A porous network lanthanum oxycarbonate phosphorus adsorbent, its preparation method and application

Abstract

This invention provides a porous network lanthanum oxycarbonate phosphorus adsorbent, its preparation method, and its applications, relating to the fields of environmental functional material preparation and wastewater treatment technology. The preparation method of the porous network lanthanum oxycarbonate phosphorus adsorbent provided by this invention includes the following steps: mixing a lanthanum-based compound, an organic polymer compound, and a solvent, and freezing to obtain a solid mixture; sequentially subjecting the solid mixture to vacuum freeze-drying and pyrolysis to obtain the porous network lanthanum oxycarbonate phosphorus adsorbent. The La2CO5 prepared by this invention is less prone to aggregation under the support of the organic carbon chain framework, providing more active sites and thus improving phosphorus adsorption efficiency.

Description

Technical Field

[0001] This invention relates to the fields of environmental functional materials preparation and wastewater treatment technology, specifically to a porous network lanthanum oxycarbonate phosphorus absorbent, its preparation method, and its application. Background Technology

[0002] Excessive phosphorus (P) in water can alter the chemical properties of lakes (reservoirs) and other water bodies, disrupting the ecological balance and endangering human health. Current research confirms that various metal oxides and their modified forms have excellent adsorption capacity for P, especially some high-valence metal cations, such as La. 3+ Fe 3+ A1 3+ They are related to PO4 3- The binding ability between these compounds is more pronounced, with lanthanum (La)-based compounds exhibiting the highest adsorption capacity for phosphorus (P). Many researchers have used lanthanum hydroxide (La(OH)3) as a target lanthanum-based compound for P adsorption. However, La(OH)3 can only be produced under alkaline conditions, thus limiting its application. In contrast, lanthanum oxycarbonate (La2CO5) is chemically stable, insoluble in water, and non-toxic, therefore its preparation does not require alkaline conditions, making its applications more extensive. Currently, reported methods for preparing La2CO5 include solid-phase methods, sol-gel methods, hydrothermal methods, and solvothermal methods.

[0003] However, if La2CO5 is loaded on a poorly dispersible support, the La2CO5 particles are prone to agglomeration, which leads to the masking of internal La sites and low adsorption capacity for P. Summary of the Invention

[0004] The purpose of this invention is to provide a porous network lanthanum oxycarbonate phosphorus adsorbent, its preparation method, and its application. In this invention, lanthanum oxycarbonate is not only distributed on the outer surface of the organic framework carbon chain, but also interspersed inside the organic framework carbon chain. The La2CO5 prepared by this invention is not prone to aggregation under the support structure of the organic framework carbon chain, and can provide more active sites, thereby improving phosphorus adsorption efficiency.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing a porous network lanthanum oxycarbonate phosphorus adsorbent, comprising the following steps:

[0007] A lanthanide compound, an organic polymer compound, and a solvent were mixed and then frozen to obtain a solid mixture.

[0008] The solid mixture was subjected to vacuum freeze-drying and pyrolysis in sequence to obtain a porous network lanthanum oxycarbonate phosphorus adsorbent.

[0009] Preferably, the mass ratio of the lanthanide compound to the organic polymer compound is 2-5:2-5.

[0010] Preferably, the lanthanide compound includes one or more of lanthanum chloride, lanthanum nitrate, and lanthanum acetate.

[0011] Preferably, the organic polymeric compound includes one or more of polyvinylpyrrolidone, polyethylene glycol, and polyvinyl alcohol.

[0012] Preferably, the solvent includes one of water, ethanol, and methanol.

[0013] Preferably, the freezing temperature is -18 to -25°C, and the freezing time is 7 to 11 hours.

[0014] Preferably, the vacuum freeze-drying temperature is -60 to -160°C; and the vacuum freeze-drying time is 10 to 24 hours.

[0015] Preferably, the pyrolysis temperature is 300–600°C, and the holding time is 1.5–4 hours; the pyrolysis is carried out in a protective atmosphere.

[0016] The present invention provides a porous network lanthanum oxycarbonate phosphorus absorbent prepared by the preparation method described above, comprising an organic framework carbon chain and lanthanum oxycarbonate distributed on the organic framework carbon chain.

[0017] This invention provides the application of the porous mesh lanthanum oxycarbonate phosphorus adsorbent described above in the removal of phosphorus from wastewater.

[0018] This invention provides a method for preparing a porous network of lanthanum oxycarbonate phosphorus adsorbent. The method employs vacuum freeze-drying and pyrolysis to prepare La2CO5 uniformly grown on an organic framework carbon chain. During pyrolysis, the organic polymer forms an organic framework carbon chain and generates gas. This gas penetrates the material from the interior to the surface, forming a porous structure. Simultaneously, lanthanum ions coordinate with the C and O atoms on the organic polymer to form La-C / O coordination bonds, ultimately generating lanthanum oxycarbonate. Therefore, La2CO5 is not only distributed on the outer surface of the organic framework carbon chain but also interspersed within it. The La2CO5 prepared by this invention is less prone to aggregation under the support of the organic framework carbon chain, providing more active sites and thus improving phosphorus adsorption efficiency. Attached Figure Description

[0019] Figure 1 The morphology and mapping diagram of the porous network lanthanum oxycarbonate phosphorus adsorbent prepared in Example 1;

[0020] Figure 2The following images are provided for the XRD patterns (a) and (b) of the porous lanthanum oxycarbonate phosphorus adsorbent prepared in Example 1 before and after phosphorus adsorption: XRD pattern (a), adsorption-desorption curve (b), pore size distribution (c), infrared spectrum (d), XPS full spectrum (e), and high-resolution C, O, La, P spectra (f) of the porous lanthanum oxycarbonate phosphorus adsorbent before and after phosphorus adsorption. Detailed Implementation

[0021] This invention provides a method for preparing a porous network lanthanum oxycarbonate phosphorus adsorbent, comprising the following steps:

[0022] A lanthanide compound, an organic polymer compound, and a solvent were mixed and then frozen to obtain a solid mixture.

[0023] The solid mixture was subjected to vacuum freeze-drying and pyrolysis in sequence to obtain a porous network lanthanum oxycarbonate phosphorus adsorbent.

[0024] This invention involves mixing a lanthanide compound, an organic polymer compound, and a solvent, followed by freezing to obtain a solid mixture. In this invention, the preferred mass ratio of the lanthanide compound to the organic polymer compound is 2–5:2–5, more preferably 3–4:3.

[0025] In this invention, the lanthanide compound preferably includes one or more of lanthanum chloride, lanthanum nitrate, and lanthanum acetate.

[0026] In this invention, the organic polymeric compound preferably includes one or more of polyvinylpyrrolidone, polyethylene glycol, and polyvinyl alcohol. Preferably, the molecular weight of the polyvinylpyrrolidone is 58,000; the molecular weight of the polyethylene glycol is preferably 3,500; and the molecular weight of the polyvinyl alcohol is preferably 27,000. In this invention, the organic polymeric compound has good water solubility, readily forms a hydrated film, and its hydrophilic portion contains polarizing groups capable of partially ionizing and charging particles to prevent aggregation. Furthermore, the carbonyl oxygen can provide coordination electrons that can be adsorbed onto the surface atoms of metal particles, and its long polymer chain spatial structure can exert a steric effect.

[0027] In this invention, the solvent preferably includes one of water, ethanol, and methanol. In this invention, the water is preferably deionized water. In this invention, the ratio of the organic polymer compound to the solvent is preferably 2-5 g: 15-20 mL, more preferably 3-4 g: 15 mL.

[0028] In this invention, the mixing process preferably includes: first dissolving the organic polymer compound in a solvent and stirring for 20–40 minutes; then adding the lanthanide compound and continuing to stir for another 20–40 minutes. In this invention, the organic polymer compound and the lanthanide compound are uniformly mixed after dissolving in the solvent during the mixing process.

[0029] In this invention, the freezing temperature is preferably -18 to -25°C, more preferably -18 to -20°C; the freezing time is preferably 7 to 11 hours, more preferably 9 to 10 hours. This invention freezes the mixed solution into a solid state, facilitating subsequent vacuum freeze-drying.

[0030] After obtaining the solid mixture, the present invention sequentially subjectes the solid mixture to vacuum freeze-drying and pyrolysis to obtain a porous network lanthanum oxycarbonate phosphorus absorbent. In the present invention, the vacuum freeze-drying temperature is preferably -60 to -160°C, more preferably -70 to -80°C; the vacuum freeze-drying time is preferably 10 to 24 hours, more preferably 12 hours.

[0031] In this invention, the pyrolysis temperature is preferably 300–600°C, more preferably 400–550°C; the holding time is preferably 1.5–4 hours, more preferably 2–3 hours; and the heating rate is preferably 2–10°C / min, more preferably 3–5°C / min. In this invention, the pyrolysis is carried out in a protective atmosphere, more preferably in a nitrogen or argon atmosphere. During pyrolysis, gases such as H₂O and CO₂ escape, thereby generating a large number of porous structures.

[0032] Preferably, after pyrolysis, the sample is cooled to room temperature to obtain a porous network lanthanum oxycarbonate phosphorus absorbent.

[0033] This invention provides a porous network lanthanum oxycarbonate phosphorus absorber prepared by the method described above, comprising an organic framework carbon chain and lanthanum oxycarbonate distributed on the organic framework carbon chain. In this invention, the lanthanum oxycarbonate is grown in situ on the organic framework carbon chain. Preferably, the specific surface area of ​​the porous network lanthanum oxycarbonate phosphorus absorber is 30–150 m² / g. 2 / g; pore size preferably in the range of 2–50 nm; pore volume preferably in the range of 0.05–0.5 cm³. 3 / g.

[0034] This invention provides the application of the porous network lanthanum oxycarbonate phosphorus adsorbent described above in the removal of phosphorus from wastewater. The porous network lanthanum oxycarbonate phosphorus adsorbent provided by this invention can efficiently and rapidly adsorb phosphorus from wastewater, ultimately achieving compliant phosphorus discharge.

[0035] This invention does not impose any special requirements on the application method; any application method well-known to those skilled in the art can be used. In this invention, the phosphorus concentration in the wastewater is preferably 0.5–100 mg P / L. In this invention, the pH value of the application is preferably 3–8; the amount of the porous network lanthanum oxycarbonate phosphorus adsorbent added is preferably 0.1–1 g / L.

[0036] In a specific embodiment of the present invention, when the phosphorus concentration in the wastewater is 50 mg P / L, the pH value of the wastewater is 5.5, and the amount of porous lanthanum oxycarbonate phosphorus adsorbent added is 0.3 g / L, the adsorption capacity of the porous lanthanum oxycarbonate phosphorus adsorbent for phosphorus is 93.1 to 100 mg P / g.

[0037] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0038] Example 1

[0039] (1) Dissolve 4g of polyvinylpyrrolidone (molecular weight 58000) in 15ml of deionized water, and then stir vigorously with a magnetic force for 40 minutes.

[0040] (2) Quickly add 2g of lanthanum chloride to step (1) and stir for 30 minutes.

[0041] (3) Add the mixed solution from step (2) into a disposable PE box with a volume of 100 ml, and transfer it to the freezer. Control the temperature at -18℃ and freeze for 7 hours.

[0042] (4) After freezing is complete, quickly place the disposable PE box into the vacuum freeze dryer, control the vacuum freezing temperature to -80℃, and the vacuum freezing time to 10 hours;

[0043] (5) The material obtained by vacuum freezing in step (4) is placed in a tube furnace and heated to 400°C at a heating rate of 3°C / min. It is then calcined for 3 hours under a nitrogen atmosphere and cooled to room temperature to obtain a porous network lanthanum carbonate phosphorus adsorbent.

[0044] The porous network lanthanum oxycarbonate phosphorus adsorbent prepared in this embodiment was used to remove phosphorus from wastewater. The phosphorus concentration in the wastewater was 50 mg P / L, the pH value of the wastewater was 5.5, the amount of porous network lanthanum oxycarbonate phosphorus adsorbent added was 0.3 g / L, and the phosphorus adsorption capacity of the porous network lanthanum oxycarbonate phosphorus adsorbent prepared in this embodiment was 99.9 mg P / g.

[0045] Example 2

[0046] (1) Dissolve 3g of polyvinyl alcohol (molecular weight 27000) in 15ml of methanol solvent, and then stir vigorously with a magnetic force for 40 minutes;

[0047] (2) Quickly add 3g of lanthanum nitrate to step (1) and stir for 30 minutes.

[0048] (3) Add the mixed solution from step (2) into a disposable PE box with a volume of 100 ml, and transfer it to the freezer. Control the temperature at -25℃ and freeze for 8 hours.

[0049] (4) After freezing is complete, quickly place the disposable PE box into the vacuum freeze dryer, control the vacuum freezing temperature to -60℃, and the vacuum freezing time to 12 hours;

[0050] (5) The material obtained by vacuum freezing in step (4) is placed in a tube furnace and heated to 500°C at a heating rate of 5°C / min. It is then calcined under a nitrogen atmosphere for 2 hours and cooled to room temperature to obtain a porous network lanthanum carbonate phosphorus adsorbent.

[0051] The porous network lanthanum oxycarbonate phosphorus adsorbent prepared in this embodiment was used to remove phosphorus from wastewater. The phosphorus concentration in the wastewater was 50 mg P / L, the pH value of the wastewater was 5.5, the amount of porous network lanthanum oxycarbonate phosphorus adsorbent added was 0.3 g / L, and the phosphorus adsorption capacity of the porous network lanthanum oxycarbonate phosphorus adsorbent prepared in this embodiment was 95.7 mg P / g.

[0052] Example 3

[0053] (1) Dissolve 3g of polyethylene glycol (molecular weight 3500) in 15ml of deionized water, and then stir vigorously with a magnetic force for 40 minutes;

[0054] (2) Quickly add 2g of lanthanum acetate to step (1) and stir for 40 minutes.

[0055] (3) Add the mixed solution from step (2) into a disposable PE box with a volume of 100 ml, and transfer it to the freezer. Control the temperature at -20℃ and freeze for 9 hours.

[0056] (4) After freezing is complete, quickly place the disposable PE box into the vacuum freeze dryer, control the vacuum freezing temperature to -60℃, and the vacuum freezing time to 12 hours;

[0057] (5) The material obtained by vacuum freezing in step (4) is placed in a tube furnace and heated to 500°C at a heating rate of 10°C / min. It is then calcined under an argon atmosphere for 2 hours and cooled to room temperature to obtain a porous network lanthanum carbonate phosphorus adsorbent.

[0058] The porous network lanthanum oxycarbonate phosphorus adsorbent prepared in this embodiment was used to remove phosphorus from wastewater. The phosphorus concentration in the wastewater was 50 mg P / L, the pH value of the wastewater was 5.5, the amount of porous network lanthanum oxycarbonate phosphorus adsorbent added was 0.3 g / L, and the phosphorus adsorption capacity of the porous network lanthanum oxycarbonate phosphorus adsorbent prepared in this embodiment was 94.8 mg P / g.

[0059] Example 4

[0060] (1) Dissolve 3g of polyethylene glycol (molecular weight 3500) in 15ml of ethanol, and then stir vigorously with a magnetic force for 40 minutes;

[0061] (2) Quickly add 4g of lanthanum nitrate to step (1) and stir for 30 minutes.

[0062] (3) Add the mixed solution from step (2) into a disposable PE box with a volume of 100 ml, and transfer it to the freezer. Control the temperature at -18℃ and freeze for 7 hours.

[0063] (4) After freezing is complete, quickly place the disposable PE box into the vacuum freeze dryer, control the vacuum freezing temperature to -70℃, and the vacuum freezing time to 12 hours;

[0064] (5) The material obtained by vacuum freezing in step (4) is placed in a tube furnace and heated to 550°C at a heating rate of 5°C / min. It is then calcined under a nitrogen atmosphere for 2 hours and cooled to room temperature to obtain a porous network lanthanum carbonate phosphorus adsorbent.

[0065] The porous network lanthanum oxycarbonate phosphorus adsorbent prepared in this embodiment was used to remove phosphorus from wastewater. The phosphorus concentration in the wastewater was 50 mg P / L, the pH value of the wastewater was 5.5, the amount of porous network lanthanum oxycarbonate phosphorus adsorbent added was 0.3 g / L, and the phosphorus adsorption capacity of the porous network lanthanum oxycarbonate phosphorus adsorbent prepared in this embodiment was 93.1 mg P / g.

[0066] Comparative Example

[0067] The preparation method is basically the same as that in Example 1, except that lanthanum chloride is not added, and pyrolysis products without added La are obtained.

[0068] The pyrolysis product without added La was used to remove phosphorus from wastewater. The concentration of phosphorus in the wastewater was 50 mg P / L, the pH value of the wastewater was 5.5, the amount of pyrolysis product without added La was 0.3 g / L, and the adsorption capacity of the pyrolysis product without added La prepared in this comparative example for phosphorus was 7.3 mg P / g.

[0069] Test case

[0070] Figure 1 The morphology and mapping diagram of the porous network lanthanum oxycarbonate phosphorus adsorbent prepared in Example 1; Figure 1 a is a scanning electron microscope (SEM) image of the pyrolysis product without added La prepared in the comparative example; b is a SEM image of the porous network lanthanum oxycarbonate phosphorus adsorbent after adding La; c and d are transmission electron microscope (TEM) images of the porous network lanthanum oxycarbonate phosphorus adsorbent; e is an elemental mapping (EDS) image of the porous network lanthanum oxycarbonate phosphorus adsorbent; f is a SEM image of the phosphorus adsorbent after phosphorus adsorption; g and h are TEM images of the phosphorus adsorbent after phosphorus adsorption; and i is an elemental mapping (EDS) image of the phosphorus adsorbent after phosphorus adsorption.

[0071] Under the same preparation method, the pyrolysis products without added La exhibit dense porous characteristics. Figure 1 (a) The product after adding La still retains its loose and porous morphology, indicating that the polymer mainly provides the organic carbon skeleton structure. Figure 1 (b) Adding La did not change the morphology of the material. (Combined scanning electron microscopy images) Figure 1 (b) and transmission electron microscopy (TEM) image ( Figure 1 As can be seen from (c) and (d), the porous network lanthanum oxycarbonate phosphorus adsorbent has an internal structure consisting of layers of interconnected, loosely porous meshes. Surface elemental mapping (EDS) analysis... Figure 1 (e) It can be observed that C, O, and La elements are uniformly distributed in the network structure of the phosphorus adsorbent, indicating that La2CO5 is uniformly coated in the organic framework structure provided by the polymer. The porous network lanthanum oxycarbonate phosphorus adsorbent still exhibits a loose and porous microstructure after phosphorus adsorption. Figure 1 The f) indicates that the phosphorus adsorbent retained its original skeletal structure. However, transmission electron microscopy revealed that the phosphorus adsorbent had changed from its original layered network structure to a large number of needle-like clusters piled together. Figure 1 (g, h), this is a typical LaPO4 structure. EDS analysis ( Figure 1 (i) It can be observed that phosphorus elements are evenly distributed on the surface of the phosphorus adsorbent after adsorbing phosphorus.

[0072] Figure 2The following images are provided for the XRD patterns (a) and (b) of the porous lanthanum oxycarbonate phosphorus adsorbent prepared in Example 1 before and after phosphorus adsorption: XRD pattern (a), adsorption-desorption curve (b), pore size distribution (c), infrared spectrum (d), XPS full spectrum (e), and high-resolution C, O, La, P spectra (f) of the porous lanthanum oxycarbonate phosphorus adsorbent before and after phosphorus adsorption. Figure 2 Figure 'a' shows the XRD patterns of the phosphorus adsorbent before and after phosphorus adsorption. Before phosphorus adsorption, the diffraction peak positions of the phosphorus adsorbent match the standard XRD diffraction pattern of La2CO5 (JCPDS card number: 23-0320), indicating that the crystals detected on the surface of the prepared porous network lanthanum oxycarbonate phosphorus adsorbent are mainly La2CO5. Figure 2 Figure b shows the N2 adsorption-desorption isotherm of the porous network lanthanum oxycarbonate phosphorus adsorbent, which conforms to the IUPAC type IV curve characteristics and exhibits an H3 type hysteresis loop, indicating the presence of a mesoporous structure. This is further supported by the pore size distribution diagram (…). Figure 2 c) shows that it has both mesoporous and macroporous multi-level structures. Figure 2 d represents the FTIR characterization result, primarily used to obtain information about the functional groups contained in the sample. Located at 1500 cm⁻¹ -1 and 1367cm -1 The strong absorption band at that point corresponds to CO3. 2- The asymmetric stretching vibration peak of C=O in C is at 852 cm⁻¹. -1 CO3 appeared at the location 2- The bending vibration peak. Figure 2 The image shows the XPS spectrum of the porous lanthanum oxycarbonate phosphorus adsorbent. A P2p signal peak was detected in the phosphorus adsorbent after phosphorus adsorption, confirming that the phosphate was successfully adsorbed. Figure 2 Figures f to i show the XPS high-resolution C, O, La, and P spectra of the porous network lanthanum oxycarbonate phosphorus adsorbent before and after phosphorus adsorption. The double-split peaks at 835.5 and 852.1 eV correspond to the characteristic peaks of La3d5 / 2 and La3d3 / 2, respectively, with a spin orbital splitting energy of 16.6 eV, consistent with the positional characteristics of the La3d characteristic peak in La2CO5. After phosphorus adsorption, the La3d characteristic peak shifts towards a higher binding energy (~0.7 eV), indicating possible electron transfer and the formation of a complex containing La-OP bonds. The fitting results of the C1s signal peak indicate that it belongs to CO32-. 2- The position of the OC=O bond shifted from 289.6 eV to 288.7 eV, indicating that during adsorption, CO3... 2- The component reacted with phosphate, and ligand exchange was the main adsorption mechanism. The fitting results of the O 1s characteristic peak also verified this statement.

[0073] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a porous network lanthanum oxycarbonate phosphorus adsorbent, comprising the following steps: A lanthanide compound, an organic polymer compound, and a solvent were mixed and then frozen to obtain a solid mixture. The solid mixture was sequentially subjected to vacuum freeze-drying and pyrolysis to obtain a porous network lanthanum oxycarbonate phosphorus adsorbent. The mass ratio of the lanthanide compound to the organic polymer compound is 2~5:2~5; The vacuum freeze-drying time is 10-12 hours; The pyrolysis is carried out in a protective atmosphere; The organic polymeric compound includes one or more of polyvinylpyrrolidone, polyethylene glycol, and polyvinyl alcohol; The pyrolysis temperature is 300~600℃, and the holding time is 1.5~4 hours.

2. The production method according to claim 1, characterized by, The lanthanide compounds include one or more of lanthanum chloride, lanthanum nitrate, and lanthanum acetate.

3. The production method according to claim 1, characterized by, The solvent includes one of water, ethanol, and methanol.

4. The method of claim 1, wherein, The freezing temperature is -18 to -25°C, and the freezing time is 7 to 11 hours.

5. The preparation method according to claim 1, characterized in that, The vacuum freeze-drying temperature is -60~-160℃.

6. The porous network lanthanum oxycarbonate phosphorus absorber prepared by the preparation method according to any one of claims 1 to 5 comprises an organic framework carbon chain and lanthanum oxycarbonate distributed on the organic framework carbon chain.

7. The application of the porous mesh lanthanum oxycarbonate phosphorus adsorbent according to claim 6 in the removal of phosphorus from wastewater.

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