Harmless treatment method for rare earth smelting waste residues

Abstract

The invention discloses a harmless treatment method for rare earth smelting waste residues, and relates to the technical field of hazardous waste treatment and disposal. The method comprises the following steps: firstly, adding an organic barium salt into the rare earth smelting waste residue, stirring to react completely, then adding a carbonate mineralizing bacteria culture solution to carry out induced mineralization reaction, after the reaction is completed, pressurizing and compacting the rare earth smelting waste residue, carrying out carbonization maintenance, and drying after the maintenance is completed, so that the harmless treatment of the rare earth smelting waste residue is realized. The method for harmlessly treating the rare earth smelting waste residues has the advantages that the method is green and environment-friendly, the radioactivity of the rare earth smelting waste residues can be reduced in situ, the cementing effect on the rare earth smelting waste residues is good, and subsequent secondary utilization is not affected.

Description

Technical Field

[0001] The invention relates to the technical field of hazardous waste treatment and disposal, and in particular to a method for harmless treatment of rare earth smelting waste residue. Background Art

[0002] Rare earth minerals are polymetallic co-existing ores. In addition to iron, niobium and rare earths, they also contain a large amount of radioactive elements thorium and uranium. Due to the low industrial value of thorium and the low grade of uranium, most of the thorium and uranium introduced into the ore enter the waste slag, which will greatly increase the radioactivity of rare earth smelting waste slag compared with the radioactivity of the natural environment. If improperly disposed, it will not only pose a threat to the ecological environment and human health, but also lead to a waste of resources. Therefore, the development of a harmless disposal technology for rare earth smelting waste slag is of great significance to the long-term effective treatment and disposal of rare earth smelting waste slag and the sustainable development of the rare earth industry.

[0003] At present, solidification / stabilization treatment technology is the main technology for harmless disposal of hazardous waste, including cement solidification technology and asphalt solidification technology. However, cement solidification technology is prone to uneven mixing, premature or late solidification, and high leaching rate of pollutants during operation; asphalt solidification technology is prone to combustion when sealing waste containing oxidants. In addition, these technologies have the disadvantages of high cost, large volume increase, and difficulty in reusing the solidified rare earth tailings.

[0004] In recent years, microbial induced mineralization solidification of tailings / waste residues has attracted the attention of many scientific researchers. The use of microbial induced carbonate precipitation (MICP) technology to solidify rare earth smelting waste residues has the advantages of being environmentally friendly, low cost, and small footprint. It does not affect the future reuse of rare earth smelting waste residues and can reduce the waste of resources. There are many driving modes for the MICP process. One of them is to rely on the urease produced by microorganisms to decompose urea to form carbonate ions, which combine with exogenous calcium ions to form calcium carbonate precipitation. Another is to use carbonic anhydrase to catalyze carbon dioxide to form carbonate ions, and finally form calcium carbonate precipitation. The carbonate ions formed in the MICP process can also form carbonates with heavy metals and radionuclide ions, reducing the mobility and bioavailability of heavy metals and radionuclide ions. However, high concentrations of ammonium ions and ammonia may be produced as byproducts in the MICP process driven by urease, which may harm the environment and human health. High concentrations of ammonia can lead to eutrophication, hypoxia and damage to aquatic organisms; ammonia may also form heavy metal-ammonia complexes with heavy metals, thereby enhancing the mobility of heavy metal ions. When calcium chloride is used as a calcium source, the chloride ions introduced together with exogenous calcium ions may also further contaminate groundwater. In contrast, carbonic anhydrase bacteria can avoid the production of high concentrations of ammonium ions and ammonia, reducing the possibility of secondary pollution. In addition, although the traditional MICP process can cement rare earth smelting waste, it has limited effect in reducing the radiation dose of rare earth smelting waste. When using MICP technology to treat rare earth low-level waste, if carbonic anhydrase bacteria can be used, calcium sulfate in rare earth tailings can be used as a calcium source, and the use of urea and calcium chloride can be reduced, the possibility of secondary pollution will be effectively reduced and harmless treatment can be achieved. Summary of the invention

[0005] The purpose of the present invention is to provide a method for harmless treatment of rare earth smelting waste slag, so as to solve the problems existing in the above-mentioned prior art and realize the harmless treatment of rare earth smelting waste slag.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides a method for harmlessly treating rare earth smelting waste residue, comprising the following steps:

[0008] (1) adding organic barium salt to rare earth smelting waste slag and stirring for reaction;

[0009] (2) adding a carbonate mineralizing bacteria culture solution to the rare earth smelting waste residue treated in step (1) to induce a mineralization reaction;

[0010] (3) Pressurizing and compacting the rare earth smelting waste slag after the culture in step (2), carbonizing and curing, and drying after the curing is completed, so as to achieve harmless treatment of the rare earth smelting waste slag.

[0011] Furthermore, the reaction temperature of the induced mineralization reaction is 25 to 37° C., and the reaction time is 1 to 14 days;

[0012] Furthermore, the specific activity of the rare earth smelting waste slag is less than 4×10 11 Bq / kg.

[0013] Furthermore, the OD of the carbonate mineralizing bacteria culture solution is 600 It is 0.5~2.5.

[0014] Furthermore, the organic barium salt is barium acetate or barium lactate; the organic barium salt is added in the form of a solution in step (1), and the concentration of the organic barium salt solution is 0.01 to 0.5 mol / L.

[0015] Furthermore, the organic barium salt solution is added to the rare earth smelting waste slag according to a solid-liquid ratio of 1g:0.3-0.8mL.

[0016] Furthermore, the stirring reaction temperature in step (1) is 10 to 35° C., and the reaction time is 0.5 to 24 h.

[0017] In step (1), taking barium acetate as an example, the reaction equation is as follows: CaSO4+Ba(CH3COO)2→BaSO4+Ca(CH3COO)2. In step (2), after adding carbonate mineralizing bacteria and solidifying culture medium for cultivation, calcium acetate is converted into calcium carbonate, carbon dioxide and water. The reaction equation is as follows: Ca(CH3COO)2→CaCO3+CO2+H2O.

[0018] Furthermore, the rare earth smelting waste residue is solid waste generated after rare earth-containing minerals are subjected to wet smelting to extract rare earths, and contains a large amount of calcium sulfate and calcium sulfate dihydrate.

[0019] Furthermore, the carbonate mineralizing bacteria culture solution is a culture solution of one or more carbonate mineralizing strains, and the inoculation ratio is 1-3% (bacterial solution / culture medium).

[0020] The components of the culture medium used for the carbonate mineralizing bacteria culture solution are molasses 1-3 g / L, soy peptone 1-5 g / L, potassium dihydrogen phosphate 0.1-0.5 g / L and zinc sulfate 0.05-0.5 g / L. The initial pH of the culture medium is 6-9; the carbonate mineralizing bacteria culture solution is obtained by culturing for 24-48 hours.

[0021] Furthermore, the carbonate mineralization strain includes Bacillus mucilaginosus (CGMCC1.0910), Bacillus subtilis (ATCC 6633), Stenotrophomonas rhizophila (ACTT DSM14405T) or Rhodopseudomonas palustris (ATCC 17001).

[0022] Furthermore, the solidification culture medium comprises 1-3 g / L molasses, 1-5 g / L soy peptone, 0.1-0.5 g / L potassium dihydrogen phosphate and 0.05-0.5 g / L zinc sulfate.

[0023] Furthermore, the temperature of the carbonization curing is 20-35° C., the humidity of the carbonization curing is 70%±5%; the gas used in the carbonization curing is carbon dioxide or industrial waste gas containing carbon dioxide, the gas concentration is 20%-100%, and the gas pressure is 0-0.20 MPa.

[0024] The present invention first reconstructs the physical phase of rare earth smelting waste slag, adds barium acetate solution to the rare earth smelting waste slag, mixes evenly, and reacts for a certain period of time to convert calcium sulfate in the rare earth smelting waste slag into barium sulfate and calcium acetate, then adds carbonate mineralization bacteria agent and culture medium to the rare earth smelting waste slag, and decomposes calcium acetate into calcium carbonate through microbial induced mineralization. The generation of barium sulfate can effectively reduce the radiation dose, and the formation of calcium carbonate can cement the rare earth smelting waste slag together to prevent its wind erosion and diffusion and the migration and diffusion of polluting elements, thereby achieving the purpose of harmless disposal of rare earth smelting waste slag. The treatment method of the present invention has the characteristics of simple process and environmental friendliness.

[0025] The present invention discloses the following technical effects:

[0026] The present invention applies organic barium salt to microbial induced carbonate precipitation technology, so that the carbonate mineralizing bacteria induce the production of biological calcium carbonate while cementing the rare earth smelting waste together to form a whole, effectively reducing the risk of wind migration and diffusion of the rare earth smelting waste and leaching of polluting elements. In addition, barium sulfate is also generated in the reaction system and is doped in the rare earth smelting waste, which can effectively reduce the radiation dose of the rare earth smelting waste.

[0027] The method for harmlessly treating rare earth smelting waste slag of the present invention is green, environmentally friendly, can reduce the radioactivity of rare earth smelting waste slag in situ, has good cementing effect on rare earth smelting waste slag, and does not affect subsequent secondary utilization.

[0028] The barium salt used in the present invention is an organic acid barium, which reacts with rare earth smelting waste to form barium sulfate and organic acid calcium, and the carbonate mineralization bacteria can further convert the organic acid calcium into biological calcium carbonate to achieve the purpose of cementing the rare earth smelting waste. The present invention does not need to add a calcium source, and uses calcium sulfate, calcium sulfate dihydrate in the rare earth smelting waste and the organic acid calcium formed by conversion as the calcium source, which has low cost, small weight gain during the treatment process, and small volume increase.

[0029] The traditional urea decomposition-driven microbial mineralization process produces high concentrations of ammonium ions and ammonia as byproducts, which may harm the environment and human health. High concentrations of ammonia can lead to eutrophication, hypoxia and damage to aquatic organisms; ammonia may also form heavy metal-ammonia complexes with heavy metals, thereby enhancing the mobility of heavy metal ions. The present invention uses carbonate mineralizing bacteria to convert organic acid calcium into biological calcium carbonate without adding urea, which can avoid secondary pollution caused by ammonium ions and ammonia.

[0030] The traditional microbial induced calcium carbonate precipitation process generally uses calcium chloride as a calcium source. When the microorganisms use the calcium source to form biological calcium carbonate, the chloride ions introduced together with the exogenous calcium ions may migrate in the reaction system and even further pollute the groundwater. The present invention does not require the addition of a calcium source, and can also reduce the introduction of chloride ions during the treatment process, thereby reducing the environmental risk to groundwater caused by the migration of chloride ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the implementation examples of the present invention or the technical solutions in the prior art, the drawings required for use in the implementation examples will be briefly introduced below. Obviously, the drawings described below are only some implementation examples of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 It is a process flow chart of the present invention.

[0033] Figure 2 The XRD diagram of the rare earth smelting waste slag after treatment in the control group and implementation examples 1-4 of the present invention. DETAILED DESCRIPTION

[0034] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0035] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0036] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0037] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and implementation examples are merely exemplary.

[0038] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0039] By analyzing the composition of rare earth smelting waste residues, it was found that the rare earth smelting waste residues studied contained a large amount of calcium sulfate and calcium sulfate dihydrate, which have the possibility of being converted into calcium carbonate. By comparing the solubility products of different insoluble substances, it can be found that barium sulfate (1.1×10 -10 )<Calcium carbonate (3.36×10 -9 )<Barium carbonate (5.1×10 -9 )<Calcium sulfate (9.1×10 -6 ). According to the law of transformation of insoluble substances into more insoluble substances, when a soluble barium salt solution is added to rare earth smelting waste, calcium sulfate and calcium sulfate dihydrate will react with barium ions to form more insoluble barium sulfate and release some calcium ions. These calcium ions can be used as a calcium source in the subsequent MICP process to form calcium carbonate precipitation. Therefore, the MICP process can be adjusted by adding a barium salt solution to first form barium sulfate and organic acid calcium, which can achieve a repair effect while avoiding secondary pollution and truly achieve harmless treatment of rare earth smelting waste.

[0040] In the following examples and control groups of the present invention, the main components of rare earth smelting waste slag before treatment are: Ca, 12.143%; Fe, 9.994%; S, 8.061%; P, 0.849%; Ce, 0.81%; Ba, 0.644%; Pb, 0.506% and Th, 0.495%. Before the treatment of rare earth smelting waste slag, XRF results show that the main components are: CaO, 29.80%; SO3, 24.95%; P2O5, 18.47%; Fe2O3, 17.36%; CeO2, 1.04%; Nd2O3, 1.03%; others, 7.35%.

[0041] Control group

[0042] (1) Add deionized water to 100 g of rare earth smelting waste slag at a solid-liquid ratio of 1 g:0.3 mL, stir evenly at 25 °C for 30 min, and let stand for 1 h;

[0043] (2) Add 20 mL of deionized water to the rare earth smelting waste slag in step (1), stir thoroughly, and then incubate at room temperature for 7 days.

[0044] (3) After the incubation is completed, the rare earth smelting waste slag of step (2) is pressed and compacted, and then dried after pressurized carbonization curing to complete the treatment. The carbonization curing temperature is 30° C., the carbonization curing humidity is 70%, and the carbonization curing is performed using carbon dioxide gas, the gas concentration is 20%, and the gas pressure is 0.1 MPa.

[0045] The obtained samples were subjected to α and β activity tests, radon gas concentration tests, wind tunnel tests, unconfined compressive strength tests, and heavy metal and radionuclide leaching tests. The α and β activities were measured using an MR-50 radiation detector according to the operating manual. The radon gas evolution rate was measured using RAD7. The wind erosion loss was measured using an AF1300 wind tunnel tester, with the test wind speeds set to 6, 9, and 12 m / s. The unconfined compressive strength was measured using a universal compression machine. The sample leachate was prepared using the sulfuric acid-nitric acid method, and the content of heavy metal elements in the leachate was determined using a flame atomic absorption spectrophotometer, and the content of rare earth element Ce and radionuclides Th and U were determined using inductively coupled plasma atomic emission spectrometry.

[0046] The radiation dose of the control group before treatment was 0.535μsv / h, which was reduced to 0.412μsv / h after treatment, with a reduction of 0.123μsv / h. The single-side radon exhalation rate after treatment was 0.312Bq·m -2 ·s -1 The double-sided radon exhalation rate is 0.162 Bq·m -2 ·s -1; The leaching concentrations of Cu, Pb, Zn and Cd were 10.407, 60.613, 6.697 and 2.264 mg / kg respectively; the leaching concentrations of Th and U were 0.613 and 0.236 mg / kg respectively. After treatment, the unconfined compressive strength of the cemented body was 0.34 MPa, and the wind erosion loss at 6, 9 and 12 m / s was 0.3378, 0.9970 and 1.2750 g / min respectively. The content of Ce element was 0.81% before treatment and 0.81% after treatment.

[0047] Implementation Example 1

[0048] (1) Add 0.1 mol / L barium acetate solution to 100 g of rare earth smelting waste slag at a solid-liquid ratio of 1 g:0.3 mL, stir evenly at 30°C for 60 min, and let stand for 24 h to convert part of the calcium sulfate in the waste slag into barium sulfate and calcium acetate.

[0049] (2) Add 20 mL of OD 600 The carbonate mineralization bacteria culture solution is 1.0, and is fully stirred and cultured at room temperature for 7 days. The carbonate mineralization bacteria culture solution is obtained by inoculating 1% of Bacillus subtilis (CGMCC1.0910) and 1% of Bacillus subtilis (ATCC 6633) into a solidified medium and culturing for 24 hours. The solidified medium is composed of 3g / L molasses, 5g / L soy peptone, 0.5g / L potassium dihydrogen phosphate and 0.05g / L zinc sulfate.

[0050] (3) After the cultivation is completed, the rare earth smelting waste slag of step (2) is pressed and compacted, and then dried after pressurized carbonization curing to complete the harmless treatment. The carbonization curing temperature is 30° C., the carbonization curing humidity is 70%, and carbon dioxide gas is used for carbonization curing, the gas concentration is 30%, and the gas pressure is 0.1 MPa.

[0051] The detection method is the same as that of the control group. After the harmless treatment of implementation example 1, the radiation dose of the rare earth smelting waste slag is reduced from 0.535μsv / h to 0.292μsv / h, and the reduction range is 0.243μsv / h, which is 1.98 times the reduction range of the control group; the single-side radon gas precipitation rate of the rare earth smelting waste slag is reduced by 30.77% compared with the control group; the leaching rates of heavy metals Cu, Pb, Zn and Cd in the rare earth smelting waste slag are reduced by 36.85%, 66.74%, 44.38% and 62.15% respectively compared with the control group; the leaching rates of radioactive nuclides thorium and uranium in the rare earth smelting waste slag are reduced by 32.79% and 21.61% respectively compared with the control group. Therefore, after being treated by this method, the unconfined compressive strength can be significantly improved, and the radiation dose, wind erosion loss, and leaching concentrations of heavy metals and radioactive nuclides can be reduced.

[0052] The XRD test results of the treated samples are shown in Figure 2 The XRD results show that the rare earth smelting waste slag contains a large amount of calcium sulfate and calcium sulfate dihydrate before harmless treatment. After harmless treatment, a large number of diffraction peaks of barium sulfate and diffraction peaks of biological calcium carbonate (calcite, vaterite and aragonite) formed by carbonate mineralizing bacteria appear.

[0053] After treatment, the compressive strength of the cemented body of the rare earth smelting waste slag finally obtained in Example 1 is 1.47MPa, which is 4.32 times that of the control group; the wind erosion loss of the cemented body at 6m / s, 9m / s and 12m / s after treatment is 0.2688g / min, 0.5988g / min and 0.9626g / min, respectively, which is 20.43%, 39.93% and 24.50% lower than that of the control group. The content of Ce element before treatment is 0.81%, and the content after treatment is 0.81%. The rare earth element content before and after treatment is basically unchanged, indicating that this method does not affect the secondary utilization of rare earth smelting waste slag.

[0054] Implementation Example 2

[0055] (1) Add 0.2 mol / L barium acetate solution to 100 g of rare earth smelting waste slag at a solid-liquid ratio of 1 g:0.3 mL, stir evenly at 35 ° C for 60 min, and let stand for 24 h to convert part of the calcium sulfate in the waste slag into barium sulfate and calcium acetate.

[0056] (2) Add 20 mL of OD 600 The carbonate mineralization bacteria culture solution is 2.0, and is cultured at room temperature for 14 days after being fully stirred. The carbonate mineralization bacteria culture solution is obtained by inoculating 3% of Bacillus subtilis (CGMCC1.0910), 3% of Bacillus subtilis (ATCC 6633), 1% of rhizotrophic oligotrophic monospermum (ACTTDSM14405T) and 1% of Rhodopseudomonas palustris (ATCC 17001) into a solidified medium and culturing for 24 hours. The solidified medium is composed of 2.5g / L molasses, 4.5g / L soy peptone, 0.4g / L potassium dihydrogen phosphate and 0.03g / L zinc sulfate.

[0057] (3) After the cultivation is completed, the rare earth smelting waste slag of step (2) is pressed and compacted, and then dried after pressurized carbonization curing to complete the harmless treatment. The carbonization curing temperature is 35° C., the carbonization curing humidity is 75%, and the carbonization curing is performed using carbon dioxide gas, the gas concentration is 50%, and the gas pressure is 0.2 MPa.

[0058] The detection method is the same as that of the control group. After the harmless treatment of Example 2, the radiation dose of the rare earth smelting waste slag is reduced from 0.535μsv / h to 0.313μsv / h, with a reduction of 0.222μsv / h, which is 1.80 times the reduction of the control group; the single-side radon gas precipitation rate of the rare earth smelting waste slag is reduced by 28.53% compared with the control group; the leaching rates of heavy metals Cu, Pb, Zn and Cd in the rare earth smelting waste slag are reduced by 41.52%, 67.91%, 45.59% and 61.40% respectively compared with the control group; the leaching rates of radioactive nuclides thorium and uranium in the rare earth smelting waste slag are reduced by 54.00% and 30.93% respectively compared with the control group. Therefore, after being treated by this method, the unconfined compressive strength can be significantly improved, and the radiation dose, wind erosion loss, and leaching concentrations of heavy metals and radioactive nuclides can be reduced.

[0059] The XRD test results of the treated samples are shown in Figure 2 The XRD results showed that the spectrum was similar to that of Example 1, proving that barium sulfate was formed, as well as biological calcium carbonate formed under the action of carbonate mineralizing bacteria.

[0060] After treatment, the compressive strength of the solidified body of rare earth smelting waste slag is 1.49MPa, which is 4.38 times that of the control group; the wind erosion loss of the solidified body at 6m / s, 9m / s and 12m / s is 0.2636g / min, 0.5944g / min and 0.9394g / min respectively, which is 21.97%, 40.38% and 26.32% lower than that of the control group respectively. The content of Ce element is 0.81% before treatment and 0.80% after treatment. The rare earth element content before and after treatment is not much different, indicating that this method does not affect the secondary utilization of rare earth smelting waste slag.

[0061] Implementation Example 3

[0062] (1) Add 0.2 mol / L barium acetate solution to 100 g of rare earth smelting waste slag at a solid-liquid ratio of 1 g:0.5 mL, stir evenly at 30°C for 60 min, and let stand for 12 h to convert part of the calcium sulfate in the waste slag into barium sulfate and calcium acetate.

[0063] (2) Add 30 mL of carbonate mineralization bacteria agent and solidification medium to the rare earth smelting waste, stir thoroughly and culture at room temperature for 14 days. The carbonate mineralization bacteria culture solution is obtained by inoculating 2% of Bacillus subtilis (CGMCC1.0910) and 1% of Rhodopseudomonas palustris (ATCC 17001) in the solidification medium and culturing for 24 hours. The solidification medium is composed of 3 g / L molasses, 4.5 g / L soy peptone, 0.4 g / L potassium dihydrogen phosphate and 0.05 g / L zinc sulfate.

[0064] (3) After the cultivation is completed, the rare earth smelting waste slag of step (2) is compacted under pressure, and then dried after pressurized carbonization curing to complete harmless treatment. The carbonization curing temperature is 30° C., the carbonization curing humidity is 70%, and carbon dioxide gas is used for carbonization curing, the gas concentration is 25%, and the gas pressure is 0.15 MPa.

[0065] The detection method is the same as that of the control group. After the harmless treatment of Example 3, the radiation dose of the rare earth smelting waste slag was reduced from 0.535μsv / h to 0.279μsv / h, with a reduction of 0.256μsv / h, which is 2.08 times the reduction of the control group. The single-sided radon gas precipitation rate of the rare earth smelting waste slag was reduced by 37.82% compared with the control group. The leaching rates of heavy metals Cu, Pb, Zn and Cd were reduced by 38.34%, 67.85%, 46.81% and 68.86% respectively compared with the control group; the leaching rates of radioactive nuclides thorium and uranium were reduced by 61.66% and 47.03% respectively compared with the control group. Therefore, after treatment by this method, the unconfined compressive strength can be significantly improved, and the radiation dose, wind erosion loss, and leaching concentrations of heavy metals and radioactive nuclides can be reduced.

[0066] The XRD test results of the treated samples are shown in Figure 2 The XRD results showed that the spectrum was similar to that of Example 1, proving that barium sulfate was formed, as well as biological calcium carbonate formed under the action of carbonate mineralizing bacteria.

[0067] After treatment, the compressive strength of the solidified body of rare earth smelting waste slag is 1.68MPa, which is 4.94 times that of the control group; the wind erosion loss of the solidified body at 6m / s, 9m / s and 12m / s is 0.2162g / min, 0.5564g / min and 0.7832g / min respectively, which is 36.00%, 44.19% and 38.57% lower than that of the control group respectively. The content of Ce element is 0.81% before treatment and 0.79% after treatment. The rare earth element content before and after treatment is not much different, indicating that this method does not affect the secondary utilization of rare earth smelting waste slag.

[0068] Implementation Example 4

[0069] (1) Add 0.2 mol / L barium acetate solution to 100 g of rare earth smelting waste slag at a solid-liquid ratio of 1 g:0.8 mL, stir evenly at 35 ° C for 60 min, and let stand for 24 h to convert part of the calcium sulfate in the waste slag into barium sulfate and calcium acetate.

[0070] (2) Add 30 mL of carbonate mineralization bacteria agent and solidification medium to the rare earth smelting waste, stir thoroughly and culture at room temperature for 14 days. The carbonate mineralization bacteria culture solution is obtained by inoculating 3% of Bacillus subtilis (CGMCC1.0910) and 3% of Bacillus subtilis (ATCC 6633) in the solidification medium and culturing for 24 hours. The solidification medium is composed of 3 g / L molasses, 5 g / L soy peptone, 0.4 g / L potassium dihydrogen phosphate and 0.01 g / L zinc sulfate.

[0071] (3) After the cultivation is completed, the rare earth smelting waste slag of step (2) is compacted under pressure, and then dried after pressurized carbonization curing to complete harmless treatment. The carbonization curing temperature is 35° C., the carbonization curing humidity is 75%, and carbon dioxide gas is used for carbonization curing, the gas concentration is 20%, and the gas pressure is 0.10 MPa.

[0072] The detection method is the same as that of the control group. After the harmless treatment of Example 4, the radiation dose of the rare earth smelting waste slag was reduced from 0.535μsv / h to 0.292μsv / h, with a reduction of 0.243μsv / h, which is 1.98 times the reduction of the control group. The single-sided radon gas precipitation rate of the rare earth smelting waste slag was reduced by 19.55% compared with the control group. The leaching rates of heavy metals Cu, Pb, Zn and Cd were reduced by 41.65%, 68.98%, 44.44% and 56.76% respectively compared with the control group; the leaching rates of radioactive nuclides thorium and uranium were reduced by 60.85% and 57.20%. Therefore, after treatment by this method, the unconfined compressive strength can be significantly improved, and the radiation dose, wind erosion loss, and leaching concentrations of heavy metals and radioactive nuclides can be reduced.

[0073] The XRD test results of the treated samples are shown in Figure 2 The XRD results showed that the spectrum was similar to that of Example 1, proving that barium sulfate was formed, as well as biological calcium carbonate formed under the action of carbonate mineralizing bacteria.

[0074] After treatment, the compressive strength of the solidified body of rare earth smelting waste slag is 1.39MPa, which is 4.09 times that of the control group; the wind erosion loss of the cemented body at 6m / s, 9m / s and 12m / s is 0.1596g / min, 0.5606g / min and 0.6338g / min respectively, which is 52.75%, 43.77% and 50.29% lower than that of the control group. The content of Ce element is 0.81% before treatment and 0.80% after treatment. The rare earth element content before and after treatment is not much different, indicating that this method does not affect the secondary utilization of rare earth smelting waste slag.

[0075] The above results show that the original sample of rare earth smelting waste contains a large amount of calcium sulfate and calcium sulfate dihydrate. After being treated by the harmless treatment method of the present invention, the diffraction peak intensity of calcium sulfate and calcium sulfate dihydrate in Examples 1, 2, 3 and 4 is reduced, and diffraction of barium sulfate and biological calcium carbonate (calcite, vaterite and aragonite) appears. This shows that after being treated by the method of the present invention, barium sulfate and biological calcium carbonate are generated in the reaction system, which can cement the rare earth smelting waste particles together, and while reducing the radiation dose, it can prevent the rare earth smelting waste particles from being blown away by the wind to cause air pollution, and reduce the leaching content of heavy metal elements and radionuclides.

[0076] Table 1 Radiation dose of rare earth smelting waste slag before and after treatment in each group

[0077]

[0078]

[0079] Table 2 Radon release rate of rare earth smelting waste slag before and after treatment

[0080]

[0081] Table 3 Contents of heavy metal elements and radionuclides in the sulfuric acid-nitric acid leaching solution before and after treatment of rare earth smelting waste slag

[0082]

[0083] Table 4 Unconfined compressive strength and wind erosion loss of cemented bodies before and after treatment in each group

[0084]

[0085] Table 5 Ce element content of each group before and after treatment

[0086]

[0087]

[0088] The harmless treatment method for rare earth waste slag provided by the present invention relieves the storage pressure of the waste slag warehouse and reduces the impact on the surrounding environment.

[0089] The implementation examples described above are only descriptions of the preferred methods of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for harmlessly treating rare earth smelting waste residue, characterized in that: The following steps are involved: (1) adding organic barium salt to rare earth smelting waste slag and stirring for reaction; (2) adding a carbonate mineralizing bacteria culture solution to the rare earth smelting waste residue treated in step (1) to induce a mineralization reaction; (3) Pressurizing and carbonizing the rare earth smelting waste slag after the culture in step (2), and drying it after the curing is completed to achieve harmless treatment of the rare earth smelting waste slag.

2. The method according to claim 1, characterized in that The organic barium salt is barium acetate or barium lactate; in step (1), the organic barium salt is added in the form of a solution, and the concentration of the organic barium salt solution is 0.01-0.5 mol / L.

3. The method according to claim 2, characterized in that The organic barium salt solution is added to the rare earth smelting waste slag according to a solid-liquid ratio of 1 g: 0.3-0.8 mL.

4. The method according to claim 2, characterized in that: The stirring reaction temperature in step (1) is 10-35° C., and the reaction time is 0.5-24 h.

5. The method according to claim 1, characterized in that The rare earth smelting waste residue is a hazardous solid waste generated after rare earth-containing minerals are subjected to wet smelting to extract rare earths.

6. The method according to claim 1, characterized in that The carbonate mineralizing bacteria culture solution is the culture solution of one or more carbonate mineralizing bacteria strains.

7. The method according to claim 6, characterized in that The carbonate mineralizing strains include Bacillus mucilaginosus, Bacillus subtilis, Stenotrophomonas rhizophila or Rhodopseudomonas palustris.

8. The method according to claim 6, characterized in that The components of the culture medium used for the carbonate mineralizing bacteria culture solution are 1-3 g / L molasses, 1-5 g / L soy peptone, 0.1-0.5 g / L potassium dihydrogen phosphate and 0.05-0.5 g / L zinc sulfate.

9. The method according to claim 1, characterized in that: The temperature of the carbonization curing is 20-35° C., the humidity of the carbonization curing is 70%±5%; and the gas atmosphere of the carbonization curing is a carbon dioxide atmosphere.

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