A method for regenerating an organic phase poisoned by radioactive elements during rare earth smelting and separation

Abstract

A method for regenerating an organic phase poisoned by radioactive elements during the rare earth smelting and separation process. Aiming at the problem that the organic extractant is poisoned by radioactive elements after high-concentration hydrochloric acid stripping during the rare earth smelting and separation process, a high-efficiency regeneration method is proposed. The method uses a purifier of high-acidity phosphoric acid to regenerate the organic phase containing uranium and thorium, removes radioactive elements such as uranium and thorium in the organic phase, restores its extraction capacity, and achieves efficient regeneration. This method solves the problem of decreased extraction capacity of the organic phase extractant due to the accumulation of uranium and thorium radioactive elements after repeated use in the rare earth smelting and separation process, as well as the excessively high content of radioactive elements in the final product. It can reduce the uranium and thorium content by more than 99% at one time, and restore the rare earth extraction capacity by more than 30%.

Description

Technical Field

[0001] The invention belongs to the technical field of rare earth extraction, and in particular relates to the technical field of recycling and regeneration of an organic phase poisoned by radioactive elements. Background Art

[0002] At present, the rare earth resources used on a large scale in industry include Baotou mixed rare earth concentrate, Mt. Weld monazite concentrate, seashore placer-type monazite, southern ionic rare earth concentrate, and fluorocarbon cerium ore concentrate. After decomposition (including but not limited to sulfuric acid roasting-water leaching, alkaline decomposition, acid dissolution, oxidative roasting-hydrochloric acid leaching) and purification, a mixed rare earth chloride solution is finally obtained, and the mixed rare earth chloride system is then separated to obtain single rare earths and enriched products.

[0003] Rare earth elements are difficult to separate due to their similar properties. Solvent extraction is generally used. This method is based on the difference in the extraction ability of different rare earth elements in aqueous solution by an organic extractant that is immiscible with aqueous solution. The easily extractable rare earth elements or rare earth element groups are preferentially extracted into the organic phase composed of the extractant and the diluent, and the difficult-to-extract rare earth elements or rare earth element groups are enriched in the aqueous phase. The separation of rare earth elements is achieved through multi-stage and multi-stage extraction and exchange. The general rare earth extraction and separation operation includes four stages: saponification, extraction, washing and stripping to achieve separation. The difficult-to-extract rare earth elements or element groups enter the raffinate, and the easily extractable rare earth elements or element groups enter the stripping solution after stripping the loaded organic phase with high-concentration hydrochloric acid (5-6mol / LHCl).

[0004] In industry, the most commonly used organic extractants for rare earth separation are mainly acidic phosphorus extractants, including P507, P204, C272 and other extractants, which are used to extract and separate rare earth elements in a hydrochloric acid system. The organic phase composed of the extractant and the diluent needs to be recycled. In industrial practice, it is found that the extraction effect of the organic phase will be significantly reduced after being recycled several times, especially the trace radioactive elements thorium and uranium contained in the mixed rare earth chloride (flakes) produced by alkaline decomposition using monazite as raw material. After stripping with hydrochloric acid at a concentration of about 6 mol / L in the stripping section of rare earth extraction and separation, most of them still remain in the organic phase after stripping. After cyclic accumulation, they are gradually enriched in the organic phase, which causes the so-called poisoning. The poisoned organic phase produces blocky crystals during the saponification process, which clog the tank and make it impossible to effectively extract and separate the rare earths, causing its extraction capacity to drop by more than 40%. At the same time, the radioactive elements accumulated in the poisoned organic phase will be released intermittently and enter the single rare earth product at irregular intervals, causing its radioactive impurity content to exceed the standard, which has become a technical problem that plagues this field.

[0005] Due to the accumulation of uranium and thorium radioactive elements in the organic phase, the resulting decrease in the organic phase extraction capacity and the presence of a certain amount of impurities in some products that cannot meet the usage requirements, the industry believes that the treatment of uranium and thorium radioactive elements in the so-called organic phase after stripping is more important.

[0006] In actual production, in order to solve the interference of thorium and uranium radioactive elements in the rare earth extraction and separation process, the main methods used are: using high-concentration hydrochloric acid, or high-concentration hydrochloric acid plus oxalic acid to treat the organic phase.

[0007] The effect of removing thorium and uranium is limited, and the removal rate is less than 10%, causing the organic phase content to continue to increase with recycling. Therefore, it is necessary to adopt an efficient purification method to remove the excessive uranium and thorium elements in the organic phase. Summary of the invention

[0008] The invention provides a method for stripping metal ions from an extractant containing uranium and thorium impurities. The technology uses a phosphoric acid solution purifier to efficiently strip the extractant containing uranium and thorium impurities, so that the extractant obtains extraction capacity regeneration and ensures the continuous extraction effect of the organic phase.

[0009] The present invention provides a method for regenerating an organic phase poisoned by radioactive elements in a rare earth smelting and separation process. The organic phase poisoned by radioactive elements is stirred and mixed with a purifier, and then the organic phase and the purifier are clarified and separated by standing to obtain an organic phase with restored extraction capacity. Furthermore, the organic phase poisoned by radioactive elements is stirred and mixed with the purifier, and then separated by standing. The process steps include continuous operation of continuous liquid inflow and liquid outflow composed of several stages of mixing tanks, and intermittent operation of single-stage stirring, mixing, standing and separation.

[0010] In certain implementations of the present invention, the volume ratio of the organic phase poisoned by the radioactive element to the purifier is 10:1 to 1:10, preferably 3:1 to 1:3.

[0011] In certain implementations of the present invention, the stirring and mixing time is 0.2-3 hours, the standing time is 0.2-1 hour, and the stirring and mixing and standing temperature is 15-70°C.

[0012] In certain implementations of the present invention, the purifier is a 5-10 mol / L pure phosphoric acid solution. The organic phase poisoned by radioactive elements refers to the organic phase obtained after high-acid stripping in the stripping section of the rare earth smelting and separation process, and the total amount of uranium and thorium is between 200ppm and 10000ppm.

[0013] In certain implementations of the present invention, the organic phase poisoned by radioactive elements is a mixture of an acidic phosphorus extractant and a diluent, wherein the acidic phosphorus extractant includes but is not limited to at least one of P507, P204, and C272.

[0014] In certain implementations of the present invention, the total amount of uranium and thorium in the organic phase for recovering the extraction capacity is between 2 ppm and 10 ppm.

[0015] In certain implementations of the present invention, the purifier contains uranium and thorium after being stirred and mixed with the organic phase poisoned by radioactive elements and separated by static separation. A neutral phosphorus extractant is used to comprehensively recycle the uranium and thorium resources of the purifier containing uranium and thorium, and the purifier is reused to treat the poisoned organic phase.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] The invention adopts a high-concentration pure phosphoric acid solution as a purifier. Under high acidity conditions, compared with high-concentration phosphate ions and low-acid organic phase phosphoric acid extractants, inorganic phosphate has a stronger complexing ability for thorium and uranium, and can form a more stable and soluble coordination compound. Under high acid conditions, it can compete with organic phosphorus extractants for thorium and uranium, and obtain a phosphoric acid solution containing uranium and thorium, thereby achieving efficient purification of the organic phase, and no precipitation is generated during the purification process. The purification effect is significant, and the so-called poisoned organic phase with a load of more than 5g / L of thorium and uranium can be purified, and the single purification rate can reach more than 99%.

[0018] After thorium and uranium are treated with a purifier, phosphoric acid containing thorium and uranium is obtained, which can be directly recovered and treated with a conventional neutral extractant to achieve the recovery and purification of uranium and thorium therein. The phosphoric acid from which thorium and uranium have been removed can be returned as a purifier to continue to treat the poisoned blank organic phase, thereby achieving the recycling of phosphoric acid.

[0019] Organic regeneration technology is simple to operate and highly efficient, and can completely solve the problem of radioactive element poisoning of organic matter through a single stirring and purification. DETAILED DESCRIPTION

[0020] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0021] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the prior art can be used. The reagents and other instruments used without specifying the manufacturer are all conventional reagent products that can be purchased commercially. Example 1

[0022] The organic phase poisoned by radioactive elements has a total uranium and thorium content of 1100ppm. A 5.5mol / L phosphoric acid solution is used as a purifier. The organic phase / purifier volume ratio is 2:1. The mixture is stirred for 1 hour at 40°C and allowed to stand for 0.5h. After separation, the organic phase is washed with water to avoid organic phosphoric acid entrainment. The total uranium and thorium content is reduced to 5ppm. After the purification operation, the organic phase's rare earth extraction capacity is increased by 30.5%.

[0023] The phosphoric acid containing thorium and uranium is treated by using TRPO+P204 extraction and separation to extract thorium and uranium, and the obtained phosphoric acid is reused for purification of organic phase poisoned by radioactive elements. Example 2

[0024] The organic phase poisoned by radioactive elements, with a total uranium and thorium content of 1100ppm, was purified continuously in a countercurrent manner in a three-stage extraction tank with a volume ratio of 2:1 and a 5.5mol / L phosphoric acid solution as the purifier, at a temperature of 40°C, a stirring time of 0.5 hours in a single-stage tank, and a standing time of 0.3 hours. After separation, in order to avoid the organic phase from carrying phosphoric acid, water was used to wash the organic phase, and the total uranium and thorium content was reduced to 3ppm. After the purification operation, the organic phase's rare earth extraction capacity increased by 35.4%.

[0025] The phosphoric acid containing thorium and uranium is treated by using TRPO+P204 extraction and separation to extract thorium and uranium, and the obtained phosphoric acid is reused for purification of organic phase poisoned by radioactive elements. Example 3

[0026] The organic phase poisoned by radioactive elements, with a total uranium and thorium content of 8700ppm, was mixed and stirred in a tank for 2 hours at a volume ratio of 3:1 with 8.0mol / L phosphoric acid solution and a temperature of 30°C, and then left to stand for 1 hour. After separation, in order to avoid the organic phase from carrying phosphoric acid, the organic phase was washed with water. After purification, the total uranium and thorium content in the organic phase was 8ppm. After the purification operation, the extraction capacity of the organic phase for rare earths increased by 45%.

[0027] The phosphoric acid containing thorium and uranium is treated by using TRPO+P204 extraction and separation to extract thorium and uranium, and the obtained phosphoric acid is reused for purification of organic phase poisoned by radioactive elements. Example 4

[0028] The organic phase poisoned by radioactive elements, with a total uranium and thorium content of 5000ppm, was treated with 7.0mol / L phosphoric acid solution as the purifier, with an organic phase / purifier volume ratio of 4:1, at a temperature of 30°C, and was mixed and stirred in the tank for 1.5 hours, and then left to stand for 0.5 hours. After separation, in order to avoid the organic phase from carrying phosphoric acid, the organic phase was washed with water. After purification, the total uranium and thorium content in the organic phase was 10ppm. After the purification operation, the organic phase's rare earth extraction capacity increased by 38%.

[0029] The phosphoric acid containing thorium and uranium is treated by using TRPO+P204 extraction and separation to extract thorium and uranium, and the obtained phosphoric acid is reused for purification of organic phase poisoned by radioactive elements.

Claims

1. A method for regenerating an organic phase poisoned by radioactive elements in a rare earth smelting and separation process, characterized in that: The organic phase poisoned by radioactive elements is stirred and mixed with a purifier, and then the organic phase and the purifier are clarified and separated by standing to obtain an organic phase with restored extraction capacity. The purifier is a 5-10 mol / L pure phosphoric acid solution. The organic phase poisoned by radioactive elements is stirred and mixed with the purifier, and then separated by standing. The process steps include continuous operation of continuous liquid inflow and liquid outflow consisting of several stages of mixing tanks, and intermittent operation of single-stage stirring, mixing, standing and separation. The single-stage stirring and mixing time is 0.2-3 hours, the standing time is 0.2-1 hour, and the stirring, mixing and standing temperature is 15-70°C. The organic phase poisoned by radioactive elements refers to an organic phase obtained after high-acid stripping in the stripping section of the rare earth extraction and separation process, and the total amount of uranium and thorium is between 200ppm and 10000ppm. The total amount of uranium and thorium in the organic phase with restored extraction capacity is between 2ppm and 10ppm.

2. The method according to claim 1, characterized in that The volume ratio of the organic phase poisoned by the radioactive element to the purifier is 10:1-1:

10.

3. The method according to claim 2, characterized in that The volume ratio of the organic phase poisoned by the radioactive element to the purifier is 3:1-1:

3.

4. The method according to claim 1, characterized in that The organic phase poisoned by radioactive elements is a mixture of an acidic phosphorus extractant and a diluent, wherein the acidic phosphorus extractant includes but is not limited to at least one of P507, P204, and C272.

5. The method according to claim 1, characterized in that: The purifier contains uranium and thorium after being stirred and mixed with the organic phase poisoned by radioactive elements and separated by static separation. A neutral phosphorus extractant is used to comprehensively recycle the uranium and thorium resources of the purifier containing uranium and thorium, and the purifier is reused to treat the poisoned organic phase.