Synchronous treatment method for ammonia nitrogen residues and exchangeable rare earth in rare earth tailing soil
By combining psychrophilic Pseudomonas aeruginosa with extracellular polymers, the problem of simultaneous treatment of ammonia nitrogen residue and exchangeable rare earth elements in rare earth tailings soil was solved, achieving efficient, low-cost, and environmentally friendly remediation results, and significantly improving soil stability and ecological restoration efficiency.
Patent Information
- Application Number
- CN202511562595.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-29
- Publication Date
- 2026-01-23
AI Technical Summary
Existing technologies are unable to simultaneously and efficiently remove residual ammonia nitrogen and exchangeable rare earth elements from rare earth tailings soil, resulting in high environmental pollution risks and high remediation costs, making it difficult to meet the needs for rapid, low-cost, and environmentally friendly solutions.
By using psychrophilic Pseudomonas and its extracellular polymers, ammonia nitrogen is converted into nitrate nitrogen through biological nitrification, and stable complexes are formed with rare earth elements, thereby achieving the removal of ammonia nitrogen and the fixation of rare earth elements. The modular culture and the characteristics of extracellular polymers avoid chemical reagent residues and secondary environmental risks.
Within 84 days, the ammonia nitrogen removal rate reaches 99%, the exchangeable rare earth element fixation rate is ≥40%, the soil ecological restoration efficiency is improved, energy consumption and reagent usage are reduced, the soil organic matter content is increased, and the soil water and fertilizer retention capacity is enhanced.
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Abstract
Description
TECHNICAL FIELD
[0001] The application relates to a method for simultaneously treating residual ammonia nitrogen and exchangeable rare earth in rare earth tailing soil, and belongs to the technical field of mine soil remediation. BACKGROUND
[0002] The ion-type rare earth ore is usually mined by using an in-situ leaching process, ion exchange between an ion leaching agent (such as ammonium sulfate) and rare earth elements in the ore body is used to realize effective extraction of the rare earth elements; however, after a large amount of the leaching agent such as ammonium sulfate is used, high-concentration ammonia nitrogen is left in the rare earth tailing soil, which can easily cause a series of ecological problems such as soil acidification, activity and fertility reduction of soil microorganisms and ammonia nitrogen eutrophication of surrounding water bodies; at the same time, in the process of extracting the rare earth elements, NH4 + is ion-exchanged and thus replaced, so a large amount of the rare earth elements in the form of exchangeable state exists in the rare earth tailing soil; the exchangeable rare earth has strong migration and bioavailability: they are adsorbed on the surface of soil colloids such as clay minerals and organic matter through electrostatic action, are easily exchanged with other cations (such as H + , Ca 2+ , NH4 + , etc.) in the soil solution and enter the liquid phase, are then leached and diffused with rainwater or are absorbed by plants, are a form with high environmental risk and can easily cause widespread soil and water pollution. Therefore, the treatment of the rare earth tailing soil faces the problems of multiple levels and multiple dimensions.
[0003] At present, the treatment of the ion-adsorbed rare earth tailing soil mainly depends on two ways of physical and chemical leaching and plant hyperaccumulation. The physical and chemical leaching can strip part of the ammonia nitrogen (NH4 + -N), but the actual removal efficiency is only 40% to 60%, a large amount of chemical reagents (the common amount is about 10 kg / m³) needs to be invested, the remediation cost is as high as, and the soil aggregate structure is damaged in the leaching process, causing secondary chemical residues; the plant remediation needs to rely on hyperaccumulation species such as vetiver and sunflower, and it usually takes 1 to 2 years to complete the rare earth fixation, and the stability rate of the rare earth elements is less than 30%, which is difficult to be popularized on a large scale due to the limitation of climate and soil conditions. It is worth noting that no matter which kind of remediation, the existing technology is difficult to realize the efficient cooperation of simultaneously strengthening the removal of ammonia nitrogen and the stabilization of the rare earth elements, and it is difficult to meet the urgent needs of rapid, low-cost and environmentally friendly remediation of the tailing soil after the mine is closed. SUMMARY
[0004] In view of the problem that the existing soil remediation technology is difficult to simultaneously consider high residual ammonia nitrogen removal and rare earth element fixation, the present application provides a method for simultaneously treating residual ammonia nitrogen and exchangeable rare earth in rare earth tailing soil, which realizes integrated treatment of residual ammonia nitrogen removal and exchangeable rare earth fixation in soil through the double synergistic fixation mechanism of biological nitrification and rare earth elements, without chemical reagent residues and secondary environmental risks, and has a broad application prospect.
[0005] The technical scheme of the present application is as follows: The present application provides a method for simultaneously treating residual ammonia nitrogen and exchangeable rare earth in rare earth tailing soil, which uses Pseudomonas putida (Pseudomonas putida) and its extracellular polymers. Pseudomonas psychrotolerans The Pseudomonas putida is derived from soil around a rare earth mine, has good adaptability to rare earth mine soil, and has significant ammonia nitrogen biological nitrification characteristics. It was preserved in the Guangdong Microbial Culture Collection Center on August 22, 2025, and the preservation number is GDMCC NO:66872.
[0006] The present application also provides a specific step for the above-mentioned method for simultaneously treating residual ammonia nitrogen and exchangeable rare earth in rare earth tailing soil: S1, inoculate the Pseudomonas putida strain with preservation number GDMCC NO:66872 into LB culture medium and shake culture, wash the obtained bacterial cells with 0.9% sterile NaCl solution and resuspend, dilute to OD 600 =1.0 to obtain a Pseudomonas putida suspension; S2, heat the Pseudomonas putida suspension at 60℃ water bath for at least 40 min, then centrifuge to obtain supernatant and filter to obtain an extracellular polymer solution; S3, mix the Pseudomonas putida suspension and the extracellular polymer solution and uniformly inject or spray on the surface layer of rare earth tailing soil, keep the soil at 60% field capacity, and incubate at room temperature for 7-84 days.
[0007] Further, the LB culture medium in step S1 is prepared as follows: dissolve 10 grams of peptone, 5 grams of yeast extract and 10 grams of sodium chloride in 1000 mL ultrapure water, and adjust the pH to 7.2-7.4.
[0008] Further, the conditions for shake culture in step S1 include: culture temperature 28℃, rotation speed 135 r / min, culture time 5 days.
[0009] Further, in step S3, the Pseudomonas putida suspension and the extracellular polymer solution are mixed in a volume ratio of 1:2.
[0010] Further, the mixture of the Pseudomonas putida suspension and the extracellular polymer is applied to the surface layer of the soil at a dose of 1 L / m².
[0011] Compared with the prior art, the application has the following beneficial effects: 1. The application uses Pseudomonas putida for soil remediation for the first time; the application first converts NH4 + -N into NO3 - -N through biological nitrification of Pseudomonas putida, and in this process, the negatively charged NO3 -N is naturally leached out with rainwater, achieving efficient removal of NH4 + -N and release of ion adsorption vacancies in the soil, and then re-adsorbing and fixing REEs ions in the soil, avoiding the environmental migration risk of rare earth elements and their toxic effects on organisms, and achieving NH4 -N removal and REEs stabilization in one step, avoiding multiple treatments and long processes.
[0012] 2. The application also uses Pseudomonas putida extracellular polymer (EPS) in combination with Pseudomonas putida, the functional groups such as carboxyl and hydroxyl in the EPS molecules form stable complexes with exchangeable REEs, and the rare earth elements are converted into relatively stable organic bound state and residual state through the mineralization of the bacterial body, achieving double synergistic fixation of exchangeable rare earth elements, significantly improving the efficiency of rare earth element immobilization, and promoting the ecological remediation of rare earth tailings soil.
[0013] 3. The application uses local Pseudomonas putida naturally screened from rare earth tailings, combined with modular culture and EPS extraction, to achieve in-situ microbial remediation, and the reaction conditions are mild (25-30℃, normal pressure), with low energy consumption, less reagent consumption, no chemical reagent residue, and no secondary environmental risk; at the same time, EPS and microbial residues can also increase soil organic matter content, promote the formation of aggregates, and improve the soil water and fertilizer retention capacity, having broad application prospects.
[0014] 4. The Pseudomonas putida and its EPS of the application have good environmental persistence, and in the application process, only the soil moisture content needs to be maintained at 60% of the field water holding capacity, without the need for secondary inoculation or repeated spraying operation, to achieve long-term removal of ammonia nitrogen and stabilization of rare earth elements.
[0015] 5. The rare earth tailings soil ammonia nitrogen and exchangeable rare earth simultaneous treatment method of the application has a fast response speed, and the NH4 + -N removal rate can reach 99% within 84 days, and the exchangeable REEs ratio is reduced by ≥40%. BRIEF DESCRIPTION OF DRAWINGS
[0016] Figure 1The concentration distribution of different forms of nitrogen in the soil samples treated by Examples 1-4 and Comparative Examples 1-4 is shown in Table 1, wherein Figure 1 A represents the samples obtained from Comparative Examples 1-4 at the corresponding treatment time, Figure 1 B represents the samples obtained from Examples 1-4 at the corresponding treatment time.
[0017] Figure 2 The amoA gene abundance of ammonia-oxidizing microorganisms (AOA, AOB) in the soil samples treated by Examples 1-4 and Comparative Examples 1-4 is shown in Table 2, wherein Figure 2 A represents Comparative Examples 1-4, Figure 2 B represents Examples 1-4.
[0018] Figure 3 The distribution of each component of rare earth elements in the soil samples of Comparative Example 4 (A) and Example 4 (B) after 84 days of treatment is shown in Table 3. Figure 3 A) and Example 4 (B) after 84 days of treatment is shown in Table 3. Figure 3 B) after 84 days of treatment is shown in Table 3.
[0019] Figure 4 The variation trend of the physicochemical properties of the soil samples obtained from Examples 1-4 and Comparative Examples 1-4 with the treatment time is shown in Table 4, wherein the ck group represents the samples of the comparative examples at the corresponding treatment time, and the pp group represents the samples of the examples at the corresponding treatment time, Figure 4 A represents the pH of the soil, Figure 4 B represents the content of organic matter in the soil, Figure 4 C represents the content of free iron (DCB-Fe) in the soil, Figure 4 D represents the content of ammonium oxalate extractable iron (Oxalate-Fe) in the soil. DETAILED DESCRIPTION
[0020] The present application will be further described below in conjunction with the drawings and preferred embodiments, and the embodiments are only given to illustrate the present application, but not to limit the scope of the present application.
[0021] In the following examples, the materials, reagents, etc. used, unless otherwise specified, can be obtained from commercial channels; the methods in the following examples, unless otherwise specified, are conventional methods.
[0022] In the following embodiments, the Luria-Bertani (LB) medium is prepared according to the following steps: 10 grams of peptone, 5 grams of yeast extract and 10 grams of sodium chloride are dissolved in 1000 mL of ultrapure water, and the pH is adjusted to 7.2-7.4 to obtain the LB medium. Before use, the LB medium is autoclaved at 121°C.
[0023] The following embodiments relate to Pseudomonas putida (P. putida) which is a kind of bacteria that can grow at low temperatures. Pseudomonas psychrotoleransThe strain was preserved in Guangdong Microbial Culture Collection Center on August 22, 2025, the preservation unit code is GDMCC, the preservation number is GDMCC NO: 66872, and the address of the preservation unit is No. 59, Building 5, Guangzhou Xianlie Middle Road 100, Guangzhou. The cold-tolerant Pseudomonas strain was obtained by enrichment, isolation and purification from tailings soil in Longyan City, Fujian Province, and the process is as follows: (1) Add Y(III) metal salt solution to LB medium to prepare LB medium containing 50 mg / L Y(III), thereby obtaining LB-Y(III) medium; (2) Collect 1.0 g of soil from tailings in Longyan City, Fujian Province, and directly inoculate it into LB-Y(III) medium solution (50 mL) and cultivate at 30°C with 200 rpm shaking for 5 days; (3) Take 10 mL of supernatant and inoculate it again into LB-Y(III) medium solution (100 mL), and cultivate under the same conditions for 5 days. Repeat the above enrichment step 3 times; (4) Dilute the enrichment liquid by 10³ times, take 0.2 mL and inoculate it on LB-Y(III) medium agar plate, and cultivate at 30°C for 48 h; (5) Pick single colonies on fresh LB plates for repeated subculture and purification to obtain purified strains.
[0024] The above purified strain was sent to Shanghai Fuda Analysis and Testing Group for 16S rRNA sequencing. The identification result shows that the strain belongs to Pseudomonas putida, and its 16S rRNA sequence is shown as SEQ ID NO: 1.
[0025] Example 1 The present embodiment provides a method for simultaneously treating rare earth tailings soil ammonia nitrogen residues and exchangeable rare earth, which uses the above-mentioned Pseudomonas putida and the extracellular polymers extracted therefrom, and comprises the following steps: S1, inoculate the Pseudomonas putida strain into 200 mL of LB medium, and place it in a shaking constant temperature incubator at 28°C and 135 rpm for 5 days. After completion, centrifuge to collect the bottom bacterial precipitate, wash the obtained bacterial body with 0.9% sterile NaCl solution for 3 times, and then resuspend and dilute the obtained bacterial body to OD 600 =1.0 using 0.9% sterile NaCl solution to obtain a Pseudomonas putida suspension, which is stored at 4°C before use; S2, heat part of the Pseudomonas putida suspension obtained in step S1 in a 60°C water bath for 40 min, then centrifuge at 12000 rpm for 5 min, filter the supernatant through a 0.45 μm filter membrane to obtain an extracellular polymer solution; S3. Mix 2.5 mL of psychrophilic Pseudomonas suspension with 5 mL of extracellular polymeric solution and dilute at 1 L / m 2 The dosage was evenly sprayed onto the surface of the rare earth tailings soil in a plastic bottle 15 cm high and 12 cm in diameter. Water was replenished regularly to keep the soil at 60% field capacity, and the soil was left to stand for 7 days.
[0026] Examples 2-4 follow the same steps as Example 1 to simultaneously treat ammonia nitrogen residue and exchangeable rare earth in rare earth tailings soil. The difference from Example 1 is that in step S3, after mixing the psychrophilic Pseudomonas suspension and the extracellular polymer solution and applying it to the soil surface, the soil is kept at 60% field capacity and incubated statically for 14, 42 and 84 days, respectively.
[0027] Comparative Example 1 This comparative example uses sterile deionized water for the simultaneous treatment of ammonia nitrogen residue and exchangeable rare earth elements in rare earth tailings soil, including the following steps: Add 7.5 mL of sterile deionized water at a rate of 1 L / m 2 The dosage was evenly sprayed onto the surface of the rare earth tailings soil in a plastic bottle 15 cm high and 12 cm in diameter. Water was replenished regularly to keep the soil at 60% field capacity, and the soil was left to stand for 7 days.
[0028] Comparative Examples 2-4 were carried out in the same manner as Comparative Example 1, with simultaneous treatment of ammonia nitrogen residue and exchangeable rare earth in rare earth tailings soil. The difference from Comparative Example 1 was that after applying sterile deionized water to the soil surface, the soil was kept at 60% field capacity and incubated for 14, 42 and 84 days, respectively.
[0029] Performance testing This invention samples were taken from soils treated in Examples 1-4 and Comparative Examples 1-4. The collected samples were freeze-dried and then evaluated for ammonia nitrogen removal, rare earth element stabilization, and soil physicochemical properties. The results are as follows: Figure 1 The concentration distribution of different forms of nitrogen in soil samples obtained from Examples 1-4 and Comparative Examples 1-4 is shown. The results indicate that soil samples treated with sterile deionized water for 7-84 days ( Figure 1 In A), compared to the untreated soil sample (day 0), the ammonia nitrogen concentration in soil samples treated for 7–84 days did not change significantly, while... Figure 1 As shown in Figure B, compared to the untreated soil sample (day 0), the soil sample treated with the combined psychrophilic Pseudomonas aeruginosa and the extracellular polymers extracted therefrom showed a significant reduction in ammonia nitrogen content. By day 84, ammonia nitrogen and NH4+ were almost completely removed. + -N removal rate can reach 99%.
[0030] Figure 2 The abundance of the amoA gene in ammonia-oxidizing microorganisms (AOA, AOB) in Examples 1-4 and Comparative Examples 1-4 was measured. The results showed that Comparative Examples 1-4, which were treated with deionized water only, had a significantly higher abundance of the amoA gene. Figure 2 The bioactivity of AOA and AOB in A) was significantly lower than that in Examples 1-4. Figure 2 As can be seen from the activity in B), the combined use of the cold-resistant Pseudomonas aeruginosa of the present invention and the extracellular polymer extracted therefrom can significantly improve the conversion efficiency of ammonia nitrogen to nitrate nitrogen.
[0031] Figure 3 After 84 days of treatment, Comparative Example 4 ( Figure 3 A) and Example 4 ( Figure 3 The distribution of rare earth elements in soil samples (B) shows that after treatment with the cold-resistant Pseudomonas aeruginosa and the extracellular polymers extracted therefrom, the exchangeable rare earth elements in the soil samples are almost completely converted into relatively stable organic-bound or residual states.
[0032] Figure 4 The results show the changes in the physicochemical properties of soil samples obtained in Examples 1-4 and Comparative Examples 1-4 over time. The results indicate that, compared to soil samples treated with sterile deionized water (CK group), soil samples treated with the combined use of the psychrophilic Pseudomonas aeruginosa and its extracted extracellular polymers (PP group) showed significantly increased organic matter and oxalate-extractable iron (Oxalate-Fe) content. Therefore, the method provided by this invention can effectively improve soil fertility and promote the ecological restoration of rare earth tailings soil.
Claims
1. A method for simultaneously treating rare earth tailing soil ammonia nitrogen residues and exchangeable rare earths, characterized in that, The present application is characterized in that a cold-tolerant Pseudomonas (Pseudomonas sp. Pseudomonas psychrotolerans ) and its extracellular polymers are used; the cold-tolerant Pseudomonas strain is preserved in the Guangdong Microbial Culture Collection Center on August 22, 2025, and the preservation number is GDMCC NO: 66872.
2. The method for simultaneously treating the residual ammonia-nitrogen and the exchangeable rare earth in the rare earth tailing soil according to claim 1, characterized in that, The method comprises the following steps: S1, inoculate the cold-tolerant Pseudomonas strain with the preservation number GDMCC NO: 66872 into LB medium for shaking culture, wash the obtained bacterial cells with 0.9% sterile NaCl solution and resuspend, dilute to OD 600 = 1.0 to obtain a cold-tolerant Pseudomonas suspension; S2, heating the Pseudomonas psychrotolerans suspension at 60°C for at least 40 min, then centrifuging to obtain supernatant and filtering to obtain an extracellular polymer solution; S3, mixing the Pseudomonas psychrotolerans suspension and the extracellular polymer solution and uniformly injecting or spraying them on the surface layer of the rare earth tailing soil, keeping the soil at 60% field capacity and standing for 7-84 days at room temperature.
3. The method according to claim 2, wherein the method is characterized by, The LB medium in step S1 is prepared as follows: 10 g of peptone, 5 g of yeast extract and 10 g of NaCl are dissolved in 1000 mL of ultrapure water, and the pH is adjusted to 7.2-7.
4.
4. The method for synchronous treatment of rare earth tailing soil ammonia-nitrogen residue and exchangeable rare earth state according to claim 2, characterized in that, The conditions for the oscillation culture in step S1 include: a culture temperature of 28°C, a rotation speed of 135 r / min, and a culture time of 5 days.
5. The method for simultaneous treatment of soil ammonia-nitrogen residue and exchangeable rare earth in rare earth tailings according to claim 2, characterized in that, The Pseudomonas psychrotolerans suspension and the extracellular polymer solution are mixed at a volume ratio of 1:2 in step S3.
6. The method for simultaneous treatment of soil ammonia-nitrogen residue and exchangeable rare earth in rare earth tailings according to claim 2, characterized in that, The mixed solution obtained by mixing the Pseudomonas psychrotolerans suspension and the extracellular polymer solution is applied to the surface layer of the soil at a dose of 1 L / m².