A long-chain alkyl surfactant-mediated lanthanum hydroxide material, its preparation method and application

Abstract

This invention relates to a long-chain alkyl surfactant-mediated lanthanum hydroxide material, its preparation method, and its applications. The lanthanum hydroxide material is synthesized by alkaline co-thermal precipitation of a soluble lanthanum salt and alkyltrimethylammonium bromide in a pressure-resistant reactor under closed conditions. This yields a long-chain alkyl surfactant-mediated lanthanum hydroxide material with optimal adsorption performance, suitable for removing phosphorus nutrients from low-concentration phosphorus wastewater. Compared with existing technologies, the long-chain alkyl surfactant-mediated lanthanum hydroxide material provided by this invention not only possesses good dispersibility but also exhibits higher phosphorus adsorption capacity and rate through the regulation of its physicochemical properties. Compared with lanthanum hydroxide prepared by conventional hydrothermal precipitation methods, its phosphorus separation performance is significantly higher.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection and resource recycling technology, specifically relating to a long-chain alkyl surfactant-mediated lanthanum hydroxide material, its preparation method, and its application. Background Technology

[0002] With increasing human exploitation of environmental resources, continuous urbanization and industrialization, and the extensive use of agricultural fertilizers and phosphorus-containing detergents, the amount of nitrogen and phosphorus nutrients entering lakes, reservoirs, and rivers is constantly increasing, leading to massive algal blooms and widespread eutrophication. Eutrophication not only severely damages the aquatic ecosystem, reduces the usability of water bodies, and accelerates their decline, but also affects navigation and hinders economic development. Faced with the current dilemma of excessive phosphorus emissions and phosphorus resource shortages, effectively controlling excessive phosphorus nutrients in water bodies and recovering phosphorus resources is an urgent need. Traditional phosphorus treatment technologies generally employ traditional adsorbents and natural minerals for phosphorus removal, as well as commonly used iron and aluminum salt precipitation methods. These methods are effective for high-concentration wastewater, but under low-concentration phosphorus conditions, the required amount of iron or aluminum salts increases dramatically.

[0003] For the separation or removal of low-concentration phosphorus, adsorption methods are widely used due to their simple operation, high removal efficiency, and low sludge production. However, general adsorbents are physical adsorption agents, which have low adsorption efficiency and long adsorption times, making it difficult to achieve selective phosphorus separation and ultra-low phosphorus emission treatment requirements. For example, patent application CN202310366119.X discloses a lanthanum magnetic iron modified attapulgite adsorbent and its phosphorus removal application. This lanthanum magnetic iron modified attapulgite phosphorus removal adsorbent includes attapulgite, on which lanthanum and γ-Fe2O3 are loaded. The lanthanum magnetic iron modified attapulgite phosphorus removal adsorbent has a large specific surface area and many adsorption active sites, and has a good phosphorus removal effect on low-concentration phosphorus (≤2mg / L). However, the synthesis conditions of this patent require high-temperature calcination, resulting in relatively high costs.

[0004] The synthesis or preparation method of lanthanum metal-based materials has a significant impact on their morphology, which in turn affects their adsorption or separation functions. Therefore, selecting appropriate methods and rationally controlling the morphology, structure, and physicochemical properties of metal-based materials are key to obtaining high-performance materials. Summary of the Invention

[0005] The purpose of this invention is to overcome the deficiencies of the prior art by providing a long-chain alkyl surfactant-mediated lanthanum hydroxide material, its preparation method, and its application, thereby overcoming the shortcomings of the prior art.

[0006] The objective of this invention can be achieved through the following technical solution: a method for preparing lanthanum hydroxide material mediated by a long-chain alkyl surfactant, which is synthesized by alkaline co-heat precipitation of soluble lanthanum salt and alkyltrimethylammonium bromide in a pressure-resistant reactor under closed conditions.

[0007] Furthermore, the alkyl group in the alkyltrimethylammonium bromide is dodecyl to octadecyl, and is calculated as C0. x TAB, where x is the carbon chain length, x = 12, 14, 16 and 18.

[0008] Furthermore, the soluble lanthanum salt includes lanthanum nitrate, lanthanum chloride, or lanthanum sulfate, etc.

[0009] Furthermore, the molar ratio of the soluble lanthanum salt to alkyltrimethylammonium bromide is 5 to 20:1.

[0010] Furthermore, the method specifically includes the following steps:

[0011] (1) Dissolve soluble lanthanum salt and alkyltrimethylammonium bromide in deionized water; shake and adjust pH to 9-11, and a white flocculent precipitate appears in the reactor;

[0012] (2) Transfer the mixed suspension obtained in step (1) to a pressure-resistant reactor and react it at 60-100℃ and 110-160℃ respectively under closed conditions for 6-12 hours. After cooling, take it out.

[0013] (3) Centrifuge the solid-liquid mixture obtained in step (2) to remove the supernatant. The resulting precipitate is washed and dried to obtain a highly dispersed surfactant-mediated lanthanum hydroxide material.

[0014] Furthermore, in step (1), the oscillation is performed at a shaking speed of 200-400 rpm for 3-6 hours.

[0015] Furthermore, in step (3), the centrifugation is performed at 7000-9000 rpm for 10-30 min.

[0016] Furthermore, in step (3), the washing is performed by washing with deionized water and ethanol multiple times, and the drying is performed by heating in a forced-air drying oven at 100-150°C for 10-14 hours.

[0017] The present invention also provides a long-chain alkyl surfactant-mediated lanthanum hydroxide material prepared by the above method.

[0018] The present invention also provides the application of the above-mentioned surfactant-mediated lanthanum hydroxide material, which is used for the separation, removal or enrichment of phosphates in water, especially for low concentrations of phosphates (below 2 mg / L).

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The lanthanum hydroxide material synthesized by surfactant-mediated synthesis provided by the present invention has special morphological characteristics such as larger specific surface area and richer pore structure compared with lanthanum hydroxide prepared by general hydrothermal precipitation method, which makes it have higher phosphorus adsorption capacity and phosphorus adsorption rate.

[0021] (2) The long-chain alkyl surfactant selected in this invention is long-chain alkyltrimethylammonium bromide. During the hydrothermal crystallization process, the alkyl chain of the surfactant can be adsorbed on the crystal and induce the formation of a low-dimensional morphological structure. As the carbon chain length increases, the steric hindrance inside also increases, which greatly affects the close arrangement of the crystal and forms a highly dispersed structure. The product has abundant active sites. Therefore, the lanthanum hydroxide provided by this invention has superior phosphorus adsorption performance. Attached Figure Description

[0022] Figure 1 The images are SEM images of the phosphorus adsorbents Sur-Cx La(OH)3 and comparative La(OH)3 prepared in Examples 1-4 of this invention; where a is La(OH)3, b is Sur-C12 La(OH)3, c is Sur-C14 La(OH)3, d is Sur-C16 La(OH)3, and e is Sur-C18 La(OH)3.

[0023] Figure 2 The X-ray powder diffraction patterns of the phosphorus adsorbents Sur-Cx La(OH)3 and comparative La(OH)3 prepared in Examples 1-4 of this invention are shown below.

[0024] Figure 3 This is a nitrogen adsorption-desorption curve of the phosphorus adsorbent Sur-C18-La(OH)3 prepared in Example 4 of the present invention;

[0025] Figure 4 This is a pore size distribution diagram of the phosphorus adsorbent Sur-C18-La(OH)3 prepared in Example 4 of the present invention;

[0026] Figure 5 The adsorption kinetics and fitting diagrams of the phosphorus adsorbents Sur-Cx La(OH)3 and comparative example La(OH)3 prepared in Examples 1-4 of this invention are shown.

[0027] Figure 6 The adsorption isotherms and fitting diagrams of the phosphorus adsorbents Sur-Cx La(OH)3 and comparative example La(OH)3 prepared in Examples 1-4 of this invention are shown.

[0028] Figure 7This is an experimental diagram showing the anion coexistence and competition between the phosphorus adsorbent Sur-C18-La(OH)3 prepared in Example 4 of this invention and the comparative example La(OH)3. Detailed Implementation

[0029] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. Finally, it should be noted that the following embodiments are only used to illustrate the technical solution of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solution of the invention without departing from the spirit and scope of the technical solution of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention.

[0030] All raw materials used in this application are of reagent grade or analytical grade, or commercially available industrial grade products may be used.

[0031] The following will provide a detailed explanation through specific examples:

[0032] Example 1

[0033] Preparation of phosphorus adsorbent Sur-C12-La(OH)3:

[0034] Weigh 2.165 g of lanthanum nitrate hexahydrate (La(NO3)3·6H2O) and 0.15 g of dodecyl ammonium bromide (molar ratio 10:1), and dissolve them in 100 mL of deionized water. Adjust the pH to 10 under shaking at 300 rpm for 4 h, and a white flocculent precipitate will appear in the beaker. Transfer the above mixed suspension to a 150 mL pressure-resistant reactor, and control the temperature of the drying oven at 90℃ and 120℃ for 6 h each under sealed conditions. After cooling, remove the mixture. Centrifuge the solid-liquid mixture at 8000 rpm for 20 min, and discard the supernatant. Wash the precipitate obtained above three times with deionized water and ethanol, and heat it in a drying oven at 120℃ for 12 h to obtain highly dispersed Sur-C12-La(OH)3.

[0035] Example 2

[0036] Preparation of phosphorus adsorbent Sur-C14-La(OH)3

[0037] Replace 0.15g dodecyltrimethylammonium bromide in Example 1 with 0.16g tetradecyltrimethylammonium bromide (molar ratio 10:1), and the rest is the same as in Example 1.

[0038] Example 3

[0039] Preparation of phosphorus adsorbent Sur-C16-La(OH)3

[0040] Replace 0.15g dodecyltrimethylammonium bromide in Example 1 with 0.18g hexadecyltrimethylammonium bromide (molar ratio 10:1), and the rest is the same as in Example 1.

[0041] Example 4

[0042] Preparation of phosphorus adsorbent Sur-C18-La(OH)3

[0043] Replace 0.15g dodecyltrimethylammonium bromide with 0.2g octadecyltrimethylammonium bromide (molar ratio 10:1), and the rest is the same as in Example 1.

[0044] Comparative Example

[0045] Preparation of phosphorus adsorbent La(OH)3:

[0046] The same as in Example 1 was used, but without the addition of alkyltrimethylammonium bromide.

[0047] Figure 1 The images show SEM (Scanning Electron Microscopy) images of the phosphorus adsorbents Sur-Cx La(OH)3 and La(OH)3 prepared in Examples 1-4 of this invention. As can be seen from the images, La(OH)3 has a spherical structure, while the Sur-Cx-La(OH)3 material has a rod-like structure, and the structure gradually becomes finer as the chain length of the long-chain alkyl group increases. The length of all samples is between 100-200 nm.

[0048] Figure 2 The X-ray powder diffraction patterns of the phosphorus adsorbents Sur-Cx La(OH)3 and the comparative La(OH)3 prepared in Examples 1-4 of this invention are shown. It can be seen that the Sur-Cx-La(OH)3 prepared in Examples 1-4 is a crystalline material, which conforms to the standard La(OH)3 pattern (dashed line).

[0049] Figure 3 The image shows the nitrogen adsorption-desorption curve of the phosphorus adsorbent Sur-C18-La(OH)3 prepared in Example 4 of this invention; it can be seen that this material has a high specific surface area of ​​57.43 m². 2 g -1 .

[0050] Figure 4 The figure shows the pore size distribution of the phosphorus adsorbent Sur-C18-La(OH)3 prepared in Example 4 of the present invention. The figure shows that the pore size of Sur-C18-La(OH)3 is mainly distributed in mesopores within the range of 2-50 nm, which indicates that the material is a mesoporous material.

[0051] The phosphorus adsorption performance of Sur-Cx-La(OH)3 prepared in Examples 1-4 above was tested:

[0052] Adsorption kinetics is an important indicator of the adsorption performance of an adsorbent. The conditions for this adsorption kinetics experiment were: initial phosphoric acid concentration 2 mg / L. -1 The temperature was 25℃ (room temperature), the pH was 6-7, and the adsorbent dosage was 0.1 g / L. -1 .

[0053] Figure 5 The figures show the adsorption kinetics and fitting diagrams of the phosphorus adsorbents Sur-Cx La(OH)3 and the comparative example La(OH)3 prepared in Examples 1-4 of this invention. It can be seen from the figures that the adsorption effect of Sur-Cx La(OH)3 is better than that of the comparative example, especially in low-concentration scenarios (initial concentration approximately 2 mg PL). -1 In this process, the equilibrium adsorption capacity can be reached to 80% within three to five minutes, with the phosphate concentration decreasing from 2 mg / L. -1 Up to 0.5 mg / L -1 That is, the phosphate removal rate is 75% within 3-5 minutes, and the phosphate removal rate can reach nearly 100% within 30 minutes of reaction time. The concentration of phosphate after removal is less than 0.02 mg / L (below the detection limit of spectrophotometry); among them, the adsorbent in Example 4 has the best effect.

[0054] Figure 6 The adsorption isotherms and fitting diagrams of the phosphorus adsorbents Sur-Cx La(OH)3 and comparative example La(OH)3 prepared in Examples 1-4 of this invention are shown; from Figure 6 It can be seen that, in the adsorption isotherm experiment, compared with the control example, the adsorbent prepared by surfactant-mediated adsorption has a higher and faster adsorption capacity under the same phosphate concentration; the adsorption isotherm fitting of the Langmuir model further shows ( Figure 6 (and Table 1), the maximum phosphorus adsorption capacity q of Sur-C18-La(OH)3 max It can reach 308.86 mg g -1 Compared with La(OH)3(q) max =210.75mg g -1 Its adsorption capacity was increased by 50%, and the adsorption rate constant (k2 value = 0.071 g mg) was also improved. - 1 min -1 It was also compared to the control group (k2 = 0.029 g mg). -1 min -1 It's also faster.

[0055] Table 1. Summary of isotherm fitting results for Sur-Cx-La(OH)3 and La(OH)3

[0056]

[0057] Based on the above examples, the surfactant-mediated lanthanum hydroxide provided by this invention exhibits significantly superior phosphorus adsorption performance compared to the control example. This is in contrast to the attapulgite-loaded lanthanum and γ-Fe₂O₃ on CN202310366119.X. The Sur-C₁₈-La(OH)₃ material provided by this invention, under neutral low-concentration phosphorus (pH = 7, 2 mg PL) conditions... -1 In similar processing scenarios, the amount of material used in this invention is only 0.1 g / L. -1 The reaction time was reduced to below the phosphorus detection limit within 30 minutes, while the control patent CN202310366119.X had a loading of lanthanum and γ-Fe2O3 on attapulgite clay of 0.8 g / L. -1 The reaction time is 24 hours.

[0058] Furthermore, the phosphorus adsorbent of the present invention also exhibits excellent selectivity. Figure 7 This is an experimental diagram showing the anion coexistence competition between the phosphorus adsorbent Sur-C18-La(OH)3 prepared in Example 4 of this invention and the comparative example La(OH)3. In practical applications, the phosphorus removal rate of Sur-C18-La(OH)3 is basically unaffected by the presence of competing anions, and the removal rate can still reach 100%. Only when HCO3- in the water is present is the removal rate significantly reduced. - At a concentration of 0.05 M, the phosphate adsorption rate decreases, but it can still reach 76%.

[0059] Example 5

[0060] 2.83 g of anhydrous lanthanum sulfate (La2(SO4)3) and 0.393 g of octadecyltrimethylammonium bromide were used in a molar ratio of 5:1, with the remainder the same as in Example 4. Using the same method as in Example 4, the adsorption capacity was increased by 47% compared to lanthanum hydroxide without a long-chain surfactant, and the adsorption capacity of low-concentration phosphoric acid (2 mg / L) was also increased. -1 Under these conditions, phosphorus adsorption performance is significantly improved, with phosphorus removal reaching below the detection limit within half an hour.

[0061] Example 6

[0062] The molar ratio of 1.86 g lanthanum chloride heptahydrate (LaCl3·7H2O) and 0.098 g hexadecyltrimethylammonium bromide was 20:1, and the rest was the same as in Example 3. Using the same method as in Example 3, in a low concentration of phosphoric acid (2 mg / L... -1 Under these conditions, the adsorption capacity is reduced to below the detection limit within half an hour, with a maximum saturation adsorption capacity of approximately 280 mg / g. -1 It is more than 35% higher than the control group (lanthanum hydroxide without long-chain surfactants).

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An application of a long-chain alkyl surfactant-mediated lanthanum hydroxide material, characterized in that, The long-chain alkyl surfactant-mediated lanthanum hydroxide material is used for the separation, removal, or enrichment of phosphates in water. The long-chain alkyl surfactant-mediated lanthanum hydroxide material is prepared by the following method: alkaline co-heat precipitation from a soluble lanthanum salt and alkyltrimethylammonium bromide in a pressure-resistant reactor under closed conditions; the alkyl group in the alkyltrimethylammonium bromide is dodecyl to octadecyl, calculated as C1. x TAB, where x = 12 - 18; The method specifically includes the following steps: (1) Dissolve the soluble lanthanum salt and alkyltrimethylammonium bromide in deionized water; shake and adjust the pH to 9-11, and a white flocculent precipitate appears in the reactor; (2) Transfer the mixed suspension obtained in step (1) to a pressure-resistant reactor and react it at 60~100℃ and 110~160℃ respectively under closed conditions for 6~12h. After cooling, take it out. (3) Centrifuge the solid-liquid mixture obtained in step (2), remove the supernatant, and wash and dry the resulting precipitate to obtain highly dispersed surfactant-mediated lanthanum hydroxide material.

2. The application of the long-chain alkyl surfactant-mediated lanthanum hydroxide material according to claim 1, characterized in that, The soluble lanthanum salts include lanthanum nitrate, lanthanum chloride, or lanthanum sulfate.

3. The application of the long-chain alkyl surfactant-mediated lanthanum hydroxide material according to claim 1, characterized in that, The molar ratio of the soluble lanthanum salt to alkyltrimethylammonium bromide is 5~20:

1.

4. The application of the long-chain alkyl surfactant-mediated lanthanum hydroxide material according to claim 1, characterized in that, In step (1), the oscillation is performed at a shaking speed of 200-400 rpm for 3-6 hours.

5. The application of the long-chain alkyl surfactant-mediated lanthanum hydroxide material according to claim 1, characterized in that, In step (3), centrifugation is performed at 7000~9000 rpm for 10~30 min.

6. The application of the long-chain alkyl surfactant-mediated lanthanum hydroxide material according to claim 1, characterized in that, In step (3), the washing process involves multiple washes with deionized water and ethanol, and the drying process involves heating in a forced-air drying oven at 100~150℃ for 10~14 hours.

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