Bimetal Co / Mn-MOF / ZnAl-LDHs material and application thereof

Abstract

The invention discloses a bimetallic Co / Mn-MOF / ZnAl-LDHs material and application thereof, and belongs to the technical field of wastewater treatment. The Co / Mn-based metal organic framework grows in situ on the ZnAl-LDHs carrier through a hydrothermal method, so that the prepared Co / Mn-MOF-ZnAl-LDHs inherit the advantages of the spatial structure of MOF and the arsenic affinity of LDHs, rich adsorbent active surfaces contain functional groups such as-OH, M-O-M and Co / Mn-O, arsenic in complex wastewater can be separated and removed with high selectivity, and the preparation method is simple and economical. Therefore, the prepared Co / Mn-MOF (at) ZnAl-LDHs adsorbent can be used as a potential heavy metal scavenging agent for treating heavy metal polluted underground water or industrial wastewater.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and specifically relates to a bimetallic Co / Mn-MOF / ZnAl-LDHs material and application thereof. Background Art

[0002] Arsenic is highly toxic, bioaccumulative, volatile and potentially carcinogenic. Compared with chemical precipitation, membrane separation, ion exchange and other methods, adsorption is widely used in the treatment of arsenic wastewater due to its advantages of low cost, high efficiency and simple operation.

[0003] Metal Organic Frameworks (MOF) are a series of functional materials composed of metal ions / clusters and organic ligands, and are a promising adsorbent. Due to the unique advantages of MOF, such as abundant active sites, designable framework structure, large specific surface area (SSA) and high porosity, MOF has been widely studied in the fields of energy and environment. However, MOF itself has defects such as easy agglomeration, poor mechanical strength, non-conductivity and low adsorption efficiency. In addition, the existing adsorbent materials adsorb As in a single environment. In fact, when applied, As-containing wastewater is very complex, containing a large amount of metal ions, a large amount of anions, etc., which compete with the adsorbent material for adsorbing As, so that the adsorption effect of the adsorbent material on As is not ideal. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, the present invention provides a bimetallic Co / Mn-MOF / ZnAl-LDHs material and application thereof.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a bimetallic Co / Mn-MOF / ZnAl-LDHs material, using ZnAl-LDHs as a carrier, and in-situ growing a Co / Mn-based metal organic framework on the carrier;

[0006] The preparation method of the bimetallic Co / Mn-MOF / ZnAl-LDHs material comprises the following steps:

[0007] (1) adding zinc nitrate hexahydrate and aluminum nitrate nonahydrate into water to form solution A;

[0008] (2) dissolving sodium carbonate in water to form solution B;

[0009] (3) adding solution B dropwise to solution A to form solution C, adjusting the pH of solution C, and stirring at room temperature to obtain a mixed solution;

[0010] (4) subjecting the mixed solution to a hydrothermal reaction, taking it out after cooling, and centrifuging, washing, and drying the obtained precipitate to obtain ZnAl-LDHs;

[0011] (5) A mixture of ZnAl-LDHs, manganese chloride tetrahydrate, cobalt chloride hexahydrate and 1,3,5-trimethylbenzene trimesic acid was dissolved in a mixed solution of N,N-dimethylformamide, ethanol and water, followed by a hydrothermal reaction. After cooling to room temperature, the mixture was washed and dried to obtain a bimetallic Co / Mn-MOF / ZnAl-LDHs material.

[0012] As a preferred embodiment of the present invention, the molar ratio of the zinc nitrate hexahydrate, the aluminum nitrate nonahydrate and the sodium carbonate is 4-8:3-6:2-4.

[0013] As a preferred embodiment of the present invention, the pH of the adjustment solution C is 10±0.5.

[0014] As a preferred embodiment of the present invention, the temperature of the hydrothermal reaction in step (4) is 120-125°C and the time is 12-15h.

[0015] As a preferred embodiment of the present invention, the molar ratio of ZnAl-LDHs, manganese chloride tetrahydrate, cobalt chloride hexahydrate and 1,3,5-trimethylolpropane is (1-2):(8-16):(4-8):(4-8).

[0016] As a preferred embodiment of the present invention, the volume ratio of N,N-dimethylformamide, ethanol and water is (5-10):(1-2):(1-2).

[0017] The present invention adopts a mixed system of N,N-dimethylformamide, ethanol and water to prepare a high-purity material. Compared with a single solvent system, the structure and morphology of the material prepared by the mixed system of the present invention are changed, which is more conducive to the high selective adsorption of As.

[0018] As a preferred embodiment of the present invention, the temperature of the hydrothermal reaction in step (5) is 120-125°C and the time is 24-26 hours.

[0019] The present invention also claims the use of the bimetallic Co / Mn-MOF / ZnAl-LDHs material in removing arsenic from wastewater.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention not only brings abundant active sites, but also improves the large specific surface area and porosity of the material by in-situ growth of Co / Mn-based metal organic framework on layered double hydroxide ZnAl-LDHs as a carrier. During the in-situ growth of MOF on the surface of LDH, an interface between MOF and LDH is formed, and new pores are generated, thereby optimizing the pore size distribution of the material. The introduction of MOF also improves the surface roughness of the material, exposes more active sites, and increases contact with reactants. In addition, the LDH substrate effectively prevents the aggregation of MOF particles, thereby exposing the sites. Therefore, the excellent performance of Co / Mn-MOF@ZnAl-LDHs is caused by the synergistic effect between LDHs and MOF, which not only inherits the advantages of the spatial structure of MOF and the arsenic affinity of LDHs, but also contains -OH, -COOH and Co / Mn-O functional groups on the active surface of the rich adsorbent, which can highly selectively separate and remove arsenic from complex wastewater. The preparation method of the present invention is simple and economical. Therefore, the prepared Co / Mn-MOF@ZnAl-LDHs adsorbent can be used as a potential heavy metal scavenger for the treatment of heavy metal-contaminated groundwater or industrial wastewater. DETAILED DESCRIPTION

[0021] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0022] Example 1

[0023] A preparation method of a bimetallic Co / Mn-MOF-based in-situ grown ZnAl-LDHs material, the specific steps are as follows:

[0024] S1: 5.94 g of zinc nitrate hexahydrate and 3.75 g of aluminum nitrate nonahydrate were added to 100 mL of deionized water to form solution A.

[0025] S2: Prepare alkaline solution B by dissolving 1.6 g of sodium carbonate in 50 mL of deionized water with continuous stirring.

[0026] S3: Solution B was slowly added dropwise to solution A, and the mixture was stirred vigorously at room temperature to form solution C. The pH of solution C was adjusted to 10±0.5 using 1M sodium hydroxide solution, and the mixture was stirred continuously at room temperature for 2 hours.

[0027] S4: The obtained mixed solution was transferred to a 500 mL polytetrafluoroethylene-lined stainless steel autoclave and reacted at 120°C for 12 hours. After cooling, the obtained precipitate was taken out by centrifugation, washed three times with deionized water, and finally dried at 50°C overnight to obtain ZnAl-LDHs.

[0028] S5: A mixture of 0.45 g ZnAl-LDHs, 2.37 g manganese chloride tetrahydrate, 1.42 g cobalt chloride hexahydrate and 1.26 g 1,3,5-trimethylbenzene carboxylic acid was dissolved in a mixed solution of DMF (N,N-dimethylformamide), ethanol and deionized water (90 mL, 5:1:1, v / v / v).

[0029] S6: The mixture was transferred to a 500 mL polytetrafluoroethylene-lined stainless steel autoclave and heated at 120 °C for 24 h. After cooling to room temperature, it was washed with ethanol several times. Finally, it was dried at 60 °C to obtain Co / Mn-MOF@ZnAl-LDHs.

[0030] Comparative Example 1

[0031] A method for preparing a bimetallic Co / Mn-MOF material, the specific steps are as follows:

[0032] S1: A mixture of 2.37 g of manganese chloride tetrahydrate, 1.42 g of cobalt chloride hexahydrate and 1.26 g of 1,3,5-trimethylbenzene carboxylic acid was dissolved in a mixed solution of DMF (N,N-dimethylformamide), ethanol and deionized water (90 mL, 5:1:1, v / v / v).

[0033] S2: The mixture was transferred to a 500 mL polytetrafluoroethylene-lined stainless steel autoclave and heated at 120 °C for 24 h. After cooling to room temperature, it was washed with ethanol several times. Finally, it was dried at 60 °C to obtain Co / Mn-MOF.

[0034] Comparative Example 2

[0035] A method for preparing a ZnAl-LDHs material, the specific steps are as follows:

[0036] S1: 5.94 g of zinc nitrate hexahydrate and 3.75 g of aluminum nitrate nonahydrate were added to 100 mL of deionized water to form solution A.

[0037] S2: Prepare alkaline solution B by dissolving 1.6 g of sodium carbonate in 50 mL of deionized water with continuous stirring.

[0038] S3: Solution B was slowly added dropwise to solution A, and the mixture was stirred vigorously at room temperature to form solution C. The pH of solution C was adjusted to 10±0.5 using 1M sodium hydroxide solution, and the mixture was stirred continuously at room temperature for 2 hours.

[0039] S4: The obtained mixed solution was transferred to a 500 mL polytetrafluoroethylene-lined stainless steel autoclave and reacted at 120°C for 12 hours. After cooling, the obtained precipitate was taken out by centrifugation, washed three times with deionized water, and finally dried at 50°C overnight to obtain ZnAl-LDHs.

[0040] Comparative Example 3

[0041] A preparation method of a Co-MOF-based in-situ grown ZnAl-LDHs material, the specific steps are as follows:

[0042] S1: 5.94 g of zinc nitrate hexahydrate and 3.75 g of aluminum nitrate nonahydrate were added to 100 mL of deionized water to form solution A.

[0043] S2: Prepare alkaline solution B by dissolving 1.6 g of sodium carbonate in 50 mL of deionized water with continuous stirring.

[0044] S3: Solution B was slowly added dropwise to solution A, and the mixture was stirred vigorously at room temperature to form solution C. The pH of solution C was adjusted to 10±0.5 using 1M sodium hydroxide solution, and the mixture was stirred continuously at room temperature for 2 hours.

[0045] S4: The obtained mixed solution was transferred to a 500 mL polytetrafluoroethylene-lined stainless steel autoclave and reacted at 120°C for 12 hours. After cooling, the obtained precipitate was taken out by centrifugation, washed three times with deionized water, and finally dried at 50°C overnight to obtain ZnAl-LDHs.

[0046] S5: A mixture of 0.45 g ZnAl-LDHs, 1.42 g cobalt chloride hexahydrate and 1.26 g 1,3,5-trimethylbenzene carboxylic acid was dissolved in a mixed solution of DMF (N,N-dimethylformamide), ethanol and deionized water (90 mL, 5:1:1, v / v / v).

[0047] S6: The mixture was transferred to a 500 mL polytetrafluoroethylene-lined stainless steel autoclave and heated at 120 °C for 24 h. After cooling to room temperature, it was washed with ethanol several times. Finally, it was dried at 60 °C to obtain Co-MOF@ZnAl-LDHs.

[0048] Comparative Example 4

[0049] A preparation method of a Mn-MOF-based in-situ grown ZnAl-LDHs material, the specific steps are as follows:

[0050] S1: 5.94 g of zinc nitrate hexahydrate and 3.75 g of aluminum nitrate nonahydrate were added to 100 mL of deionized water to form solution A.

[0051] S2: Prepare alkaline solution B by dissolving 1.6 g of sodium carbonate in 50 mL of deionized water with continuous stirring.

[0052] S3: Solution B was slowly added dropwise to solution A, and the mixture was stirred vigorously at room temperature to form solution C. The pH of solution C was adjusted to 10±0.5 using 1M sodium hydroxide solution, and the mixture was stirred continuously at room temperature for 2 hours.

[0053] S4: The obtained mixed solution was transferred to a 500 mL polytetrafluoroethylene-lined stainless steel autoclave and reacted at 120°C for 12 hours. After cooling, the obtained precipitate was taken out by centrifugation, washed three times with deionized water, and finally dried at 50°C overnight to obtain ZnAl-LDHs.

[0054] S5: A mixture of 0.45 g ZnAl-LDHs, 2.37 g manganese chloride tetrahydrate and 1.26 g 1,3,5-trimethylbenzene carboxylic acid was dissolved in a mixed solution of DMF (N,N-dimethylformamide), ethanol and deionized water (90 mL, 5:1:1, v / v / v).

[0055] S6: The mixture was transferred to a 500 mL polytetrafluoroethylene-lined stainless steel autoclave and heated at 120 °C for 24 h. After cooling to room temperature, it was washed with ethanol several times. Finally, it was dried at 60 °C to obtain Mn-MOF@ZnAl-LDHs.

[0056] Comparative Example 5

[0057] A preparation method of a bimetallic Co / Mn-MOF-based in-situ grown MnFe-LDHs material, the specific steps are as follows:

[0058] S1: 5.02 g of manganese nitrate tetrahydrate and 5.09 g of iron nitrate nonahydrate were added to 100 mL of deionized water to form solution A.

[0059] S2: Prepare alkaline solution B by dissolving 1.6 g of sodium carbonate in 50 mL of deionized water with continuous stirring.

[0060] S3: Solution B was slowly added dropwise to solution A, and the mixture was stirred vigorously at room temperature to form solution C. The pH of solution C was adjusted to 10±0.5 using 1M sodium hydroxide solution, and the mixture was stirred continuously at room temperature for 2 hours.

[0061] S4: The obtained mixed solution was transferred to a 500 mL polytetrafluoroethylene-lined stainless steel autoclave and reacted at 120°C for 12 hours. After cooling, the obtained precipitate was taken out by centrifugation, washed three times with deionized water, and finally dried at 50°C overnight to obtain MnFe-LDHs.

[0062] S5: A mixture of 0.45 g MnFe-LDHs, 2.37 g manganese chloride tetrahydrate, 1.42 g cobalt chloride hexahydrate and 1.26 g 1,3,5-trimethylbenzene carboxylic acid was dissolved in a mixed solution of DMF (N,N-dimethylformamide), ethanol and deionized water (90 mL, 5:1:1, v / v / v).

[0063] S6: The mixture was transferred to a 500 mL polytetrafluoroethylene-lined stainless steel autoclave and heated at 120 °C for 24 h. After cooling to room temperature, it was washed with ethanol several times. Finally, it was dried at 60 °C to obtain Co / Mn-MOF@MnFe-LDHs.

[0064] Comparative Example 6

[0065] A method for preparing a bimetallic Co / Mn-MOF / ZnAl-LDHs material, the specific steps are as follows:

[0066] S1: 5.94 g of zinc nitrate hexahydrate and 3.75 g of aluminum nitrate nonahydrate were added to 100 mL of deionized water to form solution A.

[0067] S2: Prepare alkaline solution B by dissolving 1.6 g of sodium carbonate in 50 mL of deionized water with continuous stirring.

[0068] S3: Solution B was slowly added dropwise to solution A, and the mixture was stirred vigorously at room temperature to form solution C. The pH of solution C was adjusted to 10±0.5 using 1M sodium hydroxide solution, and the mixture was stirred continuously at room temperature for 2 hours.

[0069] S4: The obtained mixed solution was transferred to a 500 mL polytetrafluoroethylene-lined stainless steel autoclave and reacted at 120°C for 12 hours. After cooling, the obtained precipitate was taken out by centrifugation, washed three times with deionized water, and finally dried at 50°C overnight to obtain ZnAl-LDHs.

[0070] S5: A mixture of 2.37 g of manganese chloride tetrahydrate, 1.42 g of cobalt chloride hexahydrate and 1.26 g of 1,3,5-trimethylbenzene carboxylic acid was dissolved in a mixed solution of DMF (N,N-dimethylformamide), ethanol and deionized water (90 mL, 5:1:1, v / v / v).

[0071] S6: The mixture was transferred to a 500 mL polytetrafluoroethylene-lined stainless steel autoclave and heated at 120 °C for 24 h. After cooling to room temperature, it was washed with ethanol several times. Finally, it was dried at 60 °C to obtain Co / Mn-MOF.

[0072] S7: 0.45 g ZnAl-LDHs and the Co / Mn-MOF prepared in S6 were mixed to obtain Co / Mn-MOF / ZnAl-LDHs material.

[0073] Effect example

[0074] The application of the adsorption materials prepared in Example 1 and Comparative Examples 1-6 to efficiently remove arsenic from wastewater is carried out in the following specific steps:

[0075] The arsenic-containing wastewater from nonferrous metal smelting used in this effect example comes from the sulfuric acid workshop of a zinc smelter in the southwest region. The smelting flue gas is washed with a large amount of arsenic and other impurities produced by the waste acid, and ultrapure water is used to prepare the arsenic concentration to 10 mg / L. The main components are shown in Table 1.

[0076] The pH of 10 mg / L arsenic-containing wastewater was adjusted to 10±0.5; then 0.05 g Co / Mn-MOF@ZnAl-LDHs or Co / Mn-MOF adsorbent or ZnAl-LDHs adsorbent was added to 50 ml of arsenic-containing wastewater; the mixture was stirred at a stirring speed of 350 rpm for 24 hours at room temperature and pressure. The metal ion concentration of the filtrate after the reaction was determined by ICP method, see Table 2.

[0077] Table 1

[0078]

[0079]

[0080] Table 2

[0081]

[0082] As shown in Table 2, the Co / Mn-MOF@ZnAl-LDHs prepared in Example 1 can reduce the arsenic in the arsenic-containing wastewater with an initial concentration of 10 mg / L and a pH of 10 to 0.2 mg / L, and the arsenic removal rate is 98%; Co / Mn-MOF can reduce the arsenic in the arsenic-containing wastewater with an initial concentration of 10 mg / L and a pH of 10 to 6.26 mg / L, and the arsenic removal rate is 37.4%; ZnAl-LDHs can reduce the arsenic in the arsenic-containing wastewater with an initial concentration of 10 mg / L and a pH of 10 to 5.72 mg / L, and the arsenic removal rate is 42.8%. By comparison, it is found that the addition of Co / Mn-MOF@ZnAl-LDHs can remove arsenic more selectively than Co / Mn-MOF and ZnAl-LDHs.

[0083] Effect Example 2

[0084] The only difference between this effect example and the application of efficient removal of arsenic in wastewater described in the effect example is that the main components of the arsenic-containing wastewater are shown in Table 3, and the concentration of metal ions in the filtrate after the reaction is determined by ICP method is shown in Table 4.

[0085] Table 3

[0086]

[0087] Table 4

[0088]

[0089]

[0090] Effect Example 3

[0091] The only difference between this effect example and the application of efficient removal of arsenic in wastewater described in the effect example is that the main components of the arsenic-containing wastewater are shown in Table 5, and the concentration of metal ions in the filtrate after the reaction is determined by ICP method is shown in Table 6.

[0092] Table 5

[0093]

[0094] Table 6

[0095]

[0096] According to Table 1-6, the present invention utilizes Zn 2+ and Al 3+ ZnAl-LDHs are constructed, and the active sites on their surfaces are in an unsaturated coordination state with the -OH groups of metal cations, providing abundant coordination sites for the growth of Co / Mn-MOF. In addition, the carboxylic acid groups are coordinated with the BTC linkers through metal ions, supporting the simultaneous incorporation of Co and Mn into the formed organic framework, allowing the MOFs material to form a bimetallic cluster. The Co / Mn-MOF@ZnAl-LDHs adsorbent prepared by in situ growth of ZnAl-LDHs on the bimetallic Co / Mn-MOF base has functional groups such as -OH, -COOH and Co / Mn-O, which can be highly selectively combined with arsenic in wastewater, thereby separating and removing arsenic. ZnAl-LDHs and Co / Mn-MOF alone have low selectivity and removal rate for removing arsenic from non-ferrous metal smelting wastewater. Compared with Example 1, Comparative Examples 3-4 show that Co / Mn-O and MOM functional groups are formed in Example 1, which can significantly improve its adsorption capacity and application range, and show a structure and arsenic removal performance that is superior to that of a single metal MOF. In addition, compared with Comparative Examples 1-6, the Co / Mn-MOF@ZnAl-LDHs prepared by the present invention can achieve high selectivity and high removal rate of As in complex water bodies.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A bimetallic Co / Mn-MOF / ZnAl-LDHs material, characterized in that: Using ZnAl-LDHs as carrier, a Co / Mn-based metal-organic framework was in situ grown on the carrier; The preparation method of the bimetallic Co / Mn-MOF / ZnAl-LDHs material comprises the following steps: (1) adding zinc nitrate hexahydrate and aluminum nitrate nonahydrate into water to form solution A; (2) dissolving sodium carbonate in water to form solution B; (3) adding solution B dropwise to solution A to form solution C, adjusting the pH of solution C, and stirring at room temperature to obtain a mixed solution; (4) subjecting the mixed solution to a hydrothermal reaction, taking it out after cooling, and centrifuging, washing, and drying the obtained precipitate to obtain ZnAl-LDHs; (5) A mixture of ZnAl-LDHs, manganese chloride tetrahydrate, cobalt chloride hexahydrate and 1,3,5-trimethylbenzene trimesic acid was dissolved in a mixed solution of N,N-dimethylformamide, ethanol and water, followed by a hydrothermal reaction. After cooling to room temperature, the mixture was washed and dried to obtain a bimetallic Co / Mn-MOF / ZnAl-LDHs material.

2. The bimetallic Co / Mn-MOF / ZnAl-LDHs material according to claim 1, characterized in that: The molar ratio of the zinc nitrate hexahydrate, the aluminum nitrate nonahydrate and the sodium carbonate is (4-8):(3-6):(2-4).

3. The bimetallic Co / Mn-MOF / ZnAl-LDHs material according to claim 1, characterized in that: The pH of the adjustment solution C is 10±0.

5.

4. The bimetallic Co / Mn-MOF / ZnAl-LDHs material according to claim 1, characterized in that: The temperature of the hydrothermal reaction in step (4) is 120-125° C. and the time is 12-15 hours.

5. The bimetallic Co / Mn-MOF / ZnAl-LDHs material according to claim 1, characterized in that: The molar ratio of the ZnAl-LDHs, manganese chloride tetrahydrate, cobalt chloride hexahydrate and 1,3,5-trimethylbenzene carboxylic acid is (1-2):(8-16):(4-8):(4-8).

6. The bimetallic Co / Mn-MOF / ZnAl-LDHs material according to claim 1, characterized in that: The volume ratio of N,N-dimethylformamide, ethanol and water is (5-10):(1-2):(1-2).

7. The bimetallic Co / Mn-MOF / ZnAl-LDHs material according to claim 1, characterized in that: The temperature of the hydrothermal reaction in step (5) is 120-125° C. and the time is 24-26 hours.

8. Use of the bimetallic Co / Mn-MOF / ZnAl-LDHs material as described in any one of claims 1 to 7 in removing arsenic from wastewater.

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