A method for preparing fly ash-based layered double hydroxide by molybdenum sulfide intercalation modification

Abstract

The application discloses a method for preparing fly ash-based layered double hydroxide by molybdenum sulfide intercalation modification, and the fly ash-based layered double hydroxide is prepared by mixing fly ash, AlCl3 and hydrochloric acid and adjusting pH by NaOH; on the basis, a single-phase material, fly ash-based layered double hydroxide modified by molybdenum sulfide intercalation, is prepared by mechanical-chemical method. 2‑ The method can not only significantly improve the adsorption capacity of fly ash LDHs for heavy metals Pb 2+ , Ag + , Hg 2+ , 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 mechanical-chemical 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

TECHNICAL FIELD

[0001] The application belongs to the technical field of environmental protection, and particularly relates to a method for preparing fly ash-based layered double hydroxide by molybdenum sulfide intercalation modification. BACKGROUND

[0002] With the rapid development of urban economy in China and the enhancement of public environmental awareness, the generation amount and incineration treatment proportion of municipal solid waste continue to rise. This change also leads to the increase in the production of fly ash from municipal solid waste incineration, making the treatment and resource utilization of fly ash an important problem to be solved. At present, waste incineration fly ash is mainly disposed of by landfill and cement kiln co-processing. However, with the continuous improvement of government policies, 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 it is necessary to develop more green resource utilization technologies with high added value and low cost 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.

[0003] Preparation of layered double hydroxide from fly ash is a green resource utilization technology that can meet the needs, has high added value and low cost. At present, layered double hydroxide has some applications in the aspect of heavy metal adsorption, and the LDHs prepared from fly ash have similar adsorption capacity to those on the market. However, in some specific cases where single heavy metal needs to be adsorbed, LDHs lack selectivity. Based on this, there is an urgent need to provide a modified fly ash-based layered double hydroxide with selective heavy metal adsorption. SUMMARY

[0004] In order to solve at least one of the above problems, the application provides a method for preparing fly ash-based layered double hydroxide by molybdenum sulfide intercalation modification.

[0005] In order to achieve the above purpose, the application adopts the following technical means:

[0006] The first aspect of the application provides a method for preparing fly ash-based layered double hydroxide by molybdenum sulfide intercalation modification, comprising the following steps:

[0007] S1, adding waste incineration fly ash into sodium hydroxide solution and soaking 1-2 times, the liquid-solid ratio of sodium hydroxide solution to fly ash is (10-12) ml:1 g; after solid-liquid separation, the solid is taken to obtain soaked fly ash;

[0008] 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;

[0009] 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 temperature-controlled ball milling treatment is performed.

[0010] 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.

[0011] 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.

[0012] In some embodiments of the present application, in step S1, the concentration of the sodium hydroxide solution is 0.5-1 mol / L.

[0013] 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.

[0014] In some embodiments of the present application, in step S2, the concentration of the hydrochloric acid solution is 1-1.2 mol / L.

[0015] 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℃.

[0016] 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.

[0017] 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℃.

[0018] In some embodiments of the present application, in step S4, the washing process is two water washings and one ethanol cleaning.

[0019] In some embodiments of the present application, the drying process in step S4 is at 80-105°C under nitrogen atmosphere.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] Advantages of the present application

[0025] Compared with the prior art, the present application has the following advantages:

[0026] (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.

[0027] (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.

[0028] (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

[0029] Figure 1 The electron microscope image of the LDHs obtained in Example 1 of the present application is shown. DETAILED DESCRIPTION

[0030] 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 thus 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 present application, without parting from the spirit or scope of the application.

[0031] 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 present specification and the cited references, the present specification will control. Those skilled in the art will appreciate that many of the techniques described herein can be performed by means of analogies to techniques described in the cited references. Such analogies are deemed to be encompassed within the scope of the claims.

[0032] The technical solutions of the present application will be further described in detail below in combination with the specific embodiments.

[0033] A method for preparing fly ash-based layered double hydroxide by molybdenum sulfide intercalation modification, the process steps are as follows:

[0034] S1, the waste incineration fly ash is added into a sodium hydroxide solution with a concentration of 0.5-1 mol / L for 1-2 times of immersion washing, the liquid-solid ratio of the sodium hydroxide solution to the fly ash is (10-12) ml:1 g; after being fully shaken for 6-8 h, the mixture is left to stand for 22-24 h, then filtered, and the solid is taken to obtain the immersion-washed fly ash;

[0035] S2, the immersion-washed 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 immersion-washed 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, sodium hydroxide is used to adjust the pH to 11-13, and after being fully stirred, a mixture is obtained, 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;

[0036] S3, ammonium tetrathiomolybdate is added into the fly ash-based layered double hydroxide obtained in S2, the mass ratio is (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;

[0037] S4, centrifuging the mixed solution in S3, filtering, washing twice with water, and drying at 80-105℃ under nitrogen atmosphere to obtain a molybdenum sulfide intercalation modified fly ash based layered double hydroxide, denoted as: CaAl-MoS4-LDH.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] Example 1

[0043] A method for preparing a molybdenum sulfide intercalation modified fly ash based layered double hydroxide, comprising the following steps:

[0044] S1: adding waste incineration fly ash to a 1 mol / L NaOH solution, with a liquid-solid ratio of 10 ml:1 g, stirring for 6 h, and standing for 24 h; the obtained mixture was filtered through a 0.45 μm filter membrane to obtain the solid;

[0045] 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, controlling the temperature at 110℃, and ball milling for 6 h; the obtained mixture was centrifuged and washed with water, and dried at 105℃ for 24 h to obtain a fly ash based layered double hydroxide, denoted as: CaAl-Cl-LDH;

[0046] S3: adding the obtained fly ash based layered double hydroxide and ammonium tetrathiomolybdate to 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℃;

[0047] S4: The solid phase was separated by centrifugation at 5500 rpm, washed with deionized water twice and ethanol once, and dried at 100°C under nitrogen atmosphere for 12h to obtain the molybdenum sulfide intercalated modified fly ash based layered double hydroxide.

[0048] Example 2

[0049] 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.

[0050] Example 3

[0051] 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.

[0052] Example 4

[0053] 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.

[0054] Example 5

[0055] The difference from Example 1 is that in step S2, the ball milling speed is set to 800 rpm.

[0056] Example 6

[0057] The difference from Example 1 is that in step S3, the ball milling speed is set to 500 rpm.

[0058] Example 7

[0059] The difference from Example 1 is that in step S2, the ball milling time is set to 4h.

[0060] Example 8

[0061] The difference from Example 1 is that in step S3, the ball milling time is set to 8h.

[0062] Example 9

[0063] The difference from Example 1 is that in step S2, the liquid-solid ratio is added in the proportion of 12ml:1g.

[0064] Example 10

[0065] The difference from Example 1 is that in step S3, the liquid-solid ratio is added in the proportion of 10ml:1g.

[0066] Comparative Example 1

[0067] The difference from Example 1 is that in step S2, 2M NaOH solution is added to adjust the pH to 10.

[0068] Comparative Example 2

[0069] The difference from Example 1 is that the mass ratio of fly ash to aluminum chloride in step S2 is set to 25:1.

[0070] Comparative Example 3

[0071] The difference from Example 1 is that the ball milling speed in step S2 is set to 500 rpm.

[0072] Comparative Example 4

[0073] The difference from Example 1 is that the ball-to-material ratio in step S3 is 10:1.

[0074] Comparative Example 5

[0075] The difference from Example 1 is that the ball milling speed in step S3 is set to 900 rpm.

[0076] Comparative Example 6

[0077] The difference from Example 1 is that the ball milling time in step S2 is set to 2 h.

[0078] Comparative Example 7

[0079] The difference from Example 1 is that the ball milling temperature in step S2 is set to 80°C.

[0080] Comparative Example 8

[0081] The difference from Example 1 is that the ball milling temperature in step S3 is set to 120°C.

[0082] Comparative Example 9

[0083] The difference from Example 1 is that the liquid-to-solid ratio in step S3 is 5 ml:1 g.

[0084] Comparative Example 10

[0085] The difference from Example 1 is that the mass ratio of fly ash-based layered double hydroxide to ammonium tetrathiomolybdate in step S3 is 2:1.

[0086] The molybdenum sulfide intercalated 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:

[0087] (1) 0.05 g of the molybdenum sulfide intercalation modified fly ash based layered double hydroxide material prepared above was mixed with 100 ml of simulated liquid, the initial concentration of silver nitrate, mercury nitrate, lead nitrate and copper nitrate in the four simulated liquids was 500 mg / L, and the mixture was stirred at 400 rpm at room temperature 25 °C for 6 h, and then centrifuged at 7000 rpm for 5 min to obtain supernatant and separated slurry, and the supernatant was filtered through a 0.22 μm filter to obtain a filtrate, and the concentrations of heavy metal ions in the liquid phase before and after adsorption were determined by ICP-OES.

[0088] The adsorption results of the tests of the materials prepared in the examples and comparative examples are shown in Table 1.

[0089] Table 1 Heavy metal adsorption results of the materials prepared in Examples 1-10 and Comparative Examples 1-9

[0090]

[0091] The results show that: using the preparation method of the present application, under suitable conditions, the adsorption capacity of the product prepared for Ag, Hg, Cu and Pb is significantly greater than that of the product prepared in the comparative examples, wherein the unsuitable conditions affect the synthesis and structure optimization of LDHs in step S2, which leads to the failure of MoS4 2- substituting interlayer Cl - forming LDHs intercalated with MoS4 2- in the interlayer, which greatly affects the heavy metal adsorption capacity of fly ash LDHs.

[0092] The product completed step S2 in the examples was tested for adsorption effect with the final product, and the results are shown in Table 2.

[0093] Table 2 Adsorption effect of fly ash based layered double hydroxide before and after MoS4 2- intercalation modification

[0094]

[0095] The results show that: after MoS4 2- intercalation modification of fly ash LDHs, the adsorption capacity for heavy metals is significantly improved, and the improvement for silver ions is particularly obvious.

[0096] (2) 0.05 g of the molybdenum sulfide intercalation modified fly ash based layered double hydroxide material prepared in Example 1 was mixed with 100 ml of simulated liquid, the simulated liquid contained silver nitrate, mercury nitrate, lead nitrate and copper nitrate with initial concentrations of 500 mg / L, and the mixture was stirred at 400 rpm at room temperature of 25 °C for 6 h, and then centrifuged at 7000 rpm for 5 min to obtain supernatant and separated slurry, and the supernatant was filtered through a 0.22 μm filter to obtain filtrate, and 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.

[0097] Table 3 Adsorption effect of the molybdenum sulfide intercalation modified fly ash based layered double hydroxide prepared in Example 1

[0098]

[0099] The results show that the LDHs prepared from waste incineration fly ash is selectively adsorbed to heavy metals after MoS4 2- intercalation modification, and the selectivity is Ag + > Hg 2+ > Cu 2+ > Pb 2+ .

[0100] (3) 0.1 g of the molybdenum sulfide intercalation modified fly ash based layered double hydroxide material prepared in Example 1 and the LDHs before ball milling in the preparation process of Example 1 were respectively placed in 100 ml of water, and the mixture was stirred at 400 rpm at room temperature of 25 °C for 6 h, and then filtered through a 0.45 um membrane, and the Mo element release amount was analyzed by ion chromatography, and the results are shown in Table 4.

[0101] Table 4 Comparison of Mo element release amount in LDHs before and after ball milling

[0102]

[0103] The results show that the Mo release amount in the LDHs before ball milling is 1.94 times that in the LDHs after ball milling, the Mo release amount in the modified LDHs material obtained after S3 ball milling is reduced by nearly 1 times compared with that in the material before ball milling, and the Mo in 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.

[0104] All the documents mentioned in the present application are incorporated herein by reference as if each document were individually incorporated by reference. In addition, it should be understood that various changes and modifications can be made to the present application by those skilled in the art upon reading the above description of the present application, and such equivalent forms are also within the scope of the present application.

Claims

1. A method for preparing fly ash-based bimetallic hydroxides by molybdenum sulfide intercalation modification, characterized in that, 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 method according to claim 1, characterized in that: In step S1, the concentration of sodium hydroxide solution is 0.5~1 mol / L.

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

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

8. A molybdenum sulfide intercalation modified fly ash-based bimetallic hydroxide prepared by the method according to any one of claims 1 to 7.

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