Sodium alginate sealed semi-dry calcium-based desulfurized fly ash slow-release material as well as preparation method and application thereof

Abstract

The invention discloses a sodium alginate sealed semi-dry calcium-based desulfurized fly ash slow-release material as well as a preparation method and application thereof, and belongs to the technical field of material modification preparation. Through the synergistic effect of the sodium alginate and the desulfurized gypsum, encapsulation and fixation of the desulfurized gypsum by the sodium alginate are synchronously completed to obtain the sustained-release material, the release speed of the SFGDA in a water body is delayed, the situation that the pH is strongly alkaline and violently fluctuates is avoided, the problems of water body pollution and the like caused by direct application of traditional SFGDA are solved, and the preparation method is simple and convenient to operate. The mechanical stability and adsorption efficiency of the material are improved, the water quality of a water body is effectively improved, the survival rate of submerged plants is increased, the concentration of nitrogen and phosphorus dissolved in the water body is reduced, the eutrophication phenomenon of the water body is prevented, and high efficiency, durability and environmental friendliness of water body remediation are achieved. The preparation method disclosed by the invention is simple to operate and low in cost, and has a good application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of SFGDA material modification and preparation, and specifically relates to a sodium alginate-sealed semi-dry calcium-based desulfurization ash slow-release material, a preparation method thereof, and an application thereof. Background Art

[0002] Semi-dry calcium-based desulfurization ash (SFGDA), as a by-product of industrial desulfurization, has a high calcium sulfite content, and its main components include CaSO 3 , CaSO 4 , Ca(OH)2, CaCO 3 , and CaCl 2 etc. Due to the presence of CaO and Ca(OH)2, SFGDA exhibits strong alkalinity, and the pH value is usually around 12. SFGDA is usually in powder form, with fine and irregular particles, a wide particle size range, a large specific surface area, and a high porosity. Although SFGDA itself has a sedimentation effect on dissolved phosphorus, directly using it for water body restoration will cause the pH value of the water body to rise sharply, resulting in water pollution and limiting its application effect. Converting SFGDA into an ecological restoration material has become a new way for the efficient reuse of waste resources, which conforms to the concept of green development and circular economy.

[0003] Sodium alginate (SA) is a natural anionic polysaccharide salt with good biocompatibility and biodegradability, and is widely used in the medical field due to its rich functional organic groups. When sodium alginate encounters divalent cations such as Ca 2 +, it will undergo ion exchange with Ca 2 + to form a cross-linked network structure. However, pure sodium alginate has insufficient mechanical adsorption performance in water quality restoration, which greatly limits the application of sodium alginate. Therefore, aiming at the deficiencies of the two, the present invention attempts to make full use of the characteristics of sodium alginate to provide a slow-release material and a preparation method that can solve the problem of sharp increase in pH value in water quality restoration. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides a preparation method of a modified SA-sealed SFGDA composite colloid slow-release material for natural water body restoration. Using SA to encapsulate SFGDA enables it to be slowly released and the performance to be long-lasting and effective, with a good ecological restoration effect, and solves the above technical problems.

[0005] A preparation method of a sodium alginate-sealed semi-dry calcium-based desulfurization ash slow-release material includes the following steps S1-S4:

[0006] S1: Mix sodium alginate (SA) powder and desulfurized gypsum (SFGDA) powder in a mass ratio of (1-3):(3-1), put them into a beaker and add appropriate amount of deionized water;

[0007] S2: heating and stirring until the mixture surface shows adhesion, slowing down the stirring speed until the mixture appears to be aggregated and flocculent, then cooling and filtering, filtering out excess water in the beaker to obtain a flocculent composite;

[0008] S3: Add the flocculent complex into a syringe and then drop it into an ice water bath to obtain a preliminarily fixed SA-SFGDA colloidal sustained-release material;

[0009] S4: Dry the SA-SFGDA colloidal sustained-release material at low temperature, filter it, and obtain the sodium alginate sealed semi-dry calcium-based desulfurization ash sustained-release material, which is stored for future use.

[0010] Preferably, when the mass ratio of the sodium alginate powder to the desulfurized gypsum powder in S1 is 1:3, 1:2, 1:1, 2:1, 3:1, the corresponding sustained-release materials obtained are SA-31, SA-21, SA-11, SA-12, and SA-13.

[0011] Preferably, the solid-liquid ratio of the sodium alginate powder in water in S1 is 1: (50-100) g / mL.

[0012] Preferably, during heating in S2, the reaction is controlled to be stable at 45-60°C, the rotation speed is 150-200 rpm / s and stirred for 30-45 min, and adhesion occurs on the surface of the mixture. The stirring speed is gradually slowed down at a speed of 10 rpm / s until the stirring is stopped. When the mixture appears to be aggregated lumps, the stirring is stopped, the temperature is lowered to 35°C, and the flocs are collected by filtration.

[0013] Preferably, in S3, the flocculent composite is dripped into the ice water bath at a speed of 1 drop / second.

[0014] Preferably, the viscosity of the SA powder in the S3 flocculent composite should be no less than 200 mPa.s.

[0015] Preferably, the low temperature drying in S4 is to place the SA-SFGDA colloidal sustained-release material into an oven and control the temperature at 35-45° C., and perform low temperature drying for 12-24 hours.

[0016] 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 with the humidity maintained at 0-4°C.

[0017] The SA-fixed SFGDA slow-release material of the present invention has good application in nitrogen and phosphorus removal during water body restoration.

[0018] Compared with the prior art, the following beneficial effects are achieved:

[0019] (1) Through the exploration of the mass ratio of sodium alginate to desulfurized gypsum and accurate stirring conditions, and the simultaneous encapsulation and fixation of desulfurized gypsum by sodium alginate, the prepared slow-release water body repair material has achieved excellent beneficial effects during the water body repair process.

[0020] (2) For the slow-release water body repair material prepared by the present invention, due to the synergistic effect of sodium alginate (SA) and desulfurized gypsum (SFGDA), the problem of sharp increase in pH value during the water body repair process is solved. It can effectively capture pollutants such as nitrogen and phosphorus, improve the transparency of the water body and the survival rate of submerged plants, improve the growth environment of submerged plants, optimize the state of water body pollution, and thus ensure the high efficiency and durability of water body repair.

[0021] (3) The present invention synthesizes the slow-release water body repair material by a low-cost, simplified, efficient and environmentally friendly one-step method. No additional chemical reagents are required during the preparation process, achieving the beneficial effects of lower preparation cost and higher efficiency. Compared with the existing gel materials, it can ensure the long-term effectiveness of SFGDA in the water body. Description of the Drawings

[0022] Figure 1 It is a flow chart of the preparation scheme of the slow-release material for encapsulating semi-dry calcium-based desulfurized ash with sodium alginate.

[0023] Figure 2 It is a comparative analysis diagram of scanning electron microscope images before and after the adsorption experiment of the slow-release material SA-31 for encapsulating semi-dry calcium-based desulfurized ash with sodium alginate. Figure (a) is the SEM spectrum of the slow-release material SA-31 for encapsulating semi-dry calcium-based desulfurized ash with sodium alginate prepared in Example 1, and Figure (b) is the SEM spectrum of the slow-release material SA-31 for encapsulating semi-dry calcium-based desulfurized ash with sodium alginate after adsorbing nitrogen and phosphorus in Experimental Example 1.

[0024] Figure 3 It is a comparative diagram of Raman spectra before and after of the slow-release material SA-31 for encapsulating semi-dry calcium-based desulfurized ash with sodium alginate.

[0025] Figure 4 It is a comparative analysis of X-ray photoelectron spectra before and after of the slow-release material SA-31 for encapsulating semi-dry calcium-based desulfurized ash with sodium alginate. Figure (a) is the full-spectrum scan of the slow-release material SA-31 for encapsulating semi-dry calcium-based desulfurized ash with sodium alginate prepared in Example 1, and Figure (b) is the full-spectrum scan of the slow-release material SA-31 for encapsulating semi-dry calcium-based desulfurized ash with sodium alginate after adsorbing nitrogen and phosphorus in Experimental Example 1.

[0026] Figure 5High-resolution narrow-spectrum diagrams before and after the adsorption experiment of the alginate-encapsulated semi-dry calcium-based desulfurization ash slow-release material SA-31 prepared in Example 1. Figure (a) is the high-resolution narrow spectrum of the alginate-encapsulated semi-dry calcium-based desulfurization ash slow-release material SA-31 prepared in Example 1, and Figure (b) is the high-resolution narrow spectrum of the alginate-encapsulated semi-dry calcium-based desulfurization ash slow-release material SA-31 after adsorbing nitrogen and phosphorus in Experimental Example 1. Detailed implementation manners

[0027] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0028] Example 1

[0029] A preparation method of an alginate-encapsulated semi-dry calcium-based desulfurization ash slow-release material includes the following steps:

[0030] (1) Prepare the SA-SFGDA colloid slow-release material. Mix the mixture of sodium alginate powder and desulfurization gypsum powder with a total mass of 4 g evenly according to the mass ratios of 1:3, 1:2, 1:1, 2:1, and 3:1, put it into a beaker, and add an appropriate amount of deionized water. Among them, the solid-liquid ratio of sodium alginate powder to water is 1:(50 - 100) g / mL.

[0031] (2) Control the reaction temperature at 45 - 60 °C, stir at a speed of 150 - 200 rpm / s for 30 - 45 min. When a bonding phenomenon appears on the surface of the mixture, slow down the stirring speed, and the mixture presents an aggregated block shape.

[0032] (3) Filter out the excess water in the beaker to obtain a flocculent composite material. Add the flocculent composite material to a syringe and drop it into an ice-water bath pot at a speed of 1 drop / second to obtain the SA-SFGDA colloid slow-release material.

[0033] (4) Put the SA-SFGDA colloid slow-release material into an oven, control the temperature at 35 - 45 °C, and dry it at a low temperature for 12 - 24 hours to obtain the SA-31, SA-21, SA-11, SA-12, and SA-13 slow-release materials corresponding to SA-SFGDA respectively.

[0034] Comparative Example 1

[0035] The difference between this example and Example 1 is that a single desulfurization gypsum powder (SFGDA) is selected as the slow-release material.

[0036] Comparative Example 2

[0037] In this example, the difference from Example 1 is that sodium alginate is replaced by carboxymethyl cellulose, and the mass ratio of carboxymethyl cellulose to desulfurized gypsum powder is 3:1 for mixing, with other conditions remaining unchanged.

[0038] Experimental Example 1

[0039] The SA-31, SA-21, SA-11, SA-12, and SA-13 slow-release materials prepared in Example 1 were evenly placed into glass cylinders respectively, with a dosage of 1 mg / L, and 10 L of water samples from an artificial lake were added. After the water samples were allowed to settle statically, the total nitrogen (TN) and total phosphorus (TP) values of the obtained water samples were measured. After 30 days of adding the materials, the total phosphorus and total nitrogen values of the water body were measured, and the removal effects of the prepared materials on total nitrogen and total phosphorus in the water body were represented by the differences between the two times, as shown in Table 1.

[0040] Table 1 Removal effects of slow-release materials on total nitrogen and total phosphorus in water body.

[0041] Material TN Removal Amount (mg / L) TP Removal Amount (mg / L) SA31 3.1478 0.0689 SA21 1.987 0.0023 SA11 2.631 0.0389 SA12 4.082 0.0012 SA13 4.793 0.0189 Comparative Example 1 0.864 0.0026 Comparative Example 2 1.296 0.0034

[0042] According to Table 1, compared with Comparative Examples 1 and 2, the nitrogen removal amounts of the SA-sealed SFGDA slow-release materials SA-31, SA-21, SA-11, SA-12, and SA-13 prepared by the present invention are 3 - 5 times higher than those of single desulfurized gypsum powder. For the adsorption of phosphorus in the water body, the slow-release material SA-31 shows strong adsorption ability.

[0043] The slow-release material SA-31 prepared in Example 1 and the slow-release material SA-31 after adsorbing nitrogen and phosphorus in Experimental Example 1 were respectively subjected to scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and high-resolution narrow-spectrum analysis. From the results of scanning electron microscopy Figure 2 it can be seen that the material has a porous structure and has good adsorption performance; from the Raman spectra before and after the adsorption experiment Figure 3 it can be seen that by comparing before and after the experiment, the intensity of the Raman spectrum is significantly enhanced, indicating that the addition of sodium alginate increases the number of functional groups and strengthens the adsorption reaction with the water body; and according to the X-ray photoelectron spectroscopy Figure 4 it can be seen that by 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; from the high-resolution narrow spectrum Figure 5 it can be seen that after adsorption, complexes, nitrites, non-metal nitrides, and hydrogen phosphate substances formed between -NH 2 on the surface of SA-31 and metal ions are present, proving the success of nitrogen and phosphorus adsorption.

[0044] Experimental Example 2

[0045] The SA-31, SA-21, SA-11, SA-12, and SA-13 sustained-release materials prepared in Example 1 were evenly placed in a glass cylinder, with a dosage of 1 mg / L, and the water samples from a 10-L artificial lake were added. The pH value and water turbidity of the water samples were measured at two time points: 0 day and 30 days, to represent the impact of the prepared materials on water quality, as shown in Table 2.

[0046] Table 2. Changes in pH value and water turbidity (NTU) before and after treatment with the sustained-release materials.

[0047]

[0048] According to Table 2, it can be seen that the SA-31, SA-21, SA-11, SA-12, and SA-13 sustained-release materials prepared by the present invention can maintain the pH value of the water body between 7.5 and 8.5 for a long time. After 30 days, the transparency of the water body in the water sample increased by about 2 - 9 NTU, improving the water body transparency.

[0049] Experimental Example 3

[0050] The SA-31, SA-21, SA-11, SA-12, and SA-13) sustained-release materials prepared in Example 1 were evenly put into a glass cylinder, with a dosage of 1 mg / L. 10 L of severely polluted black and odorous water body and the sediment at the lower part of its water area were added to the cylinder. The growth of submerged plants in the glass cylinder was observed at different times, as shown in Table 3.

[0051] Table 3. Changes in the growth of submerged plants before and after treatment with the sustained-release materials prepared at different addition ratios.

[0052]

[0053] Experimental Example 4

[0054] The SA-31, SA-21, SA-11, SA-12, and SA-13 sustained-release materials prepared in Example 1 were evenly placed in a glass cylinder, with a dosage of 1 mg / L. The sediment at the lower part of the water area was added to the cylinder. The survival rate of submerged plants in the glass cylinder was observed after 30 days, and the statistics are shown in Table 4.

[0055] Table 4. Survival rates of submerged plants before and after treatment with the materials prepared at different addition ratios.

[0056] Material Comparative Example 1 Comparative Example 2 SA31 SA21 SA11 SA12 SA13 30-day Survival Rate 71％ 76％ 91％ 81％ 86％ 77％ 79％

[0057] From Table 3, the prepared SA-31, SA-21, SA-11, SA-12, and SA-13 slow-release materials were used to study their effects on the growth of submerged plants. After 30 days, the growth environment of the submerged plants was significantly improved, optimizing the aquatic plant structure and further improving the water pollution status. According to Table 4, the slow-release water body repair material prepared by the present invention can promote the growth and survival rate of submerged plants. Compared with the comparative example, the survival rate of submerged plants has increased by 4-6%. Submerged plants have an irreplaceable position in the aquatic ecosystem. Submerged plants not only provide living habitats and hiding places for aquatic animals and plants, but also increase the dissolved oxygen in the water, purify the water quality, and expand the effective living space for aquatic animals. At the same time, the tender parts of submerged plants can be fed on by aquatic animals, thus improving the entire aquatic ecosystem. Therefore, improving the growth environment of submerged plants is of great significance for water quality restoration.

[0058] In summary, the slow-release material prepared by combining SA with SFGDA improves the mechanical strength and stability of the material, avoids the problem of efficacy loss of traditional powder materials, and can effectively improve the water transparency and increase the survival rate of submerged plants during the water body repair process, thereby delaying its release rate in water. It can also further improve the water quality under the cooperation of submerged plants, reduce the concentration of dissolved nitrogen and phosphorus, and provide a new technical approach for water environment restoration.

[0059] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a sodium alginate-sealed semi-dry calcium-based desulfurization ash slow-release material, characterized in that: The steps include: S1: Mix sodium alginate powder and desulfurized gypsum powder evenly and dissolve them in water; S2: heating and stirring the mixture until it becomes flocculent, stopping the stirring, and filtering to obtain a flocculent composite; S3: dropping the flocculent complex into an ice water bath to obtain a colloidal sustained-release material of SA-SFGDA that is initially fixed; S4: The colloidal sustained-release material of SA-SFGDA is dried and filtered at low temperature to obtain a sodium alginate sealed semi-dry calcium-based desulfurization ash sustained-release material, which is stored for future use.

2. The method for preparing the sodium alginate-sealed semi-dry calcium-based desulfurization ash slow-release material according to claim 1, characterized in that: The mass ratio of the sodium alginate powder and the desulfurized gypsum 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 method for preparing the sodium alginate-sealed semi-dry calcium-based desulfurization ash slow-release material according to claim 1, characterized in that: The heating temperature in S2 is 45-60° C., and the stirring speed is 150-200 rpm / s.

4. The method for preparing the sodium alginate-sealed semi-dry calcium-based desulfurization ash slow-release material according to claim 1, characterized in that: The viscosity of the SA powder in the S3 flocculent composite is ≥200 mPa.s.

5. The method for preparing the sodium alginate sealed semi-dry calcium-based desulfurization ash slow-release material according to claim 1, characterized in that: The temperature of low temperature drying in S4 is 35-45°C, and the temperature of storage is 0-4°C.

6. The method described in any one of claims 1 to 5 is used to prepare a sodium alginate sealed semi-dry calcium-based desulfurization ash slow-release material.

7. Application of the sodium alginate sealed semi-dry calcium-based desulfurization ash slow-release material as described in claim 6 in water body restoration.

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