A deep phosphorus removal material and its preparation method and application

Abstract

The present invention relates to the field of water treatment technology, and in particular to a deep phosphorus removal material and its preparation method and application, comprising at least the following steps: S1, dissolving a lanthanide metal salt and bentonite in an ethanol solution, ultrasonically treating them, to obtain a lanthanide metal salt alcohol solution and a bentonite alcohol solution; S2, sequentially adding the lanthanide metal salt alcohol solution and an organosilane ammonia hydrolyzate to a magnetically dispersed bentonite alcohol solution sample, immersing them at room temperature for 6 hours, and then filtering to obtain a solid precipitate; S3, washing, drying, grinding, and sieving the solid precipitate in sequence to obtain a deep phosphorus removal material. The deep phosphorus removal material provided by the present invention has improved adsorption capacity and adsorption rate, and after 5 consecutive adsorption-desorption cycles (single cycle time 450 minutes), the phosphorus removal rate can still be maintained at more than 71.1%; at the same time, it shows excellent tolerance in complex water bodies, exhibits good potential for selective phosphorus adsorption, and has good market application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and in particular to a deep phosphorus removal material, a preparation method and an application thereof. Background Art

[0002] Traditional biological treatment technologies have limitations in removing phosphate from wastewater, with effluent phosphate concentrations typically exceeding 0.5 mg / L. This results in excessive phosphorus (P) discharge into natural water bodies. This can trigger eutrophication, such as algal blooms and red tides, posing a serious threat to drinking water supplies and the biodiversity of aquatic ecosystems. As an efficient and cost-effective water treatment technology, adsorption has been widely used in the field of phosphorus removal, meeting the requirements for deep phosphorus removal, i.e., reducing effluent phosphate concentrations by an order of magnitude compared to traditional technologies.

[0003] Currently, a range of high-capacity metal-based adsorption materials have been developed for phosphorus removal from water. However, most of these materials pose a risk of metal toxicity, potentially posing a threat to aquatic ecosystems. They also have a narrow scope of application and are difficult to adapt to complex and changing aquatic environments. The complex synthesis process leads to high production costs, making them unsuitable for large-scale industrial applications. In contrast, bentonite-based materials have attracted considerable attention due to their natural non-toxicity and favorable economic benefits. However, in practical applications, existing bentonite-based materials have low adsorption rates and capacities for phosphate in water, making them difficult to meet the requirements for efficient phosphorus removal.

[0004] To date, numerous metal-modified bentonite materials (such as iron-, lanthanum-, and zirconium-modified bentonites) have been developed to meet stringent phosphorus emission standards. Lanthanum, due to its stronger affinity for phosphate and the stability of the resulting lanthanum phosphate, has been widely used in bentonite modification. Its commercial product, lanthanum-modified bentonite (LMB), is popular for eutrophication management in 200 lakes worldwide. However, commercial lanthanum-modified bentonite exhibits slow adsorption rates and poor selectivity in low-phosphorus waters, making it difficult to achieve deep phosphorus removal (less than 0.1 mg / L). Furthermore, coexisting anions and organic matter in real-world waters significantly interfere with the phosphorus removal efficiency of commercial lanthanum-modified bentonite, reducing its adsorption performance. These factors severely limit the widespread adoption of existing lanthanum-modified bentonite-based materials in industrial and commercial applications. Therefore, the development of a new bentonite material that combines high adsorption performance, anti-interference capabilities, environmental friendliness, and cost-effectiveness is of great scientific significance and application value. Summary of the Invention

[0005] In order to solve the above problems, the first aspect of the present invention provides a method for preparing a deep phosphorus removal material, which comprises at least the following steps:

[0006] S1, dissolving a lanthanide metal salt and bentonite in an ethanol solution, and then ultrasonically treating the solution to obtain a lanthanide metal salt alcohol solution and a bentonite alcohol solution;

[0007] S2, sequentially adding the lanthanide metal salt alcohol solution and the organosilane ammonia hydrolyzate to the magnetically dispersed bentonite alcohol solution sample, immersing at room temperature for 6 hours, and then filtering to obtain a solid precipitate;

[0008] S3. Washing, drying, grinding and screening the solid precipitate in sequence to obtain a deep phosphorus removal material.

[0009] In one embodiment, the ratio of the lanthanide metal salt to the ethanol solution in step S1 is 0.1307 g:20 mL.

[0010] In one embodiment, the ratio of bentonite to ethanol solution in step S1 is 1 g:20 mL.

[0011] In one embodiment, the ultrasonic treatment in step S1 is performed under the following conditions: an ultrasonic frequency of 53 kHz and an ultrasonic time of 10-20 min. Preferably, the ultrasonic time is 10 min.

[0012] In one embodiment, in step S1, after the bentonite is dissolved in the ethanol solution and ultrasonically treated, a high-speed dispersion treatment is performed. The conditions for the high-speed dispersion treatment are 1000 rpm at room temperature and a dispersion time of 20-30 minutes. Preferably, the dispersion time is 25 minutes.

[0013] In one embodiment, the mass concentration of the ethanol solution is 50%.

[0014] In one embodiment, the preparation method of the organosilane ammonia hydrolyzate is: dissolving the organosilane ammonia in deionized water, and the hydrolysis time is 10-20 minutes. Preferably, the hydrolysis time is 10 minutes.

[0015] In one embodiment, the mass concentration of organosilane ammonia in the organosilane ammonia hydrolyzate is any one of 1.3%, 2.6%, 5.2% and 10.4%.

[0016] In one embodiment, the magnetic dispersion in step S2 is performed under magnetic stirring at room temperature and a rotation speed of 200 rpm.

[0017] In one embodiment, the lanthanide metal salt comprises lanthanum chloride.

[0018] In one embodiment, the organosilane amine includes 3-(phenylamino)propyltrimethoxysilane.

[0019] In one embodiment, the S3 step is specifically as follows: washing the solid precipitate with water and ethanol in sequence, drying it at room temperature with ventilation for 12 hours, grinding it, and passing it through a 200-mesh sieve to obtain the deep phosphorus removal material.

[0020] A second aspect of the present invention provides a deep phosphorus removal material prepared according to the above preparation method.

[0021] In one embodiment, the deep phosphorus removal material is NH2-La-Ben(Et).

[0022] A third aspect of the present invention provides an application of a deep phosphorus removal material for removing phosphates from water.

[0023] Beneficial effects

[0024] 1. This invention innovatively develops a room-temperature aqueous co-assembly modification process for bentonite, constructing a bifunctional active interface through the synergistic coordination of 3-(phenylamino)propyltrimethoxysilane (APTES) and lanthanum chloride. This molecular-level interface engineering promotes protonation and reconstruction of amino groups on the silicate surface, significantly improving surface mass transfer efficiency, enabling efficient adsorption at a low phosphorus concentration of 0.5 mg / L, and significantly enhancing adsorption kinetics and selectivity.

[0025] 2. The deep phosphorus removal material prepared in this application has improved adsorption capacity (58.8 mg / g) and adsorption rate (0.82 g / (mg•min)), and after 5 consecutive adsorption-desorption cycles (single cycle time 450 minutes), the phosphorus removal rate can still be maintained above 71.1%.

[0026] 3. The present invention utilizes an alcohol-based dispersion system to achieve a highly uniform loading distribution of lanthanide metals on the surface of the bentonite carrier. This significantly enhances the probability of interfacial contact with phosphate ions by increasing the exposed density and spatial accessibility of active sites. This structural characteristic promotes directional coordination within the inner Helmholtz layer at the adsorption interface, strengthening the specific inner-sphere complexation mechanism, thereby achieving a dual-effect enhancement in complex aqueous environments: maintaining strong electrostatic capture capabilities while also possessing excellent anti-interference properties. Based on this synergistic mechanism, the material maintains 97.2% of its phosphorus adsorption capacity under an ultra-high hydraulic shock load of 8000 BV. Its efficient mass transfer characteristics and selective adsorption advantages provide an innovative solution for the efficient adsorption of low-concentration phosphorus.

[0027] 4. The preparation method provided by this application is simple, and the raw materials are readily available and inexpensive. The simple impregnation method has significant economic benefits compared to metal-based materials and bentonite-based materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1This is a comparison chart of the phosphorus removal efficiency of the deep phosphorus removal materials prepared in Examples 1-4;

[0029] Figure 2 Isothermal curves of phosphate adsorption by the deep phosphorus removal materials prepared in Example 3 and Comparative Examples 1-2;

[0030] Figure 3 The figure is a kinetic curve diagram of phosphate adsorption by the deep phosphorus removal materials prepared in Example 3 and Comparative Examples 1-2;

[0031] Figure 4 This is a graph showing the cyclic adsorption performance of the deep phosphorus removal material prepared in Example 3;

[0032] Figure 5 This is a comparison chart of La ion leaching in the cyclic adsorption experiment of phosphate by the deep phosphorus removal materials prepared in Example 3 and Comparative Examples 1-2;

[0033] Figure 6 This is a comparison chart of the phosphorus concentration of the filtrate after phosphate treatment using the deep phosphorus removal materials prepared in Example 3 and Comparative Examples 1-2 in a fixed bed adsorption column;

[0034] Figure 7 The distribution coefficient diagram of the deep phosphorus removal materials prepared in Example 3 and Comparative Examples 1-2 for different coexisting ions;

[0035] Figure 8 The deep phosphorus removal materials prepared in Example 3 and Comparative Examples 1-2 react with different coexisting ions (NO3 - 、SO4 2- ) relative separation constant diagram;

[0036] Figure 9 The deep phosphorus removal materials prepared in Example 3 and Comparative Examples 1-2 react with different coexisting ions (Cl – 、HCO3 – ) relative separation constant diagram;

[0037] Figure 10 Phosphorus removal efficiency diagram of the deep phosphorus removal material prepared in Example 3 under different coexisting ion concentrations. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and Examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. The experimental methods for which specific conditions are not specified in the examples are carried out according to conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used for which the manufacturer is not specified are conventional products that can be purchased commercially.

[0039] The normal temperature in this application is 24°C.

[0040] Example 1

[0041] A first aspect of this embodiment provides a method for preparing a deep phosphorus removal material, comprising the following steps:

[0042] S1. Dissolve 0.1307 g of lanthanum chloride and 0.1 g of bentonite in 20 mL of ethanol solution, followed by ultrasonic treatment to obtain a lanthanum chloride alcohol solution and a bentonite alcohol solution;

[0043] S2, sequentially adding the lanthanum chloride alcohol solution and the organosilane ammonia hydrolyzate to the magnetically dispersed bentonite alcohol solution sample, immersing at room temperature for 6 hours, and then filtering to obtain a solid precipitate;

[0044] S3. Wash the solid precipitate with water and ethanol in sequence, dry it at room temperature with ventilation for 12 hours, grind it, and pass it through a 200-mesh sieve to obtain the deep phosphorus removal material.

[0045] The ultrasonic treatment conditions in step S1 are as follows: ultrasonic frequency is 53 kHz, and ultrasonic time is 10 min.

[0046] In step S1, after the bentonite is dissolved in the ethanol solution and ultrasonically treated, it is necessary to perform a high-speed dispersion treatment. The conditions for the high-speed dispersion treatment are 1000 rpm at room temperature and a dispersion time of 25 min.

[0047] The mass concentration of the ethanol solution is 50%.

[0048] The preparation method of the organosilane ammonia hydrolyzate is as follows: dissolving the organosilane ammonia in deionized water, and the hydrolysis time is 10 minutes.

[0049] The mass concentration of organosilane ammonia in the organosilane ammonia hydrolyzate is 1.3%.

[0050] The organosilane amino is 3-(phenylamino)propyltrimethoxysilane.

[0051] The magnetic dispersion conditions in step S2 are magnetic stirring at room temperature and a rotation speed of 200 rpm.

[0052] The second aspect of this embodiment provides a deep phosphorus removal material prepared according to the above preparation method. The deep phosphorus removal material is recorded as NH2-La-Ben(Et).

[0053] The third aspect of this embodiment provides an application of a deep phosphorus removal material for removing phosphates from water bodies.

[0054] Example 2

[0055] The specific implementation of this embodiment is the same as that of Example 1, except that the mass concentration of the organosilane ammonia in the organosilane ammonia hydrolyzate is 2.6%.

[0056] Example 3

[0057] The specific implementation of this embodiment is the same as that of Example 1, except that the mass concentration of the organosilane ammonia in the organosilane ammonia hydrolyzate is 5.2%.

[0058] Figure 4 This is a diagram of the cyclic adsorption performance of the deep phosphorus removal material prepared in Example 3.

[0059] Figure 10 Phosphorus removal efficiency diagram of the deep phosphorus removal material prepared in Example 3 under different coexisting ion concentrations.

[0060] Example 4

[0061] The specific implementation of this embodiment is the same as that of Example 1, except that the mass concentration of the organosilane ammonia in the organosilane ammonia hydrolyzate is 10.4%.

[0062] Figure 1 This is a comparison chart of the phosphorus removal efficiency of the deep phosphorus removal materials prepared in Examples 1-4.

[0063] Comparative Example 1

[0064] The specific implementation of this comparative example is the same as that of Example 1, except that no organosilane ammonia hydrolyzate is added in step S2.

[0065] Comparative Example 2

[0066] This comparative example uses commercially available Phoslock ® Phosphorus-locking agent was purchased from Shanghai Fengsile Environmental Technology Co., Ltd.

[0067] Performance Testing

[0068] 1. Phosphorus removal experiment in water with low phosphorus concentration

[0069] 100 mg of the deep phosphorus removal material prepared in Examples 1-4 was added to a solution with a pH of 7.0±0.5 and an initial phosphorus concentration of 0.5 mg / L, and the phosphorus removal experiments of Examples 1, 2, 3 and 4 were carried out respectively. The phosphorus removal efficiency obtained is shown in the attached figure. Figure 1 ;

[0070] from Figure 1 It can be seen that when the APTES concentration increases from 1.3% to 5.2%, the phosphorus removal efficiency of the system shows a linear improvement trend, significantly increasing from 72.9% to 91.5%; and when the APTES concentration exceeds 5.2%, the phosphorus removal efficiency enters a plateau period, and the performance fluctuation range narrows to within ±1.5%.

[0071] 2. Adsorption isotherm and kinetic experiments

[0072] In the adsorption isotherm experiments, 100 mg of adsorbent (the deep phosphorus removal materials from Example 3 and Comparative Examples 1-2) was added to a solution with a pH of 7.0 ± 0.5 and an initial phosphorus concentration of 0.1-200 mg / L. The solution was shaken at 350 rpm for 12 hours at a constant temperature of 25°C. In the adsorption kinetics experiments, 100 mg of adsorbent was dispersed in 50 mL of a 0.5 mg / L phosphate solution and the experiment was conducted at 25°C. 0.5 mL of water was sampled at regular intervals over a period of 1-120 minutes to determine the residual phosphorus concentration. After shaking, the solution was filtered through a 0.22 μm polyethersulfone membrane, and the supernatant was collected.

[0073] Test results see Figure 2-Figure 3 . Through the adsorption isotherm ( Figure 2 ) and dynamics ( Figure 3 Comparison of experimental data quantitatively revealed differences in adsorption capacity and kinetic parameters between Example 3, Comparative Example 1, and Comparative Example 2 at different initial phosphorus concentrations. Langmuir isotherm fitting results indicate that at 298K, Example 3 achieved a maximum adsorption capacity of 58.8 mg / g, 3.36 times and 5.94 times that of Comparative Example 1 (17.5 mg / g) and Comparative Example 2 (9.9 mg / g), respectively. Notably, within the initial phosphorus concentration range of 0.1-200 mg / L, the adsorption capacity-concentration curve for Example 3 exhibited the steepest upward trend. In particular, in the low concentration range of 0.1-20 mg / L, its adsorption efficiency was significantly improved compared to the comparative example sample. This phenomenon is likely related to the higher shear surface potential (+8.9 mV, pH=7) and optimized specific surface area (89.28 m² / g) of Example 3, properties that enhance the adsorbent's physical adsorption capacity for negatively charged phosphate, particularly the significantly enhanced electrostatic attraction.

[0074] According to the kinetic fitting results, the adsorption process of the embodiment of the present application is more consistent with the pseudo-second-order kinetic model (R²>0.99), and its rate constant k2 reaches 1.24 min -1 , respectively, comparative example 1 (0.74 min -1 ) and Comparative Example 2 (0.61 min -1), indicating that chemical adsorption is the dominant mechanism of adsorption. Compared to existing modified clay mineral adsorbents (including processes such as acid / alkali / heat treatment, metal doping, and layered double hydroxide modification), this example, while maintaining a low dosage (<0.5 g / L), not only achieves an adsorption capacity that reaches the industry-leading level for clay mineral adsorption passivation, but also significantly improves its adsorption rate compared to similar products. This breakthrough performance improvement is primarily due to the unique amino functionalization modification strategy and the resulting synergistic adsorption effect.

[0075] 3. Regeneration cycle experiment

[0076] In the regeneration experiment, the used NH2-La-Ben(Et) adsorbent prepared in Example 3 was dispersed in a 1 M NaOH eluent at a solid-to-liquid ratio of 1 g / L. After shaking for 2 hours, the mixture was filtered and separated. The mixture was rinsed with deionized water to a neutral pH and then vacuum-dried at 65°C. Five regeneration cycles were performed. The lanthanum and phosphorus in the adsorbent were dissolved with hydrofluoric acid and analyzed using an inductively coupled plasma optical emission spectrometer (ICP-OES, Agilent 5110).

[0077] 4. Adsorption column experiment

[0078] In the adsorption column experiments, a fixed-bed adsorption column (10 mm inner diameter, 7 mm height) was used, filled with 30% (mass fraction) adsorbent and 70% (mass fraction) block dolomite. A solution containing 0.5 mg / L phosphorus was continuously delivered at a constant flow rate of 6 mL / min via a peristaltic pump (BT100-2J, Lange, China) to investigate the dynamic phosphorus adsorption capacity of the column. The regenerated adsorbent was rinsed with NaOH and deionized water to a neutral pH before use in the next cycle experiment.

[0079] from Figure 4 As can be seen from the figure, after five cycles (450 minutes of adsorption), the phosphorus removal rate remained above 71.1%. After two regenerations, the phosphorus concentration in the simulated wastewater was reduced to a safe level for algal eutrophication (0.02 mg / L). After four cycles, the phosphorus concentration was still reduced to 0.1 mg / L, demonstrating that the deep phosphorus removal material prepared in this application has good regeneration cycle stability and meets the standards of the US National Pollutant Discharge Elimination System (NPDES) and the EU Water Framework Directive (0.1 mg / L).

[0080] Regarding material stability ( Figure 5), the La element leaching characteristics of Example 3 and Comparative Examples 1-2 showed significant differences. The results showed that the La dissolution rate of Example 3 and Comparative Example 2 within the 350-min experimental cycle showed a gradient downward trend. It is worth noting that the cumulative dissolution rate of Example 3 over the entire experimental cycle was 19.6% and 15.1% lower than that of Comparative Examples 1 and 2, respectively. The test data fully demonstrates that the examples of the present application not only have significantly improved cyclic phosphorus removal performance, but also have significantly better leaching stability than existing technical solutions.

[0081] In order to verify the practical application performance of the material, this application constructs a - 、SO4 2- 、NO3 - ) was used to systematically evaluate the engineering applicability of Example 3 under continuous fixed bed operation conditions. Figure 6 The results showed that when the inlet flow rate reached 1100 BV, 2500 BV, and 3500 BV, respectively, the effluent phosphorus concentrations of Comparative Example 2, Comparative Example 1, and Example 3 exceeded the U.S. National Pollutant Discharge Elimination System (NPDES) standard (0.1 mg / L). When the inlet flow rate increased to 3500 BV, 6500 BV, and 8000 BV, the phosphorus adsorption capacities of Comparative Example 2, Comparative Example 1, and Example 3 reached saturation critical points. Notably, Example 3 maintained effective adsorption even under a high hydraulic load of 8000 BV, achieving breakthrough treatment capacities of 1.23 times and 2.29 times that of Comparative Example 1 (6500 BV) and Comparative Example 2 (3500 BV), respectively.

[0082] In order to study the adsorbent and the coexisting anions (Cl - 、SO4 2- 、NO3 - 、HCO3 - ) selective adsorption effect, the adsorption experiment of P by Example 3, Comparative Example 1 and Comparative Example 2 was carried out in simulated water ( Figure 7 ). Partition coefficient (K d ) is defined as the ratio of the anion concentration in the solid phase to the anion concentration in the liquid phase when the reaction equilibrium is reached (a dimensionless constant of adsorption capacity under a unified standard). The K values of Example 3 (1.83) and Comparative Example 1 (0.71) for phosphate d The K values are higher than those of other coexisting anions. d The value indicates that the embodiment has a higher phosphate selectivity. 2- 、NO3 - and HCO3 - Shows higher K d values, indicating that they have poor resistance to these coexisting ions in water.

[0083] From the separation constant, α (relative separation constant) represents the relative separation ability of the adsorbent to the adsorbate. The α value of comparative example 2 is greater than 1 ( Figure 8 , 9), indicating that these two adsorbents have relatively low phosphate adsorption in coexisting systems, especially with nitrate, sulfate, and bicarbonate ions. The α values for various anions in Example 3 are all less than 1, and are even the lowest among the three adsorbents. In summary, the examples demonstrate excellent potential for selective phosphorus adsorption in low-phosphorus water bodies with the coexistence of multiple anions.

[0084] Interference experimental results under different coexisting ion concentrations ( Figure 10 ) shows that the embodiment in Cl - and SO4 2- (1-10 mM) can still maintain an adsorption rate of more than 91.4%. - (10 mM) caused the water's phosphate adsorption rate to drop sharply from 94.4% to 69.3%, a concentration level that is difficult to achieve in lake water. As the concentration of humic acid increased, the removal rate showed a U-shaped curve, indicating that humic acid promoted phosphorus adsorption at low concentrations but inhibited phosphorus adsorption at high concentrations. In summary, the deep phosphorus removal material prepared in this application showed excellent tolerance in complex water bodies compared to the control, which may be related to the inner sphere complexation and hydrogen bonding of La-OP.

Claims

1. A method for preparing a phosphorus removal material, characterized in that: At least the following steps are included: S1, dissolving a lanthanide metal salt and bentonite in an ethanol solution, and then ultrasonically treating the solution to obtain a lanthanide metal salt alcohol solution and a bentonite alcohol solution; S2, sequentially adding the lanthanide metal salt alcohol solution and the organosilane ammonia hydrolyzate to the magnetically dispersed bentonite alcohol solution sample, immersing at room temperature for 6 hours, and then filtering to obtain a solid precipitate; S3, washing, drying, grinding and screening the solid precipitate in sequence to obtain a deep phosphorus removal material; The organosilane amino is 3-(phenylamino)propyltrimethoxysilane.

2. The method for preparing the phosphorus removal material according to claim 1, wherein: The preparation method of the organosilane ammonia hydrolyzate is as follows: dissolving the organosilane ammonia in deionized water, and the hydrolysis time is 10 minutes.

3. The method for preparing the phosphorus removal material according to claim 2, wherein: The mass concentration of organosilane ammonia in the organosilane ammonia hydrolyzate is any one of 1.3%, 2.6%, 5.2% and 10.4%.

4. The method for preparing the phosphorus removal material according to claim 1, wherein: The conditions for the ultrasonic treatment in step S1 are as follows: the ultrasonic frequency is 53 kHz, and the ultrasonic time is 10-20 min.

5. The method for preparing the phosphorus removal material according to claim 1, wherein: In step S1, after the bentonite is dissolved in the ethanol solution and ultrasonically treated, it is necessary to perform a high-speed dispersion treatment. The conditions for the high-speed dispersion treatment are 1000 rpm at room temperature and a dispersion time of 20-30 min.

6. The method for preparing the phosphorus removal material according to claim 1, wherein: The conditions for magnetic dispersion in step S2 are magnetic stirring at room temperature and a rotation speed of 200 rpm.

7. The method for preparing the phosphorus removal material according to claim 1, wherein: The lanthanide metal salt includes lanthanum chloride.

8. A phosphorus removal material prepared according to the preparation method according to any one of claims 1 to 7.

9. Use of the phosphorus removal material according to claim 8, characterized in that: Used for the removal of phosphate in water.

Images