Application of modified adsorption material in removal of perfluorinated compounds and preparation method of modified adsorption material

Abstract

The invention provides application of a modified adsorption material in removal of perfluorinated compounds and a preparation method of the modified adsorption material. According to the method, the to-be-treated water body containing the perfluorinated compound is mixed with the modified adsorption material, and the obtained mixed to-be-treated water body is treated by regulating and controlling reaction conditions, so that PFAS is removed, and the purified water body is obtained. The method disclosed by the invention is a process for treating PFAS based on layered bimetallic hydroxide efficient adsorption, and the method is relatively low in energy consumption and relatively low in process treatment cost; wherein the layered bimetal hydroxide material is a modified layered bimetal hydroxide material, the PFAS treatment capacity is remarkably improved, and the layered bimetal hydroxide material has a good application prospect in the field of wastewater treatment.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to the application of a modified adsorbent material in the removal of perfluorinated compounds and its preparation method. Background Technology

[0002] Perfluorinated compounds (PFAS) are a class of artificially synthesized organic compounds in which all hydrogen atoms bonded to carbon atoms are replaced by fluorine atoms and connected to hydrophilic groups such as carboxyl groups and sulfonic acid groups. Therefore, they have excellent properties such as hydrophobicity, oil repellency, high temperature resistance, and reduced water surface tension, and are widely used in industrial production and daily consumer products.

[0003] However, PFAS are a class of persistent organic pollutants. Due to their extremely high chemical stability and C–F bond energy, PFAS are difficult to degrade by light, chemical, or biological means, and can persist in the environment and organisms for a long time, posing hazards such as reproductive toxicity, endocrine disruption, hepatotoxicity, and immunotoxicity. Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) have been classified as Group 1 and Group 2B carcinogens by the International Agency for Research on Cancer, respectively. With the widespread use of PFAS, they enter the aquatic environment through various pathways, polluting rivers and lakes, and entering water sources via runoff. Traditional water treatment processes primarily target particulate matter and microorganisms, with limited removal capacity for PFAS, leading to their easy entry into drinking water systems and posing exposure risks to humans. Among existing treatment technologies, adsorption methods have been widely studied due to their simplicity and low cost, especially activated carbon adsorption, which has been practically applied. However, it suffers from limited adsorption capacity, susceptibility to interference from coexisting ions, and easy clogging of micropores by micelles.

[0004] Meanwhile, in wastewater treatment, due to the numerous substituents involved in perfluorinated compounds and the differences in their physicochemical properties, it is difficult to use a unified method for efficient removal. For example, in the wastewater treatment of perfluorinated compounds such as PFOA (perfluorooctanoic acid), PFOS (perfluorooctane sulfonic acid), and PFBA (perfluorobutyric acid), the differences in physicochemical properties dominated by molecular structure make it impossible to use a unified method for efficient removal, and the difficulty of impurity removal varies significantly. The core physicochemical differences among the three are concentrated in carbon chain length and hydrophobicity: PFOS and PFOA both contain long carbon chain structures with 8 carbon atoms, are highly hydrophobic, and have large molecular sizes, while PFBA contains only short carbon chains with 4 carbon atoms, is less hydrophobic, and has smaller molecular sizes. At the same time, the differences in the charged characteristics of the functional groups (sulfonic acid group for PFOS, carboxyl group for PFOA and PFBA) further affect the suitability for impurity removal. In terms of the choice of impurity removal methods, although all three rely on mainstream processes such as adsorption, advanced oxidation, and membrane separation, the process adaptability is significantly different: In adsorption treatment, PFOS and PFOA can be efficiently adsorbed by conventional activated carbon and other materials with strong hydrophobic effects, while PFBA, due to insufficient hydrophobicity, has weak adsorption forces, is easy to desorb and difficult to remove, becoming a major problem in the treatment of perfluorinated compounds.

[0005] Therefore, the development of adsorption materials that are both highly efficient and selective for the removal of various perfluorinated compounds has become a current research focus. Summary of the Invention

[0006] To overcome the problems in existing technologies, such as the inability to simultaneously and efficiently remove multiple perfluorinated compounds, and especially the difficulty in removing impurities from easily desorbed compounds, this paper provides an application of modified adsorbent materials in the removal of perfluorinated compounds and a method for their preparation. By utilizing the strong adsorption capacity of layered bimetallic hydroxides for PFAS and the control of the adsorption environment, PFAS can be removed efficiently and rapidly. This method is simple, energy-efficient, and has low processing costs, and can achieve efficient adsorption of multiple PFAS.

[0007] In a first aspect, the present invention provides an application of a modified adsorbent material in the removal of perfluorinated compounds, characterized in that the modified adsorbent material comprises a layered bimetallic hydroxide and nitric acid located between the layers of the layered bimetallic hydroxide; the volume-to-mass ratio of the nitric acid to the layered bimetallic hydroxide is (0.5~2) mL / g, and the metals in the layered bimetallic hydroxide are magnesium and aluminum;

[0008] In the modified adsorbent material, the molar ratio of metallic magnesium to metallic aluminum is 1:(0.3~0.7), for example 1:0.5; The median particle size of the modified adsorbent material is 1.0~6.0 μm; The modified adsorbent material has an average pore size of 12-14 nm.

[0009] Optionally, the nitric acid exists in the interlayer of the layered bimetallic hydroxide of the modified adsorbent material in the form of nitrate ions.

[0010] Optionally, the volume-to-mass ratio of the nitric acid to the layered bimetallic hydroxide is 1 mL / g.

[0011] Optionally, the specific surface area of ​​the modified adsorbent material is 14~20 m². 2 / g.

[0012] Optionally, the total pore volume of the modified adsorbent material is 0.04~0.05 cm³. 3 / g.

[0013] Optionally, the modified adsorbent material has anion exchange adsorption sites for adsorbing perfluorinated compounds.

[0014] Optionally, the modified adsorbent material is prepared by the following method: in the presence of a solvent, a layered bimetallic hydroxide undergoes an exchange reaction with a modifier to obtain the modified adsorbent material. The modifier is concentrated nitric acid. The solvent is methanol.

[0015] In one embodiment, the mass-to-volume ratio of the layered bimetallic hydroxide to the methanol is 1-15 g / L; preferably 5-10 g / L.

[0016] In one embodiment, the mass percentage of concentrated nitric acid is 60-75%, preferably 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75% or any two values, more preferably 68%.

[0017] In one embodiment, the mass-to-volume ratio of methanol to the modifier is (90~120):1; preferably (100~115):1; more preferably (100~110):1.

[0018] In one embodiment, the exchange reaction takes 10 to 30 hours, preferably 12 to 24 hours.

[0019] In one embodiment, the exchange reaction is carried out in the presence of an inert gas, preferably in an N2 atmosphere.

[0020] In one embodiment, the exchange reaction further includes the following post-processing steps: centrifuging the reaction solution to obtain a solid, washing, and drying.

[0021] In one embodiment, the cleaning is a conventional cleaning method in the art, preferably cleaning once with methanol.

[0022] In one embodiment, the drying is performed in an oven, preferably in an oven at 60°C.

[0023] Optionally, the exchange reaction further includes the preparation of the layered bimetallic hydroxide, which includes the following steps: mixing magnesium salt, aluminum salt and urea in a solvent to obtain a mixture, and carrying out a hydrothermal reaction of the mixture in a hydrothermal reactor to prepare the layered bimetallic hydroxide.

[0024] In one embodiment, the magnesium salt is magnesium nitrate and the aluminum salt is aluminum nitrate.

[0025] In one embodiment, the molar ratio of the magnesium salt to the aluminum salt is 1:(0.3~0.7); preferably 1:0.5.

[0026] In one embodiment, the total molar amount of the bimetallic salt and the molar ratio of the urea are 1:(4~5), preferably 1:4.5 or 3:14.

[0027] In one embodiment, the mixing is defined as the uniform mixing of all substances in the system.

[0028] In one embodiment, the temperature of the hydrothermal reaction is 100~150℃, preferably 120℃.

[0029] In one embodiment, the hydrothermal reaction takes 10-15 hours.

[0030] In one embodiment, the hydrothermal reaction further includes the following post-processing steps: cooling, separation, cleaning, and drying.

[0031] In this invention, the cleaning is a conventional cleaning method in the art, and the purpose of water washing is to remove large particles and residues of Na from the synthesis process. + CO3² - Impurity ions, etc.

[0032] In a preferred embodiment, it is preferable to first clean with water and then clean with ethanol.

[0033] In this invention, unless otherwise specified, the reaction temperature is room temperature, preferably 20~30℃.

[0034] Optionally, the perfluorinated compound includes at least one of perfluorooctanoic acid, perfluorooctyl sulfonic acid, perfluorobutyric acid, and perfluorohexane sulfonic acid.

[0035] Optionally, the application involves immersing the modified adsorbent material in the water to be treated for adsorption, thereby achieving effective removal of perfluoride.

[0036] Optionally, the application involves adding a pH adjuster to the water sample containing perfluorinated compounds to adjust the pH value of the water sample to 6.0~7.0.

[0037] Preferably, the pH adjuster includes an acidic adjuster and an alkaline adjuster; more preferably, the acidic adjuster includes at least one of hydrochloric acid, sulfuric acid, and nitric acid; and the alkaline adjuster includes at least one of sodium hydroxide, sodium carbonate, and lime.

[0038] Optionally, the dosage of the modified adsorbent material is 0.1~0.75 g / L; preferably 0.25~0.75 g / L, for example 0.1 g / L, 0.15 g / L, 0.2 g / L, 0.25 g / L, 0.3 g / L, 0.35 g / L, 0.4 g / L, 0.45 g / L, 0.5 g / L, 0.75 g / L or any range between the aforementioned two values.

[0039] Optionally, the concentration of perfluorinated compounds in the treated water is 100~1000 μg / L.

[0040] Optionally, the adsorption temperature is 20~25℃.

[0041] Optionally, the adsorption process requires stirring, and preferably, the stirring intensity is 150~200 r / min.

[0042] Optionally, the adsorbed material is separated from the treated water by filtration or centrifugation.

[0043] In a second aspect, the present invention provides a modified adsorbent material, characterized in that the modified adsorbent material comprises a layered bimetallic hydroxide and nitric acid located between the layers of the layered bimetallic hydroxide; the molar ratio of the nitric acid to the layered bimetallic hydroxide is (0.5~2) mL / g, and the metals in the layered bimetallic hydroxide are magnesium and aluminum; In the modified adsorbent material, the molar ratio of metallic magnesium to metallic aluminum is 1:(0.3~0.7). The median particle size of the modified adsorbent material is 1.0~6.0 μm; The modified adsorbent material has an average pore size of 12-14 nm.

[0044] Optionally, the nitric acid exists in the interlayer of the layered bimetallic hydroxide of the modified adsorbent material in the form of nitrate ions.

[0045] Optionally, the volume-to-mass ratio of the nitric acid to the layered bimetallic hydroxide is 1 mL / g.

[0046] Preferably, the specific surface area of ​​the modified adsorbent material is 14-20 m².2 / g.

[0047] Optionally, the total pore volume of the modified adsorbent material is 0.04~0.05 cm³. 3 / g.

[0048] Optionally, the modified adsorbent material has anion exchange adsorption sites for adsorbing perfluorinated compounds.

[0049] Optionally, the modified adsorbent material is the modified adsorbent material used in the applications described in the first aspect.

[0050] Thirdly, the present invention provides a method for preparing a modified adsorbent material, characterized in that it includes the following steps: in the presence of a solvent, a layered bimetallic hydroxide undergoes an exchange reaction with a modifier to obtain the modified adsorbent material; The modifier is concentrated nitric acid. The solvent is methanol; The metals in the layered bimetallic hydroxide are magnesium and aluminum.

[0051] In one embodiment, the preparation method and dosage of the modified adsorbent material are as described in the first aspect.

[0052] Fourthly, the present invention provides a modified adsorbent material for use as described in the first aspect or as described in the second aspect, wherein the modified adsorbent material is prepared by the preparation method described in the third aspect.

[0053] Fifthly, the present invention provides an application of a modified adsorbent material prepared by the preparation method described in the third aspect in the removal of perfluorinated compounds.

[0054] Optionally, the application is as described in the first aspect.

[0055] In a sixth aspect, the present invention provides a method for removing perfluorinated compounds using a modified adsorbent material as described in the first aspect, a modified adsorbent material as described in the second aspect, or a modified adsorbent material prepared by the preparation method described in the third aspect.

[0056] Optionally, it includes the following steps: Mix the water sample to be treated with the modified adsorbent material, adjust the pH of the water sample to 6-7, control the temperature at 20-25℃, and perform constant temperature oscillation adsorption to adsorb and fix the perfluorinated compounds on the modified adsorbent material. After reaching adsorption equilibrium, separate and remove the adsorbent material.

[0057] Optionally, the perfluorinated compound comprises at least one of perfluorooctanoic acid, perfluorooctyl sulfonic acid, perfluorobutyric acid, and perfluorohexane sulfonic acid.

[0058] Optionally, the pH adjustment requires a pH adjuster; preferably, it includes an acidic adjuster and an alkaline adjuster; more preferably, the acidic adjuster includes at least one of hydrochloric acid, sulfuric acid, and nitric acid; and the alkaline adjuster includes at least one of sodium hydroxide, sodium carbonate, and lime.

[0059] Optionally, the dosage of the modified adsorbent material is 0.1~0.75 g / L, preferably 0.25~0.75 g / L, for example 0.1 g / L, 0.15 g / L, 0.2 g / L, 0.25 g / L, 0.3 g / L, 0.35 g / L, 0.4 g / L, 0.45 g / L, 0.5 g / L, 0.75 g / L or any range between the aforementioned values.

[0060] Optionally, the concentration of perfluorinated compounds in the treated water is 100~1000 μg / L.

[0061] Beneficial effects 1. This invention utilizes a specially modified layered bimetallic hydroxide as a modified adsorbent material. By optimizing its microstructure (specific surface area, pore size, etc.), it provides abundant adsorption sites and can achieve efficient and rapid adsorption and removal of various perfluorinated compounds through anion exchange and other mechanisms, effectively solving the problems of insufficient adsorption capacity and susceptibility to interference ions in existing materials.

[0062] 2. The entire treatment method operates under mild conditions, requiring only isothermal oscillation at near-neutral pH and room temperature, without the need for complex equipment or high energy consumption. Furthermore, the preparation process of the modified adsorbent material is mature, and the raw materials are readily available, keeping both the processing cost and operating energy consumption of this method at a low level.

[0063] 3. The operation process of this method is simple, making it easy to apply and promote on a large scale in actual water treatment projects. Attached Figure Description

[0064] Figure 1 This is a SEM image of the modified adsorbent material.

[0065] Figure 2 This is the XRD pattern of the modified adsorbent material.

[0066] Figure 3 The graphs show the adsorption curves of perfluorooctanoic acid (PFOA) by the modified adsorbent material in Test Example 2, where a is the adsorption curve from 0 to 24 h and b is the adsorption curve from 0 to 120 min. Detailed Implementation

[0067] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0068] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0069] Example 1 This embodiment investigates the removal effect of modified adsorbent materials on perfluorinated compounds in water. The specific preparation steps are as follows: The preparation method of the modified adsorbent material of the present invention specifically includes the following steps: 1) Dissolve 0.1 mol / L magnesium nitrate, 0.05 mol / L aluminum nitrate, and 0.7 mol / L urea in water and stir until homogeneous at room temperature to obtain a mixed solution. Transfer the mixed solution to a hydrothermal reactor and react at 120°C for 10-15 hours. After the reaction is stopped, cool to room temperature, remove the solution, filter, separate the aqueous layer, and centrifuge the lower solid layer repeatedly until neutral to remove large particles and residual Na from the synthesis process. + CO3² - Plasma (with residual impurities) was removed, and the solid was washed twice with ethanol. The resulting solid was then dried in an oven at 60°C to obtain a layered bimetallic hydroxide.

[0070] 2) The layered bimetallic hydroxide obtained in step 1) was added to a three-necked flask, and then 150 mL of methanol was added as the reaction solvent (the solid-liquid ratio of the layered bimetallic hydroxide to methanol was 10 g / L). After stirring evenly, 1.5 mL of concentrated nitric acid (68% by mass) was quickly added, and the mixture was stirred at high speed for 12 hours. During this process, N2 was introduced to maintain a nitrogen atmosphere. After the reaction was completed, the reaction solution was centrifuged to obtain a solid, which was washed once with methanol. The obtained solid was dried in an oven at 60°C to obtain the modified adsorbent material. During the reaction, an N2 atmosphere was maintained for 12 hours.

[0071] The microstructure of the modified layered bimetallic hydroxide prepared in Example 1 was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results are shown in the figure. Figure 1 and Figure 2 .

[0072] in, Figure 1The SEM scale bar is 2 μm, which clearly shows that the modified bimetallic hydroxide obtained by this invention has a layered structure with uniform layers. Its performance parameters are as follows: median particle size is 1.0~6.0 μm. According to calculations, the average pore size of the modified bimetallic hydroxide of this invention is in the range of 12~14 nm, the specific surface area is in the range of 14~20 m² / g, and the total pore volume is in the range of 0.04~0.05 cm³ / g.

[0073] Figure 2 The XRD diffraction pattern shows characteristic diffraction peaks at 9.9°, 19.8°, 34.6°, 38.0°, and 43.6°, corresponding to the characteristic diffraction planes (003), (006), (012), (015), and (018), respectively, which are consistent with NO3. - The intercalated layered bimetallic hydroxide corresponds to this.

[0074] Example 2 Referring to the steps of Example 1, the amount of methanol in step (2) is changed, wherein the solid-liquid ratio of the layered bimetallic hydroxide to methanol is 10 g / L, the volume ratio of methanol to concentrated nitric acid is 110:1, and the rest of the operation is the same as in Example 1.

[0075] Example 3 Referring to the steps of Example 1, the amount of methanol in step (2) is changed, wherein the solid-liquid ratio of the layered bimetallic hydroxide to methanol is 10 g / L, the volume ratio of methanol to concentrated nitric acid is 105:1, and the remaining operations and amounts are the same as in Example 1.

[0076] Comparative Example 1 Referring to the steps of Example 1, the type of solvent in step (2) is changed, wherein an equal amount of deionized water is used as the solvent, and the remaining operations and amounts are the same as in Example 1.

[0077] Comparative Example 2 Referring to the steps of Example 1, the type of solvent in step (2) is changed, wherein an equal amount of ethanol is used as the solvent, and the remaining operations and amounts are the same as in Example 1.

[0078] Comparative Example 3 Referring to the steps of Example 1, the type of modifier in step (2) is changed, wherein an equal amount and concentration of concentrated sulfuric acid is used as the solvent, and the remaining operations and dosages are the same as in Example 1.

[0079] Comparative Example 4 Referring to the steps of Example 1, the type of metal salt in step (1) was changed, wherein magnesium chloride and aluminum chloride of equal concentration were used as metal salts, and the amount of modifier added in step (2) was changed, wherein 200 μL of concentrated nitric acid was used, and the remaining operations and amounts were the same as in Example 1.

[0080] Comparative Example 5 Referring to the steps of Example 1, the type of alkali source in step (1) was changed, wherein sodium hydroxide of equal concentration was used as the alkali source, and layered bimetallic hydroxides were synthesized at room temperature. The remaining operations and amounts were the same as in Example 1.

[0081] Test Example 1 Standards for perfluorooctanoic acid (PFOA), perfluorooctyl sulfonic acid (PFOS), perfluorobutyric acid (PFBA), and perfluorohexane sulfonic acid (PFHxS) were added to ultrapure water to achieve a concentration of 100 μg / L for each perfluorinated compound. The pH was adjusted to 7 using a pH adjuster. The modified layered bimetallic hydroxide prepared in Example 1 was added to the water at a concentration of 0.25 g / L. Adsorption was then carried out in a constant-temperature water bath shaker at 150 r / min for 24 h at 20 °C. After the reaction, 5 mL of the supernatant was collected and filtered through a 0.22 μm filter. The first 3.5 mL was discarded, and the last 1.5 mL was analyzed using high-performance liquid chromatography-mass spectrometry (HPLC-MS). The results are shown in Table 1.

[0082] Table 1. Removal rates of different perfluorinated compounds by adsorbent materials Perfluorinated compounds 1-hour removal rate (%) 24-hour removal rate (%) PFOA 76.58 81.80 PFOS 94.84 97.70 PFHxS 60.65 77.08 PFBA 20.67 25.82 Experimental results show that the adsorbent material used in this invention has good adsorption capacity for a variety of perfluorinated compounds. Adding 0.25 g / L of adsorbent can effectively adsorb and remove perfluorinated compounds within a 1-hour contact time. In particular, the removal rates of perfluorooctanoic acid and perfluorooctyl sulfonic acid, which are included in the appendix of the drinking water hygiene standards, reached 76.58% and 94.84%, respectively, and the removal rates after 24 hours reached 81.80% and 97.70%, respectively.

[0083] Test Example 2 (1) PFOA standard was added to ultrapure water to make the PFOA concentration in the solution 100~1000µg / L, and the pH was adjusted to 7 by pH adjuster. The modified layered bimetallic hydroxide prepared in Example 1 was added at a dosage of 0.25g / L, and then adsorption was carried out in a constant temperature water bath shaker at a speed of 150r / min, an adsorption temperature of 20℃, and an adsorption time of 24h. After the reaction was completed, 5mL of the supernatant after adsorption was taken and filtered through a 0.22μm filter. The first 3.5mL of liquid was discarded, and the last 1.5mL of liquid was taken for analysis by high performance liquid chromatography-mass spectrometry. The PFOA adsorption results are shown in Table 2 below.

[0084] Table 2. Removal rate of adsorbent for different concentrations of PFOA in water

[0085] Experimental results show that the adsorbent material has a good treatment effect on PFOA within a certain range.

[0086] (2) Adsorption curves of 1000 µg / L PFOA were plotted from 0 to 120 min and from 0 to 24 h as shown in the figure. Figure 3 As shown (where a is the adsorption curve from 0 to 24 h, and b is the adsorption curve from 0 to 120 min). Experimental results show that the adsorbent material used in this invention has good adsorption capacity for PFOA. With an adsorbent concentration of 0.25 g / L, the removal rate can reach 88.7% after 10 min of contact and 97.2% after 30 min. max The removal rate can reach 98.2%, demonstrating the ability of this adsorbent material to remove PFOA quickly and efficiently.

[0087] (3) The modified layered bimetallic hydroxides prepared in Examples 2-4 were subjected to the same experimental method as in step 2: PFOA standard was added to ultrapure water to make the PFOA concentration in the solution 1000 µg / L, and the pH was adjusted to 7 using a pH adjuster. 0.25 g / L of the modified layered bimetallic hydroxide was added, and then adsorption was carried out in a constant temperature water bath shaker at a speed of 150 r / min for 24 h at an adsorption temperature of 20 °C. After the reaction, 5 mL of the supernatant was taken and filtered through a 0.22 μm filter. The first 3.5 mL of liquid was discarded, and the last 1.5 mL of liquid was analyzed using high performance liquid chromatography-mass spectrometry. The results showed that the removal rate of PFOA by the modified layered metal hydroxide in Example 2 after 24 h of reaction was 98.2%; the removal rate of PFOA by the modified layered metal hydroxide in Example 3 after 24 h of reaction was 85.9%.

[0088] Test Example 3 This embodiment provides a method for removing perfluorinated compounds from water using the modified layered bimetallic hydroxide prepared in Example 1. The method is basically the same as that in Test Example 2, and the specific parameters are as follows: The modified layered bimetallic hydroxide was added at a dosage of 0.1–0.75 g / L, the PFOA concentration was 1000 µg / L, the pH was 7.0, and the reaction time was 24 h. The results are shown in Table 3 below.

[0089] Table 3. Removal rate of PFOA in water by different dosages of adsorbent

[0090] As shown in the table above, when the dosage of adsorbent material increased from 0.1 to 0.75 g / L, the PFOA removal rate increased from 41.93% to 98.11%, indicating that the micro-modified layered bimetallic hydroxide maintained a high PFOA removal rate.

[0091] Test Example 4 This embodiment provides a method for removing perfluorinated compounds from water using the modified layered bimetallic hydroxide prepared in Example 1. The method is basically the same as that in Test Example 2, and the specific parameters are as follows: The modified layered bimetallic hydroxide was added at a dosage of 0.25 g / L, the PFOA concentration was 1000 µg / L, the pH was 3–11, and the reaction time was 24 h. The results are shown in Table 4 below.

[0092] Table 4. Removal rate of PFOA from water by adsorbent materials at different pH levels

[0093] The results showed that as the pH of the water sample increased from 3 to 7, the PFOA removal rate increased from 89.18% to 95.64%. However, as the pH continued to increase to 11, the PFOA removal rate decreased from 95.64% to 61.06%. Under neutral conditions, the adsorbent material maintained a high PFOA removal rate. This is because at neutral pH, the zeta potential of the adsorbent material is positive, and the carboxylic acid groups (-COOH) of PFOA completely dissociate into negatively charged -COO groups. - PFOA exists in anionic form, which allows the negatively charged PFOA to bind more tightly to the positively charged surface or interlayer region of the adsorbent material. However, at acidic pH, PFOA is protonated (-COOH), weakening the electrostatic interaction; at alkaline pH, the deprotonation of hydroxyl groups on the LDH surface leads to a more negative Zeta potential, reducing the adsorbent material's ability to capture PFOA through electrostatic adsorption, thus resulting in a lower removal rate.

[0094] Test Example 5 Actual water bodies contain a certain amount of salt, and the anions in these waters (such as Cl-) are... - NO3 - SO4 2- CO3 2- These compounds compete with PFOA for adsorption sites on the adsorbent, leading to a decrease in the adsorbent's efficiency against PFOA. Generally, monovalent anions interfere less with PFOA than polyvalent anions. All good adsorbent materials should have a certain degree of resistance to anion interference. The resistance to anion interference is reflected by simulating the coexistence of different anions with PFOA. This embodiment provides a method for removing perfluorinated compounds from water using the modified layered bimetallic hydroxide prepared in Example 1. The method is basically the same as in Test Example 2, with the specific parameters as follows: The modified layered bimetallic hydroxide was added at a dosage of 0.25 g / L, the PFOA concentration was 1000 µg / L, the pH was 7, and the reaction time was 24 h. Then, 1 mM of different anions (Cl...) were added to the water to be treated. - NO3 - CO32- SO4 2- The results are shown in Table 5 below.

[0095] Table 5. Removal rate of PFOA from water by adsorbent materials under different anion (1 mM) interference.

[0096] Results analysis: Monovalent anion (Cl... - NO3 - Even when coexisting with divalent anions (CO3), the removal rate of PFOA can still be maintained at 86.78% and 86.50%, respectively. 2- SO4 2- The removal rate of PFOA was controlled at over 50% even when coexisting, indicating that the modified layered bimetallic hydroxide has good resistance to anion interference.

[0097] Test Example 6 The presence of organic matter in water can also affect the adsorption efficiency of PFOA. For example, humic acid (HA) can interfere with adsorption through site competition and steric hindrance, leading to a decrease in the adsorbent's efficiency for PFOA. This study simulates the coexistence of organic matter and PFOA to reflect the interference capabilities of other factors. This embodiment provides a method for removing perfluorinated compounds from water using the modified layered bimetallic hydroxide prepared in Example 1. The method is basically the same as in Test Example 2, with specific parameters as follows: The modified layered bimetallic hydroxide was added at a dosage of 0.25 g / L, the PFOA concentration was 1000 µg / L, the pH was 7, and the reaction time was 24 h. Then, 1 mg / L of humic acid was added to the water to be treated. The results are shown in Table 6 below.

[0098] Table 6. Removal rate of PFOA from water by adsorbent materials under other influencing factors other PFOA removal rate (%) Humic acid (1 mg / L) 94.13 The results showed that the removal rate of PFOA could be maintained at 94.13% when humic acid was present, indicating that the modified layered bimetallic hydroxide had good resistance to organic matter interference.

[0099] Test Example 7 To enable the material to be recycled multiple times, desorption experiments were conducted on the modified layered bimetallic hydroxide. PFOA in the water was collected through adsorption-desorption experiments and then subjected to subsequent chemical treatment. For the material in Example 2 that adsorbed 1000 µg / L PFOA, a certain volume of different desorption solutions was added to the adsorbed material, the pH was adjusted with a pH adjuster, and the mixture was placed in a constant-temperature shaker at 150 rpm for a certain period of time. The supernatant was then collected for analysis to determine the desorption rate of the material.

[0100] The specific steps are as follows: The PFOA-adsorbed material from Test Example 2, with a concentration of 1000 µg / L, was placed in a PFOA solution with a solid-liquid ratio of 0.25 g / L. The solution was shaken at 150 rpm for 24 h in a constant-temperature shaker. The supernatant was then analyzed using high-performance liquid chromatography-mass spectrometry (HPLC-MS / MS). The saturated adsorbent material was removed, dried, and placed in different desorption solutions with a solid-liquid ratio of 0.25 g / L. The solution was then shaken at 150 rpm for 24 h in a constant-temperature shaker. The supernatant was then analyzed using HPLC-MS / MS. The results are shown in Table 7 below.

[0101] Table 7 Desorption rates of adsorbent materials by different desorption solutions Desorption liquid Desorption rate (%) A mixture of methanol and 0.5M NaCl solution in a volume ratio of 1:1 35.61 A mixture of methanol and 0.5M NaCl solution in a volume ratio of 7:3. 26.59 A mixture of methanol and 1 wt% NaCl solution in a volume ratio of 1:1 11.46 A mixture of methanol and 1 wt% NaCl solution in a volume ratio of 3:2 19.27 A mixture of methanol and 1 wt% NaCl solution in a volume ratio of 7:3. 92.44 Using a mixture of methanol and 1 wt% NaCl solution (7:3 volume ratio) as the desorption solvent, the desorption rate of PFOA reached 92.44%, indicating that this mixture is the optimal desorption solvent for recycling the adsorbent. This is because the appropriate amount of methanol mixed with water reduces the polarity of the system, weakening the PFOA carboxyl groups (-COO). - PFOA is attracted to the adsorbent material's layers or surface by electrostatic attraction, and methanol can also disrupt the hemimictal aggregation of PFOA in water, releasing its monomeric form. NaCl solution can provide Cl... - By replacing the interlayer PFOA through ion exchange, a suitable ratio of methanol and NaCl solution can achieve efficient desorption.

[0102] The regenerated adsorbent was then added back to the PFOA solution, and a second round of adsorption was performed using this desorption buffer. This process was repeated multiple times during the adsorption-regeneration experiment, and the adsorption rate remained excellent.

[0103] Comparative test cases The experimental procedures and methods for this comparative example and test example 2 are basically the same. The difference is that the adsorbent added is the unmodified layered bimetallic hydroxide and the modified layered bimetallic hydroxide prepared in comparative examples 1-5. The specific parameters are as follows: (1) An unmodified layered bimetallic hydroxide (i.e., the layered bimetallic hydroxide prepared in step 1 of Example 1) was used, with an addition amount of 0.25 g / L, a PFOA concentration of 1000 µg / L, a pH of 7, and a reaction time of 24 h. The results showed that the removal rate of PFOA after 24 h of reaction was 62.5%. This indicates that the modified adsorbent material has a significant improvement in the removal efficiency of perfluorinated substances.

[0104] (2) The modified layered bimetallic hydroxide prepared in Comparative Example 1 was added at a dosage of 0.25 g / L, the concentration of PFOA was 1000 µg / L, the pH was 7, and the reaction time was 24 h. The results showed that the removal rate of PFOA after 24 h of reaction was 69.4%. This indicates that when water is used as a solvent during modification, even when air is isolated, the resulting adsorbent material does not significantly improve the removal efficiency of perfluorinated substances.

[0105] (3) The modified layered bimetallic hydroxide prepared in Comparative Example 2 was added at a dosage of 0.25 g / L, the concentration of PFOA was 1000 µg / L, the pH was 7, and the reaction time was 24 h. The results showed that the removal rate of PFOA after 24 h of reaction was 73.2%. This indicates that when ethanol is used as a solvent during modification, the modified adsorbent material has a better removal effect on perfluorinated substances than when methanol is used as a solvent.

[0106] (4) The modified layered bimetallic hydroxide prepared in Comparative Example 3 was added at a dosage of 0.25 g / L, the concentration of PFOA was 1000 µg / L, the pH was 7, and the reaction time was 24 h. The results showed that the removal rate of PFOA after 24 h of reaction was 65.8%. This indicates that when concentrated sulfuric acid was used as a modifier during modification, the resulting adsorbent did not significantly improve the removal of perfluorinated substances.

[0107] (5) The modified layered bimetallic hydroxide prepared in Comparative Example 4 was added at a dosage of 0.25 g / L, the concentration of PFOA was 1000 µg / L, the pH was 7, and the reaction was carried out for 24 h. The results showed that the removal rate of PFOA after 24 h of reaction was 76.92%, which indicates that reasonable control of the synthesis and modification conditions can achieve better removal effect for perfluorinated compounds.

[0108] (6) The modified layered bimetallic hydroxide prepared in Comparative Example 5 was added at a dosage of 0.25 g / L, the concentration of PFOA was 1000 µg / L, the pH was 7, and the reaction time was 24 h. The results showed that the removal rate of PFOA after 24 h of reaction was 85.96%, but the cost of urea was lower.

[0109] Application examples The experimental procedures in this application example are basically the same as those in test example 2. The difference is that the water sample used is a real water sample containing perfluorinated compounds. The basic information of the water sample is shown in Table 8 below: Table 8 Basic Information of Actual Water Samples to be Treated

[0110] The specific reaction parameters are as follows: The modified layered bimetallic hydroxide prepared in Example 1 was added at a dosage of 0.25 g / L, the pH was 7, and the reaction time was 24 h. The results are shown in Table 9 below.

[0111] Table 9. Removal rate of perfluorinated compounds from actual water samples by the adsorbent

[0112] The adsorbent material exhibits good anti-interference ability in real water samples and also shows good removal effects on PFOA and PFBA, indicating that the adsorbent and controlled reaction parameters used in this invention can effectively remove perfluorinated compounds from the water samples.

[0113] In this invention, unless otherwise stated, scientific and technical terms used herein have the meanings commonly understood by those skilled in the art. Furthermore, the reagents, materials, and procedures used herein are all widely used in the relevant fields.

[0114] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. The application of a modified adsorbent material in the removal of perfluorinated compounds, characterized in that, The modified adsorbent material comprises a layered bimetallic hydroxide and nitric acid located between the layers of the layered bimetallic hydroxide; the volume-to-mass ratio of the nitric acid to the layered bimetallic hydroxide is (0.5~2) mL / g, and the metals in the layered bimetallic hydroxide are magnesium and aluminum; In the modified adsorbent material, the molar ratio of metallic magnesium to metallic aluminum is 1:(0.3~0.7). The median particle size of the modified adsorbent material is 1.0~6.0 μm; The modified adsorbent material has an average pore size of 12-14 nm.

2. The application according to claim 1, characterized in that, In the modified adsorbent material, the molar ratio of metallic magnesium to metallic aluminum is 1:0.5; The modified adsorbent material has a specific surface area of ​​14-20 m². 2 / g; And / or, the total pore volume of the modified adsorbent material is 0.04~0.05 cm³. 3 / g; And / or, the modified adsorbent material has anion exchange adsorption sites for adsorbing perfluorinated compounds.

3. The application according to claim 1 or 2, characterized in that, The modified adsorbent material is prepared by the following method: in the presence of a solvent, a layered bimetallic hydroxide undergoes an exchange reaction with a modifier to obtain the modified adsorbent material. The modifier is concentrated nitric acid. The solvent is methanol.

4. The application according to claim 3, characterized in that, The mass-to-volume ratio of the layered bimetallic hydroxide to the methanol is 1~15 g / L; preferably 5~10 g / L. Optionally, the mass-to-volume ratio of methanol to the modifier is (90~120):1; preferably (100~115):1; more preferably (100~110):1; Optionally, the concentrated nitric acid has a mass percentage content of 60-75%, preferably 68%; Optionally, the exchange reaction takes 10 to 30 hours, preferably 12 to 24 hours; Optionally, the exchange reaction further includes the following post-processing steps: centrifuging the reaction solution to obtain a solid, washing, and drying; Preferably, the cleaning can be a single cleaning with methanol; Preferably, the drying is performed in an oven, more preferably in an oven at 60°C; Optionally, the exchange reaction further includes the preparation of the layered bimetallic hydroxide, which includes the following steps: mixing magnesium salt, aluminum salt and urea in a solvent to obtain a mixture, and carrying out a hydrothermal reaction of the mixture in a hydrothermal reactor to prepare the layered bimetallic hydroxide.

5. The application according to claim 4, characterized in that, The magnesium salt is magnesium nitrate, and the aluminum salt is aluminum nitrate; Optionally, the molar ratio of the magnesium salt to the aluminum salt is 1:(0.3~0.7), preferably 1:0.5; Optionally, the total molar amount of the bimetallic salt and the molar ratio of the urea are 1:(4~5), preferably 1:4.5 or 3:14; Optionally, the mixing is based on the uniform mixing of all substances in the system; Optionally, the temperature of the hydrothermal reaction is 100~150℃, preferably 120℃; Optionally, the hydrothermal reaction time is 10-15 hours; Optionally, the hydrothermal reaction further includes the following post-processing steps: cooling, separation, washing, and drying; Preferably, the cleaning process involves first cleaning with water and then cleaning with ethanol.

6. The application according to claim 1, characterized in that, The perfluorinated compound includes at least one of perfluorooctanoic acid, perfluorooctyl sulfonic acid, perfluorobutyric acid, and perfluorohexane sulfonic acid; Optionally, the application involves immersing the modified adsorbent material in the water to be treated for adsorption, thereby achieving effective removal of perfluoride.

7. The application according to claim 1, characterized in that, The application involves adding a pH adjuster to a water sample containing perfluorinated compounds to adjust the pH value of the water sample to 6.0~7.

0. Preferably, the pH adjuster includes an acidic adjuster and an alkaline adjuster; more preferably, the acidic adjuster includes at least one of hydrochloric acid, sulfuric acid, and nitric acid; and the alkaline adjuster includes at least one of sodium hydroxide, sodium carbonate, and lime. Optionally, the dosage of the modified adsorbent material is 0.1~0.75 g / L; preferably 0.25~0.75 g / L. Optionally, the concentration of perfluorinated compounds in the treated water is 100~1000 μg / L; Optionally, the adsorption temperature is 20~25℃; Optionally, the adsorption process requires stirring; preferably, the stirring intensity is 150~200 r / min. Optionally, the adsorbed material is separated from the treated water by filtration or centrifugation.

8. A modified adsorbent material, characterized in that, The modified adsorbent material comprises a layered bimetallic hydroxide and nitric acid located between the layers of the layered bimetallic hydroxide; the volume-to-mass ratio of the nitric acid to the layered bimetallic hydroxide is (0.5~2) mL / g, and the metals in the layered bimetallic hydroxide are magnesium and aluminum; In the modified adsorbent material, the molar ratio of metallic magnesium to metallic aluminum is 1:(0.3~0.7). The median particle size of the modified adsorbent material is 1.0~6.0 μm; The modified adsorbent material has an average pore size of 12-14 nm; Preferably, The modified adsorbent material has a specific surface area of ​​14-20 m². 2 / g; And / or, the total pore volume of the modified adsorbent material is 0.04~0.05 cm³. 3 / g; And / or, the modified adsorbent material has anion exchange adsorption sites for adsorbing perfluorinated compounds; More preferably, The modified adsorbent material is the modified adsorbent material used in any one of claims 1-5.

9. A method for preparing a modified adsorbent material, characterized in that, It includes the following steps: in the presence of a solvent, a layered bimetallic hydroxide undergoes an exchange reaction with a modifier to obtain the modified adsorbent material; The modifier is concentrated nitric acid. The solvent is methanol; The metals in the layered bimetallic hydroxide are magnesium and aluminum; Preferably, the preparation method and dosage of the modified adsorbent material are as described in claim 4 or 5.

10. A method for removing perfluorinated compounds using the modified adsorbent material in any one of claims 1-5, the modified adsorbent material as described in claim 8, or the modified adsorbent material prepared by the preparation method as described in claim 9; Optionally, it includes the following steps: Mix the water sample to be treated with the modified adsorbent material, adjust the pH of the water sample to 6-7, control the temperature at 20-25℃, and perform constant temperature oscillation adsorption to adsorb and fix the perfluorinated compounds on the modified adsorbent material. After reaching adsorption equilibrium, separate and remove the adsorbent material. Optionally, the perfluorinated compound comprises at least one of perfluorooctanoic acid, perfluorooctyl sulfonic acid, perfluorobutyric acid, and perfluorohexane sulfonic acid; Optionally, the pH adjustment requires a pH adjuster; preferably, it includes an acidic adjuster and an alkaline adjuster; more preferably, the acidic adjuster includes at least one of hydrochloric acid, sulfuric acid, and nitric acid; and the alkaline adjuster includes at least one of sodium hydroxide, sodium carbonate, and lime. Optionally, the dosage of the modified adsorbent material is 0.1~0.75 g / L; preferably 0.25~0.75 g / L. Optionally, the concentration of perfluorinated compounds in the treated water is 100~1000 μg / L.

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