Preparation method and application of MoS2-PAN composite adsorption film

Abstract

The invention discloses a preparation method and application of a MoS2-coated PAN composite adsorption film, and belongs to the technical field of preparation and application of environmental materials. According to the preparation method disclosed by the invention, MoS2 nanoparticles are encapsulated in a PAN film matrix through a non-solvent induced phase separation method, so that the MoS2-coated PAN composite adsorption film is prepared. On the basis of the idea of blending modification, molybdenum disulfide with a strong affinity effect on heavy metals is introduced into PAN serving as a matrix, so that the adsorption selectivity of the composite membrane is improved, membrane pollution caused by the influence of organic matters on the membrane can be improved, high flux can be kept, and meanwhile, efficient removal of the heavy metals can be realized; the traditional ultrafiltration membrane technology is expected to be replaced in the field of heavy metal removal; the prepared MoS2-coated PAN has an excellent removal effect under an acidic condition; the catalyst has excellent selectivity on removal of Cr (VI), and the removal rate is not obviously reduced in the presence of high-concentration interference anions and cations.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental material preparation and application, and specifically relates to a preparation method and application of a MoS2@PAN composite adsorption film. Background Art

[0002] Due to the large-scale use of chromium, water sources contaminated by chromium have become a serious problem affecting the health of organisms. Chromium exists in various forms in water, ranging from Cr(0) to Cr(VI) due to different pH values, among which trivalent chromium Cr(III) and hexavalent chromium Cr(VI) are the most common. Cr(III) is an indispensable trace element in organisms. A small amount of Cr(III) will not cause great environmental harm. In contrast, Cr(VI) has serious biological toxicity and is one of the three major carcinogenic metals recognized internationally. However, since actual wastewater often coexists with low concentrations of heavy metals and high concentrations of inorganic salts and organic matter, traditional treatment technologies have problems such as poor deep treatment effects, low economic benefits, difficult operation, and secondary pollution. Therefore, how to separate and remove heavy metal chromium in complex water bodies remains a research focus.

[0003] Among various water treatment technologies, membrane separation technology has broad application prospects due to its advantages such as simple operation, high efficiency and stability. However, the trade-off between membrane permeability and selectivity is the focus of research on composite membrane separation technology. Conventional membrane treatment technology is interfered by organic matter and inorganic salts, and the generation of surface scale inhibition leads to serious membrane pollution, which limits its development. In recent years, multifunctional ultrafiltration membranes (MF-UFs) have been widely studied due to their strong adaptability, high separation efficiency, and scalability. The ultrafiltration membrane modified by group orientation has both chemical adsorption and physical retention characteristics, giving full play to the surface complexation and pore size screening effects, and is suitable for the directional removal of heavy metals in water bodies where inorganic salts and organic matter coexist.

[0004] Polyacrylonitrile (PAN) is a commonly used commercial matrix membrane. It is one of the most widely used polymer membrane materials in the field of water treatment due to its high flux, hydrophilicity, high mechanical strength and high thermal stability. It is used in ultrafiltration, seawater desalination and other fields. Molybdenum disulfide (MoS2) is a typical sulfur-rich two-dimensional layered material. It has excellent selectivity for most heavy metal ions due to the complexation and strong affinity between S ligands and heavy metals. However, since MoS2 usually exists in the form of nano-ultrafine powder, there are problems such as easy agglomeration and difficulty in solid-liquid separation in applications, which limits its practical application in the field of water purification.

[0005] Therefore, in the face of the problems of multi-component, low-concentration, and difficult-to-treat heavy metal chromium pollution in water bodies, it is urgent to develop high-efficiency, energy-saving, and low-cost heavy metal water treatment materials. The new composite membrane that combines adsorption with membrane separation is expected to achieve the synergistic advantages of adsorption and separation, steadily improve the quality of effluent water, and broaden the scope of application of UF (ultrafiltration) in the traditional sense. Summary of the invention

[0006] In view of the above problems existing in the prior art, the technical problem to be solved by the present invention is to provide a method for preparing a MoS2@PAN composite adsorption membrane, based on the idea of ​​blending modification, introducing molybdenum disulfide with a strong affinity for heavy metals into PAN as a matrix. Another technical problem to be solved by the present invention is to provide a MoS2@PAN composite adsorption membrane prepared by the above preparation method, which has an excellent removal effect under acidic conditions.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a MoS2@PAN composite adsorption film comprises encapsulating MoS2 nanoparticles in a PAN film matrix through a non-solvent induced phase separation method to prepare the MoS2@PAN composite adsorption film.

[0009] The preparation method of the MoS2@PAN composite adsorption film specifically comprises the following steps:

[0010] 1) Dissolve PAN powder and PEG in DMF and react in a water bath to obtain PAN casting solution;

[0011] 2) adding MoS2 nanoparticles to the PAN casting solution prepared in step 1), and removing residual bubbles by ultrasonication to obtain MoS2@PAN casting solution;

[0012] 3) Pour the MoS2@PAN casting solution obtained in step 2) onto a glass plate and scrape the film. After standing in the air, immerse the glass plate in ultrapure water and solidify to obtain a MoS2@PAN composite adsorption film.

[0013] Preferably, in step 1), the mass ratio of PAN powder to PEG is 20:11.9.

[0014] Preferably, in step 3), the film is scraped to form a film with a thickness of 200 μm.

[0015] Preferably, in step 2), the preparation process of MoS2 nanoparticles is: and CH4N2S were dissolved in deionized water, and the obtained mixed solution was placed in a stainless steel high-pressure reactor lined with polytetrafluoroethylene for reaction. After the reaction was completed, the reactor was cooled to room temperature, the product was washed to neutrality, and then freeze-dried to obtain MoS2 nanoparticles;

[0016] Preferably, the reaction temperature is 180°C and the reaction time is 20 hours.

[0017] Preferably, in step 2), the g / mL ratio of MoS2 nanoparticles to PAN casting solution is 4:30.

[0018] Preferably, in step 1), the temperature of the water bath reaction is 65° C. and the reaction time is 8 h.

[0019] The MoS2@PAN composite adsorption film preparation method is used to prepare the MoS2@PAN composite adsorption film.

[0020] The application of the MoS2@PAN composite adsorption membrane in treating Cr(VI)-containing wastewater.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The doping of MoS2 in the present invention causes a slight decrease in the pure water flux of the composite membrane (from 218 L / m 2 Down to 198 L / m 2 ), but the hydrophilicity of MoS2@PAN composite adsorption membrane was significantly improved, and the time for the contact angle to be reduced to 0° was reduced by 3 s; the membrane flux recovery rate of MoS2@PAN was increased by 30% compared with PAN, and it has excellent anti-fouling ability;

[0023] (2) The present invention uses a blending modification method to encapsulate MoS2 nanoparticles in a PAN membrane matrix through a "non-solvent induced phase separation" method to prepare a composite adsorption membrane (MoS2@PAN); the membrane pore structure is used to achieve effective dispersion of MoS2 powder, overcoming the shortcomings of MoS2 nanoparticles in applications such as easy agglomeration and easy loss;

[0024] (3) Based on the idea of ​​co-modification, the present invention introduces molybdenum disulfide (MoS2) with strong affinity for heavy metals into PAN as a matrix to prepare a composite adsorption membrane (MoS2@PAN) to improve the adsorption selectivity of the composite membrane. This can not only improve the membrane pollution caused by the influence of organic matter, but also achieve efficient removal of heavy metals while retaining high flux. It is expected to replace traditional ultrafiltration membrane technology in the field of heavy metal removal, comprehensively improve the effluent water quality, and significantly reduce operating costs.

[0025] (4) The MoS2@PAN prepared by the present invention has an excellent removal effect under acidic conditions. Isothermal adsorption experiments show that the removal of Cr(VI) by the MoS2@PAN composite adsorption membrane is a spontaneous endothermic process. The increase in temperature is conducive to the removal. The maximum adsorption capacity is 143 mg / g at 298 K. The removal of Cr(VI) by the MoS2@PAN composite membrane reaches equilibrium at around 2200 min, and the adsorption rate is affected by the intraparticle diffusion and membrane diffusion rate.

[0026] (5) The MoS2@PAN composite membrane prepared by the present invention has excellent selectivity for the removal of Cr(VI). In the presence of high concentrations of interfering anions and cations, the removal rate does not show a significant decrease. In addition, the Cu coordinated by S in MoS2@PAN significantly improves the removal rate of Cr(VI) based on the "cation bridging" effect.

[0027] (6) In the treatment of simulated actual wastewater, the MoS2@PAN composite membrane prepared by the present invention maintained a stable effluent concentration at 6000 L / m 2 All of them are lower than the standard of 0.5 mg / L in the "Industrial Wastewater Discharge Standard"; the material can be effectively regenerated using 0.5 M HCl solution, and the composite membrane shows excellent stability under acidic conditions; it has great application potential under low pH conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 SEM images of the upper surface and cross section of the PAN matrix film (a, b, c) and MoS2@PAN (d, e, f) prepared in Example 1;

[0029] Figure 2 Distribution diagram of Mo and S elements on the surface (g, h) and cross section (i, j) of MoS2@PAN prepared in Example 1;

[0030] Figure 3 FTIR spectrum of the MoS2@PAN composite adsorption film prepared in Example 1;

[0031] Figure 4 XRD spectrum of the MoS2@PAN composite adsorption film prepared in Example 1;

[0032] Figure 5 The pure water flux and membrane contact angle change diagram of PAN and MoS2@PAN composite adsorption membrane prepared in Example 1; wherein, Figure (a) is the pure water flux and water recovery rate result diagram of the membrane prepared in the BSA blocking experiment, and Figure (b) is the membrane contact angle change diagram;

[0033] Figure 6The anti-pollution performance diagram of PAN and MoS2@PAN composite adsorption membrane prepared in Example 1; wherein, Figure (a) is a membrane pollution parameter diagram before and after BSA pollution, and Figure (b) is a membrane pollution index diagram;

[0034] Figure 7 The Cr(VI) removal effect and Zeta potential diagram of the MoS2@PAN composite adsorption film prepared in Example 1 at different pH values; wherein, Figure (a) is a Cr(VI) removal effect diagram, and Figure (b) is a Zeta potential diagram;

[0035] Figure 8 The adsorption isotherms of the MoS2@PAN composite adsorption film prepared in Example 1 at different temperatures;

[0036] Fig. 9 The adsorption kinetics of the MoS2@PAN composite adsorption film prepared in Example 1 are fitted with the pseudo-first-order and pseudo-second-order kinetic models; wherein, Figure (b) is a fitting diagram of the pseudo-first-order kinetic model, and Figure (c) is a fitting diagram of the pseudo-second-order kinetic model;

[0037] Fig.10 This is a diagram showing the effect of competing ions on the removal of Cr(VI) by the MoS2@PAN composite adsorption membrane prepared in Example 1;

[0038] Fig.11 Figure 1 is an adsorption performance diagram of the MoS2@PAN composite adsorption membrane prepared in Example 1; wherein, Figure (a) is an adsorption performance diagram of the MoS2@PAN composite adsorption membrane for Cr(VI) in a binary solution, and Figure (b) is an adsorption performance diagram of the MoS2@PAN composite adsorption membrane for different metal ions in a multi-component solution;

[0039] Fig.12 This is a graph showing the removal results of Cr(VI) by the MoS2@PAN composite adsorption membrane prepared in Example 1 under the coexistence of different organic acids;

[0040] Fig.13 This is a diagram showing the simulated actual wastewater performance of the MoS2@PAN composite adsorption membrane prepared in Example 1;

[0041] Fig.14 This is a diagram of the recycling of the MoS2@PAN composite adsorption membrane prepared in Example 1; wherein, Figure (a) is a static cycle adsorption-desorption regeneration diagram, and Figure (b) is a stability diagram of MoS2@PAN under different pH conditions. DETAILED DESCRIPTION

[0042] The present invention will be further illustrated below in conjunction with specific examples. The examples are implemented under the premise of the technical solution of the present invention. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. In the following examples, unless otherwise specified, the technical means used are conventional means well known to those skilled in the art. In the examples, those without specifying specific conditions are carried out according to conventional conditions or the conditions recommended by the manufacturer. Those without specifying the manufacturer for reagents used or instruments are conventional products that can be obtained by commercial purchase.

[0043] The performance testing method adopted by the present invention is as follows:

[0044] (1) The concentration of Cr(VI) was measured by a UV / Vis spectrophotometer using the diphenylcarbazide spectrophotometry method. The total chromium concentration was determined by inductively coupled plasma (ICP-5000). The trivalent chromium concentration was calculated by subtracting the hexavalent chromium concentration from the total chromium concentration.

[0045] (2) Batch adsorption experiments were performed in 50 mL conical flasks. The amount of adsorption film in all experiments was 0.5 g / L. Unless otherwise stated, the adsorption experiments were performed at 25 °C and pH = 2. The pH of the solution was adjusted with negligible volumes of 0.1 M HNO3 and 0.1 M NaOH. The conical flask was oscillated at 140 rpm in a thermostatic oscillator for 24 h to ensure that adsorption equilibrium was reached. At an initial Cr(VI) concentration of 50 mg / L, the contact time between the adsorption film and Cr(VI) was varied to obtain adsorption kinetic data. 2+ 、Ni 2+ ) and mineral cations (Ca 2+ Mg 2+ and Na + ) as interfering ions to evaluate the selectivity of MoS2@PAN for Cr(VI) in a complex environment.

[0046] Example 1

[0047] A method for preparing a MoS2@PAN composite adsorption film comprises the following steps:

[0048] 1) 2.471 g and 4.567 g CH4N2S were dissolved in 70 mL deionized water, and the obtained mixed solution was placed in a stainless steel high-pressure reactor lined with polytetrafluoroethylene and reacted at 180°C for 20 h; after the reactor was cooled to room temperature, it was transferred to a suction filter and washed alternately with ethanol and deionized water three times. After the product was washed to neutrality, it was freeze-dried to obtain MoS2 nanoparticles;

[0049] 2) Dissolve 20 g PAN powder and 11.9 g PEG in 250.96 mL DMF and stir in a 65 °C water bath for 8 h to form a PAN casting solution;

[0050] 3) Add 4 g of MoS2 powder to 30 mL of the PAN casting solution prepared in step 2) and remove residual bubbles by ultrasonic treatment for 15 min to obtain MoS2@PAN casting solution;

[0051] 4) The MoS2@PAN casting solution prepared in step 3) was poured onto a glass plate and a 200 μm thick film was formed using a doctor blade; after standing in air for 30 s, the glass plate was immersed in ultrapure water and cured for 24 h to obtain a MoS2@PAN composite adsorption film.

[0052] Example 2

[0053] When preparing the MoS2@PAN composite adsorption membrane, in step 3), 1 g of MoS2 powder was added to 30 mL of PAN casting solution, and the remaining parameters and preparation steps were the same as in Example 1 to obtain the MoS2@PAN composite adsorption membrane.

[0054] Example 3

[0055] When preparing the MoS2@PAN composite adsorption membrane, in step 3), 2 g of MoS2 powder was added to 30 mL of PAN casting solution, and the remaining parameters and preparation steps were the same as those in Example 1 to obtain the MoS2@PAN composite adsorption membrane.

[0056] Example 4

[0057] When preparing the MoS2@PAN composite adsorption membrane, in step 3), 5 g of MoS2 powder was added to 30 mL of PAN casting solution, and the remaining parameters and preparation steps were the same as in Example 1 to obtain the MoS2@PAN composite adsorption membrane.

[0058] Example 5

[0059] When preparing the MoS2@PAN composite adsorption membrane, in step 3), 10 g of MoS2 powder was added to 30 mL of PAN casting solution, and the remaining parameters and preparation steps were the same as those in Example 1 to obtain the MoS2@PAN composite adsorption membrane.

[0060] Comparative Example 1

[0061] 20.0 g PAN powder and 11.90 g PEG were dissolved in 250.96 mL DMF and stirred in a water bath at 65 °C for 8 h to form a PAN casting solution. Ultrasonication was performed for 30 min to remove bubbles in the casting solution, and then an appropriate amount of the casting solution was placed on a glass plate with a doctor blade to form a film with a thickness of 200 μm. After standing in air for 30 s, the film was immersed in ultrapure water and cured for 24 h to ensure complete phase separation, thereby obtaining a PAN matrix membrane.

[0062] Depend on Figure 1 It can be seen that the PAN matrix membrane of comparative example 1 has a smooth surface and uniform pore size, and the cross section shows an uneven symmetrical structure with obvious finger-like pore paths. The upper ends of many finger-like pores converge into a thin film layer, forming an organic layer unique to the organic membrane ( Figure 1 (a)~(c)). Figure 1 (d) and (e) show that the smooth surface becomes rough after MoS2 doping, and the finger-like pores in the cross section do not show the pore blockage caused by MoS2 doping. Further magnifying the cross-sectional scanning multiple, the nanoflower structure of MoS2 can be observed at a scale of 5 μm ( Figure 1 (f)), indicating that MoS2 was successfully loaded into the membrane.

[0063] Depend on Figure 2 It can be seen that the Mo and S elements are evenly and densely distributed on the surface and cross section, confirming the uniform distribution of MoS2 in the PAN membrane matrix.

[0064] Depend on Figure 3 It can be seen that the wave number is 2242 cm -1 The characteristic peak at 1656 cm-1 is attributed to the (-C≡N) group of PAN, and the other characteristic peaks of PAN appear at 1656, 2928, 1727 and 1448 cm-1. -1 At 1168 and 1075 cm −1 The absorption peak at 486 cm-1 may be due to the Mo-O characteristic peak generated by partial oxidation of the MoS2 surface after contact with air. -1 The stretching vibration characteristic peak of Mo-S shows that MoS2 is successfully introduced into PAN. −1 ) peak shifted to 468 cm −1 , indicating that there is an interaction between MoS2 and Cr(VI) in the composite film.

[0065] Depend on Figure 4It can be seen that the diffraction peaks appearing at 2θ=32° and 56.5° correspond to the (100) and (110) crystal planes in the 2H phase MoS2 standard card, respectively; in addition, it was found that the angle of the (002) crystal plane shifted from 14.4° to 8.6°. Calculated by the Bragg formula (2dsinθ = nλ), the interlayer spacing expanded from 0.62 nm to 1.03 nm, and the expanded interlayer spacing is beneficial to increasing the contact area with pollutants and the transmission of water molecules inside.

[0066] Example 6

[0067] The performance of the MoS2@PAN composite adsorption membranes prepared in Examples 1 to 5 and the PAN matrix membrane prepared in Comparative Example 1 was tested, and the results of pure water flux and maximum adsorption amount of Cr(VI) are shown in Table 1 below.

[0068] Table 1 Pure water flux and maximum adsorption of Cr(VI) in Examples 1 to 5 and Comparative Example 1

[0069]

[0070] Depend on Figure 5 It can be seen that pure water flux is a key indicator for evaluating membrane performance. The size of water flux directly affects the mass transfer rate of pollutants in the membrane pore size. Figure 5 (a) shows that the water flux of the original PAN matrix membrane is 218 L / m 2 After doping with MoS2, the water flux dropped to 198 L / m 2 This is because the doping of a large amount of MoS2 makes the PAN matrix layer more dense, affecting the pore size and porosity of the membrane. The hydrophilic and hydrophobic properties of the membrane surface are characterized by the pure water contact angle of the membrane. Figure 5 (b) It can be seen that both PAN and MoS2@PAN are superhydrophilic membranes, which will be beneficial to their application in the field of water treatment. In addition, the introduction of MoS2 further shortens the time for the contact angle to drop to 0° by 3 s, which is attributed to the superhydrophilic property of flower-like MoS2.

[0071] Example 7

[0072] Since actual wastewater often contains a variety of coexisting substances, and membrane materials are extremely sensitive to substances such as proteins and bacteria, long-term contact will affect the membrane's permeation resistance, resulting in a serious decrease in flux. Therefore, BSA, a typical pollutant used in the national standard to evaluate the membrane's anti-fouling performance, was used as a test pollutant to evaluate the anti-fouling performance of MoS2@PAN and compare it with the PAN matrix membrane. The results are shown in Figure 2. Figure 6 shown.

[0073] The anti-fouling performance test method is: using a BSA solution with a concentration of 1 g / L as the pollutant, the anti-fouling performance of the membrane is tested. The fouling performance of the BSA solution on the membrane is mainly evaluated by the degree of contamination, that is, the degree of pure water flux attenuation (FRR) of the membrane. Test pure water flux (J w1 ) was placed in a membrane flux meter to filter pure water, the pressure was maintained at 0.2 MPa for 2 h, and then 1 g / L BSA solution was used as the influent, and the water flux of the BSA solution (J) was obtained after filtration for 1 h. P Finally, the contaminated membrane was washed with deionized water to remove the retained BSA, and the pure water flux of the washed membrane was tested again, which was the recovery flux (J w2 ).

[0074] FRR is calculated as follows:

[0075] ;

[0076] In order to further analyze the anti-fouling performance of the membrane, the total fouling ratio (R t ), reversible pollution ratio (R r ) and irreversible pollution ratio (R ir ) and other parameters describe the fouling resistance of the membrane. The corresponding calculation formula is as follows:

[0077] .

[0078] Depend on Figure 6 (a) It can be seen that the water flux of both materials decreased significantly after BSA was added. This is because the membrane itself has a small pore size and can intercept BSA through physical sieving. After BSA contamination, the membrane was taken out and ultrasonic vibration and backwashing were performed. The membrane flux recovery rate (FRR) of MoS2@PAN increased from 60% of the PAN matrix membrane to 90%, because MoS2@PAN has higher hydrophilicity.

[0079] Depend on Figure 6 (b) It can be seen that MoS2@PAN has a lower R than PAN. t and higher R r , and R ir The concentration of BSA in the membrane was significantly reduced to 14%, indicating that it has excellent anti-pollution ability. This excellent anti-pollution property comes from the following two aspects: (1) BSA pollutants are negatively charged, and the surface of the MoS2@PAN membrane is negatively charged. The two have strong electrostatic repulsion, which can effectively reduce membrane pollution; (2) Figure 1 From the SEM image, it can be seen that the doping of MoS2 causes the surface morphology to become rough, and the uneven structure is more conducive to BSA being retained on the membrane surface, making BSA easy to remove by simple backwashing.

[0080] Depend on Figure 7 (a) It can be seen that the best removal effect of MoS2@PAN on Cr(VI) occurs at pH=2, and the removal rate of Cr(VI) decreases with the increase of pH. This pH change trend is related to the morphology of Cr(VI) at different pH values ​​and the surface charge of the membrane material. In the pH range of 2~6, Cr(VI) exists in the form of HCrO4 − and Cr2O7 − As the pH rises to greater than 6, CrO4 2- Increases and dominates. Due to HCrO4 − The free energy required to complete adsorption is lower,

[0081] Therefore, MoS2@PAN has a better removal ability at pH = 2. In addition, the reason for the higher removal efficiency under low pH conditions is also related to the surface charge of the MoS2@PAN composite membrane material. Figure 7 (b) It can be seen that MoS2@PAN carries negative charge in the pH range of 2~11, but due to the influence of protonation under acidic conditions, the negative charge carried on the surface gradually decreases with the decrease of pH, and is close to the zero charge point at pH=2. The repulsion effect with negatively charged Cr(VI) is weakened, and the composite film can contact more Cr(VI).

[0082] Example 8

[0083] The MoS2@PAN composite membrane material prepared in Example 1 was subjected to isothermal adsorption experiments under different temperature conditions. The results are as follows Figure 8 As shown. Figure 8 It can be seen that with the increase of temperature, the adsorption amount of MoS2@PAN on Cr(VI) gradually increases, and the adsorption process is an endothermic reaction. The experimental results were fitted and analyzed by the Langmuir and Freundlich models, and the calculation results are shown in Table 2.

[0084] Table 2 Fitting parameters of the adsorption isotherm of MoS2@PAN for Cr(VI) at different temperatures

[0085]

[0086] As shown in Table 2, at 298 K, 308 K and 318 K, the fitting coefficients of the Freundlich model are higher than those of the Langmuir model, indicating that the Freundlich adsorption model can be better used to describe the adsorption behavior of MoS2@PAN on Cr(VI). The Freundlich model indicates the heterogeneity of the adsorption system and the multilayer adsorption phenomenon. Therefore, the adsorption process of MoS2@PAN on Cr(VI) is a non-uniform multilayer chemical adsorption on the surface.

[0087] The experimental results were fitted and analyzed using pseudo-first-order and pseudo-second-order kinetic models. The fitting curves are shown in Fig. 9 .Depend on Fig. 9 It can be seen that the fitting results of the two kinetic models are significantly different. The fitting degree of the pseudo-second-order kinetic model (R 2 ) is much higher than the pseudo-first-order model, indicating that the adsorption process of MoS2@PAN on Cr(VI) is mainly chemical adsorption.

[0088] Example 9

[0089] The MoS2@PAN composite film material prepared in Example 1 was subjected to a coexisting ion effect experiment. The results are as follows: Figures 10-12 shown.

[0090] Depend on Fig.10 It can be seen that as the anion (SO4 2- 、NO3 - , Cl - ) concentration increased, the removal capacity of MoS2@PAN for Cr(VI) decreased, especially SO4 2- The biggest impact, Cl - Next is NO3 - The effect is minimal, which is related to the degree of negative charge carried by the anion and the radius of the hydrated ion. - and NO3 - is a low affinity ligand and forms a weak outer complex. In contrast, SO4 2- It will occupy some of the adsorption sites and form inner layer complexes, thereby reducing the removal efficiency of Cr(VI).

[0091] The common cations in wastewater (Ca 2+ Mg 2+ 、Ni 2+ 、Na + , Cu 2+ ) as interfering ions to evaluate the effect of MoS2@PAN on the treatment of Cr(VI) in a system where metal cations coexist. The results are shown in Fig.11 .Depend on Fig.11 (a) It can be seen that the removal performance of the composite adsorption membrane for Cr(VI) in the Cr(VI)-metal cation binary system is that the MoS2@PAN composite membrane maintains a stable treatment effect, and the reduction in treatment capacity does not exceed 7.5%. 2+ The removal effect of Cr(VI) was significantly enhanced when it coexists with Cr(VI). When the molar ratio reached Cr:Cu=1:2, the removal rate increased from 40% to 100%. 2+ Mg 2+ 、Ni 2+ 、Na+ , Cu 2+ Five kinds of metal ions were mixed to verify the removal effect of each ion in the mixed system. The results are as follows Fig.11 As shown in (b), consistent with the binary system, MoS2@PAN in the mixed system of six metal ions still exhibits enhanced Cr(VI) removal.

[0092] The removal effect of MoS2@PAN on the coexistence system of Cr(VI) and organic acid was evaluated by taking ethylenediaminetetraacetic acid (EDTA), tannic acid (TA), oxalic acid (OA) and citric acid (CA) as examples. Fig.12 It can be seen that different organic acid systems have no significant effect on the removal of Cr(VI), and the removal efficiency is higher than 95%, which further shows that MoS2@PAN has a general anti-organic acid interference property for the removal of Cr(VI).

[0093] Example 10

[0094] Inorganic salts and other interfering ions were added to the wastewater containing Cr(VI) to simulate the actual wastewater: the solution was pumped into the ultrafiltration cup, and the negative pressure was generated by the peristaltic pump to pump the solution from one end of the membrane to the other end; the Cr(VI) solution was pumped into the ultrafiltration cup (YL-50) with the breakthrough point of 0.5 mg / L in the Integrated Wastewater Discharge Standard (GB8978-1996), and the outlet flow rate was controlled at 15.7 L·m -2 ·h -1 , collect samples every 30 min, such as Fig.13 shown.

[0095] Depend on Fig.13 It can be seen that when the breakthrough point is set to 0.5 mg / L, even in the presence of interfering ions, MoS2@PAN still exhibits a 6000 L / m 2 The effective treatment capacity of Cr(VI) was almost not detected in the first 3000 mL of effluent, and the effluent was stably lower than the strict standard of 0.05 mg / L in the "Sanitary Standard for Drinking Water" (GB 5749-2022), proving that the MoS2@PAN composite adsorption membrane has good applicability in the deep purification of chromium-containing wastewater.

[0096] Embodiment 11

[0097] A static-cyclic adsorption-desorption experiment was carried out on the MoS2@PAN composite adsorption film prepared in Example 1, and each adsorption-desorption was regarded as one cycle.

[0098] Depend on Fig.14(a) It can be seen that the material can be effectively regenerated by using a 0.5 M dilute HCl solution, and the removal amount of MoS2@PAN remained stable in the first five rounds, and showed a slight downward trend after the sixth round. The removal rate in the tenth round only decreased by 8%, indicating that MoS2@PAN has good reusability, which greatly reduces its use cost.

[0099] Depend on Fig.14 (b) It can be seen that under acidic conditions, only extremely low Mo ions were detected in the solution, which is far below the drinking water and local emission standards, proving that MoS2@PAN has excellent stability.

[0100] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a MoS2@PAN composite adsorption film, characterized in that: MoS2 nanoparticles were encapsulated in the PAN membrane matrix via a non-solvent induced phase separation method to prepare the MoS2@PAN composite adsorption film.

2. The method for preparing the MoS2@PAN composite adsorption film according to claim 1, characterized in that: The specific steps include: 1) Dissolve PAN powder and PEG in DMF and react in a water bath to obtain PAN casting solution; 2) adding MoS2 nanoparticles to the PAN casting solution prepared in step 1), and removing residual bubbles by ultrasonication to obtain MoS2@PAN casting solution; 3) Pour the MoS2@PAN casting solution obtained in step 2) onto a glass plate and scrape the film. After standing in the air, immerse the glass plate in ultrapure water and solidify to obtain a MoS2@PAN composite adsorption film.

3. The method for preparing the MoS2@PAN composite adsorption film according to claim 2, characterized in that: In the step 1), the mass ratio of PAN powder to PEG is 20:11.

9.

4. The method for preparing the MoS2@PAN composite adsorption film according to claim 2, characterized in that: In the step 3), the film is scraped to form a film with a thickness of 200 μm.

5. The method for preparing the MoS2@PAN composite adsorption film according to claim 2, characterized in that: In the step 2), the preparation process of MoS2 nanoparticles is as follows: and CH4N2S were dissolved in deionized water, and the obtained mixed solution was placed in a stainless steel high-pressure reactor lined with polytetrafluoroethylene for reaction. After the reaction was completed, the reactor was cooled to room temperature, the product was washed to neutrality, and then freeze-dried to obtain MoS2 nanoparticles.

6. The method for preparing the MoS2@PAN composite adsorption film according to claim 5, characterized in that: The reaction temperature is 180° C. and the reaction time is 20 h.

7. The method for preparing the MoS2@PAN composite adsorption film according to claim 2, characterized in that: In the step 2), the g / mL ratio of MoS2 nanoparticles to PAN casting solution is 4:

30.

8. The method for preparing the MoS2@PAN composite adsorption film according to claim 2, characterized in that: In the step 1), the temperature of the water bath reaction is 65° C. and the reaction time is 8 h.

9. The method for preparing the MoS2@PAN composite adsorption membrane according to any one of claims 1 to 8, wherein the MoS2@PAN composite adsorption membrane is prepared.

10. Use of the MoS2@PAN composite adsorption membrane according to claim 9 in treating Cr(VI)-containing wastewater.

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