KR101290658B1 - Method for separating selenium using iron oxides - Google Patents

Abstract

The present invention relates to a method for separating selenium using iron oxide, specifically, adjusting the pH of an aqueous solution containing selenite and selenate to 7 to 10 (step 1); Adsorbing selenite contained in the aqueous solution of step 1 using iron oxide (step 2); And washing the iron oxide to which selenite is adsorbed in step 2 with an aqueous alkali solution having a pH of 11 to 13 to elute the adsorbed selenite (step 3). . Separation method of selenium using iron oxide according to the present invention can be separated by adsorbing selenium which is an essential element to humans and harmful action when excessive intake, in particular by selenium and selenium mixed in the state It can be adsorbed and separated to obtain selenium in which only selenite or selenate is concentrated.

Description

Separation method of selenium using iron oxide {Method for separating selenium using iron oxides}

The present invention relates to a method for separating selenium using iron oxide.

Selenium is a toxic nonmetallic element whose chemical properties are similar to those of cognate sulfur and tellurium on the periodic table, and the gray metallic state is known to be stable. Since selenium has been used as a replacement for manganese during World War I, today it has been used in a wide range of applications, including electronics, pigments, photographs, X-ray rectifiers, photovoltaic cells, and alloys. In particular, recently known as an important component of the antioxidant enzymes to protect the human body cells and is known to be effective in reducing the mortality caused by lung cancer, colon cancer, prostate cancer. However, selenium was an element that was classified as a toxic element before the 1950s. In 1935, the 'alkali' disease, which was found in the western Rocky Mountains of the United States and where cattle and cow hair and hoofs fell out, was found to be caused by an excessive intake of selenium, and was found in the human body, such as arsenic, barium, chromium, and mercury nickel. It is classified as a hazardous metal that has harmful effects on organs. In fact, if the concentration of selenium in the blood is more than 1 mg / L is a state called selenosis, symptoms include gastrointestinal disorders, hair loss, white spots of nails and mild nerve damage. In addition, excessive ingestion of foods grown in areas with high selenium content in the soil may cause hair loss, dizziness, fatigue, changes in nails and toenails, abdominal pain, diarrhea, rashes and cirrhosis. Long-term overdose can also lead to increased cholesterol and cancer. However, contrary to the previous claim that only the toxicity of selenium was recently emphasized, the World Health Organization and the Food and Agriculture Organization of the United Nations recognized selenium as an essential nutrient, and the recommended intake of humans was 50 to 200 μg. / Day. A deficiency of selenium in the body can cause cancer in the liver, dysfunction, premature ejaculation, digestive or excretory organs, and excessive intake of selenium over 750 μg / day results in head and teeth loss and increased fatigue. Cause.

On the other hand, selenium is selenide (Se (-II)), metal selenium (Se (0)), selenite (selenite, Se (IV)) and selenate (selenate, Se (VI)) in nature. It is mainly present as a compound having four different oxidation numbers, and selenide compounds such as FeSe, CaSe and CuSe and metal selenium have very low solubility. However, selenate and selenite not only have high solubility but also exist as anions in the aqueous solution, and thus have low adsorption force on the underground rock, and thus may have high mobility.

On the other hand, even if selenium does not exist as Se (0) or Se (-II) with low solubility but as Se (IV) or Se (VI) with high solubility, the disposal container is corroded at the radioactive waste disposal site. The presence of iron oxides can reduce their mobility. In particular, iron oxides such as hematite, goethite, and magnetite are expected to adsorb the anion Se (IV) or Se (VI), and in fact MnFe ₂ O ₄ , hematite, goethite A study has been published using iron compounds to adsorb selenium without the distinction between Se (IV) or Se (VI) species. However, according to the above results, it is difficult to separate and separate Se (IV) and Se (VI), and iron oxides such as magnetite adsorb both Se (IV) and Se (VI) under acidic conditions. There is a problem in that the pH solution does not adsorb both species.

Therefore, the present inventors while adsorbing and separating selenium, while studying a separation method that can be selectively adsorbed depending on the species of selenium, a method for separating selenite and selenate using iron oxide and alkaline aqueous solution And developed the present invention.

An object of the present invention to provide a selenium separation method using iron oxide.

In order to achieve the above object, the present invention comprises the steps of adjusting the pH of the aqueous selenium solution containing selenite and selenate to 7 to 10 (step 1); Adsorbing selenite contained in the aqueous selenium solution of step 1 using iron oxide (step 2); And washing the iron oxide to which selenite is adsorbed in step 2 with an aqueous alkali solution having a pH of 11 to 13 to elute the adsorbed selenite (step 3). .

Separation method of selenium using iron oxide according to the present invention can be separated by adsorbing selenium which is an essential element to humans and harmful action when excessive ingestion, in particular selenium and selenium mixed in the selenite state adsorption Separation allows selenium or selenate to yield concentrated selenium.

1 is a schematic view showing a selenium separation device according to the present invention.

The present invention

Adjusting the pH of the aqueous selenium solution including selenite and selenate to 7 to 10 (step 1);

Adsorbing selenite contained in the aqueous selenium solution of step 1 using iron oxide (step 2); And

The selenite-adsorbed iron oxide in step 2 is washed with an alkaline aqueous solution having a pH of 11 to 13 to elute the adsorbed selenite (step 3).

Hereinafter, the separation method according to the present invention will be described in detail for each step.

In the selenium separation method using iron oxide according to the present invention, step 1 is a step of adjusting the pH of the aqueous selenium solution containing selenite and selenate to 7 to 10. The step 1 is to adjust the pH of the aqueous selenium solution containing selenite (Se (IV)) and selenate (Se (IV)) to 7 to 10 to form a condition suitable for adsorption, the selenite in the step 1 By adjusting the pH of the aqueous selenium solution containing nitrate and selenate to 7 to 10, iron oxide selectively adsorbs selenite only, and does not adsorb selenate, thereby separating the two species. If the pH of the selenium solution is less than 7, there is a problem that selenate is adsorbed together and the selenite cannot be separated and adsorbed. If the pH of the selenium solution exceeds 10, the adsorption efficiency of selenite is lowered. There is a problem.

The pH adjustment of step 1 may be performed using sodium hydroxide and hydrochloric acid, and may be performed by appropriately selecting an acid and a basic solution.

In the selenium separation method using iron oxide according to the present invention, step 2 is a step of adsorbing selenite contained in the selenium aqueous solution of step 1 using iron oxide. In step 2, iron selenite is adsorbed to the column filled with iron oxide in the selenium aqueous solution, the pH of which is adjusted to 7 to 10 in step 1 using iron oxide, and selenate passes through the column as it is and evaporates water in the aqueous solution. Only selenate can be concentrated. Although selenite is relatively less mobile than selenate, selenium is mainly present as selenite under reducing conditions such as groundwater, so in order to remove selenium from contaminated groundwater, the selenite is removed using iron oxide. Adsorb knight.

At this time, the iron oxide of step 2 may be used, such as magnetite, ferrite (ferrite), hematite, goethite, magnetite (maghemite), it is preferable to use magnetite. When the iron oxides have a pH in the range of 7 to 10, selenite is adsorbed, but selenate is not adsorbed, so the selenite and selenate mixed therein may be classified and adsorbed and separated. This is because the iron oxides have a high partition coefficient (K _d ) value for selenite in the pH range of the above range.

In the selenium separation method using iron oxide according to the present invention, step 3 is a step of eluting the adsorbed selenite by washing the iron oxide adsorbed with selenite in step 2 with an aqueous alkali solution having a pH of 11 to 13. . In order to elute selenite from the iron oxide adsorbed only selenite in step 2, in step 3, selenite is eluted and separated by washing the iron oxide adsorbed with selenite using an alkaline aqueous solution having a pH of 11 to 13. do. The selenite is used to adsorb the iron oxide in the pH range of 7 to 10, but not adsorbed in the pH range of 11 to 13, so that selenite is separated from the iron oxide and eluted in the aqueous alkali solution.

At this time, the aqueous alkali solution may be used ammonia water, sodium hydroxide, sodium carbonate aqueous solution, sodium hydrogen carbonate aqueous solution, and the like, selecting an appropriate aqueous alkali solution.

The separation method according to the present invention recovers toxic selenite and selenate from an aqueous solution of selenium, and in particular, separates and concentrates selenite and selenate separately. Accordingly, selenium can be separated and concentrated more effectively than the conventional method in which selenium is separated by adsorption without separating selenite and selenate.

On the other hand, the present invention is a column provided with a filter at the bottom;

Iron oxide charged to the top of the filter of the column; And

While injecting the sample solution to the iron oxide, it provides a separation device that can perform the separation method including a sample injection unit for adjusting the pH of the injected sample solution to 7 to 10.

A schematic diagram of the separator is shown in FIG.

Referring to the schematic diagram of Figure 1, the separation device according to the present invention is a column equipped with a filter for preventing the outflow of iron oxide in the bottom, the iron oxide is filled to the upper filter of the column adsorbed selenium and the iron oxide top It includes a sample injection unit for injecting the sample liquid. The sample solution containing selenium is injected into the iron oxide filled in the column through the sample injection unit, so that selenium in the sample solution is adsorbed to the iron oxide. Thereafter, the iron oxide to which the selenium is adsorbed is washed with an aqueous alkali solution, and thus selenium may be separated from the iron oxide to separate and concentrate selenium.

In this case, the filter may be a filter made of a material such as polyethylene sulfone, cellulose acetate, nitrocellulose.

In addition, the iron oxide packed in the column may be used magnetite, ferrite, hematite, goethite, maghite, etc., it is preferable to use magnetite. Since the iron oxides adsorb selenite but not selenate, selenite and selenate, which are generally mixed, can be classified and adsorbed and separated. This is because the iron oxides have a high distribution coefficient (K _d ) with respect to selenite, so that only selenite can be fractionated and adsorbed.

In addition, the sample solution is an aqueous selenium solution containing selenite and selenate, it is preferable to adjust the pH to 7 to 10 to form a condition suitable for adsorption on the iron oxide. By adjusting the pH of the selenium aqueous solution containing selenite and selenate to 7 to 10, only selenite can be fractionated and adsorbed to iron oxide, and selenate is not adsorbed and is concentrated and separated in the state contained in the sample liquid. Can be. If the pH of the selenium aqueous solution containing selenite and selenate is less than 7, there is a problem that selenate is adsorbed to the iron oxide together to separate and selenite only selenite, the pH of the selenium aqueous solution is 10 When it exceeds, there exists a problem that the adsorption efficiency of selenite falls.

The selenite can be adsorbed and concentrated through the separator according to the present invention, and in particular, selenite and selenate can be separated and separated.

Hereinafter, the present invention will be described more specifically by way of examples. However, the following examples are intended to illustrate the present invention, but the scope of the present invention is not limited by the following examples.

<Example 1> Separation of selenite and selenate using iron oxide 1

Step 1: pH was adjusted to 9.0 by adding hydrochloric acid or sodium hydroxide to each of the selenite and selenate aqueous solutions having a concentration of selenium of 1 × 10 ⁻⁵ mol / L.

Step 2: Each of the selenite and selenate aqueous solutions adjusted to pH 9.0 in step 1 was injected into each separator filled with 300 mg of magnetite powder as shown in FIG. 1 in an amount of 1 mL. Thereafter, the separator was washed four times using 1 mL of 1 × 10 ⁻² mol / L sodium perchlorate solution. At this time, the solution from the separator was collected and the concentration of selenium in the solution was measured using ICP-MS (Inductively Coupled Plasma-Mass Spectrometry).

Step 3: In step 2, a sodium hydroxide solution having a pH of 12 was added in an amount of 2, 2 and 1 mL using a separator filled with magnetite adsorbed with selenium. At this time, the sodium hydroxide solution passed through the separator was collected and the concentration of selenium in the solution was measured using ICP-MS. The results of performing the ICP-MS measurement in step 2 and step 3 are shown in Table 1 below.

<Example 2> Separation of selenite and selenate using iron oxide 2

Example 1 was carried out in the same manner as in Example 1, except that pH was adjusted to 7.0 by adding hydrochloric acid or sodium hydroxide to the selenite and selenate aqueous solution in Step 1 of Example 1. At this time, the results of performing ICP-MS measurement in step 2 and step 3 are shown in Table 1 below.

<Example 3> Separation of selenite and selenate using iron oxide 3

Step 1: To pH 1 9.0 by dropwise addition of hydrochloric acid and sodium hydroxide to 1x10 ^-5 mol / L aqueous solution of selenium containing selenite and selenate in a concentration ratio of 1: 1, 1: 2, and 2: 1, respectively. Adjusted.

Step 2: 1 mL of a mixture of selenite and selenate with pH adjusted to 9.0 in step 1 was injected into each separator filled with 300 mg of magnetite powder as shown in FIG. Then, the separator was washed four times with 1 × 10 ⁻² mol / L sodium perchlorate solution. At this time, the solution from each separator was collected and the concentration of selenium in the solution was measured by ICP-MS.

Step 3: The adsorbed selenium was eluted by washing the magnetite by adding a sodium hydroxide solution having a pH of 12 in an amount of 2, 2 and 1 mL, respectively, using a separator filled with magnetite adsorbed with selenium in step 2. At this time, the sodium hydroxide solution passed through the separator was collected and the concentration of selenium in the solution was measured using ICP-MS. The results of performing the ICP-MS measurement in step 2 and step 3 are shown in Table 1 below.

Example 4 Separation of Selenate and Selenate Using Iron Oxide 4

In step 1 of Example 3, hydrochloric acid and sodium hydroxide were added dropwise with 1 × 10 ^-5 mol / L aqueous solution of selenium mixed with selenite and selenate at a concentration ratio of 1: 1, 1: 2, and 2: 1, respectively. The selenite and selenate were separated in the same manner as in Example 3 except that the pH was adjusted to 7.0. At this time, the results of performing ICP-MS measurement in step 2 and step 3 are shown in Table 1 below.

<Example 5> Separation of selenite and selenate using iron oxide 5

The selenite and selenate were separated in the same manner as in Example 3 except that ferrite powder was used instead of magnetite as the adsorbent in Step 2 of Example 3. At this time, the results of measuring the concentration of selenium in the solution from each separator in steps 2 and 3 by ICP-MS is shown in Table 1 below.

Selenium solution and concentration injected into the column Eluted in stage 2
Amount of selenium (%) Eluted in step 3
Amount of selenium (%) Selenite
solution
(mol / L) Selenate
solution
(mol / L) Mixed solution 1
(mol / L) Mixed solution 2
(mol / L) Mixed solution 3
(mol / L) Example 1 1 × 10 ^-5 0 0 0 0 5 95 0 1 × 10 ^-5 0 0 0 > 99 <0.2 Example 2 1 × 10 ^-5 0 0 0 0 3 97 0 1 × 10 ^-5 0 0 0 > 99 <0.2 Example 3 0 0 1 × 10 ^-5 0 0 49 51 0 0 0 1 × 10 ^-5 0 70 30 0 0 0 0 1 × 10 ^-5 27 63 Example 4 0 0 1 × 10 ^-5 0 0 47 53 0 0 0 1 × 10 ^-5 0 67 33 0 0 0 0 1 × 10 ^-5 31 69 Example 5 0 0 1 × 10 ^-5 0 0 46 54 0 0 0 1 × 10 ^-5 0 67 33 0 0 0 0 1 × 10 ^-5 32 68

(The mixed solution 1, the mixed solution 2, and the mixed solution 3 are selenium aqueous solutions in which selenite and selenate are mixed in concentration ratios of 1: 1, 1: 2, and 2: 1, respectively.)

As shown in Table 1, it can be seen from Examples 1 and 2 that iron oxides such as magnetite adsorb most of the selenite while not adsorbing selenate. In addition, it can be seen that iron oxide selectively adsorbs only selenite even in the solution in which the selenite and selenate of Examples 3 to 5 are mixed. In addition, it can be seen from the results shown in Table 1 that the selenite adsorbed on the iron oxide in Step 3 of Examples 1 to 5 are all desorbed by the sodium hydroxide solution at pH 12. Therefore, it can be seen that the selenate and selenite can be effectively separated and recovered through the separation method according to the present invention.

Experimental Example 1 Analysis of Adsorption Characteristics of Iron Oxide in the Presence of Anions

In order to analyze the adsorption characteristics of iron oxides in the presence of anions such as fluoride ions, carbonate ions, and silicate ions, which are commonly present in nature, sodium carbonate (Na ₂ CO ₃ ), sodium fluoride (NaF), or sodium silicate ( Na ₂ SiO ₃ ) was added to the solution in which the selenite was dissolved, and then the selenite was adsorbed using the magnetite. The magnetite adsorbed selenium was analyzed, and the results are shown in Table 2 below.

Selenite injection volume
(mol / L) Sodium carbonate
(mol / L) Sodium fluoride
(mol / L) Sodium silicate
(mol / L) pH Selenium amount adsorbed on iron oxide (%) 1 × 10 ^-5 - - - 9.1 98.3 1 × 10 ^-5 1 x 10 ^-3 - - 9.1 95.9 1 × 10 ^-5 - 1 × 10 ^-4 - 6.92 98.6 1 × 10 ^-5 - 1 x 10 ^-3 - 6.96 98.4 1 × 10 ^-5 - 1 × 10 ^-4 - 9.93 96.2 1 × 10 ^-5 - 1 x 10 ^-3 - 9.93 95.5 1 × 10 ^-5 - - 1 x 10 ^-3 9.1 58.1 1 × 10 ^-4 - - 1 x 10 ^-3 9.0 39.6

As shown in Table 2, when sodium carbonate and sodium fluoride are added and carbonate or fluorine ion is present, it can be seen that the adsorption amount of magnetite adsorbed selenite does not change significantly. However, when sodium silicate is added and silicate ion exists, it turns out that selenite adsorb | sucks to magnetite and the amount of selenite adsorption decreases rapidly. Accordingly, when selenite and selenate are separated and separated by the separation method according to the present invention, selenite should be adsorbed and separated using an excessive amount of iron oxide in consideration of the concentration of silicate ions in the solution.

Claims (7)

delete delete delete A column having a filter at the bottom;
Ferrite iron oxide charged onto the filter of the column; And
The selenium separation device including a sample injecting portion of the iron oxide, including a selenite and selenate and injecting a sample liquid adjusted to a pH of 7 to 10.
The selenium separator according to claim 4, wherein the filter is made of polyethylene sulfone, cellulose acetate or nitrocellulose.
The selenium separation device according to claim 4, wherein after the injection of the sample solution, an aqueous alkali solution having a pH of 11 to 13 is injected into the sample injection unit.
7. The selenium separator according to claim 6, wherein the aqueous alkali solution is at least one member selected from the group consisting of aqueous ammonia, sodium hydroxide, sodium carbonate and sodium bicarbonate.

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