A method for treating thallium-containing, uranium-containing and manganese-containing mine uranium tailing pond seepage water by real-time synthesis of hydrotalcite-like compounds

Abstract

The present application belongs to the technical field of water pollution remediation, and particularly relates to a method for treating mine uranium tailing pond seepage water containing thallium, uranium and manganese by using real-time synthesized hydrotalcite-like compounds. The method comprises: adding industrial solid waste into the seepage water and mixing uniformly, and then adding an alkali source and mixing uniformly; the industrial solid waste contains 10wt%-100wt% of slag powder and 0-90wt% of fly ash; the alkali source is selected from at least one of alkali metal hydroxides, oxides and basic salts; and the method does not use a flocculant. Compared with the prior art, the present application realizes the transformation of waste into treasure by using raw materials and process innovation, has low cost, and has high treatment efficiency.

Description

Technical Field

[0001] This invention belongs to the field of water pollution remediation technology, specifically relating to a method for real-time synthetic hydrotalcite treatment of seepage water from thallium-, uranium-, and manganese-containing mine tailings ponds. Background Technology

[0002] During the hydrometallurgical process of uranium mining, a large amount of waste rock and tailings are exposed to the natural environment. After stabilization treatment through source control methods such as covering, surface hardening, or covering with soil and vegetation, the amount of wastewater containing radioactive nuclides and heavy metals exceeding the standards caused by rainfall or groundwater infiltration can be greatly reduced. However, due to factors such as weathering of the cover layer and vegetation disturbance, the amount of seepage from most tailings ponds and waste rock sites increases year by year. At the same time, uranium tailings and waste rock often contain sulfide minerals such as pyrite and marcasite, producing acidic wastewater with a pH < 6. If left untreated, this wastewater will flow into the environment without organization, causing pollution of soil, water bodies, and vegetation, and damaging the watershed ecology. When source control cannot completely stop the seepage of wastewater exceeding the standards, it is essential to provide an effective end-of-pipe treatment method.

[0003] Currently, methods for treating seepage water from uranium mine tailings ponds include physical, chemical, biological, and combined methods. The excessive elements are mostly heavy metals such as zinc, manganese, copper, arsenic, chromium, and cadmium, as well as radioactive nuclides. There are no cases involving the removal of thallium, uranium, or manganese-containing wastewater. Thallium is extremely toxic in water, classified as a highly poisonous substance, even more toxic than heavy metals such as lead and mercury. Its danger stems from its high solubility, insidious nature, and biomimicry, making it a highly efficient metabolic poison. Current domestic and international methods for treating thallium-containing wastewater include sulfide precipitation, adsorption, ion exchange, biological agents, and electrochemical methods. Sulfide precipitation is suitable for treating high-concentration thallium solutions, using a two-stage precipitation process with lime and sodium sulfide, followed by acid adjustment to restore pH, reducing the effluent concentration to 5 μg / L. Adsorption methods, including oxidative adsorption, activated carbon adsorption, and bioadsorption, require additional additions of oxidants, flocculants, and biological nutrients, and suffer from low treatment efficiency, large slag production, and complex processes. Biological agents can deeply remove thallium, but require high control of process parameters and exhibit unstable results. Currently, the application of hydrotalcite-like materials in wastewater treatment, especially in the adsorption / fixation of heavy metals, has been studied. However, there are no reports of "real-time synthesis" of hydrotalcite-like materials and their direct application to the treatment of highly challenging mine wastewater, particularly complex systems containing thallium, uranium, and manganese. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of excessive levels of thallium, radioactive nuclides uranium, and manganese in the seepage water of decommissioned uranium mine tailings ponds, which are difficult to remove, as well as the problems of long process flow, high reagent cost, and low wastewater treatment efficiency in existing processes. It also aims to solve at least one of the following problems: existing technologies lack a combined treatment technology for thallium, uranium, and manganese; traditional hydrotalcite-like treatment requires pre-synthesis and addition, resulting in long process flow and high cost; existing technologies have poor treatment effect on radioactive nuclides and low-concentration, difficult-to-remove ions (such as thallium), which can easily cause secondary release.

[0005] Therefore, this invention provides a method for real-time synthetic hydrotalcite-like material treatment of seepage water from thallium-, uranium-, and manganese-containing mine tailings ponds. This method is applicable to the treatment of seepage water from specific mine tailings ponds and can replace existing long-process methods. The method includes:

[0006] Add industrial solid waste to the leachate and mix thoroughly, then add an alkali source and mix thoroughly.

[0007] The industrial solid waste contains 10wt%-100wt% slag powder and 0-90wt% fly ash.

[0008] The alkaline source is selected from at least one of alkali metal hydroxides, oxides, and basic salts. It can be an alkaline substance that is alkaline in solution and can release hydroxide ions, carbonate ions, and valuable cations.

[0009] The method does not use flocculants.

[0010] The above-described method for treating seepage water from uranium tailings ponds containing thallium, uranium, and manganese in real-time synthetic hydrotalcite involves wastewater with a pH of 3-6 that meets at least one of the following characteristics: Mn ion concentration > 2 mg / L; U ion concentration > 0.3 mg / L; Ti ion concentration > 2 μg / L. Generally, the concentrations of thallium, uranium, and manganese ions in the seepage water exceed the limits specified in the wastewater discharge standard GB23727.

[0011] This invention utilizes the free alkaline substances contained in slag powder and fly ash to moderately neutralize the leachate, reducing the amount of alkali source required. The dissolved ions supplement and adjust the ratio of divalent and trivalent cations in the leachate to facilitate the formation of a layered structure similar to hydrotalcite (some excessive elements enter the layer and are removed). The addition of the alkali source provides interlayer anions, forming a stable solid precipitate and preventing the secondary release of harmful elements. The micron-sized silicate and carbonate particles in slag powder and fly ash are large and dense, increasing the overall density of the flocs and acting as a "ballast." By adjusting the ratio and type of slag powder and fly ash to optimize particle size distribution, coarse particles are "gravity-driven" for rapid initial separation, while fine particles "fill the pores" for deep dehydration. At the same time, the glassy network structure of silica significantly accelerates the precipitation efficiency of hydrotalcite through adsorption bridging or net sweeping. By precisely blending slag powder, fly ash, and alkali source and accurately controlling conditions, a low-cost, simple process technology with high pollutant removal efficiency has been developed for the treatment of leachate from tailings ponds in specific uranium mines. This technology ensures that the thallium, uranium, and manganese in the leachate meet the GB23727-2020 Integrated Wastewater Discharge Standard.

[0012] As a preferred embodiment, in the above-mentioned method for treating seepage water from thallium-, uranium-, and manganese-containing uranium tailings ponds using real-time synthetic hydrotalcite, the alkali source is selected from at least one of quicklime, hydrated lime, sodium hydroxide, magnesium hydroxide, and sodium carbonate, more preferably from at least one of inexpensive quicklime and hydrated lime, and most preferably from hydrated lime.

[0013] As a preferred embodiment, in the above-mentioned method for treating seepage water from thallium-, uranium-, and manganese-containing uranium tailings ponds using real-time synthetic hydrotalcite, the industrial solid waste contains 20wt%-90wt% slag powder and 10-80wt% fly ash. More preferably, the slag powder is 50wt%-80wt% and the fly ash is 20-50wt%.

[0014] As a preferred embodiment, the above-mentioned method for treating leachate from thallium-, uranium-, and manganese-containing mine tailings ponds using real-time synthetic hydrotalcite involves adding industrial solid waste at a concentration of 20-80 g / L relative to the leachate, and adding an alkali source at a concentration of 0.04-10 g / L relative to the leachate. More preferably, the addition of industrial solid waste is 30-60 g / L relative to the leachate, and the addition of an alkali source is 0.06-5 g / L relative to the leachate. Most preferably, the addition of industrial solid waste is 30-50 g / L relative to the leachate, and the addition of an alkali source is 0.06-1 g / L relative to the leachate.

[0015] As a preferred embodiment, the above-mentioned method for treating leachate from thallium-, uranium-, and manganese-containing uranium tailings ponds using real-time synthetic hydrotalcite has a mixing time of 2-60 min for industrial solid waste and leachate, more preferably 2-30 min, and most preferably 5-10 min.

[0016] As a preferred embodiment, the above-mentioned method for treating seepage water from thallium-, uranium-, and manganese-containing uranium tailings ponds using real-time synthetic hydrotalcite has a mixing time of 5-120 min for the alkali source and the seepage water, more preferably 5-60 min, and most preferably 20-30 min.

[0017] As a preferred option, the above-mentioned method for treating seepage water from thallium-, uranium-, and manganese-containing uranium tailings ponds using real-time synthetic hydrotalcite includes, after adding an alkali source and mixing evenly, solid-liquid separation, resulting in treated tailings water that is below discharge standards.

[0018] As a preferred embodiment, the above-mentioned method for treating seepage water from thallium-, uranium-, and manganese-containing uranium tailings ponds using real-time synthetic hydrotalcite has a mixing rate of 100-300 r / min.

[0019] As a preferred embodiment, in the above-mentioned method for treating seepage water from thallium-, uranium-, and manganese-containing uranium tailings ponds using real-time synthetic hydrotalcite, when the alkali source is a sparingly soluble or insoluble alkali source, the solid material is slurried before use. The slurry concentration can be 10-100 g / L, preferably 15-60 g / L, and more preferably 20-40 g / L, and is added to the seepage water in a homogeneous and quantitative manner.

[0020] The advantages of this invention compared to the prior art are mainly reflected in the following aspects:

[0021] 1. Raw material and process innovation to turn waste into treasure:

[0022] Traditional technologies require the preparation of hydrotalcite before it can be used to treat wastewater. This invention, however, directly uses pollutants from the wastewater as raw materials. It utilizes divalent and trivalent cations dissolved from industrial solid waste (such as fly ash and slag powder) to supplement and adjust the ion ratio, and neutralizes acidity and provides an alkaline environment through an alkali source. This allows the pollutants to be directly "locked" into the layered structure of the hydrotalcite, eliminating the need for pre-preparation steps and simplifying the process. Simultaneously, the ratio of alkali source to industrial solid waste and key process parameters can be precisely controlled according to the composition of the leachate pollutants, significantly reducing treatment costs and providing a highly efficient technological upgrade solution for treating excessive leachate from mining enterprises.

[0023] 2. Low cost:

[0024] The main raw materials used are industrial solid wastes such as fly ash and slag powder, which are widely available, readily available in the market, and inexpensive, thus significantly reducing material costs.

[0025] 3. High processing efficiency:

[0026] Compared with existing leachate treatment processes, no flocculant needs to be added; by combining fly ash (40-50% of Class III >45μm particle size) and slag powder (S105 average particle size 10-20μm) to optimize particle size distribution, the settling time is significantly shortened, all excessive cations (including radioactive nuclides) in leachate can be removed simultaneously, and the TDS of the solution can be effectively reduced, resulting in a significant improvement in overall treatment efficiency.

[0027] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Detailed Implementation

[0028] The following description provides numerous specific details to offer a more thorough understanding of the technical solutions provided by this invention. However, it will be apparent to those skilled in the art that the technical solutions provided by this invention can be implemented without one or more of these details.

[0029] In this embodiment of the invention, the sources of each raw material are: inexpensive and readily available reagents and industrial solid waste materials, wherein: calcium hydroxide is analytical grade; slag powder: S105; fly ash: Grade III.

[0030] In the embodiments and comparative examples of this invention, the seepage water is sample 0#.

[0031] Example 1

[0032] This embodiment provides a technical method for treating tailings dam seepage water. Industrial solid waste (slag powder S105: fly ash grade III = 1:1) is added to the water sample in a certain ratio and mixed thoroughly for a certain period of time. A pre-prepared alkali source suspension (calcium hydroxide) is added, and after thorough stirring and reaction, solid-liquid separation is performed. The contents of uranium, manganese, and thallium in the clear liquid are analyzed, and the pH value of the solution is measured.

[0033] Test case

[0034] S1. Experimental Preparation: Accurately measure 100 mL of a real water sample from the tailings dam of a uranium mine and pour it into a 250 mL beaker for later use. This sample is designated as #1 (sample #1 will undergo dynamic changes during the later stages of treatment and does not represent the untreated state). #0 represents the untreated real water sample from the tailings dam of the aforementioned uranium mine. All water samples were analyzed by the Analysis and Testing Center of the Beijing Research Institute of Chemical Metallurgy of Nuclear Industry (hereinafter referred to as the Analysis Center). The detection standards for uranium, manganese, and thallium were HJ700-2014, and the concentrations of key ions are shown in Table 1.

[0035] S2. Accurately weigh 2 g of calcium hydroxide and place it in a 200 mL beaker. Pour in 100 mL of deionized water and stir electromagnetically for more than 10 min at a stirring rate of 260 r / min to maintain the suspension state, thereby obtaining a calcium hydroxide suspension with a concentration of 20 g / L.

[0036] S3. Accurately weigh 1.5 g of S105 slag powder and 1.5 g of Class III fly ash, mix them evenly and set aside.

[0037] S4. Static test: Add S3 solid powder to water sample 1, start electromagnetic stirring at a stirring rate of 260 r / min, stir evenly for 5-10 min, accurately measure 0.3 mL of calcium hydroxide suspension prepared in S2, slowly add it dropwise to water sample 1, control the dropwise addition time to about 1 min, start timing after mixing evenly;

[0038] S5. Sampling and analysis: After 30 minutes of full contact reaction, solid-liquid separation is performed. The supernatant is sent to the analysis center to determine the concentrations of uranium, manganese, and thallium, as well as the pH value. Specific data are shown in Table 2.

[0039] Table 1. Key ion concentrations in seepage water from a tailings dam of a uranium mine.

[0040]

[0041] Table 2. Effect of composite material dosage ratio on the concentration of key ions in leachate.

[0042]

[0043] As can be seen from the data in Table 2, the addition combination in Example 1 can effectively remove uranium, manganese and thallium, with removal rates of 91%, 98.3% and 69% respectively, all of which are below the emission limits of GB23727.

[0044] Example 2

[0045] This embodiment provides a technical method for treating tailings pond seepage water. Industrial solid waste (single slag powder S105) is added to the water sample in a certain proportion and mixed thoroughly for a certain period of time. A pre-prepared alkaline source suspension (calcium hydroxide) is added and stirred thoroughly with the water sample and industrial solid waste. After solid-liquid separation, the contents of uranium, manganese and thallium in the clear liquid are analyzed, and the pH value of the solution is determined.

[0046] Test case

[0047] S1. Same as Example 1, the water sample after treatment / treatment is numbered 2#;

[0048] S2, Same as Example 1;

[0049] S3. Accurately weigh 3g of S105 slag powder for later use;

[0050] S4. Static test: Add S3 solid powder to water sample #2, start electromagnetic stirring at a stirring rate of 260 r / min, stir evenly for 5-10 min, accurately measure 0.3 mL of the calcium hydroxide suspension prepared in S2, and slowly add it dropwise to water sample #2, controlling the dropwise addition time to about 1 min, and start timing after mixing evenly.

[0051] S5. Same as Example 1, specific data are shown in Table 3;

[0052] Table 3. Effect of composite material dosage ratio on the concentration of key ions in leachate.

[0053]

[0054] As can be seen from the data in Table 3, the single mineral powder in Example 2 can effectively remove uranium, manganese and thallium as industrial solid waste, with removal rates of 85.4%, 91.6% and 67.3% respectively, all of which are below the emission limits of GB23727.

[0055] Example 3

[0056] As a non-preferred embodiment, the wastewater treatment effect is compared with that in Example 1 under different conditions of industrial solid waste and alkali source dosage.

[0057] Test case

[0058] S1, Same as Example 1, water sample number 3#;

[0059] S2, Same as Example 1;

[0060] S3. Accurately weigh 1g of S105 slag powder and 1g of Class III fly ash, mix them evenly and set aside.

[0061] S4. Static test: Add S3 solid powder to water sample #3, start electromagnetic stirring at a stirring rate of 260 r / min, stir evenly for 5-10 min, accurately measure 0.3 mL of calcium hydroxide suspension prepared in S2, slowly add it dropwise to water sample #3, control the dropwise time to about 1 min, and start timing after mixing evenly.

[0062] S5. Same as Example 1, specific data are shown in Table 4;

[0063] Table 4. Effect of composite material dosage ratio on the concentration of key ions in leachate.

[0064]

[0065] The data in Tables 1-4 show that the higher the amount of industrial solid waste and calcium hydroxide added, the higher the removal rate of ions exceeding the standard, and the higher the reagent cost. Compared with Example 1, when the amount of industrial solid waste added was reduced from 30 g / L to 20 g / L, the removal rates of uranium, manganese, and thallium were 81.4%, 95.9%, and 57.8%, respectively, which still met the emission standards of GB23727, but the removal rates all decreased, and the thallium concentration after treatment was close to the standard value.

[0066] Comparative Example 1

[0067] The effect of different contact reaction times on the treatment effect when using calcium hydroxide alone to treat leachate was investigated.

[0068] Ca(OH)2 can effectively raise the pH value of a solution and is inexpensive and readily available. It is slightly soluble in aqueous solution, with a solubility of 1.65 g / L (20℃). A 20 g / L suspension of Ca(OH)2 was prepared, and 1 mL was added dropwise to 200 mL of wastewater with stirring (equivalent to a Ca(OH)2 concentration of 0.1 g / L). The electromagnetic stirring speed was 260 r / min. The pH value of the solution and the concentrations of Ti, U, and Mn in the treated solution were investigated at different reaction times. The specific data are shown in Table 5.

[0069] Table 5. Treatment of leachate with Ca(OH)2 suspension at different contact reaction times

[0070]

[0071] The data in the table show that when the 20 g / L suspension prepared by Ca(OH)2 is used to treat the excessive components in the wastewater, the concentrations of TI, U, and Mn in the solution first decrease and then increase with the extension of the contact reaction time. The concentrations are lowest at 30 min, and U and Mn can be discharged in compliance with standards. The decrease in TI concentration is not significant. This indicates that even if the concentration of the alkali source Ca(OH)2 is increased, the removal effect of Ca(OH)2 alone on thallium is still not good.

[0072] When alkali is added to the leachate, the pH level rises, causing metal hydroxide precipitates. As the pH continues to rise, the amphoteric nature of uranium causes the precipitate to redissolve, forming soluble complex ions. This leads to a re-increase in the concentration of heavy metal ions that had already been removed. Manganese, under the action of alkali, first forms manganese hydroxide precipitate, reducing its concentration, and then undergoes oxidation to form stable manganese dioxide. Under excessively high pH conditions, the kinetics of some oxidation reactions slow down, or the morphology of the precipitate changes, preventing some manganese from being effectively converted into stable high-valence precipitates. In contrast to the mechanism of removing excessive ions through the synergistic effect of industrial solid waste to form hydrotalcite-like substances, this method directly "locks" pollutants into the layered structure of the material, preventing their release and avoiding the phenomenon of initial decrease followed by increase.

[0073] Comparative Example 2

[0074] The effect of different solid-liquid mass-volume ratios on the treatment effect when using a single type of slag powder to treat leachate was investigated.

[0075] Accurately weigh 0.5 g, 1 g, 2 g, 3 g, and 5 g of slag powder and add them to 100 mL of raw water respectively. The solid-liquid mass-volume ratios are 5 g / L, 10 g / L, 20 g / L, 30 g / L, and 50 g / L, respectively. The electromagnetic stirring speed is 260 r / min, and the contact reaction time is 30 min. The pH value of the solution and the concentrations of U, Mn, and TI in the treated solution are investigated. The specific data are shown in Table 6.

[0076] Table 6 Treatment of slag powder with different solid-liquid ratios

[0077]

[0078] The data in the table show that when using single slag powder to treat leachate, a solid-liquid mass-volume ratio of 30 g / L can only bring the thallium concentration to the emission standard, while 50 g / L is needed to reduce the concentrations of Ti, U, and Mn to below the requirements of the GB23727 emission standard, resulting in an increase in solid waste.

[0079] To address the characteristics of excessive tailings effluent from specific uranium mines, water treatment experiments were conducted using single or combined reagents. The provided examples and comparative data show that when using industrial solid waste (slag powder / fly ash) alone to treat uranium-containing tailings effluent, a solid-liquid mass-to-volume ratio of ≥50 g / L is required to reduce the concentrations of Ti, U, and Mn to below the GB23727 emission standard. A single alkali source (Ca(OH)2) cannot effectively remove thallium from the excessive wastewater. In Example 1, using a combination of industrial solid waste and alkali source to treat the effluent (30 g / L solid waste combined with 0.06 g / L Ca(OH)2) effectively achieved the desired treatment of the excessive components. In Example 3, although the concentrations of all ions met the standards, the thallium concentration was close to the standard value. Considering reagent cost, slag production, and the safety threshold of harmful ions after treatment, the dosing schemes in Examples 1 and 2 are superior.

[0080] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for treating seepage water from uranium tailings ponds in thallium-, uranium-, and manganese-containing mines using real-time synthetic hydrotalcite, characterized in that... The method includes: Add industrial solid waste to the leachate and mix thoroughly, then add an alkali source and mix thoroughly. The industrial solid waste contains 20wt%-90wt% slag powder and 10-80wt% fly ash. The alkali source is selected from at least one of alkali metal hydroxides, oxides, and basic salts; The method does not use flocculants; The pH value of the effluent is 3-6, and the concentration of Mn ions is >2 mg / L; the concentration of U ions is >0.3 mg / L; and the concentration of Tl ions is >2 μg / L. Compared to leachate, the dosage of industrial solid waste is 20-80 g / L; The dosage of alkali source is 0.04-10 g / L relative to the leachate.

2. The method for treating seepage water from uranium tailings ponds in thallium-, uranium-, and manganese-containing mines using real-time synthetic hydrotalcite as described in claim 1, characterized in that... The alkali source is selected from at least one of quicklime, hydrated lime, sodium hydroxide, magnesium hydroxide, and sodium carbonate.

3. The method for treating seepage water from thallium-, uranium-, and manganese-containing mine tailings ponds using real-time synthetic hydrotalcite as described in claim 2, characterized in that... Satisfy at least one of the following characteristics: The alkali source is selected from at least one of quicklime and hydrated lime; The industrial solid waste contains 50wt%-80wt% slag powder and 20-50wt% fly ash.

4. The method for treating seepage water from uranium tailings ponds in thallium-, uranium-, and manganese-containing mines using real-time synthetic hydrotalcite as described in claim 3, characterized in that... The alkali source is slaked lime.

5. The method for treating seepage water from uranium tailings ponds in thallium-, uranium-, and manganese-containing mines using real-time synthetic hydrotalcite as described in claim 1, characterized in that: The mixing time between industrial solid waste and leachate is 2-60 minutes; The mixing time between the alkali source and the leachate is 5-120 minutes.

6. The method for treating seepage water from thallium-, uranium-, and manganese-containing mine tailings ponds using real-time synthetic hydrotalcite as described in claim 5, characterized in that: The dosage of industrial solid waste is 30-60 g / L, relative to leachate. The dosage of the alkali source is 0.06-5 g / L relative to the leachate; The mixing time between industrial solid waste and leachate is 2-30 minutes; The mixing time between the alkali source and the leachate is 5-60 minutes.

7. The method for treating seepage water from uranium tailings ponds in thallium-, uranium-, and manganese-containing mines using real-time synthetic hydrotalcite as described in claim 6, characterized in that: Compared to leachate, the dosage of industrial solid waste is 30-50 g / L; The dosage of the alkali source is 0.06-1 g / L relative to the leachate; The mixing time between industrial solid waste and leachate is 5-10 minutes; The mixing time between the alkali source and the leachate is 20-30 minutes.

8. The method for treating seepage water from uranium tailings ponds in thallium-, uranium-, and manganese-containing mines using real-time synthetic hydrotalcite as described in claim 1, characterized in that, After adding the alkali source and mixing evenly, the process also includes solid-liquid separation.

9. The method for treating seepage water from uranium tailings ponds in thallium-, uranium-, and manganese-containing mines using real-time synthetic hydrotalcite as described in claim 1, characterized in that... Satisfy at least one of the following characteristics: The mixing rate is 100-300 r / min; When the alkali source is a sparingly soluble or insoluble alkali source, the solid material is pulped before use.

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