A wastewater treatment method and system for extracting hafnium from a zirconium oxychloride solution

Abstract

The present application relates to a kind of hafnium extraction wastewater treatment method and processing system of zirconium oxychloride solution, and it relates to the field of wastewater recycling, it includes to the hafnium extraction wastewater is heated and separated and is removed oil, separation entrainment organic phase;Again through adsorption resin column adsorption removal residual extractant;Phosphate is added to the deoiled water phase, and residual zirconium, hafnium in wastewater is in situ generated zirconium / hafnium phosphate salt precipitate carrier;Subsequently, iron salt is added to carry out synergistic precipitation, and clear liquid is obtained by solid-liquid separation;Then adjust the pH of clear liquid and carry out neutralization and impurity removal, obtain neutral high-salt wastewater;Finally, through membrane concentration and evaporation crystallization treatment, obtain permeate, condensate and inorganic salt crystal.The present application can reduce the influence of residual organic matter on subsequent treatment, improve the removal stability of zirconium, hafnium, uranium, thorium and heavy metal impurities, and realize wastewater reduction and water resource reuse.

Description

Technical Field

[0001] This invention relates to the technical field of wastewater treatment, and in particular to a wastewater treatment method for extracting hafnium from zirconium oxychloride solution. Background Technology

[0002] The extraction of hafnium using zirconium oxychloride solution generates hafnium extraction wastewater. This type of wastewater is typically characterized by high acidity, high salinity, and complex composition. It may contain residual zirconium, hafnium, uranium, thorium, and heavy metal impurities such as lead, nickel, copper, and manganese. It may also contain small amounts of organic phase or residual extractant, making it difficult to treat.

[0003] In existing technologies, neutralization precipitation, coagulation precipitation, adsorption, membrane separation, or evaporation crystallization are commonly used to treat this type of wastewater. Among these, simple neutralization precipitation can remove some metal ions to a certain extent, but in the presence of zirconium, hafnium, uranium, thorium, and multiple heavy metals, problems such as incomplete precipitation, small flocs, poor solid-liquid separation, and fluctuations in effluent quality are prone to occur.

[0004] Furthermore, the organic phase and residual extractant entrained in the wastewater can affect the stable operation of subsequent coagulation sedimentation, membrane concentration, and evaporation crystallization processes, potentially leading to poor settling performance, membrane fouling, or fluctuations in condensate quality. Therefore, how to stably treat hafnium extraction wastewater using zirconium oxychloride solution to achieve stable removal of organic matter, metal impurities, and subsequent concentration and crystallization treatment is a technical problem that needs to be solved in this field. Summary of the Invention

[0005] To stabilize the treatment of hafnium extraction wastewater from zirconium oxychloride solution, this invention provides a method and system for treating such wastewater.

[0006] In a first aspect, the present invention provides a method for treating wastewater from hafnium extraction using zirconium oxychloride solution, employing the following technical solution: A method for treating wastewater from hafnium extraction using zirconium oxychloride solution includes the following steps: S1. The wastewater containing the extractant generated during the extraction of hafnium with zirconium oxychloride solution is heated and separated into an organic phase and an aqueous phase by standing. The aqueous phase is then passed into an adsorption and oil removal medium for adsorption and oil removal treatment to obtain an oil-free aqueous phase. S2. Add phosphate to the de-oiled aqueous phase and adjust the pH of the system so that the zirconium ions and / or hafnium ions remaining in the de-oiled aqueous phase react with phosphate ions to form a zirconium- and / or hafnium-containing phosphate precipitate carrier in situ. S3. Add iron salt to the system in which the phosphate precipitate carrier is formed, so that the phosphate precipitate carrier and the iron salt hydrolysis product form a composite precipitation system, and allow radioactive nuclides and heavy metal impurities in the wastewater to enter the composite precipitation system. After solid-liquid separation, the first precipitate and the clarified liquid are obtained. S4. Add alkali solution to the clarified liquid for neutralization and impurity removal, and obtain the second precipitate and neutral high-salt wastewater by solid-liquid separation; S5. The neutral high-salt wastewater is sent to a membrane concentration system for concentration treatment to obtain permeate and concentrate. The concentrate is then sent to an evaporation crystallization system for evaporation crystallization treatment to obtain condensate and inorganic salt crystals.

[0007] Preferably, in step S1, the wastewater is heated to 45℃~60℃ and then kept at that temperature for 1h~2h to allow the organic extractant in the wastewater to form an enriched organic phase and separate from the aqueous phase.

[0008] Preferably, in step S1, the adsorption and oil removal medium is a macroporous adsorption resin, which is used to remove the organic extractant remaining in the aqueous phase after heating and phase separation treatment.

[0009] Preferably, in step S2, after adding phosphate, the pH of the system is controlled to be 4.5-6.0 so that the zirconium ions and / or hafnium ions preferentially form zirconium- and / or hafnium-containing phosphate precipitates.

[0010] Preferably, in step S2, the phosphate is one or a combination of two of disodium hydrogen phosphate and trisodium phosphate; In step S3, the iron salt is one or a combination of two of polyferric sulfate and ferric chloride.

[0011] Preferably, in step S2, the amount of phosphate added is determined according to the total molar amount of residual zirconium ions and hafnium ions in the deoiled aqueous phase, so that the molar ratio of phosphate ions to the total molar ratio of zirconium ions and hafnium ions is 1.0:1 to 5.0:1.

[0012] Preferably, in step S3, the iron salt is added after the phosphate precipitate carrier is formed, and the mass ratio of the iron salt to the phosphate is 1:1 to 2:1. The radioactive nuclide is a uranium-series or thorium-series radioactive nuclide, and the heavy metal impurities include one or more of lead, cadmium, chromium, nickel, copper, and manganese.

[0013] Preferably, in step S4, sodium hydroxide solution is used to adjust the pH of the system to 7.5-8.5, so that the residual zirconium ions, hafnium ions and iron ions in the clarified liquid form hydroxide precipitates and are separated and removed; In step S5, the membrane concentration system is a disc tube reverse osmosis membrane system, the evaporation crystallization system is a mechanical vapor recompression evaporation crystallization system, and the permeate and / or condensate are recycled for use in the zirconium oxychloride solution extraction process water.

[0014] Secondly, the present invention provides a wastewater treatment system for hafnium extraction using zirconium oxychloride solution, employing the following technical solution: A wastewater treatment system for hafnium extraction using zirconium oxychloride solution includes the wastewater treatment method for hafnium extraction using zirconium oxychloride solution as described in the first aspect, and further includes: A thermal phase separation oil removal unit includes a phase separation reactor equipped with a heating and temperature control device, wherein the phase separation reactor is provided with an organic phase outlet and an aqueous phase outlet; An adsorption oil removal unit includes an adsorption resin column connected to the aqueous phase outlet; The in-situ carrier generation unit includes a first reactor connected to the outlet of the adsorption resin column, and the first reactor is connected to a phosphate dosing device. The co-precipitation unit includes a second reactor connected to the first reactor and a first solid-liquid separation device, wherein the second reactor is connected to an iron salt dosing device. The neutralization and impurity removal unit includes a third reactor connected to the clear liquid outlet of the first solid-liquid separation device and a second solid-liquid separation device, wherein the third reactor is connected to an alkali addition device; The membrane concentration and evaporation crystallization unit includes a membrane concentration component connected to the filtrate outlet of the second solid-liquid separation device, and an evaporation crystallizer connected to the concentrate outlet of the membrane concentration component.

[0015] Preferably, the first reactor and / or the second reactor are equipped with an online pH monitoring device, which is controlled and connected to the phosphate dosing device, the iron salt dosing device and / or the alkali dosing device; The membrane concentration module is a disc tube reverse osmosis membrane module, the evaporator crystallizer is a mechanical vapor recompression evaporator crystallizer, and the permeate outlet of the membrane concentration module and / or the condensate outlet of the evaporator crystallizer are connected to a reuse pipeline.

[0016] In summary, the present invention has at least one of the following beneficial technical effects: 1. This invention utilizes zirconium ions and / or hafnium ions extracted from hafnium wastewater using zirconium oxychloride solution as in-situ nucleation components, which react with added phosphate ions to form zirconium- and / or hafnium-containing phosphate precipitates. Without the need for additional special adsorbents or ion exchange resins, a precipitate carrier system suitable for the removal of radionuclides and heavy metal impurities can be constructed.

[0017] 2. The present invention adopts a stepwise treatment method of first adding phosphate to form a precipitation carrier and then adding iron salt to form a composite precipitation system. Compared with the simultaneous addition of phosphate and iron salt, it can improve the simultaneous removal effect of uranium series and thorium series radionuclides and heavy metal impurities.

[0018] 3. By reducing the content of organic extractants in wastewater through thermal phase separation and adsorption oil removal, the interference of organic extractants on precipitation reaction and membrane concentration system is reduced, which is beneficial to the stable operation of subsequent disc tube reverse osmosis membrane system.

[0019] 4. This invention combines membrane concentration with mechanical vapor recompression evaporation crystallization, which can reduce the volume and recover resources of high-salt wastewater. The resulting permeate and / or condensate can be reused in the extraction of hafnium process water using zirconium oxychloride solution, and the inorganic salt crystals can be recovered after drying.

[0020] 5. The process flow of this invention has good continuity and is suitable for the treatment of complex water quality in hafnium wastewater extracted by zirconium oxychloride solution, where there are residual organic extractants, high salinity, residual zirconium hafnium ions, radioactive nuclides and heavy metal impurities. Attached Figure Description

[0021] Figure 1 These are schematic diagrams of the system flow of Embodiments 5 and 6; Figure 2 This is a schematic diagram showing the location and flow of the thermal phase separation oil removal unit and the adsorption oil removal unit; Figure 3 This is a schematic diagram of the in-situ carrier generation unit process; Figure 4 This is a schematic diagram of the process flow for the co-precipitation unit and the neutralization and impurity removal unit; Figure 5 This is a schematic diagram of the membrane concentration and evaporation crystallization unit process.

[0022] Explanation of reference numerals in the attached drawings: 100, Wastewater treatment system; 110, Thermal phase separation oil removal unit; 111, Phase separation reactor; 112, Heating and temperature control device; 113, Organic phase outlet; 114, Aqueous phase outlet; 120, Adsorption oil removal unit; 121, Adsorption resin column; 130, In-situ carrier generation unit; 131, First reactor; 132, Phosphate dosing device; 140, Co-precipitation unit; 141, Second reactor; 142, First solid-liquid separation device; 143, Iron salt dosing device; 150, Neutralization and impurity removal unit; 151, Third reactor; 152, Second solid-liquid separation device; 153, Alkali dosing device; 160, Membrane concentration and evaporation crystallization unit; 161, Membrane concentration module; 162, Evaporation crystallizer; 163, Permeate outlet; 164, Concentrate outlet; 165, Condensate outlet; 166, Reuse pipeline. Detailed Implementation

[0023] The following is in conjunction with the appendix Figure 1 The technical solutions in the embodiments of the present invention are clearly and completely described herein. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] The present invention will be further described below with reference to specific embodiments. It should be understood that the following embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Without departing from the concept of the present invention, conventional adjustments made by those skilled in the art to the type of reagent, dosage, reaction time, membrane concentration factor, and evaporation crystallization operating parameters should all fall within the scope of protection of the present invention.

[0025] The wastewater treated in this invention is high-salt wastewater containing extractant generated during the extraction of hafnium using zirconium oxychloride solution. This type of wastewater typically contains residual organic extractant, chloride salts, sulfate or nitrate ions, zirconium ions, hafnium ions, and metallic impurities such as iron, lead, nickel, copper, and manganese, and may also contain uranium- or thorium-series radionuclides. Since a certain amount of zirconium and / or hafnium ions remain in the wastewater, this invention utilizes these residual zirconium and / or hafnium ions to generate a zirconium- and / or hafnium-containing phosphate precipitate carrier in situ with phosphate ions. Then, by subsequently adding iron salts to form a composite precipitation system, the synergistic removal of radionuclides and heavy metal impurities is achieved.

[0026] Table 1. Steps and preferred control conditions of the method of the present invention In one specific embodiment, the method of the present invention includes the following steps.

[0027] S1. Thermal phase separation and adsorption oil removal: The hafnium wastewater extracted with zirconium oxychloride solution is fed into a phase separation reactor and heated to 45-70°C. The mixture is kept at this temperature and allowed to stand for 0.5-3 hours to allow the organic phase entrained in the wastewater to float and separate. After separating the lower aqueous phase, it is passed into an adsorption column packed with macroporous adsorption resin. The empty bed flow rate is controlled at 1-6 BV / h to obtain the de-oiled aqueous phase.

[0028] S2. In-situ generation of zirconium / hafnium phosphate precipitate carrier: Add phosphate solution to the deoiled aqueous phase and adjust the pH of the system to 4.0-6.5 so that the residual zirconium ions and hafnium ions in the wastewater react with phosphate ions to form a zirconium / hafnium phosphate precipitate carrier in situ.

[0029] S3. Co-precipitation of iron salts: After the zirconium / hafnium phosphate precipitate carrier is formed, iron salts are added to the system, and the mixture is stirred rapidly for 15-40 minutes. Then, it is stirred at low speed for 5-30 minutes to flocculate. The clear liquid is obtained by solid-liquid separation.

[0030] S4. Neutralization and impurity removal: Add alkaline solution to the clarified liquid to adjust the pH to 7.0-9.0, continue the reaction for 10-40 minutes, and then perform solid-liquid separation to obtain neutral high-salt wastewater.

[0031] S5. Membrane concentration and evaporation crystallization: The neutral high-salt wastewater is fed into a membrane concentration system to obtain permeate and concentrate; the concentrate enters an evaporation crystallization system to obtain condensate and inorganic salt crystals.

[0032] Example 1 1000L of hafnium wastewater was extracted with zirconium oxychloride solution. The initial pH was 2.1, COD was 1035mg / L, and petroleum and extractant residues were 246mg / L. The wastewater was then fed into a phase-separation reactor equipped with a heating and temperature control device, heated to 55℃, and held at that temperature for 1.5h. The upper enriched organic phase was separated, and the lower aqueous phase was collected.

[0033] The lower aqueous phase was passed through an adsorption column packed with macroporous adsorption resin, and the empty bed flow rate was controlled at 3 BV / h to obtain a de-oiled aqueous phase. Testing showed that the residual petroleum hydrocarbons and extractant in the de-oiled aqueous phase decreased to 18 mg / L, and the COD decreased to 765 mg / L.

[0034] Add disodium hydrogen phosphate solution to the deoiled aqueous phase and adjust the pH of the system to 5.2 with sodium hydroxide solution; control the molar ratio of phosphate ions to Zr and Hf to be 2.5:1, stir for 20 min to allow the residual zirconium and hafnium to react with phosphate and form a zirconium / hafnium phosphate precipitate carrier in situ.

[0035] Subsequently, polyferric sulfate was added to the system, controlling the mass ratio of polyferric sulfate to phosphate at 1.5:1. The mixture was stirred at 180 rpm for 25 min, followed by flocculation and maturation at 60 rpm for 15 min. Solid-liquid separation yielded a clear liquid. A 10%–20% sodium hydroxide solution was added to the clear liquid to adjust the pH to 8.0. After reacting for 20 min, solid-liquid separation was performed to obtain neutral, high-salt wastewater.

[0036] The neutral, high-salt wastewater is fed into a disc-tube reverse osmosis membrane system for concentration treatment. The operating pressure is controlled at 6.5 MPa, and the concentration factor is 4 times, yielding permeate and concentrate. The permeate has a COD of 42 mg / L and petroleum content of less than 1 mg / L, and can be reused in the zirconium oxychloride extraction process for hafnium. The concentrate is fed into a mechanical vapor recompression evaporator crystallizer to obtain condensate and inorganic salt crystals.

[0037] Example 2 This embodiment is basically the same as Example 1, except that: the Zr content in the raw water is 200-230 mg / L, and the Hf content is 28-36 mg / L; the molar ratio of phosphate ions to the total Zr and Hf is controlled at 2.3:1, and the mass ratio of polyferric sulfate to phosphate is 1.4:1. After treatment, Zr, Hf, U, Th, and heavy metal impurities are all significantly reduced.

[0038] Example 3 This embodiment is basically the same as Example 1, except that the mass ratio of polyferric sulfate to phosphate is adjusted to 1.2:1, and the rapid stirring reaction time is extended to 30 min. Under these conditions, the in-situ formed zirconium / hafnium phosphate precipitate support can still provide adsorption, complexation, and co-precipitation sites for uranium, thorium, and heavy metals.

[0039] Example 4 This embodiment is basically the same as Embodiment 1, except that: the raw water is hafnium extraction wastewater with high salinity, containing 2-3 g / L of NaCl; the thermal phase separation temperature is adjusted to 58℃, the empty bed flow rate of the resin column is adjusted to 2.5 BV / h, the molar ratio of phosphate ions to Zr and Hf is controlled at 2.6:1, and the mass dosage ratio of polyferric sulfate to phosphate is 1.6:1. After treatment, the main metallic impurities in the wastewater can still be effectively removed.

[0040] Example 5 Reference Figures 1 to 5 This embodiment provides a wastewater treatment system for the extraction of hafnium from zirconium oxychloride solution. The wastewater treatment system 100 is used to implement the above-described wastewater treatment method for the extraction of hafnium from zirconium oxychloride solution. The wastewater treatment system 100 includes a thermal phase separation oil removal unit 110, an adsorption oil removal unit 120, an in-situ carrier generation unit 130, a co-precipitation unit 140, a neutralization and impurity removal unit 150, and a membrane concentration and evaporation crystallization unit 160, which are connected sequentially along the wastewater flow direction.

[0041] The thermal phase separation oil removal unit 110 includes a phase separation reactor 111 equipped with a heating and temperature control device 112. The phase separation reactor 111 is provided with an organic phase outlet 113 and an aqueous phase outlet 114. The organic phase outlet 113 is used to discharge the organic phase that has been heated and allowed to stand before floating and separating, and the aqueous phase outlet 114 is used to output the aqueous phase after phase separation.

[0042] The adsorption oil removal unit 120 includes an adsorption resin column 121 connected to the aqueous phase outlet 114. After phase separation, the aqueous phase is further desorbed by the adsorption resin column 121 to remove residual organic phase and extractant, resulting in an oil-free aqueous phase.

[0043] The in-situ carrier generation unit 130 includes a first reactor 131 connected to the outlet of the adsorption resin column 121, and the first reactor 131 is connected to a phosphate dosing device 132. The phosphate dosing device 132 is used to add a phosphate solution into the first reactor 131, so that the residual zirconium and hafnium in the deoiled aqueous phase react with phosphate ions to generate a zirconium / hafnium phosphate precipitate carrier in situ.

[0044] The co-precipitation unit 140 includes a second reactor 141 connected to the first reactor 131 and a first solid-liquid separation device 142. The second reactor 141 is connected to an iron salt dosing device 143. The iron salt dosing device 143 is used to add iron salt to the second reactor 141, so that the zirconium / hafnium phosphate precipitate carrier and the iron salt co-form a composite floc, which is then separated by the first solid-liquid separation device 142 to obtain clear liquid and sludge.

[0045] The neutralization and impurity removal unit 150 includes a third reactor 151 connected to the clarified liquid outlet of the first solid-liquid separation device 142 and a second solid-liquid separation device 152. The third reactor 151 is connected to an alkali addition device 153. The alkali addition device 153 is used to add alkali solution to the third reactor 151 to adjust the clarified liquid output from the first solid-liquid separation device 142 to neutral or weakly alkaline, and then separate it through the second solid-liquid separation device 152 to obtain filtrate.

[0046] The membrane concentration and evaporation crystallization unit 160 includes a membrane concentration module 161 connected to the filtrate outlet of the second solid-liquid separation device 152, and an evaporation crystallizer 162 connected to the concentrate outlet 164 of the membrane concentration module 161. The membrane concentration module 161 is used to concentrate the filtrate output from the second solid-liquid separation device 152 to obtain permeate and concentrate; the evaporation crystallizer 162 is used to evaporate and crystallize the concentrate to obtain condensate and inorganic salt crystals.

[0047] The thermal phase separation oil removal unit 110, adsorption oil removal unit 120, in-situ carrier generation unit 130, synergistic precipitation unit 140, neutralization and impurity removal unit 150, and membrane concentration and evaporation crystallization unit 160 are connected in sequence, enabling wastewater to be continuously treated in the order of organic phase pre-removal, residual organic matter adsorption, metal impurity precipitation removal, neutralization and impurity removal, and concentration and crystallization. The system has a clear structure and well-defined functions for each treatment unit, which helps improve the continuity and stability of the wastewater treatment process.

[0048] The phase-separation reactor 111, equipped with a heating and temperature control device 112, promotes the separation of organic phases entrained in the wastewater. The adsorption resin column 121 further removes residual extractant and organic matter, thereby reducing the adverse effects of organic matter on subsequent precipitation, solid-liquid separation, and membrane concentration processes. The coordinated use of the first reactor 131, phosphate dosing device 132, second reactor 141, iron salt dosing device 143, and first solid-liquid separation device 142 is beneficial for improving the removal efficiency of zirconium, hafnium, uranium, thorium, and heavy metal impurities, and for improving floc settling and solid-liquid separation performance.

[0049] The neutralization and impurity removal unit 150 can further adjust the pH of the clarified liquid after co-precipitation and remove residual impurities, making the wastewater entering the membrane concentration module 161 more stable. The membrane concentration module 161, used in conjunction with the evaporator crystallizer 162, can achieve wastewater reduction treatment and obtain reusable water and inorganic salt crystals, which is beneficial to reducing the amount of wastewater discharged.

[0050] Example 6 Reference Figures 1 to 5 Based on Example 5, an online pH monitoring device is installed in the first reactor 131 and / or the second reactor 141. The online pH monitoring device is controlled and connected to the phosphate dosing device 132, the iron salt dosing device 143 and / or the alkali dosing device 153 to adjust the dosage of phosphate, iron salt and / or alkali according to the pH change of the reaction system.

[0051] Furthermore, the membrane concentration unit 161 is a disc-tube reverse osmosis membrane unit, and the evaporator crystallizer 162 is a mechanical vapor recompression evaporator crystallizer 162. The permeate outlet 163 of the membrane concentration unit 161 and / or the condensate outlet 165 of the evaporator crystallizer 162 are connected to a reuse pipeline 166, which is used to reuse the permeate and / or condensate in the zirconium oxychloride solution extraction hafnium production process or other production water replenishment processes.

[0052] An online pH monitoring device is installed in the first reactor 131 and / or the second reactor 141 and is controlled and connected to the phosphate dosing device 132, the iron salt dosing device 143 and / or the alkali dosing device 153. This device can adjust the amount of reagent added according to the pH change of the reaction system, improve the accuracy of reagent dosing control, and reduce the fluctuation of treatment effect caused by excessive or insufficient reagent.

[0053] The membrane concentration module 161 adopts a disc-tube reverse osmosis membrane module, which is beneficial for the concentration treatment of wastewater with high salt and high pollution load. The evaporator crystallizer 162 adopts a mechanical vapor recompression evaporator crystallizer 162, which helps to reduce evaporation energy consumption. The permeate outlet 163 of the membrane concentration module 161 and / or the condensate outlet 165 of the evaporator crystallizer 162 are connected to the reuse pipeline 166, which enables the permeate and / or condensate to be reused in the production process, thereby improving water resource utilization.

[0054] Table 2 Main Components and Functions of Wastewater Treatment System Table 3 Main process parameters of Examples 1-4 Table 4 Average treatment effect of Example 1 Example test results The test results of the five parallel water samples in Example 1 before and after treatment are shown in Table 5.

[0055] Table 5-1 Results of pretreatment tests on five parallel water samples from Example 1 Table 5-2 Detection results of five parallel water samples after treatment in Example 1 Table 6. Overall Removal Effects of Examples 1-4 Comparative Example To illustrate the effects of thermal phase separation and adsorption oil removal, in-situ generation of zirconium / hafnium phosphate precipitate carrier, and synergistic precipitation of iron salts in this invention, comparative examples 1 to 4 were set up. Except for the differences listed in the table below, the raw water composition and other treatment conditions of the comparative examples were the same as those in Example 1.

[0056] Table 7 Comparative Examples of Process Differences Table 8. Comparison of removal rates between Example 1 and the comparative example. As shown in Table 8, compared with the comparative example, Example 1, which simultaneously employs thermal phase separation and adsorption oil removal, in-situ generation of zirconium / hafnium phosphate precipitate carrier and iron salt synergistic precipitation, can significantly improve the removal rate of Zr, Hf, U, Th and heavy metal ions.

[0057] Specifically, Comparative Example 1 only underwent neutralization treatment, resulting in insufficient precipitate carrier and weak capture capacity for uranium, thorium, and heavy metals; Comparative Example 2 did not add iron salt, resulting in insufficient formation of composite flocs and lower sedimentation and synergistic removal effects compared to Example 1; Comparative Example 3 did not undergo deoiling treatment, and the residual organic phase affected precipitation flocculation and solid-liquid separation; Comparative Example 4, after changing the order of chemical addition, resulted in insufficient formation of phosphate precipitate carrier, leading to a decrease in overall treatment effect.

[0058] Table 9. Effluent quality during membrane concentration and evaporation crystallization stages. In summary, this invention improves the removal efficiency of radionuclides and heavy metal impurities by pre-removing organic phases from wastewater, then utilizing residual zirconium and hafnium to form phosphate precipitation carriers in situ, and further synergistically forming composite flocs with iron salts, while reducing the pollution risk of subsequent membrane concentration and evaporation crystallization units.

[0059] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. All equivalent substitutions, parameter adjustments, or process combinations made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for treating wastewater from hafnium extraction using zirconium oxychloride solution, characterized in that: Includes the following steps: S1. The wastewater containing the extractant generated during the extraction of hafnium with zirconium oxychloride solution is heated and separated into an organic phase and an aqueous phase by standing. The aqueous phase is then passed into an adsorption and oil removal medium for adsorption and oil removal treatment to obtain an oil-free aqueous phase. S2. Add phosphate to the de-oiled aqueous phase and adjust the pH of the system so that the zirconium ions and / or hafnium ions remaining in the de-oiled aqueous phase react with phosphate ions to form a zirconium- and / or hafnium-containing phosphate precipitate carrier in situ. S3. Add iron salt to the system in which the phosphate precipitate carrier is formed, so that the phosphate precipitate carrier and the iron salt hydrolysis product form a composite precipitation system, and allow radioactive nuclides and heavy metal impurities in the wastewater to enter the composite precipitation system. After solid-liquid separation, the first precipitate and the clarified liquid are obtained. S4. Add alkali solution to the clarified liquid for neutralization and impurity removal, and obtain the second precipitate and neutral high-salt wastewater by solid-liquid separation; S5. The neutral high-salt wastewater is sent to a membrane concentration system for concentration treatment to obtain permeate and concentrate. The concentrate is then sent to an evaporation crystallization system for evaporation crystallization treatment to obtain condensate and inorganic salt crystals.

2. The wastewater treatment method for hafnium extraction using zirconium oxychloride solution according to claim 1, characterized in that: In step S1, the wastewater containing the extractant is heated to 45°C to 60°C and then kept at that temperature for 1 to 2 hours to allow the organic extractant in the wastewater to accumulate and form an organic phase, which is then separated from the aqueous phase.

3. The wastewater treatment method for hafnium extraction using zirconium oxychloride solution according to claim 2, characterized in that: In step S1, the adsorption and oil removal medium is a macroporous adsorption resin, which is used to remove the organic extractant remaining in the aqueous phase after heating and phase separation treatment.

4. The wastewater treatment method for hafnium extraction using zirconium oxychloride solution according to claim 1, characterized in that: In step S2, after adding phosphate, the pH of the system is controlled to be 4.5-6.0 so that the zirconium ions and / or hafnium ions preferentially form zirconium- and / or hafnium-containing phosphate precipitates.

5. The wastewater treatment method for hafnium extraction using zirconium oxychloride solution according to claim 4, characterized in that: In step S2, the phosphate is one or a combination of two of disodium hydrogen phosphate and trisodium phosphate. In step S3, the iron salt is one or a combination of two of polyferric sulfate and ferric chloride.

6. The wastewater treatment method for hafnium extraction using zirconium oxychloride solution according to claim 5, characterized in that: In step S2, the amount of phosphate added is determined according to the total molar amount of residual zirconium ions and hafnium ions in the deoiled aqueous phase, so that the molar ratio of phosphate ions to the total molar ratio of zirconium ions and hafnium ions is 1.0:1 to 5.0:

1.

7. The wastewater treatment method for hafnium extraction using zirconium oxychloride solution according to claim 6, characterized in that: In step S3, the iron salt is added after the phosphate precipitate carrier is formed, and the mass ratio of the iron salt to the phosphate is 1:1 to 2:

1. The radioactive nuclide is a uranium-series or thorium-series radioactive nuclide, and the heavy metal impurities include one or more of lead, cadmium, chromium, nickel, copper, and manganese.

8. The wastewater treatment method for hafnium extraction using zirconium oxychloride solution according to claim 1, characterized in that: In step S4, sodium hydroxide solution is used to adjust the pH of the system to 7.5-8.5, so that the residual zirconium ions, hafnium ions and iron ions in the clarified liquid form hydroxide precipitates and are separated and removed. In step S5, the membrane concentration system is a disc tube reverse osmosis membrane system, the evaporation crystallization system is a mechanical vapor recompression evaporation crystallization system, and the permeate and / or condensate are recycled for use in the zirconium oxychloride solution extraction process water.

9. A wastewater treatment system for implementing the wastewater treatment method according to any one of claims 1 to 8, wherein hafnium is extracted with zirconium oxychloride solution, characterized in that: The thermal phase separation oil removal unit includes a phase separation reactor equipped with a heating and temperature control device, and the phase separation reactor is provided with an organic phase outlet and an aqueous phase outlet; An adsorption oil removal unit includes an adsorption resin column connected to the aqueous phase outlet; The in-situ carrier generation unit includes a first reactor connected to the outlet of the adsorption resin column, and the first reactor is connected to a phosphate dosing device. The co-precipitation unit includes a second reactor connected to the first reactor and a first solid-liquid separation device, wherein the second reactor is connected to an iron salt dosing device. The neutralization and impurity removal unit includes a third reactor connected to the clear liquid outlet of the first solid-liquid separation device and a second solid-liquid separation device, wherein the third reactor is connected to an alkali addition device; The membrane concentration and evaporation crystallization unit includes a membrane concentration component connected to the filtrate outlet of the second solid-liquid separation device, and an evaporation crystallizer connected to the concentrate outlet of the membrane concentration component.

10. The wastewater treatment system for hafnium extraction using zirconium oxychloride solution according to claim 9, characterized in that: The first reactor and / or the second reactor are equipped with an online pH monitoring device, which is controlled to be connected to the phosphate dosing device, the iron salt dosing device and / or the alkali dosing device; The membrane concentration module is a disc tube reverse osmosis membrane module, the evaporator crystallizer is a mechanical vapor recompression evaporator crystallizer, and the permeate outlet of the membrane concentration module and / or the condensate outlet of the evaporator crystallizer are connected to a reuse pipeline.

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