Clay-based phosphorus locking agent suitable for large-scale preparation as well as preparation method and application of clay-based phosphorus locking agent

Abstract

The invention relates to a clay-based phosphorus locking agent suitable for large-scale preparation and a preparation method and application thereof. The phosphorus locking agent is composed of purified clay and an aluminum-containing compound. Nontoxic and harmless clay is adopted as a raw material to load aluminum ion sites and is combined with phosphorus in water to generate insoluble aluminum phosphate, and the phosphorus in the water body is permanently fixed in the phosphorus locking agent, so that the phosphorus cannot be utilized by animals and plants in the water body, and the hidden danger of eutrophication of the water body is fundamentally eliminated. The clay-based phosphorus locking agent provided by the invention is simple in preparation process, low in cost, good in safety, green and pollution-free, and suitable for treatment of large-area and large-watershed phosphorus pollution of rivers, lakes and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment and ecological management, and particularly to a clay-based phosphorus-locking agent suitable for large-scale preparation, a preparation method thereof, and an application thereof. Background Art

[0002] The deterioration of water quality in rivers, lakes and reservoirs is a persistent global environmental problem faced by today's society. Water eutrophication is the main cause of the deterioration of water quality in rivers, lakes and reservoirs. Among them, the increase in the concentrations of nitrogen and phosphorus in water bodies will cause a large number of algae and aquatic plants to reproduce, destroying the ecological balance of water bodies. Therefore, the key to controlling water eutrophication is to control the concentrations of nitrogen and phosphorus in water bodies. In addition, research shows that phosphorus is an important key factor in water eutrophication. Controlling phosphorus in water bodies effectively is largely required for treating water eutrophication.

[0003] At present, the main phosphorus removal methods include chemical precipitation method, biological method and adsorption method. The biological phosphorus removal method is often used to treat low-concentration phosphorus-containing compounds mainly in organic form. The typical process is enhanced biological phosphorus removal. Phosphorus enrichment and removal are achieved through anaerobic phosphorus release and aerobic phosphorus uptake. However, the removal of phosphorus in water bodies is not thorough, and it is greatly affected by factors such as temperature. The adsorption method often uses materials with a large specific surface area and good adsorption performance for the deep treatment of low-concentration phosphorus-containing wastewater. However, the regeneration of the adsorbent is difficult and the operation cost is high.

[0004] The chemical precipitation method is the most commonly used phosphorus removal method at present. It has a quick effect and simple operation. However, there are still problems such as high cost in large-basin treatment, insufficient utilization of chemical reagents, and poor flocculation and sedimentation effects. Therefore, how to provide a phosphorus-locking agent with high phosphorus-locking efficiency and suitable for large-scale preparation to realize the large-scale application of the chemical precipitation method has become an urgent problem to be solved at present. Summary of the Invention

[0005] To solve the above technical problems, the present invention uses common clay and aluminum-containing compounds as raw materials and adopts a simple process method to prepare a clay-based phosphorus-locking agent. The prepared product has abundant aluminum sites, can combine with phosphorus in water to form aluminum phosphate, and at the same time, the clay can promote the co-sedimentation of aluminum phosphate, thereby achieving the goal of phosphorus removal.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a clay-based phosphorus-locking agent suitable for large-scale preparation, and the clay-based phosphorus-locking agent is composed of purified clay and an aluminum-containing compound.

[0008] The present invention uses common low-cost clay as a raw material, disperses aluminum sites on the clay surface, enabling the aluminum sites to fully combine with phosphorus in water to form water-insoluble aluminum phosphate. After the formation of aluminum phosphate, the phosphorus adheres to the clay surface and is more likely to sink to the bottom of the lake. The synergistic effect of the clay and the aluminum-containing compound makes the clay-based phosphorus-locking agent of the present invention have excellent phosphorus-locking effect.

[0009] As a preferred technical solution of the present invention, the clay includes purified yellow clay and / or purified red clay, preferably purified yellow clay.

[0010] As a preferred technical solution of the present invention, the aluminum-containing compound includes any one or a combination of at least two of alum, aluminum chloride, and aluminum nitrate, preferably alum.

[0011] As a preferred technical solution of the present invention, the mass ratio of the purified clay to the aluminum-containing compound is 1:(0.02 - 0.18), for example, it can be 1:0.02, 1:0.04, 1:0.06, 1:0.08, 1:0.10, 1:0.12, 1:0.14, 1:0.16, or 1:0.18, etc., preferably 1:(0.06 - 0.12).

[0012] The present invention preferably has the mass ratio of the purified clay to the aluminum-containing compound within the above range, which can achieve a better phosphorus-locking effect. Ensuring that there are sufficient aluminum sites evenly distributed on the surface of the purified clay can fully combine with phosphorus elements in water to generate aluminum phosphate. When the content of the aluminum-containing compound is low, there are not enough aluminum sites on the clay surface to combine with phosphorus elements in water, resulting in a decrease in the phosphorus removal rate in water. When the amount of aluminum ions is excessive, the clay is prone to agglomeration, reducing the utilization rate of aluminum sites and thus affecting the removal of phosphorus elements in water.

[0013] In a second aspect, the present invention provides a preparation method of the clay-based phosphorus-locking agent as described in the first aspect, and the preparation method includes the following steps:

[0014] (1) Remove impurities from the clay to obtain purified clay;

[0015] (2) Dissolve the aluminum-containing compound in water to obtain an aluminum-containing compound solution;

[0016] (3) Mix the aluminum-containing compound solution and the purified clay, stir evenly, and then successively undergo drying and grinding to obtain the clay-based phosphorus-locking agent.

[0017] The present invention uses common clay and alum as raw materials and adopts a simple process method to prepare a clay-based phosphorus-locking agent. In the prepared product, aluminum sites are evenly distributed on the clay surface. Its abundant aluminum sites can combine with phosphorus in water to form aluminum phosphate, and the aluminum phosphate adheres to the clay surface and promotes sedimentation to the bottom of the water, thereby achieving the goal of phosphorus removal and having broad practical application prospects. The raw materials used are extremely cheap and the synthesis method is extremely simple, which is very suitable for large-scale application.

[0018] As a preferred technical solution of the present invention, the impurity removal includes dispersing the clay in water, removing sand and stone impurities therein by filtration or levigation method, and then performing solid-liquid separation and drying in sequence.

[0019] The present invention places no restrictions on the solid-liquid separation, and any method known to those skilled in the art that can be used for solid-liquid separation can be adopted. For example, it can be filtration, sedimentation or centrifugation, etc.

[0020] As a preferred technical solution of the present invention, the drying temperature in step (3) is 40-80 °C, for example, it can be 40 °C, 50 °C, 60 °C, 70 °C or 80 °C, etc.

[0021] As a preferred technical solution of the present invention, the drying time in step (3) is 24-48 h, for example, it can be 24 h, 26 h, 28 h, 30 h, 35 h, 38 h, 40 h, 42 h, 44 h, 46 h or 48 h, etc.

[0022] In the third aspect, the present invention provides an application of the clay-based phosphorus-locking agent as described in the first aspect, and the application includes using the clay-based phosphorus-locking agent to control phosphorus pollution in large areas and large river basins.

[0023] As a preferred technical solution of the present invention, the applicable pH range of the clay-based phosphorus-locking agent for controlling phosphorus pollution in large areas and large river basins is 4-10, for example, it can be 4, 5, 6, 7, 8, 9 or 10, etc.

[0024] The clay-based phosphorus-locking agent provided by the present invention can achieve good phosphorus-locking effect within a relatively large pH range, enabling the clay-based phosphorus-locking agent to be applied to a variable water environment and used to control phosphorus pollution in large areas and large river basins, such as rivers, lakes, etc.

[0025] Compared with the prior art, the present invention has at least the following beneficial effects:

[0026] (1) The present invention combines clay and aluminum sites, evenly distributes the aluminum sites on the clay surface, enables the aluminum sites to be fully utilized, converts phosphorus in water into water-insoluble aluminum phosphate, and at the same time, the generated aluminum phosphate adheres to the clay surface and can be more easily sedimented to the bottom of the lake. Under relatively optimal conditions, the phosphorus removal rate in water can reach 97.9%.

[0027] (2) The raw materials used in the present invention are extremely cheap, and the synthesis method is simple, which is very suitable for large-scale application. Detailed implementation manners

[0028] For the convenience of understanding the present invention, the following examples are listed. Those skilled in the art should understand that the said examples are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0029] Example 1

[0030] This example provides a clay-based phosphorus-locking agent suitable for large-scale preparation, and the clay-based phosphorus-locking agent includes purified yellow clay and alum.

[0031] The preparation method of the clay-based phosphorus-locking agent includes the following steps:

[0032] (1) Dissolve yellow clay in water, and use the water flying method or filtration method to remove impurities such as sand and gravel in the yellow clay, and dry to obtain purified yellow clay;

[0033] (2) Mix 5 g of purified yellow clay with 9 mL of alum solution (alum content 0.1 g) evenly, and the mass ratio of the purified yellow clay to alum is 1:0.02;

[0034] (3) Place the precursor in step (2) in an oven and dry at 60 °C for 24 h, and grind to obtain the clay-based phosphorus-locking agent.

[0035] Example 2

[0036] This example provides a clay-based phosphorus-locking agent suitable for large-scale preparation, and the clay-based phosphorus-locking agent includes purified yellow clay and alum. Except that the mass of alum in step (2) is 0.3 g and the mass ratio of the purified yellow clay to alum is 1:0.06, the rest are the same as in Example 1.

[0037] Example 3

[0038] This example provides a clay-based phosphorus-locking agent suitable for large-scale preparation, and the clay-based phosphorus-locking agent includes purified yellow clay and alum. Except that the mass of alum in step (2) is 0.4 g and the mass ratio of the purified yellow clay to alum is 1:0.08, the rest are the same as in Example 1.

[0039] Example 4

[0040] This example provides a clay-based phosphorus-locking agent suitable for large-scale preparation, and the clay-based phosphorus-locking agent includes purified yellow clay and alum. Except that the mass of alum in step (2) is 0.6 g and the mass ratio of the purified yellow clay to alum is 1:0.12, the rest are the same as in Example 1.

[0041] Example 5

[0042] This embodiment provides a clay-based phosphorus-locking agent suitable for large-scale preparation. The clay-based phosphorus-locking agent includes purified yellow clay and alum. Except that the mass of the alum in step (2) is 0.9 g and the mass ratio of purified yellow clay to alum is 1:0.18, the rest are the same as in Example 1.

[0043] Comparative Example 1

[0044] This comparative example provides a phosphorus-locking agent, which is purified yellow clay; in the preparation method of the phosphorus-locking agent, except that alum is not added in step (2), the rest are the same as in Example 1.

[0045] Comparative Example 2

[0046] This comparative example provides a phosphorus-locking agent, which consists of activated carbon and alum; in the preparation method of the phosphorus-locking agent, except that purified yellow clay is replaced with activated carbon of equal mass, the rest are the same as in Example 1.

[0047] Comparative Example 3

[0048] This comparative example provides a phosphorus-locking agent, which consists of nano-titanium dioxide and alum; in the preparation method of the phosphorus-locking agent, except that purified yellow clay is replaced with nano-titanium dioxide of equal mass, the rest are the same as in Example 1.

[0049] Testing Method

[0050] The phosphorus-removing performance of the phosphorus-locking agents obtained in Examples 1-5 and Comparative Examples 1-3 was tested. The testing method includes: dispersing 500 mg of the clay-based phosphorus-locking agent in 100 mL of a phosphorus-containing solution (the initial concentration of phosphorus element in Examples 1-2, Examples 4-5, and Comparative Example 1 is: 10.07 mg / L; the initial concentration of phosphorus element in Example 3 and Comparative Examples 2-3 is: 9.38 mg / L), magnetically stirring for 2 h, sucking the suspension, and using a 0.22-micron Millipore filter to remove the phosphorus-locking agent in the suspension, and then measuring the remaining phosphorus concentration in the solution according to the determination of total phosphorus in water quality (ammonium molybdate spectrophotometry, GB11893-89), and calculating its removal rate. The results are shown in Table 1.

[0051] The performance test of the clay-based phosphorus-locking agent obtained in Example 2 for removing phosphorus in water at pH 3-10 was carried out. The test method includes: dispersing 500 mg of the clay-based phosphorus-locking agent in 100 mL of a phosphorus-containing solution (the initial concentrations of phosphorus elements at pH 3-10 are successively: 0.968 mg / L, 1.023 mg / L, 0.992 mg / L, 1.003 mg / L, 1.020 mg / L, 1.020 mg / L, 1.027 mg / L, 1.003 mg / L), magnetically stirring for 2 h, sucking the suspension, and after removing the phosphorus-locking agent in the suspension using a 0.22-micron Millipore filter, the concentration of the remaining phosphorus in the solution was measured according to the determination of total phosphorus in water quality (ammonium molybdate spectrophotometry, GB11893-89), and its removal rate was calculated. The results are shown in Table 2.

[0052] Test results:

[0053] Table 1

[0054]

[0055]

[0056] Table 2

[0057]

[0058] It can be seen from the test results that:

[0059] (1) It can be seen from the tests of removing phosphorus elements in water in Examples 1 to 5 that the present invention can achieve a good effect of removing phosphorus elements in water by attaching an aluminum-containing compound to the clay surface. And the mass ratio of the aluminum-containing compound to the clay was further optimized. As the amount of aluminum ions loaded on the clay gradually increased, the removal rate of phosphorus elements in water by the sample showed a trend of first increasing and then decreasing. The reason for this phenomenon is that when the amount of aluminum ions loaded on the clay surface is small, the binding sites for phosphorus elements in water will be seriously insufficient, thus affecting the removal rate of phosphorus elements in water; when the amount of aluminum ions loaded on the clay surface gradually increases, the binding sites for phosphorus elements in water will also gradually increase, thus effectively improving the removal rate of phosphorus elements in water; when the amount of aluminum ions loaded on the clay surface continues to increase, the clay may agglomerate, thus affecting its removal of phosphorus elements in water.

[0060] (2) It can be seen from the test of removing phosphorus elements in water with different pH values in Example 2 that the clay-based phosphorus-locking agent provided by the present invention can achieve a good effect of removing phosphorus elements in water in a water body with a pH of 4-10, and the phosphorus removal rate in water can reach more than 93%. When the pH value is 3, the removal of phosphorus in water in Example 2 decreased to a certain extent, which is because the aluminum phosphate generated has poor stability under acidic conditions with a pH of 3.

[0061] (3) It can be seen from Examples 1-5 and Comparative Examples 1-3 that the present invention can achieve good technical effects of removing phosphorus from water by promoting the full utilization of aluminum sites and the precipitation of aluminum phosphate through the synergistic effect of clay and aluminum-containing compounds. When no aluminum-containing compound is added to the phosphorus-locking agent, the phosphorus removal rate is only 16.1%. When the yellow clay is replaced with activated carbon or nano-titanium dioxide, the phosphorus-locking effect of the corresponding phosphorus-locking agent is significantly worse, and the phosphorus removal rate in water drops sharply to 7.0% and 15.4%. In addition, the cost of the phosphorus-locking agent also increases significantly, which is not conducive to large-scale preparation.

[0062] In summary, the present invention prepares a clay-based phosphorus-locking agent by a simple process. The prepared product has abundant aluminum sites, which can combine with phosphorus in water to form aluminum phosphate, thereby achieving the goal of phosphorus removal, and has broad practical application prospects. In addition, the raw materials used in the present invention are extremely cheap and the synthesis method is extremely simple, which is very suitable for large-scale application.

[0063] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A clay-based phosphorus-locking agent suitable for large-scale preparation, characterized in that: The clay-based phosphorus-locking agent consists of purified clay and aluminum-containing compounds.

2. The clay-based phosphorus-locking agent according to claim 1, characterized in that: The purified clay includes purified yellow clay and / or purified red clay, preferably purified yellow clay.

3. The clay-based phosphorus-locking agent according to claim 1 or 2, characterized in that: The aluminum-containing compound includes any one of alum, aluminum chloride and aluminum nitrate or a combination of at least two thereof, preferably alum.

4. The clay-based phosphorus-locking agent according to any one of claims 1 to 3, characterized in that: The mass ratio of the purified clay to the aluminum-containing compound is 1:(0.02-0.18), preferably 1:(0.06-0.12).

5. A method for preparing a clay-based phosphorus-locking agent according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: (1) removing impurities from clay to obtain purified clay; (2) dissolving an aluminum-containing compound in water to obtain an aluminum-containing compound solution; (3) The aluminum compound solution and purified clay are mixed, stirred evenly, and then dried and ground in sequence to obtain the clay-based phosphorus locking agent.

6. The preparation method according to claim 5, characterized in that: The impurity removal comprises dispersing clay in water, removing sand and stone impurities therein by filtering or water jetting, and then sequentially performing solid-liquid separation and drying.

7. The preparation method according to claim 5 or 6, characterized in that: The drying temperature in step (3) is 40-80°C.

8. The preparation method according to any one of claims 5 to 7, characterized in that: The drying time in step (3) is 24-48 hours.

9. An application of the clay-based phosphorus-locking agent according to any one of claims 1 to 4, characterized in that: The application includes using the clay-based phosphorus-locking agent to control phosphorus pollution in large areas and large watersheds.

10. The use according to claim 9, characterized in that: The applicable pH range of the clay-based phosphorus-locking agent for treating phosphorus pollution in large areas and large watersheds is 4-10.

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