Method for removing organic matter in uranium-containing nitric acid waste liquid by electro-catalytic oxidation

Abstract

The present application relates to the technical field of uranium purification conversion, and particularly relates to a method for removing organic matters in uranium-containing nitric acid-containing waste liquid by electro-catalytic oxidation, which comprises the following steps: insoluble organic matters in the uranium-containing nitric acid-containing waste liquid are removed by an oil removal tower, and the water phase is used as an original liquid for extraction; suspended matters, oil and gum substances in the raffinate water after extraction are removed by a gas float oil removal machine; the water phase after removal of the suspended matters, oil and gum substances is degraded by an electro-catalytic oxidation device under the action of an applied electric field; the mixed liquid after electro-catalytic oxidation is subjected to flocculation and sedimentation, so that the flocculation in the mixed liquid is polymerized and removed by filtration, and then the filtrate is transported to an evaporation concentration system and a membrane treatment system for deep uranium removal. The present application removes the organic matters in the uranium-containing nitric acid-containing waste liquid by electro-catalytic oxidation, so that the chemical oxygen demand in the waste liquid is reduced to below 100 mg / L, and the feeding requirements of the subsequent uranium deep treatment process and the final discharge requirements are met.

Description

Technical Field

[0001] This invention relates to the field of uranium purification and conversion technology, and in particular to a method for removing organic matter from uranium-containing and nitric acid-containing waste liquid by electrocatalytic oxidation. Background Technology

[0002] The wastewater generated by the uranium purification and conversion production line mainly includes distillation residue, organic phase alkaline washing liquid, denitrification tail gas scrubbing liquid, and hydrogen reduction tail gas bubbling water. This wastewater contains sodium ions, nitrate ions, ammonium ions, uranium ions, as well as complexes of cracking products and metal impurities. It also contains small amounts of laundry wastewater, detergent wastewater, and membrane filtration concentrate. The organic phase in the mixed water mainly consists of hydrogenated kerosene, TBP, MBP, DBP, and surfactants, with a COD of approximately 800-1000 mg / L. In existing technologies, direct evaporation concentration and membrane treatment systems are used for deep uranium processing. Excessive organic phase content reduces the efficiency of evaporation concentration and increases the risk of membrane fouling.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a method for removing organic matter from uranium-containing and nitric acid-containing wastewater by electrocatalytic oxidation. This method uses electrocatalytic oxidation to remove organic matter from uranium-containing and nitric acid-containing wastewater, reducing the chemical oxygen demand (COD) in the wastewater to below 100 mg / L, thus meeting the feeding requirements of subsequent uranium deep processing processes and the final emission standards.

[0005] This invention provides a method for removing organic matter from uranium- and nitric acid-containing waste liquid by electrocatalytic oxidation, comprising the following steps:

[0006] S1. Uranium- and nitric acid-containing waste liquid is passed through an oil removal tower to remove insoluble organic matter, while the aqueous phase is used as the extraction solution for extraction.

[0007] S2. The raffinate after extraction is passed through an air flotation oil removal machine to remove suspended solids, oils, and colloidal substances from the raffinate.

[0008] S3. The aqueous phase after removing suspended solids, grease, and colloids is degraded by an electrocatalytic oxidation device under the action of an external electric field to degrade organic matter.

[0009] S4. The mixture after electrocatalytic oxidation is subjected to flocculation and sedimentation, and the flocculent matter is polymerized and removed by filtration. The filtrate is then transported to the evaporation concentration system and membrane treatment system for deep uranium removal.

[0010] Preferably, step S1 includes the following steps:

[0011] S11. Adjust the acidity of the uranium- and nitric acid-containing waste liquid to 2-4 mol / L;

[0012] S12. After the waste liquid is separated by solid-liquid separation to remove slag, the filtrate is sent to the oil removal tower to remove the organic phase.

[0013] S13. The aqueous phase is transported to the extraction tank as the extraction solution for extraction.

[0014] Preferably, in step S12, the organic phase separated by the oil removal tower is transported to the emulsion receiving tank, and then the sludge is barreled for further processing.

[0015] Preferably, in step S1, the uranium-containing nitric acid waste liquid includes: distillation residue, organic phase alkaline washing liquid, denitrification tail gas scrubbing liquid, and hydrogen reduction tail gas bubbling water. The mixed organic phase is pretreated in an oil removal tower, and the organic phase removal efficiency can reach more than 60%.

[0016] Preferably, step S2 includes the following steps:

[0017] S21. The extracted raffinate is sent to the air flotation oil removal machine for dissolved air operation. The microbubbles combine with the suspended solids, oils, and colloidal substances in the waste liquid and float to the surface of the water phase for removal. The water phase overflows into the mixing tank.

[0018] An air flotation oil removal machine is a solid-liquid separation device that effectively removes suspended solids, grease, and colloidal substances from wastewater. The microbubbles it generates combine with suspended solids and oil in the wastewater, making the combined substances less dense than water, and causing them to gradually float to the surface to form scum. A scraper system on the water surface scrapes the scum and oil into a collection tank, thus achieving the effect of organic phase pretreatment.

[0019] S22. The wastewater from the laundry room, the concentrated water from the membrane filtration, and the liquid alkali are transported to the mixing tank for mixing.

[0020] S23. The mixed waste liquid in the mixing tank is transported to the buffer tank, and then transported to the electrocatalytic oxidation device by a magnetic pump.

[0021] Preferably, in step S22, the laundry wastewater is treated by submerged ultrafiltration before being transported to the mixing tank, and the membrane filtration concentrate comes from the membrane treatment ultrafiltration and nanofiltration system.

[0022] Preferably, step S3 includes the following steps:

[0023] S31. Under the action of an external electric field, the electrocatalytic oxidation device degrades the organic matter in the mixed waste liquid;

[0024] Considering that the remaining COD will be concentrated and returned to the treatment process in subsequent treatment steps, the oil-water separation unit alone cannot meet the treatment requirement of COD ≤ 100 mg / L in the treated wastewater. The uranium- and nitric acid-containing wastewater containing organic phases does not contain fluoride ions and is not prone to corrosion of the electrodes under acidic conditions. Therefore, it was determined that electrocatalytic oxidation would be used to directly degrade the residual TBP, hydrogenated kerosene, and surfactants in the wastewater under the action of an external electric field.

[0025] S32. The waste liquid after electrocatalytic oxidation is transported to a gas-liquid separator to remove the hydrogen produced during the electrocatalytic oxidation process;

[0026] S33. Perform COD detection on the waste liquid after gas-liquid separation.

[0027] Preferably, in step S33, the COD of the waste liquid after gas-liquid separation is detected. When the COD is greater than 100 mg / L, the waste liquid is returned to the electrocatalytic oxidation device for organic matter degradation. When the COD is less than or equal to 100 mg / L, the waste liquid undergoes flocculation and sedimentation.

[0028] Preferably, step S4 includes the following steps:

[0029] S41. Waste liquid with COD below 100 mg / L is transported to a flocculation sedimentation tank for collection;

[0030] S42. Add flocculant to aggregate the flocculent material, press it into a filter cake using a filter press, and collect the filtrate in a filtrate receiving tank.

[0031] Because flocculent insoluble matter appears in the wastewater after electrocatalytic oxidation, a flocculation and sedimentation device was added. The flocculent insoluble matter is removed by adding flocculant to precipitate it and then filtering it out.

[0032] S43. Adjust the pH of the filtrate to 6 and transfer it to the evaporation concentration system and membrane treatment system for deep uranium removal.

[0033] Preferably, in step S42, the filter cake is loaded into drums and transported to a uranium-containing solid waste treatment system for processing.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) The process route for removing organic matter from uranium-containing and nitric acid-containing waste liquid proposed in this invention achieves COD≤100mg / L for uranium-containing and nitric acid-containing waste liquid, ensuring the stable operation of subsequent deep uranium removal processes.

[0036] (2) The electrocatalytic oxidation reaction conditions of the present invention are mild and can be carried out at room temperature and pressure. The reaction conditions can be adjusted at any time by changing the voltage and current. It has good controllability and is simple and flexible to operate without complicated operations.

[0037] (3) Electrocatalytic oxidation removes organic matter from waste liquid. During the catalytic oxidation of organic matter, electron transfer only occurs between the electrode and the wastewater components. The oxidation reaction relies on the hydroxyl radicals generated by the system itself. No additional reagents or catalysts are needed, and there is no secondary pollution.

[0038] (4) An air bubbling and gas-liquid separation process was added after electrocatalytic oxidation to avoid the safety risks of hydrogen generated during the electrocatalytic oxidation process.

[0039] (5) By using pressure filtration to separate solids and liquids and remove uranium-containing solid precipitates generated by electrocatalytic oxidation, the problem of uranium-containing solid precipitates generated during the electrocatalytic oxidation process affecting the stable operation of subsequent deep uranium removal equipment is avoided. Attached Figure Description

[0040] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0041] Figure 1 The flowchart of the method for removing organic matter from uranium- and nitric acid-containing waste liquid by electrocatalytic oxidation provided by the present invention is shown. Detailed Implementation

[0042] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0043] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form includes the plural form unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0044] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Example

[0046] like Figure 1 As shown in the figure, this embodiment provides a method for removing organic matter from uranium-containing and nitric acid-containing waste liquid by electrocatalytic oxidation, including the following steps:

[0047] S1. Uranium-containing and nitric acid-containing waste liquid (filtrate from the uranium purification and extraction system) is processed by an oil removal tower to remove insoluble organic matter, while the aqueous phase is used as the extraction raw liquid for extraction. The uranium-containing and nitric acid-containing waste liquid includes: distillation residue, organic phase alkaline washing liquid, denitrification tail gas rinsing liquid, and hydrogen reduction tail gas bubbling water.

[0048] Specifically, step S1 includes the following steps:

[0049] S11. Adjust the acidity of the uranium- and nitric acid-containing waste liquid to 2-4 mol / L;

[0050] S12. After the waste liquid passes through the filter press for solid-liquid separation and slag removal, the filtrate is transported to the oil removal tower to remove insoluble organic matter. The organic phase separated from the oil removal tower is then transported to the emulsion receiving tank, and then the sludge is barreled for further processing.

[0051] S13. The aqueous phase is transported to the extraction tank as the extraction solution for extraction.

[0052] S2. The raffinate after extraction is passed through an air flotation oil removal machine to remove suspended solids, oils, and colloidal substances from the raffinate.

[0053] Specifically, step S2 includes the following steps:

[0054] S21. The extracted raffinate is sent to the air flotation oil removal machine for dissolved air operation. The microbubbles combine with the suspended solids, oils, and colloidal substances in the waste liquid and float to the surface of the water phase for removal. The water phase overflows into the mixing tank.

[0055] S22. The laundry wastewater, membrane filtration concentrate, and liquid alkali are transported to the mixing tank for mixing; specifically, the laundry wastewater is treated by submerged ultrafiltration before being transported to the mixing tank, and the membrane filtration concentrate comes from the membrane treatment system.

[0056] S23. The mixed waste liquid in the mixing tank is transported to the buffer tank (the pH and other parameters can be adjusted), and then transported to the electrocatalytic oxidation device by a magnetic pump.

[0057] S3. After removing suspended solids, grease, and colloids, the aqueous phase is degraded by an electrocatalytic oxidation device under the action of an external electric field. To ensure that the COD in the effluent is below 100 mg / L, an automatic interlocking device will fully control the residence time of the wastewater in the device.

[0058] Specifically, step S3 includes the following steps:

[0059] S31. Under the action of an external electric field, the electrocatalytic oxidation device degrades the organic matter in the mixed waste liquid;

[0060] S32. The waste liquid after electrocatalytic oxidation is transported to a gas-liquid separator to remove the hydrogen produced in the electrocatalytic oxidation process; the uranium-containing and nitric acid-containing waste liquid after electrocatalytic oxidation is subjected to gas-liquid separation by motor stirring to remove the hydrogen produced in the electrocatalytic oxidation process, and the gas produced by gas-liquid separation is discharged to the exhaust system.

[0061] S33. Perform COD testing on the waste liquid after gas-liquid separation; specifically, perform COD testing on the waste liquid after gas-liquid separation. When the COD is greater than 100 mg / L, the waste liquid is returned to the electrocatalytic oxidation device for organic matter degradation. When the COD is less than or equal to 100 mg / L, the waste liquid is subjected to flocculation and sedimentation.

[0062] In one specific embodiment, the electrocatalytic oxidation process is carried out in two stages, with the following specific steps:

[0063] The mixed waste liquid (COD approximately 800-1000 mg / L) in the buffer tank enters the electrocatalytic oxidation device 1 (set maximum current 1400A, voltage 80V, target current 1000A) for organic matter degradation. After gas-liquid separation in the gas-liquid separator 1, and multiple cycles between the electrocatalytic oxidation device 1 and the gas-liquid separator 1, when the waste liquid (COD approximately 200-300 mg / L) reaches the overflow condition, it overflows into the gas-liquid separator 2, where it undergoes gas-liquid separation. After separation, COD is detected. When COD is less than or equal to 100 mg / L, the waste liquid undergoes flocculation and sedimentation. When COD is greater than 100 mg / L, the waste liquid enters the electrocatalytic oxidation device 2 (set maximum current of 1200A, voltage of 120V, and target current of 1000A) for organic matter degradation. After gas-liquid separation in the gas-liquid separator 2, COD is detected again. After multiple cycles, the waste liquid undergoes flocculation and sedimentation when COD is detected to be less than or equal to 100 mg / L.

[0064] S4. The mixture after electrocatalytic oxidation is subjected to flocculation and sedimentation, and the flocculent matter is polymerized and removed by filtration. The filtrate is then transported to the evaporation concentration system and membrane treatment system for deep uranium removal.

[0065] Specifically, step S4 includes the following steps:

[0066] S41. Waste liquid with COD below 100 mg / L is transported to a flocculation sedimentation tank for collection;

[0067] S42. Add flocculant to aggregate the flocculent material, press it into a filter cake using a filter press, receive the filtrate in a filtrate receiving tank, and transport the filter cake in drums to a uranium-containing solid waste treatment system for processing.

[0068] S43. Adjust the pH of the filtrate to 6 and transfer it to the evaporation concentration system and membrane treatment system for deep uranium removal.

[0069] In summary, the "oil removal tower + air flotation oil removal machine + two-stage electrocatalytic oxidation" process of this invention is used to treat the organic phase in uranium purification and conversion containing uranium and nitric acid. The oil removal tower performs preliminary treatment on the organic phase after mixing the distillation residue, organic phase alkaline washing liquid, denitrification tail gas scrubbing liquid, and hydrogen reduction tail gas bubbling water. The air flotation oil removal machine further removes organic impurities from the extraction residue water. The two-stage electrocatalytic oxidation can achieve a COD removal rate of over 95% in the waste liquid.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for removing organic matter from uranium- and nitric acid-containing wastewater by electrocatalytic oxidation, characterized in that, Includes the following steps: S1. The uranium- and nitric acid-containing waste liquid is passed through an oil removal tower to remove insoluble organic matter, while the aqueous phase is used as the extraction solution for extraction; step S1 includes the following steps: S11. Adjust the acidity of the uranium-containing and nitric acid-containing waste liquid to 2-4 mol / L; S12. After the waste liquid is separated by solid-liquid separation to remove slag, the filtrate is sent to the oil removal tower to remove the organic phase. S13. The aqueous phase is transferred to the extraction tank as the extraction solution for extraction; S2. The raffinate after extraction is passed through an air flotation oil removal machine to remove suspended solids, oils, and colloidal substances; step S2 includes the following steps: S21. The extracted raffinate is sent to the air flotation oil removal machine for dissolved air operation. The microbubbles combine with the suspended solids, oils, and colloidal substances in the waste liquid and float to the surface of the water phase for removal. The water phase overflows into the mixing tank. S22. The wastewater from the laundry room, the concentrated water from the membrane filtration, and the liquid alkali are transported to the mixing tank for mixing. S23. The mixed waste liquid in the mixing tank is transported to the buffer tank, and then transported to the electrocatalytic oxidation device by a magnetic pump; S3. After removing suspended solids, grease, and colloids, the aqueous phase is subjected to electrocatalytic oxidation under an applied electric field to degrade organic matter; step S3 includes the following steps: S31. Under the action of an external electric field, the electrocatalytic oxidation device degrades the organic matter in the mixed waste liquid; S32. The waste liquid after electrocatalytic oxidation is transported to a gas-liquid separator to remove the hydrogen produced during the electrocatalytic oxidation process; S33. Perform COD testing on the waste liquid after gas-liquid separation. When the COD is greater than 100 mg / L, the waste liquid is returned to the electrocatalytic oxidation device for organic matter degradation. When the COD is less than or equal to 100 mg / L, the waste liquid is subjected to flocculation and sedimentation. S4. The mixture after electrocatalytic oxidation is subjected to flocculation and sedimentation, and the flocculent matter is polymerized and removed by filtration. The filtrate is then transported to the evaporation concentration system and membrane treatment system for deep uranium removal.

2. The method for removing organic matter from uranium- and nitric acid-containing wastewater by electrocatalytic oxidation according to claim 1, characterized in that, In step S12, the organic phase separated by the oil removal tower is transported to the emulsion receiving tank, and then the sludge is loaded into barrels for further processing.

3. The method for removing organic matter from uranium- and nitric acid-containing wastewater by electrocatalytic oxidation according to claim 1, characterized in that, In step S1, the uranium-containing nitric acid waste liquid includes: distillation residue, organic phase alkaline washing liquid, denitrification tail gas scrubbing liquid, and hydrogen reduction tail gas bubbling water.

4. The method for removing organic matter from uranium- and nitric acid-containing wastewater by electrocatalytic oxidation according to claim 1, characterized in that, In step S22, the laundry wastewater is treated by submerged ultrafiltration before being transported to the mixing tank, and the concentrated water from the membrane filtration comes from the membrane treatment ultrafiltration and nanofiltration system.

5. The method for removing organic matter from uranium- and nitric acid-containing wastewater by electrocatalytic oxidation according to claim 1, characterized in that, Step S4 includes the following steps: S41. Waste liquid with COD below 100 mg / L is transported to a flocculation sedimentation tank for collection; S42. Add flocculant to aggregate the flocculent material, press it into a filter cake using a filter press, and collect the filtrate in a filtrate receiving tank. S43. Adjust the pH of the filtrate to 6 and transfer it to the evaporation concentration system and membrane treatment system for deep uranium removal.

6. The method for removing organic matter from uranium- and nitric acid-containing wastewater by electrocatalytic oxidation according to claim 5, characterized in that, In step S42, the filter cake is loaded into drums and transported to the uranium-containing solid waste treatment system for processing.

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