A saline-alkali land drainage pipe and its preparation method and application

Abstract

The present invention provides a saline-alkali land drainage pipe and a preparation method and application thereof, belonging to the technical field of soil remediation. The saline-alkali land drainage pipe provided by the present invention is made of phosphogypsum and oyster shells, and the weight ratio of the phosphogypsum and oyster shells is (1‑3): (1‑4). The drainage pipe provided by the present invention not only solves the problem that traditional salt discharge pipes are prone to aging and breaking, and the salt discharge port is easily blocked by water, but also improves the drainage efficiency, thereby improving the soil structure, improving soil fertility, and being beneficial to plant growth, and the cost is low, which is conducive to large-scale application. In addition, the drainage pipe provided by the present invention can improve the air permeability and water retention of the soil, while reducing the salt content of the soil, which is beneficial to plant growth, thereby realizing effective remediation of saline-alkali land. The drainage pipe material of the present invention is widely available, low in price, and has excellent performance, and can replace the existing high-priced and highly polluting drainage pipe materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of soil remediation, and in particular relates to a saline-alkali land drainage pipe and a preparation method and application thereof. Background Art

[0002] Saline-alkali land is an important land resource. The formation of saline-alkali land is mainly due to excessive salt in groundwater. These salts will accumulate on the soil surface, resulting in an increase in soil pH and destruction of soil structure, which will affect plant growth. Therefore, the restoration of saline-alkali land is an important research field. In the field of environmental engineering technology, a common solution is to drain the salt water from saline-alkali land through a drainage system. Traditional drainage systems usually use salt drainage pipes made of materials such as plastic or cement. Plastic pipes are prone to aging and breaking, and the salt drainage ports are easily blocked by water, resulting in poor drainage effects. Cement pipes are expensive, and it is time-consuming and laborious to remove cement pipes from the soil system after they are broken, which will undoubtedly further increase the cost of use. In the field of soil remediation technology, another method is to use materials such as phosphogypsum and oyster shells to improve saline-alkali land. Phosphogypsum is an industrial byproduct that is rich in calcium and sulfur elements. It can improve soil structure and increase soil aeration and water retention. Oyster shells are a natural biomaterial with good adsorption and stability, which can effectively reduce the salt content of the soil. In the field of building materials technology, some new materials are also used to make drainage pipes, such as polymer materials, but these materials are expensive and may have a certain impact on the environment. It can be seen that the existing solutions for saline-alkali land are mainly to improve the design of the drainage system, such as increasing the strength and durability of the salt drainage pipe, or using more advanced materials to make the salt drainage pipe. In addition, there are some methods to improve the structure and function of the soil by changing the physical and chemical properties of the soil, such as adding materials such as phosphogypsum and oyster shells. However, there are still some problems with the existing technology in practical applications. First, traditional salt drainage pipes are prone to aging and breaking, and the salt drainage ports are easily blocked by water, resulting in poor drainage effects. Secondly, although materials such as phosphogypsum and oyster shells can improve the structure and function of the soil, their usage is large and the cost is high. In addition, the processing and utilization of these materials is also a problem, which may have a certain impact on the environment. Finally, although the existing drainage pipe materials such as polymer materials have good performance, they are expensive and are not conducive to large-scale application. Summary of the invention

[0003] In view of this, an object of the present invention is to provide a saline-alkali land drainage pipe that can effectively solve the problems that traditional salt discharge pipes are prone to aging and breakage, and salt discharge ports are easily blocked by water.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a saline-alkali land drainage pipe, which is made of phosphogypsum and oyster shells, and the weight ratio of the phosphogypsum to the oyster shells is (1-3): (1-4).

[0006] Preferably, the particle size of the phosphogypsum is 0.5-1 mm.

[0007] Preferably, the particle size of the oyster shell is 1-2 mm.

[0008] The present invention also provides a method for preparing the saline-alkali land drainage pipe, comprising the following steps: mixing the phosphogypsum and the oyster shell, calcining at a temperature of 800°C-1000°C for 1h-2h to obtain a mixture A; and pressing the mixture A into a shape to obtain the saline-alkali land drainage pipe.

[0009] Preferably, the pressing pressure is 10 MPa-15 MPa.

[0010] Preferably, the saline-alkali land drainage pipe has a wall thickness of 50mm-60mm, an inner diameter of 150mm-250mm, and an outer diameter of 200mm-310mm.

[0011] The present invention also provides application of the saline-alkali land drainage pipe or the preparation method in saline-alkali land soil remediation.

[0012] Beneficial effects of the present invention:

[0013] The drain pipe provided by the present invention not only solves the problem that the traditional salt discharge pipe is easy to age and break, and the salt discharge port is easy to be blocked by water, but also improves the drainage efficiency, thereby improving the soil structure, increasing the soil fertility, and being conducive to the growth of plants, and the cost is low, which is conducive to large-scale application. In addition, the drain pipe provided by the present invention can improve the air permeability and water retention of the soil, while reducing the salt content of the soil, which is conducive to the growth of plants, thereby realizing the effective restoration of saline-alkali land. This is something that traditional salt discharge pipes cannot do. The drain pipe material of the present invention has a wide range of sources, low prices, and excellent properties, such as high strength and durability, which can replace the existing high-priced and highly polluting drain pipe materials and meet the market demand for environmentally friendly, low-cost, and high-performance building materials. Moreover, the treatment and utilization of the drain pipe of the present invention is relatively simple, has little impact on the environment, and meets the current environmental protection requirements. However, the treatment and utilization process of traditional salt discharge pipe materials such as plastics or cement will have a certain impact on the environment. The drain pipe of the present invention has a long service life and good use effect, which can not only save the cost of replacement and maintenance, but also save a lot of manpower and material resources, and has high economic value and social benefits. DETAILED DESCRIPTION

[0014] The present invention provides a saline-alkali land drainage pipe, which is made of phosphogypsum and oyster shells, and the weight ratio of the phosphogypsum to the oyster shells is (1-3): (1-4).

[0015] In a specific embodiment of the present invention, phosphogypsum is derived from solid waste residue generated during the production of phosphoric acid, which is an industrial hazardous waste. Its main mineral component is CaSO4·2H2O, and it contains impurities such as phosphorus, fluoride, and organic matter. Oyster shells are the product of oyster metabolism, and their main component is CaO. After removing the internal organs, the shells are piled up as biological waste, causing environmental pollution.

[0016] In the present invention, the weight ratio of the phosphogypsum to the oyster shell is preferably (1-2): (1-3), more preferably 1:1, the particle size of the phosphogypsum is preferably 0.5-1 mm, more preferably 0.6-0.8 mm, and the particle size of the oyster shell is preferably 1-2 mm, more preferably 1.2-1.8 mm.

[0017] The present invention also provides a method for preparing the saline-alkali land drainage pipe, comprising the following steps: mixing the phosphogypsum and the oyster shell, calcining at a temperature of 800°C-1000°C for 1h-2h to obtain a mixture A; and pressing the mixture A into a shape to obtain the saline-alkali land drainage pipe.

[0018] In the present invention, the calcination temperature is preferably 850-950°C, more preferably 900°C, the calcination time is preferably 1.2h-1.8h, more preferably 1.5h, under the calcination conditions of the present invention, phosphogypsum and oyster shells will react chemically to generate a drainage pipe material with certain strength and corrosion resistance. In the present invention, the pressing pressure is preferably 10MPa-15MPa, more preferably 11MPa-14MPa, and most preferably 12MPa. In the present invention, the wall thickness of the saline-alkali land drainage pipe is preferably 50mm-60mm, more preferably 52mm-58mm, the inner diameter of the saline-alkali land drainage pipe is preferably 150mm-250mm, more preferably 160mm-220mm, and the outer diameter of the saline-alkali land drainage pipe is preferably 200mm-310mm, more preferably 230mm-280mm.

[0019] In the present invention, the main mineral component of phosphogypsum is CaSO4·2H2O, which contains impurities such as phosphorus, fluoride, and organic matter, resulting in loose crystal structure, poor crystallinity, and a pH of 4-6, which is very acidic. After being ground to a particle size of 0.5-1 mm, its specific surface area can be increased to 400 m 2 / kg-600m 2 / kg, mixed evenly with oyster shells with a particle size of 1-2mm and calcined together, it can fully react with oyster shells. The specific mechanism is as follows: the specific surface area of ​​phosphogypsum and oyster shells increases to 400m after grinding. 2 / kg-600m 2 / kg, has a certain property of absorbing crystal water of phosphogypsum. The main component of oyster shell is CaO. After calcination, the activity of CaO is increased, and it reacts with phosphogypsum to increase the pH. CaO reacts with the moisture in phosphogypsum to generate Ca(OH)2. The Ca(OH)2 generated by the hydration reaction reacts with phosphogypsum and SiO2 therein to generate colloid-like substances such as calcium silicate hydrate (CSH), which wraps the phosphogypsum in a colloidal network structure to improve the strength of the phosphogypsum material.

[0020] The present invention also provides application of the saline-alkali land drainage pipe or the preparation method in saline-alkali land soil remediation.

[0021] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0022] In the following embodiments, unless otherwise specified, all of them are conventional methods.

[0023] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0024] Example 1

[0025] A saline-alkali land drainage pipe is made of phosphogypsum and oyster shells, the weight ratio of the phosphogypsum to the oyster shells is 1:1, the particle size of the phosphogypsum is 0.5 mm, and the particle size of the oyster shells is 1 mm.

[0026] Example 2

[0027] A saline-alkali land drainage pipe is made of phosphogypsum and oyster shells, the weight ratio of the phosphogypsum to the oyster shells is 1:2, the particle size of the phosphogypsum is 1 mm, and the particle size of the oyster shells is 2 mm.

[0028] Example 3

[0029] A saline-alkali land drainage pipe is made of phosphogypsum and oyster shells, the weight ratio of the phosphogypsum to the oyster shells is 1:3, the particle size of the phosphogypsum is 0.7 mm, and the particle size of the oyster shells is 1.5 mm.

[0030] Example 4

[0031] The saline-alkali land drainage pipe described in Example 1 is prepared by the following steps:

[0032] Prepare phosphogypsum and oyster shells in a weight ratio of 1:1, totaling 2000 kg. The particle size of phosphogypsum is 0.5 mm, and the particle size of oyster shells is 1 mm. Mix the two evenly to obtain a mixture.

[0033] The mixture was placed in a high-temperature furnace and calcined at 800°C for 2h to obtain mixture A. Mixture A was poured into a mold and pressed into shape at a pressure of 10MPa using a press, and then naturally cooled at room temperature and demolded to obtain a saline-alkali land drainage pipe having a wall thickness of 50mm, an inner diameter of 150mm, and an outer diameter of 200mm.

[0034] Example 5

[0035] The saline-alkali land drainage pipe described in Example 2 is prepared by the following steps:

[0036] Prepare phosphogypsum and oyster shells in a weight ratio of 1:2, totaling 2000 kg. The particle size of the phosphogypsum is 1 mm, and the particle size of the oyster shell is 2 mm. Mix the two evenly to obtain a mixture.

[0037] The mixture was placed in a high-temperature furnace and calcined at 850°C for 1.2 hours to obtain mixture A. Mixture A was poured into a mold and pressed into shape using a press at a pressure of 15 MPa, and then naturally cooled at room temperature and demolded to obtain a saline-alkali land drainage pipe having a wall thickness of 60 mm, an inner diameter of 250 mm, and an outer diameter of 310 mm.

[0038] Comparative Example 1

[0039] The difference from Example 1 is that the weight ratio of phosphogypsum to oyster shell is 1:5, and the rest is the same as Example 1. The specific preparation method is the same as Example 4. The compressive strength and flexural strength of the saline-alkali land drainage pipe obtained in Example 1 and the drainage pipe obtained in Comparative Example 1 were tested, and the results are shown in Table 1:

[0040] Table 1 Compressive and flexural strength test results of the drainage pipes obtained in Example 1 and Comparative Example 1

[0041] Detection indicators Example 1 Comparative Example 1 Compressive strength / MPa 25.52 16.33 Flexural strength / MPa 4.32 2.44

[0042] The greater the compressive strength, the stronger its ability to resist pressure, and the greater the flexural strength, the stronger its ability to resist aging. It can be seen from Table 1 that compared with Comparative Example 1, the pipeline of Example 1 has stronger compressive and aging resistance.

[0043] Example 6

[0044] The saline-alkali land drainage pipe obtained in Example 4 is installed in the saline-alkali land, and the inclination of the drainage pipe is maintained at 10° to facilitate the discharge of salt water. After the saline-alkali land is filled with water, the salt water will flow along the drainage pipe to the drainage ditch next to it.

[0045] Example 7

[0046] The saline-alkali land drainage pipe obtained in Example 4 is installed at a depth of 1-2m on the surface of the saline-alkali land, the inclination of the drainage pipe is maintained at 5-10°, and the soil is covered so that after the saline-alkali land is irrigated, the salt water can flow along the drainage pipe to the drainage ditch next to it.

[0047] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A saline-alkali land drainage pipe, characterized in that: The saline-alkali land drainage pipe is made of phosphogypsum and oyster shells, and the weight ratio of the phosphogypsum to the oyster shells is (1-3):(1-4); The particle size of the phosphogypsum is 0.5-1 mm; The particle size of the oyster shell is 1-2 mm; The method for preparing the saline-alkali land drainage pipe comprises the following steps: The phosphogypsum and the oyster shell are mixed, and calcined at a temperature of 800°C-1100°C for 1-2 hours to obtain a mixture A; the mixture A is pressed into a shape to obtain a saline-alkali land drainage pipe.

2. The saline-alkali land drainage pipe according to claim 1, characterized in that: The pressing pressure is 10MPa-15MPa.

3. The saline-alkali land drainage pipe according to claim 1, characterized in that: The saline-alkali land drainage pipe has a wall thickness of 50mm-60mm, an inner diameter of 150mm-250mm, and an outer diameter of 200mm-310mm.

4. Use of the saline-alkali land drainage pipe according to any one of claims 1 to 3 in saline-alkali land soil remediation.