Lanthanum modified phosphorus removal agent and preparation method thereof

Abstract

The invention discloses a lanthanum-modified phosphorus removal agent and a preparation method thereof, and belongs to the technical field of phosphorus removal, and the lanthanum-modified phosphorus removal agent comprises the following preparation raw materials in parts by mass: 40-60 parts of lanthanum-loaded zeolite, 20-45 parts of porous aluminum silicate microspheres, 2-3 parts of sodium carboxymethylcellulose and 3-5 parts of ferrous sulfate; the preparation method of the porous aluminum silicate microspheres comprises the following steps: coprecipitating sodium silicate and aluminum sulfate in water, controlling the coprecipitation pH to be 10.1-10.7, and reacting at 55-65 DEG C for 5-8 hours to obtain gel; and carrying out spray granulation on the gel, sintering and activating to obtain the porous aluminum silicate microspheres. The prepared lanthanum modified phosphorus removal agent is large in phosphorus removal capacity and high in capacity retention rate after multiple phosphorus removal, and is expected to be applied to deep phosphorus removal of a sewage treatment plant.

Description

Technical Field

[0001] The present invention belongs to the technical field of phosphorus removal, and specifically relates to a lanthanum-modified phosphorus removal agent and a preparation method thereof. Background Art

[0002] Phosphorus element (P) is a key limiting factor leading to water eutrophication. Excessive phosphorus can trigger ecological disasters such as algal blooms and dissolved oxygen depletion. Treatment methods for phosphorus element include chemical precipitation method. Traditional chemical precipitation methods (such as aluminum salts and iron salts) have the advantage of low cost, but there are problems such as large sludge production and excessive residual metal ions, making it difficult to meet the increasingly strict emission standards.

[0003] Due to its high affinity with phosphate and wide pH adaptability, lanthanum has become a research hotspot for new phosphorus removal agents. Although using pure lanthanum compounds has a high adsorption capacity, the nanoparticles are prone to agglomeration, and lanthanum resources are scarce and the cost is relatively high. In the prior art, lanthanum-loaded materials are usually prepared by modifying activated carbon, clay or zeolite with lanthanum. However, the specific surface area of the carrier is insufficient, resulting in low utilization rate of active sites and poor regeneration performance. The phosphorus removal agent of lanthanum composite iron double metal oxide usually requires high-temperature (≥800 °C) calcination to form a crystal phase structure, with high energy consumption. Summary of the Invention

[0004] In order to overcome the above technical problems, the present invention provides a lanthanum-modified phosphorus removal agent and a preparation method thereof. The lanthanum-modified phosphorus removal agent prepared by the present invention has a large phosphorus removal capacity and a high capacity retention rate after multiple phosphorus removals.

[0005] The present invention solves the above technical problems through the following technical solutions.

[0006] A lanthanum-modified phosphorus removal agent, comprising the following raw materials in parts by mass: 40 - 60 parts of lanthanum-loaded zeolite, 20 - 45 parts of porous aluminosilicate microspheres, 2 - 3 parts of sodium carboxymethylcellulose, and 3 - 5 parts of ferrous sulfate; Preferably, the lanthanum-modified phosphorus removal agent comprises the following raw materials in parts by mass: 40 - 50 parts of lanthanum-loaded zeolite, 20 - 35 parts of porous aluminosilicate microspheres, 2 - 3 parts of sodium carboxymethylcellulose, and 3 - 5 parts of ferrous sulfate; The preparation method of the porous aluminosilicate microspheres comprises the following steps: sodium silicate and aluminum sulfate are co-precipitated in water to obtain a gel, and the gel is spray granulated and then sintered and activated to obtain porous aluminosilicate microspheres; The preparation method of the lanthanum-loaded zeolite comprises the following steps: after acid activation of clinoptilolite powder, an ion exchange reaction is carried out with lanthanum nitrate solution, and then calcination is carried out. Among them, after acid activation of clinoptilolite, its aluminum-oxygen tetrahedron framework fixes La 3+ , forming a stable La-O-Si bond to avoid lanthanum loss.

[0007] Further, the coprecipitation is carried out at a pH of 10.1 - 10.7 and a temperature of 55 - 65 °C for 5 - 8 h.

[0008] Further, the particle size of the product discharged from the spray granulation is D50 of 100 - 150 μm.

[0009] Further, the sintering activation is carried out by roasting at 580 - 610 °C for 0.5 - 2 h.

[0010] In some preferred embodiments, the porous aluminosilicate microspheres comprise the following raw materials in parts by mass: 30 - 60 parts of sodium silicate, 20 - 30 parts of aluminum sulfate, 3 - 7 parts of polyethylene glycol, and 20 - 35 parts of water; preferably, the porous aluminosilicate microspheres comprise the following raw materials in parts by mass: 40 - 50 parts of sodium silicate, 20 - 35 parts of aluminum sulfate, 4 - 6 parts of polyethylene glycol, and 20 - 30 parts of water; In the present invention, the polyethylene glycol comprises PEG400:PEG2000, and the mass ratio of PEG400:PEG2000 is 10:3 - 5. In the present invention, the abundant pores of the porous aluminosilicate microspheres improve the dispersion degree of the active components and avoid the 3+ agglomeration and inactivation of La. Two types of pore-forming agents, PEG400 and PEG2000, are added during the preparation by the coprecipitation method, so that the porous aluminosilicate microspheres have a pore structure with different pore diameters.

[0011] In the present invention, the modulus of the sodium silicate is 1.5 - 3.5, preferably 3.0 - 3.5.

[0012] In the present invention, the specific surface area of the porous aluminosilicate microspheres is 300 - 350 m 2 / g, preferably 300 - 330 m 2 / g.

[0013] In the present invention, the feed liquid ratio of the clinoptilolite powder to the lanthanum nitrate solution is 0.1 - 0.2 g / L.

[0014] In the present invention, the concentration of the lanthanum nitrate solution is 0.3 - 0.8 mol / L, preferably 0.5 - 0.7 mol / L.

[0015] In the present invention, the pH needs to be controlled during the ion exchange reaction, and dilute nitric acid is used to control the pH of the ion exchange reaction to be 4.5 - 5.0.

[0016] In the present invention, the time of the ion exchange reaction is 5 - 12 h.

[0017] In the present invention, the acid activation is to stir the clinoptilolite powder in a 2.5 - 3.5 mol / L HCl solution at 55 - 65 °C for 2 - 3 h and then wash it to neutral.

[0018] In the present invention, the calcination is carried out at 400 - 450 °C for 1.5 - 3.5 h.

[0019] In the present invention, the lanthanum loading amount of the lanthanum-loaded zeolite is 8 - 10 wt%. In the present invention, the specific surface area of the lanthanum-loaded zeolite ≥ 200 m 2 / g, preferably 200 - 220 m 2 / g.

[0020] In the present invention, the phosphorus removal capacity of the lanthanum-modified phosphorus remover ≥ 40 mg P / g, preferably 43 - 50 mg P / g.

[0021] In the present invention, the lanthanum-modified phosphorus remover is used in the range of pH 5 - 9.

[0022] In the present invention, the lanthanum-modified phosphorus remover is regenerated by soaking in 1 mol / L NaOH, and the phosphorus removal capacity retention rate after 5 regeneration times ≥ 80%.

[0023] The present invention also discloses a preparation method of a lanthanum-modified phosphorus remover, which includes the following steps: wet kneading and granulating lanthanum-loaded zeolite, porous aluminosilicate microspheres and sodium carboxymethylcellulose, drying, and then impregnating in a ferrous sulfate solution for curing. The ferric ions generated by the oxidation of ferrous ions can form iron phosphate precipitate with phosphate radicals, jointly constructing a dual-effect phosphorus removal system with lanthanum phosphate precipitate.

[0024] The concentration of the ferrous sulfate solution is 0.1 - 0.2 mol / L; The impregnation time is 20 - 40 min; The curing temperature is 140 - 160 °C and the time is 2 - 3 h.

[0025] On the basis of conforming to the common knowledge in the art, the above preferred conditions can be combined arbitrarily to obtain various preferred examples of the present invention.

[0026] Compared with the prior art, the beneficial effects of the present invention are: 1. The lanthanum-loaded zeolite of the present invention provides a high density of lanthanum ions to fix phosphates. The removal of phosphorus is not a simple adsorption, but experiences: diffusion - surface coordination - LaPO4 crystal nucleus formation - crystal grain growth; the porous aluminosilicate microspheres of the present invention contain different levels of pore sizes, which can provide a loading space for lanthanum.

[0027] 2. The lanthanum-modified phosphorus remover of the present invention has regeneration performance. First, the La - O - Si bonds formed on the surface of lanthanum ions and clinoptilolite are not easily lost; furthermore, the silanol groups (Si - OH) on the surface of porous aluminosilicate microspheres form Si - O - La covalent bonds with lanthanum ions, which is beneficial to maintaining the structural stability during the regeneration cycle.

[0028] 3. The lanthanum-modified phosphorus adsorbent prepared by the present invention has a high phosphorus adsorption capacity, which is ≥ 40 mg P / g in some preferred embodiments; and the capacity retention rate is ≥ 80% after being used five times, and the capacity retention rate is 82 - 88% in some preferred embodiments. This solution can remove phosphorus efficiently, stably and at low cost, and is expected to be applied to the advanced phosphorus removal in sewage treatment plants, having market application potential. Detailed Embodiments

[0029] To facilitate the understanding of the present invention, the following will describe the present invention more comprehensively and meticulously in conjunction with preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0030] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0031] The "range" disclosed in the present invention is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The ranges defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4 and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4 and 2 - 5. In the present invention, unless otherwise stated, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" have been fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0032] If there is no special instruction, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0033] If there is no special instruction, all technical features and optional technical features of the present invention can be combined with each other to form new technical solutions.

[0034] Unless otherwise specified, all steps of the present invention can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out sequentially, or may include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0035] Unless otherwise specified, the terms "comprising" and "including" mentioned in the present invention mean open-ended or may also be closed-ended. For example, the "comprising" and "including" may mean that other components not listed may also be included or comprised, or may only include or comprise the listed components.

[0036] Unless otherwise specified, in the present invention, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) while B is true (or exists); or both A and B are true (or exist).

[0037] The raw material information used in the following examples is as follows: Clinoptilolite was purchased from Shijiazhuang Huabang Mineral Products Co., Ltd., and the particle size was 200 mesh; Including but not limited to the above raw material manufacturers.

[0038] Example 1 1. The lanthanum-modified phosphorus removal agent of this example is composed of the following parts by mass of preparation raw materials: 50 parts of lanthanum-loaded zeolite, 30 parts of porous aluminosilicate microspheres, 3 parts of sodium carboxymethylcellulose, and 5 parts of ferrous sulfate.

[0039] (1) Porous aluminosilicate microspheres The porous aluminosilicate microspheres are composed of the following parts by mass of preparation raw materials: 45 parts of sodium silicate, 30 parts of aluminum sulfate, 5 parts of polyethylene glycol, and 25 parts of water; The mass ratio of PEG400:PEG2000 in polyethylene glycol is 10:5; According to the above formula, sodium silicate (modulus 3.2, modulus n = SiO2 / Na2O) and aluminum sulfate are co-precipitated in water, controlling the co-precipitation pH at 10.2, reacting at 50 °C for 8 h to obtain a gel; the gel is spray granulated, and the discharge particle size is D50 = 120 μm, and then sintered and activated by roasting at 610 °C for 0.5 h to obtain porous aluminosilicate microspheres, and the specific surface area of the porous aluminosilicate microspheres is 320 m 2 / g。

[0040] (2) Lanthanum-loaded zeolite The clinoptilolite powder was stirred in 3.0 mol / L HCl solution at 55 °C for 2.5 h, then washed to neutrality to complete acid activation and dried; the acid-activated clinoptilolite powder was subjected to an ion exchange reaction in 0.5 mol / L lanthanum nitrate solution. The ratio of the clinoptilolite powder to the lanthanum nitrate solution was 0.2 g / L. Dilute nitric acid was used to adjust the pH during the ion exchange reaction, and the pH of the ion exchange reaction was controlled at 4.5; the time of the ion exchange reaction was 10 h. After filtering and drying, it was sintered at 420 °C for 2 h to obtain lanthanum-loaded zeolite; the lanthanum loading of the lanthanum-loaded zeolite was 9.1 wt% (measured by the mass difference method), and the specific surface area of the lanthanum-loaded zeolite was 215 m 2 / g。

[0041] 2. The preparation method of the lanthanum-modified phosphorus remover in this example is as follows: The lanthanum-loaded zeolite, porous aluminosilicate microspheres and sodium carboxymethyl cellulose (prepared into a 5 wt% CMC solution) were wet kneaded and granulated. Granulation was carried out by twin-screw extrusion granulation, with a screw speed of 40 rpm and a die head aperture of 2.5 mm. After drying, it was impregnated in a ferrous sulfate solution (0.15 mol / L) for 35 min, and finally cured at 150 °C for 2 h to obtain the lanthanum-modified phosphorus remover.

[0042] Example 2 The difference between this example and Example 1 is as follows: Preparation method of porous aluminosilicate microspheres: Sodium silicate and aluminum sulfate were co-precipitated in water, and the pH of the co-precipitation was controlled at 10.6. The reaction was carried out at 60 °C for 5 h to obtain a gel; the gel was spray granulated, and the particle size of the discharged material was D50 = 100 μm, and then sintered and activated by roasting at 600 °C for 1 h to obtain porous aluminosilicate microspheres. The specific surface area of the porous aluminosilicate microspheres was 307 m 2 / g。

[0043] All other raw materials, steps and parameters are the same as those in Example 1.

[0044] Example 3 The difference between this example and Example 1 is as follows: The porous aluminosilicate microspheres were composed of the following raw materials in parts by mass: 60 parts of sodium silicate, 20 parts of aluminum sulfate, 5 parts of polyethylene glycol and 27 parts of water; the modulus of sodium silicate was 2.5; The specific surface area of the porous aluminosilicate microspheres was 304 m 2 / g; All other raw materials, steps and parameters are the same as those in Example 1.

[0045] Example 4 The difference between this example and Example 1 is as follows: The mass ratio of PEG400 to PEG2000 in polyethylene glycol is 10:8; The specific surface area of the porous aluminosilicate microspheres is 297 m 2 / g; All other raw materials, steps and parameters are the same as in Example 1.

[0046] Example 5 The difference between this example and Example 1 is that: The clinoptilolite in this example was not acid-activated. The clinoptilolite and lanthanum nitrate solution were directly subjected to an ion exchange reaction. All other raw materials, steps and parameters are the same as in Example 1; the lanthanum loading of the obtained lanthanum-loaded zeolite is 4.8 wt%, and the specific surface area of the lanthanum-loaded zeolite is 173 m 2 / g.

[0047] The clinoptilolite in this example was not acid-activated, and the lanthanum loading in the prepared lanthanum-loaded zeolite is less. Therefore, compared with other examples, the initial phosphorus removal capacity of the lanthanum-modified phosphorus remover in this example is poor.

[0048] Example 6 The difference between this example and Example 1 is that: The clinoptilolite powder was acid-activated by stirring in 2.5 mol / L HCl solution at 65 °C for 2 h, then washed to neutral and dried; the acid-activated clinoptilolite powder was subjected to an ion exchange reaction in 0.7 mol / L lanthanum nitrate solution. The liquid ratio of the clinoptilolite powder to the lanthanum nitrate solution was 0.1 g / L. Dilute nitric acid was used to adjust the pH during the ion exchange reaction, and the pH of the ion exchange reaction was controlled at 5.0. The time of the ion exchange reaction was 8 h. After filtering and drying, it was sintered at 450 °C for 2.5 h to obtain the lanthanum-loaded zeolite. The lanthanum loading of the lanthanum-loaded zeolite is 8.4 wt%, and the specific surface area of the lanthanum-loaded zeolite is 203 m 2 / g.

[0049] All other raw materials, steps and parameters are the same as in Example 1.

[0050] Comparative Example 1 The difference between this comparative example and Example 1 is that: The lanthanum-modified phosphorus remover in this comparative example is composed of the following raw materials in parts by mass: 70 parts of lanthanum-loaded zeolite, 3 parts of sodium carboxymethylcellulose and 5 parts of ferrous sulfate.

[0051] All other raw materials, steps and parameters are the same as in Example 1.

[0052] Comparative Example 2 The difference between this comparative example and Example 1 is that: The lanthanum-modified phosphorus remover in this comparative example is composed of the following raw materials in parts by mass: 38 parts of lanthanum-loaded zeolite, 50 parts of porous aluminosilicate microspheres, 2 parts of sodium carboxymethylcellulose and 4 parts of ferrous sulfate.

[0053] All other raw materials, steps and parameters are the same as those in Example 1.

[0054] Effect Example The phosphorus removal capacity of the lanthanum-modified phosphorus removal agent prepared in the above examples and comparative examples was tested, and the test results are shown in Table 1.

[0055] Initial phosphorus removal capacity test (adsorption test): By simulating the adsorption reaction of phosphorus-containing wastewater (pH = 7, TP is 5 mg / L) with the lanthanum-modified phosphorus removal agent, the maximum adsorption amount (mg) of phosphorus (P) per unit mass of the phosphorus removal agent (g) was measured, and the static saturated adsorption capacity was calculated.

[0056] The test method for phosphorus content refers to GB / T 11893 and is tested at a temperature of 23 ± 2 °C.

[0057] Regeneration test: After the lanthanum-modified phosphorus removal agent undergoes the adsorption test-regeneration process 5 times repeatedly, the phosphorus removal capacity of the lanthanum-modified phosphorus removal agent for the 6th time is calculated; the capacity retention rate after 5 uses is calculated, and the capacity retention rate = the phosphorus removal capacity for the 6th time / the initial phosphorus removal capacity.

[0058] The regeneration method is to soak the lanthanum-modified phosphorus removal agent after phosphorus removal in 1 mol / L sodium hydroxide solution according to a liquid-solid ratio of 1:10, oscillate at 25 °C for 2 h, and wash with deionized water until the pH = 7 - 8 to achieve regeneration.

[0059]

[0060] Application Example 700 mg of the lanthanum-modified phosphorus removal agent (prepared from the above examples and comparative examples respectively) was added to 10 L of phosphorus-containing sewage (initial pH was 6.2, TP was 106.3 mg / L). After oscillating at 23 °C for 1 h, the total phosphorus removal rate was calculated, and the results are shown in Table 2.

[0061]

[0062] Unless otherwise specified, all kinds of raw materials, reagents, instruments and equipment used in the present invention can be obtained through market purchase or can be prepared by existing methods. The specific embodiments described above have further detailed the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A lanthanum-modified phosphorus removal agent, characterized in that, It includes the following preparation raw materials in parts by mass: 40 - 60 parts of lanthanum - loaded zeolite, 20 - 45 parts of porous aluminosilicate microspheres, 2 - 3 parts of sodium carboxymethylcellulose, and 3 - 5 parts of ferrous sulfate; The preparation method of the porous aluminosilicate microspheres includes the following steps: Sodium silicate and aluminum sulfate are co - precipitated in water to obtain a gel; The gel is spray - granulated and then sintered and activated to obtain the porous aluminosilicate microspheres; The preparation method of the lanthanum - loaded zeolite includes the following steps: The clinoptilolite powder is acid - activated and then undergoes an ion - exchange reaction with lanthanum nitrate solution, and then is calcined.

2. The lanthanum-modified phosphorus removal agent according to claim 1, characterized in that, Meet at least one of the following conditions ① - ③: ① The co - precipitation is carried out by controlling the pH at 10.1 - 10.7 and reacting at 55 - 65 °C for 5 - 8 h; ② The particle size of the discharged material of the spray - granulation is D50 of 100 - 150 μm; ③ The sintering and activation is carried out by calcining at 580 - 610 °C for 0.5 - 2 h.

3. The lanthanum-modified phosphorus removal agent according to claim 1, wherein The porous aluminosilicate microspheres include the following preparation raw materials in parts by mass: 30 - 60 parts of sodium silicate, 20 - 30 parts of aluminum sulfate, 3 - 7 parts of polyethylene glycol, and 20 - 35 parts of water.

4. The lanthanum-modified phosphorus removal agent according to claim 3, characterized in that, Meet at least one of the following conditions ① - ③: ① The polyethylene glycol includes PEG400 and PEG2000, and the mass ratio of PEG400:PEG2000 is 10:3 - 5; ② The modulus of the sodium silicate is 1.5 - 3.5; ③ The specific surface area of the porous aluminosilicate microspheres is 300~350 m 2 / g.

5. The lanthanum-modified phosphorus removal agent according to claim 1, wherein Meet at least one of the following conditions ① - ④: ① The material - liquid ratio of the clinoptilolite powder and the lanthanum nitrate solution is 0.1 - 0.2 g / L; ② The concentration of the lanthanum nitrate solution is 0.3 - 0.8 mol / L; ③ During the ion - exchange reaction, the pH is controlled, and dilute nitric acid is used to control the pH of the ion - exchange reaction at 4.5 - 5.0; ④ The time of the ion - exchange reaction is 5 - 12 h.

6. The lanthanum-modified phosphorus removal agent according to claim 1, wherein, Meet at least one of the following conditions ① - ②: ① The acid - activation is to stir the clinoptilolite powder in 2.5 - 3.5 mol / L HCl solution at 55 - 65 °C for 2 - 3 h and then wash it to neutral; ② The calcination is carried out at 400 - 450 °C for 1.5 - 3.5 h.

7. The lanthanum-modified phosphorus removal agent according to claim 6, characterized in that, Meet at least one of the following conditions ① - ②: ① The lanthanum loading amount of the lanthanum - loaded zeolite is 8 - 10 wt%; ②The specific surface area of the lanthanum-loaded zeolite ≥ 200 m 2 / g.

8. The lanthanum-modified phosphorus removal agent according to claim 1, characterized in that, The phosphorus - removal capacity of the lanthanum - modified phosphorus - removing agent ≥ 40 mg P / g.

9. The preparation method of the lanthanum-modified phosphorus removal agent according to any one of claims 1 to 8, characterized in that, It includes the following steps: The lanthanum - loaded zeolite, porous aluminosilicate microspheres and sodium carboxymethylcellulose are wet - kneaded and granulated, dried, and then impregnated in a ferrous sulfate solution and cured.

10. The preparation method of the lanthanum-modified phosphorus removal agent according to claim 9, characterized in that, Meet at least one of the following conditions ① - ③: ① The concentration of the ferrous sulfate solution is 0.1 - 0.2 mol / L; ② The impregnation time is 20 - 40 min; ③ The curing temperature is 140 - 160 °C and the time is 2 - 3 h.

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