Method for preparing functional membrane for recovering noble metal ions from oil-containing wastewater and application thereof

Abstract

The application discloses a preparation method and application of a functional membrane for recovering noble metal ions in oil-containing wastewater, and belongs to the field of functional membrane materials. The method comprises the following steps: preparing hydrazide functional group modified carbon nanotubes CNTs-PAH; first, acrylic acid is grafted to the surface of the carbon nanotubes by using a graft polymerization method to obtain a first-step product CNTs-PAA. Then, hydrazide functional group modified carbon nanotubes (CNTs-PAH) are obtained by reacting adipic acid dihydrazide with a carboxyl functional group; a monolayer MXene nanosheet is prepared; and based on the CNTs-PAH and the MXene, a CNTs-PAH / MXene composite membrane is prepared by using a vacuum suction filtration method.

Description

Technical Field

[0001] This invention relates to the field of functional membrane materials, specifically to a method for preparing a functional membrane for recovering precious metal ions from oily wastewater and its application. Background Technology

[0002] Carbon nanotubes possess a large specific surface area, a loose and porous network structure, and excellent mechanical properties, making them ideal materials for constructing separation membranes. Compared with other superwetting membranes, surface functionalization and porous network microstructure give them an inherent advantage as functional membranes. Studies have shown that the functional groups on the surface of carbon nanotubes are a crucial factor in enhancing their ability to recover noble metal ions. Oxidation with strong oxidizing acids or hydrogen peroxide, or grafting with polymers containing noble metal ion ligands, can enrich the surface of carbon nanotubes with functional groups, thereby modulating their physicochemical properties and resulting in superior recovery capabilities. However, most reported separation membranes can only recover noble metals from single aqueous solutions, while the pollutant composition in actual wastewater is often complex, leading to less than ideal results for carbon nanotube membranes in recovering noble metal ions from oily wastewater. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention proposes a method for preparing a functional membrane for recovering precious metal ions from oily wastewater and its application.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] A method for preparing a functional membrane for recovering precious metal ions from oily wastewater includes the following steps:

[0006] Acrylic acid was grafted onto the surface of carbon nanotubes using a graft polymerization method to obtain CNTs-PAA;

[0007] Carbon nanotubes (CNTs-PAH) modified with hydrazide functional groups were obtained by reacting adipic acid dihydrazide with carboxyl functional groups.

[0008] Preparation of monolayer MXene nanosheets;

[0009] A CNTs-PAH / MXene composite membrane was prepared by vacuum filtration based on CNTs-PAH and Mxene nanosheets.

[0010] Optionally, the preparation method of CNTs-PAA includes the following steps: CNTs are dispersed in acetone and ultrasonically treated; then acrylic acid after vacuum distillation and recrystallized benzoyl peroxide BPO are added to the above dispersion; the resulting product CNTs-PAA is washed with deionized water and vacuum dried at 30°C.

[0011] Optionally, the preparation method of CNTs-PAH specifically includes the following steps: dispersing CNTS-PAA in N,N-dimethylformamide (DMF), then adding N,N'-carbonyldiimidazole, adding the resulting mixture to a DMF solution containing adipic acid dihydrazide, and collecting the product CNTs-PAH by filtration and vacuum drying at 30°C.

[0012] Optionally, the method for preparing monolayer MXene nanosheets includes the following steps: adding lithium fluoride to hydrochloric acid to prepare an etching solution; adding Ti3AlC2 powder to the etching solution under ice-water bath conditions, and then transferring it to an oil bath for stirring; washing the product obtained after the reaction with deionized water by centrifugation multiple times, removing the precipitate by centrifugation at high speed, and freeze-drying the suspension to obtain Ti3C2T x MXene nanosheets.

[0013] Optionally, the method for preparing CNTs-PAH / MXene composite membrane by vacuum filtration includes the following steps: dispersing CNTs-PAH powder in deionized water and ultrasonicating it; then dispersing MXene nanosheets in deionized water and ultrasonicating them; then mixing the MXene dispersion and the CNTs-PAH dispersion, ultrasonicating them, and then filtration to form a membrane.

[0014] Optionally, the mass ratio of CNTs-PAH to MXene nanosheets is 1:(0.1 to 0.5).

[0015] The functional membrane prepared by the above-mentioned method for recovering precious metal ions from oily wastewater is a functional membrane.

[0016] The above-mentioned functional membranes are used in the recovery of metal ions and the catalysis of organic pollutants.

[0017] The beneficial effects of this invention are:

[0018] Acylhydrazine functional groups (R-CO-NHNH2) were grafted onto the surface of carbon nanotubes. These acylhydrazine functional groups have the ability to rapidly and selectively reduce noble metal ions in aqueous solutions.

[0019] Secondly, a two-dimensional Ti3C2T was introduced. x MXene nanosheets are used to address the problem of low oil-water separation efficiency. MXene nanosheets possess hydrophilic surfaces, large surface areas, high electrical conductivity, abundant surface functional groups, redox properties, and high adsorption capacity, making them widely applicable in the field of water treatment.

[0020] Introducing MXene nanosheets into carbon nanotube membrane systems can optimize the surface wettability of the composite membrane and synergistically enhance its ability to recover precious metals, thereby enabling the direct recovery of precious metal ions during oil / water separation. Attached Figure Description

[0021] The invention will now be further described with reference to the accompanying drawings.

[0022] Figure 1 This is a flowchart of the synthesis process of the present invention;

[0023] Figure 2 The contact angles of seven membranes to chloroform are shown (M-1: CNTs-PAH / Mxene-10 membrane, M-2: CNTs-PAH / Mxene-20 membrane, M-3: CNTs-PAH / Mxene-30 membrane, M-4: CNTs-PAH / Mxene-50 membrane, M-5: CNTs membrane, M-6: CNTs-PAH membrane, M-7: MXene membrane).

[0024] Figure 3 The efficiency of seven membranes in recovering silver ions and the efficiency of oil-water separation in oil-water emulsions;

[0025] Figure 4 The maximum recovery capacity of the CNTs-PAH / Mxene-20 membrane for three noble metal ions;

[0026] Figure 5 SEM images of Ag(a), Au(b) and Pd(c) recovered from CNTs-PAH / Mxene-20 membrane;

[0027] Figure 6 The catalytic efficiency of CNTs-PAH / Mxene-20 membrane for the recovery of three noble metals on 4-nitrophenol. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] In some embodiments of the present invention, a method for preparing a functional membrane is disclosed, comprising the following steps:

[0030] 1) First, carbon nanotubes modified with hydrazide functional groups were prepared: 0.1 g CNTs were dispersed in 100 mL acetone and sonicated for 20 min. Then, 1.0 g of acrylic acid after vacuum distillation and 0.055 g of recrystallized benzoyl peroxide (BPO) were added to the dispersion, and the mixture was stirred at 75 °C for 8 h (the reaction was carried out under N2 atmosphere). The resulting product, CNTs-PAA, was washed with deionized water and dried under vacuum at 30 °C.

[0031] 2) Subsequently, 0.1 g of CNTs / PAA was uniformly dispersed in 50 mL of N,N-dimethylformamide (DMF). 1 g of N,N'-carbonyldiimidazole was dissolved in 10 mL of DMF and poured into the CNTs-PAA dispersion, and stirred at room temperature for 12 h. The resulting mixture was then added dropwise to an adipic acid dihydrazide solution (10 g of adipic acid dihydrazide dissolved in 50 mL of DMF), and stirred at 45 °C for 24 h.

[0032] The obtained product CNTs-PAH was purified by washing and then vacuum dried at 30°C for 12 h.

[0033] 3) Then, monolayer MXene nanosheets were prepared: 1.6 g of lithium fluoride (LiF) was added to 20 mL of 9 mol / L hydrochloric acid (HCl) to prepare an etching solution. 1.0 g of Ti3AlC2 powder was weighed and slowly added to the LiF-HCl etching solution under ice-water bath conditions, and then transferred to a 45℃ oil bath and stirred for 36 h. After the reaction, the product was washed several times with deionized water by centrifugation, and the precipitate was removed by centrifugation at high speed. The suspension was freeze-dried to obtain Ti3C2Tx MXene nanosheets.

[0034] 4) Finally, the CNTs-PAH / MXene composite membrane was prepared by vacuum filtration: 20 mg of CNTs-PAH powder was dispersed in 200 mL of deionized water and sonicated for 30 min. Then, 10 mg of MXene was dispersed in 200 mL of deionized water and sonicated for 1 h. Different volumes of MXene dispersion (5, 10, 15, and 25 mL) were then mixed with 25 mL of CNTs-PAH dispersion, sonicated for 10 min, and then filtered to form the membrane.

[0035] The prepared composite membranes were named CNTs-PAH / MXene-10, CNTs-PAH / MXene-20, CNTs-PAH / MXene-30, and CNTs-PAH / MXene-50, respectively.

[0036] Comparative Example 1:

[0037] 1) Disperse 10 mg of CNT powder in a mixture of 50 mL of deionized water and 50 mL of ethanol, and sonicate for 1 h. Dispersion A is obtained.

[0038] 2) Take 30 mL of dispersion A and prepare CNT membrane by vacuum filtration.

[0039] Comparative Example 2:

[0040] 1) Disperse 10 mg of CNTs-PAH powder in 100 mL of deionized water and sonicate for 30 min to obtain dispersion A.

[0041] 2) Take 30 mL of dispersion A and prepare CNTs-PAH membrane by vacuum filtration.

[0042] Comparative Example 3:

[0043] 1) Disperse 10 mg of MXene powder in 100 mL of deionized water and sonicate for 1 h. Dispersion A is obtained.

[0044] 2) Take 30 mL of dispersion A and prepare MXene membrane by vacuum filtration.

[0045] Figure 2 The figures represent the oil contact angles of membranes prepared under different embodiment and comparative conditions. The underwater oil contact angles of the membranes in the embodiments are all greater than 150°, exhibiting underwater superoleophobic behavior. With the introduction of MXene, the oil contact angle of the membrane shows a trend of first increasing and then decreasing. This is due to the synergistic effect of the surface roughness and hydrophilicity of the composite membrane, which further improves the underwater superoleophobicity of the membrane. In Example 2, the CNTs-PAH / MXene-20 membrane exhibits a higher repulsion effect to chloroform, with an underwater oil contact angle as high as 156°. The oil contact angle of the CNTs membrane in Comparative Example 1 is only 137°; after hydrazide functionalization, the oil contact angle of the CNTs-PAH membrane in Comparative Example 2 increases to 149°; and the MXene membrane in Comparative Example 3, due to its rough surface structure, has an oil contact angle of 151°.

[0046] Figure 3 This study examines the oil-water separation efficiency and noble metal ion recovery capabilities of the membranes prepared through the methods of various embodiments and comparative examples. Comparative Example 1 shows that the original carbon nanotube membrane effectively recovers Ag in oil-water emulsions. + The recovery efficiency and oil-water emulsion separation efficiency were very low, at 31.8% and 59.4%, respectively; the modified CNTs-PAH membrane showed poor Ag recovery efficiency. + The recovery efficiency was greatly improved (89.2%), but the oil-water separation efficiency was still not high (76.8%); in Comparative Example 3, the MXene membrane, due to its abundant unsaturated Ti atomic sites, showed improved Ag recovery efficiency. +The recovery efficiency reached 84.2%, and the oil-water separation efficiency was 92.6%. Introducing an appropriate amount of MXene into the composite membrane system can optimize the surface energy of the composite membrane to a certain extent, giving it the best separation performance for oil-water emulsions, and also maximizing the composite membrane's ability to capture silver ions. With increasing MXene content, the Ag content of the composite membrane... + The recovery efficiency initially increased and then decreased, while the oil-water separation efficiency continued to improve. In one example, the CNTs-PAH / MXene-20 membrane achieved a recovery efficiency of up to 96.9% for noble metal ions in an oil-water emulsion, and an oil-water separation efficiency of 92.1%.

[0047] Figure 4 The maximum recovery capacity of the CNTs-PAH / Mxene-20 membrane for the three noble metal ions in the examples is shown. The maximum recovery capacity of the CNTs-PAH / Mxene-20 composite membrane for the three noble metal ions Ag(Ⅰ), Au(Ⅲ) and Pd(Ⅱ) is 527 mg / g, 631 mg / g and 464 mg / g, respectively.

[0048] Figure 5 The image shows a SEM image of the CNTs-PAH / Mxene-20 membrane used in the example after recovering three noble metal ions, Ag(Ⅰ), Au(Ⅲ) and Pd(Ⅱ). A large number of nanoparticles can be clearly seen on the surface of the composite membrane in the image.

[0049] Figure 6 The efficiency of the CNTs-PAH / Mxene-20 membrane in the examples for catalyzing 4-NP after noble metal recovery is shown. The membrane without noble metal support has a catalytic efficiency of only 41.3%. The CNTs-PAH / Mxene-20 membrane with noble metal nanoparticles loaded exhibits excellent catalytic ability, capable of converting toxic p-nitrophenol into non-toxic p-aminophenol, with catalytic efficiencies of 98.2%, 99.2%, and 96.6%, respectively.

[0050] The testing / calculation methods for the above indicators are as follows:

[0051] Precious metal recovery efficiency: First, a certain amount of silver nitrate (chloroauric acid, palladium chloride) was dissolved in 200 mL of ultrapure water. 1 g of Tween 80 was added to the solution and stirred vigorously. Then, 8 mL of chloroform was added, and the mixture was stirred vigorously for 4 hours to form an oil-in-water emulsion containing precious metal ions. The membrane recovery efficiency was tested using a vacuum filtration device at room temperature. The effective filtration area of ​​the membrane was 12.56 cm². 2 The vacuum pressure was 1.0 bar, the concentration of precious metal ions was 20 ppm, and the filtration volume was 20 mL.

[0052] The precious metal recovery efficiency (R1) is calculated using the following formula (1):

[0053]

[0054] Where C1 represents the concentration of noble metal ions in the filtrate, and C0 represents the concentration of noble metal ions in the original solution. The concentration of noble metal ions can be obtained by AAS or ICP-OES / MS testing.

[0055] The oil-water separation efficiency (R2) is calculated using the following formula (2):

[0056]

[0057] Among them, C p C represents the oil content in the filtrate. f This represents the oil content in the oil-in-water emulsion. Oil concentrations were obtained using a UV-Vis spectrophotometer.

[0058] Catalytic efficiency of 4-nitrophenol: 2.70 mL of 4-NP aqueous solution (0.10 mM) was mixed with 0.30 mL of NaBH4 solution (0.10 mM). The catalytic ability of the membrane after recovering the noble metal was then tested using a vacuum filtration device for 4-NP.

[0059] The catalytic efficiency (R3) is calculated using the following formula (3):

[0060]

[0061] Among them, C ′ C represents the concentration of 4-NP in the filtrate, and C represents the concentration of 4-NP in the original solution. The concentration of 4-NP can be obtained by measuring with a UV-Vis spectrophotometer.

[0062] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0063] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for preparing a functional membrane for recovering precious metal ions from oily wastewater, characterized in that, Includes the following steps: Acrylic acid was grafted onto the surface of carbon nanotubes using a graft polymerization method to obtain CNTs-PAA; Carbon nanotubes (CNTs-PAH) modified with hydrazide functional groups were obtained by reacting adipic acid dihydrazide with carboxyl functional groups. Preparation of monolayer MXene nanosheets; CNTs-PAH / MXene composite membranes were prepared by vacuum filtration based on CNTs-PAH and Mxene nanosheets. The preparation method of CNTs-PAA includes the following steps: CNTs are dispersed in acetone and ultrasonically treated; then acrylic acid after vacuum distillation and recrystallized benzoyl peroxide BPO are added; the resulting product CNTs-PAA is washed with deionized water and vacuum dried at 30°C. The preparation method of CNTs-PAH specifically includes the following steps: dispersing CNTs-PAA in DMF, adding N,N' carbonyl diimidazole, adding the resulting mixture to a DMF solution containing adipic acid dihydrazide, collecting the product CNTs-PAH by filtration and vacuum drying at 30°C; The method for preparing monolayer MXene nanosheets includes the following steps: adding lithium fluoride to hydrochloric acid to prepare an etching solution; adding Ti3AlC2 powder to the etching solution under ice-water bath conditions, and then transferring it to an oil bath for stirring; washing the product obtained after the reaction with deionized water by centrifugation multiple times, removing the precipitate by centrifugation at high speed, and freeze-drying the suspension to obtain Ti3C2T x MXene nanosheets; The mass ratio of CNTs-PAH to MXene nanosheets is 1:(0.1-0.5); Introducing MXene nanosheets into the carbon nanotube membrane system optimizes the surface wettability of the composite membrane and synergistically enhances its ability to recover precious metals, thereby enabling the direct recovery of precious metal ions during oil-water separation.

2. The method for preparing a functional membrane for recovering precious metal ions from oily wastewater according to claim 1, characterized in that, The method for preparing CNTs-PAH / MXene composite membrane by vacuum filtration includes the following steps: dispersing CNTs-PAH powder in deionized water and ultrasonicating it; then dispersing MXene nanosheets in deionized water and ultrasonicating them; then mixing the MXene dispersion and the CNTs-PAH dispersion, ultrasonicating them, and then filtration to form a membrane.

3. The functional membrane prepared by the method for recovering precious metal ions from oily wastewater according to any one of claims 1 to 2.

4. The application of the functional membrane according to claim 3 in the recovery of metal ions and the catalysis of organic pollutants.

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