A kind of phosphorus adsorbent and preparation method thereof

Abstract

The present invention provides a phosphorus adsorbent and a preparation method thereof, and relates to the technical field of water pollution control. The present invention uses waste gypsum as a raw material, and prepares a phosphorus adsorbent through drying, crushing, low-temperature pyrolysis and other steps. The present invention realizes the resource utilization of waste gypsum boards, and can recover phosphorus in water bodies at the same time, which conforms to the concept of treating waste with waste, avoids the harm caused by the secondary release of calcium sulfate and other ions by waste gypsum boards in the natural environment, and has important significance for the application of gypsum pyrolysis materials in the field of phosphorus adsorption.

Description

Technical Field

[0001] The invention relates to the technical field of water pollution control, and in particular to a phosphorus adsorbent and a preparation method thereof. Background Art

[0002] Phosphorus is one of the elements necessary for life and plays an important role in organisms. It is a component of biological molecules such as DNA, RNA, and ATP, and is essential for the growth, metabolism, and energy conversion of organisms. In the agricultural field, phosphorus is one of the nutrients necessary for plant growth. The supply of phosphorus in fertilizers can increase the yield and quality of crops. However, excessive release of phosphorus into water bodies can lead to eutrophication of water bodies, triggering a series of environmental problems including excessive growth of algae, algal blooms, eutrophication of water bodies, and ecosystem collapse. This not only affects the ecological balance of water bodies and the sustainable use of water resources, but may also have a negative impact on human health and well-being. Therefore, it is crucial to control and recycle phosphorus in water bodies.

[0003] Gypsum board is a material made of building gypsum as the main raw material, and its main component is calcium sulfate dihydrate. This material has the characteristics of light weight, easy processing, sound insulation, heat insulation, flame retardancy, etc., and is widely used in construction and decoration. With the continuous investment and construction of gypsum industry projects, the output of waste gypsum board is also accumulating, becoming an environmental problem that needs to be dealt with urgently. Traditional methods of treating gypsum board waste mainly include landfill, incineration and recycling. However, these methods have some obvious disadvantages. Landfilling gypsum board will cause waste of resources and may cause soil and groundwater pollution; incineration may release harmful gases and cause air pollution; recycling is restricted by technical limitations and economic costs. Therefore, it is urgent to adopt more energy-saving and environmentally friendly means to treat and dispose of gypsum board waste, so as to minimize the impact on the environment and realize the resource utilization of gypsum board waste.

[0004] Pyrolysis refers to the process of decomposing compounds into simpler compounds or elements by heating under oxygen-deficient conditions. It is a common method for preparing adsorbents. Moisture or other impurities on the surface of waste gypsum materials may occupy active sites, affecting their adsorption capacity for target molecules. These surface impurities are removed by pyrolysis, thereby releasing active sites and improving the adsorption capacity of the adsorbent material. The traditional pyrolysis process is usually carried out at a temperature of 300℃-800℃. This high temperature condition will trigger chemical reactions and structural changes inside the material. Within this temperature range, organic matter will decompose to produce gas, while inorganic matter may be partially pyrolyzed, dehydrated or converted into other compounds. In addition, high-temperature pyrolysis may also increase the crystallinity of the material and change the pore structure, thereby affecting its physical and chemical properties. However, high-temperature pyrolysis consumes a lot of energy, has many side reactions, and has high requirements for equipment, which in turn increases the preparation cost of the product.

[0005] Therefore, it is necessary to develop a low-temperature pyrolysis process for waste gypsum materials and use it to make materials with higher phosphorus adsorption performance to overcome the existing problems. Summary of the invention

[0006] To solve the above problems, the present invention provides a method for preparing a phosphorus adsorbent using waste building gypsum as raw material, which realizes the resource utilization of waste gypsum boards and can recover phosphorus in water bodies, conforming to the concept of treating waste with waste, and avoiding the harm caused by the secondary release of calcium sulfate and other ions by waste gypsum boards in the natural environment.

[0007] The method for preparing the phosphorus adsorbent of the present invention comprises the following steps:

[0008] S1, drying the waste gypsum to remove moisture;

[0009] S2, crushing the dried gypsum and sieving it;

[0010] S3, pyrolyzing the crushed gypsum at low temperature to obtain a pyrolysis product;

[0011] S4, grinding and sieving the pyrolysis product to obtain a phosphorus adsorbent;

[0012] The SO3 content in the waste gypsum is less than 47%, the CaO content is greater than 45%, and the Al2O3 content is less than 1%.

[0013] Furthermore, the waste gypsum is construction waste gypsum.

[0014] Furthermore, the drying temperature is 100°C-120°C, and the drying time is 24 hours. Preferably, the drying temperature is 105°C.

[0015] Furthermore, the low-temperature pyrolysis is carried out under anaerobic or anoxic conditions.

[0016] Furthermore, the low-temperature pyrolysis is carried out under an inert gas atmosphere.

[0017] Furthermore, the inert gas includes but is not limited to nitrogen and argon.

[0018] Furthermore, the flow rate of the inert gas is 0.5 L / min-2 L / min.

[0019] Furthermore, the heating rate of the low-temperature pyrolysis is 5°C / min-10°C / min, the pyrolysis temperature is 150°C-300°C, and the pyrolysis holding time is 1 h-4 h. Preferably, the low-temperature pyrolysis temperature is 150°C, and the pyrolysis time is 2 h.

[0020] The present invention also provides a phosphorus adsorbent prepared according to the method.

[0021] Compared with the prior art, the beneficial technical effects of the present invention are:

[0022] The present invention converts the gypsum board into a material with higher adsorption performance by performing pyrolysis under low temperature conditions, thereby providing a new solution to the problem of phosphorus pollution in water bodies.

[0023] The low-temperature pyrolysis process of the present invention has low energy consumption and low requirements for equipment. The lower temperature can reduce the occurrence of side reactions and retain the organic components in the material, which is beneficial to maintaining the structure and properties of the material. It has important scientific and practical significance for exploring the potential of gypsum pyrolysis materials in the field of phosphorus adsorption. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described below in conjunction with the accompanying drawings.

[0025] Figure 1 Phosphorus adsorption isotherms of different adsorption materials of Test Example 1 of the present invention;

[0026] Figure 2 Phosphorus adsorption isotherms of different adsorption materials of Test Example 2 of the present invention;

[0027] Figure 3 The maximum adsorption capacity of different adsorption materials in Test Example 3 of the present invention;

[0028] Wherein: the pyrolyzed gypsum board is the phosphorus adsorbent prepared by pyrolysis at 150°C in Example 1, and the unpyrolyzed gypsum board is the product of waste gypsum board dried at 105°C for 24 hours and then crushed and passed through a 60-mesh sieve;

[0029] The pyrolyzed desulfurized gypsum is the low-temperature pyrolysis product prepared in Comparative Example 3, and the unpyrolyzed desulfurized gypsum is the product of the desulfurized gypsum dried at 105° C. for 24 h and then crushed and passed through a 60-mesh sieve;

[0030] The pyrolyzed phosphogypsum is the low-temperature pyrolysis product prepared in Comparative Example 4, and the unpyrolyzed phosphogypsum is the product of phosphogypsum being dried at 105° C. for 24 h and then crushed and passed through a 60-mesh sieve;

[0031] The pyrolyzed CaSO4·2H2O is the low-temperature pyrolysis product prepared in Comparative Example 2, and the unpyrolyzed CaSO4·2H2O is the product of the CaSO4·2H2O agent being dried at 105°C for 24 h and then crushed and passed through a 60-mesh sieve.

[0032] Figure 4 SEM images of different adsorption materials;

[0033] Among them: a is unpyrolyzed gypsum board (a product of discarded gypsum board dried at 105°C for 24 hours and crushed and passed through a 60-mesh sieve); b is the pyrolysis product of gypsum board (Example 1, 150°C); c is the unpyrolyzed gypsum board (a product of discarded gypsum board dried at 105°C for 24 hours and crushed and passed through a 60-mesh sieve) after adsorption of phosphorus; d is the pyrolysis product of gypsum board (Example 1, 150°C) after adsorption of phosphorus. DETAILED DESCRIPTION

[0034] The present invention provides a method for preparing a phosphorus adsorbent, comprising the following steps:

[0035] S1, drying the waste gypsum to remove moisture;

[0036] S2, crushing the dried gypsum and sieving it;

[0037] The present invention does not strictly limit the size of the screen, but between 30-100 meshes can improve the recovery efficiency of the material while ensuring the uniformity of the particle size;

[0038] S3, pyrolyzing the crushed gypsum at low temperature to obtain a pyrolysis product;

[0039] S4, grinding and sieving the pyrolysis product to obtain a phosphorus adsorbent.

[0040] In one embodiment, the waste gypsum is construction waste gypsum.

[0041] In one embodiment, the drying temperature is 100° C.-120° C., and the drying time is 24 h. In one embodiment, the drying temperature is 105° C. The present invention does not strictly limit the drying temperature, but a better drying effect and speed can be achieved at 105° C.

[0042] In one embodiment, the low temperature pyrolysis is performed under anaerobic or anoxic conditions.

[0043] In one embodiment, the low temperature pyrolysis is performed under an inert gas atmosphere.

[0044] In one embodiment, the inert gas includes but is not limited to nitrogen and argon.

[0045] In one embodiment, the flow rate of the inert gas is 0.5 L / min-2 L / min.

[0046] In one embodiment, the heating rate of the low-temperature pyrolysis is 5°C / min-10°C / min, the pyrolysis temperature is 150°C-300°C, and the pyrolysis holding time is 1 h-4 h.

[0047] In one embodiment, the low-temperature pyrolysis temperature is 150° C., and the pyrolysis holding time is 2 h.

[0048] The present invention strictly limits the heating rate in the low-temperature pyrolysis process, and only the phosphorus adsorbent prepared within this range has a good phosphorus adsorption effect.

[0049] The increase of pyrolysis temperature has an inhibitory effect on the phosphorus adsorption effect of the pyrolysis material of the present invention. Therefore, the present invention strictly limits the pyrolysis temperature and the heating rate to improve the phosphorus adsorption performance of the material.

[0050] The present invention pyrolyzes the gypsum board alone to enhance the material's ability to adsorb phosphorus, does not require multiple substances to be compounded, simplifies the material synthesis process, and significantly enhances the phosphorus adsorption capacity. Experiments have shown that the ability of the pyrolyzed gypsum board to adsorb phosphorus is greatly enhanced, and the maximum adsorption capacity is 6 times that of the initial gypsum board. At the same time, the present invention finds that the optimal pyrolysis temperature of the material is 150°C. At this temperature, the original structure of the material is not significantly destroyed, reducing the risk of material denaturation. The lower temperature also avoids the risk of calcium sulfate releasing toxic gases at high temperatures. At the same time, the energy required for pyrolysis at 150°C is less, which can reduce energy consumption and production costs. The present invention uses low-temperature pyrolysis of waste gypsum board to produce phosphorus adsorbents, which can effectively solve the current problems of waste gypsum treatment and disposal, phosphorus pollution in water bodies, and phosphorus recovery and reuse. It is a wastewater treatment technology that treats waste with waste, which can achieve the purpose of comprehensive utilization and greatly improve the economic added value of waste gypsum board.

[0051] The technical solution provided by the present invention is further described below in conjunction with embodiments.

[0052] The compositions of the waste gypsum board (Shanghai Liming Resource Recycling Co., Ltd.), desulfurized gypsum (Gongyi Yuanheng Water Purification Material Factory), and phosphogypsum (Gongyi Yuanheng Water Purification Material Factory) used in the embodiments, comparative examples, and test examples of the present invention are as follows:

[0053]

[0054] Example 1

[0055] A method for preparing a phosphorus adsorbent, comprising the following steps:

[0056] S1. Dry the waste gypsum board at 105°C for 24 h to remove moisture;

[0057] S2, crush the dried gypsum board and pass it through a 60-mesh sieve;

[0058] S3, pyrolyzing the crushed gypsum at low temperature to obtain a pyrolysis product;

[0059] The low-temperature pyrolysis process is carried out in a nitrogen atmosphere, the nitrogen flow rate is 1 L / min, the heating rate is 5°C / min, the low-temperature pyrolysis temperatures are 150°C, 200°C, 300°C, 500°C, and the low-temperature pyrolysis time is 2 h;

[0060] S4. Grind the phosphorus adsorbent through a 60-mesh sieve to obtain a phosphorus adsorbent.

[0061] Example 2

[0062] S1. Dry the waste gypsum board at 105°C for 24 h to remove moisture;

[0063] S2, crush the dried gypsum board and pass it through a 60-mesh sieve;

[0064] S3, pyrolyzing the crushed gypsum at low temperature to obtain a pyrolysis product;

[0065] The low-temperature pyrolysis process was carried out in a nitrogen atmosphere, the nitrogen flow rate was 1 L / min, the heating rate was 10°C / min, the low-temperature pyrolysis temperature was 300°C, and the low-temperature pyrolysis time was 2 h;

[0066] S4. Grind the phosphorus adsorbent through a 60-mesh sieve to obtain a phosphorus adsorbent.

[0067] Comparative Example 1

[0068] S1. Dry the waste gypsum board at 105°C for 24 h to remove moisture;

[0069] S2, crush the dried gypsum board and pass it through a 60-mesh sieve;

[0070] S3, calcining the crushed gypsum in an air atmosphere to obtain a phosphorus adsorbent;

[0071] The calcination heating rate is 10°C / min, the calcination temperature is 300°C, and the calcination time is 2 h;

[0072] S4. Grind the phosphorus adsorbent through a 60-mesh sieve to obtain a phosphorus adsorbent.

[0073] Comparative Example 2

[0074] S1, drying CaSO4·2H2O reagent (Shanghai Titan Technology Co., Ltd.) at 105℃ for 24 h to remove moisture;

[0075] S2. Crush the dried CaSO4·2H2O agent and pass it through a 60-mesh sieve;

[0076] S3, pyrolyzing the crushed CaSO4·2H2O reagent at low temperature to obtain a pyrolysis product;

[0077] In the low-temperature pyrolysis process, the heating rate is 10°C / min, the low-temperature pyrolysis temperature is 300°C, and the low-temperature pyrolysis holding time is 2 h.

[0078] Comparative Example 3

[0079] S1. Dry the desulfurized gypsum at 105°C for 24 h to remove moisture;

[0080] S2, crush the dried desulfurized gypsum and pass it through a 60-mesh sieve;

[0081] S3, pyrolyzing the crushed desulfurized gypsum at low temperature to obtain a pyrolysis product;

[0082] In the low-temperature pyrolysis process, the heating rate is 10°C / min, the low-temperature pyrolysis temperature is 300°C, and the low-temperature pyrolysis holding time is 2 h.

[0083] Comparative Example 4

[0084] S1. Dry the phosphogypsum at 105°C for 24 h to remove moisture;

[0085] S2, crush the dried phosphogypsum and pass it through a 60-mesh sieve;

[0086] S3, pyrolyzing the crushed phosphogypsum at low temperature to obtain a pyrolysis product;

[0087] In the low-temperature pyrolysis process, the heating rate is 10°C / min, the low-temperature pyrolysis temperature is 300°C, and the low-temperature pyrolysis holding time is 2 h.

[0088] Testing has shown that phosphogypsum is unable to adsorb phosphorus before and after pyrolysis.

[0089] Test Example 1

[0090] The adsorbent and the pyrolysis product of Example 1 were subjected to a phosphorus adsorption test, with untreated waste gypsum board as a control. The specific test method is as follows:

[0091] The adsorption experiment used KH2PO4 and deionized water to prepare phosphorus stock solution and stored it at room temperature. The amount of the prepared adsorbent was 0.1 g, the volume of the phosphorus solution was 20 mL, and the volume of the centrifuge tube for the adsorption reaction was 50 mL. The adsorption reaction was carried out at room temperature (25±3°C) and on a mechanical shaker at 200 rpm, and the adsorption contact time was 24 h. The concentrations of the phosphorus solution were set to 10 mgP / L, 50 mgP / L, 100 mgP / L, 200 mgP / L, 400 mgP / L, 800 mgP / L, and 1000 mgP / L. After the adsorption reaction, the supernatant was filtered with a 0.45 μm filter membrane and the phosphorus concentration of the filtrate was measured by ICP-OES.

[0092] The phosphorus adsorption amount was calculated from the change in phosphorus concentration before and after adsorption. Each experiment was repeated twice. When the experimental error was less than 3%, the average value was taken as the valid data. The test results are shown in Figure 1 shown.

[0093] Test Example 2

[0094] The adsorbent materials of Example 2 and Comparative Example 1 were subjected to phosphorus adsorption tests, with untreated waste gypsum board as a control. The test method was the same as that of Example 1, and the test results were as follows: Figure 2 shown.

[0095] Test Example 3

[0096] The adsorbent materials of Comparative Examples 2, 3 and 4 were subjected to phosphorus adsorption tests, with untreated (unpyrolyzed) CaSO4·2H2O reagent, desulfurized gypsum and phosphogypsum as controls. The test method was the same as in Example 1, and the test results were as follows: Figure 3 shown.

[0097] Example 3

[0098] Same as Example 1, except that the heating rate is 3°C / min. After testing, the maximum phosphorus adsorption capacity of the adsorption material is 87.59 mgP / g.

[0099] Example 4

[0100] Same as Example 1, except that the heating rate is 12°C / min. After testing, the maximum phosphorus adsorption capacity of the adsorption material is 76.44 mgP / g.

[0101] The Langmuir model was used to fit the adsorption isotherm, and it was found that the maximum adsorption capacity of the waste gypsum board increased from 35.00 mgP / g to 204.85 mgP / g ( Figure 1 ), that is, the adsorption capacity of phosphorus by the pyrolysis products after low-temperature pyrolysis is about 6 times higher than that of the unmodified gypsum board. In addition, the effect of different pyrolysis temperatures of gypsum board on the adsorption capacity is compared ( Figure 1 ), and found that the adsorption capacity of gypsum board pyrolysis products for phosphorus decreased with increasing pyrolysis temperature. The adsorption capacity of gypsum board pyrolysis and calcination at the same temperature is expressed as ( Figure 2 ), the improvement of gypsum board's phosphorus adsorption performance is not only due to the removal of its own bound water, but also due to other factors. Comparison of the adsorption performance of four materials before and after pyrolysis: waste gypsum board, CaSO4·2H2O agent, desulfurized gypsum and phosphogypsum ( Figure 3), and found that although the main components of the four substances are all CaSO4·2H2O, due to the impurities contained in the waste gypsum board itself and the differences in the physical and chemical properties of different materials, they show different adsorption characteristics, that is, the waste gypsum board can effectively adsorb phosphorus after pyrolysis, while the CaSO4·2H2O agent and phosphogypsum have no significant adsorption effect on phosphorus before and after pyrolysis. Desulfurized gypsum itself has a good adsorption effect on phosphorus, but low-temperature pyrolysis has no synergistic effect on it. This shows that the pyrolysis product of the gypsum board in the present invention can adsorb phosphorus in the aqueous solution, and has good application prospects in the fields of phosphorus pollution in water bodies and phosphorus recovery and reuse.

[0102] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A phosphorus adsorbent, characterized in that: The phosphorus adsorbent is used for phosphorus pollution and phosphorus recovery in water bodies; The preparation method of the phosphorus adsorbent comprises the following steps: S1, drying the waste gypsum to remove moisture; S2, crushing the dried gypsum and sieving it; S3, pyrolyzing the crushed gypsum at low temperature under an inert gas atmosphere to obtain a pyrolysis product; S4, grinding and sieving the pyrolysis product to obtain a phosphorus adsorbent; The SO3 content in the waste gypsum is less than 47%, the CaO content is greater than 45%, and the Al2O3 content is less than 1%; The waste gypsum is construction waste gypsum; The heating rate of the low-temperature pyrolysis is 5°C / min-10°C / min, the pyrolysis temperature is 150°C-300°C, and the pyrolysis time is 1 h-4 h.

2. The method for preparing a phosphorus adsorbent according to claim 1, characterized in that: The drying temperature is 100° C.-120° C., and the drying time is 24 h.

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