A bimetallic Co / Mn-MOF / ZnAl-LDHs material and its application

Abstract

The present invention discloses a bimetallic Co / Mn-MOF / ZnAl-LDHs material and its application, belonging to the field of wastewater treatment technology. The present invention in situ grows a Co / Mn-based metal organic framework on a ZnAl-LDHs carrier by a hydrothermal method, so that the prepared Co / Mn-MOF@ZnAl-LDHs inherits the advantages of the spatial structure of MOF and the arsenic affinity of LDHs, and the rich adsorbent active surface contains functional groups such as OH, M-O-M and Co / Mn-O, which can highly selectively separate and remove arsenic from complex wastewater, and the preparation method 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.

Description

Technical Field

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

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

[0003] Metal Organic Frameworks (MOFs) are a series of functional materials composed of metal ions / clusters and organic ligands, and are a very promising adsorbent. Due to the unique advantages of MOFs, such as abundant active sites, designable framework structures, large specific surface area (SSA), and high porosity, they have been widely studied in the fields of energy and environment. However, MOFs themselves have defects such as easy agglomeration, poor mechanical strength, non-conductivity, and low adsorption efficiency. In addition, existing adsorption 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 adsorption of As by the adsorption material, resulting in unsatisfactory adsorption of As by the adsorption material. Summary of the Invention

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

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: 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 carboxylic acid was dissolved in a mixed solution of N,N-dimethylformamide, ethanol and water, followed by hydrothermal reaction. After cooling to room temperature, washing and drying, a bimetallic Co / Mn-MOF / ZnAl-LDHs material was obtained.

[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 12-15 hours.

[0015] As a preferred embodiment of the present invention, the molar ratio of the ZnAl-LDHs, manganese chloride tetrahydrate, cobalt chloride hexahydrate and 1,3,5-pyromellitic acid 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 utilizes a mixed system of N,N-dimethylformamide, ethanol, and water to produce a high-purity material. Compared to single-solvent systems, the structure and morphology of the material produced by this mixed system are altered, making it more conducive to the highly selective adsorption of arsenic.

[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 present invention demonstrates the following advantages: Co / Mn-MOF@ZnAl-LDHs, constructed by in situ growth of a Co / Mn-based metal-organic framework (MOF) on a layered double hydroxide (ZnAl-LDHs) substrate, not only provides abundant active sites but also increases the material's surface area and porosity. The in situ growth of MOF on the LDH surface forms an interface between the MOF and LDH, simultaneously creating new pores and optimizing the material's pore size distribution. The introduction of MOF also improves the material's surface roughness, exposing more active sites and increasing contact with reactants. Furthermore, the LDH substrate effectively prevents the aggregation of MOF particles, thereby exposing sites. Therefore, the superior performance of Co / Mn-MOF@ZnAl-LDHs is due to the synergistic effect between LDHs and MOFs. Not only does it inherit the advantages of the MOF's spatial structure and the arsenic affinity of LDHs, but the abundant adsorbent surface functional groups, such as -OH, -COOH, and Co / Mn-O, enable highly selective separation and removal of arsenic from complex wastewaters. 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 for a bimetallic Co / Mn-MOF-based in-situ grown ZnAl-LDHs material, comprising the following steps:

[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 1 M sodium hydroxide solution, and the mixture was stirred continuously at room temperature for 2 hours.

[0027] S4: The resulting mixed solution was transferred to a 500 mL polytetrafluoroethylene-lined stainless steel autoclave and reacted at 120°C for 12 hours. After cooling, the resulting precipitate was centrifuged, 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 Teflon-lined stainless steel autoclave and heated at 120°C for 24 h. After cooling to room temperature, the mixture was washed several times with ethanol and finally 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 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).

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

[0034] Comparative Example 2

[0035] A method for preparing a ZnAl-LDHs material, comprising the following steps:

[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 1 M sodium hydroxide solution, and the mixture was stirred continuously at room temperature for 2 hours.

[0039] S4: The resulting mixed solution was transferred to a 500 mL polytetrafluoroethylene-lined stainless steel autoclave and reacted at 120°C for 12 hours. After cooling, the resulting precipitate was centrifuged, 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 for in-situ growth of ZnAl-LDHs materials based on Co-MOF, 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 1 M sodium hydroxide solution, and the mixture was stirred continuously at room temperature for 2 hours.

[0045] S4: The resulting mixed solution was transferred to a 500 mL polytetrafluoroethylene-lined stainless steel autoclave and reacted at 120°C for 12 hours. After cooling, the resulting precipitate was centrifuged, 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 Teflon-lined stainless steel autoclave and heated at 120°C for 24 h. After cooling to room temperature, the mixture was washed several times with ethanol and finally dried at 60°C to obtain Co-MOF@ZnAl-LDHs.

[0048] Comparative Example 4

[0049] A preparation method for in-situ grown ZnAl-LDHs material based on Mn-MOF, 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 1 M sodium hydroxide solution, and the mixture was stirred continuously at room temperature for 2 hours.

[0053] S4: The resulting mixed solution was transferred to a 500 mL polytetrafluoroethylene-lined stainless steel autoclave and reacted at 120°C for 12 hours. After cooling, the resulting precipitate was centrifuged, 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 Teflon-lined stainless steel autoclave and heated at 120°C for 24 h. After cooling to room temperature, the mixture was washed several times with ethanol and finally dried at 60°C to obtain Mn-MOF@ZnAl-LDHs.

[0056] Comparative Example 5

[0057] A preparation method for in-situ grown MnFe-LDHs material based on a bimetallic Co / Mn-MOF, comprising the following steps:

[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 1 M sodium hydroxide solution, and the mixture was stirred continuously at room temperature for 2 hours.

[0061] S4: The resulting mixed solution was transferred to a 500 mL polytetrafluoroethylene-lined stainless steel autoclave and reacted at 120°C for 12 hours. After cooling, the resulting precipitate was centrifuged, 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 of MnFe-LDHs, 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).

[0063] S6: The mixture was transferred to a 500 mL Teflon-lined stainless steel autoclave and heated at 120°C for 24 h. After cooling to room temperature, the mixture was washed several times with ethanol and finally 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 1 M sodium hydroxide solution, and the mixture was stirred continuously at room temperature for 2 hours.

[0069] S4: The resulting mixed solution was transferred to a 500 mL polytetrafluoroethylene-lined stainless steel autoclave and reacted at 120°C for 12 hours. After cooling, the resulting precipitate was centrifuged, 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 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).

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

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

[0073] Effect Examples

[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 non-ferrous 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 and the large amount of arsenic and other impurities produced after washing are produced by the waste acid. 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 of 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 content of arsenic-containing wastewater with an initial concentration of 10 mg / L and a pH of 10 to 0.2 mg / L, with an arsenic removal rate of 98%. Co / Mn-MOF can reduce the arsenic content of arsenic-containing wastewater with an initial concentration of 10 mg / L and a pH of 10 to 6.26 mg / L, with an arsenic removal rate of 37.4%. ZnAl-LDHs can reduce the arsenic content of arsenic-containing wastewater with an initial concentration of 10 mg / L and a pH of 10 to 5.72 mg / L, with an arsenic removal rate of 42.8%. A comparison shows that the addition of Co / Mn-MOF@ZnAl-LDHs achieves more selective arsenic removal 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+ When constructing ZnAl-LDHs, 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. Furthermore, the carboxylic acid groups coordinate with the BTC linker via the metal ions, supporting the simultaneous incorporation of Co and Mn into the resulting organic framework, allowing the MOFs material to form bimetallic clusters. The Co / Mn-MOF@ZnAl-LDHs adsorbent, prepared by in situ growth of ZnAl-LDHs on a bimetallic Co / Mn-MOF substrate, contains functional groups such as -OH, -COOH, and Co / Mn-O, which can selectively bind to arsenic in wastewater, thereby separating and removing arsenic. ZnAl-LDHs and Co / Mn-MOF alone have low selectivity and removal rates for arsenic removal 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 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 solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A bimetallic Co / Mn-MOF / ZnAl-LDHs material, characterized in that: Using ZnAl-LDHs as supports, a Co / Mn-based metal-organic framework was in situ grown on the supports; 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, cooling it, taking it out, and centrifuging, washing, and drying the resulting precipitate to obtain ZnAl-LDHs; (5) A mixture of ZnAl-LDHs, manganese chloride tetrahydrate, cobalt chloride hexahydrate and 1,3,5-trimethylbenzene carboxylic acid was dissolved in a mixed solution of N,N-dimethylformamide, ethanol and water, followed by hydrothermal reaction. After cooling to room temperature, washing and drying, a bimetallic Co / Mn-MOF / ZnAl-LDHs material was obtained.

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-pyromellitic 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 according to any one of claims 1 to 7 in removing arsenic from wastewater.

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