Modified hydrotalcite adsorbent, method for preparing the same, and use thereof

Abstract

The present application relates to the field of dephosphorization adsorbent, disclose a kind of modified hydrotalcite adsorbent and its preparation method and application, the adsorbent includes hydrotalcite and / or hydrotalcite-like compound with lamellar structure, and modification component;The modification component includes the first metal component modified on the layer of the hydrotalcite and / or hydrotalcite-like compound, and the second metal component modified in the interlayer of the hydrotalcite and / or hydrotalcite-like compound;Wherein, the first metal component is selected from transition metal and / or rare earth metal;The second metal component is selected from at least one of alkali metal.By metal modification in the layer and interlayer of hydrotalcite and / or hydrotalcite-like compound, the selectivity of adsorbent for phosphate in water can be effectively improved, and the phosphorus capacity is high, and has excellent effect in the application of dephosphorization in complex water.

Description

Technical Field

[0001] This invention relates to the field of dephosphorization adsorbents, specifically to a modified hydrotalcite-like adsorbent, its preparation method, and its application. Background Technology

[0002] Excessive phosphorus can accelerate the growth of photosynthetic aquatic organisms and algae in wastewater, leading to algal blooms and a sharp decrease in dissolved oxygen in the water. Dead plants, as they decompose, further consume dissolved oxygen, resulting in eutrophication. This is especially true for phosphorus levels in the water (expressed as PO4). 3- When the concentration (calculated) is greater than 0.3 mg / L, it will lead to a significant acceleration in algal growth.

[0003] The presence of anions in industrial water used in industrial production can affect the activity of catalysts. For example, phosphoric acid can directly influence the acid strength distribution of solid acid catalysts and form insoluble compounds with metal ions, which can also affect the reduction and use of metallic catalysts. Since industrial processes often employ continuous feeding methods, adsorption methods produce significantly less sludge compared to chemical precipitation methods, and their performance is more stable. Developing adsorption protectants with high adsorption capacity, fast adsorption rate, and strong hydrothermal stability is an important research direction.

[0004] In terms of structure, hydrotalcite-like materials possess a unique layered structure. Positively charged main layers and interlayer anions assemble into compounds through non-covalent interactions, while the weak bonding between metal ions and oxygen allows for free movement between layers. In terms of performance, they exhibit advantages such as good thermal stability, high specific surface area, high wear resistance, and environmental friendliness.

[0005] Numerous attempts have been made in the prior art to improve the adsorption performance of hydrotalcite-like materials. For example, CN113134339A discloses a zirconium-doped magnesium-iron hydrotalcite adsorbent, which increases the total adsorption capacity of the adsorbent through Zr doping. CN103127900A increases the interlayer distance of the original anionic hydrotalcite by using an anion intercalation column, and then modifies it with an alkaline metal salt, thereby increasing the gas adsorption capacity and adsorption rate of the adsorbent after calcination.

[0006] However, existing adsorbents have low phosphorus capacity, and for complex water bodies, there is a lack of effective methods to improve the adsorbent's ability to handle PO4. 3- Selective adsorption. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems of low adsorption capacity, poor phosphorus adsorption selectivity, and poor hydrothermal stability of existing adsorbents, and to provide a modified hydrotalcite-like adsorbent, its preparation method, and its application. This adsorbent has a large adsorption capacity and good phosphorus removal adsorption effect.

[0008] To achieve the above objectives, the first aspect of the present invention provides a modified hydrotalcite-like adsorbent, the adsorbent comprising hydrotalcite and / or hydrotalcite-like compounds having a layered structure, and a modifying component;

[0009] The modified components include a first metal component that modifies the hydrotalcite and / or hydrotalcite-like compound layers, and a second metal component that modifies the spaces between the hydrotalcite and / or hydrotalcite-like compound layers.

[0010] The first metal component is selected from transition metals and / or rare earth metals; the second metal component is selected from at least one alkali metal.

[0011] A second aspect of this invention provides a method for preparing a modified hydrotalcite-like adsorbent, comprising the following steps:

[0012] (1) A first solution containing a soluble compound of the main metal element A, a soluble compound of the secondary metal element B, and a soluble compound of the first metal component is brought into contact with an alkali to carry out a precipitation reaction;

[0013] (2) The product obtained in step (1) is subjected to hydrothermal crystallization, followed by washing and first drying to obtain the adsorbent precursor;

[0014] (3) The adsorbent precursor is contacted with a solution of a soluble compound containing a second metal component, and then subjected to a second drying and calcination to obtain the adsorbent;

[0015] The calcination temperature shall not exceed 600℃;

[0016] The first metal component is selected from transition metals and / or rare earth metals; the second metal component is selected from at least one alkali metal.

[0017] A third aspect of the present invention provides a modified hydrotalcite-like adsorbent prepared by the above preparation method.

[0018] The fourth aspect of this invention provides the application of the modified hydrotalcite-like adsorbent described in the first or third aspect above in continuous dephosphorization.

[0019] For hydrotalcite or hydrotalcite-like adsorbents, current technologies often increase the overall adsorption capacity by widening the interlayer spacing or fully exposing the anions between layers. However, hydrotalcite or hydrotalcite-like adsorbents do not exhibit selectivity for anions; for example, in real water bodies, the adsorption of anions is not selective except for PO4. 3- In addition, there are a large number of substances such as CO3. 2- Cl -In other words, while existing methods can improve the overall adsorption capacity, the adsorption effect on specific ions is unpredictable due to the complex composition of water bodies. The inventors of this invention have discovered that by modifying the layers and interlayers of hydrotalcite and / or hydrotalcite-like compounds with metals, a modified hydrotalcite-like adsorbent can effectively improve the selective adsorption of phosphate ions in water, exhibiting high phosphorus capacity. It demonstrates excellent performance in phosphorus removal applications in complex water bodies.

[0020] This invention utilizes co-precipitation Modified hydrotalcite-like material was successfully prepared by hydrothermal crystallization. By controlling the doping ratio and preparation conditions, an adsorbent with fast adsorption rate and large adsorption capacity was obtained, which has great economic value. Moreover, the preparation method is simple, low-cost, and easy to promote. Attached Figure Description

[0021] Figure 1 The image shows the XRD pattern of the modified hydrotalcite-like adsorbent prepared in Example 1. Detailed Implementation

[0022] 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.

[0023] The first aspect of the present invention provides a modified hydrotalcite-like adsorbent, the adsorbent comprising hydrotalcite and / or hydrotalcite-like compounds having a layered structure, and a modifying component;

[0024] The modified components include a first metal component that modifies the hydrotalcite and / or hydrotalcite-like compound layers, and a second metal component that modifies the spaces between the hydrotalcite and / or hydrotalcite-like compound layers.

[0025] The first metal component is selected from transition metals and / or rare earth metals; the second metal component is selected from at least one alkali metal.

[0026] In this invention, the hydrotalcite and / or hydrotalcite-like compounds refer to composite oxides formed by calcining hydrotalcite and / or hydrotalcite-like compounds with a layered structure. For hydrotalcite or hydrotalcite-like adsorbents, the existing technology often increases the overall adsorption capacity of the adsorbent by widening the interlayer spacing or fully exposing the interlayer anions. However, hydrotalcite or hydrotalcite-like adsorbents do not exhibit selectivity for anions; for example, in real water bodies, the adsorption of anions is not selective except for PO4. 3-In addition, there are a large number of substances such as CO3. 2- Cl - In other words, while existing methods can improve the overall adsorption capacity, the adsorption effect on specific ions is difficult to predict due to the complex composition of water bodies. The inventors of this invention discovered that by modifying the first metal component on the hydrotalcite and / or hydrotalcite-like compound layers, and by modifying the second metal component between the hydrotalcite and / or hydrotalcite-like compound layers, chemisorption is enhanced, thereby increasing the phosphorus capacity of the adsorbent and improving the selectivity of the adsorbent for phosphate.

[0027] In this invention, the characteristic peaks in the XRD pattern can prove that the modified hydrotalcite-like adsorbent in this invention still maintains a layered structure after doping modification.

[0028] In this invention, the first metal component modifies the hydrotalcite and / or hydrotalcite-like compound layers, meaning that the first metal component and the main metal element of the hydrotalcite and / or hydrotalcite-like compound together constitute a layered structure of metal hydroxide; the second metal component modifies the interlayers of the hydrotalcite and / or hydrotalcite-like compound, meaning that it is located between the hydroxide layers as a surface conditioning agent.

[0029] According to the present invention, preferably, the relative crystallinity of the adsorbent is 10-99%, more preferably 65%-88%. Within the above-mentioned preferred crystallinity range, it is beneficial to further improve the adsorption performance of the adsorbent, while excessive crystallinity may lead to a deterioration in performance.

[0030] In this invention, the relative crystallinity is calculated by the following method: the XRD spectra of the sample to be tested and the standard sample are tested respectively to determine the peak height of the highest peak, and then the relative crystallinity of the sample to be tested is calculated by substituting it into the following formula.

[0031] Relative crystallinity = I max (Sample to be tested) / I max (Standard sample) × 100%;

[0032] Among them, I max (Sample to be tested) is the peak height of the highest peak in the XRD diffraction pattern of the sample to be tested, I max (Standard sample) is the peak height of the highest peak in the XRD diffraction pattern of the standard sample.

[0033] The preparation method of the standard sample includes: weighing 12.8 g of magnesium nitrate (Mg(NO3)2·6H2O), 4.7 g of aluminum nitrate (Al(NO3)3·9H2O), and 1.93 g of lanthanum nitrate (La(NO3)3·6H2O), with a molar ratio of n(Mg):[n(Al)+n(La)]=3:1, and dissolving them in 250 mL of distilled water, which is recorded as the first solution, making the total metal concentration in the first solution 0.27 mol / L. Weighing 15 g of NaOH and 15 g of Na2CO3, and dissolving them in 300 mL of distilled water, which is recorded as the second solution. The above two solutions are added dropwise to a beaker, the pH is adjusted to about 9, and the mixture is stirred vigorously. After the reaction is complete, the slurry is transferred to a hydrothermal reactor lined with tetrafluoroethylene and hydrothermally heated at 80℃ for 12 h. After filtration, the precipitate is washed until neutral and dried in an oven at 120℃ for 2 h to obtain the XRD standard sample.

[0034] In this invention, XRD characterization can be used to measure the crystal structure and parameters of the sample. During the test, a Cu optical target is used as the radiation source, the tube voltage and tube current are set to 40.0 kV and 30.0 mA, respectively, the scanning range is set to 5-70 º, the scanning step size is set to 0.02 º, and the scanning rate is 5º / min to obtain the relevant XRD patterns.

[0035] According to the present invention, preferably, the phosphorus capacity of the adsorbent is not less than 100 mg / g, and more preferably 120-160 mg / g.

[0036] In this invention, the phosphorus content is determined by liquid chromatography-anion chromatography, specifically including: taking 1 mL of adsorbent, using 90% methanol and 10% water as solvents, dissolving 100 ppm of phosphoric acid, reacting at 80°C, with a feed rate of 0.5 mL / min and a feed density of 0.8 g / mL, taking samples every 4 hours for anion chromatography to detect the concentration, and considering adsorbent breakthrough when the phosphoric acid content in the solution exceeds 5 ppm.

[0037] Phosphorus capacity (mg / g) = (Phosphoric acid concentration in feed - Phosphoric acid concentration in discharge) × Feed rate × Breakthrough time × 1000;

[0038] The units for phosphoric acid concentration in the feed and the output are ppm by mass, the feed rate is the product of the feed rate and the feed density, and the unit is g / min. The unit for breakthrough time is min.

[0039] According to the present invention, preferably, the specific surface area of ​​the adsorbent is 10-200 m². 2 / g, preferably 50-150m 2 / g.

[0040] According to the present invention, preferably, the average pore size of the adsorbent is 1-30 nm, more preferably 5-20 nm.

[0041] According to the present invention, preferably, the pore volume of the adsorbent is not less than 0.4 cm³. 3 / g, preferably 0.6-1cm 3 / g.

[0042] In this invention, the specific surface area, average pore size, and pore volume are measured by the BET method.

[0043] In this invention, preferably, based on the total mass of the adsorbent, the content of hydrotalcite and / or hydrotalcite-like compounds is 50-99 wt%, more preferably 70-99 wt%; calculated as oxides, the content of the first metal component is 1-50 wt%, more preferably 1-30 wt%, and the content of the second metal component is 0.01-5 wt%, more preferably 0.01-1 wt%. Under these preferred conditions, it is beneficial to maintain the bilayer structure and specific surface area of ​​the hydrotalcite bulk while maximizing the modifying effect of the modified components.

[0044] For example, the mass fraction of the first metal component, calculated as an oxide, can be a typical, but not limiting, content such as 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, 20 wt%, 22 wt%, 24 wt%, 26 wt%, 28 wt%, 30 wt%. The mass fraction of the second metal component can be a typical, but not limiting, content such as 0.01 wt%, 0.02 wt%, 0.03 wt%, 0.04 wt%, 0.05 wt%, 0.06 wt%, 0.07 wt%, 0.08 wt%, 0.09 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%.

[0045] In this invention, the content of each component in the adsorbent is determined by a fluorescence semi-quantitative method.

[0046] In this invention, when the adsorbent contains only hydrotalcite and / or hydrotalcite-like compounds, a first metal component, and a second metal component, the sum of their contents satisfies 100%.

[0047] Preferably, the first metal component is selected from at least one of Zr, Ce, Fe, Co, Ni, La, Pr, Nd, Y, and Ti, more preferably from at least one of Ce, Fe, Ni, and La, and even more preferably from La. Using the above-mentioned preferred first metal component is beneficial for further improving the adsorption performance of the adsorbent.

[0048] Preferably, the second metal component is selected from at least one of Na, Li, and K. Using the aforementioned preferred second metal component is beneficial for the selective adsorption of phosphate ions.

[0049] In this invention, preferably, the hydrotalcite and / or hydrotalcite-like compound comprises a primary metal element A and a secondary metal element B. It is understood that the primary metal element A and secondary metal element B refer to the metal elements constituting the layers in the layered structure of the hydrotalcite and / or hydrotalcite-like compound.

[0050] Preferably, the molar amounts of the main metal element A, the secondary metal element B, and the first metal component satisfy the following: the ratio of the total molar amount of divalent metals to the total molar amount of trivalent metals is 1.5-4:1, preferably 2-4:1.

[0051] In this invention, it should be noted that the main metal element A is calculated as a divalent metal, the secondary metal element B is calculated as a trivalent metal, and the first metal component is calculated as a trivalent metal.

[0052] According to the present invention, the specific selection range for the main metal element A and the secondary metal element B is relatively wide, and can be a conventional selection in the art.

[0053] Preferably, the main metal element A is selected from at least one of Zn, Mg, Mn and Co.

[0054] Preferably, the secondary metal element B is selected from Al and / or Fe.

[0055] In this invention, preferably, the hydrotalcite is Mg-Al hydrotalcite; preferably, the hydrotalcite-like compound is selected from at least one of Zn-Al hydrotalcite, Mg-Fe hydrotalcite, Mn-Fe hydrotalcite, Co-Fe hydrotalcite, and Zn-Fe hydrotalcite. Using the above-preferred composition is beneficial for the formation of the hydrotalcite-like matrix.

[0056] A second aspect of this invention provides a method for preparing a modified hydrotalcite-like adsorbent, comprising the following steps:

[0057] (1) A first solution containing a soluble compound of the main metal element A, a soluble compound of the secondary metal element B, and a soluble compound of the first metal component is brought into contact with an alkali to carry out a precipitation reaction;

[0058] (2) The product obtained in step (1) is subjected to hydrothermal crystallization, followed by washing and first drying to obtain the adsorbent precursor;

[0059] (3) The adsorbent precursor is contacted with a solution of a soluble compound containing a second metal component, and then subjected to a second drying and calcination to obtain the adsorbent;

[0060] The calcination temperature shall not exceed 600℃;

[0061] The first metal component is selected from transition metals and / or rare earth metals; the second metal component is selected from at least one alkali metal.

[0062] Through coprecipitation The hydrothermal crystallization method for preparing modified hydrotalcite-like adsorbents enables the modification of a first metal component onto the hydrotalcite and / or hydrotalcite-like compound layers, while a second metal component is modified between the hydrotalcite and / or hydrotalcite-like compound layers. By controlling the calcination temperature, the adsorbent achieves a stable layered structure, resulting in a fast adsorption rate, large adsorption capacity, and excellent dephosphorization effect. This makes it highly effective for dephosphorization applications in complex water bodies.

[0063] In this invention, there are no special requirements for the specific selection of the main metal element A, the secondary metal element B, and the soluble compound of the first metal component; they can be selected from any conventional metal salt. Preferably, the main metal element A, the secondary metal element B, and the soluble compound of the first metal component are each independently selected from at least one of metal nitrates, chlorides, and organometallic salts.

[0064] In this invention, the selection range of the main metal element A, the secondary metal element B, and the first metal component is the same as that in the modified hydrotalcite adsorbent described above. The amounts of the main metal element A, the secondary metal element B, and the first metal component meet the content requirements of each component in the modified hydrotalcite adsorbent described above, and will not be repeated here.

[0065] According to the present invention, preferably, the total metal concentration in the first solution, based on elements, is 0.1-5 mol / L, more preferably 0.2-2 mol / L.

[0066] According to the present invention, preferably, the alkali is provided by a second solution containing alkali, wherein the concentration of alkali in the second solution is 0.5-5 mol / L, preferably 1-3 mol / L.

[0067] According to the present invention, preferably, the alkali includes NaOH and / or Na2CO3, and more preferably, the alkali includes NaOH and Na2CO3.

[0068] Preferably, the mass ratio of NaOH to Na2CO3 is 1:0.5-1.5.

[0069] Preferably, the first solution and the second solution each independently contain a solvent, wherein the solvent is water and / or an alcohol; the alcohol is preferably ethanol.

[0070] Preferably, the contact method in step (1) includes: adding the first solution and the second solution in parallel to each other and mixing them under stirring conditions.

[0071] In the preparation method of this invention, the stirring can be magnetic stirring, mechanical stirring, or manual stirring, etc. The stirring conditions can be determined by those skilled in the art based on the actual situation.

[0072] According to the present invention, preferably, the pH of the precipitation reaction is 5-11, more preferably 8-9; the pH of the precipitation reaction is adjusted by the amount of alkali used. Under the above preferred embodiments, it is beneficial to form an adsorbent with suitable crystallinity.

[0073] According to the present invention, the precipitation reaction is carried out in the presence of a precipitation aid. The precipitation aid is preferably introduced into the second solution.

[0074] Preferably, the precipitation aid is selected from at least one of triethylamine (TEA), polyethylene glycol (PEG, weight average molecular weight of 2000-8000), polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123), and polyvinylpyrrolidone (PVP, weight average molecular weight of 2000-8000).

[0075] Preferably, the total weight ratio of the soluble compound containing the main metal element A, the soluble compound containing the secondary metal element B, and the soluble compound containing the first metal component to the precipitating agent is 10-30:1.

[0076] In this invention, the hydrothermal crystallization can be carried out under conventional operating conditions in the art, which are well known to those skilled in the art. Preferably, the conditions for hydrothermal crystallization include: a reaction temperature of 60-200℃, more preferably 80-180℃, and a reaction time of 1-48h, more preferably 2-24h.

[0077] Preferably, the hydrothermal crystallization is carried out under microwave radiation conditions, for example, a conventional microwave synthesizer can be used for the reaction, wherein the microwave frequency is preferably 2.45 GHz.

[0078] Preferably, the microwave power is 500-2000W.

[0079] In this invention, the washing and first drying can be carried out under conventional operating conditions in the art. Preferably, the conditions for the first drying include: a temperature of 40-200°C, more preferably 80-150°C, and a drying time of 0.5-5 hours, more preferably 1-3 hours.

[0080] In this invention, the preparation method further includes: grinding and sieving the first dried product to obtain the adsorbent precursor. The grinding and sieving conditions can be determined by those skilled in the art based on actual application needs.

[0081] Preferably, the particle size of the adsorbent precursor is 80-120 mesh.

[0082] According to the present invention, preferably, the conditions for the second drying include: a temperature of 40-200°C, preferably 80-150°C, and a drying time of 0.5-5h, preferably 0.5-3h.

[0083] Preferably, the calcination temperature is 300-500℃, and the calcination time is 1-5 hours. Using these preferred calcination conditions is beneficial for forming composite oxides with a memory effect.

[0084] A third aspect of the present invention provides a modified hydrotalcite-like adsorbent prepared by the above preparation method.

[0085] The fourth aspect of this invention provides the application of the modified hydrotalcite-like adsorbent described in the first or third aspect above in continuous dephosphorization.

[0086] According to the present invention, preferably, the continuous dephosphorization includes contacting the phosphorus-containing solution with a modified hydrotalcite-like adsorbent.

[0087] Preferably, the phosphorus content in the phosphorus-containing solution, calculated as phosphoric acid, is 10-200 ppm, more preferably 50-100 ppm;

[0088] Preferably, the contact conditions include: a contact temperature of 40-120°C, more preferably 70-90°C; and a volume hourly space velocity (VHSV) of 10-200 h⁻¹ for the phosphorus-containing solution. -1 Preferably 20-100h -1 .

[0089] The present invention will be described in detail below through embodiments.

[0090] In the following examples, all raw materials used were commercially available.

[0091] Example 1

[0092] (1) Weigh 12.8g of magnesium nitrate (Mg(NO3)2·6H2O), 4.7g of aluminum nitrate (Al(NO3)3·9H2O), and 2.7g of lanthanum nitrate (La(NO3)3·6H2O), with a molar ratio of n(Mg):[n(Al)+n(La)]=2.7:1. Dissolve these in 250mL of distilled water, and record this as the first solution, making the total metal concentration in the first solution 0.27 mol / L. Weigh 15g of NaOH and 15g of Na2CO3, dissolve them in 300mL of distilled water, making the alkali concentration 1.72 mol / L. Add 2g of PEG (weight-average molecular weight 8000), and record this as the second solution. The two solutions were added dropwise to a beaker, the pH was adjusted to approximately 8.5, and the mixture was stirred vigorously. After the reaction was complete, the slurry was transferred to a tetrafluoroethylene-lined hydrothermal reactor and placed in a microwave synthesizer at 1500W and 120℃ for 6 hours. The mixture was filtered, the precipitate was washed until neutral, and dried in an oven at 80℃ for 2 hours. After drying, the precipitate was ground into powder and sieved through an 80-120 mesh sieve to obtain the adsorbent precursor.

[0093] 0.09 g of KNO3 was dissolved in 5 mL of deionized water and impregnated with the adsorbent precursor. The solution was dried at 120 °C for 1 h and calcined at 500 °C for 2 h to obtain the product adsorbent A1. The physicochemical data of A1 are shown in Table 1.

[0094] Preparation of XRD standards:

[0095] Weigh 12.8 g of magnesium nitrate (Mg(NO3)2·6H2O), 4.7 g of aluminum nitrate (Al(NO3)3·9H2O), and 1.93 g of lanthanum nitrate (La(NO3)3·6H2O), with a molar ratio of n(Mg):[n(Al)+n(La)]=3:1. Dissolve these in 250 mL of distilled water, and this solution is designated as the first solution, resulting in a total metal concentration of 0.27 mol / L. Weigh 15 g of NaOH and 15 g of Na2CO3, and dissolve them in 300 mL of distilled water, designating this solution as the second solution. Add both solutions dropwise to a beaker, adjust the pH to approximately 9, and stir vigorously. After the reaction is complete, transfer the slurry to a tetrafluoroethylene-lined hydrothermal reactor and incubate at 80 °C for 12 h. Filter the solution, wash the precipitate until neutral, and dry it in an oven at 120 °C for 2 h to obtain an XRD standard. The XRD patterns of the test sample and the standard sample were tested separately, such as... Figure 1 As shown in Table 1, the peak height of the highest peak was determined, and the relative crystallinity of A1 was calculated.

[0096] (2) Determination of adsorption performance

[0097] The prepared adsorbent was evaluated in a fixed-bed reactor. 1 mL of the adsorbent was dissolved in 90% methanol and 10% water (by weight) to obtain 100 ppm of phosphoric acid. The reaction temperature was 80 °C, the feed rate was 0.5 mL / min, and the feed density was 0.8 g / mL. Samples were taken every 4 hours and sent to anion exchange chromatography to detect the concentration. Adsorbent breakthrough was considered to have occurred when the phosphoric acid content in the solution exceeded 5 ppm.

[0098] Phosphorus capacity (mg / g) = (Phosphoric acid concentration in feed - Phosphoric acid concentration in discharge) × Feed rate × Breakthrough time × 1000;

[0099] The units for phosphoric acid concentration in the feed and the output are ppm by mass, the feed rate is the product of the feed rate and the feed density, and the unit is g / min. The unit for breakthrough time is min.

[0100] The calculation results are shown in Table 1.

[0101] Example 2

[0102] (1) Preparation of adsorbent

[0103] Weigh 27.5g of zinc nitrate (Zn(NO3)2·6H2O), 8g of aluminum nitrate (Al(NO3)3·9H2O), and 3g of lanthanum nitrate (La(NO3)3·6H2O), with a molar ratio of n(Zn):[n(Al)+n(La)]=3.2:1. Dissolve these in 400mL of distilled water, and this solution is designated as the first solution. The total metal concentration in the first solution is 0.3mol / L. Weigh 30g of NaOH and 30g of Na2CO3, and dissolve them in 400mL of distilled water to make the alkali concentration 2.58 mol / L. Add 2.5g of TEA, and this solution is designated as the second solution. Add both solutions dropwise to a beaker, adjust the pH to approximately 8, and stir vigorously. After the reaction is complete, transfer the slurry to a tetrafluoroethylene-lined hydrothermal reactor and place it in a microwave synthesizer at 1500W microwave power and 120℃ for 8 hours. After centrifugation, the precipitate was collected, washed until neutral, dried in an oven at 110℃ for 1.5 hours, ground into powder, and passed through a 100-mesh sieve to obtain the adsorbent precursor.

[0104] 0.3 g of LiNO3 was dissolved in 5 mL of deionized water and impregnated with the adsorbent precursor. The solution was dried at 120 °C for 1 h and calcined at 480 °C for 2 h. The product adsorbent A2 was obtained. The physicochemical data of A2 are shown in Table 1.

[0105] Using the XRD standard sample from Example 1, the XRD spectra of A2 and the standard sample were tested respectively to determine the peak height of the highest peak and calculate the relative crystallinity of A2. The results are shown in Table 1.

[0106] (2) Determination of adsorption performance

[0107] The evaluation method is the same as in Example 1, and the calculation results are shown in Table 1.

[0108] Example 3

[0109] A mixed metal solution was prepared by dissolving 20g of Mg(NO3)2·6H2O, 3.5g of Fe(NO3)3·9H2O, and 5g of Ce(NO3)3·6H2O in 500mL of deionized water, with a molar ratio of n(Mg):[n(Fe)+n(Ce)]=3.9:1, denoted as the first solution. A second solution was prepared by dissolving 20g of NaOH and 20g of Na2CO3 in 240mL of distilled water to achieve a base concentration of 2.87mol / L, followed by the addition of 2.0g of TEA. Both solutions were added dropwise to a beaker, adjusting the pH to approximately 8.5, and stirring vigorously. After the reaction was complete, the slurry was transferred to a tetrafluoroethylene-lined hydrothermal reactor and placed in a microwave synthesizer at 1500W for 8 hours at 120℃. The mixture was then centrifuged and washed until the pH reached approximately 7, dried at 120℃ for 3 hours, and ground through a 100-mesh sieve to obtain the adsorbent precursor.

[0110] 0.13 g of LiNO3 was dissolved in 5 mL of deionized water and impregnated with the adsorbent precursor. The solution was dried at 120 °C for 1 h and calcined at 380 °C for 3 h. The product adsorbent A3 was obtained. The physicochemical data of A3 are shown in Table 1.

[0111] Using the XRD standard sample from Example 1, the XRD spectra of A3 and the standard sample were tested respectively to determine the peak height of the highest peak and calculate the relative crystallinity of A3. The results are shown in Table 1.

[0112] The adsorption performance was tested using the same test method as in Example 1, and the results are shown in Table 1.

[0113] Example 4

[0114] (1) Weigh 16g of magnesium nitrate (Mg(NO3)2·6H2O), 5g of aluminum nitrate (Al(NO3)3·9H2O), and 2.7g of lanthanum nitrate (La(NO3)3·6H2O), with a molar ratio of n(Mg):[n(Al)+n(La)]=3.2:1. Dissolve these in 500mL of distilled water and record this as the first solution. Weigh 25g of NaOH and 25g of Na2CO3, dissolve them in 500mL of distilled water, and add 2.0g of PEG (weight-average molecular weight of 8000) to the solution. Record this as the second solution. Add the two solutions dropwise to a beaker, adjust the pH to about 8, and stir vigorously. After the reaction is complete, transfer the slurry to a tetrafluoroethylene-lined hydrothermal reactor and place it in a microwave synthesizer. The microwave power is 1500W, and the mixture is hydrothermally heated at 120℃ for 5 hours. Filter the precipitate, wash it until neutral, dry it in an oven at 100℃ for 3 hours, grind it into powder, and sieve it through an 80-120 mesh sieve to obtain the adsorbent precursor.

[0115] 0.12 g of LiNO3 was dissolved in 5 mL of deionized water and impregnated with the adsorbent precursor. The solution was dried at 120 °C for 1 h and calcined at 450 °C for 2 h. The product adsorbent A4 was obtained. The physicochemical data of A4 are shown in Table 1.

[0116] Using the XRD standard sample from Example 1, the XRD spectra of A4 and the standard sample were tested respectively to determine the peak height of the highest peak and calculate the relative crystallinity of A4. The results are shown in Table 1.

[0117] (2) Determination of adsorption performance

[0118] The evaluation method is the same as in Example 1, and the calculation results are shown in Table 1.

[0119] Example 5

[0120] The method was followed as in Example 4, except that the calcination temperature was 700°C. The resulting adsorbent product, A5, has physicochemical data shown in Table 1.

[0121] Using the XRD standard sample from Example 1, the XRD spectra of A5 and the standard sample were tested respectively to determine the peak height of the highest peak and calculate the relative crystallinity of A5. The results are shown in Table 1.

[0122] The adsorption performance was tested using the same test method as in Example 1, and the results are shown in Table 1.

[0123] Example 6

[0124] Weigh out 16g of magnesium nitrate (Mg(NO3)2·6H2O), 5g of aluminum nitrate (Al(NO3)3·9H2O), and 3.0g of nickel nitrate (Ni(NO3)2·6H2O), with a molar ratio of n(Mg):[n(Al)+n(Ni)]=3.2:1. Dissolve these in 500mL of distilled water, and this solution is designated as the first solution. Weigh out 25g of NaOH and 25g of Na2CO3, and dissolve them in 500mL of distilled water, resulting in an alkali concentration of 1.72mol / L. Add 2.0g of PEG (weight-average molecular weight 8000), and this solution is designated as the second solution. Add both solutions dropwise to a beaker, adjust the pH to approximately 8, and stir vigorously. After the reaction is complete, transfer the slurry to a tetrafluoroethylene-lined hydrothermal reactor and place it in a microwave synthesizer at 1500W microwave power and 120℃ for 5 hours. Filter the precipitate, wash it until neutral, dry it in an oven at 100℃ for 3 hours, grind it into powder, and sieve it through an 80-120 mesh sieve to obtain the adsorbent precursor.

[0125] 0.12 g of LiNO3 was dissolved in 5 mL of deionized water and impregnated with the adsorbent precursor. The solution was dried at 120 °C for 1 h and calcined at 450 °C for 2 h. The product adsorbent A6 was obtained. The physicochemical data of A6 are shown in Table 1.

[0126] Using the XRD standard sample from Example 1, the XRD spectra of A6 and the standard sample were tested respectively to determine the peak height of the highest peak and calculate the relative crystallinity of A6. The results are shown in Table 1.

[0127] The adsorption performance was tested using the same test method as in Example 1, and the results are shown in Table 1.

[0128] Example 7

[0129] The method is the same as in Example 1, except that the amount of KNO3 used is 0.5g.

[0130] The adsorbent A7 was obtained. The physicochemical data of A7 are shown in Table 1. Using the XRD standard from Example 1, the XRD spectra of A7 and the standard were tested respectively to determine the peak height of the highest peak and calculate the relative crystallinity of A7. The results are shown in Table 1.

[0131] The adsorption performance was tested using the same test method as in Example 1, and the results are shown in Table 1.

[0132] Example 8

[0133] (1) Weigh 16g of magnesium nitrate (Mg(NO3)2·6H2O), 5g of aluminum nitrate (Al(NO3)3·9H2O), and 2.7g of lanthanum nitrate (La(NO3)3·6H2O), with a molar ratio of n(Mg):[n(Al)+n(La)]=3.2:1. Dissolve these in 500mL of distilled water and record this as the first solution. Weigh 25g of NaOH and dissolve it in 500mL of distilled water. The concentration of the alkali is 1.25mol / L. Add 2.0g of PEG (weight-average molecular weight of 8000) and record this as the second solution. Add the two solutions dropwise to a beaker, adjust the pH to about 8, and stir vigorously. After the reaction is complete, transfer the slurry to a hydrothermal reactor lined with tetrafluoroethylene and place it in a microwave synthesizer. The microwave power is 1500W, and the mixture is hydrothermally heated at 120℃ for 5 hours. Filter the precipitate, wash it until neutral, dry it in an oven at 100℃ for 3 hours, grind it into powder, and sieve it through an 80-120 mesh sieve to obtain the adsorbent precursor.

[0134] 0.12 g of LiNO3 was dissolved in 5 mL of deionized water and impregnated with the adsorbent precursor. The solution was dried at 120 °C for 1 h and calcined at 450 °C for 2 h. The product adsorbent A8 was obtained. The physicochemical data of A8 are shown in Table 1.

[0135] Using the XRD standard sample from Example 1, the XRD spectra of A8 and the standard sample were tested respectively to determine the peak height of the highest peak and calculate the relative crystallinity of A8. The results are shown in Table 1.

[0136] (2) Determination of adsorption performance

[0137] The evaluation method is the same as in Example 1, and the calculation results are shown in Table 1.

[0138] Comparative Example 1

[0139] (1) Weigh 15g of magnesium nitrate (Mg(NO3)2·6H2O), 6g of aluminum nitrate (Al(NO3)3·9H2O), and 2g of lanthanum nitrate (La(NO3)3·6H2O), with a molar ratio of n(Mg):[n(Al)+n(La)]=2.8:1. Dissolve these in 300mL of distilled water and record this as the first solution. The total metal concentration in the first solution is 0.26mol / L. Weigh 16g of NaOH and 16g of Na2CO3 and dissolve them in 200mL of distilled water. The alkali concentration is 2.75mol / L, and this is recorded as the second solution. Add the two solutions dropwise to a beaker, adjust the pH to about 10, and stir vigorously. After the reaction is complete, age for 6 hours. Wash the precipitate until neutral, dry it in an oven at 80℃ for 2 hours, grind it into powder, and sieve it through an 80-120 mesh sieve to obtain the adsorbent precursor. Calcine at 480℃ for 2 hours. The adsorbent DA1 was obtained, and its physicochemical data are shown in Table 1.

[0140] Using the XRD standard sample from Example 1, the XRD spectra of DA1 and the standard sample were tested respectively to determine the peak height of the highest peak and calculate the relative crystallinity of DA1. The results are shown in Table 1.

[0141] (2) Determination of adsorption performance

[0142] The evaluation method is the same as in Example 1, and the calculation results are shown in Table 1.

[0143] Comparative Example 2

[0144] (1) Weigh 20g of magnesium nitrate (Mg(NO3)2·6H2O) and 10g of aluminum nitrate (Al(NO3)3·9H2O), with a molar ratio of n(Mg):n(Al) = 2.9:1. Dissolve them in 500mL of distilled water and record this as the first solution. The total metal concentration in the first solution is 0.21mol / L. Weigh 25g of NaOH and 25g of Na2CO3 and dissolve them in distilled water in a 500mL beaker. The concentration of the alkali is 1.72mol / L and this is recorded as the second solution. Add the two solutions dropwise to the beaker, adjust the pH to about 10, and stir vigorously. After the reaction is complete, age for 6 hours. Wash the precipitate until neutral, dry it in an oven at 80℃ for 2 hours, grind it into powder, and sieve it through an 80-120 mesh sieve to obtain the adsorbent precursor.

[0145] 0.1 g of KNO3 was dissolved in 5 mL of deionized water and impregnated with the adsorbent precursor. The solution was dried at 120 °C for 1 h and calcined at 480 °C for 2 h. The product adsorbent DA2 was obtained. The physicochemical data of DA2 are shown in Table 1.

[0146] Using the XRD standard sample from Example 1, the XRD spectra of DA2 and the standard sample were tested respectively to determine the peak height of the highest peak and calculate the relative crystallinity of DA2. The results are shown in Table 1.

[0147] (2) Determination of adsorption performance

[0148] The evaluation method is the same as in Example 1, and the calculation results are shown in Table 1.

[0149] Table 1

[0150]

[0151] Test case

[0152] To investigate the effect of coexisting ions on phosphate adsorption, the prepared adsorbent was evaluated in a fixed-bed reactor. 1 mL of sample was dissolved in 90% methanol and 10% water (by weight) to obtain 100 ppm of phosphate and SO42-. 2- The content is 50 ppm, Cl -The concentration was 50 ppm, the reaction temperature was 80℃, the feed rate was 0.5 mL / min, and the feed density was 0.8 g / mL. Samples were taken every 4 hours for anion chromatography to detect the concentration. The adsorbent was considered to have broken through when the phosphoric acid content in the solution exceeded 5 ppm. The calculation results are shown in Table 2.

[0153] Phosphorus capacity of coexisting ion solution (mg / g) = (phosphoric acid concentration of coexisting ion solution - phosphoric acid concentration at discharge port) × feed rate × breakthrough time × 1000;

[0154] The units for the coexisting ion solution phosphoric acid concentration and the outlet phosphoric acid concentration are ppm (mass), the feed rate is the product of the feed rate and the feed density, and the unit is g / min. The unit for the breakthrough time is min.

[0155] Phosphorus capacity retention (%) = Phosphorus capacity of coexisting ionic liquid / Phosphorus capacity × 100%.

[0156] Table 2

[0157]

[0158] The results in Tables 1 and 2 show that the modified hydrotalcite-like adsorbent provided by this invention can effectively improve the selective adsorption of phosphate in water, has a high phosphorus capacity, and has a high phosphorus capacity retention rate in complex water bodies, indicating that the adsorbent has a good selective adsorption effect on phosphorus.

[0159] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A modified hydrotalcite-like adsorbent, characterized in that, The adsorbent comprises hydrotalcite and / or hydrotalcite-like compounds having a layered structure, as well as modifying components; The modified components include a first metal component that modifies the hydrotalcite and / or hydrotalcite-like compound layers, and a second metal component that modifies the spaces between the hydrotalcite and / or hydrotalcite-like compound layers. The adsorbent is obtained by the following preparation method: (1) a first solution containing a soluble compound of the main metal element A, a soluble compound of the secondary metal element B and a soluble compound of the first metal component is contacted with an alkali to carry out a precipitation reaction; (2) The product obtained in step (1) is subjected to hydrothermal crystallization, followed by washing and first drying to obtain the adsorbent precursor; (3) The adsorbent precursor is contacted with a solution of a soluble compound containing a second metal component, and then subjected to a second drying and calcination to obtain the adsorbent; The calcination temperature shall not exceed 600℃; The soluble compounds of the main metal element A, the soluble compounds of the secondary metal element B, and the soluble compounds of the first metal component are each independently selected from at least one of the metal nitrates, chlorides, and organometallic salts. The first metal component is selected from at least one of Zr, Ce, Fe, Co, Ni, La, Pr, Nd, Y and Ti; the second metal component is selected from at least one of Na, Li and K.

2. The adsorbent according to claim 1, wherein, The phosphorus capacity of the adsorbent is not less than 100 mg / g; And / or, the specific surface area of ​​the adsorbent is 10-200 m². 2 / g; And / or, the average pore size of the adsorbent is 1-30 nm; And / or, the pore volume of the adsorbent is not less than 0.4 cm³. 3 / g.

3. The adsorbent according to claim 2, wherein, The phosphorus capacity of the adsorbent is 120-160 mg / g; And / or, the specific surface area of ​​the adsorbent is 50-150 m². 2 / g; And / or, the average pore size of the adsorbent is 5-20 nm; And / or, the pore volume of the adsorbent is 0.6-1 cm³. 3 / g.

4. The adsorbent according to claim 1, wherein, The relative crystallinity of the adsorbent is 10-99%.

5. The adsorbent according to claim 4, wherein, The relative crystallinity of the adsorbent is 65-88%.

6. The adsorbent according to claim 1, wherein, Based on the total mass of the adsorbent, the content of hydrotalcite and / or hydrotalcite-like compounds is 50-99 wt%; based on oxides, the content of the first metal component is 1-50 wt%, and the content of the second metal component is 0.01-5 wt%. And / or, the first metal component is selected from at least one of Ce, Fe, Ni and La.

7. The adsorbent according to claim 6, wherein, Based on the total mass of the adsorbent, the content of hydrotalcite and / or hydrotalcite-like compounds is 70-99 wt%; based on oxides, the content of the first metal component is 1-30 wt%, and the content of the second metal component is 0.01-1 wt%. And / or, the first metal component is La.

8. The adsorbent according to claim 1, wherein, The hydrotalcite and / or hydrotalcite-like compounds contain a main metal element A and a secondary metal element B.

9. The adsorbent according to claim 8, wherein, The molar amounts of the main metal element A, the secondary metal element B, and the first metal component satisfy the following: the ratio of the total molar amount of divalent metals to the total molar amount of trivalent metals is 1.5-4:1; And / or, the main metallic element A is selected from at least one of Zn, Mg, Mn and Co; And / or, the secondary metal element B is selected from Al and / or Fe; And / or, the hydrotalcite is Mg-Al hydrotalcite; And / or, the hydrotalcite-like compound is selected from at least one of Zn-Al hydrotalcite, Mg-Fe hydrotalcite, Mn-Fe hydrotalcite, Co-Fe hydrotalcite and Zn-Fe hydrotalcite.

10. A method for preparing a modified hydrotalcite-like adsorbent, characterized in that, Includes the following steps: (1) A first solution containing a soluble compound of the main metal element A, a soluble compound of the secondary metal element B, and a soluble compound of the first metal component is brought into contact with an alkali to carry out a precipitation reaction; (2) The product obtained in step (1) is subjected to hydrothermal crystallization, followed by washing and first drying to obtain the adsorbent precursor; (3) The adsorbent precursor is contacted with a solution of a soluble compound containing a second metal component, and then subjected to a second drying and calcination to obtain the adsorbent; The calcination temperature shall not exceed 600℃; The soluble compounds of the main metal element A, the soluble compounds of the secondary metal element B, and the soluble compounds of the first metal component are each independently selected from at least one of the metal nitrates, chlorides, and organometallic salts. The first metal component is selected from at least one of Zr, Ce, Fe, Co, Ni, La, Pr, Nd, Y and Ti; the second metal component is selected from at least one of Na, Li and K.

11. The preparation method according to claim 10, wherein, In the first solution, the total metal concentration, based on elemental composition, is 0.1-5 mol / L; And / or, the molar amounts of the main metal element A, the secondary metal element B, and the first metal component satisfy the following: the ratio of the total molar amount of divalent metals to the total molar amount of trivalent metals is 1.5-4:1; And / or, the main metallic element A is selected from at least one of Zn, Mg, Mn and Co; And / or, the secondary metal element B is selected from Al and / or Fe.

12. The preparation method according to claim 10, wherein, The alkali is provided through a second solution containing alkali, wherein the concentration of alkali in the second solution is 0.5-5 mol / L.

13. The preparation method according to claim 12, wherein, In the second solution, the concentration of alkali is 1-3 mol / L.

14. The preparation method according to claim 10, wherein, The base is selected from NaOH and / or Na2CO3.

15. The preparation method according to claim 14, wherein, The alkali is NaOH and Na2CO3.

16. The preparation method according to claim 15, wherein, The mass ratio of NaOH to Na2CO3 is 1:0.5-1.

5.

17. The preparation method according to claim 10, wherein, The pH of the precipitation reaction is 5-11.

18. The preparation method according to claim 17, wherein, The pH of the precipitation reaction is 8-9.

19. The preparation method according to claim 10, wherein, The precipitation reaction is carried out in the presence of a precipitation aid.

20. The preparation method according to claim 19, wherein, The precipitation aid is selected from at least one of triethylamine, polyethylene glycol, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, and polyvinylpyrrolidone.

21. The preparation method according to claim 10, wherein, The total weight ratio of the soluble compound containing the main metal element A, the soluble compound containing the secondary metal element B, and the soluble compound containing the first metal component to the precipitating agent is 10-30:

1.

22. The preparation method according to claim 10, wherein, The conditions for hydrothermal crystallization include: a reaction temperature of 60-200℃ and a reaction time of 1-48h.

23. The preparation method according to claim 22, wherein, The conditions for hydrothermal crystallization include: a reaction temperature of 80-180℃ and a reaction time of 2-24h.

24. The preparation method according to claim 10, wherein, The hydrothermal crystallization is carried out under microwave radiation conditions, with a microwave power of 500-2000W. And / or, the conditions for the first drying include: a temperature of 40-200°C and a drying time of 0.5-5 hours.

25. The preparation method according to claim 10, wherein, The amounts of the first metal component and the second metal component are such that, in the prepared adsorbent, the mass ratio of the first metal component and the second metal component, calculated as oxides, is 10-20:

1.

26. The preparation method according to claim 10, wherein, The amounts of the soluble compounds of the main metal element A, the soluble compounds of the secondary metal element B, the soluble compounds of the first metal component, and the soluble compounds of the second metal component are such that the content of hydrotalcite and / or hydrotalcite-like compounds in the prepared adsorbent is 50-99 wt%. Based on oxides, the content of the first metal component is 1-50 wt%, and the content of the second metal component is 0.01-5 wt%. And / or, the first metal component is selected from at least one of Ce, Fe, Ni and La; And / or, the conditions for the second drying include: a temperature of 40-200°C and a drying time of 0.5-5 hours; And / or, the calcination temperature is 300-500℃, and the calcination time is 1-5h.

27. The preparation method according to claim 26, wherein, The amounts of the soluble compounds of the main metal element A, the soluble compounds of the secondary metal element B, the soluble compounds of the first metal component, and the soluble compounds of the second metal component are such that the content of hydrotalcite and / or hydrotalcite-like compounds in the prepared adsorbent is 70-99 wt%. Based on oxides, the content of the first metal component is 1-30 wt%, and the content of the second metal component is 0.01-1 wt%. And / or, the first metal component is La.

28. The modified hydrotalcite-like adsorbent prepared by the preparation method according to any one of claims 10-27.

29. The application of the modified hydrotalcite-like adsorbent according to any one of claims 1-9 and 28 in continuous dephosphorization.

30. The application according to claim 29, wherein, The continuous dephosphorization process involves contacting a phosphorus-containing solution with a modified hydrotalcite-like adsorbent.

31. The application according to claim 30, wherein, The phosphorus content in the phosphoric acid solution is 10-200 ppm, calculated as phosphoric acid. And / or, the contact conditions include: a contact temperature of 40-120°C; and a volume hourly space velocity (VHSV) of 10-200 h⁻¹ for the phosphorus-containing solution. -1 .

32. The application according to claim 31, wherein, The phosphorus content in the phosphorus-containing solution, calculated as phosphoric acid, is 50-100 ppm; And / or, the contact conditions include: a contact temperature of 70-90°C; and a volume hourly space velocity (VHSV) of 20-100 h⁻¹ for the phosphorus-containing solution. -1 .

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