Green low-carbon uranium leaching tailings filling material and preparation method thereof

Abstract

The application provides a green low-carbon uranium tailing leaching filling material and a preparation method thereof, and belongs to the technical field of mine filling and low-radioactivity solid waste disposal. The filling material comprises uranium tailings, cementitious material, lime, slump retaining agent and water, wherein the cementitious material comprises cement clinker, phosphorous slag powder, slag powder and silica fume; and the raw materials are mixed through specific steps, so that the synergistic effect among the raw materials is maximally enhanced, the fixation of nuclides and the strength of the filling material are maximally improved. The application adopts multi-source active solid waste as the main component of the filling cementitious material, which can not only inhibit the reverse acid of the uranium tailings, greatly improve the strength and late stability of the filling body, reduce the cost, but also effectively control the release and migration of radioactive nuclides; the utilization rate of the uranium tailings solid waste in the filling material is high, the value of the solid waste in the cementitious material is low, the source is wide, the low-carbon and environment-friendly disposal of the uranium tailings can be realized, and the application has good application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mine filling and low-level radioactive solid waste disposal, and particularly relates to a green low-carbon acid leaching uranium tailings filling material and a preparation method thereof. BACKGROUND

[0002] Uranium tailings are a large amount of solid waste produced after the hard rock uranium mine ore is extracted and acid leaching of uranium on the ground. A large amount of sulfuric acid and long-lived radionuclides are left in the uranium tailings, which are harmful. Under the background of "double carbon", the global peaceful use of nuclear energy is accelerating, and the demand for natural uranium is increasing. The total amount of uranium tailings continues to increase, which makes the mine face more severe environmental and safety pressure.

[0003] Currently, the disposal of uranium tailings mainly relies on surface tailings storage. During the stacking process, not only a large amount of land is occupied, but also the release and migration of hazardous elements in uranium tailings into water, soil and air will pose a threat to the ecological environment and human health. At the same time, the tailings storage faces high maintenance and management costs during service and after retirement. In addition, solidification and stabilization is also a method for disposing uranium tailings. Patent document CN117383901A discloses a uranium tailings solidification agent and a solidification method. The solidification material used in the method is composed of mine powder, sodium silicate, river sand, uranium tailings and water. The uranium tailings solidification body obtained by the method has the characteristics of high strength and stable performance. However, in the method, the mass ratio of cementing material to aggregate, and the mass ratio of mine powder to sodium silicate are 1:1-3 and 2-5:1 respectively. There are problems such as low utilization rate of uranium tailings, high consumption of activator, high solidification cost, large land occupation and complex daily maintenance, which makes it difficult to implement in production.

[0004] In recent years, the cemented filling technology based on tailings and other mine solid wastes has been widely used in mines at home and abroad. This technology can make full use of uranium tailings to control the potential collapse of goaf, tailings dam and surface environmental pollution in uranium mines, and has the advantages of low cost, high utilization rate of tailings and environmental friendliness, making large-scale utilization of uranium tailings possible. Ordinary Portland cement is the most commonly used filling cementing material in mines. However, since the uranium tailings are completely soaked with sulfuric acid, the sulfuric acid will be released slowly in a humid environment. The filling body prepared by using uranium tailings and cement has serious reverse acid, and has problems such as low early strength of filling body, serious degradation and disintegration in later period, and high risk of radionuclide release and migration. Therefore, it is of great significance to develop a green, low-carbon, efficient and low-cost uranium tailings filling material and preparation method for filling in goaf, which is important for the reduction, pollution control of large industrial solid waste such as low-level radioactive uranium tailings, and the sustainable development and utilization of uranium resources. SUMMARY

[0005] In view of the technical problems in the background art, the present application provides a green and low-carbon uranium tailings leaching filling material and a preparation method thereof, aiming to solve the problems of existing uranium tailings filling materials, such as serious acid resistance, low early strength, serious degradation and disintegration in later period, environmental pollution caused by radionuclide release and migration, and low utilization rate and high cost of uranium tailings.

[0006] In a first aspect, the embodiments of the present application provide a green and low-carbon uranium tailings leaching filling material, characterized in that it comprises uranium tailings, cementitious material, lime, slump retaining agent and water; wherein the cementitious material comprises, in terms of mass percentage:

[0007] 30-40% of cement clinker, 60-70% of phosphorous slag powder;

[0008] Alternatively, 15-50% of cement clinker, 30-80% of phosphorous slag powder, 0-15% of slag powder and 0-10% of silica fume.

[0009] In the technical solution of the embodiments of the present application, the superimposed effect generated by the reaction of the advantages and disadvantages of the multi-source active solid waste and the uranium tailings is utilized, which not only can inhibit the acid resistance of the uranium tailings, greatly improve the strength and later stability of the filling body, reduce the cost, but also can effectively control the release and migration of radioactive nuclides. The uranium tailings solid waste utilization rate in the filling material of the present application is high, and the solid waste content in the cementitious material is large, low in value, and widely available, which is conducive to low-carbon, green and low-cost production of uranium mines, and has good application prospect.

[0010] In some embodiments, the uranium tailings are solid waste after uranium is extracted by sulfuric acid leaching agent in surface heap leaching process or agitation leaching process, and the pH value is 3.5-4.5, and the maximum particle size is ≤10mm.

[0011] In this embodiment, the uranium tailings are soaked with sulfuric acid and contain a large amount of soluble uranium. When used as filling aggregate, SO4 2- will slowly seep out for a long time, wherein the seeped SO4 2- can react with a large amount of Ca 2+ and OH - released by cement clinker and lime when water is added to generate gypsum.

[0012] In some embodiments, the phosphorous slag powder is a powder prepared by grinding granulated electric furnace phosphorous slag, and has a specific surface area of ≥300m 2 / kg, a 28d activity index of ≥85%, a P2O5 content of ≤5%, and both the radioactivity indexes IRa and Ir of ≤1.

[0013] In this embodiment, on the one hand, during the preparation of the filling slurry, the dissolution of residual phosphoric acid in the phosphorus slag powder reacts with the soluble nuclides in the uranium tailings to form insoluble minerals, achieving chemical fixation of the nuclides and reducing the leaching and migration risk of uranium from the source. On the other hand, the newly generated Ca(OH)2 and gypsum in the filling material destroy the Si-O-Si bond, Al-O-Si bond, and Al-O-Al bond on the surface of the glass body of the phosphorus slag powder, causing slow release of [SiO4] 4- , [AlO4] 5- , etc., and combining with Ca 2+ to form hydrated calcium silicate and hydrated calcium aluminate, and the hydrated calcium aluminate further reacts with gypsum to produce ettringite; this process mainly occurs in the later hydration period, and the effect is to consume the gypsum and Ca(OH)2 generated in the middle and later periods of the uranium tailings filling material, inhibit the reverse acid of the uranium tailings, reduce the content of gypsum, increase the amount and performance of hydrated calcium silicate, enhance the strength and stability of the filling body in the middle and later periods, and simultaneously achieve secondary physical fixation and stabilization of the nuclides through adsorption and encapsulation of the hydration products.

[0014] In some embodiments, the slag powder is a ground granulated blast furnace slag powder with a specific surface area of ≥400 m 2 / kg, a 28d activity index of ≥95%, a SO3 content of ≤4%, and both the radioactivity indexes IRa and Ir of ≤1.

[0015] In this embodiment, the activity of the slag powder is higher than that of the phosphorus slag powder, and after the slag powder is added, the newly generated Ca(OH)2 and gypsum in the filling material break the Si-O-Si bond, Al-O-Si bond, and Al-O-Al bond on the surface of the glass body of the slag powder, release [SiO4] 4- , [AlO4] 5- , etc., and combine with Ca 2+ to form hydrated calcium silicate and hydrated calcium aluminate, and the hydrated calcium aluminate reacts with gypsum to produce ettringite. This process mainly occurs in the early and middle hydration periods, and the effect is to produce more hydrated calcium silicate and ettringite in the early and middle hydration periods, thereby improving the early and middle period strength of the filling body. The synergistic effect of the slag powder and the phosphorus slag powder reduces the total amount of gypsum and Ca(OH)2 in the filling material, weakens the corrosion of sulfates on the filling body, improves the full-age strength and stability of the filling body, and further enhances the fixation and stabilization of the nuclides.

[0016] In some embodiments, the silica fume specifically refers to a powder collected in the flue during the smelting of ferrosilicon alloy, with a specific surface area of ≥15000 m 2 / kg, an activity index of ≥105%, and a SiO2 content of ≥85%.

[0017] In this embodiment, the activity of silica fume is higher than that of slag powder. After adding silica fume, the newly generated Ca(OH)2 in the filling material destroys the Si-O-Si bond on the surface of the silica fume glass body, so that it is quickly released [SiO4] 4- , and combines with Ca 2+ to form calcium silicate hydrate. This process mainly occurs in the early hydration stage, and the effect is to produce more calcium silicate hydrate in the early hydration stage, improve the early strength of the filling body and the density of the matrix. The addition of silica fume increases the early hydration products in the filling body, which can enhance the plugging effect of the original fissure channel of the uranium tailings particles, prevent free water from entering the interior of the uranium tailings particles, inhibit the release of SO4 2- , reduce the formation of gypsum in the middle and late stages, and at the same time, the synergistic effect with phosphorus slag powder and slag powder enhances the full-age strength, stability and fixation and stabilization of the nuclides of the filling body.

[0018] In some embodiments, the specific surface area of the cement clinker is 300-400 m 2 / kg, and the mass percentage of silicate minerals is greater than 66%.

[0019] In this embodiment, C3S, C2S and C3A in the cement clinker dissolve a large amount of Ca(OH)2, [SiO4] 4- , [Al(OH)4] - , etc. in water. Part of the Ca(OH)2 consumes the SO4 2- dissolved from the uranium tailings to produce gypsum, and the newly generated gypsum slows down the hydration reaction of the cement clinker, which is used to reduce the loss of the slump of the filling material slurry. C3S in the cement clinker hydrates to form calcium silicate hydrate before C2S, and at the same time, the newly generated gypsum reacts with C3A to generate ettringite, so that the filling material begins to solidify and form strength. The remaining Ca(OH)2 and newly generated gypsum create conditions for the continuous hydration reaction of phosphorus slag powder, slag powder or silica fume in the filling material, and promote the hydration to generate more calcium silicate hydrate.

[0020] In some embodiments, the lime is quicklime powder, the CaO content is ≥90%, and the addition amount is 0.08-0.15% of the dry weight of the uranium tailings.

[0021] In this embodiment, lime dissolves a large amount of Ca(OH)2 in water. Part of the Ca(OH)2 reacts with a large amount of SO4 2- dissolved from the uranium tailings in the early stage to generate gypsum, and the remaining Ca(OH)2 provides an alkaline environment and a calcium source for the hydration of phosphorus slag powder, slag powder or silica fume, and ensures the continuous hydration reaction of phosphorus slag powder, slag powder or silica fume.

[0022] In some embodiments, the slump retaining agent comprises: a superplasticizer and / or a high performance water reducing agent; the superplasticizer comprises one or more of sulfamate, naphthalene series, anthracene series, melamine resin, ketone aldehyde condensate superplasticizer, the high performance water reducing agent comprises polycarboxylic acid high performance water reducing agent, and the slump retaining agent is added in an amount of 0.2-0.8% of the mass of the cementitious material.

[0023] In this embodiment, on the one hand, the slump retaining agent is used to improve the fluidity of the filling slurry, reduce the unit water consumption in the filling material, and reduce the segregation and bleeding rate of the filling slurry. At the same time, after the water consumption is reduced, the free water content in the filling body is greatly reduced, SO4 2- released from the inside of the uranium tailings particles is more difficult, and the uranium tailings acid is inhibited. On the other hand, the total amount of the newly generated gypsum in the filling body is reduced, and the hydration reaction with the cementitious material cooperatively improves the full-age strength, stability and fixation and stabilization of the nuclides of the filling body.

[0024] In a second aspect, the embodiment of the present application provides a preparation method of a green low-carbon acid leaching uranium tailings filling material, comprising the following steps:

[0025] S1. mixing the uranium tailings, the phosphorous slag powder and water, and fully stirring to obtain a mixed slurry;

[0026] S2. sequentially adding the cement clinker, the slag, the silica fume, the lime and the slump retaining agent into the mixed slurry, and fully stirring to obtain the uranium tailings filling material.

[0027] In the technical scheme of the embodiment of the present application, the uranium tailings are first uniformly stirred with water, the sulfur-containing clay minerals on the surface of the uranium tailings are washed away with water, the particle surface becomes smoother, and the SO4 2- on the surface layer of the uranium tailings particles is maximally dissolved. The slurry forms an acidic environment, in addition, the soluble uranium and the like in the uranium tailings particles can be maximally dissolved. Then the phosphorous slag powder is added, the residual phosphoric acid in the phosphorous slag powder can mineralize the soluble uranium and the like under weakly acidic conditions, and the chemical fixation efficiency of the soluble uranium and the like is maximally improved; then the cement clinker, the slag powder, the silica fume, the lime and the slump retaining agent are sequentially added, a large amount of Ca(OH)2, [SiO4] 4- , [Al(OH)4] - and the like are dissolved in the stirring process, a part of the Ca(OH)2consumes the SO4 2- dissolved from the uranium tailings to generate gypsum; at the same time, the C3S and C3A in the cement clinker undergo hydration reaction, the filling material begins to solidify and form strength; the remaining Ca(OH)2and the newly generated gypsum create conditions for the continuous hydration reaction of the phosphorous slag powder, the slag powder or the silica fume in the filling material, and promote the hydration to generate more hydrated calcium silicate and the like, so as to improve the strength and the later stability of the filling body.

[0028] The above description is only a summary of the technical scheme of the present application. In order to more clearly understand the technical means of the present application, the specific embodiments of the present application can be implemented in accordance with the content of the description, and in order to make the above and other purposes, characteristics and advantages of the present application more obvious and easy to understand, the following specific embodiments of the present application are described. DETAILED DESCRIPTION

[0029] The embodiments of the technical scheme of the present application will be described in detail below. The following embodiments are only used to more clearly illustrate the technical scheme of the present application, and therefore only serve as examples, and cannot limit the protection scope of the present application.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "include" and "have" and any variations thereof in the specification and claims of the present application are intended to cover non-exclusive inclusion.

[0031] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application. The occurrence of the phrase in various places in the specification does not necessarily all refer to the same embodiment, nor is it necessarily independent or alternative embodiments to each other. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0032] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " in this paper generally represents that the front and rear associated objects are a "or" relationship.

[0033] In order to solve the problems of serious acid resistance of existing cement uranium tailings filling body, low early strength, serious degradation and disintegration in later period, environmental pollution caused by nuclide release and migration, low utilization rate of uranium tailings and high cost, the present application provides a green low-carbon acid leaching uranium tailings filling material and a preparation method thereof. The filling material in the present application comprises: uranium tailings, cement clinker, phosphorous slag powder, slag powder, silica fume, slump retaining agent and water. The present application uses multi-source active solid waste as the main component of the filling cementitious material, which not only can inhibit the acid resistance of uranium tailings, greatly improve the strength and later stability of the filling body, reduce the cost, but also can effectively control the release and migration of radioactive nuclides; the uranium tailings solid waste utilization rate of the filling material in the present application is high, and the value of the solid waste in the cementitious material is low and the source is wide, which can realize low-carbon and environment-friendly disposal of uranium tailings, and has good application prospect.

[0034] In one aspect, the embodiment of the present application provides a green low-carbon uranium tailings acid leaching filling material, which comprises uranium tailings, cementitious material, lime, slump retaining agent and water; the total mass of the uranium tailings, the cementitious material and the lime accounts for 77-83% of the mass of the uranium tailings filling material, and the mass ratio of the cementitious material to the uranium tailings is 1:4-1:25; wherein the cementitious material comprises, in percentage by mass:

[0035] 30-40% of cement clinker, 60-70% of phosphorous slag powder;

[0036] or, 15-50% of cement clinker, 30-80% of phosphorous slag powder, 0-15% of slag powder and 0-10% of silica fume.

[0037] In the technical scheme of the embodiment of the present application, the superposition effect generated by the reaction of the advantages and disadvantages of the multi-source active solid waste and the uranium tailings is utilized, so that the uranium tailings acid can be inhibited, the strength and the late stability of the filling body can be greatly improved, the cost can be reduced, and the release and migration of radionuclides can be effectively controlled. The utilization rate of the uranium tailings solid waste in the filling material of the present application is high, and the solid waste in the cementitious material has a large amount, a low value and a wide source, which is conducive to low-carbon, green and low-cost production of uranium mines and has a good application prospect.

[0038] Further, in some embodiments, the cementitious material comprises, in percentage by mass, 15-50% of cement clinker, 30-80% of phosphorous slag powder and 5-15% of slag powder.

[0039] In the technical scheme of the embodiment of the present application, under the action of Ca(OH)2 and gypsum, the slag powder releases a large amount of [SiO4] 4- , [AlO4] 5- , etc., and combines with Ca 2+ to form calcium silicate hydrate and calcium aluminate hydrate, and the calcium aluminate hydrate reacts with gypsum to produce ettringite. This process mainly occurs in the early and middle hydration periods, and can make up for the defect that the early and middle period strength of the filling body is low. In addition, the synergistic effect of the slag powder and the phosphorous slag powder reduces the total amount of gypsum and Ca(OH)2 in the filling material, which can weaken the corrosion of sulfates on the filling body and improve the full-age strength and stability of the filling body, and at the same time further improve the stable fixation of radionuclides.

[0040] Further, in some embodiments, the cementitious material comprises, in percentage by mass, 15-50% of cement clinker, 30-80% of phosphorous slag powder and 3-10% of silica fume.

[0041] In the technical scheme of the embodiment of the present application, under the action of Ca(OH)2, the silica fume rapidly releases [SiO4] 4- , and combines with Ca 2+Calcium silicate hydrate is formed. This process mainly occurs in the early hydration stage, compensates for the low early strength of the filling body, and improves the density of the matrix. In addition, calcium silicate hydrate blocks the original fissure channels on the surface of uranium tailings particles, prevents free water from entering the interior of uranium tailings particles, inhibits the release of SO4 2- , and reduces the formation of gypsum in the middle and later stages. The synergistic effect of phosphorus slag powder enhances the full-age strength, stability, and stable fixation of nuclides of the filling body.

[0042] Further, in some embodiments, the cementitious material includes 15-50% cement clinker, 30-80% phosphorus slag powder, 5-10% slag powder, and 3-10% silica fume by mass percentage.

[0043] In the technical solution of the embodiments of the present application, the slag powder reacts with Ca(OH)2 and gypsum to produce calcium silicate hydrate and calcium aluminate hydrate, and the calcium aluminate hydrate reacts with gypsum to produce ettringite, thereby improving the early and middle strength of the filling body. The added silica fume reacts with Ca(OH)2 to produce a large amount of calcium silicate hydrate in the early stage, thereby improving the early strength and density of the filling body. The synergistic effect of the two and the phosphorus slag powder enhances the full-age strength, stability, and stable fixation of nuclides of the filling body.

[0044] Further, in some embodiments, the uranium tailings are solid waste after using sulfuric acid leaching agent to extract uranium in the surface heap leaching process or the agitated leaching process, and the pH value is 3.5-4.5, and the maximum particle size is ≤10 mm.

[0045] In the technical solution of the embodiments of the present application, the uranium tailings are soaked with sulfuric acid and contain a large amount of soluble uranium. When used as filling aggregate, SO4 2- will slowly seep out for a long time, and the seeped SO4 2- can react with Ca 2+ and OH - released by the cement clinker and lime to generate a large amount of gypsum.

[0046] Further, in some embodiments, the phosphorus slag powder is a powder prepared by grinding granulated electric furnace phosphorus slag, the specific surface area is ≥300 m 2 / kg, the 28d activity index is ≥85%, the P2O5 content is ≤5%, and the radioactivity indexes IRa and Ir are both ≤1.

[0047] In the technical solution of the embodiments of the present application, on the one hand, during the preparation of the filling slurry, the dissolved phosphoric acid in the phosphorus slag powder reacts with the soluble nuclides in the uranium tailings to form insoluble minerals, thereby realizing the chemical fixation of the nuclides and reducing the leaching and migration risk of uranium from the source. On the other hand, the newly generated Ca(OH)2 and gypsum in the filling material destroy the Si-O-Si bond, Al-O-Si bond, and Al-O-Al bond on the surface of the glass body of the phosphorus slag powder, so that [SiO4]4- [AlO4] 5- , etc., and combine with Ca 2+ to form hydrated calcium silicate and hydrated calcium aluminate, and the hydrated calcium aluminate further reacts with gypsum to produce ettringite; this process mainly occurs in the later hydration period, and the effect is to consume the gypsum and Ca(OH)2 generated in the middle and later periods of the uranium tailings filling material, inhibit the reverse acid of the uranium tailings, reduce the content of gypsum, improve the quantity and performance of the hydrated calcium silicate, enhance the middle and later period strength and stability of the filling body, and simultaneously realize the secondary physical fixation and stabilization of the nuclides through the adsorption and encapsulation of the hydration products.

[0048] Further, in some embodiments, the slag powder is a ground powder of granulated blast furnace slag, with a specific surface area of ≥400 m 2 2 / g, a 28d activity index of ≥95%, a SO3 content of ≤4%, and both the radioactivity indexes IRa and Ir of ≤1.

[0049] In the technical solution of the embodiments of the present application, the activity of the slag powder is higher than that of the phosphorous slag powder, and after the slag powder is added, the newly generated Ca(OH)2 and gypsum in the filling material break the Si-O-Si bond, Al-O-Si bond and Al-O-Al bond on the surface of the slag powder glass body, release [SiO4] 4- , [AlO4] 5- , etc., and combine with Ca 2+ to form hydrated calcium silicate and hydrated calcium aluminate, and the hydrated calcium aluminate reacts with gypsum to produce ettringite. This process mainly occurs in the early and middle hydration period, and the effect is to produce more hydrated calcium silicate and ettringite in the early and middle hydration period, and improve the early and middle period strength of the filling body. The synergistic effect of the slag powder and the phosphorous slag powder reduces the total amount of gypsum and Ca(OH)2 in the filling material, can weaken the corrosion of sulfates on the filling body, improve the full age strength and stability of the filling body, and further improve the fixation and stabilization of the nuclides.

[0050] Further, in some embodiments, the silica ash specifically refers to a powder collected in the flue during the smelting of ferrosilicon alloy, with a specific surface area of ≥15000 m 2 2 / g, an activity index of ≥105%, and a SiO2 content of ≥85%.

[0051] In the technical solution of the embodiments of the present application, the activity of the silica ash is higher than that of the slag powder, and after the silica ash is added, the newly generated Ca(OH)2 in the filling material breaks the Si-O-Si bond on the surface of the silica ash glass body, makes it quickly release [SiO4] 4- , and combine with Ca 2+The calcium silicate hydrate is formed by combination. The process mainly occurs in the early hydration stage, and the effect is to produce more calcium silicate hydrate in the early hydration stage, improve the early strength of the filling body and the compactness of the matrix. The addition of silica fume increases the early hydration products in the filling body, which can enhance the plugging effect of the original crack channels on the surface of the uranium tailings particles, prevent free water from entering the interior of the uranium tailings particles, inhibit the release of SO4 2- , reduce the formation of gypsum in the middle and late stages, and at the same time, the synergistic effect with the phosphorus slag powder and the slag powder enhances the full-age strength, stability and fixation and stabilization of the nuclides of the filling body.

[0052] Further, in some embodiments, the specific surface area of the cement clinker is 300-400 m 2 / kg, and the mass percentage of silicate minerals is greater than 66%.

[0053] In the technical scheme of the embodiments of the present application, C3S, C2S and C3A in the cement clinker dissolve a large amount of Ca(OH)2, [SiO4] 4- , [Al(OH)4] - , etc. in water, part of the Ca(OH)2 consumes SO4 2- dissolved from the uranium tailings to produce gypsum, and the newly generated gypsum slows down the hydration reaction of the cement clinker, which is used to reduce the loss of the slump of the filling slurry. C3S in the cement clinker hydrates to form calcium silicate hydrate before C2S, and at the same time, the newly generated gypsum reacts with C3A to generate ettringite, and the filling material begins to solidify and form strength. The remaining Ca(OH)2 and the newly generated gypsum create conditions for the continuous hydration reaction of the phosphorus slag powder, the slag powder or the silica fume in the filling material, and promote the hydration to produce more calcium silicate hydrate, etc.

[0054] Further, in some embodiments, the lime is a quicklime powder, the CaO content is ≥90%, and the addition amount is 0.08-0.15% of the dry weight of the uranium tailings.

[0055] In the technical scheme of the embodiments of the present application, in this embodiment, a large amount of Ca(OH)2 is dissolved from the lime in water, part of the Ca(OH)2 reacts with a large amount of SO4 2- dissolved from the uranium tailings in the early stage to generate gypsum, and the remaining Ca(OH)2 provides an alkaline environment and a calcium source for the hydration of the phosphorus slag powder, the slag powder or the silica fume, and ensures the continuity of the hydration reaction of the phosphorus slag powder, the slag powder or the silica fume.

[0056] Further, in some embodiments, the slump retaining agent includes: a high efficiency water reducing agent and / or a high performance water reducing agent; the high efficiency water reducing agent includes one or more of sulfamate, naphthalene, anthracene, melamine resin, and ketone aldehyde condensate high efficiency water reducing agents, the high performance water reducing agent includes a polycarboxylic acid high performance water reducing agent, and the addition amount of the slump retaining agent is 0.2-0.8% of the mass of the cementitious material.

[0057] In the technical scheme of the embodiment of the present application, on the one hand, the slump retaining agent is used to improve the fluidity of the filling slurry, reduce the unit water consumption in the filling material, and reduce the segregation and bleeding rate of the filling slurry. At the same time, after the water consumption is reduced, the free water content in the filling body is greatly reduced, the SO4 2- released from the inside of the uranium tailings particles is more difficult, and the uranium tailings acid is inhibited. On the other hand, the total amount of the newly generated gypsum in the filling body is reduced, and the hydration reaction of the cementing material is cooperated to improve the full-age strength, stability and fixation and stabilization of the nuclides of the filling body.

[0058] In a second aspect, the embodiment of the present application provides a preparation method of a green low-carbon acid leaching uranium tailings filling material, comprising the following steps:

[0059] S1. mixing the uranium tailings, the phosphorous slag powder and water, and fully stirring to obtain a mixed slurry;

[0060] S2. sequentially adding the cement clinker, the slag, the silica fume, the lime and the slump retaining agent to the mixed slurry, and fully stirring to obtain the uranium tailings filling material.

[0061] In the technical scheme of the embodiment of the present application, the uranium tailings are first uniformly stirred with water, the sulfur-containing clay minerals on the surface of the uranium tailings are washed away with water, the particle surface becomes smoother, and the SO4 2- on the surface layer of the uranium tailings particles is maximally dissolved. The slurry forms an acidic environment, in addition, the soluble uranium and the like in the uranium tailings particles can be maximally dissolved. Then the phosphorous slag powder is added, the residual phosphoric acid in the phosphorous slag powder can mineralize the soluble uranium and the like under weakly acidic conditions, and the chemical fixation efficiency of the soluble uranium and the like is maximally improved; then the cement clinker, the slag powder, the silica fume, the lime and the slump retaining agent are sequentially added, a large amount of Ca(OH)2, [SiO4] 4- , [Al(OH)4] - and the like are dissolved in the stirring process, a part of the Ca(OH)2consumes the SO4 2- dissolved from the uranium tailings to generate gypsum; at the same time, the C3S and C3A in the cement clinker occur hydration reaction, the filling material begins to solidify and form strength; the remaining Ca(OH)2and the newly generated gypsum create conditions for the continuous hydration reaction of the phosphorous slag powder, the slag powder or the silica fume in the filling material, and promote the hydration to generate more hydrated calcium silicate and the like to improve the strength and the later stability of the filling body.

[0062] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and cannot be understood as a limitation on the present application. If the specific technology or condition is not specified in the embodiments, the technology or condition described in the literature in the art or according to the product manual is used. If the reagent or instrument is not specified by the manufacturer, it is a conventional product that can be obtained from the market.

[0063] Example 1

[0064] The embodiment provides a green low-carbon uranium tailings filling material and a preparation method thereof, and specifically comprises the following steps:

[0065] (1) The required raw materials are weighed according to the following proportions: 1000 parts of uranium tailings, 25.03 parts of cement clinker, 60.52 parts of phosphorous slag powder, 10.04 parts of slag, 4.95 parts of silica fume, 1 part of lime, 0.4 parts of polycarboxylic acid, and 274 parts of water;

[0066] (2) The weighed uranium tailings and phosphorous slag powder are put into a stirrer, and the weighed water is slowly added, and stirring is performed at a stirring rate of 80 r / min for 1 min;

[0067] (3) Then the weighed cement clinker, slag, silica fume, lime and polycarboxylic acid are sequentially and slowly added, and stirring is performed at a stirring rate of 80 r / min for 3 min, to obtain a uranium tailings filling material slurry.

[0068] The sources and performance parameters of the raw materials are as follows:

[0069] The uranium tailings are solid waste produced after uranium is extracted by a heap leaching process sulfuric acid leaching agent, are provided by a certain hard rock uranium heap leaching field, have a pH of 4.5, a moisture content of 9%, and a particle size distribution as shown in Table 1, and chemical components as shown in Table 2.

[0070] Table 1 Particle size distribution of uranium tailings

[0071]

[0072] Table 2 Chemical components of uranium tailings

[0073] Ingredients SiO2 CaO Al2O3 K2O SO3 Fe2O3 Na2O MgO U3O8 Content / % 68.92 3.43 7.52 2.03 1.98 1.05 0.32 0.51 0.013

[0074] The cement clinker is provided by Hunan Haisi Cement Co., Ltd., has a density of 3046 kg / m 3 , a specific surface area of 400 m 2 / kg, and a mass percentage of silicate minerals of 79.87%.

[0075] The phosphorous slag powder is taken from a phosphorus chemical enterprise in Guizhou Weng'an, has a density of 2828 kg / m 3 , a specific surface area of 306 m 2 / kg, a mass coefficient of 1.32, an alkaline coefficient of 1.19, an activity index of 88.5%, a P2O5 content of 4.6%, and both of the radioactivity indexes IRa and Ir are ≤1.

[0076] The slag powder is S95-grade slag provided by Wuhan Weishen Technology Development Co., Ltd., has a density of 2876 kg / m 3The specific surface area of the silica ash is 408 m 2 / kg, the mass coefficient is 2.01, the SO3 content is 2.42%, the alkaline coefficient is 1.07, the activity index is 98%, and the radioactivity indexes IRa and Ir are both ≤1.

[0077] The silica ash is provided by Henan Liurun New Material Co., Ltd., and the specific surface area of the silica ash is 20150 m 2 / kg, the activity index is 110%, and the SiO2 content is 96.25%.

[0078] The slump retaining agent is a polycarboxylic acid water reducing agent, and the CaO content in the lime powder is 95%.

[0079] Examples 2-9 and Comparative Examples 1-5

[0080] Examples 2-9 and Comparative Examples 1-5 each provide a green low-carbon acid leaching uranium tailings filling material and a preparation method thereof. Compared with Example 1, the difference lies in that the proportions of cement clinker, phosphorus slag powder, slag and silica ash in the filling cementitious material are different, and the specific amounts are shown in Table 3. Other steps are substantially the same as those of Example 1, and will not be described here again.

[0081] Table 3: Contents of each component in the cementitious material in Examples 2-9 and Comparative Examples 1-5

[0082] Example / Comparative Example Cement clinker (parts) Phosphorous slag powder (parts) Slag (parts) Silica fume (parts) Example 2 26.3 63.2 10.5 0 Example 3 23.7 56.8 9.5 10 Example 4 27.8 66.7 0 5.5 Example 5 23.5 56.5 15 5 Example 6 15 70 10 5 Example 7 25.6 61.4 8 5 Example 8 30 70 0 0 Example 9 40 60 0 0 Comparative Example 1 23 53 9 15 Comparative Example 2 23.1 54 20 2.9 Comparative Example 3 5 85 6.7 3.3 Comparative Example 4 80 20 0 0 Comparative Example 5 20 80 0 0

[0083] Comparative Example 6

[0084] This comparative example provides a green low-carbon acid leaching uranium tailings filling material and a preparation method thereof. Compared with Example 1, the difference lies in that no polycarboxylic acid slump retaining agent is added, and other steps are substantially the same as those of Example 1, and will not be described here again.

[0085] Comparative Example 7

[0086] This comparative example provides a green low-carbon acid leaching uranium tailings filling material and a preparation method thereof. Compared with Example 1, the difference lies in that the preparation steps of the filling material are different, i.e., the uranium tailings, cement clinker, phosphorus slag powder, slag, silica ash, lime and polycarboxylic acid are put into a mixer at the same time, and then water is slowly added. The mixture is stirred at a stirring speed of 80 r / min for 5 min to obtain a uranium tailings filling material slurry. Other steps are substantially the same as those of Example 1, and will not be described here again.

[0087] Comparative Example 8

[0088] The comparative example provides a green low-carbon uranium tailings filling material and a preparation method thereof. Compared with Example 1, the difference is that the cementing material is 42.5# ordinary portland cement; the uranium tailings filling material preparation steps are: weighing the raw materials according to the proportion, putting the uranium tailings, 42.5# ordinary portland cement and lime into a mixer, then slowly adding water, stirring at a stirring rate of 80 r / min for 5 min to obtain a uranium tailings filling slurry, and other steps are substantially the same as those of Example 1, which will not be repeated here.

[0089] The source and performance parameters of the 42.5# ordinary portland cement are as follows:

[0090] The 42.5# cement is provided by Hunan Conch Cement Co., Ltd., and the density is 2956 kg / m 3 , and the specific surface area is 364 m 2 / kg.

[0091] The bleeding rate and the slump and spread of the filling slurry in Examples 1-9 and Comparative Examples 1-8 are tested according to the “Test Method for Performance of Ordinary Concrete Mixture” (GB / T 50080-2016); and the setting time of the filling slurry is tested according to the “Standard Test Method for Basic Performance of Building Mortar” (JGJ / T 70-2009), and the test results are shown in Table 4.

[0092] Table 4 Performance test results of the filling slurry in Examples 1-9 and Comparative Examples 1-8

[0093]

[0094]

[0095] The filling slurry in Examples 1-9 and Comparative Examples 1-8 is poured into a cylindrical mold with a size of φ50 mm x H100 mm, and after demolding, the filling body test block is placed in a curing box (humidity is 95%, temperature is 20℃) for curing. The uniaxial compressive strength of the filling body test block is tested according to the “Technical Standard for Filling Engineering in Metal and Non-metal Mines” (GB / T 51450-2022) at 7d, 28d, 90d and 180d, and the test results are shown in Table 5.

[0096] Table 5 Strength test results of the filling body in Examples 1-9 and Comparative Examples 1-8

[0097]

[0098]

[0099] The step-by-step continuous extraction test was used to analyze the uranium content of the filling body of 7d, 28d and 90d age in examples 1-9 and comparative examples 1-8; then the nuclide leaching test was carried out on the curing 28d filling body test block according to the "low and medium level radioactive waste solidification body standard leaching test method" (GB / T7023-2011), and the leaching rate and leaching fraction of uranium in the filling body were calculated, and the test results are shown in Table 6.

[0100] Table 6: Test results of uranium leaching and radon release in the filling body of examples 1-9 and comparative examples 1-8

[0101]

[0102]

[0103] The solid waste content and material cost of the filling material in examples 1-9 and comparative examples 1-8 are shown in Table 7.

[0104] Table 7: Solid waste content and material cost of the filling material in examples 1-9 and comparative examples 1-8

[0105]

[0106] As can be seen from Table 4, the bleeding rate of examples 1-9 is between 1.5-5%, the slump is greater than 25cm, the setting time is greater than 8h, and the stability and fluidity of the filling slurry are good; compared with example 1, the bleeding rate and slump of comparative example 1 are small, the setting time of comparative example 1 and comparative example 4 is small, which is not conducive to pipeline transportation; the bleeding rate and setting time of comparative example 3 and comparative example 5 are large, the bleeding rate of comparative example 6 is large, and the stability of the filling slurry is poor. The slump of comparative example 6 is low, which cannot realize long distance pipeline transportation; it is shown that when the cement clinker accounts for 30-40% and the phosphorus slag powder accounts for 60-70% by mass percentage, or the cement clinker accounts for 15-50%, the phosphorus slag powder accounts for 30-80%, the slag powder accounts for 0-15% and the silica fume accounts for 0-10%, the filling slurry can meet the production requirements, and the filling material with raw materials exceeding the range will have different degrees of performance problems.

[0107] As can be seen from Table 5, the strengths of Examples 1-9 gradually increase with time and have good stability in later period; the strength of Comparative Example 8 first increases and then decreases, and obvious deterioration occurs at 180d. The 28d strength of Examples 1-9 is greater than 2.8MPa, the 90d strength is greater than 4MPa, and the 180d strength is higher than 5MPa, which are 1.57-2.5, 1.81-2.22 and 2.89-3.49 times of Comparative Example 8 respectively, thus it can be seen that the strength and stability of the filling material made of the raw materials of the application are obviously superior to those of the ordinary cement uranium tailings filling material. The 7d strength of Examples 1-7 is obviously higher than that of Examples 8-9, which shows that the addition of slag and silica fume can obviously improve the early strength of the filling slurry.

[0108] As can be seen from Table 5 and Table 7, compared with Example 1, the strength of each age period of Comparative Examples 1-3 decreases obviously, among which the strength of Comparative Example 3 decreases most obviously, the shrinkage and cracking of Comparative Example 2 is relatively obvious, and the cost of Comparative Example 1 is the highest. Compared with Example 1, the strength of each stage of Comparative Example 7 is lower, which shows that the addition and mixing sequence of the materials has a certain influence on the strength. Compared with Example 8, the 7d strength of Comparative Example 4 increases by 107%, the 28-180d strength decreases by 6.5-37.3%, and the cost is 1.54 times of Example 8; compared with Example 9, although the cost of Comparative Example 5 is the lowest, but its strength decreases by 34.4-47.5%; therefore, in view of the cost and the performance requirements of the filling slurry in actual production, the ratio of cement clinker and phosphorous slag powder in the cementitious material raw materials of the filling slurry of the application is relatively reasonable.

[0109] As can be seen from Table 6, the leaching rate, leaching fraction and mobile uranium content of uranium in Examples 1-9 are far lower than those of Comparative Example 8. Compared with Example 1, the leaching rate, leaching fraction and mobile uranium content of uranium in Comparative Example 7 increase by 2.67, 2.82 and 1.06 times respectively. Thus it can be seen that the uranium fixation and stabilization effect of the filling material obtained by the raw material ratio and preparation method provided by the application is superior to that of the filling material obtained by conventional raw materials and preparation method, and the leaching rate and migration risk of uranium are at a relatively low level.

[0110] As can be seen from Table 7, the solid waste content in the uranium tailings filling material of Examples 1-9 is higher than 96%, which is much higher than that of Comparative Example 8, and is beneficial to the reduction of bulk industrial solid waste and energy saving and carbon reduction while having excellent performance; the average cost of the raw materials of Examples 1-9 is 42.32 yuan / m 3 , which is obviously lower than that of Comparative Examples 1, 4 and 8, thus the uranium tailings filling material provided by the application has good economy.

[0111] In summary, the application provides a green low-carbon uranium tailings leaching filling material and a preparation method thereof, belonging to the technical field of mine filling and the technical field of low-radioactivity solid waste disposal. The filling material comprises uranium tailings, cementitious material, lime, slump retaining agent and water, wherein the cementitious material comprises cement clinker, phosphorous slag powder, slag powder and silica fume; and the raw materials are mixed through specific steps to maximize the synergistic effect between the raw materials, so that the fixation of nuclides and the strength of the filling material are both maximized. (1) The uranium tailings filling material prepared by the application has good fluidity, low bleeding rate and moderate setting time, and can meet the conveying requirements; the early strength of the filling body is adjustable and controllable, the middle and late strength is high, and the stability is good; the filling body has excellent fixation and control effect on nuclides; the comprehensive performance of the uranium tailings filling material is far superior to that of the cement uranium tailings filling material, and has good application prospect. (2) The filling material of the application fully utilizes the additive effect generated by the reaction of active solid waste and the advantages and disadvantages of components in uranium tailings, chemically fixes nuclides from the source by residual phosphoric acid in phosphorous slag, and consumes new Ca(OH)2 and gypsum in the hydration process by using active components in phosphorous slag powder, slag powder or silica fume, which can inhibit the reverse acid of uranium tailings, greatly improve the strength, late stability and nuclide leaching resistance of the filling body. (3) The total solid waste content in the uranium tailings filling material of the application is more than 96%, which can consume a large amount of industrial solid waste such as uranium tailings, effectively alleviate the pressure of tailings stacking and surface environmental pollution, and reduce the maintenance cost and decommissioning cost of uranium tailings. (4) The filling cementitious material provided by the application has large solid waste content, wide sources and low value, which can effectively improve the performance of the filling body, greatly reduce the filling cost, reduce CO2 emission, and is conducive to cost reduction and efficiency improvement of hard rock uranium mining and promotion of "double carbon" work.

[0112] It should be noted that the application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and embodiments having the same technical idea and playing the same role and effect within the scope of the technical solution of the application are all included in the technical scope of the application. In addition, within the scope of the main idea of the application, various modifications of the embodiments that can be thought of by those skilled in the art, and other ways constructed by combining part of the components of the embodiments are also included in the scope of the application.

Claims

1. A green low-carbonic acid leaching uranium tailings filling material, characterized in that: It includes uranium tailings, cementitious materials, lime, collapse-preventing agents and water; wherein, the cementitious materials, calculated by mass percentage, include: 30~40% cement clinker, 60~70% phosphorus slag powder; Alternatively, 15~50% cement clinker, 30~80% phosphorus slag powder, 0~15% slag powder and 0~10% silica fume.

2. The green low-carbonic acid leaching uranium tailings filling material according to claim 1, characterized in that: The uranium tailings are solid wastes after uranium is extracted using a sulfuric acid leaching agent in a surface heap leaching process or a stirring leaching process, with a pH value of 3.5 to 4.5 and a maximum particle size of ≤10 mm.

3. The green low-carbonic acid leaching uranium tailings filling material according to claim 1, characterized in that: The phosphorus slag powder is a powder ground from granulated electric furnace phosphorus slag, with a specific surface area of ​​≥300m 2 / kg, 28d activity index ≥85%, P2O5 content ≤5%, and radioactive indicators IRa and Ir are both ≤1.

4. The green low-carbonic acid leaching uranium tailings filling material according to claim 1, characterized in that: The slag powder is a powder ground from granulated blast furnace slag, with a specific surface area of ​​≥400m 2 / kg, 28d activity index ≥95%, SO3 content ≤4%, and radioactive indicators IRa and Ir are both ≤1.

5. The green low-carbonic acid leaching uranium tailings filling material according to claim 1, characterized in that: The silica fume is the powder collected in the flue during the smelting of ferrosilicon alloy, with a specific surface area of ​​≥15000m 2 / kg, activity index ≥105%, SiO2 content ≥85%.

6. The green low-carbonic acid leaching uranium tailings filling material according to claim 1, characterized in that: The specific surface area of ​​the cement clinker is 300~400m 2 / kg, the mass percentage of silicate minerals is greater than 66%.

7. The green low-carbonic acid leaching uranium tailings filling material according to claim 1, characterized in that: The lime is quicklime powder with a CaO content of ≥90%, and the added amount is 0.08-0.15% of the dry weight of the uranium tailings.

8. The green low-carbonic acid leaching uranium tailings filling material according to claim 1, characterized in that: The slump retaining agent includes: a high-efficiency water reducer and / or a high-performance water reducer; the high-efficiency water reducer includes one or more of aminosulfonate, naphthalene series, anthracene series, melamine resin, and ketone-aldehyde condensation product high-efficiency water reducers; the high-performance water reducer includes a polycarboxylic acid high-performance water reducer; and the addition amount of the slump retaining agent is 0.2-0.8% of the mass of the cementitious material.

9. The method for preparing the green low-carbonic acid leaching uranium tailings filling material according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. The uranium tailings, phosphorus slag powder and water are mixed and stirred thoroughly to obtain a mixed slurry; S2. Add cement clinker, slag, silica fume, lime, and collapse preventive agent to the mixed slurry in sequence and stir thoroughly to obtain uranium tailings filling material.

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