KR20150133568A - System and method for purifying rare earth mine drainage - Google Patents

Abstract

The present invention relates to a treatment system and a method for rare earth material mine drainage. According to the present invention, the treatment system for the rare earth material mine drainage comprises: a mine drainage supplying part (10) supplying the rare earth material mine drainage; a heavy metal processing part (20) including a precipitation reactor (21) where the mine drainage is supplied to and a alkali supply medium (24) removing the heavy metals by precipitation from the mine drainage supplied into the precipitation reactor; a radioactive substance processing part (30) including an absorbing reactor (31) where a primarily processed water in which the heavy metals are removed is supplied to and an absorbent (32) absorbing and removing radioactive substances from the primarily processed water supplied in the absorbing reactor; and an organic material processing part (40) where a secondarily processed water in which the radioactive substances are eliminated is supplied so as to removing organic materials from the secondarily processed water.

Description

FIELD OF THE INVENTION The present invention relates to a rare earth mine drainage treatment system,

The present invention relates to a rare earth mine drainage treatment system, and more particularly, to a rare earth mine drainage treatment system and method for purifying heavy metals, radioactive materials, and organic substances contained in mine drainage generated when extracting rare earth elements.

Rare earth metals are a group of 17 elements including lanthanides from atomic number 57, lanthanum from lanthanum (La) to lanthanum (71), scandium (Sc), and yttrium (Y) do. Because of its unique physical and chemical properties, rare earth metals are used in a wide variety of applications such as optical glass, abrasives, fluorescent materials, pigments, magnetic materials, metal additives, and ceramics in all industrial fields such as metals, chemicals and materials. . Regarding this, in the rare earth producing countries such as China, they are trying to mineralize these metals, and in 2010, Korea designated the rare earth as a new strategic mineral.

The main characteristics of the rare earth production process are as follows. First, since rare earths are usually present as ionic compounds, they require a relatively complicated purification process, which requires considerable skill. Second, a lot of strong chemicals are used for extraction, and therefore a large amount of harmful wastewater is generated during the extraction process. Third, since rare earth metals have properties that exist together with radioactive elements, radioactive contamination also occurs in large quantities. In other words, severe environmental pollution occurs in the mining and extraction process, and the reprocessing and purification process is costly. Therefore, a new rare earth metal refining technology that can reduce environmental pollution is needed to secure the rare earth metals safely.

Extraction techniques for recycling rare earth metals have been proposed in response to these circumstances. Currently, there are about 20 kinds of minerals containing rare earth metals. However, monazite, bastnasite, allanite and xenotime can be used industrially as ore. In the case of monazite and xenotime, concentrated sulfuric acid method and alkali method are commercialized for extraction of rare earth metals from ore. The concentrated sulfuric acid process can be treated at low cost, but the pollution problem is relatively severe, while the alkaline process requires an autoclave and is costly and has the advantage of recovering soda ash. On the other hand, the bastnasite leaching method after roasting is used as the main extraction process.

On the other hand, rare earth mine drainage occurs when extracting rare earth metals, which include various heavy metals, radioactive materials, and organic matter.

In other words, since rare earth mine drainage contains various pollutants, it can not be discharged or reused as it is. Therefore, the rare earth extraction technology requires a technique for purification of rare earth mine drainage.

The conventional rare earth mine drainage treatment method usually involves only precipitation of heavy metal ions using an alkali agent. In the wastewater, not only heavy metals but also radioactive substances and organic substances are present together. Since radioactive substances and organic substances are difficult to be removed in the precipitation treatment process due to alkalization, a state in which a large amount of radioactive substances and organic substances exist is purified.

Patent No. 10-0500730 Patent No. 10-1058567

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a method for removing rare earth mine pollutants by removing all heavy metals, radioactive substances and organic substances, And to provide a rare earth mine drainage treatment system and method capable of recovering high purity water.

The rare earth mine drainage treatment system according to the present invention comprises: a mine drainage supplying unit for supplying a rare earth mine drainage generated during the extraction of rare earths and containing heavy metals, radioactive materials and organic matter; A precipitation reactor connected to the mine drainage supply unit and supplied with mine drainage, an alkaline supply medium for trapping heavy metals in the cation from the rare earth mine drainage supplied into the precipitation reactor, A heavy metal processing unit; An adsorption reactor connected to the precipitation reactor of the heavy metal treatment unit and supplied with the primary treatment water from which the heavy metal is removed through the heavy metal treatment unit, an anion from the primary treatment water supplied into the adsorption reactor, And an adsorbent for adsorbing and removing the radioactive substance of the radioactive substance; And an organic matter treatment unit connected to the adsorption reactor of the radioactive substance treatment unit and supplied with the secondary treatment water from which the radioactive substance is removed through the radioactive substance treatment unit to remove organic matter from the secondary treatment water.

A method for treating a rare earth mine drainage according to the present invention comprises: a first step of supplying a rare earth mine drainage generated during the extraction of rare earths and containing heavy metals, radioactive materials and organic matter; The rare earth mine drainage supplied through the first step is supplied to the precipitation reactor and the alkaline supply medium is loaded into the precipitation reactor to precipitate the heavy metals of the cation from the rare earth mine drainage through the alkali reaction between the alkali supply medium and the rare earth mine drainage A second step of removing the liquid; A third step of supplying the primary treated water from which the heavy metal is removed through the second step to an adsorption reactor containing the adsorbent to remove the anion radioactive material contained in the primary treated water through the adsorbent; And a fourth step of removing organic matter from the secondary treatment water from which the radioactive material has been removed through the third step and recovering the purified water.

According to the rare earth mine drainage treatment system and method of the present invention, it is possible to remove all heavy metals, radioactive substances and organic substances, which are impurities of different characteristics included in the rare earth mine drainage generated upon extraction of rare earth elements, Since highly purified water is recovered, there is an effect of preventing environmental pollution caused by purified water containing pollutants and reducing the cost for purification treatment of pollutants.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a system for processing wastewater generated during the extraction of a rare earth element according to the present invention and a treatment process thereof. FIG.
2 is a schematic view of an adsorption reactor applied to a rare earth mine drainage treatment system according to the present invention.
3 is a process chart of a method for treating rare earth mine drainage according to the present invention.

The rare earth mine drainage treatment system according to the present invention as shown in FIG. 1 is a system for treating a heavy metal of a cation from a mine drainage (wastewater generated at the time of extracting a rare earth element) supply unit 10 and a mine drainage supply unit 10, A radioactive material processing unit 30 for processing the radioactive material of negative ions from the primary treatment water (heavy water treated wastewater) that has passed through the heavy metal processing unit 20 and the heavy metal processing unit 20 and the radioactive material processing unit 30 And an organic matter treatment section 40 for treating organic matter from one secondary treatment water (wastewater treated with radioactive material).

The mine drainage supply unit 10 includes a supply tank 11 for storing rare earth mine drainage (hereinafter abbreviated as "mine drainage") generated upon extraction of rare earths, a pump 12 for transferring the mine drainage stored in the supply tank 11 And a supply pipe 13 for supplying the mine drainage conveyed by the pump 12 to the heavy metal processing unit 20 and a valve for opening and closing the supply pipe 13 are connected together Lt; / RTI > The feed tank 11 may be equipped with a stirrer for stirring the mine drainage.

The heavy metal processing unit 20 processes the heavy metals (Pb, Cd, Cu, Zn, Mn, etc.) of positive ions contained in the mine drainage and the fluorine F of the anions by precipitation, U, etc.) are processed together.

The heavy metal processing unit 20 includes a precipitation reactor 21 having a space therein and an alkali supply medium 24 as a medium for precipitation of heavy metals.

The settling reactor 21 has a tank structure having an inlet port 22 for the introduction of the mineral wastewater and a discharge port 23 for the primary treatment water and is equipped with an alkali supply medium input port for charging the alkali supply medium A retractable door is constructed and a drain port for discharging the sediment is constituted. The precipitation reactor 21 may be composed of, for example, a precipitation reactor body having upper and lower openings, and an upper and lower covers respectively coupled to upper and lower portions of the precipitation reactor body.

In the drawing, the inlet port 22 is formed so as to face upward from the bottom, and the discharge port 23 is formed to be laterally directed from the top, but is not limited thereto.

The alkali supply medium 24 is used in an amount within the precipitation reactor 21, and the amount of the alkali supply medium 24 varies depending on the contamination concentration of the heavy metal.

It is widely known that the alkali supply medium is a mixture of CaO and CaCO ₃ , and CaO is changed into an alkali substance by reacting with water. Alkaliization (pH 9 - 9) of heavy metals (Pb, Cd, Cu, Zn, Mn, 12) to precipitate. The CaO and CaCO ₃ are mixed in an amount of 95 to 98% by weight and 2 to 5% by weight, respectively. If the ratio is out of this range, it is difficult or long to control the pH of the heavy metal. CaCO ₃ is an alkaline substance that, when mixed with CaO, supplies alkali for longer.

In order to improve the reactivity of the alkali supply medium 24 with heavy metals and the alkali production ability, the alkali supply medium 24 is used by impregnating the air stones (particulate material having voids) with an alkali agent. The particle size of the air stone is 20 ~ 30mm in diameter. That is, the alkali supply medium 24 is composed of the air stone 24a and the reaction layer 24b of the alkali agent impregnated in the pores of the air stone 24a.

The packing density of alkali feed medium is 50 ~ 60kg / ㎥ (recommended condition: 56kg / ㎥).

The alkali feed medium is used by injecting 0.6-0.9g of alkaline agent (recommended condition: 0.7g) into the internal standard (Φ 6mm ㅧ H18mm, volume 0.51mL) which can impregnate the alkali feed medium per one air stone.

The radioactive material processing unit 30 is disposed inside the adsorption reactor 31 and the adsorption reactor 31 connected to the precipitation reactor 21 of the heavy metal processing unit 20 through a pipeline and contains primary treatment water (PU _CMDS , Polyurethane Coal Mine drainage sludge) for adsorbing and removing the radioactive material contained in the waste water (treated wastewater).

As shown in FIGS. 1 and 2, the adsorption reactor 31 includes, for example, an adsorption reactor main body 31a having upper and lower openings, upper and lower covers 31b And 31c, and a sealing ring made of rubber or the like is used for ensuring watertightness. Further, the discharge port 34 of the primary treatment water, the discharge port 34 of the secondary treatment water (the waste water from which the radioactive material is adsorbed and removed), and the drain port of the radioactive substance are constituted, The present invention is not limited thereto.

The adsorbent 32 is contained in the adsorption reactor 31. The primary treatment water flowing into the adsorption reactor 31 passes through the adsorbent 32 and adsorbs the anion radioactive material. The adsorbent 32 can be contained as a single space, but the adsorption performance can be improved by forming a plurality of adsorption spaces by containing the adsorbent 32 in two or more stages through one or more shelves 35, . The shelf 35 may be formed of a mesh or the like that is porous for securing the flow of water and does not lose the adsorbent 32.

The adsorbent 32 uses sludge as a by-product, which is a byproduct generated in the coal mine drainage treatment, and preferably has a particle size of 1 to 3 μm. By making the waste sludge recyclable, it is possible to reduce the disposal cost of the waste and prevent environmental pollution caused by the waste.

The adsorbent 32 is made of sludge, methylene diphenyl diisocyanate (MDI), and polyol. The MDI and polyol are used for sludge to have pores for adsorbing radioactive material.

The adsorbent 32 is used in a weight ratio of particulate sludge: MDI: polyol of 2: 0.9-1.1: 0.9-1.1, preferably 2: 1: 1, which is a ratio for improving the adsorption performance with optimum porosity formation to be.

The process for producing the adsorbent 32 is as follows.

1. Material mixing and void formation.

1 to 3 탆 sludge and MDI and polyol are put into a stirrer at the above ratio and stirred at a temperature of 20 to 25 ° C at a speed of 80 to 120 rpm for 20 to 40 minutes and preferably at a speed of 100 rpm for 30 minutes, The CO ₂ in the sludge on the particulate matter is blown off to form a void.

The stirring speed and time are conditions for uniform mixing of materials and formation of voids. If the above conditions are not satisfied, the porosity is low and the adsorption performance is deteriorated or the material is destroyed.

2. Drying.

A drying process is performed to stabilize the adsorbent workpieces that have formed voids through the whole process.

Drying conditions are 2 hours and 30 minutes to 3 hours and 30 minutes (recommended conditions: 3 hours) at room temperature (20 to 25 ° C).

3. Processing.

The dried adsorbent can be processed to a wide range of particle sizes and it is subjected to crushing, crushing and particle size sorting processes in order to process the adsorbent having a particle size of 1 to 3 μm, which is the initial particle size of the sludge.

The adsorbent 32 has a porosity of 0.5 to 0.6 (recommended condition: 0.57) and a packing density of 600 to 650 kg / m 3 (recommended condition: 617 kg / m 3).

Table 1 shows the characteristics of the adsorbent thus prepared.

Properties Data Bulk density (g mL ^-1 ) 0.24 pH 7.68 pHZPC 5.8 BET surface area (m ² g ^-1 ) 23.0 Pore size (nm) 48 Goethite (wt.%)
Calcite (wt.%)
SO ₄ ^2- (wt.%) 60.67
16.33
5.11 Surface strength 1 GPa

The organic material treatment unit 40 removes organic matter using ozone, and includes an ozone generator 41, an ozone reactor 42 for removing ozone contained in the secondary treatment water, ).

The ozone generator 41 is a known product and supplies ozone to the ozone reactor 42. The ozone treatment efficiency for the secondary treated water was 39.3 mg COD _Cr / g O ₃ .

The ozone reactor 42 is a tank having a space therein and can have a variety of structures such as the structure of the precipitation reactor 21 and the adsorption reactor 31 described above. The ozone reactor 42 has an ozone introduction port, a purified water discharge port, a drain port, Can be configured. A purifier may be provided together with the purifier for purifying ozone discharged through the ozone discharging unit.

The organic material treatment unit 40 is not limited to the ozone generator 41, and any structure that removes organic matter such as a photocatalytic sterilizer may be used.

The present invention can be equipped with a sensor for detecting the characteristics of mine drainage, primary treatment water, secondary treatment water, and purified water (flow rate, temperature, etc.). In addition to the structure of the mine drainage supply unit 10, a pump for the flow of the primary treatment water, the secondary treatment water, and the purified water can be provided.

The method of treating rare earth mine drainage according to the present invention comprises precipitation treatment of heavy metals - radioactive material treatment - organic matter treatment process, and each process is as follows.

(S10) Rare earth mine drainage supply.

The rare earth mine drainage generated in the extraction of rare earths is a mixture of water, heavy metals, radioactive materials, organic materials and the like. The mine drainage stored in the supply tank 11 is supplied to the precipitation reaction unit (21).

(S20) Heavy metal precipitation treatment.

An alkali supply medium 24 is contained in the precipitation reactor 21 and mine drainage is supplied to the precipitation reactor 21 of the heavy metal processing unit 20.

The mine drainage reacts with the reactive layer of the alkaline agent in the alkali feed medium 24, during which the alkaline agent reacts with the water to increase the pH so that the heavy metal of the cation is precipitated in the precipitation reactor 21 (in this process, Also precipitates). The residence time (HRT) of mine drainage is 2 hours and 30 minutes to 3 hours and 30 minutes (recommended conditions: 3 hours). The conditions of the precipitation reaction are 22 ~ 28 ℃ (recommended condition: 25 ℃).

The mine drainage initially supplied through this process is divided into heavy metal precipitate and primary treated water.

Table 2 below shows the treatment mechanism of heavy metals by this step.

(S30) Treatment of radioactive materials.

(S20) After the heavy metal precipitation treatment step, the primary treated water treated with the heavy metal is supplied to the adsorption reactor 31 of the radioactive substance treatment unit 30. [ The adsorbent (32) is contained in the adsorption reactor (31).

The primary treated water reacts with the adsorbent 32. In this process, the radioactive material contained in the primary treated water is adsorbed by the adsorbent 32 and removed from the primary treated water.

The deposit retention time (EBCT) for the adsorption reaction is from 50 minutes to 70 minutes (recommended conditions: 60 minutes).

When the present process is completed, the radioactive substance [adsorbed to the adsorbent 32] and the secondary treatment water (water, organic matter) are separated.

(S40) Organic matter treatment.

The second treated water is supplied to the inside of the ozone reactor 42 and the ozone generated by the ozone generator 41 is supplied to the inside of the ozone reactor 42 to remove the organic matter to generate purified water. The residence time (HRT) for ozone treatment is 2 hours and 30 minutes to 3 hours and 30 minutes.

In the rare earth mine drainage treatment method according to the present invention, mine drainage supply, heavy metal treatment, radioactive material treatment and organic material treatment may be performed stepwise or flowwise.

<Examples>

1. Rare earth mine drainage supply.

The amounts of heavy metals, radioactive materials and organic matter in rare earth mine drainage are shown in Table 3 below. The flow rate of rare earth mine drainage used in this experiment is 20 L / day.

2. Treatment of heavy metals.

The alkali supply medium 24 is an alkali material mixed with 97% CaO and 3% CaCO ₃ by weight, impregnated with particulate matter (air stone) having a particle size of 22 mm, and has a packing density of 56 kg / m 3.

The alkaline supply medium was treated with heavy metals of cations at a residence time of mine drainage of 3 hours.

3. Radioactive material handling unit.

Absorbent 32 has a 2㎛ of sludge and MDI and polyol particle diameter based on the weight of 2: Prepare in a ratio of 1, and put in a stirrer as the ratio was stirred for 30 minutes at a speed of 100rpm discharging the CO ₂ from the process: 1 Pores were formed. The porosity is 0.57. The activity volume is 0.833L.

After drying for 3 hours, the adsorbent having a particle size of 2 mu m was prepared through particle size selection. The packing density is 617 kg / m3.

The radioactive material was removed from the primary treated water in which heavy metal was removed by using the thus-prepared adsorbent 32, and the radioactivity was removed by setting the deposit time to 1 hour. At pH 5, adsorption performance and reaction rate were found to be the highest.

4. Ozone Organic Oxidation.

A known ozone organic oxidation apparatus was used. Ozone was supplied to the secondary treatment water from which the radioactive material was removed, and the organic matter was removed with a residence time of 3 hours. When ozone was used for the oxidation of organic matter, the pH was 6.5-7.2 and the temperature was 20-25 ° C.

The results are shown in Table 3. The results are shown in Table 3. &lt; tb &gt;&lt; TABLE &gt;

R1 is the result after the heavy metal treatment process using the alkali feed medium, R2 is the result after the radioactive substance treatment process using the adsorbent, and R3 is the result after the organic substance treatment process by the ozone oxidation.

As can be seen from Table 3, the treatment of rare earth mine drainage according to the present invention shows that both heavy metals, radioactive materials and organic matter are significantly reduced compared with the raw water.

10: mine drainage supply section, 11: mine drainage supply section
12: pump, 20: heavy metal processing unit
21: precipitation reactor, 24: alkali feed medium
30: Radioactive substance treatment section, 31: Adsorption reactor
32: adsorbent, 40: organic matter treatment section
41: ozone generator, 42: ozone reactor

Claims (4)

A mine drainage supplying unit 10 for supplying a rare earth mine drainage which is generated during the extraction of rare earths and contains heavy metals, radioactive materials and organic matter;
A sedimentation reactor (21) having a space formed therein and connected to the mine drainage supply unit and supplied with mine drainage; a precipitation reactor (21) containing the cationic heavy metal from the rare earth mine drainage supplied into the precipitation reactor A heavy metal treatment section 20 composed of an alkali supply medium 24;
An adsorption reactor (31) connected to the precipitation reactor of the heavy metal treatment unit and supplied with the primary treatment water from which the heavy metal is removed through the heavy metal treatment unit, and a primary treatment A radioactive material processing unit 30 comprising an adsorbent 32 for adsorbing and removing radioactive material from water;
And an organic matter treatment unit (40) connected to the adsorption reactor of the radioactive substance treatment unit and supplied with the secondary treatment water from which the radioactive substance has been removed through the radioactive substance treatment unit to remove organic matter from the secondary treatment water. Mine drainage treatment system. The rare earth mine drainage treatment system according to claim 1, wherein the adsorption reactor is divided into two or more stages through a porous shelf, and the adsorbent is contained in the shelf so that two or more adsorption treatments are performed. The adsorbent according to claim 1 or 2, wherein the adsorbent is sludge having a particle size of 1 to 3 μm, methylene diphenyl diisocyanate (MDI) and polyol in a weight ratio of 2: 0.9 to 1: 1.1: 0.9 to 1.1. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt; A first step of supplying a rare earth mine drainage generated during the extraction of rare earths and containing heavy metals, radioactive materials and organic matter;
The rare earth mine drainage supplied through the first step is supplied to the precipitation reactor, the alkali supply medium is loaded in the precipitation reactor, and the heavy metals of the cation are removed from the rare earth mine drainage by the reaction between the alkali supply medium and the rare earth mine drainage A second step of:
A third step of supplying the primary treated water from which the heavy metal is removed through the second step to an adsorption reactor containing the adsorbent to remove the radioactive material contained in the primary treated water through the adsorbent;
And a fourth step of removing organic matter from the secondary treatment water from which the radioactive material has been removed through the third step to recover the purified water.

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