Multi-pH segment slow-release alkaline buffer material, and preparation method and application thereof

Abstract

This invention relates to the field of acidification environment remediation technology, and discloses a multi-pH-segment slow-release alkaline buffer material, its preparation method, and its application. The alkaline buffer material comprises a slow-release framework and a pH buffering agent encapsulated therein; wherein the slow-release framework is composed of an organic molecular skeleton and terpene polymers / hydrated minerals; the pH buffering agent comprises alkaline materials and optionally acidic materials, used to provide multi-segment pH buffering capacity in acidified environments. The multi-pH-segment slow-release alkaline buffer material provided by this invention possesses the characteristics of adjustable multi-pH segments, long-lasting slow release, and environmental friendliness, and can precisely stabilize pH according to different acidification scenarios. It is directly applied in solid block form, simplifying construction and maintenance, and achieving efficient, long-lasting, and green passive remediation of acidified environments.

Description

Technical Field

[0001] This invention relates to the field of acidification environment improvement technology, specifically to a multi-pH-segment slow-release alkaline buffer material, its preparation method, and its application. Background Technology

[0003] Currently, the treatment of AMD mainly relies on chemical precipitation, which involves adding alkaline materials such as quicklime, hydrated lime, limestone, and caustic soda, or alkaline sulfiding materials such as sodium sulfide and sodium hydrosulfide, depending on the OH- ions they provide. - or S 2- Raising the pH of water bodies causes heavy metal ions to precipitate. While this method has advantages such as low remediation cost and mature technology, it requires the construction of fixed treatment sites, relies on electricity and continuous manual operation, and has rigid treatment capacity, unable to flexibly adapt to water volume fluctuations, and lacks long-term slow-release function. For acidified farmland, the mainstream improvement method is to apply lime-like substances (mainly CaO) to the soil surface. Although simple and economical to operate, its improvement effect is mostly limited to the soil surface, with poor effect on deep soil. Frequent application is required to maintain the remediation effect, and long-term use can easily lead to soil compaction, decreased aggregate stability, and even repeated soil acidification and cation imbalance.

[0004] In summary, existing acidification remediation technologies generally suffer from problems such as reliance on continuous human intervention, lack of long-term effectiveness and adaptability, and potential secondary adverse effects. Therefore, there is an urgent need to develop a passive remediation material that combines long-term sustained release, multi-pH adjustment, simple construction, environmental friendliness, and applicability to various acidification scenarios to fill the gaps in existing technologies. Summary of the Invention

[0005] This invention aims to overcome the technical defects of existing acidification environmental remediation technologies, such as the inability to provide long-term sustained release, the limited pH adjustment range, reliance on continuous human intervention, and the potential for secondary environmental problems.

[0006] To achieve the above objectives, a first aspect of the present invention provides a multi-pH-segment slow-release alkaline buffer material, comprising a slow-release framework and a pH buffering agent encapsulated therein; wherein the slow-release framework is composed of an organic molecular skeleton and terpene polymers / hydrated minerals; and the pH buffering agent comprises an alkaline material and optionally an acidic material, for providing multi-segment pH buffering capacity in acidified environments.

[0007] A second aspect of the present invention provides a method for preparing the multi-pH-segment slow-release alkaline buffer material described in the first aspect above. This method utilizes the substances in the multi-pH-segment slow-release alkaline buffer material described in the first aspect above and includes the following steps: (1) The soil polymer / hydrated minerals, organic molecular framework and water are mixed in the first stage to form a slow-release framework; (2) The sustained-release framework is mixed with the alkaline material for a second time of not less than 30 minutes to obtain mixture I; (3) When the required sustained-release pH range is 7 ≤ pH < 10, the mixture I is mixed with the acidic material for a third time to obtain mixture II; When the required sustained-release pH range is 10 ≤ pH < 11.5, then mixture I is directly used as mixture II, and the acidic material is not added; (4) The mixture II is cured for 24-36 hours to obtain a multi-pH slow-release alkaline buffer material.

[0008] The third aspect of the present invention provides the application of the multi-pH-segment slow-release alkaline buffer material described in the first aspect above in the improvement of acidified environments, wherein the acidified environment includes at least one of acidic mine water inflow, acidified surface water / groundwater, and acidified farmland.

[0009] Compared with the prior art, the present invention has at least the following beneficial effects: (1) The unique organic-inorganic composite slow-release framework of the multi-pH-segment slow-release alkaline buffer material provided by the present invention can effectively control the release rate of alkaline components, realize long-term and stable pH adjustment capability, overcome the disadvantage of the traditional technology that requires frequent addition, and the material service life can reach 1 to 3 years. (2) By flexibly adjusting the types and ratios of acidic and alkaline materials, the present invention can enable the materials to provide and stabilize in different pH buffer ranges (such as pH 7-8, 8-9, 9-10, 11-12) in the environment, thus achieving precise adaptation to multiple types and different degrees of acidification environments. (3) The multi-pH slow-release alkaline buffer material provided by the present invention is used in the form of solid block, which is simple to construct and suitable for various passive repair scenarios such as infiltration dams, reaction ponds, and farmland ditches. It does not require continuous energy and manual maintenance, which greatly reduces the operation and maintenance costs. (4) The main components of the multi-pH slow-release alkaline buffer material provided by the present invention are environmentally friendly minerals and organic frameworks. It will not introduce harmful substances during use and has green and environmentally friendly characteristics. At the same time, it has a certain compressive strength (3.5-8.7MPa) after hardening and can maintain good physical stability in complex water and soil environments. Detailed Implementation

[0010] The endpoints and any values ​​of the ranges disclosed herein 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 the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0011] As previously stated, a first aspect of the present invention provides a multi-pH-segment slow-release alkaline buffer material, comprising a slow-release framework and a pH buffering agent encapsulated therein; wherein the slow-release framework is composed of an organic molecular skeleton and terpenoids / hydrated minerals; and the pH buffering agent comprises an alkaline material and optionally an acidic material, for providing multi-segment pH buffering capacity in an acidified environment.

[0012] In a preferred embodiment, the compressive strength of the multi-pH-segment slow-release alkaline buffer material is 3.5-8.7 MPa.

[0013] In a preferred embodiment, the organic molecular backbone is selected from at least two of polyacrylic acid, carboxymethyl cellulose, hydroxypropyl methyl cellulose, N-vinylcaprolactam, hydroxyethyl cellulose, lignocellulose, lauric acid, palmitic acid, and stearic acid.

[0014] According to a preferred embodiment, the soil polymer / hydrated mineral is selected from at least two of calcium silicate, calcium aluminate, calcium carbonate, calcium chloride, calcium sulfate, metakaolin, kaolin, and bentonite.

[0015] Preferably, the bentonite is calcium-based bentonite.

[0016] In a preferred embodiment, the metakaolin and / or the white clay are calcined and have an average volume diameter of 10-30 μm.

[0017] More preferably, the calcination treatment of the metakaolin and / or the white clay includes calcination at 600-900℃ for 2-3 hours.

[0018] In a preferred embodiment, the alkaline material is selected from at least one of calcium hydroxide, sodium hydroxide, and sodium silicate.

[0019] Preferably, the pH buffer comprises both alkaline and acidic materials.

[0020] Preferably, the acidic material is selected from at least one of formic acid, acetic acid, oxalic acid, and citric acid.

[0021] According to a preferred embodiment, the modulus of the sodium silicate is 1.

[0022] In a preferred embodiment, the multi-pH-segment slow-release alkaline buffer material of the present invention further contains water, and the mass fraction of each component, based on the total mass of the material, is as follows: The soil polymer / hydrated minerals: 30-50 wt%; The organic molecular skeleton: 0.2-1.2 wt%; The pH buffer: 15-36 wt%; Water content: 20-35 wt%.

[0023] Preferably, the content ratio of the acidic material to the alkaline material is adjusted so that the buffering range that the multi-pH-segment slow-release alkaline buffer material can achieve is different.

[0024] More preferably, the buffering range that the multi-pH-segment slow-release alkaline buffer material can achieve is 7≤pH≤11.5.

[0025] More preferably, the buffering range that the multi-pH-segment slow-release alkaline buffer material can achieve is 7≤pH≤10.

[0026] As mentioned above, a second aspect of the present invention provides a method for preparing the multi-pH-segment slow-release alkaline buffer material described in the first aspect. This method utilizes the substances in the multi-pH-segment slow-release alkaline buffer material described in the first aspect and includes the following steps: (1) The soil polymer / hydrated minerals, organic molecular framework and water are mixed in the first stage to form a slow-release framework; (2) The sustained-release framework is mixed with the alkaline material for a second time of not less than 30 minutes to obtain mixture I; (3) When the required sustained-release pH range is 7 ≤ pH < 10, the mixture I is mixed with the acidic material for a third time to obtain mixture II; When the required sustained-release pH range is 10 ≤ pH < 11.5, then mixture I is directly used as mixture II, and the acidic material is not added; (4) The mixture II is cured for 24-36 hours to obtain a multi-pH slow-release alkaline buffer material.

[0027] Preferably, the alkaline material and the acidic material together constitute a pH buffer, and the mass fraction of each component, based on the total mass of the multi-pH-segment slow-release alkaline buffer material, is as follows: The soil polymer / hydrated minerals: 30-50 wt%; The organic molecular skeleton: 0.2-1.2 wt%; The pH buffer: 15-36 wt%; Water content: 20-35 wt%.

[0028] More preferably, the desired sustained-release pH range can be adjusted by changing the ratio of acidic to alkaline materials in the pH buffer. Specifically, when the desired sustained-release pH range is 7 ≤ pH < 8, the mass weight ratio of acidic to alkaline materials in the multi-pH-segment sustained-release alkaline buffer is 1:1.30-1.69; when the desired sustained-release pH range is 8 ≤ pH < 9, the mass weight ratio of acidic to alkaline materials in the multi-pH-segment sustained-release alkaline buffer is 1:1.70-2.09; when the desired sustained-release pH range is 9 ≤ pH < 10, the mass weight ratio of acidic to alkaline materials in the multi-pH-segment sustained-release alkaline buffer is 1:2.10-2.49; and when the desired sustained-release pH range is 10 ≤ pH < 11.5, no acidic materials need to be added to the multi-pH-segment sustained-release alkaline buffer.

[0029] In a preferred embodiment, in step (1), the first mixing is carried out under stirring conditions, and at least the following conditions are met: the rotation speed is 30-60 rpm, the temperature is 10-35℃, and the time is 30-50 min.

[0030] In a preferred embodiment, in step (2), the second mixing is carried out under stirring conditions, and at least the following conditions are met: the rotation speed is 30-50 rpm, the temperature is 10-35℃, and the time is 30-50 min.

[0031] In a preferred embodiment, in step (3), the third mixing is carried out under stirring conditions, and at least the following conditions are met: the rotation speed is 30-50 rpm, the temperature is 10-35℃, and the time is 10-30 min.

[0032] According to a preferred embodiment, in step (4), the maintenance operation and conditions include: S1, spraying water to keep the mixture II moist and prevent rapid water loss causing cracking; S2. Covering reduces the reaction between alkaline substances in the material and carbon dioxide in the air under humid conditions; S3. Maintain a temperature of 10-35℃ to allow a chemical reaction to occur inside the material, forming a stable blocky structure.

[0033] As mentioned above, the third aspect of the present invention provides the application of the multi-pH-segment slow-release alkaline buffer material described in the first aspect in the improvement of acidified environments, wherein the acidified environment includes at least one of acidic mine water inflow, acidified surface water / groundwater, and acidified farmland.

[0034] In a preferred embodiment, the material is used in the form of solid blocks for adding to infiltration dam fillers, reaction tank fillers, or farmland irrigation ditches; its release rate under soaking conditions is 0.8-3‰ / d, its service life is 1-3 years, and the pH of the effluent is stable within an adjustable range of 7-12.

[0035] The present invention will be described in detail below through examples. Unless otherwise specified, the raw materials used are all commercially available products.

[0036] In the following examples, unless otherwise specified, each "serving" represents 3g; Sodium silicate: Sodium metasilicate pentahydrate, modulus 1, purchased from Longxi Science and Chemical Co., Ltd., CAS number 10213-79-3; Metakaolin: calcined at 800℃ for 2 hours, with an average volume diameter of 20μm, purchased from Henan Borun Materials Co., Ltd. White clay: calcined at 800℃ for 2 hours, with an average volume diameter of 20μm, purchased from Henan Borun Materials Co., Ltd. Bentonite: calcium-based bentonite, purchased from JD Chemicals; Ethylene oxalic acid: purchased from Longxi Scientific Chemical Co., Ltd., CAS No. 6153-56-6; Stearic acid: purchased from Longxi Scientific Chemical Co., Ltd., CAS No. 57-11-4.

[0037] Preparation Example 1 This preparation example illustrates how the multi-pH-segment sustained-release alkaline buffer material provided by the present invention is obtained by following the steps below: (1) The soil polymer / hydrated minerals (24.7 parts metakaolin, 8 parts kaolin, 7 parts bentonite), 0.8 parts organic molecular framework (stearic acid) and 25 parts water are mixed in the first mixture to form a slow-release framework; (2) The sustained-release framework is mixed with alkaline material (3 parts sodium silicate and 18.5 parts calcium hydroxide) for a second time of not less than 30 minutes to obtain mixture I; (3) Mixture I is mixed with acidic material (13 parts oxalic acid) in a third mixing process to obtain mixture II; (4) The mixture II was cured for 24 hours to obtain a multi-pH slow-release alkaline buffer material, named hshc-1; The alkaline and acidic materials together form the pH buffer.

[0038] Preparation Example 2 This preparation example was carried out using a method similar to that of Preparation Example 1, except that the amounts of some components were different. Specifically: earth polymer / hydrated minerals (27.2 parts metakaolin, 8 parts kaolin, 7 parts bentonite), 0.8 parts organic molecular framework (stearic acid), 25 parts water, alkaline material (3 parts sodium silicate, 18.5 parts calcium hydroxide), and 10.5 parts acidic material (oxalic acid). Ultimately, a multi-pH sustained-release alkaline buffer material was obtained and named hshc-2.

[0039] Preparation Example 3 This preparation example was carried out using a method similar to that of Preparation Example 1, except that the amounts of some components were different. Specifically: earth polymer / hydrated minerals (28.4 parts metakaolin, 8 parts kaolin, 7 parts bentonite), 0.8 parts organic molecular framework (stearic acid), 25 parts water, alkaline material (3 parts sodium silicate, 18.5 parts calcium hydroxide), and 9.3 parts acidic material (oxalic acid). Ultimately, a multi-pH sustained-release alkaline buffer material was obtained and named hshc-3.

[0040] Preparation Example 4 This preparation example uses a method similar to that of Preparation Example 1, except that no acidic material is added, and the amounts of some components are different, specifically including: (1) The soil polymer / hydrated minerals (21.2 parts metakaolin, 8 parts kaolin, 7 parts bentonite), organic molecular framework (0.8 parts stearic acid) and 25 parts water are mixed in the first mixture to form a slow-release framework; (2) The slow-release framework is mixed with alkaline materials (3 parts sodium silicate and 25 parts calcium hydroxide) for a second time of not less than 30 min to obtain mixture I. Mixture I is then cured for 24 h to obtain a multi-pH slow-release alkaline buffer material, named hsj-1.

[0041] Preparation Example 5 This preparation example uses a method similar to that of Preparation Example 1, except that no acidic material is added, and the amounts of some components are different, specifically including: (1) The soil polymer / hydrated minerals (23.8 parts metakaolin, 8 parts kaolin, 7 parts bentonite), organic molecular framework (0.8 parts stearic acid) and 25 parts water are mixed in the first mixture to form a slow-release framework; (2) The slow-release framework is mixed with alkaline materials (3 parts sodium silicate and 22 parts calcium hydroxide) for a second time of not less than 30 min to obtain mixture I. Mixture I is then cured for 24 h to obtain a multi-pH slow-release alkaline buffer material, named hsj-2.

[0042] Test Example 1 The pH-segmented adjustment performance of the multi-pH-segmented slow-release alkaline buffer materials and alkaline buffer materials prepared in the above examples was simulated and determined using a continuous column chromatography method, specifically including: Quartz sand and alkaline buffer material were mixed and packed into the material column. The test water was a distilled water acetic acid solution with pH 6.5. The simulation experiment was started at a constant flow rate (30 mL / min). The pH change of the effluent was recorded at 60-minute intervals. The results are shown in Table 1. Table 1 Application Example 1 This application example illustrates the practical application effect of the multi-pH-segment slow-release alkaline buffer material provided by the present invention.

[0043] Test Project: A lead-zinc mine in Guangxi was shut down, covering an area of ​​approximately 12 km. 2 There are over one hundred abandoned mine shafts remaining in the mining area, with mine water having a pH of 2-4. The pilot test aims to adjust the mine water pH from 2 to 8, with a mine water outflow rate of 20 m³ / h. 3 / d.

[0044] A slow-release conditioning tank was designed, and 1.08 t of slow-release material with a release rate of 30 mol / (t*d) and a pH of 8-9 was added to the tank. The specific gravity of the material was 1.67 t / m³. 3 The material has a porosity of 35%, and the filling amount of the multi-pH-segment slow-release alkaline buffer material (hshc-1) is 1.8m³. 3 The designed alkali-adjusting sedimentation tank has dimensions of 2.0m*1.0m*1.0m and a hydraulic retention time of 45min.

[0045] The results of continuous monitoring of the effluent from the test point for 12 weeks are shown in Table 2. Table 2 The results above demonstrate that the multi-pH-segment slow-release alkaline buffer material provided by this invention possesses the characteristics of adjustable pH ranges, long-lasting slow release, and environmental friendliness, and can precisely stabilize pH according to different acidification scenarios. Its direct application in solid block form simplifies construction and maintenance, achieving efficient, long-lasting, and green passive remediation of acidified environments.

[0046] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A multi-pH-segment slow-release alkaline buffer material, characterized in that, The invention includes a sustained-release framework and a pH buffer encapsulated therein; wherein the sustained-release framework is composed of an organic molecular skeleton and terpenoids / hydrated minerals; and the pH buffer includes basic materials and optionally acidic materials to provide multi-stage pH buffering capacity in acidified environments.

2. The multi-pH-segment slow-release alkaline buffer material according to claim 1, characterized in that, The compressive strength of the multi-pH-segment slow-release alkaline buffer material is 3.5-8.7 MPa.

3. The multi-pH-segment slow-release alkaline buffer material according to claim 1 or 2, characterized in that, The organic molecular skeleton is selected from at least two of polyacrylic acid, carboxymethyl cellulose, hydroxypropyl methyl cellulose, N-vinylcaprolactam, hydroxyethyl cellulose, lignocellulose, lauric acid, palmitic acid, and stearic acid.

4. The multi-pH-segment slow-release alkaline buffer material according to claim 1 or 2, characterized in that, The soil polymer / hydrated mineral is selected from at least two of the following: calcium silicate, calcium aluminate, calcium carbonate, calcium chloride, calcium sulfate, metakaolin, kaolin, and bentonite.

5. The multi-pH-segment slow-release alkaline buffer material according to claim 4, characterized in that, The metakaolin and / or the white clay are calcined and have an average volume diameter of 10-30 μm.

6. The multi-pH-segment slow-release alkaline buffer material according to claim 1 or 2, characterized in that, The alkaline material is selected from at least one of calcium hydroxide, sodium hydroxide, and sodium silicate; and / or The acidic material is selected from at least one of formic acid, acetic acid, oxalic acid, and citric acid.

7. The multi-pH-segment slow-release alkaline buffer material according to claim 1 or 2, characterized in that, The material also contains water, and the mass fraction of each component, based on the total mass of the material, is as follows: The soil polymer / hydrated minerals: 30-50 wt%; The organic molecular skeleton: 0.2-1.2 wt%; The pH buffer: 15-36 wt%; Water content: 20-35 wt%.

8. A method for preparing a multi-pH-segment slow-release alkaline buffer material as described in any one of claims 1-7, characterized in that, This method uses the substances in the multi-pH-segment slow-release alkaline buffer material according to any one of claims 1-7, and includes the following steps: (1) The soil polymer / hydrated minerals, organic molecular framework and water are mixed in the first stage to form a slow-release framework; (2) The sustained-release framework is mixed with the alkaline material for a second time of not less than 30 minutes to obtain mixture I; (3) When the required sustained-release pH range is 7 ≤ pH < 10, the mixture I is mixed with the acidic material for a third time to obtain mixture II; When the required sustained-release pH range is 10 ≤ pH < 11.5, then mixture I is directly used as mixture II, and the acidic material is not added; (4) The mixture II is cured for 24-36 hours to obtain a multi-pH slow-release alkaline buffer material.

9. The application of a multi-pH-segment slow-release alkaline buffer material as described in any one of claims 1-7 in the improvement of acidified environments, characterized in that, The acidified environment includes at least one of the following: acidic mine water inflow, acidified surface water / groundwater, and acidified farmland.

10. The application according to claim 9, characterized in that, The material is used in the form of solid blocks for application in infiltration dam fillers, reaction tank fillers, or irrigation canals in farmland; its release rate under soaking conditions is 0.8-3‰ / d, its service life is 1-3 years, and the pH of the effluent is stable within an adjustable range of 7-12.

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