Resourceful treatment method for wastewater containing high-concentration uranium

Abstract

The invention discloses a resourceful treatment method for wastewater containing high-concentration uranium, and belongs to the technical field of radioactive wastewater treatment. According to the method, a double-chamber electrolytic tank is adopted, a positive electrode chamber and a negative electrode chamber are separated through a PVDF micro-filtration membrane, uranium ions are driven to migrate directionally through the electrochemical potential gradient between high-concentration wastewater and low-concentration wastewater, and efficient migration and reduction of uranium are achieved through electrolysis under low voltage with a hastelloy net as an anode and graphite as a cathode. After electrolysis, uranium is enriched and recovered in the form of high-purity UO2, and the uranium content of wastewater is reduced to 20 mg / L or below. The method has the advantages of low energy consumption, no chemical addition, high resource recovery rate, environmental friendliness and the like, and is suitable for treatment and resource utilization of the high-concentration uranium-containing acidic wastewater.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of radioactive wastewater treatment, and particularly relates to a resource treatment method for high-concentration uranium-containing wastewater. BACKGROUND

[0002] Uranium is an important strategic resource and radioactive element, and is widely used in nuclear power, national defense and medical research (such as isotope application). In the process of uranium ore processing (such as the use of sulfuric acid-hydrofluoric acid mixed acid to decompose the ore in the tantalum-niobium alloy industry) and nuclear fuel cycle, high-concentration uranium-containing acidic wastewater (uranium content is usually hundreds to thousands of mg / L) is generated. The traditional treatment mainly adopts a chemical precipitation method (such as neutralization to p=6-7 by using lime milk or sodium hydroxide), so that uranium is precipitated in the form of diuranate (such as Na2U2O7). The precipitate is solidified and landfilled as radioactive hazardous waste.

[0003] This method not only occupies a large amount of land, has long-term leakage and environmental pollution risks, but also produces a large amount of uranium-containing sludge (hazardous waste residue), which increases the difficulty and cost of subsequent disposal, and sometimes it is difficult to stabilize to meet the strict U<20mg / L discharge standard.

[0004] In the prior art, for example, application No. 2021101900337 provides a microbial electrolysis cell and a treatment method for uranium-containing wastewater. The microbial electrolyte includes: an electrolysis cell; an electrolyte solution and uranium-containing wastewater arranged in the electrolysis cell; a biological anode and a biological cathode arranged in the electrolysis cell; an external circuit connecting the biological anode and the biological cathode; and the microbial electrolysis cell is used for microbial electrochemical reduction of the uranium-containing wastewater. The microbial electrolysis cell can produce a large amount of hydrogen gas while treating the uranium-containing wastewater. In another prior art, for example, application No. 2017102846973 discloses an efficient treatment system for uranium-containing wastewater, which includes a chelating agent adding pool, a pH adjusting pool, an electrolysis pool and a precipitation pool connected in sequence.

[0005] Therefore, it is of great practical significance to develop an efficient and environmentally friendly resource treatment method for high-concentration uranium-containing waste residue. SUMMARY

[0006] The present application mainly aims at the problem that a large amount of hydrogen gas is easily generated in the process of decomposing tantalum-niobium alloy ore, and avoids the problem that the calcination product is difficult to decompose caused by the conventional hydrogen gas generation avoidance scheme.

[0007] A resource treatment method for high-concentration uranium-containing wastewater includes the following steps: Step 1: A double-chamber electrolysis cell is used, and a hydrophobic polyvinylidene fluoride (PVDF) microfiltration membrane is used to separate the anode chamber and the cathode chamber of the electrolysis cell; Step 2: Low-uranium wastewater is injected into the anode chamber, and high-uranium wastewater is injected into the cathode chamber, and an electrochemical potential gradient is formed by using the initial uranium concentration difference; Step 3: using a Hastelloy mesh as the positive electrode, a high-purity graphite plate as the negative electrode, and applying a 1.5-3V direct current voltage for electrolysis for 60-180min; Step 4: stirring the cathode chamber liquid during electrolysis; Step 5: after the electrolysis, separating the cathode chamber liquid by suction filtration, drying the separated black filter residue to obtain a uranium-rich product, and collecting the purified wastewater filtered from the cathode chamber and the anode chamber, respectively, detecting the uranium content and pH value of the wastewater, and discharging the wastewater after confirming that the uranium content is less than 20mg / L.

[0008] Preferably, the hydrophobic polyvinylidene fluoride (PVDF) microfiltration membrane has a pore size of 0.18-0.3μm, a thickness of 100-200μm, and a porosity of 60-80%.

[0009] Preferably, the stirring of the cathode chamber uses magnetic stirring at a speed of 200-400rpm to prevent excessive adhesion or deposition of solid products on the electrode surface. The stirring reaction phenomenon is that the cathode liquid changes from black purple to dark green with slag generation, the anode changes from dark green to purple black, and a small amount of suspended matter appears on the surface of the liquid.

[0010] Preferably, after the electrolysis in Step 5, the separation of the cathode chamber liquid uses vacuum suction filtration with a filter membrane pore size of 0.3-0.5μm.

[0011] Preferably, the Hastelloy mesh is 80-150 mesh.

[0012] Preferably, the high-uranium wastewater has a pH of 2.5-3.5 and a uranium concentration of 500-2000mg / L.

[0013] Preferably, the uranium content in the uranium-rich product is ≥95wt%, and the main phase is UO2.

[0014] The beneficial effects of the present application are: 1. Utilizing the concentration gradient to drive the directional migration of uranium ions, with a migration efficiency of >98%, significantly reducing external energy consumption; 2. No need to add a large amount of chemical reagents, saving cost and reducing sludge production; 3. Using a Hastelloy mesh as the anode, which has excellent corrosion resistance in strong acidic (pH 2.5-3.5) and fluorine-containing environments, effectively solving the problem of electrode passivation and ensuring long-term stable operation of the process.

[0015] 4. Compared with the microbial electrolysis cell method in the background technology, the present invention has a fundamental difference from the prior art in terms of safety: it does not require the use of complex microbial electrolytes and their maintenance system, which not only reduces the technical complexity and operating costs, but more importantly, its unique electrochemical process does not produce a large amount of hydrogen gas, thereby completely avoiding the potential explosion risk and ensuring the environmental friendliness and operational safety of the treatment process.

[0016] 5. Compared to the high-efficiency uranium wastewater treatment systems in the background art, this invention eliminates the need for additional chelating agents and multi-stage equalization tanks. By constructing an electrochemical potential gradient based on the initial uranium concentration difference, it achieves deep purification of high-uranium wastewater, reducing the uranium concentration to below 20 mg / L, while simultaneously enriching and recovering high-purity UO2 (uranium content ≥ 95 wt%) in situ. This achieves efficient directional migration and reduction recovery of uranium ions, simplifies the process, and avoids introducing foreign chemicals, thus reducing treatment costs and the risk of secondary pollution. Attached Figure Description

[0017] Figure 1 This is a schematic diagram illustrating the principle of an embodiment. Detailed Implementation

[0018] The following is in conjunction with the appendix Figure 1 The present invention will be described in detail with reference to the embodiments, but the scope of protection of the present invention is not limited thereto.

[0019] (1) Example 1: Step 1: Prepare experimental materials Cathodic solution: high uranium wastewater, pH: 2.8, volume: 150 mL, uranium content: 1034 mg / L; Anode solution: low uranium wastewater, pH: 5.2, volume: 150 mL, uranium content: 2 mg / L; Step 2: Device Assembly Electrolytic cell volume: 200mL / chamber, effective liquid volume: 150mL; Electrodes: Anode—Hastelloy C276 mesh (100 mesh), Cathode—High-purity graphite plate (500mm×500mm×5mm); Separation membrane: hydrophobic polyvinylidene fluoride (PVDF) microfiltration membrane (pore size 0.22 μm, thickness 150 μm, porosity 70%).

[0020] Step 3: Running parameters The constant voltage is 2V, the current density is 8-10mA / cm2, and the electrolysis time is 2h. The cathode chamber is magnetically stirred at 300rpm to prevent precipitation from adhering to the electrode.

[0021] Step 4: Result Processing The filtered cathode chamber waste liquid was vacuum filtered (filter membrane pore size 0.45 μm), dried and weighed to obtain 4.01 g; XRD analysis: the main phase of the filter residue was crystalline UO2, and the uranium content was ≥95 wt%; The filtrate after filtering of the cathode and anode was sent for detection of the uranium content, the uranium content of the cathode was 15 mg / L, and the uranium content of the anode was 18 mg / L, and the uranium content of the two-stage waste water reached the discharge standard of GB8978-1996.

[0022] Table 1 experimental results table

[0023] Comparative example: In order to show the difference between the present application and the prior art, the traditional chemical precipitation method and the existing electrochemical method are introduced as comparative examples.

[0024] Table 2 comparison of treatment effects of the present application and comparative examples

[0025] Through comparison, it can be seen that the present application realizes efficient and deep removal of uranium and high-purity recovery without adding chemical reagents and generating hydrogen, and the treatment effect is better than that of the traditional method and the prior art.

[0026] In the tantalum-niobium industry, when sulfuric acid-hydrofluoric acid mixed acid is used to decompose uranium-containing ores, uranium elements are difficult to be leached and often accompany in strong acid waste liquid after ore decomposition. The present application provides a high-concentration uranium-containing wastewater resource treatment method, which has the advantages of being able to efficiently remove uranium in wastewater to reach the national discharge standard; greatly reducing the generation of high-uranium hazardous waste residue; enriching and recycling the removed uranium in the form of high-purity and easy-to-recover (such as UO2), realizing resource recycling; avoiding or minimizing the addition of additional chemical reagents, reducing treatment cost and secondary pollution risk, etc. The method uses a double-chamber electrolytic cell, separates the anode and cathode chambers with a PVDF microfiltration membrane, uses the electrochemical potential gradient between high and low concentration wastewater to drive the directional migration of uranium ions, uses Hastelloy mesh as the anode and graphite as the cathode, and electrolyzes at low voltage to realize efficient migration and reduction of uranium. After electrolysis, uranium is enriched and recycled in the form of high-purity UO2, and the uranium content of the wastewater is reduced to below 20 mg / L. The present application has the advantages of low energy consumption, no chemical addition, high resource recovery rate, environmental friendliness, etc., and is suitable for the treatment and resource utilization of high-concentration uranium-containing acidic wastewater.

[0027] Obviously, the above embodiments of the present application are only examples for illustrating the present application, and are not intended to limit the embodiments of the present application. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. It is not necessary or possible to exhaust all embodiments. The obvious changes or variations derived from the essential spirit of the present application still belong to the protection scope of the present application.

Claims

1. A method for the resource-based treatment of wastewater containing high concentrations of uranium, characterized in that, It includes the following steps: Step 1: A dual-chamber electrolytic cell is used, with a hydrophobic polyvinylidene fluoride (PVDF) microfiltration membrane separating the anode chamber and the cathode chamber of the electrolytic cell; Step 2: Low-uranium wastewater is injected into the anode chamber and high-uranium wastewater is injected into the cathode chamber, utilizing the initial uranium concentration difference to form an electrochemical potential gradient; Step 3: Using Hastelloy mesh as the positive electrode and high-purity graphite plate as the negative electrode, electrolyze for 60-180 minutes with a DC voltage of 1.5-3V. Step 4: Stir the liquid in the cathode chamber during electrolysis; Step 5: After electrolysis, the cathode chamber liquid is separated by vacuum filtration. The separated black filter residue is dried to obtain uranium-rich product. The purified wastewater after filtration in the cathode and anode chambers is collected separately, and its uranium content and pH value are tested. After confirming that the uranium content is <20mg / L and meets the standard, it is discharged.

2. The resource-based treatment method for wastewater containing high concentrations of uranium according to claim 1, characterized in that: The hydrophobic polyvinylidene fluoride (PVDF) microfiltration membrane has a pore size of 0.18-0.3 μm, a thickness of 100-200 μm, and a porosity of 60-80%.

3. The resource-based treatment method for wastewater containing high concentrations of uranium according to claim 1, characterized in that: The cathode chamber is stirred magnetically at a speed of 200-400 rpm to prevent excessive adhesion or deposition of solid products on the electrode surface.

4. The resource-based treatment method for wastewater containing high concentrations of uranium according to claim 1, characterized in that: After electrolysis in step 5, the cathode chamber liquid is separated by vacuum filtration, and the filter membrane has a pore size of 0.3-0.5 μm.

5. The resource-based treatment method for wastewater containing high concentrations of uranium according to claim 1, characterized in that: The Hastelloy mesh is 80-150 mesh.

6. The resource-based treatment method for wastewater containing high concentrations of uranium according to claim 1, characterized in that: The high-uranium wastewater has a pH of 2.5-3.5 and a uranium concentration of 500-2000 mg / L.

7. The resource-based treatment method for wastewater containing high concentrations of uranium according to claim 1, characterized in that: The uranium-rich product contains ≥95wt% uranium and the main phase is UO2.

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