Multi-dimensional heavy metal directionally stabilized phosphogypsum roadbed material and preparation method thereof

Abstract

The invention relates to the technical field of ardealite roadbed materials, in particular to a multi-dimensional heavy metal directionally stabilized ardealite roadbed material and a preparation method thereof, and the material comprises the following raw materials in parts by mass: 100-120 parts of ardealite, 20-30 parts of slag powder, 120-150 parts of aggregate, 3-8 parts of intelligent microcapsules, 3-5 parts of an alkali activator and 15-20 parts of water. The heavy metal can be effectively adsorbed for a long time by designing a multiple adsorption structure, the first layer in the microcapsule is magnesium phosphate cement, phosphate radicals released by the magnesium phosphate cement preliminarily solidify the heavy metal, then along with gradual degradation of polylactic acid in a roadbed material, hydroxyapatite-loaded charcoal in the microcapsule can be used for adsorbing the heavy metal in the roadbed material, and the heavy metal can be effectively adsorbed by the hydroxyapatite-loaded charcoal. The heavy metal can be further fixed, and the heavy metal can be effectively treated for a long time.

Description

Technical Field

[0001] This invention relates to the field of phosphogypsum roadbed material technology, specifically a multidimensional heavy metal-oriented stabilized phosphogypsum roadbed material and its preparation method. Background Technology

[0002] Phosphogypsum is a solid waste generated by phosphate chemical companies during the production of phosphoric acid. Its main component is calcium sulfate dihydrate (CaSO4·2H2O), and typically 4-5 tons of phosphogypsum are produced for every ton of phosphoric acid produced. It is characterized by its fine powdery texture, grayish-white color, strong acidity (pH between 1 and 4.5), and the presence of impurities such as fluorides and phosphorus pentoxide. The stockpiling of phosphogypsum can be harmful to the environment, making its resource utilization particularly important. It is mainly used in cement, gypsum building materials, and other fields.

[0003] Therefore, it is particularly important to develop a roadbed material that can reduce the heavy metal content of phosphogypsum. Current technologies generally involve adding heavy metal curing agents to the roadbed material to fix the heavy metals. However, in existing technologies, it is difficult for heavy metal curing agents to achieve multi-stage slow release, making it difficult to maintain the adsorption and fixation of heavy metals efficiently and for a long time.

[0004] In response to the problems mentioned in the background art, those skilled in the art propose a multidimensional heavy metal-oriented stabilized phosphogypsum roadbed material and its preparation method. Summary of the Invention

[0005] The purpose of this invention is to provide a multidimensional heavy metal-oriented stabilized phosphogypsum roadbed material and its preparation method, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A multidimensional heavy metal-oriented stabilized phosphogypsum roadbed material, comprising the following raw materials by weight: 100-120 parts phosphogypsum, 20-30 parts slag powder, 120-150 parts aggregate, 3-8 parts intelligent microcapsules, 3-5 parts alkaline activator, and 15-20 parts water; The preparation method of the intelligent microcapsule includes the following steps: S101. Disperse biochar in calcium nitrate solution to obtain a mixture; S102. Add ammonium hydrogen phosphate solution dropwise to the mixture obtained in step S101, adjust the pH to 9-11 by adding ammonia water dropwise, heat to 50-80℃, react for 0.5-1h, then filter, wash the filtered product with deionized water until neutral, and calcine at 500-700℃ for 5-10h to obtain biochar loaded with hydroxyapatite. S103. The biochar loaded with hydroxyapatite obtained in step S102 is soaked in mercaptoacetic acid solution for 1-2 hours, then filtered, and the filtered product is washed with deionized water and then vacuum dried. S104. The biochar loaded with hydroxyapatite, which has been treated in step S103, is placed into heated and melted polylactic acid, and polylactic acid-coated biochar particles are obtained by using a capsule machine. S105. The polylactic acid-coated biochar particles obtained in step S104 are placed in a 0.05-0.1 mol / L sodium hydroxide solution for 5-10 min, then filtered, and the filtered product is washed with deionized water and then vacuum dried. S106. The polylactic acid-coated biochar particles treated in step S105 are mixed with magnesium phosphate cement, and carboxymethyl cellulose solution is added. The mixture is stirred continuously for 1-3 hours, and then vacuum dried to obtain the core material. S107. The core material obtained in step S106 is added to an aqueous solution of sodium alginate to obtain a suspension. The suspension is then added dropwise to a mixed solution of calcium chloride, chitosan and acetic acid through a dropper. The mixture is reacted for 30-50 minutes, then filtered. The filtered product is then vacuum dried to obtain smart microcapsules.

[0007] Furthermore, in step S101, the concentration of calcium nitrate in the calcium nitrate solution is 0.2-0.5 wt%, the mass ratio between biochar and calcium nitrate solution is 1:(40-80), and the particle size of biochar is 50-150 mesh.

[0008] Furthermore, in step S102, the concentration of ammonium hydrogen phosphate in the ammonium hydrogen phosphate solution is 0.1-0.4 wt%, and the mass ratio between the ammonium hydrogen phosphate solution in step S102 and the calcium nitrate solution in step S101 is 1:(1-2).

[0009] Furthermore, in step S103, the concentration of mercaptoacetic acid in the mercaptoacetic acid solution is 0.1-1 wt%, and the mass ratio between the biochar loaded with hydroxyapatite and the mercaptoacetic acid solution is 1:15.

[0010] Furthermore, in step S104, the mass ratio between the hydroxyapatite-loaded biochar and polylactic acid treated in step S103 is 1:(3-6).

[0011] Furthermore, in step S105, the mass ratio between the polylactic acid-coated biochar and the sodium hydroxide solution is 1:10.

[0012] Furthermore, in step S106, the mass ratio between the polylactic acid-coated biochar treated in step S105 and the magnesium phosphate cement is (2-3):1, the particle size of the magnesium phosphate cement is 500-1000 mesh, the concentration of the carboxymethyl cellulose solution is 1-2 wt%, and the mass ratio between the carboxymethyl cellulose solution and the magnesium phosphate cement is 1:(2-3).

[0013] Furthermore, in step S107, the concentration of the sodium alginate solution is 5-10 wt%, the mass ratio between the core material and the sodium alginate solution is (0.5-1):1, the concentrations of calcium chloride, chitosan, and acetic acid in the mixed solution of calcium chloride, chitosan, and acetic acid are 2-5 wt%, 15-25 wt%, and 2-4 wt%, respectively, and the mass ratio between the mixed solution of calcium chloride, chitosan, and acetic acid and the sodium alginate solution is (1.5-2):1.

[0014] A method for preparing a multidimensional heavy metal-oriented stabilized phosphogypsum roadbed material, the method comprising the following steps: S1. Add phosphogypsum, slag powder, aggregate and smart microcapsules to water according to the mass ratio, and stir to mix evenly to obtain a mixture; S2. Add alkaline activator to the mixture obtained in step S1 according to the mass fraction, and continue to stir and mix evenly to obtain a slurry; S3. Add the slurry obtained in step S2 into the mold, cure and demold to obtain gypsum roadbed material.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. In this invention, by coating the core material with a material cross-linked with chitosan and hydrogel, the microcapsules release the material inside the core material in the acidic "hot spot" area formed by heavy metal leaching, which can effectively reduce the content of heavy metals in the roadbed material; 2. The core material in this invention includes polylactic acid-coated biochar particles and magnesium phosphate cement. The magnesium phosphate cement is located on the outside of the polylactic acid-coated biochar particles. It releases phosphate ions to form stable phosphate precipitates with heavy metal ions. Over time, the polylactic acid shell begins to degrade, and the biochar loaded with hydroxyapatite inside the polylactic acid shell begins to be exposed. The biochar contains -SH functional groups, which further chelate heavy metal ions. Combined with the hydroxyapatite loaded on its surface, the huge specific surface area of ​​the biochar is used to further fix the heavy metals. The fixation of heavy metals by the core material in this application is completed in multiple steps. The core material is not released all at once, and has a more efficient and longer-lasting fixation ability for heavy metals. Attached Figure Description

[0016] Figure 1 This is a process flow diagram for preparing phosphogypsum roadbed materials according to the present invention; Figure 2This is a process flow diagram of the intelligent microcapsule preparation method of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Please see Figures 1 to 2 The present invention provides: Example 1 A multidimensional heavy metal-oriented stabilized phosphogypsum roadbed material, comprising the following raw materials: 110g phosphogypsum, 25g slag powder, 140g aggregate, 5g smart microcapsules, 4g alkaline activator and 16g water; The preparation method of the above-mentioned intelligent microcapsules includes the following steps: S101. Disperse 10g of biochar with a particle size of 100 mesh into 600g of calcium nitrate solution with a concentration of 0.4wt% to obtain a mixed solution; S102. Add 400g of 0.3wt% ammonium hydrogen phosphate solution to the mixture obtained in step S101, add 28wt% ammonia water to adjust the pH to 10, heat to 60℃, react for 0.8h, then filter, wash the filtered product with deionized water until neutral, and calcine at 650℃ for 7h to obtain biochar loaded with hydroxyapatite. S103. The 10g of hydroxyapatite-loaded biochar obtained in step S102 is soaked in 150g of 0.5wt% mercaptoacetic acid solution for 1.5h, then filtered, and the filtered product is washed with deionized water and then vacuum dried. S104. 8g of biochar loaded with hydroxyapatite, which has been treated in step S103, is placed into 32g of heated and melted polylactic acid, and polylactic acid-coated biochar particles are obtained by capsule machine. S105. Place 8g of polylactic acid-coated biochar particles obtained in step S104 into 80g of sodium hydroxide solution with a concentration of 0.08mol / L and treat for 8min. Then filter, wash the filtered product with deionized water and then vacuum dry. S106. Mix 6g of polylactic acid-coated biochar particles treated in step S105 with 2.4g of magnesium phosphate cement with a particle size of 800 mesh, add 1.1g of carboxymethyl cellulose solution with a concentration of 1.5wt%, stir continuously for 2h, and then vacuum dry to obtain the core material. S107. Add 6g of the core material obtained in step S106 to 7.5g of sodium alginate aqueous solution with a concentration of 6wt% to obtain a suspension. Add the suspension dropwise to a mixed solution of 14g of calcium chloride, chitosan and acetic acid through a dropper. The concentrations of calcium chloride, chitosan and acetic acid are 3wt%, 22wt% and 3wt%, respectively. React for 40min, then filter. After vacuum drying, the filtered product is used to obtain smart microcapsules.

[0019] Example 2 A multidimensional heavy metal-oriented stabilized phosphogypsum roadbed material, comprising the following raw materials: 100g phosphogypsum, 20g slag powder, 120g aggregate, 3g smart microcapsules, 3g alkaline activator and 15g water; The preparation method of the above-mentioned intelligent microcapsules includes the following steps: S101. Disperse 10g of biochar with a particle size of 50 mesh into 400g of calcium nitrate solution with a concentration of 0.2wt% to obtain a mixed solution; S102. Add 400g of 0.1wt% ammonium hydrogen phosphate solution to the mixture obtained in step S101, add 28wt% ammonia water to adjust the pH to 10, heat to 50℃, react for 0.5h, then filter, wash the filtered product with deionized water until neutral, and calcine at 500℃ for 5h to obtain biochar loaded with hydroxyapatite. S103. The 10g of hydroxyapatite-loaded biochar obtained in step S102 is soaked in 150g of 0.1wt% mercaptoacetic acid solution for 1h, then filtered, and the filtered product is washed with deionized water and then vacuum dried. S104. 8g of biochar loaded with hydroxyapatite, which has been treated in step S103, is placed into 24g of heated and melted polylactic acid, and polylactic acid-coated biochar particles are obtained by capsule machine. S105. Place 8g of polylactic acid-coated biochar particles obtained in step S104 into 80g of 0.05mol / L sodium hydroxide solution and treat for 5min. Then filter, wash the filtered product with deionized water and then vacuum dry. S106. Mix 6g of polylactic acid-coated biochar particles treated in step S105 with 3g of magnesium phosphate cement with a particle size of 500 mesh, add 1.5g of carboxymethyl cellulose solution with a concentration of 1wt%, stir continuously for 1h, and then vacuum dry to obtain the core material. S107. Add 6g of the core material obtained in step S106 to 12g of sodium alginate aqueous solution with a concentration of 5wt% to obtain a suspension. Drop the suspension into a mixed solution of calcium chloride, chitosan and acetic acid with a concentration of 2wt%, 15wt% and 2wt% respectively. React for 30min, then filter. After vacuum drying, obtain the smart microcapsules.

[0020] Example 3 A multidimensional heavy metal-oriented stabilized phosphogypsum roadbed material, comprising the following raw materials: 120g phosphogypsum, 30g slag powder, 150g aggregate, 8g smart microcapsules, 5g alkaline activator and 20g water; The preparation method of the above-mentioned intelligent microcapsules includes the following steps: S101. Disperse 10g of biochar with a particle size of 150 mesh into 800g of calcium nitrate solution with a concentration of 0.5wt% to obtain a mixed solution; S102. Add 400g of 0.4wt% ammonium hydrogen phosphate solution to the mixture obtained in step S101, add ammonia water to adjust the pH to 11, heat to 80℃, react for 1h, then filter, wash the filtered product with deionized water until neutral, and calcine at 700℃ for 10h to obtain biochar loaded with hydroxyapatite. S103. The 10g of biochar loaded with hydroxyapatite obtained in step S102 is soaked in 150g of 1wt% mercaptoacetic acid solution for 2h, then filtered, and the filtered product is washed with deionized water and then vacuum dried. S104. 8g of biochar loaded with hydroxyapatite, which has been treated in step S103, is placed into 48g of heated and melted polylactic acid, and polylactic acid-coated biochar particles are obtained by capsule machine. S105. Place 10g of polylactic acid-coated biochar particles obtained in step S104 into 100g of 0.1mol / L sodium hydroxide solution and treat for 10min. Then filter, wash the filtered product with deionized water and then vacuum dry. S106. Mix 8g of polylactic acid-coated biochar particles treated in step S105 with 2.67g of magnesium phosphate cement with a particle size of 1000 mesh, add 0.89g of carboxymethyl cellulose solution with a concentration of 2wt%, stir continuously for 3h, and then vacuum dry to obtain the core material. S107. Add 8g of the core material obtained in step S106 to 8g of a 10wt% sodium alginate aqueous solution to obtain a suspension. Drop the suspension into a mixed solution of 16g ​​of calcium chloride, chitosan and acetic acid through a dropper. The concentrations of calcium chloride, chitosan and acetic acid are 5wt%, 25wt% and 4wt%, respectively. React for 50min, then filter. After vacuum drying, the filtered product is used to obtain smart microcapsules.

[0021] Example 4 A multidimensional heavy metal-oriented stabilized phosphogypsum roadbed material, comprising the following raw materials: 110g phosphogypsum, 25g slag powder, 140g aggregate, 6g smart microcapsules, 4g alkaline activator and 18g water; The preparation method of the above-mentioned intelligent microcapsules includes the following steps: S101. Disperse 10g of biochar with a particle size of 100 mesh into 800g of calcium nitrate solution with a concentration of 0.3wt% to obtain a mixed solution; S102. Add 600g of 0.2wt% ammonium hydrogen phosphate solution to the mixture obtained in step S101, add ammonia water to adjust the pH to 10, heat to 70℃, react for 0.8h, then filter, wash the filtered product with deionized water until neutral, and calcine at 650℃ for 9h to obtain biochar loaded with hydroxyapatite. S103. The 10g of hydroxyapatite-loaded biochar obtained in step S102 is soaked in 150g of 0.6wt% mercaptoacetic acid solution for 1.2h, then filtered, and the filtered product is washed with deionized water and then vacuum dried. S104. 8g of biochar loaded with hydroxyapatite, which has been treated in step S103, is placed into 40g of heated and melted polylactic acid, and polylactic acid-coated biochar particles are obtained by capsule machine. S105. Place 8g of polylactic acid-coated biochar particles obtained in step S104 into 80g of sodium hydroxide solution with a concentration of 0.09mol / L and treat for 8min. Then filter, wash the filtered product with deionized water and then vacuum dry. S106. Mix 6g of polylactic acid-coated biochar particles treated in step S105 with 3g of magnesium phosphate cement with a particle size of 800 mesh, add 1.5g of carboxymethyl cellulose solution with a concentration of 1wt%, stir continuously for 2h, and then vacuum dry to obtain the core material. S107. Add 6g of the core material obtained in step S106 to 6g of a 5wt% sodium alginate aqueous solution to obtain a suspension. Drop the suspension into a mixed solution of 10g of calcium chloride, chitosan and acetic acid through a dropper. The concentrations of calcium chloride, chitosan and acetic acid are 3wt%, 15wt% and 4wt%, respectively. React for 45min, then filter. After vacuum drying, the filtered product is used to obtain smart microcapsules.

[0022] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that step S106 was completely omitted. In step S107, polylactic acid-coated biochar particles and magnesium phosphate cement treated in step S105 were directly added to the sodium alginate solution. The total amount of polylactic acid-coated biochar particles and magnesium phosphate cement treated in step S105 was 6g, and the mass ratio between polylactic acid-coated biochar particles and magnesium phosphate cement treated in step S105 was 2.5:1. The amounts of other materials were the same as in Example 1.

[0023] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that steps S104-S106 were completely omitted. In step S107, biochar loaded with hydroxyapatite and magnesium phosphate cement that had been treated in step S103 were added. The total amount of polylactic acid-coated biochar particles and magnesium phosphate cement treated in step S103 was 6g, and the mass ratio between polylactic acid-coated biochar particles and magnesium phosphate cement treated in step S103 was 2.5:1. The amounts of other materials were the same as in Example 1.

[0024] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that steps S101-106 were completely omitted. First, hydroxyapatite, biochar treated with mercaptoacetic acid solution, and magnesium phosphate cement were mixed evenly. Then, the mixed powder was added to sodium alginate solution to obtain a suspension. Finally, the suspension was dropped into a mixed solution of calcium chloride, chitosan, and acetic acid. The total amount of hydroxyapatite, biochar treated with mercaptoacetic acid solution, and magnesium phosphate cement was 6g. The mass ratio between hydroxyapatite and biochar treated with mercaptoacetic acid solution and the mass of magnesium phosphate cement was 2.5:1, and the mass ratio between hydroxyapatite and biochar treated with mercaptoacetic acid solution was 1:9. The amounts of other materials were the same as in Example 1. The average particle size of hydroxyapatite was 200nm.

[0025] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that steps S101-106 were completely omitted. First, hydroxyapatite, biochar treated with mercaptoacetic acid solution, and magnesium phosphate cement were mixed evenly. Then, the mixed powder was added to sodium alginate solution to obtain a suspension. Finally, the suspension was dropped into a mixed solution of calcium chloride, chitosan, and acetic acid. The total amount of hydroxyapatite, biochar treated with mercaptoacetic acid solution, and magnesium phosphate cement was 6g. The mass ratio between hydroxyapatite and biochar treated with mercaptoacetic acid solution and the mass of magnesium phosphate cement was 2.5:1, and the mass ratio between hydroxyapatite and biochar treated with mercaptoacetic acid solution was 3:7. The amounts of other materials were the same as in Example 1. The average particle size of hydroxyapatite was 200nm.

[0026] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that steps S101-106 were completely omitted. First, hydroxyapatite, biochar treated with mercaptoacetic acid solution, and magnesium phosphate cement were mixed evenly. Then, the mixed powder was added to sodium alginate solution to obtain a suspension. Finally, the suspension was dropped into a mixed solution of calcium chloride, chitosan, and acetic acid. The total amount of hydroxyapatite, biochar treated with mercaptoacetic acid solution, and magnesium phosphate cement was 6g. The mass ratio between hydroxyapatite and biochar treated with mercaptoacetic acid solution and the mass of magnesium phosphate cement was 2.5:1, and the mass ratio between hydroxyapatite and biochar treated with mercaptoacetic acid solution was 1:1. The amounts of other materials were the same as in Example 1. The average particle size of hydroxyapatite was 200nm.

[0027] Examples 1-4 and Comparative Examples 1-5 comprise a total of 9 sets of materials. These 9 sets of materials were prepared into gypsum roadbed materials. The preparation method includes the following steps: S1. Add phosphogypsum, slag powder, aggregate and smart microcapsules to water, stir and mix evenly to obtain a mixture; S2. Add an alkaline activator to the mixture obtained in step S1, and continue stirring to mix evenly to obtain a slurry; S3. Add the slurry obtained in step S2 into the mold, cure and demold to obtain phosphogypsum roadbed material.

[0028] Heavy metal leaching tests were conducted on the phosphogypsum roadbed materials prepared in Examples 1-4 and Comparative Examples 1-5. The test methods were carried out according to HJ-T299-2007 Solid Waste Leaching Toxicity Leaching Method. The test results are shown in Table 1 below: Table 1: Heavy metal leaching experiments of phosphogypsum roadbed materials prepared in Examples 1-4 and Comparative Examples 1-5

[0029] As can be seen from the data in Table 1 above, the phosphogypsum roadbed material prepared in Example 1 has a significantly lower leaching amount of heavy metals compared to the phosphogypsum roadbed materials prepared in Comparative Examples 1-5. Among them, Comparative Example 1 lacks the process of combining polylactic acid-coated biochar particles and magnesium phosphate cement, resulting in a decrease in the heavy metal fixation effect. Comparative Example 2 lacks the polylactic acid coating of biochar particles loaded with hydroxyapatite, weakening the slow-release effect and further reducing the heavy metal fixation capacity. Comparative Examples 3-5 simply mix and coat biochar, hydroxyapatite, and magnesium phosphate cement, which have the ability to fix heavy metals, resulting in a material with a lack of layering in heavy metal fixation, a worse slow-release effect, and a poorer overall heavy metal fixation effect.

[0030] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A multidimensional heavy metal-oriented stabilized phosphogypsum roadbed material, characterized in that, Raw materials comprising the following components by weight: 100-120 parts phosphogypsum, 20-30 parts slag powder, 120-150 parts aggregate, 3-8 parts intelligent microcapsules, 3-5 parts alkaline activator, and 15-20 parts water; The preparation method of the intelligent microcapsule includes the following steps: S101. Disperse biochar in calcium nitrate solution to obtain a mixture; S102. Add ammonium hydrogen phosphate solution dropwise to the mixture obtained in step S101, adjust the pH to 9-11 by adding ammonia water dropwise, heat to 50-80℃, react for 0.5-1h, then filter, wash the filtered product with deionized water until neutral, and calcine at 500-700℃ for 5-10h to obtain biochar loaded with hydroxyapatite. S103. The biochar loaded with hydroxyapatite obtained in step S102 is soaked in mercaptoacetic acid solution for 1-2 hours, then filtered, and the filtered product is washed with deionized water and then vacuum dried. S104. The biochar loaded with hydroxyapatite, which has been treated in step S103, is placed into heated and melted polylactic acid, and polylactic acid-coated biochar particles are obtained by using a capsule machine. S105. The polylactic acid-coated biochar particles obtained in step S104 are placed in a 0.05-0.1 mol / L sodium hydroxide solution for 5-10 min, then filtered, and the filtered product is washed with deionized water and then vacuum dried. S106. The polylactic acid-coated biochar particles treated in step S105 are mixed with magnesium phosphate cement, and carboxymethyl cellulose solution is added. The mixture is stirred continuously for 1-3 hours, and then vacuum dried to obtain the core material. S107. The core material obtained in step S106 is added to an aqueous solution of sodium alginate to obtain a suspension. The suspension is then added dropwise to a mixed solution of calcium chloride, chitosan and acetic acid through a dropper. The mixture is reacted for 30-50 minutes, then filtered. The filtered product is then vacuum dried to obtain smart microcapsules.

2. The multidimensional heavy metal-oriented stabilized phosphogypsum roadbed material according to claim 1, characterized in that, In step S101, the concentration of calcium nitrate in the calcium nitrate solution is 0.2-0.5 wt%, the mass ratio of biochar to calcium nitrate solution is 1:(40-80), and the particle size of biochar is 50-150 mesh.

3. The multidimensional heavy metal-oriented stabilized phosphogypsum roadbed material according to claim 1, characterized in that, The concentration of ammonium hydrogen phosphate in the ammonium hydrogen phosphate solution in step S102 is 0.1-0.4 wt%, and the mass ratio between the ammonium hydrogen phosphate solution in step S102 and the calcium nitrate solution in step S101 is 1:(1-2).

4. The multidimensional heavy metal-oriented stabilized phosphogypsum roadbed material according to claim 1, characterized in that, In step S103, the concentration of mercaptoacetic acid in the mercaptoacetic acid solution is 0.1-1 wt%, and the mass ratio between the biochar loaded with hydroxyapatite and the mercaptoacetic acid solution is 1:

15.

5. The multidimensional heavy metal-oriented stabilized phosphogypsum roadbed material according to claim 1, characterized in that, In step S104, the mass ratio of the hydroxyapatite-loaded biochar to polylactic acid processed in step S103 is 1:(3-6).

6. The multidimensional heavy metal-oriented stabilized phosphogypsum roadbed material according to claim 1, characterized in that, In step S105, the mass ratio of polylactic acid-coated biochar to sodium hydroxide solution is 1:

10.

7. The multidimensional heavy metal-oriented stabilized phosphogypsum roadbed material according to claim 1, characterized in that, In step S106, the mass ratio between the polylactic acid-coated biochar treated in step S105 and the magnesium phosphate cement is (2-3):1, the particle size of the magnesium phosphate cement is 500-1000 mesh, the concentration of the carboxymethyl cellulose solution is 1-2 wt%, and the mass ratio between the carboxymethyl cellulose solution and the magnesium phosphate cement is 1:(2-3).

8. The multidimensional heavy metal-oriented stabilized phosphogypsum roadbed material according to claim 1, characterized in that, In step S107, the concentration of sodium alginate solution is 5-10 wt%, the mass ratio between core material and sodium alginate solution is (0.5-1):1, the concentrations of calcium chloride, chitosan and acetic acid in the mixed solution are 2-5 wt%, 15-25 wt% and 2-4 wt% respectively, and the mass ratio between the mixed solution of calcium chloride, chitosan and acetic acid and sodium alginate solution is (1.5-2):

1.

9. The method for preparing multidimensional heavy metal-oriented stabilized phosphogypsum roadbed material according to any one of claims 1-8, characterized in that, The preparation method includes the following steps: S1. Add phosphogypsum, slag powder, aggregate and smart microcapsules to water according to the mass ratio, and stir to mix evenly to obtain a mixture; S2. Add alkaline activator to the mixture obtained in step S1 according to the mass fraction, and continue to stir and mix evenly to obtain a slurry; S3. Add the slurry obtained in step S2 into the mold, cure and demold to obtain gypsum roadbed material.

Images