Lime composite reagent for phosphogypsum innocent treatment based on inorganic formula, preparation method and application

Abstract

The invention discloses a lime composite agent for phosphogypsum innocent treatment based on an inorganic formula, a preparation method and application, and belongs to the technical field of resource utilization, the developed'alkali neutralization-photosensitive catalysis-excitation emulsion 'composite agent breaks through the technical defects of a traditional lime agent, lime powder and multiple components are compounded, and the comprehensive utilization rate of the lime powder is improved. The calcium-based composite alkali material with high alkalinity is prepared, the emulsification degree of lime powder is improved, and the activity degree of lime milk is enhanced. Compared with a traditional ardealite neutralization treatment process, the method has the advantages that the ultraviolet illumination step is added, soluble fluorine and phosphorus ions can be physically adsorbed, photo-generated holes can be physically adsorbed, generated superoxide free radicals can destroy molecular structures of organic matters in ardealite, decomposition of the organic matters is promoted, meanwhile, the component A of the exciting agent is optimized, and the utilization rate of the exciting agent is increased. And the modified polyacrylamide microspheres are added as a complexing agent, so that the modified polyacrylamide microspheres are promoted to be complexed with the carrier adsorbent under ultraviolet radiation, and the curing effect is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental protection and resource utilization, and in particular to a lime composite agent for harmless treatment of phosphogypsum based on an inorganic formula, a preparation method and an application thereof. Background Art

[0002] Phosphogypsum is a byproduct of phosphoric acid production, typically generating 4.5-5.5 tons of phosphogypsum for every ton of phosphoric acid produced. Phosphogypsum is a solid waste, appearing as a fine, yellowish-white, off-white, or dark-gray powder. The Florida Phosphate Institute reported that global phosphogypsum emissions reached 5.6 billion tons in 2010, with an annual increase of 110 to 150 million tons. China, a major producer of phosphate fertilizers, currently has over 800 million tons of phosphogypsum stockpiles, with approximately 50 million tons added annually. However, most phosphogypsum is disposed of in stockpiles, which not only consumes land resources but also poses a significant threat to the environment.

[0003] Currently, there are two main approaches to treating phosphogypsum in engineering: one is to discharge and discard it, or to stockpile it; the other is to render it harmless and then recycle it. Leachate obtained from leaching tests according to the "Toxicity Extraction Method for Solid Waste" (GB5086-1997) contains one or more pollutants exceeding the maximum allowable discharge concentration in the "Comprehensive Wastewater Discharge Standard" (GB8978-1996), or has a pH value between 6 and 9, which is not considered general industrial solid waste. Due to its soluble phosphorus and soluble fluorine content and its pH between 2 and 4, phosphogypsum should also be classified as a Class II solid waste and should be disposed of in accordance with the Pollution Control Standard for Storage and Disposal Sites of General Industrial Solid Wastes (GB18599-2001). The state encourages enterprises to prioritize ecological restoration and other methods to utilize phosphogypsum. For unusable materials, enterprises are allowed to classify and store or dispose of them in accordance with national environmental protection standards.

[0004] Soluble phosphorus significantly impacts phosphogypsum. Lime neutralization involves adding quicklime to phosphogypsum, which reacts with impurities such as soluble phosphorus, fluorine, and residual acid to form insoluble phosphates and fluorides, thereby removing impurities. Lime neutralization and curing is the preferred process for non-water-washing pretreatment of phosphogypsum. Lime neutralization offers significant results, a simple process, and minimal investment, making it a practical and effective pretreatment method. It is particularly well-suited for phosphogypsum with low organic matter content and stable quality. For large-scale phosphogypsum treatment, it is a very simple, efficient, and low-investment, harmless treatment process.

[0005] In traditional lime reagents, the main component of quicklime is CaO, which is generally in block form. Pure lime is white, and light gray or light yellow when it contains impurities. The optimal condition for quicklime to neutralize modified phosphogypsum is weak acidity. Hydrated lime is a white powdery solid. When added to water, it forms two layers, the upper aqueous solution is called clear lime water, and the lower suspension is called compound alkali or lime slurry. The use of slaked lime can effectively neutralize H in phosphogypsum. + , and then chemically solidify the water-soluble phosphorus and free fluorine in the phosphogypsum. Commonly used traditional lime reagents, quicklime, slaked lime, and composite alkali, all have problems such as low effective calcium content and weak alkalinity. During the harmless treatment of phosphogypsum, this results in poor solidification of the harmful components in the phosphogypsum, making it difficult to convert it from a Class II solid waste to a Class I solid waste. Therefore, there is an urgent need to develop new functional lime reagents to resolve the above technical bottlenecks.

[0006] Therefore, developing an environmentally friendly, safe and efficient post-treatment method for phosphogypsum that reduces heavy metal residues, has short steps, is simple and efficient is a problem currently faced in the fields of environmental protection and resource utilization. It is a very meaningful research in terms of ecological environment protection and resource recycling. Summary of the Invention

[0007] To this end, the present invention provides a lime composite agent for harmless treatment of phosphogypsum based on an inorganic formula, a preparation method and an application. The method prepares a calcium-based composite alkali material with high alkalinity and applies it to the harmless disposal of phosphogypsum. It further optimizes and upgrades the post-treatment process of phosphogypsum by ultraviolet light catalytic adsorption and removal of organic matter produced in the phosphogypsum.

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] According to a first aspect of the present invention, a lime composite agent for harmless treatment of phosphogypsum based on an inorganic formula is provided, comprising the following components:

[0010] Activator A, buffer B and lime, wherein the mass ratio of activator A, buffer B and lime is (1-10): (0.5-5): (5-25); wherein the ratio of activator A, buffer B and lime can be adjusted according to the pH value and soluble phosphorus and fluorine concentration of the treated phosphogypsum;

[0011] After being dissolved in an appropriate amount of water, the solid content of the stimulator A in the composite medicine is (0.3-3)%.

[0012] Furthermore, the activator A includes a carrier stabilizer, a carrier adsorbent, a photosensitive catalyst and a complexing agent, and the mass ratio of the carrier stabilizer, the carrier adsorbent, the photosensitive catalyst and the complexing agent is (10-20): (1-5): (0.5-2): (1-3).

[0013] Furthermore, the mass ratio of the carrier stabilizer, the carrier adsorbent, the photosensitive catalyst and the complexing agent is 15:3:1:2.

[0014] Furthermore, the carrier stabilizer is bentonite or clay, the carrier adsorbent is biochar, activated carbon or modified activated carbon, the photosensitive catalyst is titanium dioxide or zinc oxide, and the complexing agent is modified polyacrylamide microspheres.

[0015] Among them, bentonite has good adhesion and expansion properties. After mixing with phosphogypsum, it can form a bonding network between the particles, enhance the structural strength of the phosphogypsum system, make the solidified body denser, reduce the risk of structural damage caused by the presence of impurities such as fluorine and phosphorus or the influence of external factors, and help maintain the stability of the solidified body.

[0016] Among them, the multi-level pore structure of activated carbon (micropore <2nm, mesopore 2-50nm, macropore >50nm) adsorbs soluble phosphorus and fluorine through van der Waals force and capillary action. Its specific surface area (500-1500m 2 / g) and surface chemical properties determine the selective adsorption capacity.

[0017] Under light, electrons in the valence band of titanium dioxide are excited to the conduction band, forming photogenerated electron-hole pairs. Holes have strong oxidizing properties, oxidizing water adsorbed on the titanium dioxide surface to form hydroxyl radicals, while electrons react with oxygen in the air to form superoxide anions. Hydroxyl radicals and superoxide anions have strong oxidizing properties, capable of oxidizing and decomposing organic pollutants in phosphogypsum into harmless substances such as carbon dioxide and water. They can also oxidize some heavy metal ions into more insoluble and stable high-valence states.

[0018] Furthermore, wherein, wherein, buffer B is a trivalent aluminum source compound, and the compound is preferably selected from inorganic aluminum salts, coordinated aluminum complexes or dissociable trivalent aluminum complex salts with sustained release and pH stability, preferably aluminum hydroxide, γ-alumina, sodium metaaluminate and its derivatives. Alumina, aluminum hydroxide, aluminates, etc., under alkaline conditions, will undergo complex chemical reactions with calcium ions and other components in phosphogypsum to generate hydrated calcium aluminate and other gelling substances. These gelling substances are dispersed on the surface of phosphogypsum particles to form a tight structure, improve the strength and stability of the phosphogypsum solidified body, and at the same time, due to the amphoteric nature of aluminum itself, play a buffering role and maintain the stability of the pH value, thereby achieving the harmlessness of phosphogypsum. Pre-treating phosphogypsum provides a guarantee for subsequent resource utilization (such as preparing high-purity gypsum building materials).

[0019] The curing agent (calcium salt) chemically reacts with harmful substances in phosphogypsum (such as phosphorus and fluorine) to form insoluble compounds, thereby solidifying and stabilizing the harmful substances. For example, calcium oxide reacts with phosphoric acid in phosphogypsum to form calcium phosphate precipitate, and calcium chloride reacts with fluoride ions in phosphogypsum to form calcium fluoride precipitate. These insoluble compounds form a stable lattice structure in the cured product, effectively reducing the risk of harmful substances dissolving out.

[0020] According to a second aspect of the present invention, there is provided a method for preparing a lime composite agent for harmless treatment of phosphogypsum based on an inorganic formula, comprising the following steps:

[0021] 1) Add the carrier stabilizer, carrier adsorbent, photosensitive catalyst and complexing agent to a mixing container in proportion, add an appropriate amount of water to dissolve, stir at room temperature at a stirring speed of 150-260 rpm, and stir for 1-2 hours until the mixture is uniform to obtain a mixed solution A;

[0022] 2) adding buffer B to the mixed solution A in 1) according to the proportion, stirring at room temperature at a speed of 200-300 rpm for 0.5-1 h until the mixture is uniformly mixed to obtain a mixed solution B;

[0023] 3) Add lime to the mixed solution in 2) according to the proportion, stir at room temperature, at a stirring speed of 150-200 rpm, for 0.5-1 hour until the mixture is uniform, and let it stand for 6-24 hours to obtain the composite agent.

[0024] According to a third aspect of the present invention, there is provided an application of a lime composite agent for harmless treatment of phosphogypsum based on an inorganic formula in the harmless disposal of phosphogypsum.

[0025] Further, a composite agent is added to the new material phosphogypsum, and the mass ratio of phosphogypsum to the composite agent is 100:(1-15), stirred at room temperature for 2-3 hours, and a stirring speed of 250-450 rpm. During the stirring process, ultraviolet irradiation is performed with an irradiation intensity of 5-10 mW / cm 2 , then let it stand for 3-6 hours;

[0026] Start stirring again, stir at room temperature for 2-3 hours, and irradiate with UV light during stirring at an intensity of 10-100 mW / cm 2 , then let it sit until the process is complete.

[0027] Furthermore, the moisture content of the phosphogypsum is 12-25%.

[0028] Furthermore, the mass ratio of the phosphogypsum to the composite agent is 100:13.

[0029] The present invention has the following advantages:

[0030] The present invention independently develops a new type of lime composite agent material, which breaks through the technical defects of traditional lime agents. It compounds lime powder with active components, dispersants, etc., improves the emulsification degree of lime powder and thus enhances the "activity" of lime milk, and prepares a calcium-based composite alkali material with high alkalinity. On this basis, it is applied to the harmless disposal of phosphogypsum, and its effectiveness, economy and stability are further evaluated, providing a new technical solution for the harmless disposal of phosphogypsum. In addition, compared with the traditional neutralization treatment of phosphogypsum process, the addition of ultraviolet light irradiation step, this process flow can not only physically adsorb soluble fluorine and phosphorus ions, but also photogenerated holes and the generated superoxide radicals can destroy the molecular structure of organic matter in phosphogypsum, promote the decomposition of organic matter, and decompose it into harmless CO2, H2O, etc., which is beneficial to inhibit sulfate-reducing bacteria in an anaerobic environment in the later stage and reduce the generation of hydrogen sulfide. The present invention can effectively improve the defects of poor curing effect in traditional processes, and can effectively adsorb heavy metal ions in phosphogypsum, photocatalytically decompose organic matter present in phosphogypsum, etc. At the same time, on this basis, the component of activator A was optimized, and modified polyacrylamide microspheres were added as complexing agents to promote the complexation of modified polyacrylamide microspheres with the carrier adsorbent under ultraviolet irradiation, thereby improving the curing effect. DETAILED DESCRIPTION

[0031] The following describes the implementation of the present invention using specific embodiments. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. Obviously, the embodiments described are only a portion of the present invention, not all of it. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0032] According to a first aspect of the present invention, a lime composite agent for harmless treatment of phosphogypsum based on an inorganic formula is provided, comprising the following components:

[0033] The mass ratio of stimulator A, buffer B and lime is (1-10): (0.5-5): (5-25);

[0034] After being dissolved in an appropriate amount of water, the solid content of the stimulator A in the composite drug is (0.3-3)%.

[0035] Furthermore, the activator A includes a carrier stabilizer, a carrier adsorbent, a photosensitive catalyst and a complexing agent, and the mass ratio of the carrier stabilizer, the carrier adsorbent, the photosensitive catalyst and the complexing agent is (10-20): (1-5): (0.5-2): (1-3).

[0036] Furthermore, the carrier stabilizer is bentonite or clay, the carrier adsorbent is biochar, activated carbon or modified activated carbon, the photosensitive catalyst is titanium dioxide or zinc oxide, and the complexing agent is modified polyacrylamide microspheres.

[0037] The preparation method of modified polyacrylamide microspheres in this application is as follows:

[0038] Polyacrylamide microspheres and zinc oxide are added to a reaction vessel in a mass ratio of 15:2. An appropriate amount of water is added and the pH value is adjusted to 9-10 using sodium hydroxide solution. The reaction is carried out at room temperature with continuous stirring during the reaction. Zinc oxide and polyacrylamide undergo a coordination reaction. After reacting for 3-4 hours, the reaction is allowed to stand at room temperature. The modified polyacrylamide microspheres are then filtered and washed with ethanol to obtain the modified polyacrylamide microspheres. The modified polyacrylamide microspheres added in this application can promote complexation with activated carbon when exposed to ultraviolet light, thereby improving the curing effect.

[0039] Furthermore, the buffer B is a trivalent aluminum source compound, which is preferably selected from inorganic aluminum salts, coordinated aluminum complexes or dissociable trivalent aluminum complex salts with sustained release and pH stability, preferably aluminum hydroxide, γ-alumina, sodium aluminate and its derivatives.

[0040] According to a second aspect of the present invention, there is provided a method for preparing a lime composite agent for harmless treatment of phosphogypsum based on an inorganic formula, comprising the following steps:

[0041] 1) Add the carrier stabilizer, carrier adsorbent, photosensitive catalyst and complexing agent to a mixing container in proportion, add an appropriate amount of water to dissolve, stir at room temperature at a stirring speed of 150-260 rpm, and stir for 1-2 hours until the mixture is uniform to obtain a mixed solution A;

[0042] 2) adding buffer B to the mixed solution A in 1) according to the proportion, stirring at room temperature at a speed of 200-300 rpm for 0.5-1 h until the mixture is uniformly mixed to obtain a mixed solution B;

[0043] 3) Add lime to the mixed solution in 2) according to the proportion, stir at room temperature, at a stirring speed of 150-200 rpm, for 0.5-1 hour until the mixture is uniform, and let it stand for 6-24 hours to obtain the composite agent.

[0044] According to a third aspect of the present invention, there is provided an application of a lime composite agent for harmless treatment of phosphogypsum based on an inorganic formula in the harmless disposal of phosphogypsum.

[0045] Further, a composite agent is added to the new material phosphogypsum, and the mass ratio of phosphogypsum to the composite agent is 100:(1-15), stirred at room temperature for 2-3 hours, and a stirring speed of 250-450 rpm. During the stirring process, ultraviolet irradiation is performed with an irradiation intensity of 5-10 mW / cm 2 , then let it stand for 3-6 hours;

[0046] Start stirring again, stir at room temperature for 2-3 hours, and irradiate with UV light during stirring at an intensity of 10-100 mW / cm 2 , then let it sit until the process is complete.

[0047] Furthermore, the moisture content of the phosphogypsum is 12-25%.

[0048] The technical effects of this application are described below with reference to embodiments.

[0049] Example 1

[0050] This embodiment provides a lime composite agent for harmless treatment of phosphogypsum based on an inorganic formula, which is prepared as follows:

[0051] 1) Weigh 2.5 kg of bentonite, 0.8 kg of activated carbon, 0.2 kg of titanium dioxide, and 0.5 kg of modified polyacrylamide microspheres into a mixing container, add an appropriate amount of water to dissolve, and stir at room temperature at a stirring speed of 180 rpm for 2 h until the mixture is uniformly mixed to obtain a mixed solution A;

[0052] 2) Weighing 0.1.1 kg of aluminum hydroxide was added to the mixed solution A prepared in 1), and stirred at room temperature at a speed of 200 rpm for 0.5 h until uniformly mixed to obtain a mixed solution B;

[0053] 3) Weigh 20 kg of lime and add it to the mixed solution in 2), stir at room temperature at a stirring speed of 150 rpm for 0.5 h until the mixture is uniformly mixed, and let it stand for 24 h to obtain a composite agent. After the above processing steps, the solid content of activator A in the composite agent is 2%.

[0054] The lime composite agent prepared above is further applied to the harmless treatment of phosphogypsum, and the specific treatment steps are as follows:

[0055] The composite agent was added to the new material phosphogypsum (total phosphorus in the leachate was 137.35 mg / L, fluoride content was 320.17 mg / L, pH was 3.0, and water content was 12%), and the mass ratio of phosphogypsum to the composite agent was 100:3. The stirring time was 2 h, the stirring speed was 300 rpm, and ultraviolet irradiation was performed during the stirring process at room temperature with an irradiation intensity of 10 mW / cm 2Then let it stand for 3 hours; start stirring again, stirring time is 2 hours, and perform ultraviolet irradiation during stirring at room temperature, with an irradiation intensity of 50mW / cm 2 , then let it sit until the process is complete.

[0056] Example 2

[0057] This embodiment provides a lime composite agent for harmless treatment of phosphogypsum based on an inorganic formula, which is prepared as follows:

[0058] 1) Weigh 2.2 kg of bentonite, 0.6 kg of activated carbon, 0.1 kg of titanium dioxide, and 0.6 kg of modified polyacrylamide microspheres into a mixing container, add an appropriate amount of water to dissolve, and stir at room temperature at a stirring speed of 200 rpm for 2 h until uniformly mixed to obtain a mixed solution A;

[0059] 2) Weigh 1.6 kg of aluminum hydroxide and add it to the mixed solution A prepared in 1), stirring at room temperature at a speed of 300 rpm for 0.5 h until the mixture is uniformly mixed to obtain a mixed solution B;

[0060] 3) Weigh 27 kg of lime and add it to the mixed solution in 2), stir at room temperature at 150 rpm for 1 hour until the mixture is uniformly mixed, and let it stand for 12 hours to obtain a composite agent. After the above processing steps, the solid content of activator A in the composite agent is 1%.

[0061] The lime composite agent prepared above is further applied to the harmless treatment of phosphogypsum, and the specific treatment steps are as follows:

[0062] The composite agent was added to the new material phosphogypsum (total phosphorus in the leachate was 137.35 mg / L, fluoride content was 320.17 mg / L, pH was 3.0, and water content was 12%), and the mass ratio of phosphogypsum to the composite agent was 100:8. The stirring time was 2.5 h, the stirring speed was 450 rpm, and ultraviolet irradiation was performed during the stirring process at room temperature with an irradiation intensity of 8 mW / cm 2 , then let it stand for 6 hours; start stirring again, stirring time is 2 hours, and ultraviolet irradiation is carried out during stirring at room temperature, with an irradiation intensity of 70mW / cm 2 , then let it sit until the process is complete.

[0063] Example 3

[0064] This embodiment provides a lime composite agent for harmless treatment of phosphogypsum based on an inorganic formula, which is prepared as follows:

[0065] 1) 3 kg of bentonite, 0.6 kg of activated carbon, 0.2 kg of titanium dioxide, and 0.4 kg of modified polyacrylamide microspheres were added to a mixing container, and an appropriate amount of water was added to dissolve them. The mixture was stirred at room temperature at a stirring speed of 260 rpm for 1 hour until the mixture was uniformly mixed to obtain a mixed solution A;

[0066] 2) Weigh 1.7 kg of aluminum hydroxide and add it to the mixed solution A prepared in 1), stirring at room temperature at 250 rpm for 1 hour until the mixture is uniformly mixed to obtain a mixed solution B;

[0067] 3) Weigh 22 kg of lime and add it to the mixed solution in 2), stir at room temperature at 180 rpm for 0.5 h until uniformly mixed, and let it stand for 20 h to obtain a composite agent. After the above processing steps, the solid content of activator A in the composite agent is 2%.

[0068] The lime composite agent prepared above is further applied to the harmless treatment of phosphogypsum, and the specific treatment steps are as follows:

[0069] The composite agent was added to the new material phosphogypsum (total phosphorus in the leachate was 137.35 mg / L, fluoride content was 320.17 mg / L, pH was 3.0, and water content was 12%), and the mass ratio of phosphogypsum to the composite agent was 100:13. The stirring time was 3 h, the stirring speed was 350 rpm, and ultraviolet irradiation was performed during the stirring process at room temperature with an irradiation intensity of 10 mW / cm 2 , then let it stand for 4 hours; start stirring again, stirring time is 3 hours, and ultraviolet irradiation is carried out during stirring at room temperature, with an irradiation intensity of 90mW / cm 2 , then let it sit until the process is complete.

[0070] Example 4

[0071] This embodiment provides a lime composite agent for harmless treatment of phosphogypsum based on an inorganic formula, which is prepared as follows:

[0072] 1) Weigh 3.5 kg of bentonite, 0.8 kg of activated carbon, 0.4 kg of titanium dioxide, and 0.3 kg of modified polyacrylamide microspheres into a mixing container, add an appropriate amount of water to dissolve, and stir at room temperature at a stirring speed of 260 rpm for 2 h until the mixture is uniformly mixed to obtain a mixed solution A;

[0073] 2) Weigh 1 kg of aluminum hydroxide and add it to the mixed solution A prepared in 1), stirring at room temperature at 200 rpm for 1 hour until the mixture is uniformly mixed to obtain a mixed solution B;

[0074] 3) Weigh 21 kg of lime and add it to the mixed solution in 2), stir at room temperature at 200 rpm for 0.5 h until uniformly mixed, and let it stand for 18 h to obtain a composite agent. After the above processing steps, the solid content of activator A in the composite agent is 3%.

[0075] The lime composite agent prepared above is further applied to the harmless treatment of phosphogypsum, and the specific treatment steps are as follows:

[0076] The composite agent was added to the new material phosphogypsum (total phosphorus in the leachate was 137.35 mg / L, fluoride content was 320.17 mg / L, pH was 3.0, and water content was 12%), and the mass ratio of phosphogypsum to the composite agent was 100:10. The stirring time was 2 h, the stirring speed was 300 rpm, and ultraviolet irradiation was performed during the stirring process at room temperature with an irradiation intensity of 10 mW / cm 2 , then let it stand for 6 hours; start stirring again, stirring time is 3 hours, and ultraviolet irradiation is carried out during stirring at room temperature, with an irradiation intensity of 50mW / cm 2 , then let it sit until the process is complete.

[0077] Example 5

[0078] This embodiment provides a lime composite agent for harmless treatment of phosphogypsum based on an inorganic formula, which is prepared as follows:

[0079] 1) Weigh 3.8 kg of bentonite, 0.4 kg of activated carbon, 0.4 kg of titanium dioxide, and 0.6 kg of modified polyacrylamide microspheres into a mixing container, add an appropriate amount of water to dissolve, and stir at room temperature at a stirring speed of 200 rpm for 1 hour until the mixture is uniformly mixed to obtain a mixed solution A;

[0080] 2) Weigh 1.2 kg of aluminum hydroxide and add it to the mixed solution A in 1), stirring at room temperature at a speed of 200 rpm for 1 hour until the mixture is uniform to obtain a mixed solution B;

[0081] 3) Weigh 25 kg of lime and add it to the mixed solution in 2), stir at room temperature at a stirring speed of 160 rpm for 0.5 h until the mixture is uniformly mixed, and let it stand for 12 h to obtain a composite agent. After the above processing steps, the solid content of activator A in the composite agent is 1%.

[0082] The lime composite agent prepared above is further applied to the harmless treatment of phosphogypsum, and the specific treatment steps are as follows:

[0083] The composite agent was added to the new material phosphogypsum (total phosphorus in the leachate was 137.35 mg / L, fluoride content was 320.17 mg / L, pH was 3.0, and water content was 12%), and the mass ratio of phosphogypsum to the composite agent was 100:8. The stirring time was 2 h, the stirring speed was 350 rpm, and ultraviolet irradiation was performed during the stirring process at room temperature with an irradiation intensity of 10 mW / cm 2 , then let it stand for 5h; start stirring again, stirring time is 2h, and ultraviolet irradiation is carried out during stirring at room temperature, with an irradiation intensity of 30mW / cm 2 , then let it sit until the process is complete.

[0084] Example 6

[0085] This embodiment provides a lime composite agent for harmless treatment of phosphogypsum based on an inorganic formula, which is prepared as follows:

[0086] 1) Weigh 2.1 kg of bentonite, 0.6 kg of activated carbon, 0.3 kg of titanium dioxide, and 0.2 kg of modified polyacrylamide microspheres into a mixing container, add an appropriate amount of water to dissolve, and stir at room temperature at a stirring speed of 210 rpm for 2 h until uniformly mixed to obtain a mixed solution A;

[0087] 2) Weighing 1.5 kg of aluminum hydroxide was added to the mixed solution A prepared in 1), and stirred at room temperature at a speed of 300 rpm for 1 h until uniformly mixed to obtain a mixed solution B;

[0088] 3) Weigh 26 kg of lime and add it to the mixed solution in 2), stir at room temperature at 200 rpm for 0.5 h until uniformly mixed, and let it stand for 10 h to obtain a composite agent. After the above processing steps, the solid content of activator A in the composite agent is 2%.

[0089] The lime composite agent prepared above is further applied to the harmless treatment of phosphogypsum, and the specific treatment steps are as follows:

[0090] The composite agent was added to the new material phosphogypsum (total phosphorus in the leachate was 137.35 mg / L, fluoride content was 320.17 mg / L, pH was 3.0, and water content was 12%), and the mass ratio of phosphogypsum to the composite agent was 100:5. The stirring time was 3 h, the stirring speed was 300 rpm, and ultraviolet irradiation was performed during the stirring process at room temperature with an irradiation intensity of 10 mW / cm 2 Then let it stand for 5 hours; start stirring again, stirring time is 2 hours, and perform ultraviolet irradiation during stirring at room temperature, with an irradiation intensity of 60mW / cm 2 , then let it sit until the process is complete.

[0091] Comparative Example 1

[0092] This comparative example is based on Example 3, except that activator A is not added and other conditions remain unchanged.

[0093] Comparative Example 2

[0094] This comparative example is based on Example 3, except that activator A and lime are not added, and other conditions remain unchanged.

[0095] Comparative Example 3

[0096] This comparative example is based on Example 3, except that stimulator A and buffer B are not added, and other conditions remain unchanged.

[0097] Comparative Example 4

[0098] This comparative example is based on Example 3, except that the complexing agent in activator A is not added, and other conditions remain unchanged.

[0099] Comparative Example 5

[0100] This comparative example is based on Example 3, but the following steps are omitted: stirring is restarted for 3 h, and ultraviolet irradiation is performed during stirring at room temperature with an irradiation intensity of 90 mW / cm 2 . Other conditions remain unchanged.

[0101] The lime composite agent prepared according to the preparation method of the above Examples 1-6 and Comparative Examples 1-5 was used to render phosphogypsum harmless. After standing for 2-3 days, the pH value, soluble phosphorus and soluble fluorine after treatment were respectively tested. The specific values ​​are shown in Table 1:

[0102]

[0103]

[0104] The above examples and comparative examples demonstrate that the ratio of activator A, buffer B, and lime in Example 3 achieves a relatively good combination effect, indicating that the activity of lime milk is primarily determined by the dispersion stability, dissolution rate, and particle size distribution of the calcium hydroxide particles in the lime milk, as well as the reactivity of the lime milk. The smaller the particle size, the narrower the particle size distribution, the more uniform the dispersion, and the higher the stability of the calcium hydroxide particles in the lime milk, the better the activity. Example 3 enhances the activity of lime, achieving the optimal technical effect. Furthermore, the other examples significantly outperformed the other comparative examples in reducing soluble phosphorus and soluble fluoride, demonstrating that the adopted combination is relatively reasonable. In Comparative Example 2, when no lime is added, lime is still the primary contributor to the curing effect. Furthermore, in Comparative Example 3, where no buffer B is added, the pH regulation effect on the reaction system is reduced. In Comparative Examples 1 and 3, where no activator A is added, the removal efficiency of soluble phosphorus and soluble fluoride is significantly lower than that of Examples 1-6. In Comparative Example 4, the step of adding a complexing agent is omitted. Although the removal effect of soluble phosphorus and soluble fluorine is better than that of Comparative Examples 1 and 3 (both without adding activator A), it is worse than the effect of Examples 1-6, especially worse than that of Example 3 (optimal ratio). This shows that the addition of a complexing agent can improve the curing effect under ultraviolet conditions. The main reason is that the modified polyacrylamide has a photoinitiator group, which can be cross-linked with components such as biochar under ultraviolet conditions to form a complex network, thereby improving the encapsulation of soluble phosphorus and soluble fluorine and reducing release. At the same time, in the present application, a secondary ultraviolet light is added to the reprocessing step. The main purpose is to promote the complexing agent to play a role by ultraviolet light. Therefore, the step of omitting the ultraviolet light again in Comparative Example 5 has a worse elimination effect than Comparative Example 4.

[0105] The mechanism is analyzed as follows:

[0106] 1) Curing Kinetics: All three indicators met the standards for all samples within three days, and within two days, five of six samples met all three indicators, with one sample only showing a soluble fluorine level slightly above 10 mg / L (10.33 mg / L). In fact, phosphogypsum can be shipped after only two days of curing.

[0107] 2) Solidification efficiency: The soluble phosphorus in Fujian Zijin phosphogypsum is reduced to 0.01 mg / L, and the soluble fluorine is as low as about 5 mg / L.

[0108] 3) Stable data: After curing, there will be no reverse release of phosphorus and fluorine. The soluble phosphorus reacts with the agent to form a stable calcium hydrogen phosphate precipitate, and the soluble fluorine forms a stable calcium fluoride precipitate.

[0109] This project focuses on the economical, efficient, and harmless treatment of phosphogypsum, a hot topic in environmental engineering. The research content meets the practical and technical requirements for phosphogypsum pollution control in my country. By manipulating synthesis conditions to construct a series of calcium-based composite alkali materials, these materials are applied to control soluble phosphorus, soluble fluorine, moisture content, and pH in phosphogypsum, transforming it from a Class II solid waste to a Class I solid waste at a material cost of 15-25 yuan per ton. This project aims to provide a technical solution for the harmless treatment of phosphogypsum and lay the foundation for subsequent research on its resource utilization.

[0110] The content of harmful components in the solidified phosphogypsum leachate and phosphogypsum samples shall be based on the "GB 8978-1996 Integrated Wastewater Discharge Standard" and "GB 18599-2020 General Industrial Solid Waste Storage and Filling Pollution Control Standard" as the detection and judgment standards for treated phosphogypsum. After treatment, the soluble phosphorus of phosphogypsum is not higher than 0.5ppm, the soluble fluorine is not higher than 10ppm, and the pH is 6-9.

[0111] A "base neutralization-photocatalytic-excited emulsion" relay has been developed for the synergistic harmless treatment of phosphogypsum. Calcium hydroxide is first used to neutralize and precipitate fluorine and phosphorus, followed by titanium dioxide photocatalytic degradation of residual organic matter, reducing the emission of toxic gases such as hydrogen sulfide, achieving "multi-level purification" of phosphogypsum. By adding reagents, soluble fluorine and phosphorus in phosphogypsum can be efficiently removed, while balancing treatment costs and resource utilization. This method effectively adsorbs heavy metal ions and organic pollutants in phosphogypsum and, through ultraviolet light or even sunlight, oxidizes and decomposes organic pollutants in phosphogypsum into harmless substances such as carbon dioxide and water, significantly improving the utilization efficiency of phosphogypsum. This method is simple, efficient, easy to operate, and requires minimal equipment. It can utilize ultraviolet light or even sunlight as a light source, reducing the production of harmful sulfur- and nitrogen-containing gases such as hydrogen sulfide. It is economical, environmentally friendly, safe, and efficient, conforming to the fundamental principles of green chemical development and possessing promising research and industrial application prospects.

[0112] The present invention independently develops a new type of lime composite agent material, which breaks through the technical defects of traditional lime agents. It compounds lime powder with active components, dispersants, etc., improves the emulsification degree of lime powder and thus enhances the "activity" of lime milk, and prepares a calcium-based composite alkali material with high alkalinity. On this basis, it is applied to the harmless disposal of phosphogypsum, and its effectiveness, economy and stability are further evaluated, providing a new technical solution for the harmless disposal of phosphogypsum. In addition, compared with the traditional neutralization treatment of phosphogypsum process, the addition of ultraviolet light irradiation step, this process flow can not only physically adsorb soluble fluorine and phosphorus ions, but also photogenerated holes and the generated superoxide radicals can destroy the molecular structure of organic matter in phosphogypsum, promote the decomposition of organic matter, and decompose it into harmless CO2, H2O, etc., which is beneficial to inhibit sulfate-reducing bacteria in an anaerobic environment in the later stage and reduce the generation of hydrogen sulfide. The present invention can effectively improve the defects of poor curing effect in traditional processes, and can effectively adsorb heavy metal ions in phosphogypsum, photocatalytically decompose organic matter present in phosphogypsum, etc. At the same time, on this basis, the component of activator A was optimized, and modified polyacrylamide microspheres were added as complexing agents to promote the complexation of modified polyacrylamide microspheres with the carrier adsorbent under ultraviolet irradiation, thereby improving the curing effect.

[0113] Although the present invention has been described in detail above using general descriptions and specific embodiments, it will be apparent to those skilled in the art that modifications and improvements may be made thereto. Therefore, such modifications and improvements, without departing from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

Claims

1. A lime composite agent for harmless treatment of phosphogypsum based on an inorganic formula, characterized in that: Includes the following components: Activator A, buffer B and lime, wherein the mass ratio of the activator A, buffer B and lime is (1-10): (0.5-5): (5-25); After being dissolved in an appropriate amount of water, the solid content of the stimulator A in the composite medicine is (0.3-3)%.

2. The lime composite agent for harmless treatment of phosphogypsum based on an inorganic formula according to claim 1, characterized in that: in, The activator A comprises a carrier stabilizer, a carrier adsorbent, a photosensitive catalyst and a complexing agent, wherein the mass ratio of the carrier stabilizer, the carrier adsorbent, the photosensitive catalyst and the complexing agent is (10-20): (1-5): (0.5-2): (1-3).

3. The lime composite agent for harmless treatment of phosphogypsum based on an inorganic formula according to claim 2, characterized in that: in, The mass ratio of the carrier stabilizer, the carrier adsorbent, the photosensitive catalyst and the complexing agent is 15:3:1:

2.

4. The lime composite agent for harmless treatment of phosphogypsum based on an inorganic formula according to claim 2, characterized in that: in, The carrier stabilizer is bentonite or clay, the carrier adsorbent is biochar, activated carbon or modified activated carbon, the photosensitive catalyst is titanium dioxide or zinc oxide, and the complexing agent is modified polyacrylamide microspheres.

5. The lime composite agent for harmless treatment of phosphogypsum based on an inorganic formula according to claim 1, characterized in that: in, Buffer B is a trivalent aluminum source compound, which is preferably selected from inorganic aluminum salts, coordinated aluminum complexes or dissociable trivalent aluminum complex salts with sustained release and pH stability, preferably aluminum hydroxide, γ-alumina, sodium metaaluminate and its derivatives.

6. A method for preparing a lime composite agent for harmless treatment of phosphogypsum based on an inorganic formula, for producing the lime composite agent for harmless treatment of phosphogypsum based on an inorganic formula as claimed in any one of claims 1 to 5, characterized in that: The steps include: 1) Add the carrier stabilizer, carrier adsorbent, photosensitive catalyst and complexing agent to a mixing container in proportion, add an appropriate amount of water to dissolve, stir at room temperature at a stirring speed of 150-260 rpm, and stir for 1-2 hours until the mixture is uniform to obtain a mixed solution A; 2) adding buffer B to the mixed solution A in 1) according to the proportion and stirring at room temperature at a speed of 200-300 rpm for 0.5-1 h until the mixture is uniformly mixed to obtain a mixed solution B; 3) Add lime to the mixed solution in 2) according to the proportion, stir at room temperature, at a stirring speed of 150-200 rpm, for 0.5-1 hour until the mixture is uniform, and let it stand for 6-24 hours to obtain the composite agent.

7. Use of the inorganic-formulated lime composite reagent for harmless treatment of phosphogypsum according to any one of claims 1 to 5 in the harmless disposal of phosphogypsum.

8. The use according to claim 7, characterized in that Add the composite agent to the new material phosphogypsum, and the mass ratio of phosphogypsum to the composite agent is 100: (1-15), stir at room temperature, the stirring time is 2-3h, the stirring speed is 250-450rpm, and ultraviolet irradiation is performed during the stirring process, and the irradiation intensity is 5-10mW / cm 2 , then let it stand for 3-6 hours; Start stirring again for 2-3 hours at room temperature. During the stirring process, perform UV irradiation at an intensity of 10-100 mW / cm 2 , then let it sit until the process is complete.

9. The use according to claim 8, characterized in that The moisture content of the phosphogypsum is 12-25%.

10. The use according to claim 8, characterized in that The mass ratio of the phosphogypsum to the composite agent is 100:13.

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