroxide material prepared in Example 1 and LDHs before ball milling in S3 step in the preparation process of Example 1 were respectively placed in 100 ml of water, and shaken and stirred at 400 rpm at room temperature 25℃ for 6h, and then filtered through a 0.45 um membrane, and the amount of Mo element released was analyzed by ion chromatography. The results are shown in Table 4.

[0063] Table 4 Comparison of Mo element release amount in LDHs before and after ball milling

[0064] The results show that the Mo release amount of the LDHs before ball milling is 1.94 times of the Mo release amount of the LDHs after ball milling, the Mo release amount of the modified LDHs material obtained after S3 ball milling is close to 1 times of the Mo release amount of the material before ball milling, and the Mo of the modified LDHs material obtained after S3 ball milling is more stable and is not easy to release, thereby reducing the harm of the material itself.

[0065] All documents mentioned in the present application are incorporated herein by reference as if each individual document were incorporated by reference. In addition, it is to be understood that the application can be carried out by specifically different embodiments and that each disclosed embodiment can be implemented with or without the corresponding benefits disclosed herein.

Claims

1. Use of molybdenum sulfide intercalated modified fly ash based layered double hydroxide in adsorption of heavy metals from wastewater, characterized in that, The heavy metal in the wastewater is one or more of Ag, Hg, Cu, and Pb. The preparation of the molybdenum sulfide intercalation modified fly ash based layered double hydroxide includes the following steps: S1, adding waste incineration fly ash into sodium hydroxide solution for 1-2 times of immersion washing, the liquid-solid ratio of sodium hydroxide solution to fly ash is (10-12) ml:1 g; after filtration, the solid is taken to obtain the immersion washed fly ash; S2, mixing the immersion washed fly ash solid, deionized water, hydrochloric acid solution and aluminum chloride, the mass ratio of immersion washed fly ash solid to aluminum chloride is (5-20):1, and the deionized water is added according to the liquid-solid ratio (10-14) ml:1 g; The pH is adjusted to 11-13 by sodium hydroxide, and the mixture is obtained after sufficient stirring, and then the mixture is transferred to a ball mill tank for temperature control ball milling, and the solid-liquid mixture obtained after ball milling is centrifuged, washed with water and dried to obtain a fly ash based layered double hydroxide; S3, adding ammonium tetrathiomolybdate to the fly ash based layered double hydroxide obtained in S2, the mass ratio is (1.1-1.5):1, and then adding deionized water for temperature control ball milling treatment; S4, centrifuging, filtering, washing and drying the mixture in S3 to obtain a molybdenum sulfide intercalation modified fly ash based layered double hydroxide. In step S2, the rotation speed of the ball mill tank is 700-900 rpm, the ball-to-material ratio is (4-7):1, the ball milling time is 4-6 h, and the ball milling temperature is controlled at 100-120℃; In step S3, the ball milling treatment conditions are: ball-to-material ratio (8-10):1, ball milling time 6-8 h, rotation speed 400-500 rpm, and ball milling temperature controlled at 80-100℃.

2. Use according to claim 1, characterized in that: In step S1, the concentration of sodium hydroxide solution is 0.5-1 mol / L.

3. Use according to claim 1, characterized in that: In step S1, the immersion washing method is: fully shaking for 6-8 h and standing for 22-24 h.

4. Use according to claim 1, characterized in that: In step S2, the concentration of hydrochloric acid solution is 1-1.2 mol / L.

5. The use according to claim 1, characterized in that: In step S3, the liquid-solid ratio of deionized water to the mixture of fly ash based layered double hydroxide and ammonium tetrathiomolybdate is (8-12) ml:1 g.

6. The use according to claim 1, characterized in that: In step S4, the washing process is water washing twice and ethanol washing once.

7. Use according to claim 1, characterized in that: In step S4, the drying process is under nitrogen atmosphere at 80-105℃.

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