Uranium-containing wastewater treatment method

Abstract

The invention discloses a uranium-containing wastewater treatment method which comprises the following steps: step 1, heating a uranium solution to 70-90 DEG C, adding a preset mass of sodium sulfate and sodium persulfate, controlling the pH value of the solution in the reaction process to be 1.5-2.0, reacting for 2-4 hours, and then carrying out liquid-solid separation to obtain uranium-precipitated mother liquor and impurity-removed slag; step 2, adding sodium hydroxide into the uranium precipitation mother liquor, adjusting the pH value of the solution to 7-8, and filtering to obtain low-iron impurity sodium diuranate precipitate and uranium-containing wastewater; step 3, adding ferric salt and / or ferrous salt and sodium persulfate into the uranium-containing wastewater, controlling the pH value of the solution to be 2-5, heating to 60-95 DEG C, and reacting for 1-3 hours; and 4, the pH of the solution in the step 3 is continuously adjusted to 7-9, filtering separation is conducted after the reaction is conducted for 1-2 hours, uranium-containing iron slag and qualified wastewater are obtained, the uranium content in the qualified wastewater is lower than 0.1 ppm, and the COD value is lower than 100 ppm. The invention aims to realize purification of uranium and removal of COD in uranium-containing wastewater generated in the uranium extraction process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of uranium-containing wastewater treatment, and particularly relates to a uranium-containing wastewater treatment method. BACKGROUND

[0002] The wastewater generated in the process of monazite comprehensive utilization not only contains trace radioactive nuclide uranium, but also contains high concentration of COD. Moreover, since the uranium solution in the process of monazite comprehensive utilization usually contains high iron, and there is part of divalent iron in the uranium solution, if not purified, it will cause the iron in the sodium diuranate product to exceed the standard.

[0003] The existing uranium wastewater treatment method includes the mode of pre-treatment uranium removal-biological degradation / oxidation COD removal or oxidation COD removal-adsorption uranium removal, mainly aims at treating the produced wastewater, and has problems of long process, large equipment investment, easy secondary pollution and the like. Especially, for the complex uranium-containing wastewater with high chloride, high salt and high COD, it is difficult to effectively purify and remove COD by using the conventional Fenton and ozone oxidation method, and the electrochemical oxidation method usually causes a large amount of chlorine to deteriorate the production environment and poor economy.

[0004] The existing patent application with the patent number CN115547533A discloses a kind of uranium-containing wastewater deep purification system and its application, the system includes ultrafiltration circulation loop, filter pressing circulation loop and nanofiltration circulation loop;The ultrafiltration circulation loop and filter pressing circulation loop overlap in acidification basifier and flocculation settler that are connected in turn;The nanofiltration circulation loop includes two-stage nanofiltration circulation sub-circuit, three-stage nanofiltration circulation sub-circuit and four-stage nanofiltration circulation sub-circuit;Two-stage nanofiltration circulation sub-circuit and three-stage nanofiltration circulation sub-circuit overlap in a nanofiltration device, two-stage nanofiltration circulation sub-circuit and four-stage nanofiltration circulation sub-circuit overlap in a nanofiltration device, three-stage nanofiltration circulation sub-circuit and four-stage nanofiltration circulation sub-circuit overlap in a nanofiltration device;The ultrafiltration circulation loop is connected with the nanofiltration circulation loop.This purification system contains multiple circulation loops and numerous devices, and the structure is complex;And chemical reagent is frequently used in the treatment process, these reagents can effectively remove pollutants, but residual or improper use may cause the salt content of wastewater to increase, produce secondary pollution, and increase the burden of subsequent treatment;And the system produces various by-products, such as solid waste after filter pressing (which needs to be temporarily stored), ultrafiltration concentrate and nanofiltration concentrate which need to be recycled. These cycles may accumulate pollutants, increase the load of the system, and the disposal of solid waste does not explicitly state how to achieve "waste minimization". SUMMARY

[0005] The main purpose of the present application is to provide a uranium-containing wastewater treatment method, which aims to solve the technical problems of high treatment cost and difficulty in achieving standard discharge in the existing uranium-containing wastewater in the process of monazite comprehensive utilization.

[0006] To achieve the above object, the application provides a method for treating uranium-containing wastewater, comprising the following steps:

[0007] Step 1, heating the uranium solution to 70-90 DEG C, adding a preset mass of sodium sulfate and sodium persulfate, controlling the pH of the solution in the reaction process in the range of 1.5-2.0, and after the reaction for 2-4 hours, separating the liquid and solid to obtain a uranium precipitation mother liquor and a dregs of impurity removal, wherein the uranium solution is a uranium enrichment liquid obtained after processing of monazite ore by an integrated utilization process of monazite comprising alkali decomposition-acid leaching-resin uranium extraction.

[0008] Step 2, adding sodium hydroxide to the uranium precipitation mother liquor, adjusting the pH of the solution to 7-8, and after filtering, obtaining a sodium diuranate precipitate with low iron impurities and a uranium-containing wastewater;

[0009] Step 3, adding an iron salt and / or a ferrous salt and sodium persulfate to the uranium-containing wastewater, controlling the pH of the solution in the range of 2-5, heating to 60-95 DEG C, and reacting for 1-3 hours;

[0010] Step 4, continuously adjusting the pH of the solution in Step 3 to 7-9, filtering and separating after reacting for 1-2 hours, and obtaining a uranium-containing dregs and qualified wastewater, wherein the uranium content in the qualified wastewater is less than 0.1 ppm, and the COD value is less than 50 ppm.

[0011] Optionally, in Step 1, the uranium solution contains iron, and the mass of the added sodium sulfate is 1-2 times the mass of the iron.

[0012] Optionally, in Step 1, the mass / volume ratio of the added sodium persulfate to the uranium solution is 0.2-1 Kg / m 3 .

[0013] Optionally, in Step 3, the mass / volume ratio of the added iron salt and / or ferrous salt to the uranium-containing wastewater is 2-5 Kg / m 3 .

[0014] Optionally, in Step 3, the mass / volume ratio of the added sodium persulfate to the uranium-containing wastewater is 5-20 Kg / m 3 .

[0015] Optionally, in Step 3, the sodium persulfate and the iron salt and / or ferrous salt are added to the uranium-containing wastewater synchronously or step by step.

[0016] Optionally, in Step 3, the iron salt includes ferric sulfate and ferric chloride, and the ferrous salt includes ferrous sulfate and ferrous chloride.

[0017] Optionally, in Step 4, sodium hydroxide or sodium carbonate is used to adjust the pH of the solution to 7-9.

[0018] Beneficial effects:

[0019] The uranium-containing wastewater treatment method of the present application realizes the treatment of impurity iron and the pre-removal of COD by simultaneously adding sodium persulfate and impurity removal agent sodium sulfate in the uranium solution to cooperatively oxidize divalent iron in one step, filters to add sodium hydroxide to precipitate uranium to form sodium diuranate, and completes the uranium precipitation when the end point pH is 7-8, collects the low-iron impurity uranium product and the uranium-containing wastewater by filtration, and adds the uranium-containing wastewater to iron salt and / or ferrous salt and sodium persulfate to react for 1-3 hours, filters the uranium-containing iron residue and wastewater, so as to meet the discharge requirements of the radionuclide uranium and the COD index in the radioactive wastewater, and the uranium-containing iron residue can be returned to the acid dissolution process to realize the recycling of uranium resources. It can be seen that by embedding the COD removal process into the impurity removal and purification process of the uranium solution, the pre-removal of COD and the deep removal of iron impurities in the uranium product are realized, only the conventional operations such as heating, stirring and filtration are required, the deep removal of U and COD in the uranium-containing wastewater can also be realized, and it is suitable for bastnaesite mining and metallurgy high-chlorine and high-salt wastewater treatment. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is a flowchart of an embodiment of the uranium-containing wastewater treatment method of the present application.

[0021] The implementation, functional features and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0022] It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0023] Referring to Figure 1 , the present application provides a structural diagram of an embodiment of a uranium-containing wastewater treatment method, which comprises the following steps:

[0024] Step 1, heating the uranium solution to 70-90℃, and adding a predetermined amount of sodium sulfate and sodium persulfate, controlling the solution pH in the reaction process in the range of 1.5-2.0, and separating the liquid and solid after the reaction for 2-4 hours to obtain a uranium precipitation mother liquor and an impurity removal residue. The uranium solution refers to the uranium-rich liquid obtained after the bastnaesite ore is treated by the alkali decomposition-acid leaching process, and the main components thereof include uranium (which may exist in the form of uranyl ions (UO2+) or complex), high-concentration chloride ions, salt content (usually sodium chloride and other salts), and impurity iron.

[0025] Specifically, based on the fact that sodium sulfate and trivalent iron impurities can form a complex to realize the purification of impurities, in order to improve the impurity removal efficiency, sodium sulfate and sodium persulfate can be added to the uranium solution, wherein the mass of sodium sulfate is 1-2 times the mass of the iron contained therein, and the mass / volume ratio of sodium persulfate to the uranium solution is 0.2-1 Kg / m 3 ​, the reaction mechanism of sodium persulfate is: using sodium persulfate to remove the COD in the high-chlorine high-salt wastewater, at the same time, the divalent iron in the solution is oxidized into trivalent iron, so as to facilitate the reaction of sodium sulfate and impurity trivalent iron; at the same time, sodium persulfate can also be used to supplement sodium sulfate, which is convenient for iron removal reaction. In practical application, the COD value of the uranium solution is 1000-5000 ppm. Further, the step is to add sodium sulfate and a small amount of sodium persulfate in the uranium solution, and to stir and keep warm at 70-90°C and pH 1.5-2.0 for 2-4 hours, to realize the process of impurity iron precipitation and the pre-removal of COD at the same time, and to realize that the COD value of the uranium precipitation mother liquor is 30%-70% of the initial COD value of the uranium solution.

[0026] Further, in the actual reaction, the addition of sodium persulfate will make the pH of the solution lower, and thus in the process of gradually adding sodium persulfate and heating the uranium solution, the pH of the solution needs to be controlled in real time, if the pH of the solution is less than 1.5 after adding the preset amount of sodium persulfate, sodium hydroxide is added to control the pH of the solution in the reaction process in the range of 1.5-2.0.

[0027] Step 2, add sodium hydroxide to the uranium precipitation mother liquor until the solution, adjust the pH of the solution to 7-8, and filter to obtain a low-iron impurity sodium diuranate precipitate and a uranium-containing wastewater. Specifically, sodium hydroxide is added to precipitate uranium to form sodium diuranate, and the uranium precipitation can be completed when the final pH is 7-8. The content of uranium in the uranium product (sodium diuranate precipitate) is less than 0.1%.

[0028] The above steps 1 and 2 successfully precipitate and extract high-purity sodium diuranate product (the content of uranium is less than 0.1%) from the complex uranium-rich solution, realizing the recycling of uranium resources, not just simple treatment. While removing iron, 60%-70% of COD is pre-removed, greatly reducing the load of subsequent deep treatment.

[0029] Step 3, add iron salt and / or ferrous salt and sodium persulfate to the uranium-containing wastewater after the uranium product is precipitated, control the pH of the solution in the range of 2-5, heat to 60-95°C and react for 1-3 hours. Sodium persulfate is used to remove COD under weakly acidic or neutral conditions, and ion activation and thermal activation are used to improve the generation of sulfate radicals, thereby promoting the removal of COD. Preferably, the iron salt includes ferric sulfate and ferric chloride; the ferrous salt includes ferrous sulfate and ferrous chloride, and then one or two of ferrous chloride, ferrous sulfate, ferric sulfate and ferric chloride are added to the uranium-containing wastewater. More preferably, the addition of divalent iron can activate sodium persulfate to remove COD, and improve the efficiency of oxidation removal.

[0030] ​​Step 4, continue to adjust the pH of the solution in step 3 to 7-9, after 1-2 hours of reaction, filter separation, use the high affinity of uranium and iron, iron forms iron hydroxide to adsorb and remove uranium, to obtain uranium and iron slag and qualified wastewater (purified wastewater), wherein the uranium content in the qualified wastewater is less than 0.1 ppm, and the COD value is less than 100 ppm.

[0031] In the above steps 3 and 4, by adding iron salt and / or ferrous salt and a certain amount of sodium persulfate, the pH in the reaction process is adjusted to 2-5, after 1-3 hours of reaction, the pH is continuously adjusted to 7-9, and the uranium and iron slag and wastewater are separated by filtration. This process uses thermal activation and ion activation to strengthen the deep oxidation and decomposition of sodium persulfate to remove COD, and at the same time, iron forms iron hydroxide to adsorb and remove uranium as the pH increases, thereby realizing the deep removal of uranium and COD in the uranium-containing wastewater and achieving the discharge standard. The uranium-containing iron slag produced in step 4 can be returned to the acid dissolution process, thereby realizing the recycling of uranium resources and avoiding the accumulation of hazardous waste and reducing secondary pollution.

[0032] Main reaction equation:

[0033] ;

[0034] ;

[0035] The uranium-containing wastewater treatment method of the present application adds sodium persulfate in step 1 mainly for wastewater pretreatment, oxidizing iron impurities and pre-removing COD, laying the foundation for producing qualified uranium products and reducing the subsequent treatment load. In step 3, the added sodium persulfate is used to oxidize the residual COD under the promotion of thermal activation and ion activation, and finally realizes the removal of iron impurities in the uranium product and the purification of the uranium product, as well as the discharge standard of the monazite comprehensive utilization wastewater. Specifically, first, sodium persulfate and sodium sulfate are simultaneously added to the uranium-rich liquid to cooperatively treat the impurity iron (divalent iron) and COD in one step, and the sodium persulfate is used to oxidize the divalent iron to trivalent iron, and the sodium sulfate is used to realize the purification of iron impurities under the condition of pH: 1.5-2 by complex salt precipitation, and after filtering and separating the complex salt precipitate, sodium hydroxide is added to precipitate uranium to form low-iron impurity sodium diuranate, and when the end point pH is 7-8, the uranium precipitation is completed, and the uranium product and uranium-containing wastewater are collected by filtration. And by adding iron salt and / or ferrous salt and sodium persulfate in the uranium-containing wastewater, the COD in the wastewater is removed by oxidation of sodium persulfate under the condition of reaction temperature 60-95℃ and reaction pH 2-5 for 1-3 hours. Continue to gradually adjust the pH to 7-9, so that the iron in the wastewater forms iron hydroxide to adsorb and precipitate the uranium in the wastewater, and then filter and separate the uranium-containing iron slag and wastewater, finally realize the discharge standard, that is, the uranium content in the wastewater is less than 0.1 ppm, and the COD value is less than 100 ppm.

[0036] Further, the above method embeds the COD removal depth into the uranium extraction process through the innovative "two-step sodium persulfate addition" technology, simultaneously and efficiently achieving high-purity uranium recovery and deep purification of wastewater in a compact process. The final effluent meets the standards for uranium and COD indicators, and has multiple advantages such as simple process, low cost, strong adaptability, and resource recycling, especially suitable for solving the problem of complex high-salt high-chlorine uranium-containing wastewater generated in monazite mining.

[0037] Further, in order to better illustrate the effect of the uranium-containing wastewater treatment method in the present application, the following is described through specific examples.

[0038] Example 1

[0039] Step 1, add sodium sulfate and persulfate to the uranium solution to remove impurities, wherein the mass of sodium sulfate added is 2 times the mass of impurity iron, the mass / volume ratio of persulfate added to the uranium solution is 1 Kg / m 3 of persulfate, and the solution pH is controlled in the range of 1.5-2.0. Heat to 90°C and maintain temperature for 2 hours with stirring. After the reaction is completed, separate the liquid and solid, and collect the uranium precipitation mother liquor and the impurity removal residue, respectively. The COD of the uranium precipitation mother liquor is reduced from 3054 ppm in the uranium solution to 1084 ppm.

[0040] Step 2, continuously add sodium hydroxide to the uranium precipitation mother liquor until the filtrate pH is 7, and filter to obtain sodium diuranate product and uranium-containing wastewater. The uranium content in the product is less than 0.1%.

[0041] Step 3, add ferrous sulfate to the uranium-containing wastewater, the mass / volume ratio of ferrous sulfate to the uranium-containing wastewater is 3 Kg / m 3 , add persulfate to the uranium-containing wastewater, the mass / volume ratio of persulfate to the uranium-containing wastewater is 20 Kg / m 3 , control the reaction temperature to 85°C and the pH to 2.5, and react for 3 hours. After the reaction is completed, slowly adjust the pH to 8.5 by adding sodium hydroxide, and separate the uranium-containing iron residue and the wastewater by filtration. The COD in the wastewater is reduced to 33 ppm, and the uranium content is reduced to 0.051 ppm.

[0042] Example 2

[0043] Step 1, add sodium sulfate and persulfate to the uranium solution to remove impurities, wherein the mass of sodium sulfate added is 2 times the mass of impurity iron, the mass / volume ratio of persulfate added to the uranium solution is 0.8 Kg / m 3 of persulfate, and add sodium hydroxide to control the solution pH in the range of 1.5-2.0. Heat to 90°C and maintain temperature for 2 hours with stirring. After the reaction is completed, separate the liquid and solid, and collect the uranium precipitation mother liquor and the impurity removal residue, respectively. The COD of the uranium precipitation mother liquor is reduced from 3054 ppm in the uranium solution to 1682 ppm.

[0044] ​Step 2, the sedimentation of uranium mother liquor continuously adds sodium hydroxide until the filtrate pH is 7, and filtration is performed to obtain sodium diuranate product and uranium-containing wastewater. The uranium content in the product is less than 0.1%. The content is less than 0.1%.

[0045] Step 3, the uranium-containing wastewater is added with ferrous sulfate at a mass / volume ratio of 5 Kg / m 3 of the uranium-containing wastewater, and sodium persulfate at a mass / volume ratio of 20 Kg / m 3 of the uranium-containing wastewater, the reaction temperature is controlled at 85 ℃, the pH is 3.5, and after 3 hours of reaction, sodium hydroxide is added to slowly adjust the pH to 7.5, and then filtration is performed to separate the uranium-containing iron residue and wastewater. The COD in the wastewater is reduced to 10 ppm, and the uranium content is reduced to 0.042 ppm.

[0046] Example 3

[0047] Step 1, sodium sulfate and sodium persulfate are added to the uranium solution for impurity removal, 1.5 times the mass of the impurity iron is added as sodium sulfate, 0.2 Kg / m 3 of sodium persulfate is added to the uranium solution as sodium persulfate, and sodium hydroxide is added to control the solution pH in the range of 1.5-2.0, heated to 90 ℃ and temperature is maintained for 2 hours of stirring. After the reaction is completed, liquid-solid separation is performed, and the sedimentation of uranium mother liquor and impurity removal residue are collected. The COD of the sedimentation of uranium mother liquor is reduced from 1685 ppm in the uranium solution to 1239 ppm.

[0048] Step 2, the sedimentation of uranium mother liquor continuously adds sodium hydroxide until the filtrate pH is 7, and filtration is performed to obtain sodium diuranate product and uranium-containing wastewater. The uranium content in the product is less than 0.1%. The content is less than 0.1%.

[0049] Step 3, the uranium-containing wastewater is added with ferrous sulfate at a mass / volume ratio of 2 Kg / 1 m 3 of the uranium-containing wastewater, and sodium persulfate at a mass / volume ratio of 10 Kg / m 3 of the uranium-containing wastewater, the reaction temperature is controlled at 85 ℃, the pH is 5, and after 3 hours of reaction, sodium hydroxide is added to slowly adjust the pH to 9, and then filtration is performed to separate the uranium-containing iron residue and wastewater. The COD in the wastewater is reduced to 45 ppm, and the uranium content is reduced to 0.067 ppm.

[0050] Example 4

[0051] Step 1, sodium sulfate and sodium persulfate are added to the uranium solution for impurity removal, 2 times the mass of the impurity iron is added as sodium sulfate, 1 Kg / m 3sodium hydroxide to control the pH of the solution in the range of 1.5-2.0, heated to 90℃ and temperature conservation stirring for 2 hours. After the reaction, liquid and solid were separated, and the mother liquor of the precipitated uranium and the impurity removal residue were collected respectively. The COD of the mother liquor of the precipitated uranium was reduced from 2858 ppm in the uranium solution to 888 ppm.

[0052] Step 2, the mother liquor of the precipitated uranium was continuously added with sodium hydroxide until the pH of the filtrate was 7, and sodium diuranate product and uranium-containing wastewater were obtained by filtration. The uranium content in the uranium product was 0.82%. <0.1%.

[0053] Step 3, iron sulfate was added into the uranium-containing wastewater, the mass / volume ratio of the iron sulfate to the uranium-containing wastewater was 5 Kg / m 3 , and the mass / volume ratio of the sodium persulfate to the uranium-containing wastewater was 20 Kg / m 3 . After the reaction at 85℃ and pH 3.5 for 3 hours, the pH was slowly adjusted to 7.5 by adding sodium hydroxide, and the uranium-containing iron residue and wastewater were separated by filtration. The COD in the wastewater was reduced to 78 ppm, and the uranium content was reduced to 0.071 ppm.

[0054] Comparative Example 1

[0055] Step 1, sodium sulfate and sodium persulfate were added to the uranium solution for impurity removal, 2 times the mass of the impurity iron was added as sodium sulfate, no sodium persulfate was added, and sodium hydroxide was added to control the pH of the solution in the range of 1.5-2.0, heated to 90℃ and temperature conservation stirring for 2 hours. After the reaction, liquid and solid were separated, and the mother liquor of the precipitated uranium and the impurity removal residue were collected respectively. The COD of the mother liquor of the precipitated uranium was reduced from 3054 ppm in the uranium solution to 2956 ppm.

[0056] Step 2, the mother liquor of the precipitated uranium was continuously added with sodium hydroxide until the pH of the filtrate was 7, and sodium diuranate product and uranium-containing wastewater were obtained by filtration. The uranium content in the uranium product was 0.82%. <0.1%.

[0057] Step 3, only sodium persulfate was added into the uranium-containing wastewater, the mass / volume ratio of the sodium persulfate to the uranium-containing wastewater was 4 Kg / m 3 . After the reaction at 85℃ and pH 3.5 for 3 hours, the pH was slowly adjusted to 7.5 by adding sodium hydroxide, and the uranium-containing iron residue and wastewater were separated by filtration. The COD in the wastewater was reduced to 138 ppm, and the uranium content was reduced to 0.071 ppm.

[0058] Comparative Example 2

[0059] Step 1, sodium sulfate and sodium persulfate were added to the uranium solution for impurity removal, 2 times the mass of the impurity iron was added as sodium sulfate, and the mass / volume ratio of the sodium persulfate to the uranium solution was 0.5 Kg / m 3Sodium persulfate was added, and sodium hydroxide was added to adjust the pH of the solution to the range of 1.5-2.0. The solution was heated to 90°C and stirred for 2 hours. After the reaction, the liquid and solid were separated, and the uranium precipitate mother liquor was collected and impurities were removed. The COD of the uranium precipitate mother liquor decreased from 3865 ppm in the uranium solution to 1756 ppm.

[0060] Step 2: Sodium hydroxide is continuously added to the uranium precipitation mother liquor until the pH of the filtrate reaches 7. The filtrate is then filtered to obtain sodium diuranate product and uranium-containing wastewater. The uranium product contains... Content <0.1%.

[0061] Step 3: Add 5 kg / m³ of uranium-containing wastewater to the uranium-containing wastewater by mass-to-volume ratio. 3 Ferrous sulfate was used without adding sodium persulfate. The reaction temperature was controlled at 85℃ and the pH at 3.5. After reacting for 3 hours, sodium hydroxide was added to slowly adjust the pH to 7.5. Then, the uranium-containing iron slag and wastewater were separated by filtration. The COD in the wastewater was reduced to 1653 ppm, and the uranium content was reduced to 0.042 ppm.

[0062] The uranium content (less than 0.1 ppm) and COD value (<100 mg / L) in the final effluent of Examples 1-4 were significantly lower than those in Comparative Examples 1-2.

[0063] In Comparative Example 1, sodium persulfate was not added in step 1, resulting in poor COD pre-removal (the COD of the uranium precipitation mother liquor decreased only from 3054 ppm to 2956 ppm, almost unchanged) and poor uranium product quality (the final sodium diuranate product had a lower COD content). The iron content was as high as 0.82%, indicating that iron impurities were not effectively removed. It is evident that after adding sodium persulfate in step 1, the COD of the uranium precipitation mother liquor was significantly reduced, and the iron content of the uranium products was all below 0.1%. This suggests that adding sodium persulfate in step 1 not only pre-oxidized and degraded some of the COD, but also... Oxidized to This facilitates the removal of iron impurities through precipitation in the form of double salts, ensuring the purity of the final uranium product.

[0064] As can be seen from Examples 1-3, adding ferrous salt in step 3 improves the oxidation and removal of COD, resulting in a final COD level of less than 50 ppm in the wastewater. In Example 4, ferric sulfate was added in step 3, and the final COD level in the wastewater was reduced to 78 ppm. It can be seen that adding ferrous salt in step 3 can improve the oxidation and removal of COD, mainly due to the activation effect of ferrous ions on sodium persulfate, which improves the efficiency of sulfate free radical production.

[0065] In the comparative example 2, no sodium persulfate was added in step 3, only iron salt was added, and as a result, the COD was hardly removed (from 1756 ppm to 1653 ppm), which proves that the iron salt alone is ineffective for COD removal. It further proves that the advanced oxidation system of the present application using iron salt and sodium persulfate can effectively degrade refractory organic matter and achieve deep removal of COD. At the same time, the subsequently formed iron hydroxide colloid can also efficiently adsorb and precipitate residual uranium.

[0066] It should be noted that in this document, the terms "comprising", "including", or any other variant thereof are intended to cover a non-exclusive inclusion, so that a process, method, article, or system that comprises a list of elements does not only include those elements, but can also include other elements not expressly listed, or inherent to such process, method, article, or system. Without more limitations, the element defined by the statement "comprising a" does not exclude the presence of additional identical elements in the process, method, article, or system that includes the element.

[0067] The above-mentioned embodiment numbers of the present application are only for description, and do not represent the advantages and disadvantages of the embodiments.

[0068] The above is only the preferred embodiment of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation, or direct or indirect application in other related technical fields, which is made by using the content of the present application specification and drawings, is also included in the patent protection scope of the present application.

Claims

1. A method for treating uranium-containing wastewater, characterized in that, The method includes the following steps: Step 1: Heat the uranium solution to 70℃-90℃ and add sodium sulfate and sodium persulfate of a predetermined mass. Control the pH of the solution during the reaction process within the range of 1.5-2.

0. After the reaction is completed for 2-4 hours, liquid-solid separation is performed to obtain uranium precipitation mother liquor and impurity removal residue. The uranium solution is a uranium enrichment solution obtained by the comprehensive utilization process of monazite ore, which is alkali decomposition-acid leaching-resin uranium extraction. Step 2: Add sodium hydroxide to the uranium precipitation mother liquor to adjust the pH of the solution to 7-8, and after filtration, obtain sodium diuranate precipitate with low iron impurities and uranium-containing wastewater. Step 3: Add ferric salts and / or ferrous salts and sodium persulfate to the uranium-containing wastewater, control the pH of the solution in the range of 2-5, and heat to 60℃-95℃ for 1-3 hours. Step 4: Continue to adjust the pH of the solution from Step 3 to 7-9, react for 1-2 hours, then filter and separate to obtain uranium-containing iron slag and qualified wastewater. The uranium content in the qualified wastewater is less than 0.1 ppm, and the COD value is less than 100 ppm.

2. The uranium-containing wastewater purification method as described in claim 1, characterized in that, In step 1, the uranium solution contains iron, and the mass of sodium sulfate added is 1-2 times the mass of the iron.

3. The uranium-containing wastewater purification method as described in claim 1, characterized in that, In step 1, the mass-to-volume ratio of sodium persulfate to uranium solution is 0.2-1 kg / m³. 3 .

4. The method for treating uranium-containing wastewater as described in claim 1, characterized in that, In step 3, the added ferric salt and / or ferrous salt to uranium-containing wastewater have a mass-to-volume ratio of 2-5 kg / m³. 3 .

5. The uranium-containing wastewater treatment method as described in claim 4, characterized in that, In step 3, the mass-to-volume ratio of added sodium persulfate to uranium-containing wastewater is 5-20 kg / m³. 3 .

6. The method for treating uranium-containing wastewater as described in claim 4, characterized in that, In step 3, sodium persulfate is added to the uranium-containing wastewater simultaneously or in stages with ferric salts and / or ferrous salts.

7. The method for treating uranium-containing wastewater as described in claim 4, characterized in that, In step 3, the iron salts include ferric sulfate and ferric chloride; the ferrous salts include ferrous sulfate and ferrous chloride.

8. The method for treating uranium-containing wastewater as described in claim 1, characterized in that, In step 4, sodium hydroxide or sodium carbonate is used to adjust the pH of the solution to 7-9.

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