KR20200059977A - Method for removing uranium by using iron sulfide minerals and oxidizing agents - Google Patents

Abstract

The present invention relates to a method for removing uranium in an aqueous solution which adds oxidizing agents to groundwater containing iron sulfide minerals to simply reduce a concentration of uranium in the aqueous solution, particularly ground water, so as to be immediately applied to a site since additional processes or devices are not required. According to the present invention, the method for removing uranium in an aqueous solution comprises the steps of: preparing an aqueous solution containing iron sulfide minerals; and adding oxidizing agents to the aqueous solution containing the iron sulfide minerals.

Description

Method for removing uranium using iron sulfide mineral and oxidizing agent {METHOD FOR REMOVING URANIUM BY USING IRON SULFIDE MINERALS AND OXIDIZING AGENTS}

Disclosed herein is a method for removing uranium using iron sulfide minerals and oxidizing agents.

In most developed countries, groundwater is used as a representative water resource and is researched and developed as an important part of the water industry. However, in the case of Korea, where surface water is used as the most water resource, groundwater pollution is reported as a serious level due to poor regulation and management of groundwater.

Specifically, in Korea, groundwater pollution progressed due to various causes such as heavy metals such as cadmium, copper, and arsenic, and oils and organic solvents. Recently, groundwater contamination problems have been raised by radioactive materials such as uranium and radon, and according to the Ministry of Environment, natural radioactive materials such as uranium have been reported to exceed the standard in some areas where groundwater is used for drinking water.

As a biological effect of the radioactive material, tissues may be damaged or deteriorated when excessive exposure to alpha rays, beta rays, gamma rays, and x rays emitted by uranium may cause genetic modification of germ cells. In order to solve this problem, research and development of a technology for removing radioactive materials is required.

On the other hand, the groundwater moves along the pores in the ground layers or rocks. Most of the igneous metamorphic rocks in the domestic rock formations contain iron and sulfide minerals. Iron sulfide minerals exist as Fe ^{2 +} and SO ₄ ^2- in aqueous solution, and easily act as electron donors due to the high reactivity of Fe ^{2 +} , resulting in oxidation and reduction reactions with surrounding pollutants through the generated electrons and adsorption. And inorganic contaminants including uranium through precipitation.

Existing domestic uranium removal technology is focused on equipment and process methods such as ion exchange resin removal, membrane filtration and synthetic activated carbon. This method has high efficiency in removing uranium, but has disadvantages of high cost and hassle of field application from the viewpoint of installation and management of the device.

In addition, there is a method of removing uranium in the groundwater using activated carbon, but this is a method of synthesizing and manufacturing most of the activated carbon and adding it to the groundwater, and there is a hassle of going through a separate activated carbon processing process.

Korean Open Patent No. 10-2015-0039531 Korean Open Patent No. 10-2010-0097426

In one aspect, the object of the present invention is to effectively remove uranium in an aqueous solution using iron sulfide minerals and oxidizing agents, thereby economically purifying an aqueous solution containing uranium, particularly ground water, without a separate device or complicated process.

In one aspect, the present invention comprises the steps of preparing an aqueous solution containing an iron sulfide mineral; And adding an oxidizing agent to the aqueous solution containing the iron sulfide mineral.

In one aspect, according to the present invention, by simply adding an oxidizing agent to the groundwater containing iron sulfide mineral, it is possible to easily reduce the concentration of uranium in an aqueous solution, especially the groundwater, so there is no need for a separate process or device, so it is applied directly to the site It is possible.

In another aspect, the method for removing uranium in an aqueous solution of the present invention, especially when removing uranium in groundwater, uses iron sulfide minerals naturally present in the underground environment and uses a relatively economical oxidant, thereby reducing cost when removing uranium. Can have

1 is a result showing the reaction (Py) with an aqueous solution of uranium when only pyrite is present without an oxidizing agent, and a reaction with an aqueous solution of uranium (Py_Ox) when pyrite and sodium hypochlorite are present together.
FIG. 2 shows XRD results for analyzing the composition of the remaining precipitate after decanting the supernatant after reacting pyrite and sodium hypochlorite with an aqueous uranium solution for 48 hours.

Term Definition

In the present specification, when a part “includes” a certain component, it means that the component may further include other components, rather than excluding other components, unless otherwise specified.

Exemplary Of implementations  Explanation

Hereinafter, the present invention will be described in detail.

In exemplary embodiments of the present invention, preparing an aqueous solution containing an iron sulfide mineral; And adding an oxidizing agent to the aqueous solution containing the iron sulfide mineral.

Unlike the conventional uranium removal technology, which is focused on equipment or process methods, the uranium removal method according to the present invention is uranium removal through chemical treatment. As can be seen from the example kinetic test, when the uranium concentration is 5 mg / L, it has a removal efficiency of 100% within 30 minutes. This is higher than the 99.9% uranium removal efficiency within 6 hours of the conventional invention. In addition, unlike the uranium removal method in which activated carbon is synthesized and manufactured and added to the groundwater, the uranium removal method according to the present invention can be said to be environmentally friendly because it uses the oxidation mechanism of iron sulfide minerals naturally present in the underground environment.

In one embodiment, the iron sulfide mineral may be included in a high liquid ratio (g / mL) of 0.1 g / 16 mL based on the total aqueous solution volume.

In one embodiment, the aqueous solution containing the iron sulfide mineral may be ground water. Most of the igneous metamorphic rocks in domestic rock aquifers contain iron and sulfide minerals, and iron sulphide minerals contained in the groundwater can be used to purify the groundwater by removing uranium in the groundwater.

In one embodiment, the iron sulfide mineral may be one or more selected from the group consisting of pyrite (Pyrite), pyrite (Marcasite), Grezite (Greigite), Troilite (Troilite), and pyrite (Pyrrhotite), Preferably, it may be pyrite (FeS ₂ , purity 99.9%), and more preferably, standard Peruvian pyrite (FeS ₂ , 99.9%).

In this specification, "pyrite" is a mineral of an equiaxed crystal system having the formula of FeS ₂ as a main component of iron sulfide. Specifically pyrite in the present description with (FeS ₂₎ is easily oxidized due to the high reactivity of the Fe ^{2 +} acts as an electron donor. These chemical mechanisms can interact with surrounding contaminants. For example, mechanisms that can be removed through adsorption or coprecipitation with inorganic pollutants such as arsenic or uranium are possible, but are not limited thereto.

In one embodiment, the oxidizing agent is selected from the group consisting of sodium hypochlorite (NaClO), hydrogen peroxide (H ₂ O ₂ ), potassium permanganate (KMnO ₄ ), sodium permanganate (NaMnO ₄ ), and sodium bromate (NaBrO ₃ ). It may be one or more, preferably sodium hypochlorite (NaClO). The method for removing uranium in an aqueous solution according to the present invention can promote the oxidation of iron sulfide minerals contained in an aqueous solution by using an oxidizing agent, so that uranium in an aqueous solution can be removed in a shorter time, which is relatively inexpensive, and thus an economical removal process is possible. .

In this specification, “sodium hypochlorite” has a chemical formula of NaClO, and is a colorless, transparent or pale pale liquid with strong oxidizing and bleaching effects, and is used as a disinfectant in a water treatment plant due to its oxidation characteristics. In addition, it is used for sterilization, disinfection, and deodorant. Specifically, the sodium hypochlorite of the present specification exists as sodium hydroxide (NaOH) and hypochlorous acid (HOCl) when reacted with water, and the oxidizing power of hypochlorous acid (HOCl) produced at this time is excellent.

In one embodiment, the pH of the aqueous solution may be 5.4 or less, for example, 5.3 or less, 5.2 or less, 5.1 or less, 5.0 or less, and when the oxidation conditions are satisfied, on the surface of the iron sulfide mineral, uranium dioxide (UO ₂ ) It can be formed.

Specifically, uranium exists as UO ₂ ²⁺ in an aqueous solution in an oxidation condition with a pH of 5.4 or less. At this time, UO ₂ precipitates may be formed on the pyrite surface by oxidation of iron sulfide minerals, for example, pyrite (FeS ₂ ), thereby reducing uranium concentration. The mechanism involved is as follows.

In the case of the present invention, by using the chemical mechanism, by using an oxidizing agent such as sodium hypochlorite (NaClO), by promoting the oxidation of iron sulfide minerals such as pyrite (FeS ₂ ), focusing on increasing the efficiency of uranium removal I put it.

In one embodiment, the concentration of uranium in the aqueous solution containing the iron sulfide mineral may be 30 μg / L or more. U.S. EPA has a uranium contamination standard concentration of 30 μg / L or more, and in the present invention, it is possible to efficiently remove uranium even at a higher uranium concentration of 5 mg / L.

In one embodiment, the volume ratio of the aqueous solution and the oxidizing agent containing the iron sulfide mineral may be 16: 1, and may exhibit high uranium removal efficiency in a small amount of the oxidizing agent ratio.

Hereinafter, the present invention will be described in more detail through the following examples. However, the following implementations are provided for the purpose of illustration only to aid understanding of the present invention, and the scope and scope of the present invention are not limited thereto.

Example

In connection with the following experiment, the 'inductively coupled plasma emission analyzer (ICP-OES)' was used to analyze the concentration of uranium reduction, and the ICP as described above for the analysis of total iron content by pyrite (FeS ₂ ) oxidation of the present invention -OES analysis equipment was used.

In addition, 'UV-vis spectroscopy' was used to confirm the concentration change of Fe ^{2 +} and SO ₄ ^2- due to oxidation of pyrite (FeS ₂ ).

<Determination of uranium concentration>

According to the U.S. Environmental Protection Agency (EPA), the uranium contamination standard for drinking water is 30 μg / L, and the uranium concentration in areas with severe uranium contamination in domestic groundwater, such as Anseong, Gyeonggi-do, is 55.98 μg / L. Based on this, in the present invention, an uranium removal experiment was performed at an artificial uranium pollution concentration of 5 mg / L, which is higher than the EPA pollution standard and the maximum uranium pollution concentration in domestic groundwater.

<kinetic test>

In order to confirm the effect of removing uranium by time, a kinetic test was performed. The reaction time was set to 5min, 15min, 30min, 1h, 2h, 4h, 6h, 9h, 12h, 24h, 48h, and the supernatant was filtered at each hour to confirm the uranium concentration. Detailed experimental conditions are as follows.

First of 1000mg / L of the sample UO ₂ (NO _{3) 2} was diluted to prepare a uranium solution having a concentration of 5mg / L in the, pyrite (FeS ₂₎ 0.1 g into distilled water 10ml pyrite (FeS ₂₎ suspension 0.1 g / a 10ml in It was prepared. Thereafter, 0.1g / 10ml of the prepared pyrite (FeS ₂ ) suspension was added to 11 50ml conical tubes for each hour, and 5ml of the 5mg / L uranium solution prepared above was added in the batch experiment. Thereafter, 1 ml of 0.1M sodium hypochlorite (NaClO) as an oxidizing agent was added in the order of 48 h samples to 5 min samples, and reacted at 150 rpm at 25 ° C using a shaker. Therefore, 10 ml of the prepared pyrite (FeS ₂ ) suspension, 5 ml of uranium aqueous solution and 1 ml of oxidizing agent sodium hypochlorite (NaClO) are reacted, so that the total volume is 16 ml, and the solid-liquid ratio of pyrite is 0.1 based on the total volume of the reaction aqueous solution. It can be said to be g / 16ml.

In addition, in order to verify the effect of removing uranium by the oxidizing agent, a sample without an oxidizing agent was prepared for each time and reacted at 25 ° C. and 150 rpm as in the above, and the results are shown in FIG. 1.

Referring to FIG. 1, it was confirmed that the concentration was reduced by adsorbing and removing uranium on the pyrite surface within an initial 30-minute time period, and after 30 minutes, the concentration increased again as uranium returned to the ionic state by desorption. . In addition, the uranium concentration over time was maintained almost constant under the condition where no oxidizing agent was added.

The decrease in concentration from the initial concentration of 5 mg / L to about 1.6 mg / L was due to the total volume being diluted to 15 ml by the pyrite suspension added, and uranium was not removed by any other mechanism.

That is, as a result of experimenting through 48h, when oxidizing agent was added (Py_Ox), uranium concentration reduction by pyrite (FeS ₂ ) was more excellent, and only pyrite (FeS ₂ ) and uranium were reacted without adding oxidizing agent. In the case (Py), it was confirmed that the reduction of uranium concentration by pyrite (FeS ₂ ) did not occur and that the process of adding the oxidizing agent had a great effect on the reduction of uranium concentration.

<UO ₂  Confirmation of sediment formation>

To demonstrate the production of UO ₂ through a chemical mechanism, X-ray Diffraction (XRD), which is used in the compositional analysis of minerals, was used. The XRD sample analyzed the sample Py_Ox in which oxidizing sodium hypochlorite (NaClO) was added to pyrite (FeS ₂ ), because the best effect of reducing uranium was obtained when pyrite and oxidizing agent were added together.

Referring to FIG. 2, it was possible to qualitatively know that UO ₂ was generated through the oxidation / reduction of pyrite and uranium, and it was confirmed that uranium was converted to a UO ₂ precipitate by the above-described chemical mechanism.

Claims (8)

Preparing an aqueous solution containing iron sulfide minerals; And
A method of removing uranium in an aqueous solution, including; adding an oxidizing agent to the aqueous solution containing the iron sulfide mineral. According to claim 1,
The aqueous solution containing the iron sulfide mineral is characterized in that the ground water, uranium removal method in the aqueous solution. According to claim 1,
The iron sulfide mineral is at least one selected from the group consisting of pyrite (Pyrite), pyrite (Marcasite), Grezite (Greigite), Troyite (Troilite), and pyrite (Pyrrhotite), uranium in aqueous solution How to remove. According to claim 1,
The oxidant is at least one selected from the group consisting of sodium hypochlorite (NaClO), hydrogen peroxide (H ₂ O ₂ ), potassium permanganate (KMnO ₄ ), sodium permanganate (NaMnO ₄ ), and sodium bromate (NaBrO ₃ ). A method for removing uranium in an aqueous solution. According to claim 1,
The pH of the aqueous solution containing the iron sulfide mineral is characterized in that less than 5.4, uranium removal method in the aqueous solution. According to claim 1,
A method for removing uranium in an aqueous solution, characterized in that uranium dioxide (UO ₂ ) is formed on the surface of the iron sulfide mineral. According to claim 1,
The uranium removal efficiency of the method for removing uranium in the aqueous solution is characterized in that when the initial concentration is 5 mg / L, it is 100% within 30 minutes. According to claim 1,
The volume ratio of the aqueous solution containing the iron sulfide mineral and the oxidizing agent is 16: 1, wherein the method of removing uranium in the aqueous solution.

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