A method for recovering heavy metal ions from strongly acidic nuclear wastewater

Abstract

The invention discloses a method for recovering heavy metal ions from strongly acidic nuclear waste water, comprising the following steps: A. adjusting the acidity of the strongly acidic nuclear waste water and heating it, then adding oxalic acid and / or sodium oxalate to carry out a precipitation reaction; B. adding acrylic polymer monomers and thermal initiators to carry out polymerization reaction, and then filtering; C. adding sodium sulfate to carry out double salt precipitation, and then adding a photoinitiator to perform photopolymerization to obtain a liquid to be extracted; D. adding a diamide pod ether extractant to the liquid to be extracted to carry out an extraction reaction, and liquid-liquid separation after the reaction is completed. The invention first solidifies heavy metal ions such as thorium, nickel, and cobalt through high-temperature precipitation of oxalic acid / sodium oxalate to reduce the metal ion concentration in the solution system, and then extracts and separates heavy metals, lanthanide elements, and precious metals, thereby significantly improving the removal rate and extraction effect of heavy metals and overcoming the shortcomings of the prior art.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear waste water purification and treatment, and in particular to a method for recovering heavy metal ions from strongly acidic nuclear waste water. Background Art

[0002] In the nuclear industry, the treatment of nuclear wastewater has always been a key task. Nuclear wastewater contains a variety of radioactive elements, such as 90 Sr. 137 Cs, 60 Co. 239 Pu, etc. The main methods for removing radioactive elements from nuclear wastewater include evaporation concentration, adsorption / ion exchange, chemical precipitation, extraction, biological treatment, etc. Actinides and lanthanides in nuclear wastewater have great application value. At present, lanthanides in nuclear wastewater are mainly recovered by solvent extraction. N, N, N', N'-tetraoctyl-3-oxoglutaramide (TODGA) extractant is widely used to extract some heavy metals, lanthanides and precious metals. Its disadvantage is that the extractant is prone to phase separation in a system with strong acid or excessive metal ion concentration. In response to this problem, the inventor proposed a method for extracting metal ions in a strong acid system (CN116555568A). This method stabilizes metal ion chelates to avoid the dissociation of metal ion chelates in an environment with excessive acidity, thereby enabling the extraction rate to reach more than 40%. However, for the case where the metal ion concentration is too high, the extraction efficiency of this method is low. At the same time, the increase in pH during the extraction process causes the extraction effect of the extractant to drop significantly. Therefore, it still needs to be improved. Summary of the invention

[0003] The purpose of the present invention is to provide a method for recovering heavy metal ions from strongly acidic nuclear waste water in view of the above-mentioned problems. The present invention first solidifies heavy metal ions such as thorium, nickel, and cobalt by high-temperature precipitation of oxalic acid / sodium oxalate to reduce the metal ion concentration in the solution system, and then extracts and separates heavy metals, lanthanides and precious metals, thereby significantly improving the removal rate and extraction effect of heavy metals and overcoming the shortcomings of the prior art.

[0004] The technical solution adopted by the present invention is as follows: A method for recovering heavy metal ions from strongly acidic nuclear waste water comprises the following steps:

[0005] A. Adjust the acidity of the strongly acidic nuclear wastewater to 2.0-3.0 mol / L, heat the nuclear wastewater to above 60°C, and then add oxalic acid and / or sodium oxalate to carry out precipitation reaction;

[0006] B. After the precipitation reaction is completed, adding acrylic polymer monomer and thermal initiator to the nuclear waste water in step A to carry out polymerization reaction, cooling and standing after the polymerization reaction, and then filtering to obtain filtered strongly acidic nuclear waste water;

[0007] C. Adding sodium sulfate to the filtered strongly acidic nuclear wastewater to precipitate double salts, and then adding a photoinitiator to initiate polymerization of the remaining acrylic polymer monomers to form a colloid by light irradiation. After the reaction is completed, a liquid to be extracted is obtained;

[0008] D. Add a bisamide pod ether extractant to the liquid to be extracted, mix and perform extraction reaction, and separate the liquid after the reaction is completed.

[0009] Furthermore, the amount of oxalic acid or / and sodium oxalate added is 0.7-1.2 times the total molar amount of thorium, nickel, and cobalt ions in the strongly acidic nuclear wastewater, for example, it can be 0.7 times, 0.8 times, 0.9 times, 1.0 times, 1.2 times, etc. According to the characteristics of oxalic acid / sodium oxalate precipitating metal ions, under high temperature conditions, it preferentially precipitates heavy metal ions such as thorium, nickel, and cobalt, and begins to precipitate heavy metal ions such as rare earth after excess, so its addition amount should not be too much, and it is more appropriate within the above range, otherwise it will increase the content of radioactive elements in the solid waste and affect the post-treatment of the solid waste.

[0010] Furthermore, the acrylic polymer monomer is selected from at least one of hydroxyethyl acrylate, acrylamide, acrylic acid and its salts, and methacrylic acid and its salts.

[0011] Furthermore, the amount of the acrylic polymer monomer added is 100-300g / 1000L, for example, 100g / 1000L, 120g / 1000L, 150g / 1000L, 300g / 1000L, etc. The acrylic polymer monomer is mainly used for flocculating oxalate precipitation, which helps to filter and remove oxalate precipitation. The amount of acrylic polymer monomer added should not be too much. Too much will not only increase the cost of the agent, but also carry more heavy metal ions and increase the content of radioactive elements in the solid waste. It is more appropriate to be within the above range.

[0012] Furthermore, the thermal initiator is selected from at least one of sodium persulfate, potassium persulfate, azobisisobutylamidine hydrochloride, and azobisisobutylimidazoline hydrochloride.

[0013] Furthermore, the amount of the thermal initiator added is 20-50 g / 1000L, for example, 20 g / 1000L, 25 g / 1000L, 30 g / 1000L, 45 g / 1000L, 50 g / 1000L, etc.

[0014] Furthermore, the photoinitiator is selected from at least one of photoinitiator 2959, 4-hydroxybenzophenone, 4-(2-hydroxyethyl)-oxyfluorenone, 1-hydroxy-cyclohexyl-phenyl ketone, and 4-(2-hydroxyethyl)-oxybenzophenone.

[0015] Furthermore, the amount of photoinitiator added is 2-10g / 1000L, for example, it can be 2g / 1000L, 3g / 1000L, 5g / 1000L, 8g / 1000L, 10g / 1000L, etc. The photoinitiator is mainly used to initiate the remaining unpolymerized acrylic monomer, so the amount added should not be too much, and it is more appropriate to be within the above range.

[0016] Further, the amount of sodium sulfate added is 10-50g / 1000L. For example, it can be 10g / 1000L, 20g / 1000L, 30g / 1000L, 40g / 1000L, 50g / 1000L, etc. The main function of sodium sulfate is to increase the content of suspended matter in the filtered nuclear wastewater by double salt precipitation, so as to facilitate the adsorption of colloids formed by the polymerization of residual acrylic monomers. It is not only convenient for the removal of residual colloids, but also convenient for constructing a relatively stable colloid carrier in the wastewater system, which is convenient for the enrichment of heavy metal ions (especially rare earth ions), and is conducive to improving the extraction effect of subsequent extractants. However, the double salt precipitation method is also easy to precipitate impurity metal ions such as calcium and magnesium and affect the extraction effect. Therefore, the amount of sodium sulfate added is not easy to be too much and needs to be controlled within the above range.

[0017] Furthermore, the bisamide pod ether extractant is selected from one of N,N,N',N'-tetraoctyl-3-oxoglutaramide, Me-TODGA, DODDDGA, DMDDDGA or DMDDDGA.

[0018] Furthermore, the addition amount of the bisamide pod ether extractant is 0.4-0.8 mol / L, for example, it can be 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.8 mol / L, etc.

[0019] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0020] 1. The present invention solidifies heavy metal ions such as thorium, nickel, and cobalt by high-temperature precipitation of oxalic acid / sodium oxalate (the acidity is adjusted to a higher level to facilitate the better precipitation of these heavy metal ions by oxalic acid / sodium oxalate, avoid the consumption of oxalate ions by impurity metal ions such as calcium, magnesium, and aluminum in the wastewater system, and facilitate the construction of a strong acidic wastewater environment, which is beneficial to the subsequent extraction and separation of radioactive heavy metal ions). Since the formed precipitate particles are small and difficult to filter and separate, the residual heat of the high-temperature precipitation is used to form a colloid through the polymerization of acrylic acid to adsorb the oxalic acid precipitate, which is not only conducive to the subsequent removal of the oxalate precipitate by filtering, but also when the temperature of the nuclear wastewater is reduced, the oxalic acid precipitate is prevented from redissolving, thereby ensuring the effect of the oxalic acid precipitation;

[0021] 2. By carrying out sulfate double salt precipitation on the filtered nuclear wastewater and continuing to initiate polymerization of acrylic acid monomers dissolved in water, it is convenient to remove the remaining colloids, and it is also convenient to construct a relatively stable colloid carrier in the wastewater system, which is convenient for enriching heavy metal ions (especially rare earth ions), thereby improving the extraction effect of subsequent extractants;

[0022] 3. The present invention not only significantly reduces the amount of subsequent bisamide pod ether extractant added, but also significantly improves the removal rate of radioactive heavy metal ions by performing oxalic acid precipitation + acrylic acid polymerization treatment on strongly acidic nuclear wastewater, so that the radioactive heavy metal ions are mainly enriched in the extraction organic phase, thereby improving the extraction effect and reducing the subsequent extraction process cost. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] Wastewater 1: Nuclear wastewater 1 generated by a certain unit has the following main component concentrations: radioactivity 2103Bq / LA; suspended solids (SS): 16.2mg / L; total amount of thorium, nickel and cobalt ions: 1.0mmol / L; chemical oxygen demand (COD): 18.3mg / L; ammonia nitrogen content: 0.4mg / L: fluoride: 4.3mg / L, pH value is less than 2.

[0025] Wastewater 2: Nuclear wastewater 2 generated by a certain unit has the following main component concentrations: radioactivity 2611Bq / LA; suspended solids (SS): 22.3mg / L; total amount of thorium, nickel and cobalt ions: 1.6mmol / L; chemical oxygen demand (COD): 20.7mg / L; ammonia nitrogen content: 0.6mg / L: fluoride: 5.0mg / L, pH value is less than 2.

[0026] Wastewater 3: Nuclear wastewater 3 generated by a certain unit has the following main component concentrations: radioactivity 1887Bq / LA; suspended solids (SS): 17.4mg / L; total amount of thorium, nickel and cobalt ions: 0.8mmol / L; chemical oxygen demand (COD): 16.2mg / L; ammonia nitrogen content: 0.3mg / L: fluoride: 3.5mg / L, pH value is less than 2.

[0027] Example 1

[0028] A method for recovering heavy metal ions from strongly acidic nuclear wastewater comprises the following steps:

[0029] S1. Place 1000L of wastewater 1 in a heatable container with a stirrer, adjust the acidity of the strongly acidic nuclear wastewater to 2.5mol / L with hydrochloric acid, heat the wastewater 1 to 80°C, add 103g of sodium oxalate to the wastewater 1, stir evenly, and keep warm for 10min;

[0030] S2. After the standing is completed, 124 g of hydroxyethyl acrylate and 21 g of sodium persulfate are added to the container in time, stirred evenly, and then kept warm and stood for 20 min;

[0031] S3, after the wastewater 1 is cooled to room temperature, the wastewater 1 is filtered through a tubular inorganic hydrophilic oleophobic membrane (membrane pore size 100 nm, porosity 50%) to obtain the filtered wastewater 1, and the filtrate is dried and treated as hazardous solid waste;

[0032] S4, add 12g of sodium sulfate to the filtered wastewater 1 for double salt precipitation, mix well and let stand for 10min, then add 4g of photoinitiator 2959, irradiate the wastewater with LED lamp for 3min, after the reaction is completed, stir and let stand to obtain the extract;

[0033] S5. The liquid to be extracted is mixed with 0.6 mol / L N,N,N',N'-tetraoctyl-3-oxoglutaramide extractant. The extraction time is 30 min and the extraction temperature is 35° C. After the reaction is completed, the liquid-liquid separation is performed to obtain an organic phase rich in metal ions and an extraction waste liquid.

[0034] In the above-mentioned extraction and separation process, sodium oxalate can be replaced by oxalic acid, hydroxyethyl acrylate can be replaced by acrylamide, acrylic acid and its salts, methacrylic acid and its salts, etc., the thermal initiator can be replaced by potassium persulfate, azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, etc., and the photoinitiator 2959 can be replaced by 4-hydroxybenzophenone, 4-(2-hydroxyethyl)-oxyfluorenone, 1-hydroxy-cyclohexyl-phenyl ketone, 4-(2-hydroxyethyl)-oxybenzophenone, etc. These replaceable substances have similar properties and can achieve similar technical effects in this embodiment. Therefore, the technical effect after replacement is obvious.

[0035] In this embodiment, the radioactive activity of the solid waste obtained after treatment is less than 200 Bq / LA, the radioactive activity of the extracted waste liquid is less than 100 Bq / LA, the suspended solids (SS) is less than 6.0 mg / L, the total amount of thorium, nickel and cobalt ions is less than 0.05 mmol / L, the chemical oxygen demand (COD) is less than 5.5 mg / L, the ammonia nitrogen content is less than 0.2 mg / L, the fluoride is less than 1.0 mg / L, the pH value is less than 1, and the radioactive element removal rate is greater than 90%.

[0036] Example 2

[0037] A method for recovering heavy metal ions from strongly acidic nuclear wastewater comprises the following steps:

[0038] S1. Place 1000L of wastewater 2 in a heatable container with a stirrer, adjust the acidity of the strongly acidic nuclear wastewater to 2.8mol / L with hydrochloric acid, heat the wastewater 2 to 80°C, add 141g of sodium oxalate to the wastewater 2, stir evenly, and keep warm for 10min;

[0039] S2. After the standing is completed, 154 g of hydroxyethyl acrylate and 29 g of sodium persulfate are added to the container in time, stirred evenly, and then kept warm and stood for 20 min;

[0040] S3, after the wastewater 2 is cooled to room temperature, the wastewater 2 is filtered through a tubular inorganic hydrophilic oleophobic membrane (membrane pore size 100 nm, porosity 50%) to obtain the filtered wastewater 2, and the filtrate is dried and treated as hazardous solid waste;

[0041] S4, add 15g of sodium sulfate to the filtered wastewater 2 for double salt precipitation, mix well and let stand for 10min, then add 5g of photoinitiator 2959, irradiate the wastewater with LED light for 3min, after the reaction is completed, stir and let stand to obtain the extract;

[0042] S5. Mix the liquid to be extracted with 0.4 mol / L N,N,N',N'-tetraoctyl-3-oxoglutaramide extractant, extract for 30 min at a temperature of 35°C. After the reaction is completed, separate the liquid and obtain an organic phase rich in metal ions and an extraction waste liquid.

[0043] In this embodiment, the radioactive activity of the solid waste obtained after treatment is less than 200 Bq / LA, the radioactive activity of the extracted waste liquid is less than 100 Bq / LA, the suspended solids (SS) is less than 6.0 mg / L, the total amount of thorium, nickel and cobalt ions is less than 0.05 mmol / L, the chemical oxygen demand (COD) is less than 5.5 mg / L, the ammonia nitrogen content is less than 0.2 mg / L, the fluoride is less than 1.0 mg / L, the pH value is less than 1, and the radioactive element removal rate is greater than 90%.

[0044] Example 3

[0045] A method for recovering heavy metal ions from strongly acidic nuclear wastewater comprises the following steps:

[0046] S1. Place 1000L of wastewater 3 in a heatable container with a stirrer, adjust the acidity of the strongly acidic nuclear wastewater to 2.1 mol / L with hydrochloric acid, heat the wastewater 3 to 80°C, add 90g of sodium oxalate to the wastewater 3, stir evenly, and keep warm for 10 minutes;

[0047] S2. After the standing is completed, 110 g of hydroxyethyl acrylate and 20 g of sodium persulfate are added to the container in time, stirred evenly, and then kept warm and stood for 20 min;

[0048] S3, after the wastewater 3 is cooled to room temperature, the wastewater 3 is filtered through a tubular inorganic hydrophilic oleophobic membrane (membrane pore size 100 nm, porosity 50%) to obtain the filtered wastewater 3, and the filtrate is dried and treated as hazardous solid waste;

[0049] S4, add 10g of sodium sulfate to the filtered wastewater 3 for double salt precipitation, mix well and let stand for 10min, then add 3g of photoinitiator 2959, irradiate the wastewater with LED light for 3min, after the reaction is completed, stir and let stand to obtain the extract;

[0050] S5. Mix the liquid to be extracted with 0.6 mol / L N,N,N',N'-tetraoctyl-3-oxoglutaramide extractant, extract for 30 min at a temperature of 30° C. After the reaction is completed, separate the liquid and obtain an organic phase rich in metal ions and an extraction waste liquid.

[0051] In this embodiment, the radioactive activity of the solid waste obtained after treatment is less than 200 Bq / LA, the radioactive activity of the extracted waste liquid is less than 100 Bq / LA, and the suspended solids (SS) is less than 6.0 mg / L; the total amount of thorium, nickel, and cobalt ions is less than 0.05 mmol / L, the chemical oxygen demand (COD) is less than 5.5 mg / L, the ammonia nitrogen content is less than 0.2 mg / L, the fluoride is less than 1.0 mg / L, the pH value is less than 1, and the radioactive element removal rate is greater than 90%.

[0052] Example 4

[0053] A method for recovering heavy metal ions from strongly acidic nuclear wastewater comprises the following steps:

[0054] S1. Place 1000L of wastewater 1 in a heatable container with a stirrer, adjust the acidity of the strongly acidic nuclear wastewater to 2.5mol / L with hydrochloric acid, heat the wastewater 1 to 80°C, add 90g of oxalic acid to the wastewater 1, stir evenly, and keep warm for 10min;

[0055] S2. After the standing is completed, 135 g acrylamide and 22 g sodium persulfate are added to the container in time, stirred evenly, and then kept warm and stood for 20 min;

[0056] S3, after the wastewater 1 is cooled to room temperature, the wastewater 1 is filtered through a tubular inorganic hydrophilic oleophobic membrane (membrane pore size 100 nm, porosity 50%) to obtain the filtered wastewater 1, and the filtrate is dried and treated as hazardous solid waste;

[0057] S4, add 12g of sodium sulfate to the filtered wastewater 1 for double salt precipitation, mix well and let stand for 10min, then add 4g of photoinitiator 2959, irradiate the wastewater with LED lamp for 3min, after the reaction is completed, stir and let stand to obtain the extract;

[0058] S5. The liquid to be extracted is mixed with 0.8 mol / L N,N,N',N'-tetraoctyl-3-oxoglutaramide extractant, the extraction time is 30 min, the extraction temperature is 40° C. After the reaction is completed, the liquid-liquid separation is performed to obtain an organic phase rich in metal ions and an extraction waste liquid.

[0059] In this embodiment, the radioactive activity of the solid waste obtained after treatment is less than 200 Bq / LA, the radioactive activity of the extracted waste liquid is less than 100 Bq / LA, the suspended solids (SS) is less than 6.0 mg / L, the total amount of thorium, nickel and cobalt ions is less than 0.05 mmol / L, the chemical oxygen demand (COD) is less than 5.5 mg / L, the ammonia nitrogen content is less than 0.2 mg / L, the fluoride is less than 1.0 mg / L, the pH value is less than 1, and the radioactive element removal rate is greater than 90%.

[0060] Comparative Example 1

[0061] Comparative Example 1 is the same as Example 1, except that the amount of sodium oxalate added is 250 g.

[0062] Test results: the radioactive activity of solid waste is greater than 800Bq / LA, the radioactive activity of extraction waste liquid is less than 100Bq / LA, the suspended solids (SS) is less than 6.0mg / L, the total amount of thorium, nickel and cobalt ions is less than 0.05mmol / L, the chemical oxygen demand (COD) is less than 5.5mg / L, the ammonia nitrogen content is less than 0.2mg / L, the fluoride is less than 1.0mg / L, the pH value is less than 1, and the radioactive element removal rate is greater than 90%.

[0063] This shows that excessive use of sodium oxalate will cause more radioactive heavy metal ions to enter the solid waste, which is not only not conducive to the subsequent treatment of the solid waste, but also will greatly reduce the total amount of subsequent radioactive heavy metal ion extraction.

[0064] Comparative Example 2

[0065] Comparative Example 2 is the same as Example 1, except that step S1 is not performed.

[0066] Test results: The radioactivity of solid waste is less than 200Bq / LA, in the extraction waste liquid, the radioactivity is greater than 800Bq / LA, the suspended solids (SS) is greater than 6.0mg / L, the total amount of thorium, nickel and cobalt ions is greater than 0.1mmol / L, the chemical oxygen demand (COD) is greater than 5.5mg / L, the ammonia nitrogen content is greater than 0.2mg / L, the fluoride is greater than 1.0mg / L, the pH value is 6.4, and the radioactive element removal rate is about 50%.

[0067] It can be seen that when high-temperature oxalic acid precipitation treatment is not carried out, the subsequent removal rate of radioactive heavy metal ions and the removal rate of metal ions are significantly deteriorated, indicating that high-temperature precipitation treatment of nuclear waste water with oxalic acid / sodium oxalate first can significantly improve the removal effect of metal ions.

[0068] Comparative Example 3

[0069] Comparative Example 3 is the same as Example 1, except that steps S2 and S3 are not performed, but the tubular inorganic hydrophilic oleophobic membrane is directly used for filtration.

[0070] Test results: the radioactive activity of solid waste is less than 200Bq / LA, the radioactive activity of extraction waste liquid is greater than 800Bq / LA, the suspended solids (SS) is greater than 10.0mg / L, the total amount of thorium, nickel and cobalt ions is greater than 0.1mmol / L, the chemical oxygen demand (COD) is greater than 10.0mg / L, the ammonia nitrogen content is greater than 0.2mg / L, the fluoride is greater than 1.0mg / L, the pH value is less than 1, and the removal rate of radioactive elements is about 60%.

[0071] It can be seen that when steps S2 and S3 are not performed, the subsequent removal rates of radioactive elements and metal ions, suspended matter, etc. are significantly deteriorated, indicating that performing steps S2 and S3 can improve the removal effect of metal ions. When the two are used in combination, the treatment effect of nuclear waste water is significantly improved.

[0072] Comparative Example 4

[0073] Comparative Example 4 is the same as Example 1, except that step S3 is not performed.

[0074] Experimental results: the radioactive activity of the solid waste obtained after treatment is less than 200Bq / LA, the radioactive activity of the extracted waste liquid is about 300Bq / LA, the suspended solids (SS) is less than 6.0mg / L, the total amount of thorium, nickel and cobalt ions is less than 0.05mmol / L, the chemical oxygen demand (COD) is less than 5.5mg / L, the ammonia nitrogen content is less than 0.2mg / L, the fluoride is less than 1.0mg / L, the pH value is less than, and the radioactive element removal rate is less than 90%.

[0075] It can be seen that when step S3 is not performed, the extraction effect of the subsequent extractant is significantly reduced, indicating that performing step S3 is helpful to improve the extraction effect of the extractant.

[0076] Comparative Example 5

[0077] Comparative Example 5 is the same as Example 1, except that the amount of hydroxyethyl acrylate added is 248 g, and the amount of sodium persulfate added is 40 g.

[0078] Test results: The radioactive activity of the solid waste obtained after treatment is about 300Bq / LA, the radioactive activity of the extracted waste liquid is less than 100Bq / LA, the suspended solids (SS) is less than 6.0mg / L, the total amount of thorium, nickel and cobalt ions is less than 0.05mmol / L, the chemical oxygen demand (COD) is less than 5.5mg / L, the ammonia nitrogen content is less than 0.2mg / L, the fluoride is less than 1.0mg / L, the pH value is less than 1, and the radioactive element removal rate is greater than 90%.

[0079] This shows that adding too much acrylic acid will increase the content of radioactive elements in solid waste.

[0080] Comparative Example 6

[0081] Comparative Example 6 is the same as Example 1, except that hydroxyethyl acrylate is replaced by a commonly used polyaluminium chloride flocculant, and the operation of adding a photoinitiator in step S3 is omitted.

[0082] Test results: The radioactive activity of the solid waste obtained after treatment is less than 200Bq / LA, the radioactive activity of the extracted waste liquid is greater than 300Bq / LA, the suspended solids (SS) is less than 6.0mg / L, the total amount of thorium, nickel and cobalt ions is less than 0.05mmol / L, the chemical oxygen demand (COD) is less than 5.5mg / L, the ammonia nitrogen content is less than 0.2mg / L, the fluoride is less than 1.0mg / L, the pH value is 6.0, and the radioactive element removal rate is greater than 80%.

[0083] It can be seen that the treatment effect of commonly used ordinary flocculants on nuclear waste water is not as good as the use effect of the acrylic acid of the present invention.

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for recovering heavy metal ions from strongly acidic nuclear wastewater, characterized in that: The steps include: A. Adjust the acidity of the strongly acidic nuclear waste water to 2.0-3.0 mol / L, heat the nuclear waste water to above 60° C., and then add oxalic acid and / or sodium oxalate to carry out precipitation reaction; the amount of oxalic acid and / or sodium oxalate added is 0.7-1.2 times the total molar amount of thorium, nickel and cobalt ions in the strongly acidic nuclear waste water; B. After the precipitation reaction is completed, adding acrylic polymer monomer and thermal initiator to the nuclear waste water of step A to carry out polymerization reaction, cooling and standing after the polymerization reaction, and then filtering to obtain filtered strongly acidic nuclear waste water; the amount of acrylic polymer monomer added is 100-300g / 1000L; C. Adding sodium sulfate to the filtered strongly acidic nuclear wastewater for double salt precipitation, the amount of sodium sulfate added is 10-50g / 1000L, and then adding a photoinitiator to initiate the polymerization of the remaining acrylic polymer monomers to form a colloid by light irradiation. After the reaction is completed, a liquid to be extracted is obtained; D. Add a bisamide pod ether extractant to the liquid to be extracted, mix and perform extraction reaction, and separate the liquid after the reaction is completed.

2. The method for recovering heavy metal ions from strongly acidic nuclear waste water according to claim 1, characterized in that: The acrylic polymer monomer is selected from at least one of hydroxyethyl acrylate, acrylamide, acrylic acid and its salts, and methacrylic acid and its salts.

3. The method for recovering heavy metal ions from strongly acidic nuclear waste water according to claim 1, characterized in that: The thermal initiator is selected from at least one of sodium persulfate, potassium persulfate, azobisisobutylamidine hydrochloride and azobisisobutylimidazoline hydrochloride, and the amount of the thermal initiator added is 20-50g / 1000L.

4. The method for recovering heavy metal ions from strongly acidic nuclear waste water according to claim 1, characterized in that: The photoinitiator is selected from at least one of photoinitiator 2959, 4-hydroxybenzophenone, 4-(2-hydroxyethyl)-oxyfluorenone, 1-hydroxy-cyclohexyl-phenyl ketone, and 4-(2-hydroxyethyl)-oxybenzophenone.

5. The method for recovering heavy metal ions from strongly acidic nuclear waste water according to claim 4, characterized in that: The added amount of the photoinitiator is 2-10 g / 1000L.

6. The method for recovering heavy metal ions from strongly acidic nuclear waste water according to claim 1, characterized in that: The bisamide pod ether extractant is selected from one of N,N,N',N'-tetraoctyl-3-oxoglutaramide, Me-TODGA, DODDDGA, DMDDDGA or DMDDDGA.

7. The method for recovering heavy metal ions from strongly acidic nuclear waste water according to claim 6, characterized in that: The addition amount of the bisamide pod ether extractant is 0.4-0.8 mol / L.