Pollutant passivating agent and method for passivating phosphogypsum-based artificial aggregate by using pollutant passivating agent

Abstract

The invention discloses a pollutant passivating agent and a method for passivating phosphogypsum-based artificial aggregate by using the pollutant passivating agent. The pollutant passivating agent comprises the following components in parts by weight: 65-75 parts of a composite passivating agent, 15-20 parts of an active exciting agent, 10-15 parts of a waterproof agent, 2-5 parts of an early strength agent and 0.1-1 part of a water reducing agent, wherein the total weight of the pollutant passivating agent is 100 parts by weight; the composite passivator comprises an inorganic passivator and an organic passivator. Pollutants in the high-dosage ardealite-based aggregate are cured through the pollutant passivating agent, the leaching concentration of the pollutants in the ardealite-based artificial aggregate is reduced, and the worry of the ardealite aggregate on environmental pollution in the application of the ardealite aggregate in projects such as road construction and constructional engineering is relieved; meanwhile, the early strength of the high-content phosphogypsum-based aggregate is improved.

Description

Technical Field

[0001] The invention relates to the technical field of pollutant solidification, in particular to a pollutant passivator and a method for passivating phosphogypsum-based artificial aggregate. Background Art

[0002] Phosphogypsum is a byproduct of the phosphating industry. Every ton of phosphoric acid produced produces about 5 tons of phosphogypsum. Phosphogypsum is mainly composed of calcium sulfate dihydrate (CaSO4·2H2O), containing about 5-6% of impurities such as phosphorus, fluorine, heavy metals and residual acid, making it difficult to use directly. At present, the main disposal method for phosphogypsum is stockpiling. However, since phosphogypsum contains impurities such as phosphorus, fluorine and heavy metals, a large amount of stockpiling will cause water and soil pollution. At present, the historical stockpile of phosphogypsum in my country exceeds 500 million tons, the annual new amount is about 7,000 tons, and the comprehensive utilization rate is less than 40%.

[0003] Making artificial aggregates by pressing phosphogypsum is a new method for the comprehensive utilization of phosphogypsum. The pressed phosphogypsum-based artificial aggregates are oval and flat in appearance, with a hard surface, and can absorb a large amount of phosphogypsum, alleviating the environmental pollution caused by the large-scale storage of phosphogypsum.

[0004] However, existing phosphogypsum-based artificial aggregates are difficult to apply in large-scale engineering projects due to the following problems:

[0005] First, pollutants in phosphogypsum-based artificial aggregates (especially fluorine and phosphorus in phosphogypsum) are easily leached out, endangering the surrounding environment;

[0006] Second, phosphorus impurities in phosphogypsum include three forms: soluble phosphorus, insoluble phosphorus and eutectic phosphorus. If phosphogypsum participates in the hydration reaction, soluble phosphorus reacts with calcium ions to form insoluble phosphates, which cover the surface of phosphogypsum and hinder the continued dissolution reaction of phosphogypsum, reducing the strength of phosphogypsum products, resulting in generally lower strength of phosphogypsum-based artificial aggregates;

[0007] Third, the presence of soluble fluorine in phosphogypsum will shorten the setting time of phosphogypsum, resulting in weakening of the molecular forces between crystals, coarsening of crystals, and loose structure, thereby reducing the strength of phosphogypsum. Summary of the invention

[0008] In view of the shortcomings of the prior art, the present invention proposes a pollutant passivator and a method for passivating phosphogypsum-based artificial aggregates. The pollutants in the phosphogypsum-based artificial aggregates are solidified by the passivator, the leaching concentration of pollutants in the phosphogypsum-based artificial aggregates is reduced, and the performance of the phosphogypsum-based artificial aggregates is improved.

[0009] To achieve the above purpose, the present invention is a pollutant passivator designed for solidifying pollutants in phosphogypsum-based artificial aggregates, which is particularly characterized in that, based on 100 parts by weight of the total weight of the pollutant passivator, the pollutant passivator comprises the following components: 65 to 75 parts by weight of a composite passivator, 15 to 20 parts by weight of an active stimulant, 10 to 15 parts by weight of a waterproofing agent, 2 to 5 parts by weight of an early strength agent, and 0.1 to 1 part by weight of a water reducing agent;

[0010] The composite passivator comprises an inorganic passivator and an organic passivator. The inorganic passivator is composed of one or more of sodium lignosulfonate, calcium nitrate, polyaluminium chloride and polyaluminium ferric chloride; the organic passivator is composed of one or more of methyltriethoxysilane, ethyltriethoxysilane, triethanolamine and calcium formate.

[0011] Furthermore, the inorganic passivating agent is a composite of one or more of 10% to 15% by weight of sodium lignosulfonate, 10% to 15% by weight of calcium nitrate, 20% to 25% by weight of polyaluminium chloride, and 20% to 25% by weight of polyaluminium chloride iron;

[0012] The organic passivator is composed of one or more of 5% to 10% by weight of methyltriethoxysilane, 5% to 10% by weight of ethyltriethoxysilane, 10% to 15% by weight of triethanolamine and 10% to 15% by weight of calcium formate.

[0013] Furthermore, the activation activator is composed of one or more of 40% to 50% by weight of slag powder, 20% to 25% by weight of silica fume, 10% to 15% by weight of cement, and 15% to 20% by weight of carbide slag.

[0014] Furthermore, the waterproofing agent is composed of one or more of 25% to 30% by weight of sodium silicate, 30% to 35% by weight of aluminum sulfate, and 35% to 40% by weight of sodium methyl silicate.

[0015] Furthermore, the early strength agent is composed of one or more of 20% to 25% by weight of magnesium sulfate, 25% to 30% by weight of calcium chloride, 25% to 30% by weight of sodium sulfate, and 25% to 30% by weight of sodium acetate.

[0016] Furthermore, the water reducer is composed of one or more of 30% to 35% by weight of sodium aminosulfonate, 30% to 35% by weight of sodium aliphatic hydroxysulfonate, and 30% to 35% by weight of naphthalene-based high-efficiency water reducer.

[0017] The present invention also provides a method for passivating phosphogypsum-based artificial aggregate using a pollutant passivator, which is particularly characterized in that the method uses the above-mentioned pollutant passivator and comprises the following steps:

[0018] S1) drying and sieving the original phosphogypsum, and then grinding it with a ball mill to obtain fine phosphogypsum;

[0019] S2) mixing and stirring the ground phosphogypsum, slag powder, cement clinker and water, and adding a pollutant passivator to prepare a mixture;

[0020] Based on 100 parts by weight of the dry total weight of the phosphogypsum-based artificial aggregate, the phosphogypsum-based artificial aggregate comprises the following components: 80-85 parts by weight of ground phosphogypsum, 10-14 parts by weight of slag powder, and 5-9 parts by weight of cement clinker;

[0021] The pollutant passivating agent accounts for 0.3-2% of the total dry weight of the phosphogypsum-based artificial aggregate;

[0022] Water accounts for 8-10% of the total dry weight of the phosphogypsum-based artificial aggregate;

[0023] S3) adding the stirred mixture into a granulator and performing extrusion granulation to obtain fine light aggregate;

[0024] S4) adding the fine light aggregate obtained by the primary extrusion into a roller gear granulator, and performing secondary extrusion granulation to obtain secondary aggregate;

[0025] S5) screening the secondary aggregate to remove small and unformed aggregate to obtain formed aggregate;

[0026] S6) The formed aggregate is subjected to heat preservation and moisture preservation curing, thereby improving the solidification performance of pollutants in the phosphogypsum-based artificial aggregate.

[0027] Furthermore, in S1), the specific surface area of ​​the ground phosphogypsum is 500-600m 2 / g.

[0028] Furthermore, in S4), the pressure of the secondary extrusion granulation is 85-90 MPa, and the rotation speed is 15-17 rpm; in S5), the particle size of the formed aggregate is 10-20 mm.

[0029] Furthermore, in S6), the curing conditions are a temperature of 20° C., a relative humidity of 95%, and a curing time of 7 to 56 days.

[0030] The principle that the pollutant passivator designed in the present invention can improve the performance of phosphogypsum-based artificial aggregate is as follows:

[0031] 1. The pollutant passivator in the present invention includes an inorganic passivator and an organic passivator. The sodium lignosulfonate, polyaluminium chloride and polyaluminium ferric chloride in the inorganic passivator combine with the hydroxide in the mixture at an early stage to reduce the generation of Ca(OH)2 and make the free Ca 2+ Increase, calcium nitrate will also provide some Ca 2+ , so that the aggregate produces more calcium aluminate, improves the early strength of the aggregate, and at the same time, excessive Ca 2+ Combine with soluble P and F in the mixture to solidify P and F;

[0032] Methyltriethoxysilane and ethyltriethoxysilane in the organic passivator form covalent bonds with calcium silicate hydrate in the form of Si-O-Si. These chemical bonds interact to form a strong cross-linking network between the organic silane and calcium silicate hydrate, improving the pollutant solidification performance of phosphogypsum-based aggregates; triethanolamine and calcium formate in the organic passivator promote each other with inorganic chloride salts, accelerate the hydration reaction of aggregates, and form a relatively stable cementing body to solidify pollutants at an early stage;

[0033] 2. The pollutant passivating agent in the present invention includes an active activator, a waterproofing agent, an early strength agent, and a water reducing agent, wherein the active activator (slag powder, silica fume, cement, carbide slag) can fully activate the activity of the phosphogypsum volcanic ash, fully hydrate the phosphogypsum, and generate a large amount of hydrated calcium silicate and hydrated calcium aluminate;

[0034] Waterproofing agents (sodium silicate, aluminum sulfate, sodium methyl silicate) combine with the hydroxide in the aggregate to generate a large amount of colloid substances that are insoluble in water. The calcium aluminate hydrate produced by stimulating phosphogypsum will further react to generate calcium sulfoaluminate crystals with certain expansion. These colloids and crystals fill the capillaries formed in the aggregate during the hardening process, increase the density of the aggregate, and thus improve the waterproofing effect;

[0035] Early strength agents (magnesium sulfate, calcium chloride, mirabilite, sodium acetate) can increase the alkalinity of the system and increase the early strength of solid waste group aggregates by promoting the formation of hydrated calcium aluminate;

[0036] Water reducers (sodium aminosulfonate, sodium aliphatic hydroxysulfonate, naphthalene-based high-efficiency water reducers) can reduce water consumption and slow down the overflow or evaporation of excess water from the slurry during the hardening process of phosphogypsum-based artificial aggregates, thereby leaving a large number of micropores and cracks inside the hardened body and improving aggregate performance;

[0037] 3. In the method of passivating phosphogypsum-based artificial aggregates using a pollutant passivator of the present invention, the original phosphogypsum is dried and screened, and then ground phosphogypsum is obtained by mechanical modification to fully release the aggregate effect and activity of the material, and then mixed with slag, cement clinker and passivator in proportion, and granulated with water, so that the ground phosphogypsum and slag can fully exert their volcanic ash activity in the alkaline environment provided by the cement clinker and in the high silicon-aluminum environment provided by the passivator, forming a dense cemented body with a certain strength, so that the prepared aggregate has a strong pollutant passivation performance;

[0038] 4. In the method of passivating phosphogypsum-based artificial aggregates with pollutant passivators of the present invention, two extrusion moldings are used for granulation, so that the prepared aggregates can achieve higher cylinder pressure strength and packing density within a shorter curing period, shortening the curing period and helping the solidification of pollutants.

[0039] The advantages of the present invention are as follows:

[0040] 1. The crushing index of the aggregate prepared by the present invention meets the standard of crushed stone for construction, and can be widely used in C30-C60 grade concrete and highway subgrade materials. The pressed phosphogypsum-based water-resistant artificial aggregate has low toxic leaching concentration, high early strength and low water absorption;

[0041] 2. The pollutant passivator in the present invention is a powdered admixture with simple production process, low cost, easy packaging and transportation, and can better solve the problem of inconvenient metering during use, and has broad application prospects;

[0042] 3. The phosphogypsum content in the phosphogypsum-based artificial aggregate of the present invention is large and has a high utilization rate, which can effectively alleviate the problem of large-scale accumulation of phosphogypsum;

[0043] The pollutant passivator of the present invention and the method for passivating phosphogypsum-based artificial aggregate thereof solidify pollutants in high-dosage phosphogypsum-based aggregates through the pollutant passivator, reduce the concentration of pollutants leached in the phosphogypsum-based artificial aggregates, and alleviate the concerns about environmental pollution caused by the application of phosphogypsum aggregates in road construction, building projects and other projects; at the same time, the early strength of high-dosage phosphogypsum-based aggregates is improved, and the resource utilization of phosphogypsum is increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A schematic diagram of primary granulation of phosphogypsum-based artificial aggregate prepared by using the pollutant passivator of the present invention;

[0045] Figure 2 A schematic diagram of secondary granulation of phosphogypsum-based artificial aggregate prepared by using the pollutant passivator of the present invention;

[0046] Figure 3It is a comparison chart of the physical and chemical properties of the phosphogypsum-based artificial aggregates prepared in Examples 1 to 6 and the comparative example. DETAILED DESCRIPTION

[0047] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0048] The present invention discloses a pollutant passivator, which is used for solidifying pollutants in phosphogypsum-based artificial aggregates. The pollutant passivator comprises the following components based on 100 parts by weight of the total weight of the pollutant passivator: 65-75 parts by weight of a composite passivator, 15-20 parts by weight of an active stimulator, 10-15 parts by weight of a waterproofing agent, 2-5 parts by weight of an early strength agent, and 0.1-1 parts by weight of a water reducing agent.

[0049] The composite passivator comprises an inorganic passivator and an organic passivator. The inorganic passivator is composed of one or more of sodium lignosulfonate, calcium nitrate, polyaluminium chloride and polyaluminium ferric chloride; the organic passivator is composed of one or more of methyltriethoxysilane, ethyltriethoxysilane, triethanolamine and calcium formate.

[0050] Specifically, the inorganic passivating agent is a composite of one or more of 10% to 15% by weight of sodium lignosulfonate, 10% to 15% by weight of calcium nitrate, 20% to 25% by weight of polyaluminium chloride, and 20% to 25% by weight of polyaluminium chloride iron;

[0051] The organic passivator is composed of one or more of 5% to 10% by weight of methyltriethoxysilane, 5% to 10% by weight of ethyltriethoxysilane, 10% to 15% by weight of triethanolamine and 10% to 15% by weight of calcium formate.

[0052] Specifically, the activation activator is composed of one or more of 40% to 50% by weight of slag powder, 20% to 25% by weight of silica fume, 10% to 15% by weight of cement, and 15% to 20% by weight of carbide slag.

[0053] Specifically, the waterproofing agent is composed of one or more of 25% to 30% by weight of sodium silicate, 30% to 35% by weight of aluminum sulfate, and 35% to 40% by weight of sodium methyl silicate.

[0054] Specifically, the early strength agent is composed of one or more of 20% to 25% by weight of magnesium sulfate, 25% to 30% by weight of calcium chloride, 25% to 30% by weight of sodium sulfate, and 25% to 30% by weight of sodium acetate.

[0055] Specifically, the water reducer is composed of one or more of 30% to 35% by weight of sodium aminosulfonate, 30% to 35% by weight of sodium aliphatic hydroxysulfonate, and 30% to 35% by weight of naphthalene-based high-efficiency water reducer.

[0056] The present invention also provides a method for passivating phosphogypsum-based artificial aggregate using a pollutant passivator, using the above-mentioned pollutant passivator, comprising the following steps:

[0057] S1) drying and sieving the original phosphogypsum, and then grinding it with a ball mill to obtain fine phosphogypsum.

[0058] Specifically, the specific surface area of ​​the ground phosphogypsum is 500-600m 2 / g.

[0059] S2) mixing and stirring the ground phosphogypsum, slag powder, cement clinker and water, and adding a pollutant passivator to prepare a mixture.

[0060] Based on 100 parts by weight of the dry total weight of the phosphogypsum-based artificial aggregate, the phosphogypsum-based artificial aggregate comprises the following components: 80-85 parts by weight of ground phosphogypsum, 10-14 parts by weight of slag powder, and 5-9 parts by weight of cement clinker;

[0061] The pollutant passivating agent accounts for 0.3-2% of the total dry weight of the phosphogypsum-based artificial aggregate;

[0062] Water accounts for 8-10% of the total dry weight of the phosphogypsum-based artificial aggregate.

[0063] Specifically, the slag powder has a specific surface area of ​​≥500m 2 / kg, the particle size with a screening pass rate of 50% is less than 15um; the specific surface area of ​​cement clinker is ≥330m 2 / kg, the particle size with a screening pass rate of 50% is less than 35um.

[0064] Specifically, the ground phosphogypsum, slag powder, cement clinker and water are added into a mixer and mixed and stirred evenly, the stirring speed is 55 to 65 revolutions per minute, and the stirring time is 6 to 10 minutes.

[0065] S3) adding the stirred mixture into a granulator for extrusion granulation to obtain fine light aggregate.

[0066] Specifically, the mixture is uniformly added into a granulator, and the mixture is squeezed out of the grinding disc by active wheel rolling to obtain fine aggregate of 4 to 6 mm, and then the wheel rolling is repeated twice to finally obtain fine light aggregate of 4 to 6 mm with a certain strength.

[0067] S4) adding the fine light aggregate obtained by the primary extrusion into a fully automatic double-roll gear granulator for secondary extrusion granulation to obtain secondary aggregate;

[0068] Specifically, the stirred mixture is uniformly added to the fully automatic roller gear granulator through a conveyor belt, and the active roller and the passive roller rotate at the same speed and in different directions, so that the mixture is extruded and formed in the groove between the two rollers. The pressure of the secondary extrusion granulation is 85-90MPa and the speed is 15-17 rpm.

[0069] S5) Screening the secondary aggregate to remove small and unformed aggregate to obtain formed aggregate.

[0070] Specifically, the aggregate is sent to the screening equipment through a conveyor belt, the prepared aggregate is screened, and the broken and unformed aggregate is removed to obtain the formed aggregate, and the particle size of the formed aggregate is 10 to 20 mm.

[0071] S6) The formed aggregate is subjected to heat preservation and moisture preservation curing, thereby improving the solidification performance of pollutants in the phosphogypsum-based artificial aggregate.

[0072] Specifically, the curing conditions are a temperature of 20° C., a relative humidity of 95%, and a curing time of 7 to 56 days.

[0073] In this embodiment, the phosphogypsum used is taken from a phosphogypsum yard, has a gray-black powder solid appearance, is weakly acidic, and its main components are shown in Table 1, its fluorine and phosphorus contents are shown in Table 2, and its heavy metal content is shown in Table 3; the slag powder used is taken from a mine, has a gray-white powder solid appearance, and its main components are shown in Table 1; the cement clinker used is ordinary P.O42.5 silicate cement.

[0074] Table 1 Chemical composition of raw materials

[0075]

[0076]

[0077] Table 2 Fluorine and phosphorus content and pH in phosphogypsum

[0078] Fluoride content F(μg) Phosphorus concentration mg / L PH Phosphogypsum 30.72 5.735 6.12

[0079] Table 3 Heavy metals in phosphogypsum (mg / kg)

[0080] As Cd Cr Ni Pb Zn Hg 0 0 5.579 2.462 2.195 8.058 6.633

[0081] Example 1

[0082] The pollutant passivator of the present invention is used to passivate phosphogypsum-based artificial aggregate, and the formula thereof is calculated by weight percentage: 80.5% of modified ground phosphogypsum, 12% of slag powder, 7.5% of cement, 0.5% of pollutant passivator, and then 9% of water of the total weight of the formula is added. The pollutant passivator is compounded by 65% ​​by weight of a composite passivator, 15% by weight of an active stimulator, 14.5% by weight of a waterproofing agent, 5% by weight of an early strength agent, and 0.5% by weight of a water reducing agent.

[0083] The composite passivator is composited by 10% by weight of sodium lignosulfonate, 10% by weight of calcium nitrate, 20% by weight of polyaluminium chloride, 20% by weight of polyaluminium ferric chloride, 15% by weight of ethyltriethoxysilane, 15% by weight of triethanolamine and 10% by weight of calcium formate.

[0084] The active activator is composited by 45% by weight of slag powder, 25% by weight of silica fume, 15% by weight of cement and 15% by weight of carbide slag.

[0085] The waterproofing agent is composed of 30% by weight of sodium silicate, 35% by weight of aluminum sulfate and 40% by weight of sodium methyl silicate.

[0086] The early strength agent is composed of 20% by weight of magnesium sulfate, 30% by weight of calcium chloride, 25% by weight of sodium sulfate and 25% by weight of sodium acetate.

[0087] The water reducing agent is composed of 35% by weight of sodium aminosulfonate, 35% by weight of sodium aliphatic hydroxysulfonate and 30% by weight of naphthalene-based high-efficiency water reducing agent.

[0088] The method of passivating phosphogypsum-based artificial aggregate using the pollutant passivator of the present invention is as follows:

[0089] S1) Pretreatment and mechanical modification of original phosphogypsum: The original phosphogypsum was dried at 50°C for 20 h, passed through a 50-mesh sieve, and then ground in a ball mill for 40 min to obtain a phosphogypsum with a specific surface area of ​​500-600 m 2 / g of finely ground phosphogypsum;

[0090] S2) preparing a mixture: mixing the ground phosphogypsum powder, slag powder and cement clinker uniformly, then adding a pollutant passivator, and mixing uniformly to obtain a mixture;

[0091] 3) Granulation: Add the mixture into the granulator, squeeze the mixture out of the grinding disc through the active wheel rolling to obtain fine aggregates of 4 to 6 mm, and then repeat the wheel rolling twice to finally obtain fine and light aggregates of 4 to 6 mm with a certain strength;

[0092] Then, the fine light aggregate obtained from the primary granulation is uniformly fed into the fully automatic double-roll gear granulator through a conveyor belt, and the active roller and the passive roller rotate at the same speed and in different directions, so that the fine light aggregate is extruded and formed in the groove between the two rollers, and the formed secondary aggregate is obtained after screening;

[0093] S4) Curing: The formed aggregate obtained after screening is placed in a standard curing box, maintained at a temperature of 20° C. and a relative humidity of 95% for 28 days to obtain phosphogypsum-based low-pollutant leaching aggregate.

[0094] Example 2

[0095] The pollutant passivator of the present invention is used to passivate the phosphogypsum-based artificial aggregate, and the formula thereof is calculated by weight percentage as follows: 80.5% of modified ground phosphogypsum, 12% of slag powder, 7.5% of cement, 1% of the pollutant passivator, and then 9% of the total weight of water is added. The composition of the pollutant passivator is the same as that of Example 1.

[0096] The method of passivating phosphogypsum-based artificial aggregate using the pollutant passivator of the present invention is the same as that in Example 1.

[0097] Example 3

[0098] The pollutant passivator of the present invention is used to passivate the phosphogypsum-based artificial aggregate, and the formula thereof is calculated by weight percentage as follows: 80.5% of modified ground phosphogypsum, 12% of slag powder, 7.5% of cement, 1.5% of the pollutant passivator, and then 9% of the total weight of water is added. The components of the pollutant passivator are the same as those in Example 1.

[0099] The method of passivating phosphogypsum-based artificial aggregate using the pollutant passivator of the present invention is the same as that in Example 1.

[0100] Example 4

[0101] The pollutant passivator of the present invention is used to passivate phosphogypsum-based artificial aggregate, and the formula thereof is calculated by weight percentage: 80.5% of modified ground phosphogypsum, 12% of slag powder, 7.5% of cement, 0.5% of pollutant passivator, and then 9% of the total weight of water is added.

[0102] The pollutant passivator is composed of 75% by weight of a composite passivator, 5% by weight of an active stimulator, 14.5% by weight of a waterproofing agent, 5% by weight of an early strength agent, and 0.5% by weight of a water reducing agent.

[0103] The weight percentages of the composite passivator, active activator, waterproofing agent, early strength agent and water reducing agent are the same as those in Example 1.

[0104] The method of passivating phosphogypsum-based artificial aggregate using the pollutant passivator of the present invention is the same as that in Example 1.

[0105] Example 5

[0106] The pollutant passivator of the present invention is used to passivate phosphogypsum-based artificial aggregate, and the formula thereof is calculated as follows by weight percentage: 80.5% of modified ground phosphogypsum, 12% of slag powder, 7.5% of cement, 1% of pollutant passivator, and then 9% of the total weight of water is added.

[0107] The pollutant passivator is composed of 75% by weight of a composite passivator, 5% by weight of an active stimulator, 14.5% by weight of a waterproofing agent, 5% by weight of an early strength agent, and 0.5% by weight of a water reducing agent.

[0108] The weight percentages of the composite passivator, active stimulator, waterproofing agent, early strength agent and water reducing agent are the same as those in Example 1.

[0109] The method of passivating phosphogypsum-based artificial aggregate using the pollutant passivator of the present invention is the same as that in Example 1.

[0110] Example 6

[0111] The pollutant passivator of the present invention is used to passivate phosphogypsum-based artificial aggregate, and the formula thereof is calculated by weight percentage: 80.5% of modified ground phosphogypsum, 12% of slag powder, 7.5% of cement, 1.5% of pollutant passivator, and then 9% of the total weight of water is added.

[0112] The pollutant passivator is composed of 75% by weight of a composite passivator, 5% by weight of an active stimulator, 14.5% by weight of a waterproofing agent, 5% by weight of an early strength agent, and 0.5% by weight of a water reducing agent.

[0113] The weight percentages of the composite passivator, active stimulator, waterproofing agent, early strength agent and water reducing agent are the same as those in Example 1.

[0114] The method of passivating phosphogypsum-based artificial aggregate using the pollutant passivator of the present invention is the same as that in Example 1.

[0115] Comparative Example

[0116] A phosphogypsum-based artificial aggregate has the following formula by weight percentage: 80.5% of modified ground phosphogypsum, 12% of slag powder, 7.5% of cement, and then 9% of the total weight of water.

[0117] The preparation method of the phosphogypsum-based artificial aggregate is the same as that in Example 1.

[0118] Results

[0119] The phosphogypsum-based artificial aggregates prepared in Examples 1 to 6 and the comparative example were tested for their physical and chemical properties. The results are shown in Tables 4 and Figure 3 .

[0120] Table 4 Properties of gypsum-based artificial aggregate

[0121]

[0122]

[0123] It can be seen from Table 4 that after the pollutant passivator in the present invention is applied to the phosphogypsum-based aggregate, the toxic leaching of the phosphogypsum-based aggregate after curing for 28 days, the fluorine (F) leaching concentration is reduced by 30% to 40% compared with that without the addition of the pollutant passivator, the leaching concentration of phosphorus is undetectable, and the total phosphorus and fluoride ion concentrations of the leachate prepared according to the "Solid Waste Leaching Toxicity Leaching Method Horizontal Oscillation Method" (HJ 557-2010) are far lower than the first-level standard limit of the "Comprehensive Sewage Discharge Standard" (GB 8978-1996); the 28-day strength of the phosphogypsum-based aggregate is increased by 20% to 30% compared with that without the addition of the pollutant passivator; the water absorption rate of the phosphogypsum-based aggregate is reduced by 5% to 10% compared with that without the addition of the pollutant passivator.

[0124] Therefore, the pollutant passivator in the present invention has a good passivation effect on the pollutants in the phosphogypsum-based artificial aggregate, and also improves its strength to a certain extent. However, when the dosage of the pollutant passivator increases, the effect of improving the aggregate strength will decrease.

[0125] In this embodiment, the aggregate particle size cured for 28 days is 10-25 mm continuously graded, which meets the standard of crushed stone and pebbles for construction in GBT 14685-2011; meets the requirements of Class II crushed stone in JTG TF50-2011 Technical Specifications for Highway Bridge and Culvert Construction, and can be used for the preparation of concrete with strength grade C10-C30 and frost resistance, impermeability or other requirements.

[0126] The pollutant passivator of the present invention and the method for passivating phosphogypsum-based artificial aggregate thereof solidify pollutants in high-dosage phosphogypsum-based aggregates through the pollutant passivator, reduce the concentration of pollutants leached in the phosphogypsum-based artificial aggregates, and alleviate the concerns about environmental pollution caused by the application of phosphogypsum aggregates in road construction, building projects and other projects; at the same time, the early strength of high-dosage phosphogypsum-based aggregates is improved, and the resource utilization of phosphogypsum is increased.

[0127] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A pollutant passivator for solidifying pollutants in phosphogypsum-based artificial aggregates, characterized in that: Based on the total weight of the pollutant passivator being 100 parts by weight, the pollutant passivator comprises the following components: 65 to 75 parts by weight of a composite passivator, 15 to 20 parts by weight of an active stimulant, 10 to 15 parts by weight of a waterproofing agent, 2 to 5 parts by weight of an early strength agent, and 0.1 to 1 part by weight of a water reducing agent; The composite passivator comprises an inorganic passivator and an organic passivator. The inorganic passivator is composed of one or more of sodium lignosulfonate, calcium nitrate, polyaluminium chloride and polyaluminium ferric chloride; the organic passivator is composed of one or more of methyltriethoxysilane, ethyltriethoxysilane, triethanolamine and calcium formate.

2. The pollutant passivator according to claim 1, characterized in that: The inorganic passivating agent is a composite of one or more of 10% to 15% by weight of sodium lignosulfonate, 10% to 15% by weight of calcium nitrate, 20% to 25% by weight of polyaluminium chloride, and 20% to 25% by weight of polyaluminium ferric chloride; The organic passivator is composed of one or more of 5% to 10% by weight of methyltriethoxysilane, 5% to 10% by weight of ethyltriethoxysilane, 10% to 15% by weight of triethanolamine and 10% to 15% by weight of calcium formate.

3. The pollutant passivator according to claim 2, characterized in that: The active activator is composed of one or more of 40% to 50% by weight of slag powder, 20% to 25% by weight of silica fume, 10% to 15% by weight of cement, and 15% to 20% by weight of carbide slag.

4. The pollutant passivator according to claim 3, characterized in that: The waterproofing agent is composed of one or more of 25% to 30% by weight of sodium silicate, 30% to 35% by weight of aluminum sulfate, and 35% to 40% by weight of sodium methyl silicate.

5. The pollutant passivating agent according to claim 4, characterized in that: The early strength agent is composed of one or more of 20% to 25% by weight of magnesium sulfate, 25% to 30% by weight of calcium chloride, 25% to 30% by weight of sodium sulfate, and 25% to 30% by weight of sodium acetate.

6. The pollutant passivator according to claim 5, characterized in that: The water reducing agent is composed of one or more of 30% to 35% by weight of sodium aminosulfonate, 30% to 35% by weight of sodium aliphatic hydroxysulfonate, and 30% to 35% by weight of naphthalene-based high-efficiency water reducing agent.

7. A method for passivating phosphogypsum-based artificial aggregates with a pollutant passivator, characterized in that: Using the pollutant passivating agent as claimed in any one of claims 1 to 6 comprises the following steps: S1) drying and sieving the original phosphogypsum, and then grinding it with a ball mill to obtain fine phosphogypsum; S2) mixing and stirring the ground phosphogypsum, slag powder, cement clinker and water, and adding a pollutant passivator to prepare a mixture; Based on 100 parts by weight of the dry total weight of the phosphogypsum-based artificial aggregate, the phosphogypsum-based artificial aggregate comprises the following components: 80-85 parts by weight of ground phosphogypsum, 10-14 parts by weight of slag powder, and 5-9 parts by weight of cement clinker; The pollutant passivating agent accounts for 0.3-2% of the total dry weight of the phosphogypsum-based artificial aggregate; Water accounts for 8-10% of the total dry weight of the phosphogypsum-based artificial aggregate; S3) adding the stirred mixture into a granulator and performing extrusion granulation to obtain fine light aggregate; S4) adding the fine light aggregate obtained by the primary extrusion into a roller gear granulator, and performing secondary extrusion granulation to obtain secondary aggregate; S5) screening the secondary aggregate to remove small and unformed aggregate to obtain formed aggregate; S6) The formed aggregate is subjected to heat preservation and moisture preservation curing, thereby improving the solidification performance of pollutants in the phosphogypsum-based artificial aggregate.

8. The method for passivating phosphogypsum-based artificial aggregates with a pollutant passivator according to claim 7, characterized in that: S1), the specific surface area of ​​the ground phosphogypsum is 500-600m 2 / g.

9. The method for passivating phosphogypsum-based artificial aggregates with a pollutant passivator according to claim 8, characterized in that: In S4), the pressure of the secondary extrusion granulation is 85-90 MPa, and the rotation speed is 15-17 rpm; in S5), the particle size of the formed aggregate is 10-20 mm.

10. The method for passivating phosphogypsum-based artificial aggregates with a pollutant passivator according to claim 9, characterized in that: In S6), the curing conditions are a temperature of 20° C., a relative humidity of 95%, and a curing time of 7 to 56 days.

Images