Multilayer core-shell structure composite slow-release oxygen particles and preparation method thereof

Abstract

The application provides a multi-layer core-shell structure composite slow-release oxygen particle and a preparation method thereof, which comprises a three-layer structure of a weight-increasing core, an oxygen-releasing intermediate layer and a functional surface layer. The weight-increasing core is a high-density inorganic microsphere selected from one or more of alumina microspheres and silica microspheres, and the composition of the weight-increasing core is a binder and calcium peroxide, and the weight-increasing core has a long-acting slow-release oxygen function, wherein the binder is selected from one of sodium alginate, xanthan gum and guar gum; the composition of the outer shell layer is a binder, a porous adsorption material and a catalytic functional material, wherein the binder is physically crosslinked PVA, the adsorption functional material is selected from one or more of biochar powder, zeolite powder, diatomite and attapulgite, and the catalytic functional material is selected from one or more of iron-carbon powder, nano-iron powder and pyrite powder.

Description

Technical Field

[0001] This invention relates to the field of riverbed sediment treatment technology, specifically to a multi-layered core-shell structured composite slow-release oxygen particle and its preparation method. Background Technology

[0002] Oxygenation is a common method in riverbed sediment remediation. Its main principle is to increase the dissolved oxygen concentration in the overlying water, promoting the biochemical degradation and decomposition of various pollutants by aerobic microorganisms, thereby improving water quality. Adding oxygen-releasing agents is one common method. When added to the sediment, the oxygen produced directly acts on various sediments, creating an aerobic environment. The small oxygen bubbles allow for sufficient contact with the sediment and overlying water during diffusion, maximizing the oxygenation and water quality restoration effect. Oxygen-releasing agents are easy to add and have low construction and operating costs, making this method more convenient for river water remediation.

[0003] Calcium peroxide is the most commonly used oxygen-releasing agent because it has a low oxygen release rate and a long continuous release time, high oxygen content, and low cost. However, calcium peroxide is generally in powder form, and when added to water, it reacts fully with the water, resulting in an excessively high initial oxygen release that exceeds the water's saturation dissolved oxygen level and the requirements for oxidizing and degrading pollutants. The oxygen release lacks sustainability, necessitating repeated overdosing. Therefore, slow-release technology is needed to control its oxygen release rate.

[0004] Currently, the common method for preparing slow-release oxygen agents is the encapsulation method, which involves encapsulating calcium peroxide on various carriers. Commonly used carriers include cement, bentonite, sodium alginate, sodium humate, polyhydroxyalkanoates (PHA), and polyvinyl alcohol (PVA). Additionally, porous adsorbents such as activated carbon are often added to the encapsulation process with calcium peroxide. These porous adsorbents can adsorb various pollutants, enhancing the remediation effect on water quality. However, when porous adsorbents are mixed and encapsulated with calcium peroxide, only the surface layer exhibits efficient adsorption. Once the surface layer is saturated, the inner layers become difficult to adsorb, resulting in limited actual adsorption capacity, low utilization rate of the encapsulated porous adsorbents, and poor removal efficiency for pollutants such as ammonia nitrogen and total phosphorus in water. Summary of the Invention

[0005] In order to solve the above-mentioned problems in the prior art, the purpose of this invention is to provide a multi-layered core-shell structured composite slow-release oxygen particle and its preparation method, so as to overcome the above-mentioned shortcomings and deficiencies in the prior art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A multi-layered core-shell structured composite slow-release oxygen particle comprises a three-layer structure from the inside out: a weight-increasing core, an oxygen-releasing intermediate layer, and an outer shell.

[0008] Optionally, the diameter of the multi-layered core-shell structured composite slow-release oxygen particles is 8-20 mm.

[0009] Optionally, the weight-adding core is a high-density inorganic microsphere, which is selected from one or more of alumina microspheres and silica microspheres, and / or

[0010] The diameter of the high-density inorganic microspheres is 1-5 mm, more preferably 3-4 mm.

[0011] Optionally, the thickness of the oxygen-releasing intermediate layer is 5-10 mm, more preferably 6-8 mm.

[0012] Optionally, the oxygen-releasing intermediate layer is composed of a binder and calcium peroxide, wherein the binder is selected from sodium alginate, xanthan gum, and guar gum.

[0013] Optionally, the outer shell layer comprises an outer layer binder, a porous adsorbent material, and a catalytic functional material, wherein the outer layer binder is physically cross-linked PVA, the adsorbent functional material is selected from one or more of biochar powder, zeolite powder, diatomaceous earth, and attapulgite, and the catalytic functional material is selected from one or more of iron-carbon powder, nano-iron powder, and pyrite powder.

[0014] Optionally, the thickness of the outer shell layer is 1-5 mm, and more preferably 2-3 mm.

[0015] This invention also provides a method for preparing multi-layered core-shell structured composite slow-release oxygen particles, comprising the following steps:

[0016] Alumina and / or silica microspheres are used as weight-increasing cores and added together with oxygen-releasing binder and powdered calcium peroxide into a disc granulator. The disc is tilted at an angle of 45-55° and rotated at a speed of 32-45 rpm. Water is sprayed on the surface of the material and the granulation time is 10-30 minutes to obtain two-layer core-shell structured particles.

[0017] PVA particles are dissolved in deionized water at 80-95℃ to prepare a PVA aqueous solution with a concentration of 5-15 wt%.

[0018] The aforementioned two-layer core-shell structured particles, along with porous adsorption materials and catalytic functional materials, are added to a disc granulator with a disc inclination angle of 45-55° and a rotation speed of 32-45 rpm. PVA aqueous solution is sprayed onto the material surface, and the granulation time is 5-20 minutes to obtain three-layer core-shell structured slow-release oxygen particles.

[0019] The aforementioned three-layer core-shell structure slow-release oxygen particles are frozen at -20℃ for 8-12 hours, then thawed for 4 hours. This freeze-thaw cycle is repeated 2-4 times. Finally, the particles are dried at 60℃-70℃ for 5-10 hours to obtain the finished product.

[0020] Optionally, the diameter of the multi-layered core-shell structured composite slow-release oxygen particles is 8-20 mm, and / or

[0021] The diameter of the alumina and / or silica microspheres is 1-5 mm, more preferably 3-4 mm.

[0022] Optionally, the adhesive is selected from sodium alginate, xanthan gum, or guar gum.

[0023] By adopting the above technical solution, the present invention has the following beneficial effects:

[0024] 1. Strong adsorption capacity, with high removal efficiency for ammonia nitrogen and total phosphorus in water. Due to the multi-layer structure of this product, the oxygen-releasing calcium peroxide and adsorbent materials are not directly mixed together. The adsorbent material is located on the outermost layer of the particles, thus maximizing its adsorption function. After the product particles are added to the water, they can effectively adsorb ammonia nitrogen, organic pollutants, etc. Simultaneously, water can enter the middle layer through the outer layer and react with calcium peroxide. The generated oxygen is easily retained by the porous adsorbent material on the outer layer, forming a localized high-concentration aerobic condition. This creates a micro-bioreactor, allowing the adsorbed ammonia nitrogen and organic pollutants to be eliminated through aerobic reactions, thereby achieving the goal of efficiently removing pollutants such as ammonia nitrogen and total phosphorus.

[0025] 2. The outer adhesive is a physically cross-linked PVA coating layer, which can play a role in slow-release of oxygen. Furthermore, the cross-linked PVA is insoluble in water, so it will not cause organic matter to dissolve and cause pollution.

[0026] 3. With the addition of a weight-enhancing core, it can quickly settle onto the bottom sediment and is not easily washed away by water flow, thus fully leveraging the sediment's restorative properties. Detailed Implementation

[0027] The present invention will be further described below with reference to the embodiments.

[0028] Example 1:

[0029] 4 kg of calcium peroxide and 80 g of food-grade sodium alginate powder were stirred and mixed evenly. Then, together with 500 g of alumina microspheres with a diameter of 3 mm, they were added to a disc granulator. The disc was tilted at 52° and the rotation speed was 36 rpm. 650 g of water was sprayed on the surface of the material. The granulation time was 20 minutes to obtain two-layer core-shell structured particles with a diameter of about 8 mm.

[0030] PVA particles were dissolved in deionized water at 80-95℃ to prepare an 8wt% PVA aqueous solution. 1kg of biochar and 0.5kg of pyrite were stirred and mixed evenly, and then added together with the aforementioned two-layer core-shell structure particles into a disc granulator. The disc was tilted at 52° and rotated at 32rpm. 150g of the 8wt% PVA aqueous solution was sprayed onto the surface of the material. The granulation time was 5 minutes to obtain three-layer core-shell structure particles with a diameter of approximately 11mm.

[0031] The obtained particles were immediately frozen at -20°C for 8 hours, thawed for 4 hours, and this process was repeated 3 times. Then, they were dried at 60°C for 8 hours to obtain the finished product.

[0032] Example 2:

[0033] Mix 5 kg of calcium peroxide and 100 g of food-grade sodium alginate powder evenly, then add them together with 500 g of alumina microspheres with a diameter of 5 mm into a disc granulator. The disc is tilted at 52° and rotated at 36 rpm. Spray 800 g of water on the surface of the material and granulate for 25 minutes to obtain two-layer core-shell structured particles with a diameter of about 11 mm.

[0034] PVA particles were dissolved in deionized water at 80-95℃ to prepare an 8wt% PVA aqueous solution. 1kg of biochar and 0.5kg of pyrite were stirred and mixed evenly, and then added together with the aforementioned two-layer core-shell structure particles into a disc granulator. The disc was tilted at 52° and rotated at 32rpm. 150g of the 8wt% PVA aqueous solution was sprayed onto the surface of the material, and the granulation time was 5 minutes to obtain three-layer core-shell structure particles with a diameter of about 13mm.

[0035] The obtained particles were immediately frozen at -20°C for 8 hours, thawed for 4 hours, and this process was repeated 3 times. Then, they were dried at 60°C for 8 hours to obtain the finished product.

[0036] Example 3:

[0037] Mix 5 kg of calcium peroxide and 100 g of food-grade sodium alginate powder evenly, then add them together with 500 g of alumina microspheres with a diameter of 4 mm into a disc granulator. Set the disc to an inclination angle of 52° and a rotation speed of 36 rpm. Spray 800 g of water onto the material surface and granulate for 25 minutes to obtain two-layer core-shell structured particles with a diameter of approximately 10 mm.

[0038] PVA particles were dissolved in deionized water at 80-95℃ to prepare a 10wt% PVA aqueous solution. 1kg of biochar and 0.5kg of pyrite were stirred and mixed evenly, and then added together with the aforementioned two-layer core-shell structure particles into a disc granulator. The disc was tilted at 52° and rotated at 32rpm. 130g of the 10wt% PVA aqueous solution was sprayed onto the surface of the material. The granulation time was 6 minutes to obtain three-layer core-shell structure particles with a diameter of approximately 12mm.

[0039] The obtained particles were immediately frozen at -20°C for 8 hours, thawed for 4 hours, and this process was repeated 3 times. Then, they were dried at 60°C for 8 hours to obtain the finished product.

[0040] Example 4:

[0041] Mix 5 kg of calcium peroxide and 100 g of food-grade sodium alginate powder evenly, then add them together with 500 g of alumina microspheres with a diameter of 4 mm into a disc granulator. Set the disc to an inclination angle of 52° and a rotation speed of 36 rpm. Spray 800 g of water onto the material surface and granulate for 25 minutes to obtain two-layer core-shell structured particles with a diameter of approximately 10 mm.

[0042] PVA particles were dissolved in deionized water at 80-95℃ to prepare a 10wt% PVA aqueous solution. 1kg of 60-mesh zeolite powder and 0.5kg of pyrite were stirred and mixed evenly. Then, together with the aforementioned two-layer core-shell structured particles, they were added to a disc granulator with a disc inclination angle of 52° and a rotation speed of 32rpm. 120g of the 10wt% PVA aqueous solution was sprayed onto the surface of the material. The granulation time was 6 minutes to obtain three-layer core-shell structured particles with a diameter of approximately 12mm.

[0043] The obtained particles were immediately frozen at -20°C for 8 hours, thawed for 4 hours, and this process was repeated 3 times. Then, they were dried at 60°C for 8 hours to obtain the finished product.

[0044] Example 5:

[0045] Mix 5 kg of calcium peroxide and 100 g of food-grade sodium alginate powder evenly, then add them together with 500 g of alumina microspheres with a diameter of 4 mm into a disc granulator. Set the disc to an inclination angle of 52° and a rotation speed of 36 rpm. Spray 800 g of water onto the material surface and granulate for 25 minutes to obtain two-layer core-shell structured particles with a diameter of approximately 10 mm.

[0046] PVA particles were dissolved in deionized water at 80-95℃ to prepare a 10wt% PVA aqueous solution. 1kg of 60-mesh diatomaceous earth and 0.5kg of nano iron powder were stirred and mixed evenly. Then, together with the aforementioned two-layer core-shell structured particles, they were added to a disc granulator with a disc inclination angle of 52° and a rotation speed of 32rpm. 120g of the 10wt% PVA aqueous solution was sprayed onto the surface of the material, and the granulation time was 6 minutes to obtain three-layer core-shell structured particles with a diameter of approximately 12mm.

[0047] The obtained particles were immediately frozen at -20°C for 8 hours, thawed for 4 hours, and this process was repeated 3 times. Then, they were dried at 60°C for 8 hours to obtain the finished product.

[0048] Example for comparison:

[0049] PVA particles were dissolved in deionized water at 80-95℃ to prepare a 10wt% PVA aqueous solution.

[0050] 5 kg of calcium peroxide, 100 g of food-grade sodium alginate powder, 1 kg of biochar, and 0.5 kg of pyrite were mixed evenly. Then, they were added together with 500 g of alumina microspheres with a diameter of 4 mm into a disc granulator. The disc was tilted at 52° and rotated at 36 rpm. 800 g of 10 wt% PVA aqueous solution was sprayed onto the surface of the material. The granulation time was 25 minutes to obtain two-layer core-shell structured particles with a diameter of about 12 mm.

[0051] The obtained particles were immediately frozen at -20°C for 8 hours, thawed for 4 hours, and this process was repeated 3 times. Then, they were dried at 60°C for 8 hours to obtain the finished product.

[0052] Test results

[0053] Examples 1-5 and the control example of sediment remediation experiments: These were conducted in a 1m high, square, open water tank containing a 300mm thick layer of sediment covered with 400mm of water. The aforementioned slow-release oxygen particles were applied at a concentration of 1kg / m³. 2 The dosage was added to the surface of the sediment, and then the overlying water samples were taken periodically to test various water quality indicators such as ammonia nitrogen and total phosphorus. Ammonia nitrogen was determined by Nessler's reagent spectrophotometry, and total phosphorus was determined by ultraviolet spectrophotometry. The initial concentrations of ammonia nitrogen and total phosphorus in the overlying water of the sediment were 21.7 mg / L and 2.18 mg / L, respectively. Ten days after the addition of slow-release oxygen granules, the removal rates of ammonia nitrogen and total phosphorus in the example were higher than those in the control example, as shown in the table below:

[0054]

[0055] The technical solution of the present invention has the following beneficial effects:

[0056] 1. Strong adsorption capacity, with high removal efficiency for ammonia nitrogen and total phosphorus in water. Due to the multi-layer structure of this product, the oxygen-releasing calcium peroxide and adsorbent materials are not directly mixed together. The adsorbent material is located on the outermost layer of the particles, thus maximizing its adsorption function. After the product particles are added to the water, they can effectively adsorb ammonia nitrogen, organic pollutants, etc. Simultaneously, water can enter the middle layer through the outer layer and react with calcium peroxide. The generated oxygen is easily retained by the porous adsorbent material on the outer layer, forming a localized high-concentration aerobic condition. This creates a micro-bioreactor, allowing the adsorbed ammonia nitrogen and organic pollutants to be eliminated through aerobic reactions, thereby achieving the goal of efficiently removing pollutants such as ammonia nitrogen and total phosphorus.

[0057] 2. The outer adhesive is a physically cross-linked PVA coating layer, which can play a role in slow-release of oxygen. Furthermore, the cross-linked PVA is insoluble in water, so it will not cause organic matter to dissolve and cause pollution.

[0058] 3. With the addition of a weight-enhancing core, it can quickly settle onto the bottom sediment and is not easily washed away by water flow, thus fully leveraging the sediment's restorative properties.

[0059] The specific embodiments of the present invention have been described above, but the present invention is not limited thereto. Various changes can be made to the present invention as long as they do not depart from the spirit of the present invention.

Claims

1. A multi-layered core-shell structured composite slow-release oxygen particle, characterized in that, It includes a three-layer structure from the inside out: a weight-increasing core, an oxygen-releasing intermediate layer, and an outer shell. The weight-enhancing core is a high-density inorganic microsphere, which is selected from one or more of alumina microspheres and silica microspheres. The oxygen-releasing intermediate layer is composed of a binder and calcium peroxide, wherein the binder is selected from one of sodium alginate, xanthan gum, and guar gum. The outer shell layer comprises an outer layer binder, a porous adsorbent material, and a catalytic functional material. The outer layer binder is physically cross-linked PVA. The porous adsorbent material is selected from one or more of biochar powder, zeolite powder, diatomaceous earth, and attapulgite. The catalytic functional material is selected from one or more of iron-carbon powder, nano-iron powder, and pyrite powder.

2. The multi-layered core-shell structured composite slow-release oxygen particles according to claim 1, characterized in that, The diameter of the multi-layered core-shell structured composite slow-release oxygen particles is 8-20 mm.

3. The multi-layered core-shell structured composite slow-release oxygen particles according to claim 1, characterized in that, The diameter of the high-density inorganic microspheres is 1-5 mm.

4. The multi-layered core-shell structured composite slow-release oxygen particles according to claim 1, characterized in that, The diameter of the high-density inorganic microspheres is 3-4 mm.

5. The multi-layered core-shell structured composite slow-release oxygen particles according to claim 1, characterized in that, The thickness of the oxygen-releasing intermediate layer is 5-10 mm.

6. The multi-layered core-shell structured composite slow-release oxygen particles according to claim 1, characterized in that, The thickness of the oxygen-releasing intermediate layer is 6-8 mm.

7. The multi-layered core-shell structured composite slow-release oxygen particles according to claim 1, characterized in that, The thickness of the outer shell layer is 1-5 mm.

8. The multi-layered core-shell structured composite slow-release oxygen particles according to claim 1, characterized in that, The thickness of the outer shell layer is 2-3 mm.

9. A method for preparing multi-layered core-shell structured composite slow-release oxygen particles according to any one of claims 1 to 8, characterized in that, The process includes the following steps: Alumina and / or silica microspheres are used as the weight-increasing core, and added together with a binder selected from sodium alginate, xanthan gum, guar gum, and powdered calcium peroxide into a disc granulator. The disc is tilted at an angle of 45-55° and rotated at 32-45 rpm. Water is sprayed on the surface of the material, and the granulation time is 10-30 minutes to obtain two-layer core-shell structured particles. PVA particles are dissolved in deionized water at 80-95℃ to prepare a PVA aqueous solution with a concentration of 5-15 wt%. The aforementioned two-layer core-shell structured particles, along with porous adsorption materials and catalytic functional materials, are added to a disc granulator with a disc inclination angle of 45-55° and a rotation speed of 32-45 rpm. PVA aqueous solution is sprayed onto the material surface, and the granulation time is 5-20 minutes to obtain three-layer core-shell structured slow-release oxygen particles. The aforementioned three-layer core-shell structure slow-release oxygen particles are frozen at -20℃ for 8-12 hours, then thawed for 4 hours. This freeze-thaw cycle is repeated 2-4 times. Finally, the particles are dried at 60℃-70℃ for 5-10 hours to obtain the finished product.

10. The method for preparing multi-layered core-shell structured composite slow-release oxygen particles according to claim 9, characterized in that, The diameter of the multi-layered core-shell structured composite slow-release oxygen particles is 8-20 mm, and the diameter of the alumina and / or silica microspheres is 1-5 mm.

11. The method for preparing multi-layered core-shell structured composite slow-release oxygen particles according to claim 9, characterized in that, The diameter of the multi-layered core-shell structured composite slow-release oxygen particles is 8-20 mm, and the diameter of the alumina and / or silica microspheres is 3-4 mm.

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