Boron-based adsorbent, method for producing the same, and method for adsorbing boron

Abstract

The application discloses a boron adsorbent and a preparation method and a boron adsorption method thereof. The preparation method of the boron adsorbent comprises the following steps: preparing a hydrotalcite precursor solution, wherein the hydrotalcite precursor solution at least contains aluminum ions and magnesium ions; mixing the hydrotalcite precursor solution with tartaric acid to obtain a reaction precursor solution; adjusting the pH value of the reaction precursor solution to be alkaline, so that the aluminum ions, the magnesium ions and the tartaric acid in the reaction precursor solution generate a coprecipitation reaction to form a hydrotalcite precursor, and the tartaric acid is intercalated between the layers of the hydrotalcite precursor to obtain a reaction mixture; and then aging treatment is performed to obtain the boron adsorbent. The preparation method has the advantages of mild conditions, simple process and environmental friendliness. The prepared boron adsorbent has a wide application range, has a good adsorption effect in the pH value range of 5-10, has a large adsorption capacity, is less interfered by other coexisting ions, and has a strong recycling performance.

Description

Technical Field

[0001] This invention belongs to the field of functional composite materials technology, particularly the field of boron adsorption composite materials, and especially relates to a boron-based adsorbent and its preparation method, as well as a boron adsorption method. Background Technology

[0002] Boron is widely used in modern industry, typically in the form of boric acid, borax, and boron carbide. For example, due to its high neutron rejection rate, boron is used in the military and nuclear industries; furthermore, the addition of boron can significantly improve the performance of flame-retardant materials. On the other hand, while boron is an essential trace element for plants and animals, excessive boron in surface water can adversely affect plant cell division, photosynthesis, and respiration; excessive boron inhalation by animals can inhibit digestive enzyme activity, leading to loss of appetite and indigestion; in addition, boron volatilized into the atmosphere with water vapor exacerbates the greenhouse effect and air pollution; and trace amounts of boron can severely affect the purity of lithium extracted from salt lakes. Based on these two points, the separation and extraction of boron from solution is of great significance.

[0003] Currently, the main methods for separating boron include acid crystallization, adsorption, extraction, and membrane separation. Acid crystallization utilizes the low solubility of boric acid in aqueous solution. Boron in the brine is first converted to boric acid using hydrochloric acid or sulfuric acid, and then crystallized out once the boric acid reaches saturation. This is the earliest researched and most mature process, but it requires a large amount of acid. With the addition of reverse osmosis and electrodialysis, membrane separation can achieve the separation of boron from solution. However, the complex composition of salt lake brine makes membrane fouling prone to occur, shortening membrane life. Extraction utilizes the difference in solubility of the substances to be separated in two phases to achieve separation. It has the advantages of simple process and low cost, but it is not suitable for trace operations and has a low processing limit. Adsorption solves this problem precisely. Adsorption can further extract boron from the extracted solution to meet emission standards. Adsorption is currently the simplest and most widely used method for separating and extracting boron from solution.

[0004] Hydrotalcite, as an inorganic adsorbent material, possesses interlayer anion exchangeability and calcination reducing properties, both of which can be used for the separation and extraction of boron from solution. However, its adsorption capacity is low and its selectivity is poor. In recent years, the interlayer anion exchangeability of hydrotalcite has been utilized to allow organic anions to enter the interlayer of hydrotalcite, giving it multifunctionality. Selecting anions with multiple hydroxyl groups to enter the hydrotalcite interlayer can achieve specific adsorption of boron, reducing interference from other coexisting ions. Tartaric acid is an organic acid with two hydroxyl groups extracted from plants. To date, no systematic study has been conducted on the adsorption of boron by tartaric acid intercalation into hydrotalcite.

[0005] For example, Chinese invention patent CN102336856 A discloses a method for preparing a boron-specific resin, using styrene-divinylbenzene as a backbone and introducing secondary amine groups through chloromethylation and acetone. However, this method has a complex preparation process, and the prepared boron-specific resin is only suitable for acidic environments. Chinese invention patent CN1666813 A discloses a method for preparing an organic-inorganic composite boron adsorption functional material. This invention combines an organosilane coupling agent with a compound containing polyhydroxy functional groups in an organic solution to prepare a composite material. However, the organic raw materials used in this method all cause environmental pollution. Chinese invention patent CN106149369 A discloses a method for preparing a boron-based adsorbent for functional fibers, but does not provide data such as adsorption process parameters and adsorption capacity. This invention places polyacrylonitrile fibers in an organic ammonia aqueous solution and heats them under reflux, then places them in a D-glucose aqueous solution and heats them under reflux, followed by drying to obtain the functional material. However, the preparation process of this invention is too cumbersome and unsuitable for large-scale production. Chinese invention patent CN104874365 A discloses a carboxymethyl cellulose ion-intercalated hydrotalcite composite material and its preparation method, but its interlayer spacing is small, which is not conducive to boron adsorption. In addition, the regeneration and recycling performance of its adsorbent material is poor. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention employs environmentally friendly tartaric acid as an organic intercalating agent and uses a one-step precipitation method to prepare organically intercalated hydrotalcite for adsorbing boron from solution, and conducts cyclic adsorption experiments. Based on the above technical concept, the purpose of this invention is to provide a boron-based adsorbent, its preparation method, and a method for boron adsorption.

[0007] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0008] In a first aspect, the present invention provides a method for preparing a boron-based adsorbent, comprising:

[0009] 1) Prepare a hydrotalcite precursor solution, wherein the hydrotalcite precursor solution contains at least aluminum ions and magnesium ions;

[0010] 2) Mix the hydrotalcite precursor solution with tartaric acid to obtain the reaction precursor solution;

[0011] 3) Adjust the pH of the reaction precursor solution to be alkaline so that the aluminum ions, magnesium ions and tartaric acid in the reaction precursor solution undergo a co-precipitation reaction to generate a hydrotalcite precursor. The tartaric acid is intercalated between the layers of the hydrotalcite precursor to obtain a reaction mixture.

[0012] 4) The reaction mixture is aged to obtain a boron-based adsorbent.

[0013] Secondly, the present invention also provides a boron-based adsorbent prepared by the above preparation method, wherein the boron-based adsorbent comprises a hydrotalcite body and intercalated tartaric acid, wherein the hydrotalcite body comprises a plurality of stacked hydrotalcite sublayers, and the intercalated tartaric acid is intercalated between the hydrotalcite sublayers.

[0014] Thirdly, the present invention also provides a method for adsorbing boron, comprising:

[0015] Provide the above-mentioned boron-based adsorbents;

[0016] The boron-based adsorbent is added to the boron solution to be treated to carry out the adsorption reaction.

[0017] Based on the above technical solution, compared with the prior art, the beneficial effects of the present invention include at least the following:

[0018] The boron-based adsorbent preparation method provided by this invention has mild preparation conditions and a simple preparation process. The tartaric acid used is extracted from plant species, which has the advantage of being environmentally friendly. The boron-based adsorbent prepared by this invention has a wide range of applications, has good adsorption effect in the pH range of 5-10, has a large adsorption capacity, is less affected by other coexisting ions, and has strong recycling performance.

[0019] The above description is merely an overview of the technical solution of the present invention. In order to enable those skilled in the art to better understand the technical means of this application and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described below in conjunction with detailed drawings. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the reaction process and equipment structure of a boron-based adsorbent preparation method provided in a typical embodiment of the present invention;

[0021] Figure 2 This is an XRD pattern of a boron-based adsorbent provided in a typical embodiment of the present invention;

[0022] Figure 3 This is an FTIR test image of a boron-based adsorbent provided in a typical embodiment of the present invention;

[0023] Figure 4 This is a graph showing the correlation between the adsorption capacity of a boron-based adsorbent and different magnesium-aluminum ratios, provided in some typical embodiments of the present invention.

[0024] Figure 5 This is a graph showing the correlation between the adsorption capacity of a boron-based adsorbent and different amounts of tartaric acid added, provided in some typical embodiments of the present invention.

[0025] Figure 6This is a graph showing the correlation between the adsorption capacity of a boron-based adsorbent and different aging temperatures, provided by some typical embodiments of the present invention.

[0026] Figure 7 This is a graph showing the correlation between the adsorption capacity of a boron-based adsorbent and the pH value of different boron solutions to be treated, provided by some typical embodiments of the present invention.

[0027] Figure 8 This is a graph showing the relationship between the adsorption capacity of a boron-based adsorbent and the effect of chloride ion concentration on boron-based adsorbents in the prior art, provided by some typical embodiments of the present invention.

[0028] Figure 9 This is a graph showing the relationship between the adsorption capacity of a boron-based adsorbent and the effect of sulfate ion concentration on boron-based adsorbents in the prior art, provided by some typical embodiments of the present invention.

[0029] Figure 10 This is an FTIR test image of hydrotalcite material before and after NO3-LDH adsorption provided in a typical comparative case of the present invention;

[0030] Figure 11 This is an FTIR test image of a boron-based adsorbent before and after adsorption, provided in a typical embodiment of the present invention;

[0031] Figure 12 This is a test chart of the recycling performance of a boron-based adsorbent provided in a typical embodiment of the present invention. Detailed Implementation

[0032] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0033] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0034] See Figure 1 This invention provides a method for preparing a boron-based adsorbent, comprising the following steps:

[0035] 1) Prepare a hydrotalcite precursor solution, wherein the hydrotalcite precursor solution contains at least aluminum ions and magnesium ions;

[0036] 2) Mix the hydrotalcite precursor solution with tartaric acid to obtain the reaction precursor solution;

[0037] 3) Adjust the pH of the reaction precursor solution to be alkaline so that the aluminum ions, magnesium ions and tartaric acid in the reaction precursor solution undergo a co-precipitation reaction to generate a hydrotalcite precursor. The tartaric acid is intercalated between the layers of the hydrotalcite precursor to obtain a reaction mixture.

[0038] 4) The reaction mixture is aged to obtain a boron-based adsorbent.

[0039] This invention uses aluminum nitrate and magnesium nitrate as cation sources to prepare a magnesium aluminum layered double hydroxide (LDH) framework. Regarding the organic anion, tartaric acid, possessing two carboxyl groups, is more readily bonded to the cation plates of the LDH, and its ortho-hydroxyl groups are beneficial for B(OH) in solution. 3 and B(OH) 4- Therefore, this invention preferably uses tartaric acid as the anion source to prepare tartaric acid root-intercalated hydrotalcite (TA-LDH). The chemical formula of tartaric acid is shown below:

[0040]

[0041] Taking into account the complexity of the synthesis process and energy consumption, this invention ultimately selected co-precipitation as the preparation method for LDHs in this study. Furthermore, in the above technical solution, the one-step co-precipitation method allows the formation of hydrotalcite sheets and the intercalation of tartaric acid to occur simultaneously. This avoids the uneven or incomplete intercalation caused by diffusion resistance resulting from the prior formation of hydrotalcite or hydrotalcite-like structures followed by intercalation, as seen in existing technologies. This results in a more thorough and uniform intercalation of the obtained boron-based adsorbent, improving adsorption capacity and regeneration cycle capability.

[0042] The boron-based adsorbent preparation method provided by this invention has mild preparation conditions and a simple preparation process. The tartaric acid used is extracted from plant species, which has the advantage of being environmentally friendly. The boron-based adsorbent prepared by this invention has a wide range of applications. Tartaric acid has a good adsorption effect in the pH range of 5-10, with a large adsorption capacity. It is less affected by other coexisting ions and has strong recycling performance.

[0043] In some implementations, in step 1), the hydrotalcite precursor solution may include an aqueous solution of aluminum and magnesium salts.

[0044] In some embodiments, the molar ratio of aluminum ions to magnesium ions in the hydrotalcite precursor solution is preferably 1:2 to 1:2.5.

[0045] In some embodiments, the concentration of aluminum ions in the hydrotalcite precursor solution is preferably 0.10-0.11 mol / L.

[0046] In some embodiments, the aluminum salt may include any one or a combination of two of aluminum nitrate and aluminum chloride, but is not limited thereto; the magnesium salt may include any one or a combination of two of magnesium nitrate and magnesium chloride, but is not limited thereto.

[0047] In some implementations, step 2) may specifically include the following steps:

[0048] Prepare a tartaric acid solution, and then add the tartaric acid solution to the hydrotalcite precursor solution to obtain the reaction precursor solution.

[0049] In some embodiments, the molar ratio of aluminum ions to tartaric acid in the reaction precursor solution is preferably 1:2 to 1:2.5.

[0050] In some embodiments, the concentration of tartaric acid in the tartaric acid solution is preferably 0.20-0.25 mol / L.

[0051] In some implementations, step 3) may specifically include the following steps:

[0052] Maintain the temperature of the reaction precursor solution at 60-70°C, and add an aqueous solution of an alkaline substance dropwise to the reaction precursor solution at a specific dropping rate while stirring, so that the pH value of the reaction precursor solution is adjusted to 9-10, and continue stirring to allow the coprecipitation reaction to occur.

[0053] In some embodiments, the alkaline substance may include any one or a combination of two of sodium hydroxide and potassium hydroxide, but is not limited thereto.

[0054] In some embodiments, the concentration of the aqueous solution of the alkaline substance is preferably 1-1.5 mol / L.

[0055] In some embodiments, the specific drop rate preferably corresponds to an aqueous solution of an alkaline substance at a rate of 10-12 mL / min per 1 L of the reaction precursor solution.

[0056] In some embodiments, the reaction time of the coprecipitation reaction is preferably 2-2.5 h.

[0057] In some embodiments, the coprecipitation reaction is preferably carried out under a protective atmosphere to remove carbon dioxide and oxygen.

[0058] In some embodiments, the protective atmosphere may include any one or a combination of two of nitrogen and argon, but is not limited thereto.

[0059] In some implementations, step 4) may specifically include the following steps:

[0060] The reaction mixture is aged at 40-60°C for 18-24 hours.

[0061] In some embodiments, the reaction mixture is transferred to a stainless steel hydrothermal reactor for the aging treatment.

[0062] In some embodiments, the solvents used in the preparation method are boiled for at least 1 hour before use. In particular, the deionized water used in this method needs to be boiled, regardless of the method used, because of CO3... 2- LDHs have a strong intercalation ability and can easily replace other anions. Furthermore, the presence of O2 can affect some easily oxidized anions. Therefore, it is necessary to completely isolate CO2 and O2 during the synthesis process. This invention preferably removes CO2 and O2 from the solution by boiling deionized water for 1 hour or more, for example, 1-2 hours. During the preparation process, CO2 and O2 from the air are isolated using nitrogen protection.

[0063] As a typical application example, the preparation method provided by this invention can be implemented through the following preparation scheme:

[0064] 1) Dissolve 0.02 mol aluminum nitrate nonahydrate (Al(NO3)3·9H2O) and 0.04 mol magnesium nitrate hexahydrate (Mg(NO3)2·6H2O) in 100 mL of deionized water, then transfer the solution to a 500 mL three-necked flask. The solution contains Al... 3+ and Mg 2+ The molar ratio is 1:2-1:2.5.

[0065] 2) Dissolve 0.01 mol TA (tartaric acid) in a 300 mL mixture of water and ethanol (volume ratio 1:1), and transfer the solution to the three-necked flask mentioned above. Al 3+ The ratio of TA to TA is 1:2 to 1:2.5.

[0066] 3) Under nitrogen protection, a peristaltic pump is used at a flow rate of 6 mL / min. -1 Add 1.5 mol·L⁻¹ dropwise. -1 The sodium hydroxide solution was used to adjust the pH of the solution to 9, and the entire process was carried out under stirring in a 60°C water bath.

[0067] 4) After stirring for 2 hours, transfer to a stainless steel hydrothermal reactor for aging for 24 hours, and then allow it to cool naturally to room temperature. The aging temperature is 20℃-60℃.

[0068] This invention also provides a boron-based adsorbent prepared by the above method, comprising a hydrotalcite bulk and intercalated tartaric acid, wherein the hydrotalcite bulk comprises a plurality of stacked hydrotalcite sublayers, and the intercalated tartaric acid is intercalated between the hydrotalcite sublayers.

[0069] This invention also provides a method for adsorbing boron, comprising the following steps:

[0070] The above-mentioned boron-based adsorbents are provided.

[0071] The boron solution to be treated is brought into contact with the boron-based adsorbent to undergo an adsorption reaction, thereby achieving the adsorption of boron.

[0072] It may also include a step of separating the boron-based adsorbent from the solution after the adsorption reaction is completed.

[0073] In some embodiments, the pH of the boron solution to be treated can be 5-10, the temperature of the adsorption reaction can be 20-25°C, and the reaction time can be 2.5-3 hours.

[0074] In some embodiments, the mass-to-volume ratio of the boron-based adsorbent to the boron solution to be treated can be 1g:50mL to 1g:60mL.

[0075] In some embodiments, the adsorption method may further include the following steps:

[0076] The boron-based adsorbent after the adsorption reaction is completed is treated with an eluent to allow the boron-based adsorbent to be recycled.

[0077] In some embodiments, the eluent may be an ammonium chloride solution.

[0078] In some embodiments, the mass-to-volume ratio of the boron-based adsorbent to the eluent can be 1g:60mL-1g:70mL, and the eluent treatment is performed at a temperature of 20-25°C for 2.5-3 hours.

[0079] As a typical example, the above adsorption method can be implemented through the following implementation scheme:

[0080] 5) 0.5 g·L⁻¹ of boric acid was prepared. -1 The initial pH of the solution to be adsorbed was adjusted using HNO3 and NaOH, with the solution pH being 5-10. The prepared TA-intercalated hydrotalcite was added to a boric acid solution at a solid-liquid ratio of 1 g:60 mL. After stirring in a 20°C water bath for 3 h, the solution was filtered. The boron content in the initial solution and filtrate was measured using inductively coupled plasma atomic emission spectrometry (ICP-AES), and the adsorption capacity q was calculated.

[0081] The formula for calculating the adsorption capacity q is as follows:

[0082]

[0083] Where C0 is the initial concentration of boron; V0 is the initial volume of the solution; Ct V represents the concentration of boron in the filtrate. t denoted as ρ, where ρ is the volume of the filtrate; m is the amount of GA-LDH (i.e., boron-based adsorbent, hereinafter the same) added.

[0084] After the above adsorption process is completed, the boron-based adsorbent can still be recycled, and its regeneration method can be implemented through the following exemplary scheme:

[0085] 6) The adsorbed TA-LDH was added to NH4Cl solution at a solid-liquid ratio of 1g:60mL. After stirring in a water bath at 20℃ for 3h, the solution was filtered and washed. The boron content in the filtrate was measured by ICP-OES, and the resolution R was calculated.

[0086] The resolution R is calculated using the following formula:

[0087]

[0088] Among them, C t2 V represents the concentration of boron in the eluent. t2 This represents the volume of the eluent.

[0089] By repeating Scheme 5) and Scheme 6) above, the boron adsorbent can be recycled. When the number of cycles is 5, the adsorption and desorption amounts of the boron adsorbent do not change significantly.

[0090] The technical solution of the present invention will be further described in detail below through several embodiments and in conjunction with the accompanying drawings. However, the selected embodiments are only for illustrating the present invention and do not limit the scope of the present invention.

[0091] Example 1

[0092] First, this embodiment provides a method for preparing a boron-based adsorbent, specifically including the following steps:

[0093] 0.02 mol aluminum nitrate nonahydrate (Al(NO3)3·9H2O) and 0.04 mol magnesium nitrate hexahydrate (Mg(NO3)2·6H2O) were dissolved in 100 mL of deionized water and transferred to a 500 mL three-necked flask. 0.04 mol PA was dissolved in 300 mL of water and transferred to the same three-necked flask. Under nitrogen protection, a peristaltic pump was used at a flow rate of 6 mL / min. -1 Add 1.5 mol·L⁻¹ dropwise. -1 A sodium hydroxide solution was used to adjust the pH of the solution to 9. The entire process was carried out under stirring in a 60°C water bath. The reaction apparatus was as follows: Figure 1As shown. After stirring for another 2 hours, the mixture was transferred to a stainless steel hydrothermal reactor and aged at 20°C for 24 hours, then allowed to cool naturally to room temperature. The reaction solution was washed twice with anhydrous ethanol and twice with deionized water. The filter cake was vacuum dried at 60°C for 12 hours, then ground and sieved for later use. The sample was named TA-LDH. TA-LDH was characterized by XRD, infrared spectroscopy, and elemental analysis to confirm that TA had successfully entered the LDH interlayer.

[0094] NO3-LDH (i.e., interlayer NO3) - The XRD patterns of the hydrotalcite material (hereinafter the same) and the above-mentioned TA-LDH samples are shown below. Figure 2 As shown, the three characteristic diffraction peaks (003), (006), and (009) are very obvious in the XRD pattern of NO3-LDH, located at 10.77°, 21.85°, and 34.39° respectively, with an interlayer spacing of [missing information]. The (003), (006), and (009) diffraction peaks of the TA anion-intercalated hydrotalcite are located at 7.20°, 14.33°, and 21.72°, respectively. The (003) diffraction peak shifts to a lower angle, which is due to the introduction of larger anions into the interlayer of the hydrotalcite, resulting in a wider interlayer spacing. This indicates that the TA anion has successfully entered the interlayer space of the hydrotalcite. Comparing the XRD pattern of carboxymethyl cellulose ion-intercalated hydrotalcite prepared in a prior art (Chinese Invention Patent CN104874365 A), it can be found that the (003) diffraction peak of the TA-LDH prepared in this invention is smaller than that of its LDHs, further indicating that the TA-LDH prepared in this invention has a larger interlayer spacing, which is more conducive to the entry of B(OH)3 and B(OH)4- into the interlayer space; and the diffraction peak of the TA-LDH prepared in this invention is sharper, indicating better crystallinity and higher purity of the product.

[0095] like Figure 3 As shown, the FT-IR spectra of NO3-LDH and TA-LDH samples also confirm that TA anions have entered the interlayer of the hydrotalcite. The FT-IR spectra of NO3-LDH show a focal length of 3483.16 cm⁻¹. -1 The absorption peak at 1636.92 cm⁻¹ is the (-OH) stretching vibration peak. -1 The absorption peak at 638.59 cm⁻¹ is the (-OH) torsional vibration peak. -1 The absorption peak at 1384 cm⁻¹ is due to the (-OH) rocking vibration, while the peak at 1384 cm⁻¹ is due to the (-OH) rocking vibration. -1 The absorption peaks at this point are symmetric stretching vibration peaks of (-NO3), and these absorption peaks are characteristic peaks of NO3-LDH. In contrast, the FTIR spectrum of TA-LDH shows some new diffraction peaks: 2923.36 cm⁻¹ -1The absorption peak at 1384.61 cm⁻¹ is the asymmetric stretching vibration peak of (-CH₂). -1 The absorption peak at 1619.34 cm⁻¹ is a symmetric stretching vibration peak of (-C=O). -1 The absorption peak at 1134.07 cm⁻¹ is the asymmetric stretching vibration peak of (-C=O). -1 The absorption peak at 1089.15 cm⁻¹ is due to the stretching vibration of (-CO) and... -1 The absorption peak at [value] is the in-plane bending vibration peak of (-OH). Furthermore, compared to the TA anion, the FT-IR of TA-LDH shows (-OH) at 3457.18 cm⁻¹. -1 The contraction vibration peak and (-OH) are at 618.18 cm⁻¹. -1 A series of diffraction peaks, including the torsional vibration peak, were redshifted.

[0096] The N and C contents in NO3-LDH and TA-LDH were measured using an elemental analyzer, as shown in Table 1 below. After intercalation, the N content in TA-LDH decreased from 5.09 to 0.14, while the C content increased from 0.42 to 5.72. Under complete CO2 isolation, the carbon in LDHs could only be provided by TA anions, indicating that the NO3- ions between LDH layers had been replaced by TA anions, further confirming that TA anions were successfully intercalated into TA-LDH.

[0097] Table 1. Content of N and C elements in TA-LDH

[0098] Sample N wt.% C wt.% <![CDATA[NO3-LDH]]> 5.09 0.42 TA-LDH 0.14 5.72

[0099] Secondly, this embodiment also provides a method for boron adsorption using the above-mentioned TA-LDH, specifically including the following steps:

[0100] 0.5 g·L⁻¹ of boric acid was prepared. -1 The initial pH of the simulated solution B was adjusted to 5 using NaOH. The prepared TA-intercalated hydrotalcite (TA-LDH) was added to a boric acid solution at a solid-liquid ratio of 1 g: 60 mL. After stirring in a 20°C water bath for 3 h, the solution was filtered. The boron content in the initial solution and filtrate was measured using inductively coupled plasma atomic emission spectrometry (ICP-AES), and the adsorption capacity q was calculated using the formula described above. The obtained adsorption capacity q is as follows: Figure 4 One of the sample points is shown.

[0101] Example 2

[0102] This embodiment provides a method for preparing a boron-based adsorbent, which is basically the same as that in Example 1, except that:

[0103] Adjusting different Mg 2+ And Al3+ molar ratio of Mg 2+ ∶Al 3+ Several different boron-based adsorbents were prepared with molar ratios of 2.5:1, 3:1, 3.5:1 and 4:1 (of which 2:1 was prepared in Example 1).

[0104] The above-mentioned boron-based adsorbent was subjected to boron adsorption treatment using the same boron adsorption method as in Example 1, and the corresponding adsorption amounts were calculated. The final results are as follows: Figure 4 As shown.

[0105] from Figure 4 It is clear that a magnesium-aluminum ratio (Mg:A) of 2:1 to 4:1 exhibits good adsorption performance, and the adsorption effect is significantly better at a Mg:A ratio of 2:1 to 2.5:1 than other Mg:A ratio ranges. Elemental analysis was used to measure the mass fractions of carbon (C) and nitrogen (N) in the synthesized products at various magnesium-aluminum molar ratios, as shown in Table 2. With increasing Mg:A ratio, the C content gradually decreases, while the N content gradually increases. This indicates that with increasing Mg:A ratio, the TA anions in the hydrotalcite interlayer are gradually converted to NO3-. - This substitution is related to the charge carried by the cation exchange plates. Aluminum ions carry a higher charge than magnesium ions and have a smaller radius. The increased magnesium-aluminum ratio reduces the attraction of the plates to interlayer anions. Meanwhile, the larger TA anions require greater attraction to enter the interlayer, leading to the change of interlayer anions from TA anions to NO3-. - This further leads to a decrease in adsorption capacity.

[0106] Table 2. Content of C and N elements in hydrotalcite prepared at different Mg:Al molar ratios

[0107] Mg∶Al 2∶1 2.5∶1 3∶1 3.5∶1 4∶1 C wt.% 5.95 5.74 4.50 4.35 3.97 N wt.% 0.14 0.33 0.64 0.84 1.00

[0108] Example 3

[0109] This embodiment provides a method for preparing a boron-based adsorbent, which is basically the same as that in Example 1, except that:

[0110] Only the amount of TA added to the raw materials is adjusted so that TA reacts with Al. 3+ The molar ratios were 0.5:1, 1:1, 1.5:1, and 2.5:1 (where TA and Al were in the same molar ratio). 3+ A number of different boron-based adsorbents were prepared (with a molar ratio of 2:1 as shown in Example 1).

[0111] The above-mentioned boron-based adsorbent was subjected to boron adsorption treatment using the same boron adsorption method as in Example 1, and the corresponding adsorption amounts were calculated. The final results are as follows: Figure 5 As shown.

[0112] according to Figure 5 It is clear that as the amount of TA added increases, the adsorption capacity gradually increases, indicating that the TA anions do not completely exchange the NO3- of LDH at this point. - When the amount of TA added is twice that of aluminum ions, the adsorption capacity is basically saturated, indicating that at this point, TA anions almost completely replace NO3 in the LDH interlayer. - As can be seen, in Al 3+ A:TA ratios between 2:1 and 2:5 exhibit good adsorption effects, while Al... 3+ The adsorption effect of TA in the range of 2:4 to 2:5 is significantly better than other ranges.

[0113] Example 4

[0114] This embodiment provides a method for preparing a boron-based adsorbent, which is basically the same as that in Example 1, except that:

[0115] By adjusting the aging temperatures to 60℃, 100℃, 140℃, and 180℃, several different boron-based adsorbents were prepared.

[0116] The above-mentioned boron-based adsorbent was subjected to boron adsorption treatment using the same boron adsorption method as in Example 1, and the corresponding adsorption amounts were calculated. The final results are as follows: Figure 6 As shown.

[0117] according to Figure 6 It is clear that the boron-based adsorbents prepared by the method of this invention have good adsorption effects at aging temperatures of 20-180℃, and the adsorption effect of the adsorbents prepared at aging temperatures of 20-60℃ is significantly better than that at other temperatures.

[0118] Example 5

[0119] This embodiment provides a method for adsorbing boron using the boron-based adsorbent prepared in Example 1, which is basically the same as that in Example 1, except that:

[0120] Adjust the initial pH of the solution to be adsorbed to an integer value from 2 to 13, excluding value 5 as implemented in Example 1, and calculate the adsorption capacity at different initial pH values ​​of the solution to be adsorbed. Figure 7 As shown.

[0121] TA-LDH exhibits excellent adsorption capacity for boron within a pH range of 5-10, but the adsorption capacity decreases significantly under strong acid and strong alkaline conditions. As an alkaline material, hydrotalcite partially dissolves at pH less than 5; therefore, the adsorption capacity of TA-LDH is not ideal when the initial pH of the solution is less than 5. At pH greater than 10, intermolecular dehydration of the TA anion occurs, leading to a decrease in the content of phenolic hydroxyl groups, further reducing the adsorption capacity of TA-LDH.

[0122] Example 6

[0123] This embodiment provides a method for adsorbing boron using the boron-based adsorbent prepared in Example 1, which is basically the same as that in Example 1, except that:

[0124] Firstly, different concentrations of chloride ions were added to the boron adsorption solution: 0.5 mol / L, 0.75 mol / L, 1 mol / L, 1.25 mol / L, and 1.5 mol / L. The relationship between the adsorption capacity of TA-LDH and NO3-LDH prepared in Example 1 and the chloride ion concentration was compared as follows: Figure 8 As shown;

[0125] Secondly, different concentrations of sulfate ions were added to the boron adsorption solution, namely 0.25 mol / L, 0.375 mol / L, 0.5 mol / L, 0.625 mol / L, and 0.75 mol / L. The relationship between the adsorption capacity of TA-LDH and NO3-LDH prepared in Example 1 and the chloride ion concentration was compared as follows: Figure 9 As shown;

[0126] according to Figure 8 and Figure 9 It is clear that, compared to NO3-LDH, TA-LDH is affected by Cl... - and SO4 2- The effect of anions on the adsorption of B by TA-LDH is relatively small. The influence of anions on the adsorption of B by TA-LDH is mainly related to the interlayer anion exchangeability of LDH. - and SO4 2- This will replace the TA anions between the TA-LDH layers, reducing the active sites of TA-LDH and thus decreasing its adsorption capacity for B. The order of exchangeability of anions between the layers of hydrotalcite is CO3. 2- >SO4 2 ->HPO4 2- >F->Cl - >Br - >NO3 - >I - This indicates that it is related to Cl - Compared to SO4 2-It is easier to penetrate the interlayer of hydrotalcite and is also the least likely to be exchanged by other ions, therefore SO4 2- The effect of TA-LDH adsorption on B is much greater than that on Cl. - .

[0127] Example 7

[0128] This embodiment provides a cyclic adsorption method for the boron-based adsorbent prepared in Example 1:

[0129] Adsorption-desorption cycle experiments were conducted on the boron-based adsorbent prepared in Example 1. The adsorption conditions were: initial solution pH 8, reaction time 3 h, and initial boron concentration 500 mg / L; the desorption conditions were: NH4Cl solution concentration 0.1 mol·L⁻¹. -1 The solid-liquid ratio was 1 g:60 mL, and the desorption time was 2 h. Five cycles were performed based on this, and the adsorption capacity and desorption rate were calculated for each cycle. The results are as follows: Figure 12 As shown, with the increase of the number of cycles, the resolution stabilizes at a high level, and the adsorption capacity does not change significantly.

[0130] Figure 10 The FT-IR spectra of NO3-LDH before and after adsorption are shown at 3500 cm⁻¹. -1 The (-OH) stretching vibration peak at 1635 cm⁻¹ -1 The (-OH) torsional vibration peak at 650 cm⁻¹ -1 The (-OH) rocking vibration peak at 1380 cm⁻¹ and the peak at 1380 cm⁻¹ -1 The symmetric stretching vibration peaks of (-NO3) are characteristic peaks of NO3-LDH; NO3-LDH-B (adsorbed NO3-LDH, hereinafter the same) is at 1380 cm⁻¹. -1 The characteristic peak at the adsorption site is significantly weakened, indicating that NO3 in NO3-LDH is reduced after adsorption. - Clearly affected by B(OH)4 in the solution - The reaction mechanism of the substance being replaced is ion exchange. Figure 11 The FT-IR spectra of TA-LDH before and after adsorption are shown. Unlike NO3-LDH, TA-LDH-B (TA-LDH after adsorption, hereinafter the same) is at 1384.61 cm⁻¹. -1 The peak of symmetrical stretching vibration at (-C=O) and 1619.34 cm⁻¹ -1 The (-C=O) asymmetric stretching vibration peaks at the adsorption sites did not change significantly, indicating that the TA anion in the adsorbed TA-LDH was not reduced. This further suggests that the adsorption of B by TA-LDH is not an ion exchange, but rather a complexation reaction between the hydroxyl groups of the TA anion in the TA-LDH interlayer and B.

[0131] The changes in C and N content in LDHs shown in Table 3 further demonstrate that TA-LDH and NO3-LDH have different adsorption mechanisms. After NO3-LDH adsorbs B, the N content decreases from 5.09% to 0.97%, indicating that NO3- adsorbs NO3- from the interlayer during the adsorption process. - Gradually by B(OH)4 - The substitution further indicates that NO3-LDH is replaced by NO3. - and B(OH)4 - In contrast, TA-LDH adsorbs B through ion exchange. However, the C content did not change significantly after B adsorption, indicating that the TA anions in the interlayer of TA-LDH were not absorbed by B(OH)4 during the reaction. - The substitution further indicates that the adsorption of B by TA-LDH is due to the interaction of TA anions with B(OH)3 and B(OH)4. - The hydroxyl groups interact with each other. This adsorption mechanism makes the desorption of TA-LDH-B possible through acid washing.

[0132] Table 3. Changes in C and N content in LDH before and after adsorption.

[0133]

[0134] Comparative Example 1

[0135] The saturated adsorption capacity of the carboxymethyl cellulose ion-intercalated hydrotalcite composite material in existing technology CN104874365 A is 8 mg·g. -1 The mechanical and thermal stability of the carboxymethyl cellulose ion-intercalated hydrotalcite is slightly lower than that of the tartrate-intercalated hydrotalcite provided in this example. CN104874365 A mentions that the mechanical and thermal stability of the carboxymethyl cellulose ion-intercalated hydrotalcite composite material is beneficial for regeneration, but its regeneration mechanism is significantly different from that of this invention, and it does not provide specific regeneration methods and regeneration data.

[0136] Comparative Example 2

[0137] Reference [1] reported the preparation of gluconic acid intercalated hydrotalcite and its study on boron adsorption. It has an adsorption capacity comparable to the adsorbent in this example, but the adsorbent after adsorption cannot be regenerated.

[0138] [1]Qiu

[0139] Comparative Example 3

[0140] Reference [2] also reports the preparation of gluconate-intercalated hydrotalcite and its study on boron adsorption. Its regeneration method utilizes the memory effect of hydrotalcite. The specific operation is as follows: high-temperature calcination in marflu for 2 hours removes the compounds between the hydrotalcite layers, and then sodium gluconate is reintroduced into the hydrotalcite layers. Compared with the acid washing method disclosed in this example, the regeneration method in reference [2] cannot separate the B adsorbed in the hydrotalcite, and the high-temperature calcination requires a large amount of energy. Each regeneration also requires the reintroduction of interlayer anions, which is not conducive to the recycling of resources. This is significantly different from the treatment method in this invention, which only requires ammonium chloride for regeneration and recycling.

[0141] [2] Yan CY, Yi W T. Preparation, characterization, and boron adsorption behavior of gluconate-intercalated hydrotalcite[J]. Environmental Progress&Sustainable Energy, 2010, 29(4): 450-456.

[0142] Based on the above embodiments and test results, it is clear that the preparation conditions of the boron-based adsorbent provided by the present invention are mild, the preparation process is simple, and the tartaric acid used is extracted from plant species, which has the advantage of being environmentally friendly. The boron-based adsorbent prepared by the present invention has a wide range of applications, good adsorption effect in the pH range of 5-10, large adsorption capacity, less interference from other coexisting ions, and strong recycling performance.

[0143] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for adsorbing boron, characterized in that, include: A boron-based adsorbent is provided, the boron-based adsorbent comprising a hydrotalcite bulk and intercalated tartaric acid, the hydrotalcite bulk comprising a plurality of stacked hydrotalcite sublayers, and the intercalated tartaric acid intercalated between the hydrotalcite sublayers; The boron solution to be treated is brought into contact with the boron-based adsorbent to carry out an adsorption reaction, thereby achieving the adsorption of boron. The boron-based adsorbent is subjected to boron removal treatment using an eluent after the adsorption reaction is completed, so that the boron-based adsorbent can be recycled. The eluent is an ammonium chloride solution. The preparation method of the boron-based adsorbent includes: 1) Prepare a hydrotalcite precursor solution, wherein the hydrotalcite precursor solution contains at least aluminum ions and magnesium ions; 2) Mix the hydrotalcite precursor solution with tartaric acid to obtain the reaction precursor solution; 3) Adjust the pH of the reaction precursor solution to be alkaline so that the aluminum ions, magnesium ions and tartaric acid in the reaction precursor solution undergo a co-precipitation reaction to generate a hydrotalcite precursor. The tartaric acid is intercalated between the layers of the hydrotalcite precursor to obtain a reaction mixture. 4) The reaction mixture is aged to obtain the boron-based adsorbent.

2. The adsorption method according to claim 1, characterized in that, In step 1), the hydrotalcite precursor solution comprises an aqueous solution of aluminum salt and magnesium salt.

3. The adsorption method according to claim 2, characterized in that, The molar ratio of aluminum ions to magnesium ions in the hydrotalcite precursor solution is 1:2 to 1:2.

5. And / or, the concentration of aluminum ions in the hydrotalcite precursor solution is 0.10-0.11 mol / L.

4. The adsorption method according to claim 2, characterized in that, The aluminum salt includes any one or a combination of aluminum nitrate and aluminum chloride, and the magnesium salt includes any one or a combination of magnesium nitrate and magnesium chloride.

5. The adsorption method according to claim 1, characterized in that, Step 2) specifically includes: Prepare a tartaric acid solution, and then add the tartaric acid solution to the hydrotalcite precursor solution to obtain the reaction precursor solution.

6. The adsorption method according to claim 5, characterized in that, In the reaction precursor solution, the molar ratio of aluminum ions to tartaric acid is 1:2 to 1:2.5; The concentration of tartaric acid in the tartaric acid solution is 0.20-0.25 mol / L.

7. The adsorption method according to claim 1, characterized in that, Step 3) specifically includes: The temperature of the reaction precursor solution is maintained at 60℃-70℃, and an aqueous solution of an alkaline substance is added dropwise to the reaction precursor solution at a specific dropping rate while stirring, so that the pH value of the reaction precursor solution is adjusted to 9-10, and stirring continues to occur for the coprecipitation reaction.

8. The adsorption method according to claim 7, characterized in that, The alkaline substance includes any one or a combination of two of sodium hydroxide and potassium hydroxide; The concentration of the aqueous solution of the alkaline substance is 1-1.5 mol / L; The specific drop acceleration rate is 10-12 mL / min of alkaline aqueous solution per 1 L of the reaction precursor solution; The reaction time for the coprecipitation reaction is 2-2.5 h.

9. The adsorption method according to claim 7, characterized in that, The coprecipitation reaction was carried out under a protective atmosphere to remove carbon dioxide and oxygen; The protective atmosphere includes any one or a combination of two of nitrogen and argon.

10. The adsorption method according to claim 1, characterized in that, Step 4) specifically includes: The reaction mixture is aged at 40-60°C for 18-24 hours.

11. The adsorption method according to claim 10, characterized in that, The reaction mixture is transferred to a hydrothermal reactor for the aging process.

12. The adsorption method according to any one of claims 1-11, characterized in that, The solvents used in the preparation method are all boiled for 1-2 hours before use.

13. The adsorption method according to claim 1, characterized in that, The pH value of the boron solution to be treated is 5-10, the temperature of the adsorption reaction is 20-25℃, and the reaction time is 2.5-3h.

14. The adsorption method according to claim 1, characterized in that, The mass-to-volume ratio of the boron-based adsorbent to the boron solution to be treated is 1g:50mL-1g:60mL.

15. The adsorption method according to claim 1, characterized in that, The mass-to-volume ratio of the boron-based adsorbent to the eluent is 1g:60mL-1g:70mL, and the eluent treatment is performed at a temperature of 20-25℃ for 2.5-3 hours.

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