Method for removing arsenic in water body

Abstract

The invention discloses a method for removing arsenic in a water body. The method for removing the arsenic in the water body comprises the following steps: adding a metal organic framework material NO2-MIL-101 (Fe) into the water body to be treated, and stirring to adsorb arsenic ions so as to remove the arsenic in the water body. By optimizing a nitro ligand structure and surface properties of the MIL-101, the adsorption performance of the MIL-101 on arsenic pollutants is remarkably improved, so that an efficient water treatment effect is realized. The material disclosed by the invention is simple and convenient in synthesis process, low in energy consumption, easily available in raw materials and free of toxic by-products, and accords with the principle of green sustainable development. The material developed by the invention is expected to become an ideal choice for arsenic pollution treatment in the field of water treatment, and an efficient, economic and environment-friendly solution is provided for practical application.

Description

Technical Field

[0001] The present invention belongs to the technical field of water treatment, and particularly relates to a method for removing arsenic from water bodies. Background Art

[0002] Arsenic (As) is a common metalloid element, which has attracted much attention due to its wide distribution, diverse forms of existence and high toxicity. The World Health Organization (WHO) has listed arsenic as a class I carcinogen, and long-term exposure will pose a major threat to human health and the environment. Long-term drinking of arsenic-contaminated groundwater may lead to various cancers such as skin lesions, lung cancer, bladder cancer, and liver cancer, and may also cause nervous system damage, cardiovascular diseases, and intellectual development problems, which is particularly unfavorable to the health of children. Therefore, there is an urgent need to develop efficient arsenic-removing materials to remove arsenic from water bodies such as surface water, groundwater, and raw drinking water.

[0003] Currently, the adsorbents commonly used for arsenic removal include zeolite, activated alumina, activated carbon, fly ash, red mud, iron oxide, and zero-valent iron. However, the adsorption capacities of the above traditional adsorption materials are generally low. For example, the adsorption capacities of granular activated carbon and activated alumina are usually less than dozens of mg / g, and the adsorption equilibrium time is long, usually greater than 12 hours. Therefore, the adsorption rate, adsorption capacity, and applicable pH value range of the adsorbent for arsenic removal need to be further improved and expanded.

[0004] Metal-organic framework materials (MOFs) are a class of porous materials formed by the coordination of metal ions or metal clusters with organic ligands. MIL-101(Fe) has become a current research hotspot due to its advantages such as simple synthesis, low energy consumption, strong stability, easy adjustment and functionalization. Therefore, how to modify the functional groups of MIL-101(Fe) nanomaterials to obtain a water body arsenic adsorbent with high adsorption rate and adsorption capacity has important research significance. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for removing arsenic from water bodies. This method uses NO2-MIL-101 for water treatment, and shows more excellent removal effects on As(III) and As(V) in water bodies compared with MIL-101(Fe), especially the removal effect of As(V) is significantly better than that of MIL-101.

[0006] A method for removing arsenic from water bodies provided by the present invention includes the following steps:

[0007] Add the metal-organic framework material NO2-MIL-101(Fe) to the water body to be treated, and stir to adsorb arsenic ions to achieve the removal of arsenic in the water body.

[0008] Based on the above technical solutions, the present invention uses the metal-organic framework material NO2-MIL-101(Fe) as an adsorbent for arsenic in water. The adsorption amount of NO2-MIL-101 for removing arsenic ions in water almost approaches equilibrium after 0.5 hours, showing a very fast adsorption rate, and the adsorption capacity is as high as 155.6 mg / g As(III) and 118.8 mg / g As(V). For As(III), when the pH value is between 7 and 8, the removal rate of NO2-MIL-101 can reach 65%; for As(V), when the pH value is in the range of 4 to 6, the removal rate of NO2-MIL-101 is the highest, reaching 95%.

[0009] For the above method for removing arsenic in water, further, the water body includes any one of surface water, groundwater, and drinking water source water. In the present invention, the surface water refers to natural or artificial surface water sources such as rivers, lakes, and reservoirs. The groundwater includes underground water sources such as well water and spring water. The raw drinking water is the raw water before being treated by a water treatment plant.

[0010] For the above method for removing arsenic in water, further, 0.1 - 1.0 mg of the metal-organic framework material NO2-MIL-101(Fe) is added to every 1 mL of the water body, preferably 0.2 - 0.5 mg / mL, and more preferably 0.25 mg / mL.

[0011] For the above method for removing arsenic in water, further, the arsenic ions are arsenite ions As(III) and / or arsenate ions As(V), each existing in the form of arsenite and arsenate, such as sodium arsenite and sodium arsenate.

[0012] For the above method for removing arsenic in water, further, the concentration of arsenite ions As(III) in the water body is 1 - 150 mg / L, such as 10 - 150 mg / L, including but not limited to 10, 15, 20, 30, 40, 50, 75, 100, 125, 150, 175 mg / L, preferably 30 mg / L;

[0013] The concentration of arsenate ions As(V) in the water body is 1 - 60 mg / L, such as 10 - 60 mg / L, including but not limited to 10, 15, 20, 25, 30, 40, 50, 60 mg / L, preferably 30 mg / L.

[0014] In the present invention, when the pH value of the water body is 7.0 ± 0.1, the isothermal adsorption curve shows that when the initial concentration of As(III) is 175 mg / L, the adsorption capacity of NO2-MIL-101 is 155.6 mg / g; when the initial concentration of As(V) is 60 mg / L, the adsorption capacity of NO2-MIL-101 is 118.8 mg / g.

[0015] In the present invention, when the initial pH value of the water body is 7.0 ± 0.1, kinetic data shows that when the initial concentration of As(III) is 30 mg / L, MIL-101 can remove approximately 23% of arsenite ions after 30 minutes, while the removal rate of NO2-MIL-101 exceeds 40%; for As(V), MIL-101 can adsorb approximately 70% of arsenate ions within 30 minutes, while NO2-MIL-101 can remove approximately 90% of arsenate ions.

[0016] For the above method for removing arsenic in water, further, the rotation speed of the stirring is 10 - 120 rpm, such as 60 rpm.

[0017] For the above method for removing arsenic in water, further, the adsorption is carried out at 10 - 30 °C, such as 25 °C;

[0018] The adsorption time is 0.5 - 1 h, and can be specifically determined according to the change in the adsorption capacity. The adsorption capacity of NO2-MIL-101 for removing arsenic ions in water almost approaches equilibrium after 0.5 hours, showing a very fast adsorption rate.

[0019] For the above method for removing arsenic in water, further, the arsenic ion is arsenite ion As(III), and the method further includes the step of adjusting the pH value of the water body to 7 - 8;

[0020] The arsenic ion is arsenate ion As(V), and the method further includes the step of adjusting the pH value of the water body to 4 - 6.

[0021] For the above method for removing arsenic in water, further, the water body contains NaCl, such as 0.05 M NaCl.

[0022] For the above method for removing arsenic in water, further, the preparation method of the metal-organic framework material NO2-MIL-101(Fe) includes the following steps:

[0023] S1. Drop the organic solution of 2-nitroterephthalic acid into the organic solution of ferric salt to obtain a mixed solution;

[0024] S2. Carry out a solvothermal reaction on the mixed solution to obtain the metal-organic framework material NO2-MIL-101(Fe).

[0025] Furthermore, the solvents of the organic solution of 2-nitroterephthalic acid and the organic solution of ferric salt are N,N-dimethylformamide (DMF); as an example, the molar ratio of 2-nitroterephthalic acid to ferric salt is 1:2; the ferric salt can specifically be FeCl3·6H2O;

[0026] The temperature of the solvothermal reaction is 100 - 120 °C (such as 110 °C), and the reaction time is 20 - 24 hours (such as 24 hours); as an example, after the solvothermal reaction, the method further includes: First, centrifuge the reaction system at 10,000 rpm for 15 minutes, then wash it successively with DMF solution and methanol solution, and finally dry it under vacuum at 80 °C for 24 hours. The dried powder is ground through a 100-mesh sieve for standby.

[0027] The present invention has the following beneficial effects:

[0028] (1) Experimental results show that for the material MIL-101, the adsorption equilibrium can be reached after 24 hours of adsorption in an As(III) solution with an initial concentration of 175 mg / L, and the adsorption capacity is as high as 170.8 mg / g; in an As(V) solution with an initial concentration of 60 mg / L, the adsorption capacity is as high as 124.8 mg / g; for NO2-MIL-101, its adsorption capacity for As(III) can reach 155.6 mg / g and for As(V) can reach 118.8 mg / g under the same conditions. The above results indicate that both MIL-101 and NO2-MIL-101 have excellent adsorption performance and can efficiently and rapidly remove arsenic pollutants in water.

[0029] (2) Experimental results show that in a solution with an initial concentration of both As(III) and As(V) of 30 mg / L, the removal rate of As(III) by MIL-101 can reach 20% after 30 minutes, while the removal rate of As(V) is close to 70%. In contrast, NO2-MIL-101 shows a more excellent removal effect. The removal rate of As(III) is close to 40% after 30 minutes, and the removal rate of As(V) is as high as 90%. These results indicate that NO2-MIL-101 can remove arsenic pollutants in water more efficiently in a short time, especially the removal effect of As(V) is significantly better than that of MIL-101.

[0030] (3) The present invention conducted pH edge experiments on MIL-101 and NO2-MIL-101. The experiments were carried out in the pH range from 3 to 11 with an initial arsenic concentration of 30 mg / L. For As(III), when the pH value was between 7 and 8, the removal rate of NO2-MIL-101 could reach 65%; while at pH = 8, the removal rate of MIL-101 was the highest, reaching 73%. Under other pH conditions, the removal rate of MIL-101 was lower than that of NO2-MIL-101. For As(V), when the pH value was in the range of 4 to 6, the removal rate of NO2-MIL-101 was the highest, up to 95%; while the removal rate of MIL-101 was the highest at pH = 4, reaching 97%. These experimental results indicate that the pH value has a significant impact on the adsorption performance of the materials, and the removal effects of the two materials are different under different pH conditions, showing the adaptability of the materials under different water quality conditions. The water treatment method using NO2-MIL-101 in the present invention preferably has a pH value of the water body of 7 - 8 or 4 - 6, which can be specifically selected according to the type of arsenic ion.

[0031] In summary, by optimizing the nitro ligand structure and surface properties of MIL-101, the present invention significantly improves its adsorption performance for arsenic pollutants, thereby achieving an efficient water treatment effect. The material synthesis process involved in the present invention is simple, has low energy consumption, the raw materials are easily available and there are no toxic by-products, which conforms to the principle of green and sustainable development. The materials developed in the present invention are expected to become an ideal choice for the treatment of arsenic pollution in the water treatment field, providing an efficient, economical and environmentally friendly solution for practical applications. Brief Description of the Drawings

[0032] Figure 1 Shows the Fourier transform infrared spectroscopy (FTIR) spectra of MIL-101 and NO2-MIL-101 in Example 2.

[0033] Figure 2 Shows the BET specific surface area test results of MIL-101 and NO2-MIL-101 in Example 2.

[0034] Figure 3 Shows the pore size distribution diagrams of MIL-101 and NO2-MIL-101 in Example 2.

[0035] Figure 4 Shows the thermogravimetric analysis (TGA) curves of MIL-101 and NO2-MIL-101 in Example 2.

[0036] Figure 5 Shows the adsorption isotherms of MIL-101 and NO2-MIL-101 for As(III) in Example 3.

[0037] Figure 6Shows the adsorption isotherms of As(V) by MIL-101 and NO2-MIL-101 in Example 3.

[0038] Figure 7 Shows the removal adsorption kinetic curves of As(III) by MIL-101 and NO2-MIL-101 in Example 4.

[0039] Figure 8 Shows the removal adsorption kinetic curves of As(V) by MIL-101 and NO2-MIL-101 in Example 4.

[0040] Figure 9 Shows the removal rate curves of As(III) by MIL-101 and NO2-MIL-101 under different pH conditions in Example 5.

[0041] Figure 10 Shows the removal rate curves of As(V) by MIL-101 and NO2-MIL-101 under different pH conditions in Example 5.

[0042] Figure 11 Shows the ζ-potential change curves of MIL-101 before and after adsorbing As(III&V) in Example 5.

[0043] Figure 12 Shows the ζ-potential change curves of NO2-MIL-101 before and after adsorbing As(III&V) in Example 5. Detailed implementation manners

[0044] The present invention will be further described in detail below in conjunction with the specific implementation manners. The given examples are only for clarifying the present invention, rather than limiting the scope of the present invention. The following provided examples can be used as a guide for those of ordinary skill in the art to make further improvements, and do not limit the present invention in any way.

[0045] The methods used in the following examples are all conventional methods, unless otherwise specified, and are carried out according to the techniques or conditions described in the literature in this field or according to the product instructions. The materials, reagents, etc. used in the following examples can be obtained from commercial channels, unless otherwise specified. Specifically, FeCl3·6H2O, H2BDC, 2-nitroterephthalic acid, DMF, methanol, HCl, NaCl, etc. are all analytical pure reagents and meet the experimental requirements.

[0046] Example 1. Synthesis and preparation of MIL-101 and NO2-MIL-101

[0047] The synthesis method of MIL-101 is as follows: Dissolve FeCl3·6H2O (7.5 mmol, 2.025 g) and H2BDC (3.75 mmol, 0.618 g) separately in 30 mL of DMF, and use ultrasonic treatment for about 30 minutes until the solution becomes clear and transparent. Subsequently, dropwise add the DMF solution of terephthalic acid into the DMF solution of ferric chloride to obtain a uniform mixed solution. Transfer this solution to a Teflon autoclave, set the reaction temperature at 110 °C, and the reaction time at 24 hours. After the reaction, wait for the autoclave to cool naturally to room temperature, and separate it using a high-speed centrifuge at 10000 rpm for 15 minutes. Wash the MIL-101 powder 3 times with 200 mL of DMF solution until the washing liquid becomes clear, and then wash and activate the powder 3 times with 200 mL of methanol solution. Finally, place the powder in a vacuum oven and dry it at 80 °C for 24 hours. The dried powder is ground through a 100-mesh sieve for standby.

[0048] The synthesis method of NO2-MIL-101 is similar to the above, only replacing H2BDC (3.75 mmol, 0.618 g) with 2-nitroterephthalic acid (3.75 mmol, 0.791 g).

[0049] Example 2. Infrared spectroscopy, nitrogen adsorption and thermogravimetric analysis characterization of MIL-101 and NO2-MIL-101

[0050] Take about 4 mg of the MIL-101 and NO2-MIL-101 samples prepared in Example 1, and mix them with an appropriate amount of KBr according to a mass ratio of 1:100, and use the KBr tablet pressing method to prepare sample tablets. Subsequently, use a Fourier transform infrared spectrometer (FTIR) to analyze the functional groups of the two materials, and the test results are as Figure 1 shown.

[0051] Through FTIR analysis, the characteristic spectral peaks of MIL-101 show C-H vibration at 750 cm-1, C-O-C vibration at 1020 cm-1, symmetric vibration of O-C=C at 1390 cm-1, antisymmetric vibration of O-C=O at 1582 cm-1, and C=O vibration at 1702 cm-1. For NO2-MIL-101, the characteristic spectral peaks show antisymmetric vibration of the nitro group at 1535 cm-1 and symmetric vibration of the nitro group at 1345 cm-1. The FTIR spectral peaks indicate that a nitro functional group has been successfully introduced on the basis of MIL-101, verifying the functionalization characteristics of NO2-MIL-101 and providing structural support for its application in adsorption and other fields.

[0052] Take approximately 100 mg of the MIL-101 and NO2-MIL-101 samples prepared in Example 1 and test them respectively through a specific surface area analyzer (BET) to evaluate their specific surface area, pore size distribution, and other pore structure characteristics. The test results are as Figure 2 and Figure 3 shown.

[0053] Through BET analysis, the specific surface area of NO2-MIL-101 is 254.3 m 2 / g, which is higher than 177.2 m 2 / g of MIL-101, indicating that NO2-MIL-101 has higher surface activity and more available surface area. The pore size distribution results show that both are typical microporous materials with a small pore size range, which helps to improve their performance in adsorption reactions. The above results show that MIL-101 and NO2-MIL-101 are significantly superior to traditional materials in terms of specific surface area and exhibit ideal microporous characteristics in the pore structure, further verifying their great potential in efficient adsorption applications.

[0054] Take approximately 10 mg of the MIL-101 and NO2-MIL-101 samples prepared in Example 1 and test their thermal stability through a thermogravimetric analyzer (TGA). The test results are as Figure 4 shown. Thermogravimetric analysis provides the mass change of the material under different temperature conditions and provides key data for further evaluating its thermal stability and high-temperature resistance performance.

[0055] The initial change trends of both are roughly the same. Between 20 °C and 150 °C, the mass loss is about 10%, which may be due to the volatilization of moisture and residual organic solvent molecules inside or on the surface of the pore framework. For MIL-101, the mass loss in the range of 150 °C to 400 °C is mainly due to the volatilization of guest molecules and unreacted products in the cage structure. After exceeding 450 °C, as H2BDC decomposes, the material mass tends to be stable and almost no significant change occurs. In contrast, NO2-MIL-101 shows a rapid mass decline at 320 °C, which may be related to the strong oxidizing property of its nitro group, resulting in an auto-oxidation reaction under high-temperature conditions. The thermogravimetric analysis results show that although there are certain differences in the performance of the two materials under temperature changes, both show good thermal stability, sufficient to cope with the temperature and environmental conditions in most water treatment projects.

[0056] Example 3. Study on the adsorption capacities of MIL-101 and NO2-MIL-101 for As(III) and As(V)

[0057] Take about 10 mg of the MIL-101 and NO2-MIL-101 samples prepared in Example 1 and place them separately in 40 mL of an aqueous solution containing 10 - 175 mg / L of sodium arsenite (As(III)) (i.e., NaAsO2 solutions with initial concentrations of 10, 15, 20, 30, 40, 50, 75, 100, 125, 150, and 175 mg / L) and 40 mL of an aqueous solution containing 10 - 60 mg / L of sodium arsenate (As(V)) (i.e., Na3AsO4 solutions with concentrations of 10, 15, 20, 25, 30, 40, 50, and 60 mg / L). Add 0.05 M NaCl as a background ion to each of the two solutions with different initial concentrations. Use hydrochloric acid and sodium hydroxide to adjust the pH value of the solution to 7.0 ± 0.1. Subsequently, place the solution in a rotary stirrer, keep it at room temperature, with a rotation speed of 60 rpm, and check and adjust the pH value every 4 to 6 hours to ensure it remains stable at 7.0 ± 0.1. After the pH value stabilizes, continue rotating for 24 hours to ensure sufficient adsorption.

[0058] After the adsorption is completed, filter the adsorption solution using a 0.22-micron filter membrane and determine the remaining arsenic concentration by inductively coupled plasma atomic emission spectrometry (ICP-OES). The results are as Figure 5 and Figure 6 shown. The isothermal adsorption curves indicate that when the initial concentration of As(III) is 175 mg / L, the adsorption capacity of MIL-101 reaches up to 170.8 mg / g at adsorption saturation, while that of NO2-MIL-101 is 155.6 mg / g; when the initial concentration of As(V) is 60 mg / L, the adsorption capacity of MIL-101 is 124.8 mg / g, and that of NO2-MIL-101 is 118.8 mg / g.

[0059] The above adsorption isotherm data were fitted with the Langmuir and Freundlich adsorption models. The results show that the adsorption process of MOFs for arsenic better conforms to the Langmuir model, as Figure 5 and Figure 6 shown. In the Langmuir model fitting, the linear correlation coefficients (R 2 ) of the adsorption isotherms of MIL-101 and NO2-MIL-101 for As(III) are 0.984 and 0.939, respectively; for the adsorption isotherm of As(V), R 2 are 0.880 and 0.524, respectively. The Langmuir isothermal adsorption model can well fit the measured adsorption isotherms, indicating that the adsorbate shows monolayer adsorption on the adsorbent surface, and the adsorption on the adsorbent surface is uniform, and there is no significant interaction between the adsorbates.

[0060] Example 4. Kinetic Study on the Adsorption of As(III&V) by MIL-101 and NO2-MIL-101

[0061] In clean beakers, prepare certain amounts of aqueous solutions of 30 mg / L sodium arsenite (As(III)) and 30 mg / L sodium arsenate (As(V)) respectively, and adjust the pH value of the initial solutions to 7.0 ± 0.1 using hydrochloric acid and sodium hydroxide respectively. Add 0.05 M NaCl as background ions to both solutions. Then, add magnetic rotors respectively and place the solutions on a magnetic stirrer (rotation speed: 60 rpm). Quickly add 0.25 mg / mL of the MIL-101 and NO2-MIL-101 samples prepared in Example 1 respectively and start timing. Take samples at 0, 1, 2, 4, 6, 8, 10, 12, 15, 20, and 30 minutes. Filter the adsorption solution using a 0.22 μm filter membrane and determine the remaining arsenic concentration by ICP-OES. The experimental results are as Figure 7 and Figure 8 shown.

[0062] The kinetic data show that when the initial concentration of As(III) is 30 mg / L, MIL-101 can remove approximately 23% of arsenite ions after 30 minutes, while the removal rate of NO2-MIL-101 exceeds 40%; for As(V), MIL-101 can adsorb approximately 70% of arsenate ions within 30 minutes, while NO2-MIL-101 can remove approximately 90% of arsenate ions.

[0063] Fit the above kinetic data with the pseudo-first-order kinetic model and the pseudo-second-order kinetic model. The results show that the data are more in line with the pseudo-second-order kinetic model. The fitting results are as Figure 7 and Figure 8 shown. In the fitting of the pseudo-second-order kinetic model for the adsorption of As(III), the linear correlation coefficients R 2 of MIL-101 and NO2-MIL-101 are 0.975 and 0.996 respectively; while for the adsorption of As(V), the R 2 of the fitting results are 0.998 and 0.967 respectively. These results indicate that the pseudo-second-order adsorption kinetic model can well fit the adsorption kinetic experimental data, and the reaction rate is linearly related to the adsorbate concentration, indicating that the adsorption process is mainly controlled by chemical actions or chemical reactions, and may involve mechanisms such as chemisorption and ion exchange.

[0064] Example 5. pH Edge Experiment on the Adsorption of As(III&V) by MIL-101 and NO2-MIL-101

[0065] Take 10 mg of the MIL-101 and NO2-MIL-101 samples prepared in Example 1 and place them separately in an aqueous solution containing 40 mL of 30 mg / L sodium arsenite (As(III)) and an aqueous solution containing 40 mL of 30 mg / L sodium arsenate (As(V)). Use hydrochloric acid and sodium hydroxide to adjust the pH value of the solution to 3, 4, 5, 6, 7, 8, 9, 10, and 11. Add 0.05 M NaCl as a background ion to each of the two solutions at each pH value. Subsequently, place the solution in a rotary stirrer, keep it at room temperature, with a rotation speed of 60 rpm, and check and adjust the pH value every 4 - 6 hours to ensure that it is stable within the range of the preset value ±0.1. After the experiment continues until the pH value is stable, continue to rotate for 24 hours to ensure sufficient adsorption. After adsorption is completed, filter the adsorption solution using a 0.22-micron filter membrane and measure the remaining arsenic concentration by ICP-OES. The results are as Figure 9 and Figure 10 shown.

[0066] The data show that for As(III), when the pH value is between 7 and 8, the removal rate of NO2-MIL-101 can reach 65%; while at pH = 8, the removal rate of MIL-101 is the highest, reaching 73%. Under other pH conditions, the removal rate of MIL-101 is lower than that of NO2-MIL-101. For As(V), when the pH value is in the range of 4 to 6, the removal rate of NO2-MIL-101 is the highest, reaching 95%; while the removal rate of MIL-101 is the highest at pH = 4, reaching 97%.

[0067] To further explore the adsorption mechanism, Zeta potential (ζ-potential) tests were carried out using a laser particle size analyzer. By measuring the Zeta potential of MIL-101 and NO2-MIL-101 under different pH conditions, the charge characteristics of the material surface were evaluated to gain an in-depth understanding of their interaction with arsenic ions. The Zeta potential reflects the intensity and nature of the surface charge of the material, thus affecting the electrostatic interaction between the adsorbate and the adsorbent surface during the adsorption process.

[0068] The test results are as Figure 11 and Figure 12As shown. Under low pH conditions, both MIL-101 and NO2-MIL-101 exhibit strong positive charges, and the surface charge gradually turns into negative charges as the pH value increases. Specifically, when pH < 8, that is, on the left side of the isoelectric point (PZC), the Zeta potential of MIL-101 is always positive, indicating that its surface carries a significant positive charge. Since the adsorbed arsenic species (As(III) and As(V)) are both negatively charged ions, it can be inferred that when MIL-101 adsorbs arsenic species, the isoelectric point shifts to the left, indicating that an inner layer complex structure is formed during the adsorption process, reflecting the characteristics of chemical adsorption. Similarly, NO2-MIL-101 also exhibits a similar adsorption mechanism, that is, chemical adsorption is achieved through an inner layer complex structure. More significantly, NO2-MIL-101 exhibits a stronger positive charge than MIL-101 at pH < 8, which means that NO2-MIL-101 has a stronger electrostatic interaction during the adsorption process. This enhanced electrostatic interaction makes the mutual attraction between NO2-MIL-101 and negatively charged arsenate ions stronger, which is conducive to the adsorption and removal of arsenic. Therefore, NO2-MIL-101 shows a faster adsorption trend in kinetics.

[0069] In summary, combined with the previous adsorption kinetics results, Zeta potential analysis further supported the adsorption mechanism dominated by chemical adsorption and ion exchange.

[0070] The present invention has been described in detail above. For those skilled in the art, without departing from the purpose and scope of the present invention, can implement the present invention in a wider range under equivalent parameters, concentrations and conditions. Although the present invention provides specific embodiments, it should be understood that the present invention can be further improved. In a word, according to the principle of the present invention, the application is intended to include any changes, uses or improvements to the present invention, including departing from the disclosed scope in the application and the changes made with conventional techniques known in the art.

Claims

1. A method for removing arsenic from water, characterized in that: The steps include: The metal organic framework material NO2-MIL-101 (Fe) is added to the water body to be treated, and stirred to adsorb arsenic ions, so as to remove arsenic in the water body.

2. The method for removing arsenic from water according to claim 1, characterized in that: The water body includes any one of surface water, groundwater and raw drinking water.

3. The method for removing arsenic from water according to any one of claims 1 to 2, characterized in that: 0.1-1.0 mg of the metal organic framework material NO2-MIL-101 (Fe) is added to every 1 mL of the water, preferably 0.2-0.5 mg / mL, more preferably 0.25 mg / mL.

4. The method for removing arsenic from water according to any one of claims 1 to 3, characterized in that: The arsenic ions are arsenite ions As(III) and / or arsenate ions As(V).

5. The method for removing arsenic from water according to claim 4, characterized in that: The concentration of arsenite ion As(III) in the water body is 1 to 150 mg / L; The concentration of arsenate ions As(V) in the water body is 1-60 mg / L.

6. The method for removing arsenic from water according to any one of claims 1 to 5, characterized in that: The stirring speed is 10-120 rpm.

7. The method for removing arsenic from water according to any one of claims 1 to 6, characterized in that: The adsorption is carried out at 10-30°C; The adsorption time is 0.5 to 1 h.

8. The method for removing arsenic from water according to any one of claims 1 to 7, characterized in that: The arsenic ion is an arsenite ion As(III), and the method further comprises the step of adjusting the pH value of the water body to 7 to 8; The arsenic ion is an arsenate ion As(V), and the method further comprises the step of adjusting the pH value of the water body to 4-6.

9. The method for removing arsenic from water according to any one of claims 1 to 8, characterized in that: The preparation method of the metal organic framework material NO2-MIL-101 (Fe) comprises the following steps: S1, adding the organic solution of 2-nitroterephthalic acid dropwise to the organic solution of trivalent iron salt to obtain a mixed solution; S2. Subjecting the mixed solution to a solvothermal reaction to obtain the metal organic framework material NO2-MIL-101 (Fe).

10. The method for removing arsenic from water according to claim 9, characterized in that: The solvents of the organic solution of 2-nitroterephthalic acid and the organic solution of trivalent iron salt are both N,N-dimethylformamide; The temperature of the solvent thermal reaction is 100-120° C., and the reaction time is 20-24 hours.

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