ONE-STEP METHOD FOR ELECTROKINETIC URANIUM EXTRACTION AND SEPARATION FROM SANDSTONE-TYPE URANIUM DEPOSIT

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority from Chinese Patent Application No. 202510748674.8, filed on Jun. 6, 2025. The content of the aforementioned application, including any intervening amendments thereto, is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to a method for purifying uranium elements, in particular to a one-step method for electrokinetic uranium extraction and separation from a sandstone-type uranium deposit.

BACKGROUND

There are numerous sandstone-type uranium deposits that are difficult to mine using in-situ leaching methods. These deposits typically feature poor permeability, high carbonate and argillaceous content, low ore grade, and complex geological and hydrogeological conditions. Uranium minerals in uranium ores are characterized by complex occurrences, high levels of tetravalent uranium, close symbiosis with gangue minerals, high content of organic matters and carbonate minerals, poor permeability and filtration properties, and difficulty in solid-liquid separation, making them difficult-to-process ores.

Traditional uranium leaching methods include acid leaching, alkaline leaching, CO₂+O₂ leaching, and microbial leaching. Acid leaching often uses H₂SO₄ as a leaching agent, but this process easily generates precipitates that block leaching channels. Alkaline leaching often uses Na₂CO₃ as a leaching agent, which shows selectivity for metal dissolution and hardly dissolves elements such as Ca, Mg, Fe, and Al. Alkaline leaching is generally slow and requires high temperatures. The recently emerging CO₂+O₂ leaching method, though beneficial for the development of low-grade uranium ores, is only suitable for ore bodies with a certain degree of permeability. Microorganisms such as Thiobacillus ferrooxidans have weak environmental adaptability, and these microbial leaching methods have high requirements for environment. All of the above leaching methods are not suitable for use in efficient extraction of uranium elements from sandstone-type uranium deposits with low permeability, low grade, diverse uranium occurrences, complex inter-mineral interface relationships, and high content of water.

Electromining is a new mining technology, with the main mechanism of promoting the migration and enrichment of dissolved charged ions and their complexes in the deposits through electromigration and electroosmosis. The existing related patents are as follows:

Chinese patent CN108411130A discloses a method for enhanced electro-assisted uranium leaching from low-grade uranium ore. The method uses dilute sulfuric acid with a concentration of 35-60 g/L as a leaching solution, metallic iron as the anode, and graphite or metallic iron as the cathode. Under the action of direct current, the anode iron gradually dissolves and converts into trivalent iron ions, providing an oxidant for the leaching system, promoting the conversion of insoluble tetravalent uranium to soluble hexavalent uranium, and finally producing the uranium-containing leachate for collection.

Chinese patent CN109609788A discloses a method for separating uranium from uranium ore pulp using electrodialysis. The method uses a sulfuric acid solution with a mass concentration of 48-55% as a leaching agent and includes stirring a uranium-containing ore sample with the leaching agent for leaching to obtain a uranium-containing ore pulp and separating uranium from the uranium-containing ore pulp using electrodialysis to finally obtain a uranium-rich solution and tailings.

Chinese patent CN114658407A discloses an electrokinetic in-situ leaching device and method for uranium mining. Uranium ore is placed between an injection well and an extraction well; a negative electrode is arranged in the injection well; a positive electrode is arranged in the extraction well; oxygen and hydrogen peroxide are used as oxidants, and sulfuric acid and CO₂ solutions are used as leaching agents; a leaching solution is injected from the injection well, passes through the uranium ore, and then is extracted from the extraction well, followed by collecting the leaching solution and then extracting uranium.

The leaching agents selected in the aforementioned patents CN108411130A, CN109609788A, and CN117564070A, such as sulfuric acid, citric acid, and oxalic acid, typically require to be used at a large amount. These leaching agents have a common problem that they cannot unify uranium elements into particles with the same electrical properties. Consequently, particles of varying charges, such as positively charged UO₂²⁺ and negatively charged UO₂(X)₂²⁻ and UO₂(X)₃⁴⁻ (where X is SO₄ or CO₃), coexist in the leachate. Due to the varying charge properties of these ions, their migration directions in the electric field also differ, making it impossible to achieve directional and controllable collection of uranium. Furthermore, the use of H₂SO₄ can result in the generation of insoluble matters that block the leaching channels, thereby affecting uranium leaching efficiency.

In addition, the final products are all uranium-containing leachates, which require further processing to remove impurities and refine the uranium. Currently, uranium leachates have complicated compositions, often containing a variety of metal ion impurities, increasing difficulty of separation. The leachates contain uranium-containing particles of various forms, such as positively charged UO₂²⁺ and negatively charged UO₂(X)₂^2-, with varying charges. These particles require different purification methods, making the impurity removal process complex. The commonly used extraction method also faces challenges such as extractant's high selectivity, high cost, ease of emulsification, and regeneration and disposal.

Therefore, there is an urgent need for a more efficient and convenient one-step method for extracting and separating uranium.

It should be noted that the information disclosed in the above background section is only used to facilitate the understanding of the background of the present disclosure, and therefore may include information that does not constitute prior art known to one of ordinary skills in the art.

SUMMARY

The present invention aims to provide a one-step method for electrokinetic uranium extraction and separation from a sandstone-type uranium deposit, thereby solving the problem that the existing electrokinetic uranium leaching technology cannot achieve the enrichment of uranium with particles of the same charge property on a fixed electrode and the simultaneous separation and purification in one step. The method of the present invention can make the uranium in the sandstone-type uranium deposit form only positively charged ions and complexes, thereby achieving directional migration and enrichment of uranium by utilizing electrophysical effects such as electromigration and electroosmosis, and capable of efficiently and selectively reduce oxidized high-valent uranium cations, which are ultimately reduced and fixed on the surface of a cathode conductive plastic electrode to realize the one-step method for electrokinetic uranium extraction and separation.

To achieve the above objective, the present invention provides a one-step method for electrokinetic uranium extraction and separation from a sandstone-type uranium deposit, the method comprising:

• • uranium activation: using an activating leaching agent to adjust the pH of the activation environment as pH≤3, converting uranium elements in the sandstone-type uranium deposit into positively charged uranyl and its complexes; where the activating leaching agent is a mixture of FeCl₃ and a chlorine-containing inorganic acid;
  • electric field drive: introducing the activated sandstone-type uranium deposit into a direct current (DC) electric field, applying a DC electric field with a voltage gradient of 0.1 V/cm to 2 V/cm between the cathode and anode, and allowing the positively charged uranyl and its complexes to undergo electrophysical effects such as electromigration and electroosmosis under the action of the electric field and to be directionally enriched in the cathode chamber;
  • electrode selective reduction and fixation of uranium: both the cathode and anode being conductive plastic electrodes, allowing selective reduction of the positively charged uranium elements on the surface of the cathode conductive plastic electrode by electrochemically reducing them to a low-valent insoluble uranium-containing substance (such as UO₂) and precipitating it on the surface of the cathode conductive plastic electrode, while other impurity metal ions will not precipitated on the surface of the cathode conductive plastic electrode through hydroxides, such that the uranium-containing precipitate collected on the surface of the cathode conductive plastic electrode has a very low impurity rate.

In the present invention, the uranium activation, electric drive, and selective reduction technologies are combined together. The uranium in the sandstone-type uranium deposit is converted into positively charged uranium, so that it moves toward the cathode conductive plastic electrode under the action of the electric field and then electrically reduced at the cathode conductive plastic electrode to convert the uranium into the low-valent insoluble uranium-containing substance that is precipitated on the surface of the cathode conductive plastic electrode, while other impurity metal ions are not precipitated on the surface of the cathode conductive plastic electrode through hydroxides, thereby enriching uranium.

During the activation process of the present invention, part of the insoluble tetravalent uranium in the deposit is gradually converted into soluble hexavalent uranium, including UO₂²⁺, a small amount of UO₂Cl⁺ formed by the complexation of UO₂²⁺ and Cl⁻, and positively charged particles such as (UO₂)₂OH³⁺, (UO₂)₂(OH)₂²⁺, (UO₂)₃(OH)₄²⁺, and (UO₂)₃(OH)⁵⁺ produced by the hydrolysis of UO₂²⁺.

Uranium is converted into the low-valent insoluble uranium-containing substance as follows:

Under the action of the electric field, uranyl ions are preferentially reduced. The reduction potential of uranyl ions and their uranyl chloride complex cations is higher than that of other metal ions such as potassium, sodium, calcium, and magnesium, making them more easily reduced. If Fe³⁺ in the oxidant is not used up during the activation process, and the pH required for the precipitation of Fe³⁺ is between 1.5 and 3.5, as such, some Fe³⁺ will hydrolyze and precipitate into the cathode liquid. Although the reduction potential of Fe³⁺ is relatively high, the remaining unhydrolyzed Fe³⁺ will be reduced to Fe²⁺ prior to UO₂²⁺, however, the pH required for the precipitation of Fe²⁺ needs to be between 7.0 and 9.0. Therefore, in the system of the present method, iron is not easily adsorbed and fixed by the cathode plate.

In addition, other metal elements are not prone to producing hydroxide precipitation under acidic conditions. The pH required for the precipitation of other metal elements is as follows: Al³⁺: pH 4.5-6.0; Cu²⁺: pH 6.0-8.0; Zn²⁺: pH 7.0-9.0; Ni²⁺: pH 8.0-9.5; Pb²⁺: pH 6.0-8.0; Mg²⁺: pH 10.5-12.0; Ca²⁺: pH 12.0-13.0.

Therefore, in the system of the present invention, only the electro-reduced tetravalent uranium precipitate is selectively retained on the cathode conductive plastic electrode, achieving the purpose of removing impurities and purifying uranium elements. Preferably, the voltage gradient is 0.1 V/cm to 0.5 V/cm. The uranium-containing precipitate collected on the surface of the cathode conductive plastic electrode has a very low impurity rate, particularly as low as below 5% when the voltage gradient does not exceed 0.5 V/cm.

Preferably, the solid-liquid ratio of the sandstone-type uranium deposit to the activating leaching agent is 1 kg: 1-10 L.

Preferably, the solid-liquid ratio of the sandstone-type uranium deposit to the activating leaching agent 1 kg: 5-10 L.

Preferably, the pH of the activating leaching agent is 0.5-3.

Preferably, the pH of the activating leaching agent is 0.5-1. Preferably, the concentration of FeCl₃ in the activating leaching agent is 10 g/L to 20 g/L.

Preferably, the chlorine-containing inorganic acid is selected from any one or more of HCl, HClO, and HClO₄. For example, the present invention utilizes HCl+FeCl₃ as the activating leaching agent, significantly reducing the amount of leaching agent used. FeCl₃ not only provides Fe³⁺ to oxidize UO₂ in the sandstone-type uranium deposit, but also provides Cl⁻. HCl also provides Cl⁻ while maintaining the acidic pH environment of the sandstone-type uranium deposit. Compared to uranium leaching with H₂SO₄ (Formulas 1-3), using HCl+FeCl₃ as the activating leaching agent can control the uranyl ions to only form positively charged complex ions UO₂Cl⁺ with Cl⁻, while preventing further complexation with chloride ions to form negatively charged complexes, thereby reducing the amount of leaching agent that provides Cl⁻.

Preferably, after adding the activating leaching agent, the sandstone-type uranium deposit is activated at a temperature of 0-40° C. (in this temperature range, liquid is ensured to be present in the ore slurry) for 1-24 hours, and then a direct current with a voltage gradient of 0.1 V/cm to 2 V/cm is applied between the cathode and anode for 1-24 hours.

Preferably, the sandstone-type uranium deposit is separated from the cathode conductive plastic electrode and the anode conductive plastic electrode by the cathode filter and the anode filter respectively to form the cathode chamber and the anode chamber, and uranium enters the cathode chamber through the cathode filter; or/and, the cathode filter and the anode filter are both nylon filters; or/and, the mesh size of the cathode filter and the anode filter are both 400 mesh.

The one-step method for electrokinetic uranium extraction and separation from a sandstone-type uranium deposit according to the present invention solves the problem that the existing electrokinetic uranium leaching technology cannot achieve the enrichment of uranium with particles of the same charge property on a fixed electrode and the simultaneous separation and purification in one step and has the following advantages:

• • (1) Achieving leaching and separation and purification: The method of the present invention can make uranium in the sandstone-type uranium deposit form only positively charged ions and complexes by controlling the activation environment, thereby realizing the directional migration and enrichment of uranium by utilizing electrophysical effects such as electromigration and electroosmosis, having the effect of efficient and rapid enrichment while requiring reduced amount of leaching agent used; under the action of an external electric field, the counter adsorption is reduced and the uranium extraction efficiency is improved; by using a conductive plastic electrode as a cathode material, the oxidized high-valent uranium cations can be efficiently and selectively reduced, so that the high-valent uranium cations are selectively reduced on the surface of the cathode conductive plastic electrode, and the conductive plastic electrode also has the advantages of weak electrolysis, corrosion resistance, and low energy consumption. In the present invention, the initial pH of the reaction system is controlled to be low, and the electric field strength is controlled to weaken the electrolysis. Therefore, when the cathode conductive plastic electrode receives electrons and undergoes an electrically-induced reduction, the high-valent uranium cations can be reduced to low-valent insoluble uranium and fixed on the electrode surface, while other impurity metal ions will not be precipitated on the surface of the cathode conductive plastic electrode through hydroxides. At the same time, uranium has a high reduction potential and is reduced and fixed on the surface of the cathode conductive plastic electrode prior to other impurity metal ions, which is beneficial to improving the purity of the enriched uranium and realizing the one-step method for electrokinetic uranium extraction and separation.
  • (2) Reducing the amount of leaching agent used: The present invention utilizes HCl+FeCl₃ as the activating leaching agent, significantly reducing the amount of leaching agent used. FeCl₃ not only provides Fe³⁺ to oxidize UO₂ in the sandstone-type uranium deposit, but also provides Cl⁻. HCl also provides Cl⁻ while maintaining the acidic pH environment of the sandstone-type uranium deposit. The research results show that compared to uranium leaching with H₂SO₄, using HCl+FeCl₃ as the activating leaching agent can control the uranyl ions to only form positively charged complex ions UO₂Cl⁺ with Cl⁻, while preventing further complexation with chloride ions to form negatively charged complexes, thereby reducing the use amount of leaching agent that provides Cl⁻.
  • (3) Improving uranium enrichment efficiency: Under the action of the electric field, positively charged uranium-containing particles including uranyl ions and uranyl complex cations undergo electrophysical effects such as electromigration and electroosmosis, accelerating the enrichment of uranium toward the cathode conductive plastic electrode. In addition, due to the action of the external electric field, the adsorption of positively charged uranium-containing ions by negatively charged mineral particles is weakened, further improving the leaching efficiency of uranium.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart showing a one-step method for electrokinetic uranium extraction and separation from a sandstone-type uranium deposit according to the present invention.

FIG. 2 is a schematic diagram showing the one-step method for electrokinetic uranium extraction and separation from a sandstone-type uranium deposit according to the present invention.

FIG. 3 is a diagram showing a phase equilibrium analysis of uranium deposit under different pH according to the present invention.

Reference numeral: power supply—1; cathode conductive plastic electrode—2; anode conductive plastic electrode—3; cathode chamber—4; anode chamber—5; cathode filter—6; anode filter—7; sandstone-type uranium deposit—8.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts are within the scope of protection of the present invention.

It should be noted that if specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Reagents or instruments used without manufacturer's indication are all commercially available conventional products.

Throughout the present invention, all features, such as values, amounts, contents, and concentrations, specified in numerical ranges or percentage ranges are provided for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to encompass and specifically disclose all possible subranges and individual values within those ranges.

The features described in the present invention may be combined in any manner, and as long as there are no conflicts between the combinations of these features, all possible combinations should be considered within the scope of the present specification. Each feature disclosed in the present specification may be replaced by any alternative feature that provides the same, equivalent, or similar purpose. Therefore, unless otherwise specified, the features disclosed are merely general examples of equivalent or similar features.

Currently, sulfuric acid is the most common leaching agent used to extract uranium from uranium deposit. However, the use of sulfuric acid cause the coexistence of positively charged UO₂²⁺ and negatively charged UO₂(X)₂²⁻ and UO₂(X)₃⁴⁻ particles. Due to their varying charge properties, their migration directions in the electric field also differ, making it impossible to achieve directional and controllable collection of uranium. Furthermore, the use of H₂SO₄ is prone to reaction to generate insoluble matters that block the leaching channels. In addition, the final products are all uranium-containing leachates, which require further processing to remove impurities and refine the uranium. Uranium leachates have complicated compositions, causing the problems of high technical difficulty, complex process, and high cost in uranium purification.

Therefore, the present invention provides a one-step method for electrokinetic uranium extraction and separation from a sandstone-type uranium deposit. Referring to FIG. 1, the uranium activation, electric drive, and selective reduction technologies are combined together. The uranium in the sandstone-type uranium deposit is converted into positively charged uranium, so that it moves toward the cathode conductive plastic electrode 2 under the action of an electric field and then electrically reduced at the cathode conductive plastic electrode 2 to convert the uranium into a low-valent insoluble uranium-containing substance that is precipitated on the surface of the cathode conductive plastic electrode 2, while other impurity metal ions are not precipitated on the surface of the cathode conductive plastic electrode 2 through hydroxides, thereby enriching uranium.

The present invention uses FeCl₃+HCl as a leaching agent, combined with electric drive technology. FeCl₃ not only provides Fe³⁺ to oxidize UO₂ in the sandstone-type uranium deposit, but also provides Cl⁻ to form positively charged complex ions UO₂Cl⁺ with uranyl ions. HCl also provides Cl⁻ while maintaining an acidic pH environment of sandstone-type uranium deposit. This allows only positively charged uranium complexes to form in the sandstone-type uranium deposit, rather than causing the uranium elements in the system to exist as both anions and cations. Thus, after applying an electric field, electrophysical effects such as electromigration and electroosmosis of positively charged uranium-containing particles including uranyl ions and uranyl complex cations can promote the rapid enrichment of uranium in the cathode chamber. Furthermore, under the action of the applied electric field, positively charged species migrate toward the cathode conductive plastic electrode 2, while negatively charged species migrate toward the anode conductive plastic electrode 3. As a result, the adsorption of positively charged uranium ions by negatively charged mineral particles is reduced, further improving the leaching rate of uranium. Furthermore, the energization process not only accelerates the flow of liquid within the deposit but also oxidizes tetravalent uranium that was not oxidized during the activation process, further increasing uranium dissolution. Under low pH and a suitable electric field, the positively charged uranium-containing particles enriched in the cathode chamber are selectively reduced by the cathode conductive plastic electrode, while simultaneously preventing the precipitation of other metallic impurity ions. The positively charged uranium-containing particles are then electrically reduced through electron transfer, resulting in a high-purity uranium-containing precipitate on the surface of the cathode conductive plastic electrode 2.

By using the activating leaching agent of the present invention, the uranium elements in the system exist in the forms of UO₂²⁺, UO₂Cl⁺ formed by the complexation of UO₂²⁺ and Cl⁻, and positively charged particles such as (UO₂)₂OH³⁺, (UO₂)₂(OH)₂²⁺, (UO₂)₃(OH)₄²⁺, and (UO₂)₃(OH)⁵⁺ produced by the hydrolysis of UO₂²⁺.

In addition, the present invention conducted a phase equilibrium analysis in the study. When the pH reaches 4.2, the reaction system will start to produce uranyl hydroxide precipitation, which affects the leaching of uranium elements, referring to FIG. 3. In the technology of the present invention, although under acidic conditions, as the pH increases, the uranium content and impurity rate from cathode electroreduction will be affected. Therefore, the present invention controls the acidic environment to be pH≤3.

The conductive plastic electrodes used in the present invention are both electrically conductive and corrosion-resistant, making them particularly suitable for use in low-pH environments and enabling more economical extraction and purification of uranium elements from a sandstone-type uranium deposit. For example, the electrokinetic geosynthetic (EKG) electrodes described in Chinese Patent CN118724422A may be used, but other conductive plastic electrodes may also be used without being limited thereto.

The following is a detailed description of the one-step method for electrokinetic uranium extraction and separation from a sandstone-type uranium deposit provided by the present invention through Embodiments 1 to 17.

Embodiment 1

A one-step method for electrokinetic uranium extraction and separation from a sandstone-type uranium deposit, the method including:

5 L of the activating leaching agent FeCl₃+HCl at the pH of 3 is continuously introduced into 1 kg of the sandstone-type uranium deposit with a uranium concentration of 400 g/g, where the FeCl₃ concentration is 10 g/L, and the pH is adjusted with the HCl. During the activation process, some insoluble tetravalent uranium in the deposit is gradually converted into soluble hexavalent uranium, including UO₂²⁺, UO₂Cl⁺ formed by the complexation of UO₂²⁺ and Cl⁻, and positively charged particles such as (UO₂)₂OH³⁺, (UO₂)₂(OH)₂²⁺, (UO₂)₃(OH)₄²⁺, and (UO₂)₃(OH)⁵⁺ produced by the hydrolysis of UO₂²⁺.

The cathode and anode are conductive plastic electrodes and electrically connected to the negative and positive electrodes of a power supply 1, respectively. A 400-mesh nylon anode filter 7 is placed between the anode conductive plastic electrode 3 and the sandstone-type uranium deposit 8, forming an anode chamber 5. A 400-mesh nylon cathode filter 6 is placed between the sandstone-type uranium deposit 8 and the cathode conductive plastic electrode 2, forming a cathode chamber 4, as shown in FIG. 2. After 24 hours of activation, a stable direct current with a voltage gradient of 0.5 V/cm is introduced for 24 hours. This current not only accelerates the flow of liquid within the deposit but also oxidizes tetravalent uranium that was not oxidized during the activation process, further enhancing uranium dissolution. Uranium elements first electrochemically migrate to the cathode conductive plastic electrode 2 in the form of positively charged particles. Subsequently, uranium elements are selectively reduced on the surface of the cathode conductive plastic electrode 2. Through charge transfer between the electrode surface and the charged particles, hexavalent uranium in the positively charged uranium-containing particles is electrochemically reduced to tetravalent uranium, which precipitates on the surface of the cathode conductive plastic electrode 2 as UO₂. After the power was turned off, elution and measurement are conducted, and it is found that the uranium attached to the cathode conductive plastic electrode 2 weighs 307.6 mg, accounting for 76.9% of the total uranium content of the sandstone-type uranium deposit used in the experiment.

Embodiment 2

A one-step method for electrokinetic uranium extraction and separation from a sandstone-type uranium deposit, basically the same as that in Embodiment 1, except that:

The pH of the activating leaching agent used is 2. It is finally found that the uranium attached to the cathode conductive plastic electrode 2 weighs 337.2 mg, accounting for 84.3% of the total uranium content of the sandstone-type uranium deposit used in the experiment.

Embodiment 3

A one-step method for electrokinetic uranium extraction and separation from a sandstone-type uranium deposit, basically the same as that in Embodiment 1, except that:

The pH of the activating leaching agent used is 1. It is finally found that the uranium attached to the cathode conductive plastic electrode 2 weighs 350.0 mg, accounting for 87.5% of the total uranium content of the sandstone-type uranium deposit used in the experiment.

Embodiment 4

A one-step method for electrokinetic uranium extraction and separation from a sandstone-type uranium deposit, basically the same as that in Embodiment 1, except that:

The pH of the activating leaching agent used is 0.5. It is finally found that the uranium attached to the cathode conductive plastic electrode 2 weighs 356.8 mg, accounting for 89.2% of the total uranium content of the sandstone-type uranium deposit used in the experiment.

Embodiment 5

A one-step method for electrokinetic uranium extraction and separation from a sandstone-type uranium deposit, basically the same as that in Embodiment 2, except that:

The volume of the activating leaching agent FeCl₃+HCl used is 1 L. It is finally found that the uranium attached to the cathode conductive plastic electrode 2 weighs 261.6 mg, accounting for 65.4% of the total uranium content of the sandstone-type uranium deposit used in the experiment.

Embodiment 6

A one-step method for electrokinetic uranium extraction and separation from a sandstone-type uranium deposit, basically the same as that in Embodiment 5, except that:

The volume of the activating leaching agent FeCl₃+HCl used is 3 L. It is finally found that the uranium attached to the cathode conductive plastic electrode 2 weighs 289.2 mg, accounting for 72.3% of the total uranium content of the sandstone-type uranium deposit used in the experiment.

Embodiment 7

A one-step method for electrokinetic uranium extraction and separation from a sandstone-type uranium deposit, basically the same as that in Embodiment 5, except that:

The volume of the activating leaching agent FeCl₃+HCl used is 8 L. It is finally found that the uranium attached to the cathode conductive plastic electrode 2 weighs 345.2 mg, accounting for 86.3% of the total uranium content of the sandstone-type uranium deposit used in the experiment.

Embodiment 8

A one-step method for electrokinetic uranium extraction and separation from a sandstone-type uranium deposit, basically the same as that in Embodiment 5, except that:

The volume of the activating leaching agent FeCl₃+HCl used is 10 L. It is finally found that the uranium attached to the cathode conductive plastic electrode 2 weighs 360.4 mg, accounting for 90.1% of the total uranium content of the sandstone-type uranium deposit used in the experiment.

Embodiment 9

A one-step method for electrokinetic uranium extraction and separation from a sandstone-type uranium deposit, basically the same as that in Embodiment 2, except that:

The concentration of the FeCl₃ in the activating leaching agent used is 15 g/L. It is finally found that the uranium attached to the cathode conductive plastic electrode 2 weighs 348.8 mg, accounting for 87.2% of the total uranium content of the sandstone-type uranium deposit used in the experiment.

Embodiment 10

A one-step method for electrokinetic uranium extraction and separation from a sandstone-type uranium deposit, basically the same as that in Embodiment 9, except that:

The concentration of the FeCl₃ in the activating leaching agent used is 20 g/L. It is finally found that the uranium attached to the cathode conductive plastic electrode 2 weighs 357.2 mg, accounting for 89.3% of the total uranium content of the sandstone-type uranium deposit used in the experiment.

Embodiment 11

A one-step method for electrokinetic uranium extraction and separation from a sandstone-type uranium deposit, basically the same as that in Embodiment 2, except that:

The voltage gradient applied between the cathode and anode electrodes is 0.1 V/cm. It is finally found that the uranium attached to the cathode conductive plastic electrode 2 weighs 281.2 mg, accounting for 70.3% of the total uranium content of the sandstone-type uranium deposit used in the experiment.

Embodiment 12

A one-step method for electrokinetic uranium extraction and separation from a sandstone-type uranium deposit, basically the same as that in Embodiment 11, except that:

The voltage gradient applied between the cathode and anode electrodes is 0.2 V/cm. It is finally found that the uranium attached to the cathode conductive plastic electrode 2 weighs 298.0 mg, accounting for 74.5% of the total uranium content of the sandstone-type uranium deposit used in the experiment.

Embodiment 13

A one-step method for electrokinetic uranium extraction and separation from a sandstone-type uranium deposit, basically the same as that in Embodiment 11, except that:

The voltage gradient applied between the cathode and anode electrodes is 0.3 V/cm. It is finally found that the uranium attached to the cathode conductive plastic electrode 2 weighs 316.8 mg, accounting for 79.2% of the total uranium content of the sandstone-type uranium deposit used in the experiment.

Embodiment 14

A one-step method for electrokinetic uranium extraction and separation from a sandstone-type uranium deposit, basically the same as that in Embodiment 11, except that:

The voltage gradient applied between the cathode and anode electrodes is 0.4 V/cm. It is finally found that the uranium attached to the cathode conductive plastic electrode 2 weighs 323.6 mg, accounting for 80.9% of the total uranium content of the sandstone-type uranium deposit used in the experiment.

Embodiment 15

A one-step method for electrokinetic uranium extraction and separation from a sandstone-type uranium deposit, basically the same as that in Embodiment 2, except that:

The voltage gradient applied between the cathode and anode electrodes is 1.0 V/cm. It is finally found that the uranium attached to the cathode conductive plastic electrode 2 weighs 327.6 mg, accounting for 81.9% of the total uranium content of the sandstone-type uranium deposit used in the experiment.

Embodiment 16

A one-step method for electrokinetic uranium extraction and separation from a sandstone-type uranium deposit, basically the same as that in Embodiment 15, except that:

The voltage gradient applied between the cathode and anode electrodes is 1.5 V/cm. It is finally found that the uranium attached to the cathode conductive plastic electrode 2 weighs 314.4 mg, accounting for 78.6% of the total uranium content of the sandstone-type uranium deposit used in the experiment.

Embodiment 17

A one-step method for electrokinetic uranium extraction and separation from a sandstone-type uranium deposit, basically the same as that in Embodiment 15, except that:

The voltage gradient applied between the cathode and anode electrodes is 2.0 V/cm. It is finally found that the uranium attached to the cathode conductive plastic electrode 2 weighs 265.2 mg, accounting for 66.3% of the total uranium content of the sandstone-type uranium deposit used in the experiment.

Table 1 shows the conditions of various embodiments of the present invention and the amount of uranium electro-reduced by the cathode conductive plastic electrode

							Percentage of
			FeCl3	Activating	Electrokinetic	Voltage	uranium electro-
	Solid-liquid	pH	concentration	extraction	extraction	gradient	reduced by	Impurity
Embodiment	ratio(kg:L)	value	(g/L)	time(h)	time(h)	(V/cm)	cathode(%)	rate

1	1:5	3	10	24	24	0.5	76.9%	1.6%
2	1:5	2	10	24	24	0.5	84.3%	1.3%
3	1:5	1	10	24	24	0.5	87.5%	0.6%
4	1:5	0.5	10	24	24	0.5	89.2%	0.3%
5	1:1	2	10	24	24	0.5	65.4%	4.5%
6	1:3	2	10	24	24	0.5	72.3%	2.1%
7	1:8	2	10	24	24	0.5	86.3%	1.0%
8	1:10	2	10	24	24	0.5	90.1%	0.8%
9	1:5	2	15	24	24	0.5	87.2%	1.1%
10	1:5	2	20	24	24	0.5	89.3%	0.9%
11	1:5	2	10	24	24	0.3	70.3%	0.4%
12	1:5	2	10	24	24	0.2	74.5%	0.6%
13	1:5	2	10	24	24	0.3	79.2%	0.7%
14	1:5	2	10	24	24	0.4	80.9%	1.1%
15	1:5	2	10	24	24	1.0	81.9%	10.4%
16	1:5	2	10	24	24	1.5	78.6%	16.2%
17	1:5	2	10	24	24	2.0	66.3%	21.3%

As can be seen from Table 1, in Embodiments 1-4, when the solid-liquid ratio is 1:5, the FeCl₃ concentration is 10 g/L, the activation extraction time is 24 h, and then the electrokinetic extraction time is 24 h under the voltage gradient of 0.5 V/cm, the amount of uranium precipitated on the cathode conductive plastic electrode 2 by electroreduction increases as the pH value decreases, with reduced impurity rate and improved uranium purity. The solid-liquid ratio of Embodiment 2 is different from those of Embodiments 5-8, as the solid-liquid ratio decreases, the amount of uranium precipitated by electroreduction gradually increases and the impurity rate decreases. The FeCl₃ concentration of Embodiment 2 is different from those of Embodiments 9 and 10, trivalent iron ions function as the oxidant for tetravalent uranium in the activation process, as the FeCl₃ concentration increases, the amount of uranium precipitated by electroreduction gradually increases and the impurity rate decreases. The voltage gradient of Embodiment 2 is different from those of Embodiments 11-17, as the voltage gradient increases within the range of 0.1 V/cm to 0.5 V/cm, the amount of uranium precipitated by electroreduction significantly increases, and the content of other impurity elements in the precipitate on the cathode surface is relatively low, that is, at the low voltage gradient of 0.1 V/cm to 0.5 V/cm, applying the present invention to perform one-step electrokinetic extraction from a sandstone-type uranium deposit cam produce a high-purity uranium-containing precipitate on the cathode. Embodiments 15-17 show the extraction and separation effects at a higher voltage gradient, at a high voltage gradient, the amount of uranium precipitated by electroreduction on the cathode surface significantly decreases with the increase of the voltage gradient, and the impurity rate also increases, which may be caused by the change in system pH due to electrolysis. Therefore, in practical applications, it is necessary to take into consideration the electrolysis situation at a high voltage gradient. The intense electrolysis of the cathode causes the significant increase in pH of the cathode liquid and triggers the formation of a large amount of hydroxide precipitation of other metal elements. They precipitate into the cathode liquid or adhere to the cathode surface, reducing the uranium extraction rate and purity. However, using a low voltage gradient can achieve high and pure uranium extraction and separation effects while saving electricity.

At the same pH, the activating leaching agent of the present invention requires less amount of HCl compared to uranium leaching with H₂SO₄. The present invention utilizes HCl+FeCl₃ as the activating leaching agent, resulting in the formation of only positively charged uranium complexes in the sandstone-type uranium deposit. Under the action of electric current, the adsorption of uranium ions by mineral particles is reduced, further improving the leaching rate of uranium. High-valent uranium complexes undergo electrophysical effects such as electromigration and electroosmosis, migrating continuously toward the cathode chamber and being selectively reduced on the surface of the cathode conductive plastic electrode. Furthermore, in the present invention, the initial pH of the reaction system is controlled to be low, and the electric field strength is controlled to weaken the electrolysis. Therefore, when the cathode receives electrons and undergoes an electrically-induced reduction, high-valent uranium cations can be reduced to low-valent insoluble uranium and fixed on the electrode surface, while other impurity metal ions will not be precipitated on the cathode surface through hydroxides. At the same time, uranium has a high reduction potential and is reduced and fixed on the surface of the cathode conductive plastic electrode prior to other impurity metal ions, which is beneficial to improving the purity of the enriched uranium and realizing the one-step method for electrokinetic uranium extraction and separation.

Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description is not intended to limit the present invention. After reading the above description, various modifications and substitutions of the present invention will become apparent to those skilled in the art. Therefore, the scope of protection of the present invention should be defined by the appended claims.