CN108911102B - Method for recycling uranium in uranium-containing wastewater and underground water through efficient electrochemical reduction and enrichment - Google Patents
Method for recycling uranium in uranium-containing wastewater and underground water through efficient electrochemical reduction and enrichment Download PDFInfo
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- CN108911102B CN108911102B CN201810765731.3A CN201810765731A CN108911102B CN 108911102 B CN108911102 B CN 108911102B CN 201810765731 A CN201810765731 A CN 201810765731A CN 108911102 B CN108911102 B CN 108911102B
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/70—Treatment of water, waste water, or sewage by reduction
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/006—Radioactive compounds
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/20—Heavy metals or heavy metal compounds
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/06—Contaminated groundwater or leachate
Abstract
The invention discloses a method for recycling uranium in uranium-containing wastewater and underground water by efficient electrochemical reduction and enrichment. The method uses the metal electrode as a cathode and an anode to construct an electrochemical system, utilizes the property that hexavalent uranyl ions can obtain electrons to be reduced into tetravalent insoluble uranium dioxide, and reduces the hexavalent uranium into the uranium dioxide through the electrode and enriches the uranium dioxide on the surface of the electrode under the condition of no exogenous additive. The uranium plating layer can further catalyze and reduce the hexavalent uranium in the wastewater to form a new uranium plating layer. After the electrochemical reduction enrichment is completed, the electrode enriched with uranium dioxide is taken out of the solution, and the efficient reduction removal of uranium in wastewater and underground water can be realized. By further putting the electrode into dilute nitric acid solution for oxidation, efficient recovery can be further realized. The method has wide application range, and can realize high-efficiency removal and recovery of uranyl carbonate in low-concentration and high-concentration uranium-containing wastewater and carbonate-containing underground water.
Description
Technical Field
The invention belongs to the field of wastewater treatment, and relates to a method for recycling uranium-containing wastewater and uranium in underground water by efficient electrochemical reduction and enrichment.
Background
With the exploitation of uranium ores and the wide use of nuclear energy, the uranium pollution condition on the global scale is becoming serious day by day. Uranium, as a pollutant having both heavy metal toxicity and radioactivity, has a great threat to the ecological environment and human health due to migration in a water environment. The uranium content in surface water or ground water of many countries has greatly exceeded the drinking water standard (30 mug/L) of the world health organization, such as uranium concentration in wastewater of uranium mining areas as high as 50 mg/L. The development of an economical and effective uranium pollution control technology is the key to solving the uranium pollution. Meanwhile, with the increase of global nuclear energy demand, the demand of uranium elements is also larger and larger, and the development of an efficient uranium enrichment recovery technology is urgently needed. Therefore, the process for removing uranium in uranium-containing wastewater and synchronously realizing uranium recovery is established, and has very important significance in uranium pollution control and resource recovery.
At present, the reported methods for removing uranium mainly include adsorption method, chemical precipitation method, ion exchange method, membrane technology method and the like. The adsorption method is to adsorb uranium on the surface of an adsorbent by means of chemical coordination or physical adsorption by adding the adsorbent. Because the treatment capacity of the adsorption method is limited, the treatment effect on high-concentration uranium-containing wastewater is not ideal, and the treatment efficiency on complex uranium such as uranyl carbonate in groundwater is very low; in addition, because the adsorbent has adsorption equilibrium, the treatment efficiency of the uranium-containing wastewater system with low concentration is low. The chemical precipitation method is to fix uranium from an aqueous environment in a precipitation form by adding a flocculating agent and a coagulant aid, but the method has poor treatment effect on complex uranium such as uranyl carbonate, and a large amount of flocculating agent and waste residue cause secondary pollution. The ion exchange method is similar to the adsorption method, uranium is enriched by adding an ion exchanger, but the treatment effect of the ion exchange method is limited by the concentration of competitive ions in the water environment. The membrane separation method is a method utilizing selective permeation of a membrane to uranium, has the problem of difficult separation of complex uranium, is easily polluted by organic matters in water to cause blockage, causes reduction of treatment capacity, and is not beneficial to large-scale application.
The electrochemical method has the advantages of rapid reaction, strong controllability, simple operation and the like, and is widely applied to the field of pollution control. The electrochemical system disclosed at the present stage mainly has two methods for removing uranium: one method is to generate a co-deposition agent in situ, for example, by utilizing an electric flocculation technology, so that free ferrous ions generated by an iron anode are co-deposited with uranium in a water body; the other method is to artificially add a complexing agent, mainly to add some short-chain organic molecules, wherein a small molecular intermediate generated by anodic oxidation can form a complex precipitate with low-valence uranium generated by cathodic reduction, and the complex precipitate is deposited on the surface of an electrode. The two methods are essentially modified from chemical deposition methods, and the introduction of the electrode system merely assists the process.
Disclosure of Invention
The invention aims to provide a method for efficiently recovering uranium from uranium-containing wastewater and underground water by electrochemical reduction and enrichment.
The invention claims a method for enriching uranium in uranium-containing wastewater and/or groundwater, wherein the enrichment comprises the following steps:
for the uranium-containing wastewater and/or underground water with the concentration of hexavalent uranium higher than 2mg/L, taking a stable metal material with high conductivity as a cathode material and an anode material, performing electric reduction by using a direct current power supply, and enriching on the surface of the cathode to obtain tetravalent uranium;
and for the uranium-bearing wastewater and/or the underground water with the concentration of hexavalent uranium lower than or equal to 2mg/L, taking a stable metal electrode with high conductivity and a uranium dioxide coating covering the surface as a cathode material, taking a stable metal material with high conductivity as an anode material, performing electro-reduction by using a direct current power supply, enriching on the surface of the cathode to obtain tetravalent uranium, and finishing the enrichment of uranium in the uranium-bearing wastewater and/or the underground water.
In the above method, the stable and highly conductive metal material is a titanium sheet or a stainless steel sheet.
The voltage of the direct current power supply is 2-5V;
in the step of electroreduction, the temperature is normal temperature; the time is 0.5-15 h.
The metal electrode with the surface covered with the uranium dioxide coating is prepared by the method comprising the following steps:
in the uranium-containing solution, the concentration of hexavalent uranium is higher than 2 mg/L; specifically 20-100 mg/L; (ii) a More specifically 55 mg/L.
In the reduction step, the temperature is normal temperature; the time is 0.5 to 20 hours; specifically 15 hours; the pH value is 2-10.
The invention also claims a method for recovering uranium from uranium-containing wastewater and groundwater, which comprises the following steps:
and (3) placing the cathode with the surface enriched with the tetravalent uranium obtained by the enrichment method in a recovery liquid for oxidation recovery, and completing the recovery of the tetravalent uranium after the reaction is finished.
In the method, the recovery liquid is dilute nitric acid; the mass percentage concentration of the dilute nitric acid is 5-40%; specifically 20%.
In the step of oxidation recovery, the time is 0.5-5 hours; specifically 2 hours; the temperature is normal temperature.
The method is suitable for enriching and recycling uranium in uranium-containing wastewater of various low-concentration and high-concentration hexavalent uranium and carbonate-containing groundwater of various low-concentration and high-concentration hexavalent uranium.
The invention also claims a method for enriching and recovering uranium in uranium-containing wastewater and groundwater. The method comprises the following steps: the steps of the enrichment process and the steps of the recovery process described previously.
According to the invention, based on the property that hexavalent uranyl ions existing in a large amount in a water body environment can obtain electrons to be reduced into tetravalent insoluble uranium dioxide, hexavalent uranium is reduced into uranium dioxide through an electrode and is enriched on the surface of the electrode under the condition of no external additive. After the electrochemical reduction enrichment is completed, the electrode enriched with uranium dioxide is taken out of the solution, and the efficient reduction removal of uranium in wastewater and underground water can be realized. And the electrode is further put into a dilute nitric acid solution for oxidation, so that the high-efficiency recovery of uranium can be further realized. In addition, the uranium dioxide coating formed on the surface of the electrode through reduction does not cause adverse effect on electrochemical reduction, and on the contrary, the formed uranium dioxide coating has an adsorption effect on hexavalent uranium, so that the reduction removal efficiency of the electrode is higher and higher along with the accumulation of the uranium dioxide coating in the batch treatment process. Therefore, the electrode for forming the uranium dioxide coating can be reused for a plurality of times without affecting the removal effect. By utilizing the characteristic, the method can realize the removal and recovery of the hexavalent uranium in the uranium-containing wastewater with low concentration and high concentration and the carbonate-containing groundwater.
The principle of the invention is as follows:
according to thermodynamic calculation, in a uranium-containing solution system, when a certain potential is applied to the outside, a cathode can reduce dissolved hexavalent uranium into insoluble tetravalent uranium (uranium dioxide), the uranium dioxide generated by reduction can be deposited on the surface of an electrode in the form of a coating, and the uranium in the solution can be removed by taking out the electrode after the reduction is completed.
The generated uranium dioxide coating has a catalytic effect on electrochemical reduction of hexavalent uranium, so that the subsequent reduction process can be greatly accelerated, and more uranium dioxide coatings are generated. Therefore, the electrode in the method has extremely large reduction capacity.
Because the uranium dioxide coating has a catalytic action on electrochemical reduction of hexavalent uranium, rapid reduction removal of extremely low-concentration uranium can be realized by using an electrode with the existing uranium dioxide coating as a cathode.
The uranium dioxide formed on the surface of the electrode is easily oxidized into hexavalent uranium by oxidizing substances. And the electrode after reducing and enriching uranium is placed into 20% nitric acid, so that rapid recycling of uranium can be realized. Meanwhile, the electrode after uranium recovery can be reused.
The invention has the following beneficial effects:
1. the method can realize efficient and rapid removal and recovery of uranium in wastewater, does not need complex steps such as net capture, sediment retreatment and the like, is simple and convenient to operate, has low cost and no secondary pollution, and can recycle the electrode for a long time without treatment processes such as sintering and the like.
2. The method has wide application range, and has better removal and recovery effects on the uranium-containing wastewater with low concentration (0.02mg/L-2mg/L) and high concentration (more than 2 mg/L).
3. Carbonate is usually contained in groundwater, and forms a stable uranyl carbonate complex with hexavalent uranium, and the uranyl carbonate complex is difficult to remove by traditional adsorption and other methods. The method has a good effect of removing uranium in the carbonate-containing groundwater.
4. The invention has wide pH application range, and does not need to adjust the initial pH value for the wastewater with the pH value within the range of 2-10. Because the titanium sheet is very stable, the anode material does not need to be replaced, the whole treatment process has no secondary pollution, the operation condition is convenient, and the method can be realized at normal temperature and normal pressure.
5. The uranium plating layer of the reduction enrichment on the surface of the electrode can not inhibit the further reduction of uranium, but can catalyze and accelerate the recovery of uranium, so that the technology has huge uranium reduction removal capacity.
Detailed Description
The present invention will be further illustrated with reference to the following specific examples, but the present invention is not limited to the following examples. The method is a conventional method unless otherwise specified. The starting materials are commercially available from the open literature unless otherwise specified.
Example 1 uranium-containing wastewater of certain high concentration
Adding 100ml of uranium-containing wastewater (U (VI)) with the concentration of 55mg/L and the pH value of 7.5 into a reaction tank, and performing electroreduction and uranium removal by taking a titanium plate as a cathode and an anode under the condition of about 2V direct current power supply. After the electric reduction is carried out for 8 hours under the conditions of normal temperature and normal pressure, the concentration of uranium in the water body is reduced to 0.07mg/L, and the uranium removal efficiency reaches 99.9 percent. After the electrode is used for five times continuously, the surface of the titanium plate is covered by a large amount of deposits, and the uranium removal efficiency is not reduced. After the electrode is put into 100mL of 20% nitric acid solution at normal temperature and placed for 2 hours, the silvery white surface of the titanium plate electrode is recovered, and the recovery rate of uranium on the surface of the electrode reaches 99.9%.
Example 2 high-concentration, high-carbonate uranium-containing wastewater
100ml of high-concentration and high-carbonate uranium-containing wastewater (U (VI)) with the concentration of 50mg/L, the carbonate concentration of about 30mM and the pH value of 7.5 is added into a reaction tank, and electroreduction is carried out to remove uranium under the condition of about 2V of direct current power supply by taking a titanium plate as a cathode and an anode. After the electric reduction is carried out for 15 hours under the conditions of normal temperature and normal pressure, the concentration of uranium in the water body is reduced to 0.02mg/L, and the uranium removal efficiency reaches 99.9 percent. After the electrode is used for five times continuously, the surface of the titanium plate is covered by a large amount of deposits, and the uranium removal efficiency is not reduced. After the electrode is put into 100mL of 20% nitric acid solution at normal temperature and placed for 2 hours, the silvery white surface of the titanium plate electrode is recovered, and the recovery rate of uranium on the surface of the electrode reaches 99.9%.
Example 3 certain Low concentration uranium-containing wastewater
Firstly, adding a titanium metal electrode into a high-concentration uranium-containing solution (U (VI) concentration is 55mg/L), carrying out electro-reduction for 15 hours under the conditions of normal temperature and normal pressure, obtaining a titanium metal plate electrode covered with a uranium dioxide coating, and taking the titanium metal plate electrode as a cathode. 100ml of low-concentration uranium-containing wastewater (U (VI)) with the concentration of 0.1mg/L, the carbonate concentration of about 30mM and the pH value of 7.5 is added into a reaction tank, a titanium metal plate with a uranium dioxide coating is used as a cathode, a titanium metal plate with a clean surface is used as an anode, and electroreduction is carried out to remove uranium under the condition of a direct current power supply of about 2.5V. After the electric reduction is carried out for 13 hours under the conditions of normal temperature and normal pressure, the concentration of uranium in the water body is reduced to 0.001mg/L, and the uranium removal efficiency reaches 99.9 percent. After five consecutive uses of the electrode, the uranium removal efficiency was not reduced. After the electrode is put into 100mL of 20% nitric acid solution at normal temperature and placed for 2 hours, the silvery white surface of the titanium plate electrode is recovered, and the recovery rate of uranium on the surface of the electrode reaches 99.9%.
Claims (12)
1. A method of enriching uranium in uranium-bearing wastewater and/or groundwater, comprising:
and for the uranium-bearing wastewater and/or the underground water with the concentration of hexavalent uranium lower than or equal to 2mg/L, taking a stable metal electrode with high conductivity and a uranium dioxide coating covering the surface as a cathode material, taking a stable metal material with high conductivity as an anode material, performing electro-reduction by using a direct current power supply, enriching on the surface of the cathode to obtain tetravalent uranium, and finishing the enrichment of uranium in the uranium-bearing wastewater and/or the underground water.
2. The method of claim 1, wherein: the stable and high-conductivity material is a titanium sheet or a stainless steel sheet.
3. The method of claim 1, wherein: the voltage of the direct current power supply is 2-5V;
in the step of electroreduction, the temperature is normal temperature; the time is 0.5-20 h.
4. The method of claim 1, wherein: the metal electrode with the surface covered with the uranium dioxide coating is prepared by the method comprising the following steps:
reducing the stable and high-conductivity metal material in a uranium-containing solution; in the uranium-containing solution, the concentration of hexavalent uranium is higher than 2 mg/L.
5. The method of claim 4, wherein: in the uranium-containing solution, the concentration of hexavalent uranium is 20-100 mg/L.
6. The method of claim 5, wherein: in the uranium-containing solution, the concentration of hexavalent uranium is 55 mg/L.
7. The method according to any one of claims 4-6, wherein: in the reduction step, the temperature is normal temperature; the time is 1-20 hours.
8. The method of claim 7, wherein: in the reduction step, the time is 15 hours.
9. A method for recycling uranium in uranium-containing wastewater and groundwater comprises the following steps:
and (3) placing the cathode enriched with the tetravalent uranium on the surface obtained by the method of any one of claims 1 to 8 in a recovery liquid for oxidation recovery, and finishing the recovery of the tetravalent uranium after the reaction is finished.
10. The method of claim 9, wherein: the recovery liquid is dilute nitric acid; the mass percentage concentration of the dilute nitric acid is 5-40%.
11. The method of claim 10, wherein: the mass percentage concentration of the dilute nitric acid is 20%.
12. The method of claim 11, wherein: in the step of oxidation recovery, the time is 0.5-5 hours; the temperature is normal temperature.
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| CN109942076B (en) * | 2019-04-01 | 2020-08-28 | 中国科学院生态环境研究中心 | Method for removing and recycling uranium in water and synchronously generating electricity by utilizing microbial fuel cell |
| CN109867333B (en) * | 2019-04-01 | 2021-04-13 | 中国科学院生态环境研究中心 | Method for efficiently removing and recycling uranium in water by using titanium-based titanium dioxide nanotube array electrode |
| CN109972173B (en) * | 2019-05-09 | 2024-02-27 | 东华理工大学 | Device for recycling uranium in nuclear wastewater by using solar-based modified NZVI three-dimensional electrochemical method |
| CN113707351A (en) * | 2020-11-24 | 2021-11-26 | 核工业北京化工冶金研究院 | Static uranium removing method for sponge iron filter material |
| CN113089016A (en) * | 2021-03-10 | 2021-07-09 | 西南科技大学 | Preparation method of high-performance single-center uranium-based supported catalyst |
| CN113880234B (en) * | 2021-10-14 | 2023-10-20 | 中国科学院生态环境研究中心 | Microbial electrolysis method for continuously and efficiently removing and recycling uranium in water |
| CN114031157B (en) * | 2021-11-18 | 2023-05-23 | 中国科学院生态环境研究中心 | Method for removing and recycling heavy metals in water by utilizing porous three-dimensional wood-based electrode |
| CN114214635A (en) * | 2021-11-29 | 2022-03-22 | 哈尔滨工程大学 | Method for efficiently preparing uranium dioxide by adopting electrodeposition |
| CN114380361B (en) * | 2021-12-10 | 2023-06-30 | 中国科学院生态环境研究中心 | Method for recycling uranium in uranium-containing wastewater and groundwater through electrochemical reduction enrichment in coexistence of nitrate |
| CN116282176A (en) * | 2022-09-09 | 2023-06-23 | 哈尔滨工程大学 | Method for directly recovering high-purity uranium oxide from uranium-containing wastewater |
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| US3954594A (en) * | 1974-09-04 | 1976-05-04 | Rockwell International Corporation | Electrochemical cell for decreasing the cyanide and heavy metal content of an aqueous solution |
| CN1182275C (en) * | 2003-05-27 | 2004-12-29 | 清华大学 | Electro-deposition method of separating yttrium-90 from strontium-90-yttrium-90 system |
| CN105280261B (en) * | 2015-10-01 | 2017-06-09 | 南华大学 | A kind of method that electroreduction for uranium-containing waste water treatment precipitates uranium |
| CN206646177U (en) * | 2017-01-03 | 2017-11-17 | 中国原子能科学研究院 | A kind of device that UO2 target piece is prepared suitable for electrodeposition process |
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