Method for treating uranium-containing wastewater by polymeric ferric sulfate to remove uranium in depth

Abstract

The method for treating uranium-containing wastewater by polymeric ferric sulfate to remove uranium deeply comprises the following steps: adding lime milk into a uranium removal tank of uranium-containing wastewater generated in uranium purification and blowing air to aerate; performing thickening filtration on the mixed liquid after aeration, landfilling the filter residue, and transferring the supernatant and the filtrate into a wastewater transfer tank; pressurizing the uranium-containing wastewater in the wastewater transfer tank and conveying it into an aeration tank, and opening a fan control opening to make the aeration uniform; adding polymeric ferric sulfate solution under the state of aeration and stirring and standing; performing thickening filtration on the liquid after standing, landfilling the filter residue, and transferring the supernatant and the filtrate into a tank-type discharge tank; detecting the treated uranium-containing wastewater in the tank-type discharge tank, directly discharging the liquid that is qualified in the detection, and repeatedly treating the liquid that is unqualified in the detection in the wastewater transfer tank until it is qualified and discharged. The process steps are simple, the control is convenient, the uranium concentration in the uranium-containing wastewater is up to the standard for discharge, and the method has great practical significance for protecting the ecological environment and realizing the social sustainable development.

Description

Technical Field

[0001] This invention relates to the field of uranium processing and fuel manufacturing technology, and in particular to a method for deep uranium removal from uranium-containing wastewater by treating polyferric sulfate. Background Technology

[0002] Uranium in uranium-containing wastewater poses a radiation hazard to humans, and its entry into drinking water and the food chain also has a significant impact on the environment. Therefore, treating uranium-containing wastewater generated during production or mining operations is crucial and necessary. Only wastewater that meets national emission standards can be discharged. Common methods for treating uranium-containing wastewater include physical methods, chemical precipitation, and biological uranium removal. Chemical precipitation primarily involves adding coagulants to co-precipitate the radioactive elements in the wastewater, or to coagulate them into fine, settleable particles. This is mainly because the solubility of radioactive nuclides in wastewater, such as phosphates, carbonates, and hydroxides, is low. Therefore, the addition of flocculants adsorbs the radioactive nuclides in the wastewater, producing flocculation and achieving removal, thus bringing the treated wastewater to the permissible discharge standards.

[0003] Existing methods for treating uranium-containing wastewater often require multiple steps, such as adding uranium removal agents, stirring, neutralization and precipitation, solid-liquid separation, and pH adjustment. For example, Chinese Patent Publication No. CN101597113A discloses a method for treating uranium-containing wastewater. Other methods involve multiple steps, such as pH adjustment, uranium removal agents, oxidants, alkali, and solid-liquid separation, as in Chinese Patent Publication No. CN105906099B, a method for treating rare-earth radioactive wastewater. Still others involve multiple steps, such as pH adjustment, neutralization and precipitation, and uranium removal through filtration, as in Chinese Patent Publication No. CN102930914A, a method for treating uranium-containing radioactive liquid. However, all of these methods suffer from complex procedures, difficulty in pH adjustment, and challenges in industrial-scale production. Therefore, how to achieve convenient adjustment, simple operation, and industrial-scale mass production after the safe and environmentally friendly upgrade and renovation of existing uranium purification production lines remains a pressing issue that needs to be addressed. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned shortcomings of the prior art and provide a method for deep uranium removal from uranium-containing wastewater by treating polyferric sulfate.

[0005] The technical solution of this invention is: a method for deep uranium removal from uranium-containing wastewater treated with polyferric sulfate, comprising the following steps: Step 1, Pretreatment of uranium-containing wastewater generated from uranium purification: The uranium content in the uranium-containing wastewater generated from uranium purification is 2-30 mg / L, and the nitric acid concentration is 0.12-0.22 mol / L. Lime slurry is added to the uranium removal tank of the uranium-containing wastewater. The solid content of the lime slurry is 40%-50%. The mixed liquid after adding lime slurry is aerated by a blower for 1-3 hours.

[0006] Step 2: The aerated mixed liquid is thickened by a thickener, and the bottom slurry is filtered into the first plate and frame filter. The filtered residue is sent to the tailings dam for landfill treatment. The supernatant after thickening and the filtrate from the plate and frame filter press are both sent to the wastewater transfer tank. The pH value and uranium content of the liquid in the wastewater transfer tank are measured.

[0007] Step 3: Pressurize and transport the uranium-containing wastewater from the wastewater transfer tank to the aeration tank. When the wastewater in the aeration tank reaches its rated volume, turn on the blower and open the air inlet of the aeration tank for ventilation. Control the opening of the air inlet of the aeration tank to ensure uniform aeration. Measure the pH value and uranium content of the uranium-containing wastewater.

[0008] Step 4: Slowly add polyferric sulfate solution to the aerated wastewater while stirring to ensure thorough mixing of the uranium-containing wastewater and the polyferric sulfate solution. After stirring, allow the mixture to stand and measure the pH value of the mixed liquid at 1h, 2h, 4h, 8h, and 24h.

[0009] Step 5: After standing, the mixed liquid is thickened by a thickener, and the bottom slurry is filtered into the second plate and frame filter. The filtered residue is sent to the tailings dam for landfill treatment. The supernatant after thickening and the filtrate from the plate and frame filter press are both sent into the trough discharge tank. The iron content in the filtered filtrate is measured.

[0010] Step six: Test the treated uranium-containing wastewater in the trough discharge tank. The uranium concentration in the wastewater is set to be ≤0.05 mg / L to be qualified. If the uranium concentration in the treated uranium-containing wastewater is ≤0.05 mg / L, it will be discharged into the trough. Otherwise, if the test is unqualified, the treated uranium-containing wastewater will be transferred to the wastewater transfer tank and steps four to six will be repeated.

[0011] A further technical solution of the present invention is: the pH value of the liquid in the wastewater transfer tank is 8-9, the uranium content is ≤0.3mg / L, and the iron content in the filtrate after filtration is 0.01-0.5 mg / L.

[0012] A further technical solution of the present invention is as follows: the concentration of polyferric sulfate in step three is 100 g / L, and the amount of polyferric sulfate added to the uranium-containing wastewater is 0.5–2.0 kg / m³. 3 The mixing time is 5-10 min, the stirring time is 1-3 h, and the pH value of the uranium-containing wastewater is controlled at 7-9.

[0013] A further technical solution of the present invention is that the filter cake particle size of the first plate and frame filter is 18-38 μm, and the filter cake particle size of the second plate and frame filter is 1-10 μm.

[0014] Compared with the prior art, the present invention has the following characteristics: This invention pretreats uranium-containing wastewater by using lime slurry for neutralization and aeration, followed by deep uranium removal using polyferric sulfate. After pretreatment and deep uranium removal, the uranium-containing wastewater is thickened and filtered using a plate and frame filter. This method only requires control of the final pH value, achieving the standard discharge of uranium concentration in uranium-containing wastewater in industrial uranium purification processes. It has advantages such as economy, stability, strong operability, and good industrial application.

[0015] The detailed structure of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating the uranium removal method of the present invention; Figure 2 This is a process flow diagram of the deep uranium removal process of the present invention. Detailed Implementation

[0017] Example 1, as Figure 1-2 As shown, a method for deep uranium removal from uranium-containing wastewater using polyferric sulfate includes the following steps: Step 1, Pretreatment of uranium-containing wastewater generated from uranium purification: The uranium-containing wastewater generated from uranium purification has a uranium content of 2.4 mg / L and a nitric acid concentration of 0.2 mol / L. Lime slurry is added to the uranium removal tank of the uranium-containing wastewater. The solid content of the lime slurry is 40% to 50%. The mixed liquid after adding lime slurry is aerated by a blower for 3 hours.

[0018] Step 2: The aerated mixed liquid is thickened by a thickener, and the bottom slurry is filtered into the first plate and frame filter. The filtered residue is sent to the tailings dam for landfill treatment. The supernatant after thickening and the filtrate from the plate and frame filter press are both sent to the wastewater transfer tank. The pH value of the liquid in the wastewater transfer tank is measured to be 9.2, the uranium content is 0.28 mg / L, and the particle size of the filter residue from the first plate and frame filter is 18 μm.

[0019] After the above-mentioned limestone neutralization and filtration, the uranium content in the uranium-containing wastewater is less than 0.3 mg / L. Since the uranium concentration in the liquid effluent discharged from the wastewater treatment facility does not exceed 50 μg / L, the uranium content in the uranium-containing wastewater still does not meet the discharge standards, and further deep uranium removal is required.

[0020] Step 3: Pressurize and transport the uranium-containing wastewater from the wastewater transfer tank to the aeration tank. When the wastewater in the aeration tank reaches its rated volume, turn on the blower and open the air inlet of the aeration tank for ventilation. Control the opening of the air inlet of the aeration tank to ensure uniform aeration.

[0021] Step 4: Slowly add polyferric sulfate solution to the aerated wastewater while stirring to ensure thorough mixing. After stirring, allow the mixture to stand, and measure the pH of the mixed liquid at 1 h, 2 h, 4 h, 8 h, and 24 h, recording the pH values ​​as 8.79, 8.74, 8.66, 8.1, and 7.63, respectively.

[0022] The concentration of the polyferric sulfate is 100 g / L, and the amount of polyferric sulfate added to the uranium-containing wastewater is 0.5 kg / m³. 3 The mixing time is 5–10 min, and the stirring time is 1–3 h.

[0023] Step 5: After settling, the mixed liquid is thickened using a thickener, and the bottom slurry is filtered through a second plate and frame filter press. The filtered residue is sent to a tailings dam for landfill disposal. The supernatant from the thickening process and the filtrate from the plate and frame filter press both enter a trough-type discharge tank. The filter residue from the second plate and frame filter press has a particle size of 10 μm, and the iron content in the filtrate is 0.37 mg / L.

[0024] Step six: The treated uranium-containing wastewater in the trough discharge tank is tested. The uranium concentration in the treated uranium-containing wastewater is 0.052 mg / L. The uranium content in the wastewater still exceeds 50 μg / L. Therefore, the treated uranium-containing wastewater is transferred to a wastewater transfer tank and steps four to six are repeated until the uranium content in the wastewater is lower than 0.05 mg / L, at which point it is discharged in the trough.

[0025] Example 2: A method for deep uranium removal from uranium-containing wastewater treated with polyferric sulfate, comprising the following steps: Step 1, Pretreatment of uranium-containing wastewater generated from uranium purification: The uranium content in the uranium-containing wastewater generated from uranium purification is 20.1 mg / L, and the nitric acid concentration is 0.12 mol / L. Lime slurry is added to the uranium removal tank of the uranium-containing wastewater. The solid content of the lime slurry is 40% to 50%. The mixed liquid after adding lime slurry is aerated by a blower for 2 hours.

[0026] Step 2: The aerated mixed liquid is thickened by a thickener, and the bottom slurry is filtered into the first plate and frame filter. The filtered residue is sent to the tailings dam for landfill treatment. The supernatant after thickening and the filtrate from the plate and frame filter press are both sent to the wastewater transfer tank. The pH value of the liquid in the wastewater transfer tank is measured to be 8.2, the uranium content is 0.269 mg / L, and the particle size of the filter residue from the first plate and frame filter is 30 μm.

[0027] After the above-mentioned limestone neutralization and filtration, the uranium content in the uranium-containing wastewater is less than 0.3 mg / L. Since the uranium concentration in the liquid effluent discharged from the wastewater treatment facility does not exceed 50 μg / L, the uranium content in the uranium-containing wastewater still does not meet the discharge standards, and further deep uranium removal is required.

[0028] Step 3: Pressurize and transport the uranium-containing wastewater from the wastewater transfer tank to the aeration tank. When the wastewater in the aeration tank reaches its rated volume, turn on the blower and open the air inlet of the aeration tank for ventilation. Control the opening of the air inlet of the aeration tank to ensure uniform aeration.

[0029] Step 4: Slowly add polyferric sulfate solution to the aerated wastewater while stirring to ensure thorough mixing. After stirring, allow the mixture to stand and measure the pH value of the liquid at 1h, 2h, 4h, 8h, and 24h, recording the pH values ​​as 7.9, 7.5, 7.42, 7.2, and 7.28, respectively.

[0030] The concentration of the polyferric sulfate is 100 g / L, and the amount of polyferric sulfate added to the uranium-containing wastewater is 2 kg / m³. 3 The mixing time is 5–10 min, and the stirring time is 1–3 h.

[0031] Step 5: After settling, the mixed liquid is thickened using a thickener, and the bottom slurry is filtered through a second plate and frame filter press. The filtered residue is sent to a tailings dam for landfill disposal. The supernatant from the thickening process and the filtrate from the plate and frame filter press both enter a trough-type discharge tank. The filter residue from the second plate and frame filter press has a particle size of 5 μm, and the iron content in the filtrate is 0.1 mg / L.

[0032] Step six: The treated uranium-containing wastewater in the trough discharge tank is tested. The uranium concentration in the treated uranium-containing wastewater is 0.036 mg / L, which meets the discharge standard for uranium-containing wastewater. The wastewater is then discharged into the trough.

[0033] Example 3: A method for deep uranium removal from uranium-containing wastewater treated with polyferric sulfate, comprising the following steps: Step 1, Pretreatment of uranium-containing wastewater generated from uranium purification: The uranium-containing wastewater generated from uranium purification has a uranium content of 30 mg / L and a nitric acid concentration of 0.22 mol / L. Lime slurry is added to the uranium removal tank of the uranium-containing wastewater. The solid content of the lime slurry is 40% to 50%. The mixed liquid after adding lime slurry is aerated by a blower for 1 hour.

[0034] Step 2: The aerated mixed liquid is thickened by a thickener, and the bottom slurry is filtered into the first plate and frame filter. The filtered residue is sent to the tailings dam for landfill treatment. The supernatant after thickening and the filtrate from the plate and frame filter press are both sent to the wastewater transfer tank. The pH value of the liquid in the wastewater transfer tank is measured to be 8.9, the uranium content is 0.225 mg / L, and the particle size of the filter residue from the first plate and frame filter is 38μm.

[0035] After the above-mentioned limestone neutralization and filtration, the uranium content in the uranium-containing wastewater is less than 0.3 mg / L. Since the uranium concentration in the liquid effluent discharged from the wastewater treatment facility does not exceed 50 μg / L, the uranium content in the uranium-containing wastewater still does not meet the discharge standards, and further deep uranium removal is required.

[0036] Step 3: Pressurize and transport the uranium-containing wastewater from the wastewater transfer tank to the aeration tank. When the wastewater in the aeration tank reaches its rated volume, turn on the blower and open the air inlet of the aeration tank for ventilation. Control the opening of the air inlet of the aeration tank to ensure uniform aeration.

[0037] Step 4: Slowly add polyferric sulfate solution to the aerated wastewater while stirring to ensure thorough mixing. After stirring, allow the mixture to stand, and measure the pH of the mixed liquid at 1 h, 2 h, 4 h, 8 h, and 24 h, recording the pH values ​​as 7.95, 7.65, 7.46, 7.69, and 7.57, respectively.

[0038] The concentration of the polyferric sulfate is 100 g / L, and the amount of polyferric sulfate added to the uranium-containing wastewater is 1.5 kg / m³. 3 The mixing time is 5–10 min, and the stirring time is 1–3 h.

[0039] Step 5: After settling, the mixed liquid is thickened using a thickener, and the bottom slurry is filtered through a second plate and frame filter press. The filtered residue is sent to a tailings dam for landfill disposal. The supernatant from the thickening process and the filtrate from the plate and frame filter press both enter a trough-type discharge tank. The filter residue from the second plate and frame filter press has a particle size of 1 μm, and the iron content in the filtrate is 0.02 mg / L.

[0040] Step six: The treated uranium-containing wastewater in the trough discharge tank is tested. The uranium concentration in the treated uranium-containing wastewater is 0.039 mg / L, which meets the discharge standard for uranium-containing wastewater. The wastewater is then discharged into the trough.

[0041] To further measure the impact of the above-mentioned treatment steps on industrial uranium-containing wastewater, the filter residue from step two of Example 1 was analyzed before being sent to the tailings dam for landfill disposal. The main components of the filter residue are shown in the table below: U（%） Fe (%) Ca (%) Mg (%) Ti (%) <![CDATA[SO4 2- (%)]]> Filter residue 0.054 9.57 11.75 0.41 0.21 12.82 Therefore, the above steps can achieve deep uranium removal treatment of industrial uranium-containing wastewater, realize low-uranium landfill in filter residue and the final uranium emission concentration is below 50 μg / L, which meets the standards for industrial uranium-containing wastewater discharge.

Claims

1. A method for deep uranium removal from uranium-containing wastewater treated with polyferric sulfate, characterized in that, Includes the following steps: Step 1, Pretreatment of uranium-containing wastewater generated from uranium purification: The uranium content in the uranium-containing wastewater generated from uranium purification is 2-30 mg / L, and the nitric acid concentration is 0.12-0.22 mol / L. Lime slurry is added to the uranium removal tank of the uranium-containing wastewater. The solid content of the lime slurry is 40%-50%. The mixed liquid after adding lime slurry is aerated by a blower for 1-3 hours. Step 2: The aerated mixed liquid is thickened by a thickener, and the bottom slurry is filtered through a first plate and frame filter press. The filtered residue is sent to the tailings dam for landfill treatment. The supernatant after thickening and the filtrate from the plate and frame filter press are both sent to the wastewater transfer tank. The pH value and uranium content of the liquid in the wastewater transfer tank are measured. The pH value of the liquid in the wastewater transfer tank is controlled at 8-9, the uranium content is controlled at ≤0.3mg / L, and the iron content in the filtered filtrate is controlled at 0.01-0.5 mg / L. Step 3: Pressurize and transport the uranium-containing wastewater from the wastewater transfer tank to the aeration tank. When the wastewater in the aeration tank reaches its rated volume, turn on the blower and open the air inlet of the aeration tank for ventilation. Control the opening of the air inlet of the aeration tank to ensure uniform aeration. Measure the pH value and uranium content of the uranium-containing wastewater. Step four: Slowly add polyferric sulfate solution to the uranium-containing wastewater while aerating, stirring continuously to ensure thorough mixing. The concentration of the polyferric sulfate is 100 g / L, and the amount of polyferric sulfate added to the uranium-containing wastewater is 0.5–2.0 kg / m³. 3 The mixing time is 5-10 min, the stirring time is 1-3 h, and the pH value of the uranium-containing wastewater is controlled at 7-9. After stirring, the mixture is allowed to stand, and the pH value of the mixed liquid is measured at 1h, 2h, 4h, 8h and 24h. Step 5: After standing, the mixed liquid is thickened by a thickener, and the bottom slurry is filtered into the second plate and frame filter. The filtered residue is sent to the tailings dam for landfill treatment. The supernatant after thickening and the filtrate from the plate and frame filter press are both sent into the trough discharge tank. The iron content in the filtered filtrate is measured. Step six: Test the treated uranium-containing wastewater in the trough discharge tank. The uranium concentration in the wastewater is set to be ≤0.05 mg / L to be qualified. If the uranium concentration in the treated uranium-containing wastewater is ≤0.05 mg / L, it will be discharged into the trough. Otherwise, if the test is unqualified, the treated uranium-containing wastewater will be transferred to the wastewater transfer tank and steps four to six will be repeated.

2. The method for deep uranium removal from uranium-containing wastewater treated with polyferric sulfate as described in claim 1, characterized in that: The filter cake particle size of the first plate and frame filter is 18–38 μm, and the filter cake particle size of the second plate and frame filter is 1–10 μm.

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