Low-cost phosphogypsum efficient curing agent and harmless treatment method

Abstract

The invention discloses a phosphogypsum efficient curing agent and a phosphogypsum harmless treatment method. The curing agent is composed of an exciting agent, a modifying agent and an adsorbent. The exciting agent comprises one or a combination of more of calcium oxide and calcium hydroxide; the modifier comprises one or a combination of more of magnesium oxide, manganese oxide, aluminum oxide, ferric oxide, lanthanum oxide, magnesium chloride, manganese chloride, aluminum chloride, ferric chloride, lanthanum chloride and the like; the adsorbent comprises one or a combination of more of calcium silicate, aluminum silicate, kaolinite, potassium feldspar, calcium metasilicate and the like. The curing agent provided by the invention can efficiently cure soluble phosphorus, fluorine and heavy metal ions in ardealite whether the curing agent and ardealite are mixed and stirred for reaction or a dump leaching process is adopted for treatment, and the curing rates of the soluble phosphorus, fluorine and heavy metal ions in the ardealite reach 99%, 95% and 99%.

Description

Technical Field

[0001] The present invention belongs to the technical field of harmless treatment of phosphogypsum, and particularly relates to a low-cost and highly efficient solidifying agent for phosphogypsum and a harmless treatment method. Background Art

[0002] Phosphogypsum is a large amount of industrial solid waste generated in the production process of wet-process phosphoric acid. The global annual discharge exceeds 300 million tons, and the annual discharge in China is about 80 million tons, with a comprehensive utilization rate of less than 40%. Its main component is calcium sulfate dihydrate (CaSO4·2H2O), and it contains harmful impurities such as phosphorus (P2O5), fluorine (F - )), organic matter and heavy metals (such as Cd, Pb, As, etc.). The long-term stacking of phosphogypsum not only occupies land resources, but the leached soluble phosphorus, fluorine and heavy metals will pollute the soil and groundwater, leading to ecological risks. For example, fluoride ions in phosphogypsum can enter crops through the food chain, resulting in excessive fluoride content in agricultural products; heavy metals may leach into water bodies, threatening human health.

[0003] At present, the resource utilization of phosphogypsum mainly focuses on the building materials field (such as gypsum boards, roadbed materials), but due to problems such as high impurity content and low solidification efficiency, the application range is limited. For example, when phosphogypsum is used for road bases, traditional cement-based solidifying agents have the defects of slow low-temperature solidification and insufficient compressive strength; when used for building materials, residual phosphorus and fluorine will inhibit cement hydration, resulting in a decrease in the strength of the products. Therefore, developing an efficient and rapid solidifying agent to achieve the harmless treatment of phosphogypsum is the key to promoting its resource utilization.

[0004] In the traditional lime neutralization method for treating phosphogypsum, soluble phosphorus, fluorine and heavy metal ions react with calcium hydroxide to form insoluble precipitates. Experimental results show that the lime neutralization method has a slow solidification rate and low efficiency. Therefore, it is necessary to explore new efficient solidifying agents to further improve the solidification rate of soluble phosphorus, fluorine and heavy metal ions to achieve the harmless treatment of phosphogypsum. Summary of the Invention

[0005] One of the purposes of the present invention is to provide a low-cost and highly efficient solidifying agent for phosphogypsum, which can solidify soluble phosphorus, fluorine and heavy metal elements in phosphogypsum at low cost and high efficiency.

[0006] Another purpose of the present invention is to provide a harmless treatment method for phosphogypsum using the above solidifying agent.

[0007] The present invention provides a highly efficient solidifying agent for phosphogypsum, which is composed of an activator, a modifier and an adsorbent; the particle size is 200-400 mesh.

[0008] The activator includes one or more combinations of calcium oxide and calcium hydroxide;

[0009] The modifier includes one or a combination of more than one of magnesium oxide, manganese oxide, aluminum oxide, iron oxide, lanthanum oxide, magnesium chloride, manganese chloride, aluminum chloride, iron chloride, lanthanum chloride, etc.;

[0010] The adsorbent includes one or a combination of more than one of calcium silicate, aluminum silicate, kaolinite, potassium feldspar, calcium metasilicate, etc.

[0011] The present invention also provides a method for harmless treatment of phosphogypsum using the curing agent. The curing agent is treated by one or a combination of more than one of in-situ heap leaching or mixing and stirring, and then aging treatment is carried out to obtain the cured phosphogypsum, so as to solidify the soluble phosphorus, fluorine and heavy metal ions in the phosphogypsum.

[0012] The mixing and stirring specifically is: mixing and stirring the curing agent and phosphogypsum, and the mass ratio of phosphogypsum to water is 10:(1 - 2). After the reaction is complete, the mixed and stirred phosphogypsum is obtained.

[0013] Further, the initial soluble phosphorus mass fraction of the phosphogypsum is 0.1% - 2%; the initial soluble fluorine mass fraction is 0.1% - 2%; the initial heavy metal ion mass fraction is 0.05% - 1%.

[0014] Further, during the mixing and stirring treatment process, the mass ratio of phosphogypsum to the activator in the curing agent is 100:(1 - 3), the mass ratio of phosphogypsum to the modifier in the curing agent is 1000:(1 - 5), and the mass ratio of the phosphogypsum to the adsorbent in the curing agent is 1000:(1 - 3).

[0015] Further, the stirring rate of the mixing and stirring treatment is 60 - 180 r / min, and the stirring time is 15 - 40 min.

[0016] Further, the reaction temperature of phosphogypsum and the curing agent is 10 - 50 °C.

[0017] Further, the aging treatment time is 1 - 3 days.

[0018] Further, the soluble phosphorus concentration in the cured phosphogypsum is less than 0.5 mg / L; the soluble fluorine concentration is less than 5 mg / L; the heavy metal ion concentration is less than 0.1 mg / L.

[0019] The beneficial effects of the present invention:

[0020] (1) The harmless method for phosphogypsum provided by the present invention adopts an innovative formula, and has a higher curing efficiency compared with traditional curing methods. Compared with traditional treatment processes, the cost of the curing agent is reduced to 16 - 22 yuan / ton;

[0021] (2) The harmless treatment method of phosphogypsum provided by the present invention can adopt the method of mixing and stirring the curing agent with phosphogypsum or the heap leaching process for treatment, and both can achieve good curing effects;

[0022] (3) When the curing agent provided by the present invention is used to treat phosphogypsum by the harmless treatment method, the curing rates of soluble phosphorus, fluorine and heavy metal ions can reach more than 99%, 95% and 99% respectively;

[0023] (4) The raw materials in the curing agent provided by the present invention are pollution-free and harmless to the environment, and will not cause environmental hazards and other impacts on the later use of phosphogypsum, reducing the harm of phosphogypsum, being beneficial to the harmless treatment of resources, facilitating the resource utilization of phosphogypsum, reducing resource waste, and bringing good economic benefits. Description of the Drawings

[0024] Figure 1 It is a broken line graph of the curing rates of soluble phosphorus, fluorine and heavy metal ions after treating phosphogypsum in Example 1;

[0025] Figure 2 It is a broken line graph of the curing rates of soluble phosphorus, fluorine and heavy metal ions after treating phosphogypsum in Example 2. Detailed Embodiments

[0026] To more clearly show the purpose, technical solutions and advantages of the invention, the following further details the present invention in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] Example 1

[0028] The curing agent provided by the present invention is mixed with phosphogypsum and then stirred with water for 30 minutes, wherein the mass ratio of phosphogypsum to water is 10:1, the stirring speed is 100 r / min, and the stirring temperature is 25 °C;

[0029] The curing agent is composed of calcium oxide, aluminum chloride, magnesium chloride and calcium metasilicate; the mass ratio of phosphogypsum to calcium oxide, aluminum chloride, magnesium chloride and calcium metasilicate is 100:2:0.1:0.1:0.1;

[0030] The sample obtained after the reaction is aged for 3 days. The sample is sampled every day, the sampled sample is dried, and the dried sample is fully leached with water and then filtered. The residual amounts of soluble phosphorus, fluorine and heavy metal ions in the filtrate are tested. The curing rate results of each day of aging are as Figure 1 shown, and the residual amounts of soluble phosphorus, fluorine and heavy metal ions in the sample after 3 days of aging are shown in Table 1.

[0031] Table 1 Residual amounts of soluble phosphorus, fluorine and heavy metal ions after 3 days of aging in Example 1

[0032]

[0033] In this example, the cost of the curing agent is 19 yuan per ton.

[0034] From Figure 1 It can be obtained that after 3 days of aging, the curing rates of soluble phosphorus, fluorine and heavy metal ions in phosphogypsum are 99%, 95% and over 99% respectively.

[0035] Example 2

[0036] The curing agent provided by the present invention is used for heap leaching treatment with phosphogypsum, the mass ratio of phosphogypsum to water is 10:2, and the actual temperature is 25 °C;

[0037] The curing agent is composed of calcium oxide, aluminum chloride, magnesium chloride and calcium metasilicate; the mass ratio of phosphogypsum to calcium oxide, aluminum chloride, magnesium chloride and calcium metasilicate is 100:2:0.1:0.1:0.1;

[0038] The sample obtained after the reaction is aged for 3 days. The sample is sampled every day, and the sampled sample is dried. After the dried sample is fully leached with water and filtered, the residual amounts of soluble phosphorus, fluorine and heavy metal ions in the filtrate are tested. The curing rate results of each day of aging are as Figure 2 shown, and the residual amounts of soluble phosphorus, fluorine and heavy metal ions in the sample after 3 days of aging are shown in Table 2.

[0039] Table 2 Residual amounts of soluble phosphorus, fluorine and heavy metal ions after treating phosphogypsum by the curing agent heap leaching process in Example 2

[0040]

[0041] In this example, the cost of the curing agent is 22 yuan per ton.

[0042] From Figure 2 It can be obtained that after 3 days of aging, the curing rates of soluble phosphorus, fluorine and heavy metal ions in phosphogypsum are as Figure 2 shown, which are 97%, 94% and over 98% respectively.

[0043] Comparative Example 1

[0044] A method for stabilizing / curing soluble phosphorus and fluorine in phosphogypsum. The treatment agent used includes calcium carbonate (CaCO3), magnesium carbonate (MgCO3), calcium hydroxide (Ca(OH)2) and polydimethylsiloxane. The method includes the following steps:

[0045] 1) Add a mixture of calcium carbonate, magnesium carbonate and calcium hydroxide under stirring. The weight ratio of calcium carbonate, magnesium carbonate and calcium hydroxide is 1:1:1. The weight ratio of the mixture to phosphogypsum is 1:100, and the stirring rate is 100 r / min.

[0046] 2) Add polydimethylsiloxane under stirring conditions. The weight-volume ratio of phosphogypsum to polydimethylsiloxane is 10:1, the stirring rate is 100 r / min, and the stirring time is 2 h. After the reaction, the solidified phosphogypsum is obtained.

[0047] After testing, the solidification rates of soluble phosphorus and fluorine in the solidified phosphogypsum are 63.22% and 83.02% respectively.

[0048] Comparative Example 2

[0049] A curing agent for solidifying and removing soluble phosphorus and soluble fluorine in phosphogypsum and its application. The method includes the following steps: The solid-liquid ratio is 2:1, where the solid phase is phosphogypsum and the liquid phase is the curing agent. The curing agent is 1.2 wt% calcium hydroxide and 0.03 wt% polyacrylamide. Mix the curing agent with phosphogypsum and stir for 2 min, let it stand and age for 24 h, then filter, dry the filtered phosphogypsum, add water to the dried phosphogypsum sample and stir well, and then filter to test the residual amounts of soluble phosphorus and soluble fluorine in the filtrate.

[0050] After testing, under these process conditions, the solidification rates of soluble phosphorus and fluorine are 87.47% and 91.86% respectively.

[0051] It can be seen from the results comparison of Examples 1-2 and Comparative Examples 1-2 that the curing agent provided by the present invention can not only be applied to the mixing stirring and heap leaching processes, but also the curing effect is significantly higher than that of the existing curing agents. At the same time, the cost of the curing agent provided by the present invention is significantly less than that of the existing curing agents or processes, and it is suitable for large-scale implementation and use.

Claims

1. An efficient solidifying agent for phosphogypsum, characterized in that, The curing agent is composed of an activator, a modifier and an adsorbent; the particle size is 200 to 400 mesh.

2. The high-efficiency phosphogypsum curing agent according to claim 1, characterized in that The activator includes one or more combinations of calcium oxide and calcium hydroxide; the modifier includes one or more combinations of magnesium oxide, manganese oxide, aluminum oxide, iron oxide, lanthanum oxide, magnesium chloride, manganese chloride, aluminum chloride, iron chloride and lanthanum chloride; the adsorbent includes one or more combinations of calcium silicate, aluminum silicate, kaolinite, potassium feldspar and calcium metasilicate.

3. A method for harmless treatment of phosphogypsum using the phosphogypsum high-efficiency curing agent described in any one of claims 1 or 2, characterized in that, The curing agent is treated by one or more combinations of in-situ heap leaching or mixing and stirring, and then aged to obtain the cured phosphogypsum, so as to fix the soluble phosphorus, fluorine and heavy metal ions in the phosphogypsum.

4. The method for harmless treatment of phosphogypsum according to claim 3, characterized in that, The specific mixing and stirring is as follows: the curing agent is mixed and stirred with phosphogypsum, and the mass ratio of phosphogypsum to water is 10:(1-2). After the reaction is complete, the mixed and stirred phosphogypsum is obtained.

5. The method for harmless treatment of phosphogypsum according to claim 4, characterized in that, The initial mass fraction of soluble phosphorus in the phosphogypsum is 0.1% - 2%; the initial mass fraction of soluble fluorine is 0.1% - 2%; the initial mass fraction of heavy metal ions is 0.05% - 1%.

6. The method for harmless treatment of phosphogypsum according to claim 4, characterized in that During the mixing and stirring process, the mass ratio of phosphogypsum to the activator in the curing agent is 100:(1-3), the mass ratio of phosphogypsum to the modifier in the curing agent is 1000:(1-5), and the mass ratio of the phosphogypsum to the adsorbent in the curing agent is 1000:(1-3).

7. The method for harmless treatment of phosphogypsum according to claim 4, characterized in that The stirring rate of the mixing and stirring treatment is 60 - 180 r / min, and the stirring time is 15 - 40 min.

8. The method for harmless treatment of phosphogypsum according to claim 4, characterized in that, The reaction temperature of phosphogypsum and the curing agent is 10 - 50 °C.

9. The method for harmless treatment of phosphogypsum according to claim 3, wherein The aging time is 1 - 3 days.

10. The method for harmless treatment of phosphogypsum according to claim 3, wherein, The concentration of soluble phosphorus in the cured phosphogypsum is less than 0.5 mg / L; the concentration of soluble fluorine is less than 5 mg / L; the concentration of heavy metal ions is less than 0.1 mg / L.

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