A rare earth neodymium-containing polyoxometalate, a preparation method and application thereof

Abstract

The application discloses a rare earth neodymium-containing polyoxometalate and a preparation method and application thereof, and relates to the technical field of water treatment. The rare earth neodymium-containing polyoxometalate K 15 Nd(GeW 10 VO 39 )2.nH2O is synthesized by taking germanium dioxide, sodium metavanadate, potassium chloride, neodymium nitrate and other reagents as raw materials. The rare earth neodymium-containing polyoxometalate prepared in the application has a remarkable degradation effect on active red X3B, and the degradation rate of the active red X3B reaches 99.94% after ultraviolet light irradiation for 40 min.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water treatment, in particular to a rare earth neodymium-containing polyoxometalate and a preparation method and application thereof. BACKGROUND

[0002] Dyes are widely used in various industries, such as pigments, leather, cosmetics, textiles, plastics and electronics, etc. However, if textile dye wastewater is directly discharged into rivers without treatment, it will cause serious pollution to water resources, seriously threatening the ecological environment and human health. Photocatalytic degradation of organic dyes has the characteristics of green environmental protection and is concerned. In industry, active red X3B, rhodamine B and the like are often used for impregnation, pad dyeing and tie dyeing of cotton, fiber, polyamide, wool and the like, and as a kind of monoazo reactive dye, it is difficult to decompose under natural conditions and difficult to remove by microorganisms. Therefore, active red X3B is a typical pollutant in printing and dyeing wastewater,

[0003] As an oxidation catalyst and acid catalyst, the process of polyoxometalate (POMs) has been industrialized, and POMs can efficiently oxidize and decompose organic pollutants, converting them into CO2, H2O, N2, SO4 2- POMs have been widely used as photocatalysts for the degradation of dye wastewater. Among various structures of POMs, keggin-type polyoxometalate is the most studied and applied, which can be used as an oxidation-reduction type, acid type or dual-function catalyst, photocatalyst for many catalytic reactions. However, as far as we know, there are few reports on the photocatalytic activity of vacancy polyoxometalates. SUMMARY

[0004] The purpose of the present application is to provide a rare earth neodymium-containing polyoxometalate and a preparation method and application thereof, which solves the following technical problems:

[0005] The existing polyoxometalate (POMs) has low photocatalytic degradation efficiency on azo dyes.

[0006] The purpose of the present application can be achieved by the following technical solutions:

[0007] A preparation method of a rare earth neodymium-containing polyoxometalate, comprising the following steps:

[0008] S1: sodium germanate solution and sodium tungstate solution are blended, and the pH is adjusted to 5-6, the temperature is controlled at 90-100℃, and the reaction is kept for 0.5-2h, then the filtrate is obtained after filtration, potassium chloride is added to the filtrate, the temperature is controlled at 40-60℃, and the reaction is kept until white precipitate appears, then the white precipitate is dried to obtain K8[GeW 11 O 39 ]·13H2O;

[0009] S2: K8[GeW 11 O 39 ]·13H2O, water, sodium metavanadate are added into a reaction kettle and blended, the pH of the solution is adjusted to 2-3, the temperature is controlled at 85-95 DEG C, and the reaction is kept for 1-3 h, and then the solution is cooled to room temperature to obtain a reaction solution, and the reaction solution is extracted with diethyl ether to obtain H5GeW 11 VO 40 ;

[0010] S3: H5GeW 11 VO 40 , distilled water, neodymium nitrate are blended, potassium acetate is added to adjust the pH to 4-5.5, the temperature is controlled at 70-90 DEG C, and the reaction is kept for 1-3 h, and then the solution is cooled to room temperature and dried to obtain a polyoxometalate containing rare earth neodymium.

[0011] As a further scheme of the present application: 4-6 mol / L hydrochloric acid aqueous solution is added in S1 to adjust the pH to 5-6.

[0012] As a further scheme of the present application: 4-6 mol / L hydrochloric acid aqueous solution is added in S2 to adjust the pH to 2-3.

[0013] As a further scheme of the present application: the configuration method of the sodium germanate solution is that germanium dioxide and sodium hydroxide aqueous solution are blended to obtain the sodium germanate solution; the sodium hydroxide aqueous solution is 3.8-4.2 mol / L sodium hydroxide aqueous solution; the mass ratio of germanium dioxide in the sodium germanate solution is 15-20%.

[0014] The configuration method of the sodium tungstate solution is that 69 g of sodium tungstate and 90 mL of water are blended, and 4-6 mol / L hydrochloric acid aqueous solution is added dropwise to adjust the pH of the sodium tungstate solution to 6-6.5 to obtain the sodium tungstate solution.

[0015] The mass ratio of the sodium germanate and the sodium tungstate in S1 is 1:19.42-21.36.

[0016] As a further scheme of the present application: 4-6 mol / L hydrochloric acid aqueous solution is used to adjust the pH of the sodium tungstate solution to 6-6.5 in the configuration method of the sodium tungstate solution.

[0017] As a further scheme of the present application: the mass ratio of potassium chloride and the sodium germanate in S1 is 3.59:1.

[0018] As a further scheme of the present application: the adding ratio of K8[GeW 11 O 39 ]·13H2O, water, sodium metavanadate in S2 is 22 g:60 mL:1-1.2 g.

[0019] As a further scheme of the present application: the distilled water in S3 is 60-80 DEG C distilled water; the H5GeW 11VO 40 , distilled water, the addition ratio of neodymium nitrate is 1.4-1.5g:10mL:0.1g.

[0020] As a further scheme of the application: the specific steps of ether extraction are: the reaction liquid is added into a separatory funnel, ether is added, and 10mL / L sulfuric acid aqueous solution is added dropwise until no oil is produced, the oil is dried to obtain H5GeW 11 VO 40 .

[0021] As a further scheme of the application: the specific steps of drying treatment are: the light yellow oil is heated in a water bath to remove ether, and then dried to obtain H5GeW 11 VO 40 .

[0022] A rare earth neodymium-containing polyoxometalate prepared by any one of the preparation methods.

[0023] The rare earth neodymium-containing polyoxometalate as described above is applied in the field of water treatment.

[0024] The beneficial effects of the application are:

[0025] The application adopts ion exchange method to prepare a Keggin type of rare earth neodymium-containing lacunary polyoxometalate K 15 Nd(GeW 10 VO 39 )2·nH2O (referred to as NdGeW 10 VO); the lacunary 11 tungsten can be degraded to form 1:1 structure and 1:2 structure by complexing with transition metal or rare earth ions. The lacunary heteropoly anion can form a mixed heteropoly complex with rare earth ions through 4-8 dentate ligands. Due to the outer electron configuration of rare earth elements, the 4f electrons are multi-layered and easily affected by external conditions to produce migration, which can form a multi-electron group state, react rare earth elements with heteropoly acids to generate cluster structure polyoxometalates, change the surface properties of heteropoly acids, thereby improving the optical, catalytic, electrical and other properties, and improving the redox properties of heteropoly acids, and ultimately improving the photocatalytic effect.

[0026] The rare earth neodymium-containing polyoxometalate prepared in the application can effectively degrade 99.94% of reactive red X3B under ultraviolet light irradiation for 40min. The doping of rare earth neodymium in the polyoxometalate can significantly improve the photocatalytic activity of the heteropoly acid. The rare earth neodymium-containing polyoxometalate prepared in the application has important applications in the fields of analysis, functional materials, pharmaceuticals, etc. BRIEF DESCRIPTION OF DRAWINGS

[0027] The application will be further described below with reference to the drawings.

[0028] Figure 1 NdGeW is prepared in Embodiment 1 of the present application 10 The absorbance change curve of the reaction solution in the catalytic degradation process of VO on X3B reaction solution with pH = 0.5;

[0029] Figure 2 NdGeW is prepared in Embodiment 1 of the present application 10 The color change graph of VO at 0 min, 20 min and 40 min in the catalytic degradation process of VO on X3B reaction solution with pH = 0.5;

[0030] Figure 3 H5GeW is prepared in Comparative Example 1 of the present application 11 VO 40 The absorbance change curve of the reaction solution in the catalytic degradation process of VO on X3B reaction solution with pH = 0.5;

[0031] Figure 4 NdGeW is prepared in Embodiment 1 of the present application 10 VO and H5GeW is prepared in Comparative Example 1 of the present application 11 VO 40 The decolorization rate detection data statistical line graph of VO and H5GeW is prepared in Comparative Example 1 of the present application

[0032] Figure 5 NdGeW is prepared in Embodiment 1 of the present application 10 VO and H5GeW is prepared in Comparative Example 1 of the present application 11 VO 40 The infrared spectrum of VO and H5GeW is prepared in Comparative Example 1 of the present application

[0033] Figure 6 NdGeW is prepared in Embodiment 1 of the present application 10 VO and H5GeW is prepared in Comparative Example 1 of the present application 11 VO 40 The XRD graph of VO and H5GeW is prepared in Comparative Example 1 of the present application

[0034] Figure 7 NdGeW is prepared in Embodiment 1 of the present application 10 The TG-DSC curve of VO is prepared in Embodiment 1 of the present application

[0035] Figure 8 The chemical reaction equation of K8[GeW is prepared in the present application 11 O 39 ]·13H2O

[0036] Figure 9 The chemical reaction equation of H5GeW is prepared in the present application 11 VO 40 ​

[0037] Figure 10 is prepared according to the present application 15 Nd(GeW 10 VO 39 )2·nH2O. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0039] The preparation method of the polyoxometalate containing rare earth neodymium in the embodiment 1 comprises the following steps:

[0040] S1: please refer to Figure 1 82.9g of 4mol sodium hydroxide aqueous solution is mixed with 17.1g of germanic acid to obtain a sodium germanate solution;

[0041] 69g of sodium tungstate is dissolved in 90mL of 70℃ water, 6mol / L hydrochloric acid aqueous solution is added dropwise to adjust the pH value of the sodium tungstate solution to 6.5 to obtain a sodium tungstate solution;

[0042] The sodium germanate solution containing 10g of sodium germanate is added into the sodium tungstate solution containing 205g of sodium tungstate, 6mol / L hydrochloric acid aqueous solution is added to adjust the pH value to 5.5, the temperature is controlled at 95℃, and water bath heating is performed for 1h, then cooling and filtration are performed to obtain a filtrate. 35.9g of potassium chloride is added into the filtrate and magnetically stirred until dissolved, the temperature is controlled at 50℃, and water bath heating is performed until white precipitate appears, the precipitate is taken out and dried in a 50℃ oven to obtain K8[GeW 11 O 39 ]·13H2O.

[0043] S2: please refer to Figure 2 22g of K8[GeW 11 O 39]·13H2O, 60 mL water was mixed, 1.08 g sodium metavanadate was added, 6 mol / L hydrochloric acid aqueous solution was added to adjust the pH value of the solution to 2.5, the temperature was controlled at 90℃, water bath heating was carried out for 1.5 h, and then the solution was cooled to room temperature. Ethyl ether was added for extraction. During the extraction process, 0.01 vt% sulfuric acid aqueous solution was added dropwise into the separatory funnel. Yellow oil appeared and precipitated. A glass rod was inserted into the separatory funnel to stir properly to make it precipitate completely. Until no oil appeared when 0.01 vt% sulfuric acid aqueous solution was added dropwise, the yellow oil was collected and heated at 50℃ water bath to remove the remaining ethyl ether. The solution was evaporated to dryness and then transferred to a 50℃ oven for drying. Yellow solid H5GeW 11 VO 40 was obtained.

[0044] S3: Please refer to Figure 3 , 1.4 g H5GeW 11 VO 40 was dissolved in 10 mL 70℃ distilled water, 0.1 g neodymium nitrate was added, and the pH value was adjusted to 4-5.5 with potassium acetate. The temperature was controlled at 80℃, water bath heating was carried out for 2 h, and then the solution was cooled to room temperature. Yellow solid K 15 Nd(GeW 10 VO 39 )2·nH2O (abbreviated as NdGeW 10 VO) was obtained, that is, a polyoxometalate containing rare earth neodymium.

[0045] The preparation method of the polyoxometalate containing rare earth neodymium of Example 2 comprises the following steps:

[0046] S1: Please refer to Figure 1 , 82.9 g 3.8 mol sodium hydroxide aqueous solution was mixed with 17.1 g germanium dioxide to obtain a sodium germanate solution;

[0047] 69 g sodium tungstate was dissolved in 90 mL 70℃ water, and 6 mol / L hydrochloric acid aqueous solution was added dropwise to adjust the pH value of the sodium tungstate solution to 6.5 to obtain a sodium tungstate solution;

[0048] The sodium tungstate solution containing 194.2 g sodium tungstate was added to the sodium germanate solution containing 10 g sodium germanate, 6 mol / L hydrochloric acid aqueous solution was added to adjust the pH value to 5, the temperature was controlled at 95℃, water bath heating was carried out for 1 h, and then the solution was cooled and filtered to obtain a filtrate. 35.9 g potassium chloride was added to the filtrate and stirred magnetically until dissolved. The temperature was controlled at 50℃, water bath heating was carried out until white precipitate appeared, and then the precipitate was placed in a 50℃ oven for drying to obtain K8[GeW 11 O 39 ]·13H2O;

[0049] S2: Please refer to Figure 2 , 22 g K8[GeW11 O 39 ]·13H2O, 60 mL water was blended, 1 g sodium metavanadate was added, 6 mol / L hydrochloric acid aqueous solution was added to adjust the pH value of the solution to 2, the temperature was controlled at 85℃, water bath heating was performed for 1 h, cooling was performed to room temperature, extraction was performed by adding ether, 0.01 vt% sulfuric acid aqueous solution was added dropwise to the separatory funnel during the extraction process, yellow oil appeared and precipitated, a glass rod was inserted into the separatory funnel to stir appropriately to make it precipitate completely; until 0.01 vt% sulfuric acid aqueous solution was no longer added dropwise, the yellow oil was collected, heating was performed at 50℃ to remove the residual ether, the solution was dried by evaporation, and then was transferred to a 50℃ oven to dry, to obtain yellow solid H5GeW 11 VO 40 ;

[0050] S3: please refer to Figure 3 , 1.4 g H5GeW 11 VO 40 , 10 mL 70℃ distilled water was mixed and dissolved, 0.1 g neodymium nitrate was added, potassium acetate was used to adjust the pH value to 4, the temperature was controlled at 70℃, water bath heating was performed for 1 h, cooling was performed to room temperature, and yellow solid K 15 Nd(GeW 10 VO 39 )2·nH2O (abbreviated as NdGeW 10 VO) was obtained, that is, a polyoxometalate containing rare earth neodymium.

[0051] The preparation method of the polyoxometalate containing rare earth neodymium in Example 3 comprises the following steps:

[0052] S1: please refer to Figure 1 , 82.9 g of 4.2 mol sodium hydroxide aqueous solution was blended with 17.1 g of germanium dioxide to obtain a sodium germanate solution;

[0053] 69 g of sodium tungstate was dissolved in 90 mL of 70℃ water, 6 mol / L hydrochloric acid aqueous solution was added dropwise to adjust the pH value of the sodium tungstate solution to 6.5 to obtain a sodium tungstate solution;

[0054] The sodium germanate solution containing 10 g of sodium germanate was added to the sodium tungstate solution containing 213.6 g of sodium tungstate, 6 mol / L hydrochloric acid aqueous solution was added to adjust the pH value to 5.5, the temperature was controlled at 95℃, water bath heating was performed for 1 h, cooling and filtration were performed, and a filtrate was obtained. 35.9 g of potassium chloride was added to the filtrate and magnetically stirred until dissolved, the temperature was controlled at 50℃, water bath heating was performed until white precipitate appeared, the precipitate was taken out and dried in a 50℃ oven to obtain K8[GeW 11 O 39 ]·13H2O;

[0055] S2: please refer to Figure 222g K8[GeW 11 O 39 Mix 13H₂O and 60mL of water, add 1.2g of sodium metavanadate, and adjust the pH of the solution to 3 with 6mol / L hydrochloric acid aqueous solution. Heat in a water bath at 95℃ for 3 hours, then cool to room temperature. Extract with diethyl ether. During extraction, add 0.01vt% sulfuric acid aqueous solution dropwise to the separatory funnel. A yellow oily substance forms and precipitates. Stir appropriately with a glass rod in the separatory funnel to completely precipitate the precipitate. Continue until no more oily substance is produced when adding 0.01vt% sulfuric acid aqueous solution. Collect the pale yellow oily substance and remove the remaining diethyl ether by heating in a 50℃ water bath. Evaporate the solution to dryness and then transfer it to a 50℃ oven to dry, obtaining a yellow solid H₅GeW. 11 VO 40 ;

[0056] S3: Please refer to Figure 3 At room temperature, 1.5g of H5GeW 11 VO 40 Dissolve 10 mL of neodymium nitrate in 70 °C distilled water, add 0.1 g of neodymium nitrate, adjust the pH to 5.5 with potassium acetate, heat in a water bath at 90 °C for 3 hours, and cool to room temperature to obtain a yellow solid K. 15 Nd(GeW 10 VO 39 )2·nH2O (abbreviated as NdGeW) 10 VO), which is a polyoxometalate containing rare earth neodymium.

[0057] Comparative Example 1: The preparation method of the polyoxometalate includes the following steps:

[0058] S1: 82.9 g of 4 mol sodium hydroxide aqueous solution was mixed with 17.1 g of germanium dioxide to obtain sodium germanate solution;

[0059] Dissolve 69g of sodium tungstate in 90mL of water at 70℃, and adjust the pH of the sodium tungstate solution to 6.5 by adding 6mol / L hydrochloric acid aqueous solution dropwise to obtain a sodium tungstate solution.

[0060] A sodium germanate solution containing 10g of sodium germanate was added to a sodium tungstate solution containing 205g of sodium tungstate. The pH was adjusted to 5.5 with 6mol / L hydrochloric acid. The mixture was heated in a water bath at 95℃ for 1 hour, then cooled and filtered to obtain the filtrate. 35.9g of potassium chloride was added to the filtrate and stirred magnetically until dissolved. The mixture was then heated in a water bath at 50℃ until a white precipitate appeared. The precipitate was dried in a 50℃ oven to obtain K8[GeW] 11 O 39 ·13H2O;

[0061] S2: Please refer to Figure 222g K8[GeW 11 O 39 Mix 13H₂O and 60mL of water, add 1.08g of sodium metavanadate, and adjust the pH of the solution to 2.5 with 6mol / L hydrochloric acid aqueous solution. Heat in a water bath at 90℃ for 1.5h, cool to room temperature, and extract with diethyl ether. During extraction, add 0.01vt% sulfuric acid aqueous solution dropwise to the separatory funnel. A yellow oily substance forms and precipitates. Stir appropriately with a glass rod in the separatory funnel to completely precipitate the precipitate. Continue until no more oily substance is produced when adding 0.01vt% sulfuric acid aqueous solution. Collect the pale yellow oily substance and remove the remaining diethyl ether by heating in a 50℃ water bath. Evaporate the solution to dryness and transfer to a 50℃ oven to dry, obtaining a yellow solid H₅GeW. 11 VO 40 That is, polyoxometalates.

[0062] Performance testing

[0063] (1) Decolorization rate detection

[0064] ① Prepare the reaction solution: Take 100 mL of 2 mg / L Reactive Red X3B solution, adjust the pH of the reaction solution to 0.5 with 1 mol / L hydrochloric acid aqueous solution, and stir evenly for 5 min in a dark place on a constant temperature magnetic stirrer.

[0065] ②Detection steps: Using an ultraviolet lamp as the light source, the test solution under different levels of illumination is taken every 10 minutes, and its absorbance is measured using a double-beam ultraviolet spectrophotometer.

[0066] ③ Set up a blank control group: Take 100 mL of 2 mg / L Reactive Red X3B solution, adjust the pH of the reaction solution to 0.5 with 1 mol / L hydrochloric acid aqueous solution, place it at a constant temperature under UV irradiation, and make it uniformly exposed to light radiation by electromagnetic stirring. Measure the absorbance of the Reactive Red X3B solution at 540 nm, and calculate the decolorization rate based on the change in absorbance value of the sample before and after the reaction.

[0067] ④ Calculate the decolorization rate: The maximum absorption wavelength of Reactive Red X3B is 540 nm. The absorbance of the extracted sample was measured at this wavelength using a UV-Vis spectrophotometer; and the decolorization rate (DC) was calculated according to the following formula:

[0068] DC = [(A0-A) / A0] × 100%

[0069] In the formula: A0 - absorbance of the solution at λ=540nm before illumination; A - absorbance after illumination for a period of time. A 500W medium-pressure mercury lamp was used as the light source. Samples were taken for analysis after illumination for a certain period, and the absorbance data at the maximum wavelength was recorded. The recorded data were processed using Oringinpro-8.0. The detection results are shown in Table 1.

[0070] Table 1: Statistical Table of Decolorization Rate Detection Data

[0071]

[0072] As shown in Table 1 and Figures 1-2 As shown, the rare earth neodymium-containing polyoxometalates (NdGeW) prepared in Examples 1-3 of this application 10 VO) degrades Reactive Red X3B in the reaction solution. As the light exposure time increases, the absorbance becomes flatter and flatter. When the reaction time is 40 min, the decolorization rate is above 99%.

[0073] As shown in Table 1 and Figure 3 As shown, the H5GeW prepared in Comparative Example 1 of this application 11 VO 40 The degradation of Reactive Red X3B in the reaction solution showed that the absorbance became increasingly flat as the light exposure time increased. The decolorization rate was 71.63% after 40 min of reaction and 90.30% after 60 min of reaction.

[0074] Please see Figure 4 Under the same reaction conditions, the rare earth neodymium-containing polyoxometalate (NdGeW) prepared in Example 1 of this application... 10 VO) compared to H5GeW prepared in Comparative Example 1 11 VO 40 It has better photocatalytic activity.

[0075] The rare earth neodymium-containing polyoxometalate (NdGeW) prepared in this application 10 The presence of rare earth elements (REEs) in heteropolyacids (HMA) enhances their photocatalytic activity. These elements possess unique electronic structures and strong coordination abilities, exhibiting excellent oxyphilicity and ligand field stabilization, making them highly suitable for reacting with heteropolyacids to form structurally altered polyoxometalates. Furthermore, due to their multi-layered electron configuration, rare earth elements possess 4f electrons that are easily influenced by external conditions, allowing for multi-electron configurations. This enables the reaction of rare earth elements with heteropolyacids to generate substituted saturated, sandwich, and clustered polyoxometalates, altering the surface properties of the heteropolyacids and improving their optical, catalytic, and electrochemical properties. It also enhances the redox properties, thermal stability, catalytic activity, and selectivity of the heteropolyacids. The polyoxometalates formed by the complexation of heteropolyacids with rare earth neodymium ions further enhance the redox effect, ultimately improving the catalytic performance. Therefore, the introduction of rare earth elements in this application further improves the photocatalytic activity of heteropolyacids.

[0076] (2) NdGeW prepared in the example 10 VO, H5GeW prepared in Comparative Example 1 11 VO 40 Compare infrared spectra

[0077] Please seeFigure 5 H5GeW prepared in Comparative Example 1 11 VO 40 There are four peaks in the low wave number region, which are consistent with the four characteristic peaks of Keggin-type structure heteropoly acid: 1033.6 cm -1 W-O d vibration produces a characteristic peak, 948.8 cm -1 W-O b vibration produces a characteristic peak, 850.4 cm -1 Ge-O a vibration produces a characteristic peak, 800.3 cm -1 W-O c vibration produces a characteristic peak.

[0078] NdGeW prepared in the example 10 VO and H5GeW prepared in Comparative Example 1 11 VO 40 Compared with it, the infrared spectrum is generally similar, which shows that the structure of the heteropoly anion does not change because of the addition of rare earth neodymium ion, that is, the neodymium ion does not enter the inner boundary of the heteropoly anion. Therefore, the synthesized rare earth neodymium-containing heteropoly acid salt still maintains the Keggin-type structure. However, after the coordination of the rare earth ion with the heteropoly anion, the bond force constant decreases, the bond distance becomes larger, so that the W-O d intensity decreases, the frequency red shifts, and the characteristic peak moves to the low wave number region. From the comparison of the infrared spectra, it can be seen that the coordination of the neodymium ion is successful.

[0079] (3) XRD comparison of NdGeW 10 VO prepared in the example, H5GeW 11 VO prepared in Comparative Example 1 40

[0080] X-ray powder diffraction (XRD) is mainly used to study the arrangement of atoms in crystals. Through X-ray diffraction, the structure of the substance is understood, and the macroscopic properties of polyoxometalate are explained. In the present application, the XRD of NdGeW 10 VO prepared in the example, H5GeW 11 VO prepared in Comparative Example 1 40 was determined in the range of 10°≤2θ≤80° to determine its structural properties and grain size.

[0081] Please refer to Figure 6 In the range of 10°≤2θ≤40°, both compounds have strong diffraction peaks. From NdGeW 10 VO and H5GeW 11 VO 40 ​As can be seen from the comparison of the diffraction peaks of the two samples, the diffraction peak intensity changes and the strongest diffraction peak shifts. The spatial volume of the neodymium ion is larger than that of the hydrogen ion, which causes the expansion of the whole Keggin structure unit, indicating that the neodymium ion is successfully complexed with the heteropoly acid anion.

[0082] (4) Thermogravimetric analysis

[0083] The NdGeW 10 VO prepared in the application has a structure unit composed of two [GeW 10 VO 39 ] 9- anions, one Nd 3+ , 15 K + and 55 water molecules, i.e. K 15 Nd(GeW 10 VO 39 )2·55H2O. The [GeW 10 VO 39 ] 9- anion has Ge as a heteroatom and V and W as coordination atoms, which are combined with O atoms to form an unsaturated Keggin structure, and Nd 3+ is located in the middle of two vacancy polyoxometalate anions [GeW 10 VO 39 ] 9- , forming a sandwich structure with the double-Keggin type vacancy polyoxometalate combined with O atoms and Nd 3+ . The rare earth Nd 3+ ion is connected with eight O atoms through a tetrahedral antiprism coordination mode, and each vacancy anion [GeW 10 VO 39 ] 9- provides 4 oxygen atoms.

[0084] Please refer to Figure 7 , the NdGeW 10 VO prepared in Example 1 includes combined water and crystal water below 600℃. These waters are mainly degraded in the following two steps: first, 15 molecules of combined water are lost below 133.7℃; second, 40 molecules of crystal water are lost between 133.7℃ and 364.6℃.

[0085] The above has described one embodiment of the application in detail, but the description is only a preferred embodiment of the application and cannot be considered as limiting the scope of the application. Any equivalent changes and improvements made within the scope of the application should still be attributed to the patent coverage of the application.

Claims

1. A process for the preparation of a polyoxometalate containing neodymium, characterized in that, Comprising the following steps: S1: sodium germanate solution, sodium tungstate solution are blended, and pH is adjusted to 5-6, temperature is controlled to 90-100 DEG C, incubation reaction is carried out for 0.5-2 h, after filtration, the filtrate is taken, potassium chloride is added to the filtrate, temperature is controlled to 40-60 DEG C, incubation reaction is carried out until white precipitate appears, the white precipitate is taken and dried, to obtain K8[GeW 11 O 39 ]·13H2O; S2: K8[GeW 11 O 39 ]·13H2O, water, sodium metavanadate are added into a reaction kettle and blended, the pH of the solution is adjusted to 2-3, the temperature is controlled at 85-95°C, the reaction is kept for 1-3h, and the reaction solution is obtained after cooling to room temperature; the reaction solution is extracted with diethyl ether to obtain H5GeW 11 VO 40 ​ S3: H5GeW 11 VO 40 , distilled water, neodymium nitrate are blended, potassium acetate is added to adjust the pH to 4-5.5, the temperature is controlled at 70-90 DEG C, and the temperature is maintained for 1-3 h, and then the temperature is cooled to room temperature and dried to obtain a multi-metal oxyacid salt containing rare earth neodymium. The preparation method of the sodium tungstate solution is as follows: 69 g of sodium tungstate and 90 mL of water are mixed, and the pH value of the sodium tungstate solution is adjusted to 6-6.5 by dropwise addition to obtain the sodium tungstate solution. The mass ratio of the sodium germanate and the sodium tungstate in S1 is 1:19.42-21.

36. The mass ratio of the potassium chloride and the sodium germanate in S1 is 3.59:

1.

2. The method for preparing a polyoxometalate containing rare earth neodymium according to claim 1, characterized in that, Made by the preparation method in any one of claims 1-6.

3. The method for preparing a polyoxometalate containing rare earth neodymium according to claim 1, characterized in that, K8[GeW 11 O 39 ]·13H2O, water, sodium metavanadate in the ratio of 22 g: 60 mL: 1-1.2 g.

4. The method for preparing a polyoxometalate containing rare earth neodymium according to claim 1, characterized in that, S3 distilled water is 60-80℃ distilled water; H5GeW 11 VO 40 , distilled water, the addition ratio of neodymium nitrate is 1.4-1.5g: 10mL: 0.1g.

5. The method for preparing a polyoxometalate containing rare earth neodymium according to claim 1, characterized in that, The specific procedure for ether extraction is as follows: the reaction solution is added to a separatory funnel, ether is added, and 0.01 vt% aqueous sulfuric acid is added dropwise until no more oil is produced, and the oil is dried to obtain H5GeW 11 VO 40 .

6. The method for preparing a polyoxometalate containing neodymium according to claim 5, characterized in that, The specific steps of the drying treatment are: the yellowish oil is heated in a water bath to remove the diethyl ether, and then dried in an oven to obtain H5GeW 11 VO 40 .

7. A polyoxometalate containing neodymium, characterized in that, 8. The rare earth neodymium-containing polyoxometalate of claim 7 is applied in the field of water treatment. ​

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