Preparation method and application of a phosphorus-absorbing matrix with self-floating function

Abstract

The present invention belongs to the technical field of eutrophication restoration of landscape water bodies and resource utilization of waste organisms, and specifically relates to a method for preparing a high-efficiency phosphorus-absorbing matrix with a self-floating function. The method comprises the following steps: using discarded shells to prepare chitosan-calcium polymer, which is subjected to at least two cross-linking reactions with a gel synthetic material to synthesize a hydrogel, and then wrapping the synthesized hydrogel on a sponge fiber skeleton to prepare a matrix with a self-floating function. At the same time, the matrix with a self-floating function and the roots of aquatic plants are fixed in a planting basket with tying ropes, and then the tying ropes are used to connect the planting baskets into pieces to form a self-floating ecological floating bed that does not require frame support and is used for treating eutrophic water bodies.

Description

Technical Field

[0001] The present invention belongs to the technical field of landscape water eutrophication restoration and waste biological resource utilization, and specifically relates to a preparation method and application of a high-efficiency phosphorus-absorbing matrix with a self-floating function. Background Art

[0002] Ecological floating beds are an emerging bioremediation technology that has been widely used in landscape water restoration. Developed from traditional constructed wetlands, they offer advantages such as low cost, easy maintenance, simple operation, minimal land use, and strong adaptability to water depth. They are increasingly being used to restore eutrophic water bodies.

[0003] The substrate is a crucial component of an ecological floating bed. Materials with large specific surface areas and adsorption properties are generally selected. Traditional ecological floating bed substrates, such as quartz sand, gravel, expanded clay, coconut fiber, and polyethylene foam, have limited adsorption properties. The primary water purification benefit of an ecological floating bed lies in its rapid and substantial absorption of ammonia nitrogen, total phosphorus, and organic matter. These nutrients are then absorbed by plant growth, resulting in nutrient transfer to the water body. Ultimately, these nutrients are removed through plant harvesting, mitigating the odor and eutrophication caused by closed or insufficient self-circulating water bodies. For total phosphorus in water, the initial substrate adsorption capacity can reach 87.5% of the total removal rate. Therefore, the substrate's adsorption capacity and rate of phosphorus adsorption in eutrophic waters are key factors limiting the further promotion and application of ecological floating beds.

[0004] Chinese patent application number CN201410649284.7 discloses an ecological floating bed and a method for purifying water, which specifically discloses the selection of magnesium slag ceramic filter balls, bentonite particles and zeolite as the main components of the floating bed matrix; Chinese patent application number CN202011380294.7 discloses a matrix adsorption material with denitrification and phosphorus removal functions, its preparation method and application, which selects lanthanum chloride as the main component of the floating bed matrix; Chinese patent application number CN202110360489.3 discloses a phosphorus removal matrix adsorption material. The invention discloses a phosphorus removal matrix material, a preparation method thereof, and an application thereof, which is prepared by mixing bentonite, quicklime, and water in a specific proportion and then heat-treating the mixture at a specific temperature. In the prior art, oyster shells, iron filings, magnesite, natural pyrite, pyrrhotite, etc. are also selected as the main components of the matrix. On the one hand, by forming phosphate precipitates such as hydroxyapatite, struvite, and octacalcium phosphate, on the other hand, phosphates are adsorbed on FeOOH or flocculated with Fe(OH)2, both of which can achieve a good ecological floating bed phosphorus removal effect. However, phosphorus removal in the prior art is achieved by forming stable chemical bonds or depositing in the bottom mud, making it difficult for plants to absorb and utilize. Once the phosphorus in the bottom mud is released, it will cause secondary pollution to the water body. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a preparation method and application of an efficient phosphorus-absorbing matrix with self-floating function, which increases the adsorption capacity of the matrix and the effective planting area of ​​the ecological floating bed, thereby improving the phosphorus removal efficiency of the ecological floating bed.

[0006] The technical solution of the present invention is as follows: The present invention provides a method for preparing a phosphorus-absorbing matrix with a self-floating function, characterized in that a chitosan-calcium polymer is prepared from discarded shells, the chitosan-calcium polymer is impregnated and loaded on a sponge fiber skeleton, and then cross-linked with a gel synthetic material at least twice to synthesize a hydrogel to obtain a matrix with a self-floating function. The method specifically comprises the following steps:

[0007] (1) Chitosan-calcium polymer: Wash, crush, and sieve the discarded shells to obtain shell powder, mix it evenly with a strong alkaline solution, hydrothermally treat it at 120°C for 2-8 hours, cool it, and wash it with deionized water until the pH is constant to obtain chitosan-calcium polymer;

[0008] (2) Primary cross-linking of the hydrogel-coated skeleton: dissolving chitosan-calcium polymer in acetic acid solution, immersing the sponge fiber in the above solution and ultrasonically treating it for 15 to 30 minutes, and then immersing it in the gel synthesis material solution and ultrasonically treating it for 30 to 60 minutes;

[0009] (3) Secondary cross-linked hydrogel-coated skeleton: Using calcium chloride as the raw material, the sponge fiber soaked in the gel synthetic material is immersed in the calcium chloride solution for 12 to 24 hours, taken out and air-dried at room temperature to obtain a self-floating and efficient phosphorus-absorbing matrix.

[0010] Furthermore, the gel synthetic material is one or more of chitosan, sodium alginate, starch, cyclodextrin, lignin, and cellulose.

[0011] Furthermore, the sponge fiber is one of wood cellulose or foamed plastic polymer sponge.

[0012] Furthermore, in step (1), the solid-to-liquid ratio of the chitin powder to the strong alkaline solution is 1:20.

[0013] Furthermore, the mass concentration of the acetic acid solution in step (2) is 5-8%; the concentration of the gel synthesis material solution is 0.6-1.2 g / L.

[0014] Furthermore, the mass concentration of the calcium chloride solution in step (3) is 2-10%.

[0015] The present invention also provides an application of a phosphorus-absorbing matrix with a self-floating function in eutrophic water treatment. The matrix prepared according to the above preparation method and the roots of aquatic plants are fixed in a planting basket with a tying rope, and then the tying rope is used to connect the planting baskets into pieces to make a self-floating ecological floating bed that does not require frame support.

[0016] Furthermore, the aquatic plants are one or more of Cyperus rotundus, Acorus calamus, Pennisetum truncatum, Pickerelleaf dahliae, Zinnia odorata and Alisma orientalis.

[0017] Furthermore, the planting basket is a square or round plastic hydroponic planting basket.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The present invention utilizes discarded shells to prepare chitosan-calcium polymer, realizing resource utilization of solid waste. At the same time, the maximum phosphorus adsorption capacity of the self-floating phosphorus-absorbing matrix is ​​1797.2 times that of ceramsite, effectively improving the phosphorus adsorption capacity and adsorption rate.

[0020] 2. The present invention utilizes a self-floating phosphorus-absorbing matrix combined with a planting basket to form an ecological floating bed, with an effective area of ​​60.99%, which is 4.32 times the effective area of ​​the existing ecological floating island, thereby increasing the effective area of ​​the ecological floating bed;

[0021] 3. The self-floating phosphorus-absorbing matrix provided by the present invention also improves plant absorption. The increase in phosphorus in plants using the matrix of the present invention generally exceeds the increase in phosphorus in plants using ceramsite and quartz sand. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the thermodynamic adsorption characteristics of chitosan-calcium polymer / sodium alginate / calcium chloride@melamine sponge (CC / SC@MF) prepared in Example 1 on chitosan-calcium polymer@melamine sponge (CC@MF) and calcium alginate@melamine sponge (SC@MF);

[0023] Figure 2 Schematic diagram of the kinetic adsorption characteristics of chitosan-calcium polymer / sodium alginate / calcium chloride@melamine sponge (CC / SC@MF) prepared in Example 1 on chitosan-calcium polymer@melamine sponge (CC@MF) and calcium alginate@melamine sponge (SC@MF);

[0024] Figure 3 This is the plan of the existing ecological floating bed;

[0025] Figure 4 This is a plan view of the ecological floating bed in Example 3;

[0026] Figure 5Schematic diagram comparing the effective planting area of ​​the actual application of the ecological floating bed in Example 3 and the existing ecological floating bed;

[0027] Figure 6 The phosphorus increase in the plants of the six aquatic plants using three different substrates over an 8-week period in Example 3 is shown. DETAILED DESCRIPTION

[0028] The present invention is further described below in conjunction with preferred embodiments. The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0029] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0030] The experimental methods in the following examples are conventional methods unless otherwise specified.

[0031] Example 1

[0032] A method for preparing a phosphorus-absorbing matrix with a self-floating function comprises the following steps:

[0033] (1) The discarded shells were cleaned, crushed, and sieved through 100 mesh. The mixture was then mixed with a 50% NaOH solution at a solid-liquid ratio (v / w) of 1:20. The mixture was hydrothermally treated at 120°C for 5 h, cooled, and washed with deionized water until the pH was constant to obtain chitosan-calcium polymer.

[0034] (2) 1.8 g of chitosan-calcium polymer prepared in step (1) was dissolved in 100 mL of 8% acetic acid solution, and a 5 cm × 5 cm × 5 cm melamine sponge block was immersed in the solution and ultrasonicated for 15 min; then immersed in 0.8 g / L sodium alginate solution for 30 min;

[0035] (3) The melamine sponge block soaked in the sodium alginate solution was immersed in a 5% calcium chloride solution again for 24 hours, taken out and air-dried at room temperature to obtain a self-floating and efficient phosphorus-absorbing matrix; at the same time, the foamed plastic polymer sponge block soaked in the sodium alginate solution can be immersed in the calcium chloride solution for multiple cycles to achieve multiple cross-linking reactions.

[0036] The self-floating phosphorus-absorbing substrate prepared in Example 1 and the aquatic plant roots are fixed in a square or round plastic hydroponic planting basket with a tying rope, and the planting baskets are then connected into pieces with the tying rope to form a self-floating ecological floating bed that does not require frame support. In this embodiment, the aquatic plants can be one or more of Cyperus rotundus, Acorus calamus, Pennisetum rubrum, Pterocarpus davidianus, Zygophyllum serrata, and Alisma orientale.

[0037] The self-floating ecological floating bed was placed in the lake water sample. The main indicators of lake water quality were: TP 0.3mg / L, NH 4+ -N8.32mg / L, COD 54.93mg / L. During the experiment, samples were taken at 0, 1, 2, 3, 4, 5, 6, 12, 24, 36, 48, 60 and 72 hours respectively to measure the total phosphorus concentration of the water samples. The specific results are shown in Table 1 below:

[0038] Table 1

[0039]

[0040] The measurement results showed that adsorption equilibrium was reached 5 hours after being placed in the ecological floating bed, and the final total phosphorus concentration of the water sample dropped to 0.05 mg / L.

[0041] Example 2

[0042] A method for preparing a phosphorus-absorbing matrix with a self-floating function comprises the following steps:

[0043] (1) The discarded shells were cleaned, crushed, and sieved through 100 mesh. The mixture was then mixed with a 50% NaOH solution at a solid-liquid ratio (v / w) of 1:20. The mixture was hydrothermally treated at 120°C for 2 h, cooled, and washed with deionized water until the pH was constant to obtain chitosan-calcium polymer.

[0044] (2) 1.6 g of chitosan-calcium polymer prepared in step (1) was dissolved in 100 ml of 5% acetic acid solution, and a 5 cm × 5 cm × 5 cm wood fiber sponge block was immersed in the solution and ultrasonicated for 30 min; then immersed in a 0.6 g / L cyclodextrin solution for 40 min;

[0045] (3) The wood fiber sponge block soaked in the cyclodextrin solution was immersed in a 2% calcium chloride solution for 18 hours, taken out and air-dried at room temperature to obtain a self-floating and efficient phosphorus-absorbing matrix.

[0046] The self-floating phosphorus-absorbing substrate prepared in Example 2 and the aquatic plant roots are fixed in a square or round plastic hydroponic planting basket with a tying rope, and the planting baskets are then connected into pieces with the tying rope to form a self-floating ecological floating bed that does not require frame support. In this embodiment, the aquatic plants can be one or more of Cyperus rotundus, Acorus calamus, Pennisetum rubrum, Pterocarpus serrata, Zygophyllum serratum, and Alisma orientale.

[0047] The self-floating ecological floating bed was placed in the lake water sample. The main indicators of the lake water quality were: TP 0.99mg / L, NH 4+ -N5.01mg / L, COD 67.41mg / L. During the experiment, samples were taken at 0, 1, 2, 3, 4, 5, 6, 12, 24, 36, 48, 60 and 72 hours respectively to measure the total phosphorus concentration of the water samples. The specific results are shown in Table 2 below:

[0048] Table 2

[0049]

[0050] The measurement results showed that adsorption equilibrium was reached 12 hours after being placed in the ecological floating bed, and the final total phosphorus concentration of the water sample dropped to 0.06 mg / L.

[0051] Example 3

[0052] A method for preparing a phosphorus-absorbing matrix with a self-floating function comprises the following steps:

[0053] (1) The discarded shells were cleaned, crushed, and sieved through 100 mesh. The mixture was then mixed with a 50% KOH solution at a solid-liquid ratio (v / w) of 1:20. The mixture was hydrothermally treated at 120°C for 8 h, cooled, and washed with deionized water until the pH was constant to obtain chitosan-calcium polymer.

[0054] (2) Dissolve 2 g of chitosan-calcium polymer obtained in step (1) in 100 ml of 10% acetic acid solution, immerse a 5 cm × 5 cm × 5 cm polyurethane sponge block in the solution and ultrasonicate for 20 min; then immerse it in 1.2 g / L starch solution for 60 min;

[0055] In addition to the above embodiments, in the preparation process of the phosphorus-absorbing matrix with self-floating function, the gel synthetic material can also be selected from chitosan, lignin, cellulose and other materials and mixtures thereof;

[0056] (3) The polyurethane sponge block soaked in the starch solution was immersed in a 10% calcium chloride solution for 12 hours, and then air-dried at room temperature to obtain a self-floating and efficient phosphorus-absorbing matrix;

[0057] The self-floating phosphorus-absorbing substrate prepared in Example 3 and the aquatic plant roots are fixed in a square or round plastic hydroponic planting basket with a tying rope, and the planting baskets are then connected into pieces with the tying rope to form a self-floating ecological floating bed that does not require frame support. In this embodiment, the aquatic plants can be one or more of Cyperus rotundus, Acorus calamus, Pennisetum rubrum, Pterocarpus davidianus, Zygophyllum serrata, and Alisma orientale.

[0058] The self-floating ecological floating bed was placed in the lake water sample. The main indicators of lake water quality were: TP 5mg / L, NH4+ -N25mg / L, COD 150mg / L, samples were taken at 0, 1, 2, 3, 4, 5, 6, 12, 24, 36, 48, 60 and 72 hours respectively, and the total phosphorus concentration of the water samples was measured. The specific results are shown in Table 2 below:

[0059] Table 2

[0060]

[0061] The measurement results showed that adsorption equilibrium was reached 48 hours after being placed in the ecological floating bed, and the final total phosphorus concentration of the water sample dropped to 0.09 mg / L.

[0062] In summary, the substrate prepared by the present invention is used in an ecological floating bed (such as Figure 4 ), compared with the existing ecological floating bed (such as Figure 3 ), the effective planting area of ​​aquatic plants has been greatly increased (such as Figure 5 ), the effective area of ​​the ecological floating bed with self-floating function and efficient phosphorus absorption matrix + planting basket is 60.99%, which is 4.32 times the effective area of ​​the existing ecological floating island + planting basket;

[0063] like Figure 1 and Figure 2 As shown in Figure 2, the thermodynamic adsorption characteristics of chitosan-calcium polymer / sodium alginate / calcium chloride @ melamine sponge (CC / SC@MF) prepared in Example 1 are compared with those of chitosan-calcium polymer @ melamine sponge (CC@MF) and calcium alginate @ melamine sponge (SC@MF). Figure 1 and Figure 2 As shown, the maximum phosphorus adsorption capacity of chitosan-calcium polymer / sodium alginate / calcium chloride@melamine sponge (CC / SC@MF) was 1797.2 times that of ceramsite, 2.26 times that of chitosan-calcium polymer@melamine sponge (CC@MF), and 4.25 times that of calcium alginate@melamine sponge (SC@MF). It also effectively increased the phosphorus adsorption rate, with CC / SC@MF achieving 1.21 times that of CC@MF and 4.16 times that of SC@MF, reaching adsorption equilibrium within 10 minutes.

[0064] like Figure 6 The figure shows the increase in plant phosphorus of six aquatic plants using three substrates over an 8-week period. As can be seen from the figure, six aquatic plants, including Cyperus rotundus, Acorus calamus, Pennisetum rutaecarpa, Pterocarpus davidianus, Zygophyllum sibiricum and Alisma orientale, were selected and compared using the substrate of the present invention and ceramsite and quartz sand. The increase in plant phosphorus using the substrate of the present invention generally exceeded the increase in plant phosphorus using ceramsite and quartz sand.

[0065] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a phosphorus-absorbing matrix with self-floating function, characterized in that: Chitosan-calcium polymer is prepared from discarded shells, impregnated and loaded onto a sponge fiber skeleton, and then cross-linked with a gel synthetic material at least twice to synthesize a hydrogel to obtain a matrix with self-floating function. The method specifically includes the following steps: (1) Chitosan-calcium polymer: Wash, crush, and sieve the discarded shells to obtain shell powder, mix it evenly with a strong alkaline solution, hydrothermally treat it at 120°C for 2-8 hours, cool it, and wash it with deionized water until the pH is constant to obtain chitosan-calcium polymer; (2) Primary cross-linking of the hydrogel-coated skeleton: dissolving chitosan-calcium polymer in acetic acid solution, immersing the sponge fiber in the above solution and ultrasonically treating it for 15 to 30 minutes, and then immersing it in the gel synthesis material solution and ultrasonically treating it for 30 to 60 minutes; (3) Secondary cross-linked hydrogel-coated skeleton: Using calcium chloride as the raw material, the sponge fiber soaked in the gel synthetic material is immersed in the calcium chloride solution for 12 to 24 hours, taken out and air-dried at room temperature to obtain a self-floating and efficient phosphorus-absorbing matrix.

2. The method for preparing a phosphorus-absorbing matrix with self-floating function according to claim 1, characterized in that: The gel synthetic material is one or more of chitosan, sodium alginate, starch, cyclodextrin, lignin and cellulose.

3. The method for preparing a phosphorus-absorbing matrix with self-floating function according to claim 1, characterized in that: The sponge fiber is one of wood cellulose or foamed plastic polymer sponge.

4. The method for preparing a phosphorus-absorbing matrix with self-floating function according to claim 1, characterized in that: In the step (1), the solid-to-liquid ratio of the chitin powder to the strong alkaline solution is 1:

20.

5. The method for preparing a phosphorus-absorbing matrix with self-floating function according to claim 1, characterized in that: The mass concentration of the acetic acid solution in step (2) is 5-8%; the concentration of the gel synthesis material solution is 0.6-1.2 g / L.

6. The method for preparing a phosphorus-absorbing matrix with self-floating function according to claim 1, characterized in that: The mass concentration of the calcium chloride solution in step (3) is 2-10%.

7. Application of a self-floating phosphorus-absorbing matrix in eutrophic water treatment, characterized in that: The substrate prepared by the preparation method according to any one of claims 1 to 6 and the aquatic plant roots are fixed in a planting basket with a tying rope, and then the planting baskets are connected into pieces with the tying rope to make a self-floating ecological floating bed that does not require frame support.

8. The use of a phosphorus-absorbing matrix with self-floating function in eutrophic water treatment according to claim 7, characterized in that: The aquatic plants are one or more of Cyperus rotundus, Acorus calamus, Pennisetum truncatum, Pterocarpus dasyphylla, Zygophyllum nobile and Alisma orientale.

9. The use of a phosphorus-absorbing matrix with self-floating function in eutrophic water treatment according to claim 7, characterized in that: The planting basket is a square or round plastic hydroponic planting basket.

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