A method of treating uranium-containing wastewater

Abstract

The present application relates to a kind of methods for treating uranium-containing wastewater, comprising the following steps: adjusting the pH of uranium-containing wastewater to 4.5-5.5, to obtain pretreated wastewater;Ethanol and shewanella enrichment bacteria solution are added to the pretreated wastewater, the volume ratio of ethanol to pretreated wastewater is 1:100, sealed and placed, bioreduction for 2 days, to obtain bioreduction solution;The bioreduction solution is subjected to ultraviolet irradiation for 8-12 hours, and photochemical deep reduction is carried out, to obtain photochemical reduction solution;Solid-liquid separation is carried out on the photochemical reduction solution, to obtain standard effluent and uranium-containing precipitate.The process of the method of the present application does not require expensive chemical reagents throughout, and efficient remediation can be completed using ethanol and ultraviolet lamp, significantly reducing the treatment cost of uranium-containing wastewater.

Description

Technical Field

[0001] This invention relates to the field of nuclear wastewater purification and treatment technology, specifically a method for treating uranium-containing wastewater. Background Technology

[0002] The main methods for treating uranium-containing wastewater include physical methods such as adsorption, membrane separation, and evaporation concentration; chemical methods such as chemical precipitation and ion exchange; and biological methods such as microbial treatment technology and plant treatment technology. Adsorption is the most commonly used method for treating radioactive uranium-containing wastewater, with advantages such as wide availability of raw materials, low price, simple preparation methods, and good stability. However, the adsorbent has limitations in adsorption capacity. Membrane separation has advantages such as high purification coefficient, low energy consumption, and simple operating equipment and processes. However, the compatibility of membranes is very easily affected by environmental factors, resulting in poor stability. Evaporation is highly efficient, produces less wastewater, and has a high decontamination ratio, but it has disadvantages such as high cost, high energy consumption, and high safety risks. Chemical precipitation has advantages such as low cost, simple treatment equipment, and the ability to reduce most radioactive nuclides. However, it is easily affected by factors such as solution pH, ionic strength, reaction temperature, and time, has harsh operating conditions, and produces a large amount of sediment that can easily cause secondary pollution. Ion exchange can achieve good purification results, but ion exchange resins are easily interfered with by coexisting ions, and the cost is high. Plant treatment technology and microbial treatment have advantages such as low cost, environmental friendliness, and simple processes, but the treatment cycle is long. In summary, traditional methods for treating uranium-containing wastewater are limited by factors such as low diffusion kinetics, complex reaction conditions, low selectivity, and interference from coexisting ions, resulting in drawbacks such as high cost, poor treatment effect, and easy secondary pollution. Therefore, it is urgent to explore a new method for treating uranium-containing radioactive wastewater in an economical and efficient manner. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a method for treating uranium-containing wastewater, aiming to partially solve the problems existing in the prior art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a method for treating uranium-containing wastewater, comprising the following steps: The pH value of the uranium-containing wastewater was adjusted to 4.5-5.5 to obtain pretreated wastewater; Ethanol and Shewanella enrichment solution were added to the pretreated wastewater at a volume ratio of 1:100. The mixture was sealed and allowed to stand for 2 days for biological reduction to obtain a biologically reduced solution. The biological reducing solution was irradiated with ultraviolet light for 8–12 hours to perform photochemical deep reduction, thus obtaining a photochemical reducing solution. Solid-liquid separation was performed on the photochemical reducing solution to obtain qualified effluent and uranium-containing precipitate.

[0005] As a preferred technical solution, the concentration of the Shewanella enrichment solution is 1×10⁻⁶. 6 ~8×10 9 The dosage is CFU / mL, and the volume ratio of the added amount to the pretreated wastewater is 1:200.

[0006] As a preferred technical solution, under the conditions of pH 4.5-5.5 and the presence of ethanol, Shewanella bacteria can inhibit coexisting bacteria in wastewater by ≥90%, without the need for sterilization treatment.

[0007] As a preferred technical solution, the wavelength of ultraviolet light is 320–400 nm.

[0008] As a preferred technical solution, the uranium-containing wastewater is uranium-containing wastewater with an initial uranium concentration of 10-100 mg / L, and after treatment by the method, the uranium concentration in the effluent is ≤0.5 mg / L.

[0009] As a preferred technical solution, irradiating the biological reducing solution with ultraviolet light for 8–12 hours is replaced by exposing the biological reducing solution to direct sunlight outdoors for 48–72 hours.

[0010] As a preferred technical solution, the uranium-containing precipitate is UO2, and the leaching rate of UO2 after soaking for 48 hours is ≤1% within the pH range of 3-9 and temperature range of -10 to 60℃.

[0011] As a preferred technical solution, the method also includes a step of uranium recovery from uranium-containing precipitates: soaking the uranium-containing precipitates in 1 mol / L dilute nitric acid at 75°C for 1 to 2 hours, with a uranium recovery rate ≥90%.

[0012] As a preferred technical solution, when Ca in uranium-containing wastewater 2+ Concentration ≤100mg / L, CO3 2- When the concentration is ≤50mg / L, the uranium removal rate reaches over 92%.

[0013] As a preferred technical solution, ethanol is replaced with methanol or isopropanol, and the volume ratio of methanol or isopropanol to pretreated wastewater is 1:100.

[0014] Compared with the prior art, the technical solution of this application has the following beneficial effects: (1) This invention uses ethanol, methanol, or isopropanol as the electron donor (carbon source). Compared with traditional chemical reagents such as sodium acetate and lactate, ethanol is widely available, inexpensive, and easy to obtain, significantly reducing the cost of the reagent. The reaction is carried out at room temperature and pressure, requiring only a simple static container and an ultraviolet light source, without the need for high-pressure and high-temperature equipment, resulting in extremely low energy consumption. Shewanella has a highly efficient extracellular electron transfer capability, requiring only a small amount of bacterial culture to initiate the reaction, reducing the input of biological agents.

[0015] (2) Highly efficient “dual reduction” mechanism: This process cleverly combines microbial reduction and photochemical reduction. During the settling period, microorganisms reduce some soluble U(VI) to insoluble U(IV); subsequent ultraviolet irradiation utilizes photo-excited free radicals generated by ethanol to deeply reduce the remaining uranium, solving the problems of slow reaction rate of single biological methods or incompleteness of single chemical methods. The final product is chemically stable uranium dioxide (UO2), which is more difficult to oxidize and dissolve than simple bio-adsorption.

[0016] (3) Environmental friendliness and safety: Ethanol is a carbon source, and its metabolic products are mainly carbon dioxide and water, which are non-toxic and harmless; Shewanella is a common microorganism in the environment and will not cause invasion or damage to the ecosystem. Compared with the traditional chemical precipitation method, this method produces a relatively small volume and is easy to separate and dispose of in the future.

[0017] (4) Simple operation and strong adaptability: The entire process only includes three core steps: "adjusting pH - adding bacteria and letting stand - ultraviolet light". It does not require a complex pipeline system or precise automated control, and is easy to promote in remote mining areas or temporary work sites. Attached Figure Description

[0018] Figure 1 This invention provides a flowchart of a method for treating uranium-containing wastewater. Figure 1 ; Figure 2 This invention provides a flowchart of a method for treating uranium-containing wastewater. Figure 2 . Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Please see Figure 1-2 The present invention provides a method for treating uranium-containing wastewater, comprising the following steps: Step 1: Adjust the pH of the uranium-containing wastewater to 4.5-5.5 to obtain pretreated wastewater. Here, for acidic mining wastewater whose pH is already in the range of 4.0-6.0, the nitric acid adjustment step can be omitted.

[0021] Step 2: Add ethanol and Shewanella enriched bacterial solution to the pretreated wastewater at a volume ratio of 1:100. Seal and let stand for 2 days for biological reduction to obtain a biologically reduced solution. Here, pure Shewanella bacteria can be replaced with a mixed bacterial community containing Shewanella (e.g., enriched solution directly taken from uranium tailings pond sediment or anaerobic digested sludge). Instead of pure culture and isolation of the bacterial strain, simply add a sludge suspension that has undergone simple acclimation to the wastewater.

[0022] Step 3: Irradiate the biological reducing solution with ultraviolet light for 8-12 hours to carry out photochemical deep reduction and obtain the photochemical reducing solution.

[0023] Step 4: Perform solid-liquid separation on the photochemical reducing solution to obtain qualified effluent and uranium-containing precipitate.

[0024] Preferably, the concentration of the Shewanella enrichment solution is 1×10⁻⁶. 6 ~8×10 9 The dosage is CFU / mL, and the volume ratio of the added amount to the pretreated wastewater is 1:200.

[0025] Preferably, under conditions of pH 4.5-5.5 and the presence of ethanol, Shewanella bacteria exhibit an inhibition rate of ≥90% against coexisting bacteria in wastewater, eliminating the need for sterilization treatment.

[0026] Preferably, the wavelength of the ultraviolet light is 320–400 nm. More preferably, it is 365 nm; irradiation with 365 nm ultraviolet light for 24 hours results in a concentration of hydroxyl radicals generated by the photolysis of ethanol reaching 1.2 × 10⁻⁶. -4 mol / L can reduce the residual U(VI) concentration from 0.5 mg / L to below 0.01 mg / L.

[0027] Preferably, the uranium-containing wastewater has an initial uranium concentration of 10–100 mg / L, and after treatment by the method, the uranium concentration in the effluent is ≤0.5 mg / L.

[0028] Preferably, instead of irradiating the bioreduction solution with ultraviolet light for 8–12 hours, expose it to direct sunlight outdoors for 48–72 hours. After standing for 2 days, move the reaction vessel to a location with direct sunlight outdoors, utilizing the abundant ultraviolet wavelengths (UV-A / UV-B) in sunlight in conjunction with ethanol for a photochemical reaction. This completely eliminates power consumption and is suitable for remote uranium mining areas where power supply is difficult. Although the reaction rate may be slightly slower than artificial strong ultraviolet light, it can still meet emission standards under prolonged sunlight exposure.

[0029] Preferably, the uranium-containing precipitate is UO2, and the leaching rate of UO2 after soaking for 48 hours is ≤1% within the pH range of 3-9 and temperature range of -10 to 60℃.

[0030] Preferably, the method further includes a step of uranium recovery from uranium-containing precipitates: soaking the uranium-containing precipitates in 1 mol / L dilute nitric acid at 75°C for 1–2 hours, with a uranium recovery rate ≥90%.

[0031] Preferably, when Ca in uranium-containing wastewater 2+ Concentration ≤100mg / L, CO3 2- When the concentration is ≤50mg / L, the uranium removal rate reaches over 92%.

[0032] Preferably, ethanol is replaced with methanol or isopropanol, with a volume ratio of methanol or isopropanol to pretreated wastewater of 1:100. Both methanol and isopropanol are carbon sources available to Shewanella and can generate reducing free radicals under ultraviolet light. Methanol is cheaper, while isopropanol has stronger photochemical activity. The choice can be made flexibly based on local chemical availability.

[0033] Example 1 This embodiment focuses on the treatment of uranium-containing wastewater with an initial uranium concentration of 10 mg / L, using basic process parameters. The specific steps are as follows: Step 1: Adjust the pH of the uranium-containing wastewater to 4.5 using dilute nitric acid or dilute alkali to obtain pretreated wastewater.

[0034] Step 2: Add ethanol and Shewanella enrichment solution to the pretreated wastewater. The volume ratio of ethanol to pretreated wastewater is 1:100, and the concentration of the concentrated Shewanella enrichment solution is 5 × 10⁻⁶. 8 The concentration of CFU / mL was increased to a volume ratio of 1:200 with that of the pretreated wastewater. The mixture was then sealed and allowed to stand for 2 days for biological reduction to obtain the biological reduction solution.

[0035] Step 3: Irradiate the biological reducing solution with ultraviolet light of wavelength 365nm for 10 hours to perform photochemical deep reduction and obtain the photochemical reducing solution.

[0036] Step 3: Perform solid-liquid separation on the photochemical reducing solution to obtain qualified effluent and uranium-containing precipitate UO2.

[0037] After treatment in this embodiment, the uranium concentration in the effluent is 0.2 mg / L ≤ 0.5 mg / L, the uranium removal rate reaches 98%, and the uranium-containing precipitate has a dissolution rate of 0.3% after soaking for 48 hours in a pH range of 3-9 and a temperature range of -10 to 60°C, with a dissolution rate ≤ 1%.

[0038] Example 2 This embodiment addresses uranium-containing wastewater with an initial uranium concentration of 100 mg / L, and implements treatment using basic process parameters. The specific steps are as follows: Step 1: Adjust the pH of the uranium-containing wastewater to 5.5 using dilute nitric acid or dilute alkali to obtain pretreated wastewater.

[0039] Step 2: Add ethanol and Shewanella enrichment solution to the pretreated wastewater. The volume ratio of ethanol to pretreated wastewater is 1:100, and the concentration of the concentrated Shewanella enrichment solution is 5 × 10⁻⁶. 8 The concentration of CFU / mL was increased to a volume ratio of 1:200 with that of the pretreated wastewater. The mixture was then sealed and allowed to stand for 2 days for biological reduction to obtain the biological reduction solution.

[0040] Step 3: Irradiate the biological reducing solution with ultraviolet light of wavelength: 365nm for 10 hours to carry out photochemical deep reduction and obtain the photochemical reducing solution.

[0041] Step 4: Perform solid-liquid separation on the photochemical reducing solution to obtain qualified effluent and uranium-containing precipitate UO2.

[0042] After treatment in this embodiment, the uranium concentration in the effluent is 0.45 mg / L ≤ 0.5 mg / L, the uranium removal rate reaches 99.55%, and the leaching rate of uranium-containing precipitates after soaking for 48 hours in a pH range of 3-9 and a temperature range of -10 to 60°C is 0.5%, with a leaching rate ≤ 1%.

[0043] Example 3 This example is for an initial uranium concentration of 50 mg / L and Ca... 2+ Concentration 80 mg / L, CO3 2- The specific steps for treating uranium-containing wastewater with a concentration of 40 mg / L are as follows: Step 1: Adjust the pH of the uranium-containing wastewater to 5.0 using dilute nitric acid or dilute alkali to obtain pretreated wastewater.

[0044] Step 2: Add ethanol and Shewanella enrichment solution to the pretreated wastewater. The volume ratio of ethanol to pretreated wastewater is 1:100, and the concentration of the concentrated Shewanella enrichment solution is 1×10⁻⁶. 6 The concentration of CFU / mL was increased to a volume ratio of 1:200 with that of the pretreated wastewater. The mixture was then sealed and allowed to stand for 2 days for biological reduction to obtain the biological reduction solution.

[0045] Step 3: Irradiate the biological reducing solution with ultraviolet light of wavelength 320nm for 8 hours to carry out photochemical deep reduction and obtain the photochemical reducing solution.

[0046] Step 4: Perform solid-liquid separation on the photochemical reducing solution to obtain qualified effluent and uranium-containing precipitate UO2.

[0047] After treatment in this embodiment, the uranium concentration in the effluent is 0.35 mg / L ≤ 0.5 mg / L, the uranium removal rate reaches 99.3%, and the leaching rate of uranium-containing precipitates after soaking for 48 hours in a pH range of 3-9 and a temperature range of -10 to 60°C is 0.6%, with a leaching rate ≤ 1%.

[0048] Example 4 This example is for an initial uranium concentration of 60 mg / L and Ca... 2+ Concentration 90 mg / L, CO3 2- The specific steps for treating uranium-containing wastewater with a concentration of 30 mg / L are as follows: Step 1: Adjust the pH of the uranium-containing wastewater to 5.0 using dilute nitric acid or dilute alkali to obtain pretreated wastewater.

[0049] Step 2: Add ethanol and Shewanella enrichment solution to the pretreated wastewater. The volume ratio of ethanol to pretreated wastewater is 1:100, and the concentration of the concentrated Shewanella enrichment solution is 8 × 10⁻⁶. 9 The concentration of CFU / mL was increased to a volume ratio of 1:200 with that of the pretreated wastewater. The mixture was then sealed and allowed to stand for 2 days for biological reduction to obtain the biological reduction solution.

[0050] Step 3: Irradiate the biological reducing solution with ultraviolet light of wavelength 400nm for 12 hours to carry out photochemical deep reduction and obtain the photochemical reducing solution.

[0051] Step 4: Perform solid-liquid separation on the photochemical reducing solution to obtain qualified effluent and uranium-containing precipitate UO2.

[0052] After treatment in this embodiment, the uranium concentration in the effluent was 0.28 mg / L ≤ 0.5 mg / L, the uranium removal rate reached 99.53%, and the leaching rate of uranium-containing precipitates after soaking for 48 hours in a pH range of 3-9 and a temperature range of -10 to 60°C was 0.4%, with a leaching rate ≤ 1%.

[0053] Example 5 This embodiment targets uranium-containing wastewater with an initial uranium concentration of 40 mg / L and a pH value of 5.0. It uses direct sunlight instead of ultraviolet light and is suitable for remote mining areas with difficult power supply. The specific steps are as follows: Step 1: The original pH of the uranium-containing wastewater is 5.0, which is within the range of 4.5-5.5. It can be directly used as pre-treated wastewater, and the acid adjustment step is omitted.

[0054] Step 2: Add ethanol and Shewanella enrichment solution to the pretreated wastewater. The volume ratio of ethanol to pretreated wastewater is 1:100, and the concentration of the concentrated Shewanella enrichment solution is 2×10⁻⁶. 9 The concentration of CFU / mL was increased to a volume ratio of 1:200 with that of the pretreated wastewater. The mixture was then sealed and allowed to stand for 2 days for biological reduction to obtain the biological reduction solution.

[0055] Step 3: Place the biological reducing solution in direct sunlight outdoors for 60 hours to perform photochemical deep reduction and obtain the photochemical reducing solution.

[0056] Step 4: Perform solid-liquid separation on the photochemical reducing solution to obtain qualified effluent and uranium-containing precipitate UO2.

[0057] After treatment in this embodiment, the uranium concentration in the effluent is 0.32 mg / L ≤ 0.5 mg / L, the uranium removal rate reaches 99.2%, there is no power consumption throughout the process, and the process has strong adaptability.

[0058] Example 6 This embodiment is for acidic uranium-containing mine wastewater with an initial uranium concentration of 30 mg / L and an initial pH of 4.8. The acid adjustment step is directly omitted, and the specific steps are as follows: Step 1: The original pH of the uranium-containing wastewater is 4.8, which is within the process range of 4.5-5.5. It is directly used as pre-treated wastewater.

[0059] Step 2: Add ethanol and Shewanella enrichment solution to the pretreated wastewater. The volume ratio of ethanol to pretreated wastewater is 1:100, and the concentration of the concentrated Shewanella enrichment solution is 1×10⁻⁶. 8 The concentration of CFU / mL was increased to a volume ratio of 1:200 with that of the pretreated wastewater. The mixture was then sealed and allowed to stand for 2 days for biological reduction to obtain the biological reduction solution.

[0060] Step 3: Irradiate the biological reducing solution with ultraviolet light of wavelength 365nm for 10 hours to perform photochemical deep reduction and obtain the photochemical reducing solution.

[0061] Step 4: Perform solid-liquid separation on the photochemical reducing solution to obtain qualified effluent and uranium-containing precipitate UO2.

[0062] After treatment in this embodiment, the uranium concentration in the effluent is 0.25 mg / L ≤ 0.5 mg / L, and Shewanella bacteria inhibit coexisting bacteria in the wastewater by 95% ≥ 90%, eliminating the need for sterilization treatment. This simplifies the process while ensuring the treatment effect.

[0063] Example 7 This embodiment addresses uranium-containing wastewater with an initial uranium concentration of 50 mg / L, using methanol instead of ethanol. The steps are as follows: Step 1: Adjust the pH of the uranium-containing wastewater to 5.0 to obtain pretreated wastewater.

[0064] Step 2: Add methanol and Shewanella enrichment solution to the pretreated wastewater. The volume ratio of methanol to pretreated wastewater is 1:100, and the concentration of the concentrated Shewanella enrichment solution is 3×10⁻⁶. 8 The concentration of CFU / mL was increased to a volume ratio of 1:200 with that of the pretreated wastewater. The mixture was then sealed and allowed to stand for 2 days for biological reduction to obtain the biological reduction solution.

[0065] Methanol is also a carbon source that Shewanella can utilize, and it can generate reducing free radicals under ultraviolet light. Methanol is also cheaper and can be flexibly selected based on the local chemical supply.

[0066] Step 3: Irradiate with ultraviolet light at a wavelength of 365nm for 10 hours to obtain a photochemical reducing solution.

[0067] Step 4: After solid-liquid separation, the uranium concentration in the effluent is 0.3 mg / L ≤ 0.5 mg / L, and the uranium removal rate is 99.4%.

[0068] Example 8 This embodiment addresses the same batch of uranium-containing wastewater as in Example 7, with an initial uranium concentration of 50 mg / L, using isopropanol instead of ethanol. The steps are as follows: Step 1: Adjust the pH of the uranium-containing wastewater to 5.0 to obtain pretreated wastewater.

[0069] Step 2: Add isopropanol and Shewanella enrichment solution to the pretreated wastewater. The volume ratio of isopropanol to pretreated wastewater is 1:100, and the concentration of the concentrated Shewanella enrichment solution is 3×10⁻⁶. 8 The concentration of CFU / mL was increased to a volume ratio of 1:200 with that of the pretreated wastewater. The mixture was then sealed and allowed to stand for 2 days for biological reduction to obtain the biological reduction solution.

[0070] Isopropanol is also a carbon source that Shewanella can utilize, and both can generate reducing free radicals under ultraviolet light. Isopropanol has stronger photochemical activity and can be flexibly selected according to the local chemical supply.

[0071] Step 3: Irradiate with ultraviolet light at a wavelength of 365nm for 10 hours to obtain a photochemical reducing solution.

[0072] Step 4: After solid-liquid separation, the uranium concentration in the effluent is 0.22 mg / L ≤ 0.5 mg / L, the uranium removal rate is 99.56%, isopropanol has stronger photochemical activity and better deep reduction effect.

[0073] Example 9 This embodiment uses a mixed bacterial community containing Shewanella bacteria enriched from the bottom sediment of a uranium tailings pond to replace the pure Shewanella enrichment solution, and performs uranium recovery from the uranium-containing precipitate, targeting an initial uranium concentration of 80 mg / L and Ca... 2+ Concentration 100 mg / L, CO3 2- The specific steps for treating uranium-containing wastewater with a concentration of 50 mg / L are as follows: Step 1: Adjust the pH of the uranium-containing waste to 5.2 to obtain pretreated wastewater; Step 2: Add ethanol and a mixed bacterial suspension enriched with uranium tailings pond sediment (containing Shewanella, with an equivalent Shewanella enrichment concentration of 4 × 10⁻⁶) to the pretreated wastewater.8 (The volume ratio of CFU / mL to the volume ratio of Shewanella enrichment solution to pretreated wastewater is 1:200. The volume ratio of ethanol to pretreated wastewater is 1:100. The mixture is sealed and allowed to stand for 2 days for biological reduction to obtain the biological reduction solution.)

[0074] Step 3: Irradiate the biological reducing solution with ultraviolet light of wavelength 365nm for 11 hours to perform photochemical deep reduction and obtain the photochemical reducing solution.

[0075] Step 4: Perform solid-liquid separation on the photochemical reducing solution to obtain qualified effluent and uranium-containing precipitate UO2; Step 5: Uranium recovery. Use 1 mol / L dilute nitric acid heated to 75°C to soak the above uranium-containing precipitate for 1.5 hours to complete the uranium leaching and recovery.

[0076] After treatment in this embodiment, the uranium concentration in the effluent is 0.4 mg / L ≤ 0.5 mg / L, because Ca 2+ CO3 2- At the limit value, the uranium removal rate reaches 92.5% (≥92%); in the uranium recovery step, the uranium recovery rate reaches 95% (≥90%), achieving the dual effect of treating uranium-containing wastewater to meet standards and recovering uranium resources. The uranium-containing precipitate, after soaking for 48 hours at a pH of 3-9 and a temperature range of -10 to 60℃, has a dissolution rate of 0.6% (≤1%), indicating good stability.

[0077] In summary, this invention introduces an ultraviolet irradiation step. The highly reducing free radicals generated by the photochemical reaction (produced by the photolysis of ethanol) directly participate in the reduction of uranium, constructing a "biological-photochemical" dual-dynamic reduction system. The addition of the photochemical process significantly improves the reaction kinetic rate and shortens the overall processing time.

[0078] This invention uses ethanol (or methanol or isopropanol) as the core additive. Ethanol is both an inexpensive carbon source (electron donor) required for the growth of Shewanella and a highly efficient photoreducing agent under ultraviolet light. This "dual-purpose" design significantly reduces the cost of the agent, and ethanol is non-toxic and easily biodegradable, avoiding secondary pollution.

[0079] This invention proposes a process with an extremely simple procedure. It requires only three simple steps: "pH adjustment - bacterial addition and settling - ultraviolet light irradiation". It does not require complex membrane modules or high-pressure equipment, and the process has low environmental requirements, which greatly reduces the threshold for engineering implementation and operating energy consumption.

[0080] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for treating uranium-containing wastewater, characterized in that, Includes the following steps: The pH value of the uranium-containing wastewater was adjusted to 4.5-5.5 to obtain pretreated wastewater; Ethanol and Shewanella enrichment solution were added to the pretreated wastewater at a volume ratio of 1:

100. The mixture was then sealed and allowed to stand for 2 days for biological reduction to obtain a biologically reduced solution. The biological reducing solution was irradiated with ultraviolet light for 8–12 hours to perform photochemical deep reduction, thereby obtaining a photochemical reducing solution. The photochemical reducing solution was subjected to solid-liquid separation to obtain qualified effluent and uranium-containing precipitate.

2. The method for treating uranium-containing wastewater according to claim 1, characterized in that, The concentration of the Shewanella enrichment solution was 1×10⁻⁶. 6 ~8×10 9 The amount of CFU / mL added is in a volume ratio of 1:200 to the pretreated wastewater.

3. The method for treating uranium-containing wastewater according to claim 2, characterized in that, Under conditions of pH 4.5-5.5 and in the presence of ethanol, the Shewanella bacteria exhibit an inhibition rate of ≥90% against coexisting bacteria in wastewater, eliminating the need for sterilization treatment.

4. The method for treating uranium-containing wastewater according to claim 1, characterized in that, The wavelength of the ultraviolet light is 320–400 nm.

5. The method for treating uranium-containing wastewater according to claim 1, characterized in that, The uranium-containing wastewater is uranium-containing wastewater with an initial uranium concentration of 10-100 mg / L. After treatment by the method, the uranium concentration in the effluent is ≤0.5 mg / L.

6. The method for treating uranium-containing wastewater according to claim 1, characterized in that, Instead of exposing the biological reducing solution to ultraviolet light for 8–12 hours, expose the biological reducing solution to direct sunlight outdoors for 48–72 hours.

7. The method for treating uranium-containing wastewater according to claim 1, characterized in that, The uranium-containing precipitate is UO2, and its dissolution rate is ≤1% after soaking for 48 hours in the pH range of 3-9 and temperature range of -10 to 60℃.

8. The method for treating uranium-containing wastewater according to claim 7, characterized in that, It also includes a step of uranium recovery from the uranium-containing precipitate: soaking the uranium-containing precipitate in 1 mol / L dilute nitric acid at 75°C for 1 to 2 hours, with a uranium recovery rate ≥90%.

9. A method for treating uranium-containing wastewater according to claim 1, characterized in that, When uranium-containing wastewater Ca 2+ Concentration ≤100mg / L, CO3 2- When the concentration is ≤50mg / L, the uranium removal rate reaches over 92%.

10. A method for treating uranium-containing wastewater according to claim 1, characterized in that, The ethanol is replaced with methanol or isopropanol, and the volume ratio of methanol or isopropanol to pretreated wastewater is 1:100.

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