A modified phosphogypsum composite material and its preparation method and application

Abstract

The present invention belongs to the technical field of wastewater phosphorus removal, and provides a modified phosphogypsum composite material, a preparation method and an application thereof. The present invention comprises the following steps: after the treated phosphogypsum and a quaternary ammonium salt cationic surfactant are mixed, mechanical activation is performed to obtain the modified phosphogypsum composite material. The present invention mixes the phosphogypsum and cetyltrimethylammonium bromide, and adopts a mechanical activation method. Under the action of mechanical force, the positively charged ions of cetyltrimethylammonium bromide can not only exchange ions with inorganic cations on the surface of the phosphogypsum, but also strongly interact with the negatively charged surface of the phosphogypsum through electrostatic attraction and hydrophilic action, and change the original properties of the surface of the phosphogypsum, that is, the hydrophilicity is converted into hydrophobicity, and the phosphogypsum is combined with the surfactant, so as to realize the composite optimization of the physical surface and chemical properties of the modified material, and can efficiently purify the wastewater of the phosphorus chemical industry under high concentration.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater phosphorus removal, and specifically relates to a modified phosphogypsum composite material and a preparation method and application thereof. Background Art

[0002] Phosphogypsum (PG) is an industrial solid waste produced by phosphorus chemical enterprises in the wet process of producing phosphoric acid. Every ton of phosphoric acid produced will produce 4-5 tons of phosphogypsum. Its main components are CaSO4·2H2O and a small amount of impurities composed of insoluble compounds. The color varies according to its specific components.

[0003] Grayish white or grayish black. The reaction formula for the formation of phosphogypsum is as follows:

[0004] Ca5F(PO4)3+5H2SO4+2H2O→3PO4+5CaSO4·2H2O+HF↑.

[0005] With the continuous expansion of the scale of the phosphorus chemical industry, the accumulation of phosphogypsum has continued to increase. At present, the annual output of phosphogypsum has reached 8000wt, but its utilization rate is only 40%. The large amount of stockpiled phosphogypsum not only occupies land, but also pollutes the local air, water and other environments, and also affects the regional hydrodynamic conditions, causing changes in groundwater levels, and even changing the local natural landscape and ecosystem. In addition, it will cause economic waste. In phosphoric acid production, up to 10% of the cost is used for the transportation and storage of phosphogypsum. Exploring new high-value utilization methods for phosphogypsum and improving resource utilization are the problems that the current phosphorus chemical industry urgently needs to solve. And with the continuous expansion of the scale of the phosphorus chemical industry, the wastewater discharge of phosphorus chemical industry is the main source of phosphorus pollution in water bodies. Phosphorus is an essential element for the growth of organisms, but excessive phosphorus in water can cause eutrophication of water bodies, leading to the rapid reproduction of plankton such as algae, reducing dissolved oxygen in water bodies, and deteriorating water quality, resulting in the death of a large number of organisms in water bodies. In recent years, how to reduce and remove phosphorus from the source of phosphorus chemical enterprises has become a hot topic in the field of water treatment.

[0006] At present, the main treatment methods for phosphorus-containing wastewater include ion exchange, chemical precipitation, adsorption, etc. Among them, the ion exchange method has a high removal rate, but the ion exchange resin is expensive and the regeneration process is complicated; although the chemical precipitation method is low-cost and simple to operate, a large amount of aluminum salts or other flocculants need to be added during the phosphorus removal process, which is easy to cause secondary pollution, and a large amount of water-containing sludge will be produced after phosphorus removal, which is difficult to handle. The adsorption method generally uses materials with a large specific surface area and a suitable pore structure to adsorb phosphorus in the water body. However, it faces the problems of high material cost and poor effect. Seeking a more efficient, convenient and cheap method for removing phosphorus from wastewater has become a hot topic of concern. Application No. CN202311212947.4 discloses a method for preparing a phosphorus selective adsorption electrode for low-concentration phosphorus wastewater, using biomass raw materials to prepare biochar and then nitrogen modification, and then preparing a phosphorus selective adsorption electrode with iron source, lanthanum source and ammonia water, which has significant affinity and excellent adsorption capacity for phosphorus. However, its preparation is cumbersome and the process is costly, making it difficult to apply on a large scale in actual production; the patent with application number CN202410299921.6 discloses a modified zeolite dephosphorization adsorbent and its preparation method and application in phosphorus-containing wastewater dephosphorization. The zeolite is pretreated with hydrochloric acid and then modified with manganese alkali solution, cleaned and dried to obtain the adsorbent. The raw materials of the adsorbent are easy to obtain and the cost is low, but it only has excellent dephosphorization ability for low-concentration phosphorus-containing wastewater; the patent with application number 202310251954.9 discloses a method for making phosphorus adsorption materials by high-pressure heating after modification of phosphorus tailings. Although the process is relatively simplified and the cost has been reduced, its phosphorus adsorption capacity is only 0.14mg / g~0.17mg / g, which is difficult to meet the purification needs of phosphorus chemical wastewater with high phosphorus concentration. Based on this, how to develop a high-phosphorus concentration wastewater dephosphorization material with simple process, low cost and excellent effect has become a problem that urgently needs to be solved. Summary of the invention

[0007] The purpose of the present invention is to provide a modified phosphogypsum composite material and a preparation method and application thereof, so as to solve the purification of phosphorus chemical wastewater with high phosphorus concentration. Through the method of mechanical activation, under the action of mechanical force, phosphogypsum and surfactant are combined together, the main component of calcium sulfate of phosphogypsum is broken into sulfate and calcium ions, the adsorption performance is increased, and the positively charged ions of quaternary ammonium salt cationic surfactant can not only exchange ions with inorganic cations on the surface of phosphogypsum, but also interact strongly with the negatively charged surface of phosphogypsum through electrostatic attraction and hydrophilic effect, and change the original properties of the surface of phosphogypsum, that is, the hydrophilicity is converted into hydrophobicity, which can greatly improve its adsorption capacity for pollutants.

[0008] In order to achieve the above purpose, the technical solution adopted in this application is:

[0009] The first object of the present invention is to provide a method for preparing a modified phosphogypsum composite material, comprising the following steps: mixing the treated phosphogypsum and a quaternary ammonium salt cationic surfactant, and then performing mechanical activation. During the mechanical activation process, ion exchange occurs between the phosphogypsum and the quaternary ammonium salt cationic surfactant, so that the phosphogypsum is converted into a hydrophobic material, thereby obtaining a modified phosphogypsum composite material.

[0010] Furthermore, the mass ratio of the phosphogypsum to the quaternary ammonium salt cationic surfactant is 10:0.5-5.

[0011] Furthermore, the quaternary ammonium salt cationic surfactant is hexadecyltrimethylammonium bromide.

[0012] Furthermore, the mechanical activation adopts ball milling, the ball milling time is 40min-60min, the ball-to-material ratio is 280-320:10-30, and the ball milling speed is 500r / min-700r / min.

[0013] The further treatment method of phosphogypsum is as follows: washing the phosphogypsum with water, drying it, and then crushing and screening it to obtain the treated phosphogypsum.

[0014] The further drying temperature is 40°C to 60°C, the drying time is 3h to 4h, and the particle size of the phosphogypsum after screening is 40 mesh to 80 mesh.

[0015] The second object of the present invention is to provide a modified phosphogypsum composite material prepared by the above preparation method.

[0016] The third object of the present invention is to provide the use of the modified phosphogypsum composite material as an adsorbent for removing phosphorus from phosphorus-containing wastewater.

[0017] Furthermore, the modified phosphogypsum composite material is placed in phosphorus-containing wastewater at room temperature, and after shaking and stirring, it is allowed to stand and filter to obtain the modified phosphogypsum composite material after adsorption, wherein the phosphorus concentration in the phosphorus-containing wastewater is 200 mgP / L, and the addition amount of the modified phosphogypsum composite material is 3g to 5g / 100mL.

[0018] In addition, the present invention also provides the use of the modified phosphogypsum composite material in the preparation of fertilizers, and the modified phosphogypsum composite material after adsorbing phosphorus in phosphorus-containing wastewater is used as a slow-release phosphate fertilizer.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention mixes phosphogypsum and cetyltrimethylammonium bromide and adopts a mechanical activation method. Under the action of mechanical force, the positively charged ions of cetyltrimethylammonium bromide can not only exchange ions with inorganic cations on the surface of phosphogypsum, but also strongly interact with the negatively charged surface of phosphogypsum through electrostatic attraction and hydrophilic effect, and change the original properties of the surface of phosphogypsum, that is, the hydrophilicity is converted into hydrophobicity, and the phosphogypsum is combined with the surfactant, thereby realizing the composite optimization of the physical surface and chemical properties of the modified material, and can efficiently purify phosphorus chemical industry wastewater at high concentration.

[0021] 2. The present invention mechanically activates phosphogypsum to change the physical and chemical properties and crystal structure of phosphogypsum, reduce the particle size of the material, increase the specific surface area, increase the degree of disorder of the crystal structure, and then transform to an amorphous state, and chemical changes occur accompanied by the breaking of chemical bonds. Under the action of mechanical force, a series of physical and chemical reactions occur between substances therein, thereby generating a new substance. In addition to increasing the specific surface area of ​​phosphogypsum to increase the adsorption sites of phosphate ions, under the action of mechanical force, the main component of phosphogypsum, calcium sulfate, breaks into sulfate and calcium ions, and these abundant calcium ions are excellent phosphate ion adsorbents. Through a simple modification method, the physical and chemical aspects of phosphogypsum are coordinated and optimized, thereby improving its adsorption capacity for phosphate ions.

[0022] 3. The present invention uses phosphogypsum as the main raw material, has low cost and simple process, realizes high-value utilization of phosphogypsum while treating wastewater, and the material after water treatment can also be used as phosphate fertilizer, realizing the recycling of resources while treating waste with waste. When 4g of modified phosphogypsum composite material is added per 100mL, the removal rate reaches more than 98%, and the phosphorus content in the final wastewater is far less than the minimum 15mg / L specified in the "GB15580-2011 Phosphate Fertilizer Industry Water Pollutant Emission Standard", and the material can be used for slow-release phosphate fertilizer application at the agricultural production end after drying after treating sewage, realizing the recycling of phosphorus resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a particle size analysis diagram of the modified phosphogypsum composite material of Example 1 of the present invention.

[0024] Figure 2 The X-ray diffraction diagrams of the modified phosphogypsum composite materials of Example 3, Comparative Example 2 and Comparative Example 3 of the present invention are shown in FIG. Figure 2 (a) is Comparative Example 2, (b) is Example 3, and (c) is Comparative Example 3.

[0025] Figure 3 It is the phosphorus removal rate of the phosphogypsum composite materials of Examples 1-8 and Comparative Examples 1-4 of the present invention in wastewater containing 200 mg / L of phosphorus.

[0026] Figure 4 It is the phosphorus removal rate of the phosphogypsum composite materials of Examples 1-8 and Comparative Examples 1-4 of the present invention in wastewater containing 200 mg / L of phosphorus.

[0027] Figure 5 It is the phosphorus removal rate of the 5g examples 1-8 and comparative examples 1-4 phosphogypsum composite materials of the present invention in wastewater containing 200 mg / L phosphorus. DETAILED DESCRIPTION

[0028] The following will be combined with the data and drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods. The phosphogypsum in the present invention was purchased from Yunnan Phosphate Group, and the surfactant was purchased from McLean Company.

[0030] The present invention provides a method for preparing a modified phosphogypsum composite material, comprising the following steps:

[0031] S1, washing the phosphogypsum with water and drying it at 40°C to 60°C for 3h to 4h, then crushing and screening it, the particle size of the phosphogypsum after screening is 40 mesh to 80 mesh, and obtaining the treated phosphogypsum;

[0032] S2. After the treated phosphogypsum and quaternary ammonium salt cationic surfactant are mixed, mechanical activation is performed. During the mechanical activation process, ion exchange occurs between the phosphogypsum and the quaternary ammonium salt cationic surfactant, so that the phosphogypsum is converted into a hydrophobic state, thereby obtaining a modified phosphogypsum composite material.

[0033] Mechanical activation refers to the process of grinding, compressing, impacting, rubbing, etc. a substance through mechanical force, so that the physical and chemical properties and crystal structure of the substance change, the particle size of the substance becomes smaller, the specific surface area increases, the degree of disorder of the crystal structure increases, and then changes to an amorphous state, and chemical changes occur with the breaking of chemical bonds. When grinding two or more substances, a series of physical and chemical reactions occur between the substances under the action of mechanical force, thereby producing a new substance. Based on this, the present invention mixes phosphogypsum and hexadecyltrimethylammonium bromide, and adopts a mechanical activation method. Under the action of mechanical force, the positively charged ions of hexadecyltrimethylammonium bromide can exchange ions with inorganic cations on the surface of phosphogypsum, and can interact strongly with the negatively charged surface of phosphogypsum through electrostatic attraction and hydrophilic action, and change the original properties of the surface of phosphogypsum, that is, hydrophilicity is converted into hydrophobicity, and phosphogypsum is combined with a surfactant, so as to achieve the composite optimization of the physical surface and chemical properties of the modified material, and can efficiently purify phosphorus chemical industry wastewater at high concentrations. The prepared phosphogypsum composite material has excellent phosphorus wastewater purification ability, and the preparation process is simple, low cost, and has broad industrialization potential.

[0034] In a specific embodiment, the mass ratio of the phosphogypsum and the quaternary ammonium salt cationic surfactant is 10:0.5-5. As a preferred embodiment of the present invention, the mass ratio of the phosphogypsum and the quaternary ammonium salt cationic surfactant can be any ratio between 10:0.5-5. More preferably, the mass ratio of the phosphogypsum and the quaternary ammonium salt cationic surfactant is 10:2; the quaternary ammonium salt cationic surfactant is hexadecyltrimethylammonium bromide. The use of a single surfactant is difficult to achieve the optimal adsorption effect on the one hand, and on the other hand, there is a problem of high cost. The present invention uses a mechanical activation method to efficiently compound the phosphogypsum with a surfactant, and a series of physical and chemical reactions occur between the phosphogypsum and the quaternary ammonium salt cationic surfactant, and the original properties of the phosphogypsum surface are changed, which greatly improves its adsorption capacity for pollutants. However, the addition of too much surfactant blocks the adsorption pore size of the phosphogypsum surface, reduces the specific surface area, and thus leads to a reduction in phosphorus removal rate.

[0035] In a specific embodiment, the mechanical activation adopts ball milling, the ball milling time is 40min-60min, the ball-to-material ratio is 280-320:10-30, and the ball milling speed is 500r / min-700r / min. As a preferred solution of the present invention, the ball milling time can be any value between 40min-60min, the ball-to-material ratio can be any ratio between 280-320:10-30, and the ball milling speed is any value between 500r / min-700r / min. In the process of mechanical activation of phosphogypsum by the invention, the physical and chemical properties and crystal structure of phosphogypsum are changed, the particle size of the material particles becomes smaller, the specific surface area increases, the degree of disorder of the crystal structure increases, and then it changes to an amorphous state, and chemical changes occur accompanied by the breaking of chemical bonds. Under the action of mechanical force, a series of physical and chemical reactions occur between the substances therein, thereby producing a new substance. In addition to increasing the specific surface area of ​​phosphogypsum to increase the adsorption sites of phosphate ions, under the action of mechanical force, the main component of phosphogypsum, calcium sulfate, breaks into sulfate and calcium ions, and these abundant calcium ions are excellent phosphate ion adsorbents. Through a simple modification method, the physical and chemical aspects of phosphogypsum are synergistically optimized, thereby improving its adsorption capacity for phosphate ions.

[0036] On the other hand, the present invention provides a modified phosphogypsum composite material prepared by the above preparation method.

[0037] The third object of the present invention is to provide the application of the modified phosphogypsum composite material as an adsorbent in phosphorus removal from phosphorus-containing wastewater. The modified phosphogypsum composite material is placed in phosphorus-containing wastewater at room temperature, and after shaking and stirring, it is allowed to stand and filter to obtain the modified phosphogypsum composite material after adsorption, wherein the phosphorus concentration in the phosphorus-containing wastewater is 200 mgP / L, and the addition amount of the modified phosphogypsum composite material is 3g-5g / 100mL; the stirring speed is 150r / min-250r / min, and the time is 1h-2h. The mechanical activation method is used to combine phosphogypsum with a surfactant, and the composite optimization of the physical surface and chemical properties of the modified material is achieved, which can efficiently purify phosphorus chemical industry wastewater at high concentrations. When 4g of the modified phosphogypsum composite material is added per 100mL, a removal rate of more than 98% is achieved, and the phosphorus content in the final wastewater is far less than the minimum 15mg / L specified in the "GB15580-2011 Phosphate Fertilizer Industry Water Pollutant Discharge Standard".

[0038] In addition, the present invention also provides the use of the modified phosphogypsum composite material in the preparation of fertilizers, wherein the modified phosphogypsum composite material after adsorbing phosphorus in phosphorus-containing wastewater is used as a slow-release phosphate fertilizer. After treating the sewage, the material can be dried and applied to the application of slow-release phosphate fertilizer at the agricultural production end, thereby realizing the recycling of phosphorus resources.

[0039] The invention is further described below through specific examples.

[0040] Example 1

[0041] A method for preparing a modified phosphogypsum composite material comprises the following steps:

[0042] S1, washing the phosphogypsum with water and drying it at 60° C. for 3 h, then crushing it and passing it through an 80-mesh sieve to obtain treated phosphogypsum powder;

[0043] S2, weighing 0.5 g of hexadecyltrimethylammonium bromide powder and 10 g of the treated phosphogypsum powder respectively, and then mixing them evenly to obtain a composite powder;

[0044] S3. Add the composite powder obtained above into a planetary ball mill for mechanical activation. Set the ball milling time to 40 min, the ball-to-material ratio to 300:20, and the rotation speed to 600 r / min. After the mechanical activation, a modified phosphogypsum composite material is obtained.

[0045] Example 2

[0046] A method for preparing a modified phosphogypsum composite material comprises the following steps:

[0047] S1, washing the phosphogypsum with water and drying it at 60° C. for 3 h, then crushing it and passing it through an 80-mesh sieve to obtain treated phosphogypsum powder;

[0048] S2. Weigh 1 g of hexadecyltrimethylammonium bromide powder and 10 g of the treated phosphogypsum powder respectively, and then mix them evenly to obtain a composite powder;

[0049] S3. Add the composite powder obtained above into a planetary ball mill for mechanical activation. Set the ball milling time to 40 min, the ball-to-material ratio to 300:20, and the rotation speed to 600 r / min. After the mechanical activation, a modified phosphogypsum composite material is obtained.

[0050] Example 3

[0051] A method for preparing a modified phosphogypsum composite material comprises the following steps:

[0052] S1, washing the phosphogypsum with water and drying it at 60° C. for 3 h, then crushing it and passing it through an 80-mesh sieve to obtain treated phosphogypsum powder;

[0053] S2. Weigh 2 g of hexadecyltrimethylammonium bromide powder and 10 g of the treated phosphogypsum powder respectively, and then mix them evenly to obtain a composite powder;

[0054] S3. Add the composite powder obtained above into a planetary ball mill for mechanical activation. Set the ball milling time to 40 min, the ball-to-material ratio to 300:20, and the rotation speed to 600 r / min. After the mechanical activation, a modified phosphogypsum composite material is obtained.

[0055] Example 4

[0056] A method for preparing a modified phosphogypsum composite material comprises the following steps:

[0057] S1, washing the phosphogypsum with water and drying it at 60° C. for 3 h, then crushing it and passing it through an 80-mesh sieve to obtain treated phosphogypsum powder;

[0058] S2. Weigh 3 g of hexadecyltrimethylammonium bromide powder and 10 g of the treated phosphogypsum powder respectively, and then mix them evenly to obtain a composite powder;

[0059] S3. Add the composite powder obtained above into a planetary ball mill for mechanical activation. Set the ball milling time to 40 min, the ball-to-material ratio to 300:20, and the rotation speed to 600 r / min. After the mechanical activation, a modified phosphogypsum composite material is obtained.

[0060] Example 5

[0061] A method for preparing a modified phosphogypsum composite material comprises the following steps:

[0062] S1, washing the phosphogypsum with water and drying it at 60° C. for 3 h, then crushing it and passing it through an 80-mesh sieve to obtain treated phosphogypsum powder;

[0063] S2, weighing 4 g of hexadecyltrimethylammonium bromide powder and 10 g of the treated phosphogypsum powder respectively, and then mixing them evenly to obtain a composite powder;

[0064] S3. Add the composite powder obtained above into a planetary ball mill for mechanical activation. Set the ball milling time to 40 min, the ball-to-material ratio to 300:20, and the rotation speed to 600 r / min. After the mechanical activation, a modified phosphogypsum composite material is obtained.

[0065] Example 6

[0066] A method for preparing a modified phosphogypsum composite material comprises the following steps:

[0067] S1, washing the phosphogypsum with water and drying it at 60° C. for 3 h, then crushing it and passing it through a 60-mesh sieve to obtain treated phosphogypsum powder;

[0068] S2, weighing 5 g of hexadecyltrimethylammonium bromide powder and 10 g of the treated phosphogypsum powder respectively, and then mixing them evenly to obtain a composite powder;

[0069] S3. Add the composite powder obtained above into a planetary ball mill for mechanical activation. Set the ball milling time to 40 min, the ball-to-material ratio to 300:20, and the rotation speed to 600 r / min. After the mechanical activation, a modified phosphogypsum composite material is obtained.

[0070] Example 7

[0071] A method for preparing a modified phosphogypsum composite material comprises the following steps:

[0072] S1, washing the phosphogypsum with water and drying it at 60° C. for 3 h, then crushing it and passing it through an 80-mesh sieve to obtain treated phosphogypsum powder;

[0073] S2. Weigh 2 g of hexadecyltrimethylammonium bromide powder and 10 g of the treated phosphogypsum powder respectively, and then mix them evenly to obtain a composite powder;

[0074] S3. Add the composite powder obtained above into a planetary ball mill for mechanical activation. Set the ball milling time to 40 min, the ball-to-material ratio to 300:10, and the rotation speed to 600 r / min. After the mechanical activation, a modified phosphogypsum composite material is obtained.

[0075] Example 8

[0076] A method for preparing a modified phosphogypsum composite material comprises the following steps:

[0077] S1, washing the phosphogypsum with water and drying it at 60° C. for 3 h, then crushing it and passing it through an 80-mesh sieve to obtain treated phosphogypsum powder;

[0078] S2. Weigh 2 g of hexadecyltrimethylammonium bromide powder and 10 g of the treated phosphogypsum powder respectively, and then mix them evenly to obtain a composite powder;

[0079] S3. Add the composite powder obtained above into a planetary ball mill for mechanical activation. Set the ball milling time to 40 min, the ball-to-material ratio to 300:30, and the rotation speed to 600 r / min. After the mechanical activation, a modified phosphogypsum composite material is obtained.

[0080] Comparative Example 1

[0081] A method for preparing phosphogypsum material comprises the following steps:

[0082] The phosphogypsum was washed with water and dried at 60°C for 3 hours, then crushed and passed through an 80-mesh sieve to obtain the treated phosphogypsum powder.

[0083] Comparative Example 2

[0084] A method for preparing a modified phosphogypsum material comprises the following steps:

[0085] S1, washing the phosphogypsum with water and drying it at 60° C. for 3 h, then crushing it and passing it through an 80-mesh sieve to obtain the treated phosphogypsum powder;

[0086] S2. Weigh the treated phosphogypsum powders respectively and add them into a planetary ball mill for mechanical activation. Set the ball milling time to 40 min, the ball-to-material ratio to 300:20, and the rotation speed to 600 r / min. After the mechanical activation, the modified phosphogypsum material is obtained.

[0087] Comparative Example 3

[0088] A method for preparing a modified phosphogypsum composite material comprises the following steps:

[0089] S1, washing the phosphogypsum with water and drying it at 60° C. for 3 h, then crushing it and passing it through an 80-mesh sieve to obtain the treated phosphogypsum powder;

[0090] S2. Weigh 2 g of hexadecyltrimethylammonium bromide powder and 10 g of the treated phosphogypsum powder respectively, and then mix them evenly to obtain a composite powder;

[0091] S3. Add the composite powder obtained above into a planetary ball mill for mechanical activation. Set the ball milling time to 40 min, the ball-to-material ratio to 300:20, and the rotation speed to 600 r / min. After the mechanical activation, a modified phosphogypsum composite material is obtained.

[0092] Comparative Example 4

[0093] A method for preparing a modified phosphogypsum composite material comprises the following steps:

[0094] S1, washing the phosphogypsum with water and drying it at 60° C. for 3 h, then crushing it and passing it through an 80-mesh sieve to obtain treated phosphogypsum powder;

[0095] S2. Weigh 2 g of hexadecyltrimethylammonium bromide powder and 10 g of the treated phosphogypsum powder respectively, and then mix them evenly to obtain a composite powder;

[0096] S3. Add the composite powder obtained above into a hydrothermal shaker, shake at a constant temperature of 45°C and 300 r / min for 2 hours, dry the obtained material at 80°C for 24 hours, and grind it through a 60-mesh sieve to obtain a modified phosphogypsum composite material.

[0097] The modified phosphogypsum composite materials prepared in Examples 1-8 have similar structures and similar effects. The modified phosphogypsum composite material prepared in Example 3 is taken as an example to illustrate the structural performance of the modified phosphogypsum composite material prepared in Example 3. The results are as follows.

[0098] Figure 1 This is a particle size analysis diagram of the modified phosphogypsum composite material of Example 3 of the present invention. Figure 1 As shown, the particle size of phosphogypsum after ball milling is mainly concentrated in 5-10 microns, achieving a larger specific surface area, which is significantly improved compared with the 10-100 microns of conventional phosphogypsum.

[0099] The modified phosphogypsum composite material of Example 3, the modified phosphogypsum material of Comparative Example 2, and the modified phosphogypsum composite material of Comparative Example 3 were structurally analyzed to compare the modification effects of phosphogypsum under different processes. Figure 2 The X-ray diffraction diagrams of the modified phosphogypsum composite materials of Example 3, Comparative Example 2 and Comparative Example 3 of the present invention are shown in FIG. Figure 2 (a) is Comparative Example 2, (b) is Example 3, and (c) is Comparative Example 3. Figure 2 As shown, it can be seen that the structural composition of Comparative Example 2 is similar to that of Comparative Example 3, which is mainly composed of phosphogypsum, and no obvious surfactant composition is observed, while Example 3 has an obvious hexadecyltrimethylammonium bromide peak, indicating that ball milling can fully compound phosphogypsum with surfactants, and the effect is better than hydrothermal treatment.

[0100] Weigh 3g, 4g and 5g of the modified phosphogypsum composite material prepared in Examples 1-8, the phosphogypsum treated in Comparative Example 1, the modified phosphogypsum material in Comparative Example 2, the modified phosphogypsum composite material in Comparative Example 3 and the modified phosphogypsum composite material in Comparative Example 4, respectively, and then add 100mL of 200mg / L phosphorus-containing water (prepared with potassium dihydrogen phosphate) to simulate high-concentration phosphorus-containing wastewater, shake at 200r / min for 1h, then let stand for 1h and filter, take the clear liquid and use ammonium molybdate spectrophotometry to determine the phosphorus concentration therein, calculate the removal rate of phosphorus in the wastewater by the phosphogypsum composite material, and the removal rate calculation formula is: (C0-C1) / C0×100%, where C0 is the initial phosphorus concentration in the phosphorus-containing wastewater, in mg / L, and C1 is the phosphorus content of the wastewater after adsorption, in mg / L. The results are shown in Tables 1-3 and Figure 2-Figure 4 shown.

[0101] Table 1 Phosphorus removal rate of 3g phosphogypsum composite material added to 100mL wastewater containing 200mg / L phosphorus

[0102] Phosphorus content of wastewater after adsorption (mg / L) Phosphorus removal rate in wastewater (%) Example 1 68.15 65.93 Example 2 37.39 81.31 Example 3 7.16 96.42 Example 4 30.28 84.86 Example 5 62.14 68.93 Example 6 86.25 56.88 Example 7 10.21 94.895 Example 8 7.04 96.48 Comparative Example 1 194.21 2.9 Comparative Example 2 156.47 21.77 Comparative Example 3 113.41 43.3 Comparative Example 4 164.2 17.9

[0103] Table 2 Phosphorus removal rate of 4g phosphogypsum composite material added to 100mL wastewater containing 200mg / L phosphorus

[0104]

[0105]

[0106] Table 3 Phosphorus removal rate of 5g phosphogypsum composite material added to 100mL wastewater containing 200mg / L phosphorus

[0107] Phosphorus content of wastewater after adsorption (mg / L) Phosphorus removal rate in wastewater (%) Example 1 27.71 86.15 Example 2 12.69 93.66 Example 3 4.97 97.52 Example 4 6.39 96.81 Example 5 7.68 96.16 Example 6 16.39 91.81 Example 7 4.61 97.695 Example 8 7.54 96.23 Comparative Example 1 180.42 9.79 Comparative Example 2 134.64 32.68 Comparative Example 3 98.71 50.65 Comparative Example 4 141.6 29.2

[0108] Figure 3 The phosphorus removal rate of the phosphogypsum composite materials of Examples 1-8 and Comparative Examples 1-4 of the present invention in wastewater containing 200 mg / L phosphorus; Figure 4 The phosphorus removal rate of the phosphogypsum composite materials of Examples 1-6 and Comparative Examples 1-4 of the present invention in wastewater containing 200 mg / L phosphorus; Figure 5 The phosphorus removal rate of 5g of the phosphogypsum composite material of Examples 1-8 and Comparative Examples 1-4 in wastewater containing 200mg / L phosphorus is shown in Tables 1-3 and Figure 3-5 As shown, with the increase of the addition ratio of hexadecyltrimethylammonium bromide, the phosphorus removal rate of wastewater shows a trend of first increasing and then decreasing. This may be because the addition of a small amount of surfactant can achieve efficient compounding with phosphogypsum, while the addition of too much surfactant blocks the adsorption pore size of the surface of phosphogypsum, and the specific surface area is reduced, which leads to a decrease in phosphorus removal rate. Considering the comprehensive raw material cost and the actual effect of the above table, the phosphogypsum composite material prepared in Example 3 has the best comprehensive effect when 4g is added per 100mL in high-concentration phosphorus-containing wastewater, reaching a removal rate of more than 98%, and the phosphorus content in the final wastewater is far less than the minimum 15mg / L specified in the "GB15580-2011 Phosphate Fertilizer Industry Water Pollutant Discharge Standard", and the material can be used for the application of slow-release phosphate fertilizers at the agricultural production end after drying after treating sewage, realizing the recycling of phosphorus resources.

[0109] It should be noted that when the present invention involves a numerical range, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes a preferred embodiment. Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the attached claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0110] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing a modified phosphogypsum composite material, characterized in that: The following steps are involved: The treated phosphogypsum and the quaternary ammonium salt cationic surfactant are mixed and then mechanically activated. During the mechanical activation process, ion exchange occurs between the phosphogypsum and the quaternary ammonium salt cationic surfactant, so that the phosphogypsum is converted into a hydrophobic state, thereby obtaining a modified phosphogypsum composite material; The mechanical activation is carried out by ball milling, the ball milling time is 40 min to 60 min, the ball-to-material ratio is 280 to 320:10 to 30, and the ball milling speed is 500 r / min to 700 r / min; The quaternary ammonium salt cationic surfactant is hexadecyltrimethylammonium bromide.

2. The method for preparing the modified phosphogypsum composite material according to claim 1, characterized in that: The mass ratio of the phosphogypsum to the quaternary ammonium salt cationic surfactant is 10:0.5-5.

3. The method for preparing the modified phosphogypsum composite material according to claim 1, characterized in that: The specific method of treating phosphogypsum is: washing the phosphogypsum with water, drying it, and then crushing and screening it to obtain treated phosphogypsum.

4. The method for preparing the modified phosphogypsum composite material according to claim 3, characterized in that: The drying temperature is 40 ℃ ~ 60 ℃, the drying time is 3 h ~ 4 h, and the particle size of the phosphogypsum after screening is 40 mesh ~ 80 mesh.

5. A modified phosphogypsum composite material prepared by the preparation method according to any one of claims 1 to 4.

6. Use of the modified phosphogypsum composite material according to claim 5 as an adsorbent for removing phosphorus from phosphorus-containing wastewater.

7. The use according to claim 6, characterized in that: The modified phosphogypsum composite material is placed in phosphorus-containing wastewater at room temperature, and after shaking and stirring, it is allowed to stand and filtered to obtain the modified phosphogypsum composite material after adsorption. The phosphorus concentration in the phosphorus-containing wastewater is 200 mg / L, and the addition amount of the modified phosphogypsum composite material is 3 g to 5 g / 100 mL.

8. Use of the modified phosphogypsum composite material according to claim 5 in preparing fertilizers, characterized in that: The modified phosphogypsum composite material after adsorbing phosphorus from phosphorus-containing wastewater is used as a slow-release phosphate fertilizer.

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