Sodium alginate sealing semi-dry method calcium-based desulfurization ash slow-release material, preparation method and application

Abstract

This invention discloses a slow-release material for semi-dry calcium-based desulfurization ash encapsulated with sodium alginate, its preparation method, and its application, belonging to the field of material modification and preparation technology. This invention utilizes the synergistic effect of sodium alginate and semi-dry calcium-based desulfurization ash to simultaneously encapsulate and fix the ash, obtaining a slow-release material. This slows down the release rate of the semi-dry calcium-based desulfurization ash in water, avoiding drastic pH fluctuations due to strong alkalinity. It solves the water pollution problems caused by the direct application of traditional semi-dry calcium-based desulfurization ash, improves the material's mechanical stability and adsorption efficiency, effectively improves water quality, increases the survival rate of submerged plants, reduces dissolved nitrogen and phosphorus concentrations in water, and prevents eutrophication, achieving high efficiency, durability, and environmental friendliness in water remediation. The preparation method of this invention is simple to operate, low in cost, and has good application prospects.

Description

Technical Field

[0001] This invention relates to the field of semi-dry calcium-based desulfurization ash material modification and preparation technology, specifically to a sodium alginate-encapsulated semi-dry calcium-based desulfurization ash slow-release material, its preparation method, and its application. Background Technology

[0002] Semi-dry calcium-based desulfurization ash (SFGDA), a byproduct of industrial desulfurization, has a high calcium sulfite content. Its main components include CaSO3, CaSO4, Ca(OH)2, CaCO3, and CaCl2. Due to the presence of CaO and Ca(OH)2, SFGDA exhibits strong alkalinity, with a pH value typically around 12. SFGDA is usually in powder form, with fine and irregular particles, a wide particle size range, a large specific surface area, and high porosity. Although SFGDA itself has a settling effect on dissolved phosphorus, its direct application in water remediation can cause a sharp increase in water pH, leading to water pollution and limiting its effectiveness. Transforming SFGDA into an ecological remediation material represents a new and efficient way to reuse waste resources, aligning with the concepts of green development and a circular economy.

[0003] Sodium alginate (SA) is a natural anionic polysaccharide salt with good biocompatibility and biodegradability. Due to its rich functional organic groups, it is widely used in the medical field.

[0004] Sodium alginate reacts with Ca²⁺ + When there are divalent cations, they will react with Ca²⁺. + Ion exchange occurs, forming a cross-linked network structure. However, sodium alginate alone has insufficient mechanical adsorption properties in water quality remediation, which greatly limits its application. Therefore, in order to address the shortcomings of both, this invention attempts to make full use of the characteristics of sodium alginate to provide a slow-release material and preparation method that can solve the problem of a sharp increase in pH value in water quality remediation. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing a composite colloidal slow-release material for natural water body restoration, which uses modified SA to encapsulate SFGDA, enabling its slow release and long-lasting effectiveness, resulting in better ecological restoration effects and solving the aforementioned technical problems.

[0006] A method for preparing a semi-dry calcium-based desulfurization ash slow-release material encapsulated with sodium alginate includes the following steps S1-S4:

[0007] S1: Mix sodium alginate (SA) powder and semi-dry calcium-based desulfurization ash (SFGDA) powder in a mass ratio of (1-3):(3-1), place in a beaker and add an appropriate amount of deionized water.

[0008] S2: Heat and stir until the surface of the mixture shows adhesion. Slow down the stirring speed until the mixture shows aggregated flocculent form. Stop stirring, then cool and filter to remove excess water from the beaker to obtain a flocculated complex.

[0009] S3: After adding the flocculated complex to a syringe, it was dropped into an ice-water bath to obtain a preliminarily fixed SA-SFGDA colloidal sustained-release material.

[0010] S4: The SA-SFGDA colloidal slow-release material is dried at low temperature and filtered to obtain sodium alginate-encapsulated semi-dry calcium-based desulfurization ash slow-release material, which is then stored for later use.

[0011] Preferably, when the mass ratio of sodium alginate powder to semi-dry calcium-based desulfurization ash powder in S1 is 1:3, 1:2, 1:1, 2:1, or 3:1, the corresponding slow-release materials are SA-31, SA-21, SA-11, SA-12, and SA-13.

[0012] Preferably, the solid-liquid ratio of sodium alginate powder in water in S1 is 1:(50-100)g / mL.

[0013] Preferably, during the heating process in step S2, the reaction is controlled to be stable at 45-60°C, and the stirring speed is 150-200 rpm for 30-45 minutes. When the surface of the mixture shows adhesion, the stirring speed is gradually reduced to 10 rpm until stirring stops. When the mixture shows aggregated lumps, stirring is stopped, the temperature is lowered to 35°C, and the mixture is filtered to collect the flocculent matter.

[0014] Preferably, in step S3, the flocculated complex is added to the ice water bath at a rate of 1 drop per second.

[0015] Preferably, the viscosity of the SA powder in the S3 flocculated composite should be not less than 200 mPa. s.

[0016] Preferably, in step S4, the low-temperature drying involves placing the SA-SFGDA colloidal slow-release material in an oven and controlling the temperature at 35-45°C for 12-24 hours.

[0017] Preferably, the SA-SFGDA gel sustained-release material obtained in S4 is collected after being filtered through filter paper and stored in a blue-capped bottle at a temperature of 0-4°C.

[0018] The SA-fixed SFGDA slow-release material described in this invention has excellent applications in nitrogen and phosphorus removal during water remediation.

[0019] Compared with existing technologies, it has the following beneficial effects:

[0020] (1) This invention explores the mass ratio of sodium alginate to semi-dry calcium-based desulfurization ash and the precise stirring conditions, and simultaneously completes the encapsulation and fixation of semi-dry calcium-based desulfurization ash by sodium alginate. The prepared slow-release water remediation material achieves excellent beneficial effects in the water remediation process.

[0021] (2) The slow-release water remediation material prepared by the present invention, with the synergistic effect of sodium alginate (SA) and semi-dry calcium-based desulfurization ash (SFGDA), solves the problem of rapid increase in pH value during water remediation, can effectively capture pollutants such as nitrogen and phosphorus, improve water transparency and survival rate of submerged plants, improve the growth environment of submerged plants, optimize the state of water pollution, and thus ensure the high efficiency and long-term effectiveness of water remediation.

[0022] (3) This invention synthesizes slow-release water remediation material in a one-step process that is low-cost, simple, efficient and environmentally friendly. No additional chemical reagents are required during the preparation process, which achieves the beneficial effects of lower preparation cost and higher efficiency. Compared with existing gel materials, it can ensure the long-term effectiveness of SFGDA in water. Attached Figure Description

[0023] Figure 1 Flowchart of the preparation scheme for sodium alginate-encapsulated semi-dry calcium-based desulfurization ash slow-release material.

[0024] Figure 2 The images show a comparison of scanning electron microscope (SEM) images of the sodium alginate-encapsulated semi-dry calcium-based desulfurization ash slow-release material SA-31 before and after the adsorption experiment. Figure (a) is the SEM image of the sodium alginate-encapsulated semi-dry calcium-based desulfurization ash slow-release material SA-31 prepared in Example 1. Figure (b) is the SEM image of the sodium alginate-encapsulated semi-dry calcium-based desulfurization ash slow-release material SA-31 after adsorbing nitrogen and phosphorus in Example 1.

[0025] Figure 3 Comparison of Raman spectra before and after sodium alginate encapsulation of semi-dry calcium-based desulfurization ash slow-release material SA-31.

[0026] Figure 4 The X-ray photoelectron spectroscopy (XPS) of the sodium alginate-encapsulated semi-dry calcium-based desulfurization ash slow-release material SA-31 was compared before and after preparation. Figure (a) shows the full spectrum of the sodium alginate-encapsulated semi-dry calcium-based desulfurization ash slow-release material SA-31 prepared in Example 1, and Figure (b) shows the full spectrum of the sodium alginate-encapsulated semi-dry calcium-based desulfurization ash slow-release material SA-31 after adsorption of nitrogen and phosphorus in Experiment Example 1.

[0027] Figure 5 Figure 1 shows the high-resolution narrow spectrum of sodium alginate-encapsulated semi-dry calcium-based desulfurization ash slow-release material SA-31 before and after the adsorption experiment. Figure 2 shows the high-resolution narrow spectrum of sodium alginate-encapsulated semi-dry calcium-based desulfurization ash slow-release material SA-31 prepared in Example 1. Figure 3 shows the high-resolution narrow spectrum of sodium alginate-encapsulated semi-dry calcium-based desulfurization ash slow-release material SA-31 after adsorbing nitrogen and phosphorus in Example 1. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1

[0030] A method for preparing a slow-release material of semi-dry calcium-based desulfurization ash encapsulated with sodium alginate includes the following steps:

[0031] (1) Prepare SA-SFGDA colloidal sustained-release material. Mix sodium alginate powder with semi-dry calcium-based desulfurization ash powder in a mass ratio of 1:3, 1:2, 1:1, 2:1, 3:1. Put the mixture into a beaker and add an appropriate amount of deionized water. The solid-liquid ratio of sodium alginate powder to water is 1:(50-100)g / mL.

[0032] (2) Control the reaction to be stable at 45-60℃ and stir at 150-200 rpm for 30-45 minutes. When the mixture surface shows adhesion, slow down the stirring speed and the mixture will show aggregated lumps.

[0033] (3) Filter out excess water from the beaker to obtain a flocculated composite material. Add the flocculated composite material to a syringe and drip it into an ice water bath at a rate of 1 drop / second to obtain SA-SFGDA colloidal sustained-release material.

[0034] (4) Place the SA-SFGDA colloidal slow-release material in an oven and control the temperature at 35-45℃. Dry it at low temperature for 12-24 hours to obtain the SA-SFGDA corresponding SA-31, SA-21, SA-11, SA-12 and SA-13 slow-release materials respectively.

[0035] Comparative Example 1

[0036] The difference between this embodiment and Embodiment 1 is that a single semi-dry calcium-based desulfurization ash powder (SFGDA) is selected as the slow-release material.

[0037] Comparative Example 2

[0038] The difference between this embodiment and Embodiment 1 is that sodium alginate is replaced with carboxymethyl cellulose, and the mass ratio of carboxymethyl cellulose to semi-dry calcium-based desulfurization ash powder is 3:1, while other conditions remain unchanged.

[0039] Experimental Example 1

[0040] The slow-release materials SA-31, SA-21, SA-11, SA-12, and SA-13 prepared in Example 1 were uniformly placed into glass tanks at a dosage of 1 mg / L. 10 L of water sample from an artificial lake was added. After the water sample was allowed to settle, the total nitrogen (TN) and total phosphorus (TP) values ​​of the obtained water sample were measured. The total phosphorus and total nitrogen values ​​of the water body were measured 30 days after the addition of the materials. The difference between the two values ​​was used to represent the removal effect of the prepared materials on total nitrogen and total phosphorus in the water body, as shown in Table 1.

[0041] Table 1. Removal effect of slow-release materials on total nitrogen and total phosphorus in water.

[0042]

[0043] As shown in Table 1, compared with Comparative Examples 1 and 2, the nitrogen removal capacity of the SA-encapsulated SFGDA slow-release materials SA-31, SA-21, SA-11, SA-12, and SA-13 prepared by the present invention is 3-5 times higher than that of the single half-dry calcium-based desulfurization ash powder. As for the adsorption of phosphorus in water, the slow-release material SA-31 shows a strong adsorption capacity.

[0044] The sustained-release material SA-31 prepared in Example 1 and the sustained-release material SA-31 after adsorption of nitrogen and phosphorus in Experimental Example 1 were subjected to scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and high-resolution narrow-spectrum analysis, respectively. The results from the scanning electron microscopy were analyzed... Figure 2 It can be seen that the material has a porous structure and possesses good adsorption performance; the Raman spectra before and after the adsorption experiment show that... Figure 3 It can be seen that the Raman spectrum intensity was significantly enhanced before and after the experiment, indicating that the addition of sodium alginate increased the number of functional groups and strengthened the adsorption reaction in the water; and according to the X-ray photoelectron spectroscopy... Figure 4 It can be seen that, comparing before and after adsorption, characteristic peaks corresponding to N and P compounds appear, indicating that the SA-31 material has an adsorption effect on nitrogen and phosphorus compounds; high-resolution narrow-spectrum... Figure 5 It can be seen that after adsorption, complexes, nitrites, non-metallic nitrides, and hydrogen phosphates formed between -NH2 and metal ions appear on the surface of SA-31, proving the success of nitrogen and phosphorus adsorption.

[0045] Experiment Example 2

[0046] The slow-release materials SA-31, SA-21, SA-11, SA-12, and SA-13 prepared in Example 1 were uniformly placed in a glass tank at a dosage of 1 mg / L and added to 10 L of water sample from an artificial lake. The pH value and turbidity of the water sample were measured at two time points, 0 days and 30 days, to represent the effect of the prepared materials on water quality, as shown in Table 2.

[0047] Table 2. Changes in pH and water turbidity (NTU) before and after treatment with slow-release materials.

[0048]

[0049] According to Table 2, the SA-31, SA-21, SA-11, SA-12, and SA-13 slow-release materials prepared by this invention can maintain the pH value of water between 7.5 and 8.5 for a long time. After 30 days, the transparency of the water sample increased by about 2-9 NTU, thus improving the transparency of the water.

[0050] Experimental Example 3

[0051] The slow-release materials SA-31, SA-21, SA-11, SA-12, and SA-13 prepared in Example 1 were uniformly added into a glass tank at a dosage of 1 mg / L. 10 L of heavily polluted black and odorous water and sediments from the lower part of the water body were added to the tank. The growth of submerged plants in the glass tank was observed at different times, as shown in Table 3.

[0052] Table 3. Changes in the growth of submerged plants before and after treatment with slow-release materials prepared at different addition ratios.

[0053]

[0054] Experiment Example 4

[0055] The slow-release materials SA-31, SA-21, SA-11, SA-12, and SA-13 prepared in Example 1 were uniformly placed into a glass tank at a dosage of 1 mg / L. Submerged sediments were added to the tank, and the survival rate of submerged plants in the glass tank was observed after 30 days. The results are shown in Table 4.

[0056] Table 4. Survival rate of submerged plants before and after treatment with materials prepared with different addition ratios.

[0057]

[0058] Table 3 shows the effects of the prepared SA-31, SA-21, SA-11, SA-12, and SA-13 slow-release materials on the growth of submerged plants. After 30 days, the growth environment of submerged plants was significantly improved, the aquatic plant structure was optimized, and the water pollution status was further improved. Table 4 shows that the slow-release water remediation materials prepared in this invention can promote the growth and survival rate of submerged plants. Compared with the comparative example, the survival rate of submerged plants increased by 4-6%. Submerged plants play an irreplaceable role in aquatic ecosystems. They not only provide habitats and shelters for aquatic plants and animals but also increase dissolved oxygen in the water, purify water quality, and expand the effective living space for aquatic animals. Furthermore, the tender parts of submerged plants can provide food for aquatic animals, thereby improving the entire aquatic ecosystem. Therefore, improving the growth environment of submerged plants is of great significance for water quality remediation.

[0059] In summary, the slow-release material prepared by combining SA and SFGDA improves the mechanical strength and stability of the material, avoids the performance loss problem of traditional powder materials, and can effectively improve water transparency and increase the survival rate of submerged plants in the process of water remediation, thereby slowing down their release rate in the water. It can also further improve water quality and reduce dissolved nitrogen and phosphorus concentrations in synergy with submerged plants, providing a new technical approach for water environment remediation.

[0060] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for the preparation of sodium alginate encapsulated semi-dry process calcium based FGD ash slow release material, characterized by, Includes the following steps: S1: Mix sodium alginate powder and semi-dry calcium-based desulfurization ash powder evenly and dissolve in water; S2: Heat and stir until the mixture becomes aggregated and flocculent, then stop stirring and filter to obtain a flocculated complex; S3: The flocculated complex was dropped into an ice-water bath to obtain a pre-fixed colloidal slow-release material of SA-semi-dry calcium-based desulfurization ash. S4: The colloidal slow-release material of SA-semi-dry calcium-based desulfurization ash is dried at low temperature and filtered to obtain sodium alginate-sealed semi-dry calcium-based desulfurization ash slow-release material, which is then stored for later use.

2. The process for the preparation of sodium alginate encapsulated semi-dry calcium based FGD ash slow release material as claimed in claim 1 wherein, The mass ratio of sodium alginate powder and semi-dry calcium-based desulfurization ash powder in S1 is (1-3):(3-1), and the solid-liquid ratio of sodium alginate to water is 1:(50-100) g / mL.

3. The process for the preparation of sodium alginate encapsulated semi-dry calcium based FGD ash slow release material as claimed in claim 1 wherein, The heating temperature in S2 is 45-60℃, and the stirring speed is 150-200 rpm.

4. The process for the preparation of sodium alginate encapsulated semi-dry calcium based FGD ash slow release material as claimed in claim 1 wherein, The viscosity of the SA powder in the S3 flocculated composite is ≥ 200 mPa s.

5. The process for the preparation of sodium alginate encapsulated semi-dry calcium based FGD ash slow release material as claimed in claim 1 wherein, The low-temperature drying temperature in S4 is 35-45℃, and the storage temperature is 0-4℃.

6. The sodium alginate-encapsulated semi-dry calcium-based desulfurization ash slow-release material is prepared by the method according to any one of claims 1-5.

7. The application of the sodium alginate-encapsulated semi-dry calcium-based desulfurization ash slow-release material as described in claim 6 in water remediation.

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