Application of molybdenum sulfide intercalated modified fly ash-based layered double hydroxide in adsorption of heavy metals from wastewater

Abstract

The application discloses application of molybdenum sulfide intercalation modified fly ash based layered double hydroxide in adsorption of heavy metals in wastewater, and the fly ash based layered double hydroxide is prepared by mixing fly ash, AlCl3 and hydrochloric acid and adding NaOH to adjust pH; on the basis, a single-phase material, molybdenum sulfide intercalation modified fly ash based layered double hydroxide, is prepared by coupling a mechanochemical method. 2‑ The method can not only significantly improve the adsorption capacity of fly ash LDHs for heavy metals Pb 2+ , Ag + , Hg 2+ and Cu 2+ , but also bring selectivity of heavy metal adsorption to the LDHs material, and the selectivity is Ag + >Hg 2+ >Cu 2+ >Pb 2+ >other. In addition, the mechanochemical method can significantly reduce the precipitation of Mo, reduce the harmfulness of the material, reduce the cost, reduce the energy consumption and environmental hazards.

Description

[0001] Cross-references to related applications

[0002] This application is a divisional application based on application number 202510087284.0, filed on January 20, 2025, entitled "A method for preparing fly ash-based bimetallic hydroxide by molybdenum sulfide intercalation modification". Technical Field

[0003] This invention belongs to the field of environmental protection technology, specifically relating to the application of molybdenum sulfide intercalation modified fly ash-based bimetallic hydroxide in the adsorption of heavy metals in wastewater. Background Technology

[0004] Currently, fly ash from waste incineration is mainly disposed of through landfill and co-processing in cement kilns. However, with the continuous improvement of government policies, enhancing the treatment and resource utilization capacity of fly ash has become particularly important. Traditional methods are no longer sufficient to meet the demand due to environmental risks and processing volumes. Therefore, it is necessary to develop more high-value-added, low-cost green resource utilization technologies to effectively treat waste incineration fly ash. Layered hydrogen hydroxides (LDHs) are anionic clay materials composed of a main layer structure, interlayer anions, and water molecules. The most common synthesis method combines co-precipitation with hydrothermal methods. Currently, LDHs are mainly used in research on catalysts, adsorbents, flame retardants, and corrosion inhibitors.

[0005] The preparation of layered bimetallic hydroxides (LDHs) from fly ash is a green resource utilization technology that meets the needs, has high added value, and is low cost. Currently, layered bimetallic hydroxides have some applications in heavy metal adsorption, and the adsorption capacity of LDHs made from fly ash is not significantly different from that of commercially available LDHs. However, in certain specific situations requiring the adsorption of a single heavy metal, LDHs lack selectivity. Therefore, there is an urgent need in the market for a modified fly ash-based layered bimetallic hydroxide with selective heavy metal adsorption. Summary of the Invention

[0006] To address at least one of the aforementioned problems, the present invention provides a method for preparing fly ash-based bimetallic hydroxides by molybdenum sulfide intercalation modification.

[0007] To achieve the above objectives, the present invention employs the following technical means: The first aspect of the present invention provides a method for preparing fly ash-based bimetallic hydroxides by molybdenum sulfide intercalation modification, comprising the following steps: S1. Soak the fly ash from waste incineration in sodium hydroxide solution 1-2 times. The liquid-solid ratio of sodium hydroxide solution to fly ash is (10-12) ml: 1 g. After solid-liquid separation, take the solid to obtain the soaked fly ash. S2. Mix the solid fly ash, deionized water, hydrochloric acid solution and aluminum chloride. The mass ratio of solid fly ash to aluminum chloride is (5~20):1. Add deionized water at a liquid-to-solid ratio of (10~14) ml:1g. Adjust the pH to 11~13 with sodium hydroxide. After thorough stirring, the mixture is transferred to a ball mill jar and ball milled at a controlled temperature. Centrifuge, wash with water and dry the solid-liquid mixture obtained after ball milling to obtain a fly ash-based bimetallic hydroxide, denoted as: CaAl-Cl-LDH. S3. Add ammonium tetrathiomolybdate to the fly ash-based bimetallic hydroxide obtained in S2 at a mass ratio of (1.1~1.5):1, then add deionized water and perform temperature-controlled ball milling. S4. After centrifuging, filtering, washing and drying the mixture in S3, a molybdenum sulfide intercalation modified fly ash base layer double metal hydroxide is obtained, denoted as: CaAl-MoS4-LDH.

[0008] In some embodiments of the present invention, in step S1, solid-liquid separation is performed by filtering the mixture through a 0.45 μm filter membrane.

[0009] In some embodiments of the present invention, in step S1, the concentration of sodium hydroxide solution is 0.5~1 mol / L.

[0010] In some embodiments of the present invention, in step S1, the immersion method is: fully shake for 6-8 hours and let stand for 22-24 hours.

[0011] In some embodiments of the present invention, in step S2, the concentration of the hydrochloric acid solution is 1~1.2 mol / L.

[0012] In some embodiments of the present invention, in step S2, the ball mill jar speed is 700~900 rpm, the ball-to-material ratio is (4~7):1, the ball milling time is 4~6h, and the ball milling temperature is controlled at 100-120℃.

[0013] In some embodiments of the present invention, in step S3, the liquid-to-solid ratio of the mixture of deionized water and fly ash-based bimetallic hydroxide and ammonium tetrathiomolybdate is (8~12) ml: 1 g.

[0014] In some embodiments of the present invention, in step S3, the ball milling conditions are: ball-to-material ratio (8~10):1, ball milling time 6~8h, rotation speed 400~500rpm, and ball milling temperature controlled at 80-100℃.

[0015] In some embodiments of the present invention, in step S4, the washing process consists of two water washes followed by one ethanol wash.

[0016] In some embodiments of the present invention, in step S4, the drying process is carried out at 80~105°C under a nitrogen atmosphere.

[0017] A second aspect of the present invention provides a molybdenum sulfide intercalation modified fly ash-based bimetallic hydroxide prepared by the method described in the first aspect.

[0018] The present invention also provides the application of the molybdenum sulfide intercalation modified fly ash-based bimetallic hydroxide prepared by the method described in the first aspect in the adsorption of heavy metals in wastewater.

[0019] The application of the molybdenum sulfide intercalation modified fly ash-based bimetallic hydroxide prepared by the method described in the first aspect in the selective adsorption of heavy metals in wastewater.

[0020] In some embodiments of the present invention, the selectively adsorbed heavy metals include Ag, Hg, Cu, and Pb. In some embodiments of the present invention, Ag is preferred, followed by Hg.

[0021] Beneficial effects of the present invention Compared with the prior art, the present invention has the following beneficial effects: (1) This invention utilizes the effective components in fly ash to synthesize fly ash-based LDHs to adsorb heavy metal ions in wastewater, thereby achieving the purpose of treating waste with waste.

[0022] (2) In this invention, the structure of LDHs made from fly ash is optimized, and the interlayer band Cl is generated by a ball milling process with controllable temperature. - LDHs, and then accelerated spontaneous MoS4 by temperature-controlled ball milling process. 2- Replacement of interlayer Cl - The process involves inserting MoS4 between LDH layers. 2- This achieves the goal of increasing the heavy metal adsorption capacity of fly ash-based LDHs, while also bringing adsorption selectivity for specific heavy metal cations, which can meet the adsorption requirements of a single heavy metal under specific conditions.

[0023] (3) The present invention uses mechanochemical method to reduce energy consumption and shorten reaction time while bringing better material adsorption performance. The material made by using the performance of mechanochemical method is less likely to precipitate Mo element during use, which reduces the harm of the material itself. Attached Figure Description

[0024] Figure 1 An electron microscope image of the LDHs obtained in Embodiment 1 of the present invention is shown. Detailed Implementation

[0025] The following examples are used to illustrate preferred embodiments of the invention. Those skilled in the art will understand that the techniques disclosed in the examples represent techniques discovered by the inventors that can be used to implement the invention, and therefore can be considered preferred embodiments for implementing the invention. However, those skilled in the art should understand from this specification that many modifications can be made to the specific embodiments disclosed herein, still yielding the same or similar results, without departing from the spirit or scope of the invention.

[0026] 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 invention pertains, and all materials disclosed herein and cited therein are incorporated herein by reference. Many equivalent techniques of specific embodiments of the invention described herein will be recognized or can be understood by ordinary experimentation by those skilled in the art. These equivalents will be included in the claims.

[0027] The technical solution of this application will be further described in detail below with reference to specific embodiments.

[0028] A method for preparing fly ash-based bimetallic hydroxides by molybdenum sulfide intercalation modification includes the following steps: S1. Add the fly ash from waste incineration to a sodium hydroxide solution with a concentration of 0.5~1mol / L and wash it 1~2 times. The liquid-solid ratio of the sodium hydroxide solution to the fly ash is (10~12)ml:1g. Shake it thoroughly for 6~8h, let it stand for 22~24h, filter it, and take the solid to obtain the washed fly ash. S2. Mix the solid fly ash, deionized water, hydrochloric acid solution with a concentration of 1~1.2mol / L, and aluminum chloride. The mass ratio of solid fly ash to aluminum chloride is (5~20):1. Add deionized water at a liquid-to-solid ratio of (10~14) ml:1g. Adjust the pH to 11~13 with sodium hydroxide. After thorough stirring, transfer the mixture to a ball mill jar and control the temperature to 100-120℃. Ball mill at a speed of 700~900rpm, a ball-to-material ratio of (4~7):1, and a milling time of 4~6h. Centrifuge, wash with water, and dry the solid-liquid mixture obtained after ball milling to obtain a fly ash-based bimetallic hydroxide, denoted as: CaAl-Cl-LDH. S3. Add ammonium tetrathiomolybdate to the fly ash-based bimetallic hydroxide obtained in S2 at a mass ratio of (1.1~1.5):1; then add deionized water at a liquid-to-solid ratio of (8~12) ml:1g, control the temperature to 80-100℃, and perform ball milling treatment; the ball milling treatment conditions are: ball-to-material ratio (8~10):1, ball milling time 6~8h, and rotation speed 400~500rpm; S4. Centrifuge the mixture in S3, filter, wash twice with water, and dry at 80~105℃ under nitrogen atmosphere to obtain molybdenum sulfide intercalation modified fly ash base layer bimetallic hydroxide, denoted as: CaAl-MoS4-LDH.

[0029] A second aspect of the present invention provides a molybdenum sulfide intercalation modified fly ash-based bimetallic hydroxide prepared by the method described in the first aspect.

[0030] The present invention also provides the application of the molybdenum sulfide intercalation modified fly ash-based bimetallic hydroxide prepared by the method described in the first aspect in the adsorption of heavy metals in wastewater.

[0031] The application of the molybdenum sulfide intercalation modified fly ash-based bimetallic hydroxide prepared by the method described in the first aspect in the selective adsorption of heavy metals in wastewater.

[0032] In some embodiments of the present invention, the selectively adsorbed heavy metals include Ag, Hg, Cu, and Pb. In some embodiments of the present invention, Ag is preferred, followed by Hg.

[0033] Example 1 A method for preparing fly ash-based bimetallic hydroxides by molybdenum sulfide intercalation modification includes the following steps: S1: Add the fly ash from the waste incineration to a 1 mol / L NaOH solution, with a liquid-to-solid ratio of 10 ml: 1 g, stir for 6 h, and let stand for 24 h; filter the resulting mixture through a 0.45 μm filter membrane to obtain the solid. S2: Take fly ash and aluminum chloride treated in S1 at a mass ratio of 10:1, add 1 mol / L hydrochloric acid solution at a liquid-solid ratio of 3 ml: 1 g and mix well. Add deionized water at a liquid-solid ratio of 10 ml: 1 g, add 2 M NaOH solution to adjust the pH to 12, transfer the mixture to a ball mill jar, set the speed to 900 rpm, control the temperature at 110℃, and ball mill for 6 h. The resulting mixture is centrifuged and washed with water, and dried at 105℃ for 24 h to obtain fly ash-based basal bimetallic hydroxide, denoted as: CaAl-Cl-LDH; S3: The obtained fly ash-based bimetallic hydroxide and ammonium tetrathiomolybdate were added to a ball mill jar at a mass ratio of 1.2:1. Deionized water was added at a liquid-to-solid ratio of 8 ml: 1 g. Mechanochemical treatment was carried out under the conditions of ball-to-material ratio of 10:1 and ball milling speed of 400 rpm for 6 hours at a ball milling temperature of 80℃. S4: The solid phase was separated by centrifugation at 5500 rpm, washed twice with deionized water and once with ethanol, and dried at 100℃ for 12 h under nitrogen atmosphere to obtain molybdenum sulfide intercalation modified fly ash base layer bimetallic hydroxide.

[0034] Example 2 The preparation method is the same as in Example 1, except that in step S2, 2M NaOH solution is added to adjust the pH to 13.

[0035] Example 3 The preparation method is the same as in Example 1, except that the mass ratio of fly ash to aluminum chloride in step S2 is set to 15:1.

[0036] Example 4 The preparation method is the same as in Example 1, except that the mass ratio of fly ash to aluminum chloride in step S2 is set to 20:1.

[0037] Example 5 The difference from Example 1 is that the ball milling speed is set to 800 rpm in step S2.

[0038] Example 6 The difference from Example 1 is that the ball milling speed is set to 500 rpm in step S3.

[0039] Example 7 The difference from Example 1 is that the ball milling time in step S2 is set to 4 hours.

[0040] Example 8 The difference from Example 1 is that the ball milling time in step S3 is set to 8 hours.

[0041] Example 9 The difference from Example 1 is that the liquid-to-solid ratio in step S2 is 12 ml: 1 g.

[0042] Example 10 The difference from Example 1 is that the liquid-to-solid ratio added in step S3 is 10 ml: 1 g.

[0043] Comparative Example 1 The difference from Example 1 is that in step S2, 2M NaOH solution is added to adjust the pH to 10.

[0044] Comparative Example 2 The difference from Example 1 is that the mass ratio of fly ash to aluminum chloride in step S2 is set to 25:1.

[0045] Comparative Example 3 The difference from Example 1 is that the ball mill speed is set to 500 rpm in step S2.

[0046] Comparative Example 4 The difference from Example 1 is that the ball-to-material ratio in step S3 is 10:1.

[0047] Comparative Example 5 The difference from Example 1 is that the ball milling speed is set to 900 rpm in step S3.

[0048] Comparative Example 6 The difference from Example 1 is that the ball milling time in step S2 is set to 2 hours.

[0049] Comparative Example 7 The difference from Example 1 is that the ball milling temperature in step S2 is set to 80°C.

[0050] Comparative Example 8 The difference from Example 1 is that the ball milling temperature in step S3 is set to 120°C.

[0051] Comparative Example 9 The difference from Example 1 is that in step S3, the liquid-to-solid ratio is 5 ml: 1 g.

[0052] Comparative Example 10 The difference from Example 1 is that the mass ratio of fly ash-based bimetallic hydroxide and ammonium tetrathiomolybdate in step S3 is 2:1.

[0053] Adsorption experiments were conducted using the molybdenum sulfide intercalated modified fly ash-based bimetallic hydroxides prepared in Examples 1 to 10 and Comparative Examples 1 to 9, as follows: (1) 0.05 g of the molybdenum sulfide intercalation modified fly ash base layer bimetallic hydroxide material prepared above was mixed with 100 ml of simulated solution. The initial concentrations of silver nitrate, mercuric nitrate, lead nitrate and copper nitrate in the four simulated solutions were all 500 mg / L. The mixture was stirred at 400 rpm for 6 h at room temperature (25 °C) and centrifuged at 7000 rpm for 5 min to obtain supernatant and separation slurry. The supernatant was passed through a 0.22 μm filter to obtain filtrate. The concentration of heavy metal ions in the liquid phase before and after adsorption was determined by ICP-OES.

[0054] The adsorption results of the materials prepared in the examples and comparative examples are shown in Table 1.

[0055] Table 1. Heavy metal adsorption results of the materials prepared in Examples 1-10 and Comparative Examples 1-10

[0056] The results showed that, using the preparation method of this application, under suitable conditions, the adsorption capacity of the prepared product for Ag, Hg, Cu, and Pb was significantly greater than that of the product prepared under the comparative sample. However, unsuitable conditions affected the synthesis and structural optimization of LDHs in step S2, which led to the lower adsorption capacity of MoS4 in S3. 2- Cl replacing the interlayer -MoS4 is inserted between LDH layers to form LDHs. 2- Failure to do so will significantly affect the heavy metal adsorption capacity of LDHs produced from fly ash.

[0057] The adsorption effect of the product and the final product obtained in step S2 of the embodiment was tested, and the results are shown in Table 2.

[0058] Table 2 MoS4 2- Adsorption effect of fly ash-based bimetallic hydroxides before and after intercalation modification

[0059] The results showed that LDHs produced from waste incineration fly ash were processed using MoS4. 2- After intercalation modification, the adsorption capacity for heavy metals is significantly improved, and the improvement for silver ions is particularly obvious.

[0060] (2) 0.05 g of the molybdenum sulfide intercalation modified fly ash-based bimetallic hydroxide material prepared in Example 1 was mixed with 100 ml of simulated solution. The initial concentrations of silver nitrate, mercuric nitrate, lead nitrate, and copper nitrate in the simulated solution were all 500 mg / L. The mixture was stirred at 400 rpm for 6 h at room temperature (25 °C) and centrifuged at 7000 rpm for 5 min to obtain the supernatant and separation slurry. The supernatant was passed through a 0.22 μm filter to obtain the filtrate. The concentrations of heavy metal ions in the liquid phase before and after adsorption were determined by ICP-OES. The results are shown in Table 3.

[0061] Table 3. Adsorption effect of molybdenum sulfide intercalation modified fly ash-based bimetallic hydroxide prepared in Example 1

[0062] The results showed that LDHs produced from waste incineration fly ash were processed using MoS4. 2- After intercalation modification, the adsorption of heavy metals is selective, with the selectivity being, in descending order, Ag. + >Hg 2+ >Cu 2+ >Pb 2+ .

[0063] (3) 0.1 g of the molybdenum sulfide intercalation modified fly ash base layer bimetallic hydroxide material prepared in Example 1 and LDHs prepared in Example 1 before ball milling in step S3 were placed in 100 ml of water and stirred at 400 rpm for 6 h at room temperature of 25 °C. After filtration through a 0.45 μm membrane, the amount of Mo precipitated was analyzed by ion chromatography and the results are shown in Table 4.

[0064] Table 4 Comparison of Mo precipitation in materials before and after LDHs ball milling

[0065] The results showed that the amount of Mo precipitated in LDHs before ball milling was 1.94 times that of LDHs after ball milling. The amount of Mo precipitated in the modified LDHs material obtained after S3 ball milling was nearly half that of the material before ball milling. The modified LDHs material obtained after S3 ball milling had more stable Mo and was less likely to precipitate, thus reducing the harm of the material itself.

[0066] All documents mentioned in this invention are incorporated herein by reference as if each document were individually incorporated by reference. Furthermore, it should be understood that after reading the foregoing teachings 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 this application.

Claims

1. The application of molybdenum sulfide intercalation modified fly ash-based bimetallic hydroxide in the adsorption of heavy metals in wastewater, characterized in that, The molybdenum sulfide intercalation modified fly ash-based bimetallic hydroxide selectively adsorbs heavy metals from wastewater, including Ag, Hg, Cu, and Pb. The preparation of the molybdenum sulfide intercalation modified fly ash-based bimetallic hydroxide includes the following steps: S1. Add sodium hydroxide solution to the fly ash from waste incineration and wash it 1-2 times. The liquid-solid ratio of sodium hydroxide solution to fly ash is (10-12) ml: 1 g. After filtration, take the solid to obtain the washed fly ash. S2. Mix the solid fly ash, deionized water, hydrochloric acid solution and aluminum chloride. The mass ratio of solid fly ash to aluminum chloride is (5~20):

1. Add deionized water at a liquid-solid ratio of (10~14) ml:1g. The pH was adjusted to 11-13 using sodium hydroxide, and the mixture was stirred thoroughly. The mixture was then transferred to a ball mill jar and ball milled under controlled temperature. The solid-liquid mixture obtained after ball milling was centrifuged, washed with water, and dried to obtain fly ash-based bimetallic hydroxide. S3. Add ammonium tetrathiomolybdate to the fly ash-based bimetallic hydroxide obtained in S2 at a mass ratio of (1.1~1.5):1, then add deionized water and perform temperature-controlled ball milling. S4. After centrifuging, filtering, washing and drying the mixture in S3, molybdenum sulfide intercalation modified fly ash base layer bimetallic hydroxide is obtained. In step S2, the ball mill jar speed is 700~900 rpm, the ball-to-material ratio is (4~7):1, the ball milling time is 4~6 hours, and the ball milling temperature is controlled at 100-120℃. In step S3, the ball milling conditions are as follows: ball-to-material ratio (8~10):1, ball milling time 6~8h, rotation speed 400~500rpm, and ball milling temperature controlled at 80-100℃.

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

3. The application according to claim 1, characterized in that: In step S1, the immersion method is as follows: shake thoroughly for 6-8 hours and let stand for 22-24 hours.

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

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

6. The application according to claim 1, characterized in that: In step S4, the washing process consists of two water washes and one ethanol wash.

7. The application according to claim 1, characterized in that: In step S4, the drying process is carried out at 80~105℃ under a nitrogen atmosphere.

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