KR102475153B1 - Recovering Method of Rare Earth Element from Waste Phosphor Powder Using Acid Leaching - Google Patents

Abstract

The present invention performs alkaline roasting on the rare earth elements of waste phosphors, which were difficult to recover due to low leaching efficiency or impossible leaching for general acid leaching reactions, induces alkali chloride reaction, and then performs acid leaching, so that various types of rare earth elements It relates to a method of recovering rare earth elements from a lighting device including a waste phosphor that enables simultaneous recovery of a rare earth element.
The present invention optimizes the alkaline roasting conditions to improve the alkaline salting of rare earth oxides contained in the waste phosphor, and applies the optimized acid leaching conditions to the alkali-fired waste phosphor, so that yttrium and europium contained in the waste phosphor , cerium, terbium, and lanthanum can be simultaneously recovered.

Description

Method for recovering rare earth elements from waste phosphor powder {Recovering Method of Rare Earth Element from Waste Phosphor Powder Using Acid Leaching}

The present invention relates to a method for recovering rare earth elements from waste phosphor powder using an acid leaching process.

Phosphor refers to an aggregate of small crystal particles that emit light due to the impact of an electron beam. According to the composition of the aggregate, there are sulfide, silicate, rare earth, and nitride types, and rare earths used in lighting and flat panel displays (LCD, LED, PDP, etc.) are phosphor rare earths and are used as fluorescent base materials. The rare earth elements contained in the phosphor are mainly optically inactive yttrium (Y) and lanthanum (La) and negative active materials europium (Eu), cerium (Ce), and terbium (Tb) this is used

As a typical lighting fixture using a phosphor, there is a fluorescent lamp. The fluorescent lamp is a gas light emitting lamp, which is prepared by applying the phosphor to the inner wall of a glass tube and putting argon and a small amount of mercury vapor under pressure. In order to recycle waste fluorescent lamps, the collected fluorescent lamps are crushed in a closed state to absorb and separate mercury vapor first, and then iron and aluminum are separated from waste glass using a magnetic separator. The crushed waste glass of the fluorescent lamp is subjected to a pulverizing process to detach glass fragments and phosphors, collect the waste phosphors by sifting through a 325 mesh (#), and further heat-treat to remove residual mercury.

As recycling methods of waste fluorescent lamps, a method of recovering mercury and recycling it as high-purity metallic mercury, a method of sorting and recycling metal, and a method of separating and recycling glass have been developed and used. However, since various types of rare earths included in waste phosphors are used and included in the form of oxides, they have very stable characteristics, and thus there is a limitation in that it is difficult to simultaneously recover various types of rare earths using general leaching methods. In Korean Patent Publication No. 10-2012-0089183, an aqueous solution containing sulfone acid, phosphoric acid, ammonium hydrogen fluoride, and methyl salicylate is used as a peeling solution and applied to the inside of the waste fluorescence. A technique for washing the phosphor etc. has been described, but the technique only physically separates the phosphor and glass, and is not a technique for leaching and separating the phosphor, so there is a limit to recovery.

The patents and references mentioned herein are incorporated herein by reference to the same extent as if each document were individually and expressly specified by reference.

Korean Patent Publication No. 10-2012-0089183 Korean Patent Publication No. 10-2010-0082812

Yoon Oh-seop, Seoul Urban Research Vol. 9 No. 3 2008.9. Special Feature -invited Article- pp.35-42 Tan, Q., Li, J., & Zeng, X., Critical Reviews in Environmental Science and Technology, 45(7), 749-776, (2015). B.K. Kim, Push forward pilot program to recycle the waste LED lamp, http://www.ohmynews.com/NWS_Web/Articleview/article_print.aspx?cntn_cd=A0002633986(2020)Tunsu, C., Ekberg, C., Retegan, T ., Hydrometallurgy, Vol.144-145, 91-98 (2014). De Michelis, I., Ferella, F., Varelli, E. F., Veglio, F., Treatme, Experimental and process analyses, Waste Management, 31(12), 2559-2568 (2011). Rabah, M. A., Waste Management, 28(2), 318-325 (2008). H. Y. Kim, Recovery of Yttrium from Spent Fluoresent Lamp Phosphors by hydrometallurgy process, 13-28, Ewha Womans University Graduate School, Seoul, Korea (2016). Y. J. Song, Journal of the Korean Institute of metal and materials, 46(11). 755-762 (2018).

An object of the present invention is to obtain waste phosphor fine powder from lighting and flat panel displays (LCD, LED, PDP, etc.) using phosphor, and a method of simultaneously recovering various types of rare earth elements by alkaline roasting and leaching with strong acid. is in providing

Other objects and technical features of the present invention are presented more specifically by the following detailed description, claims and drawings.

The present invention is a method for recovering rare earth elements from a lighting device including waste phosphors, comprising: a first step of obtaining a fine powder of waste phosphors after crushing the lighting device including waste phosphors; A second step of alkali-roasting the waste phosphor fine powder at 900 to 1100° C. for 2 to 4 hours; A third step of adding strong acid to the alkali-roasted waste phosphor micropowder to prepare a waste phosphor micropowder-strong acid reaction solution and reacting at 50 to 60° C. to simultaneously leach rare earth elements; and

A fourth step of recovering rare earth elements from the waste phosphor fine powder-strong acid reaction solution from which the rare earth elements are leached;

The rare earth element is yttrium, europium, cerium, terbium, or lanthanum, and the closed phosphor fine powder has a diameter of less than 700 μm.

The alkaline roasting is characterized in that it is carried out by adding any one or a mixture of two or more selected from the group consisting of sodium carbonate, sodium hydroxide, potassium carbonate, and potassium hydroxide in an amount 1.5 to 3 times the weight of the waste phosphor fine powder. The strong acid is any one or a mixed acid of two or more selected from the group consisting of hydrochloric acid (HCl), nitric acid (HNO ₃ ), and sulfuric acid (H ₂ SO ₄ ), and is characterized in that its concentration is 0.2 to 0.4N.

The present invention performs alkaline roasting on the rare earth elements of waste phosphors, which were difficult to recover due to low leaching efficiency or impossible leaching for general acid leaching reactions, induces alkali chloride reaction, and then performs acid leaching, so that various types of rare earth elements It relates to a method of recovering rare earth elements from a lighting device including a waste phosphor that enables simultaneous recovery of a rare earth element.

The present invention optimizes the alkaline roasting conditions to improve the alkaline salting of rare earth oxides contained in the waste phosphor, and applies the optimized acid leaching conditions to the alkali-fired waste phosphor, so that yttrium and europium contained in the waste phosphor , cerium, terbium, and lanthanum can be simultaneously recovered.

1 shows the result of X-ray diffraction analysis of the particulate phosphor isolated from the waste fluorescent lamp of the present invention.
Figure 2 shows the results of scanning electron microscopy analysis of particulate phosphors isolated from the waste fluorescent lamp of the present invention.
Figure 3 shows the leaching test system for the waste phosphor of the present invention.
4 shows the result of leaching the waste phosphor powder of the present invention into a 3N hydrochloric acid solution.
5 shows that the waste phosphor powder of the present invention is hydrochloric acid (HCl), sulfuric acid (SO ₄ ), nitric acid (HNO ₃ ), aqua regia (3HCl+HNO ₃ ), and mixed acid (1H ₂ SO ₄ +1C ₆ H ₈ O ₇ ) shows the result of elution.
6 shows the result of Y leached by leaching the waste phosphor of the present invention by hydrochloric acid at various concentrations.
7 shows the results of Y leached by leaching the waste phosphor of the present invention by 3N hydrochloric acid at 20 ° C, 50 ° C or 80 ° C.
8 shows the results of analyzing rare earth elements present in the reaction solution in which the waste phosphor of the present invention was subjected to alkaline roasting and then leached with 1 liter of 0.6 N sulfuric acid solution at 50 ° C for 2 hours.
9 shows the result of calculating the leaching rate of each rare earth element in which the waste phosphor of the present invention was alkaline-roasted with sodium carbonate and leached in sulfuric acid.
10 shows the result of calculating the leaching rate of each rare earth element in which the waste phosphor of the present invention was alkaline-roasted with sodium carbonate for a predetermined time and leached in sulfuric acid.
11 shows the result of calculating the leaching rate of each rare earth element, which was subjected to a leaching reaction in sulfuric acid after alkaline roasting was performed with the waste phosphor of the present invention and a predetermined amount of sodium carbonate.

The present invention is a method for recovering rare earth elements from a lighting device including waste phosphors, comprising: a first step of obtaining a fine powder of waste phosphors after crushing the lighting device including waste phosphors; A second step of alkali-roasting the waste phosphor fine powder at 900 to 1100° C. for 2 to 4 hours; A third step of adding strong acid to the alkali-roasted waste phosphor micropowder to prepare a waste phosphor micropowder-strong acid reaction solution and reacting at 50 to 60° C. to simultaneously leach rare earth elements; and a fourth step of recovering rare earth elements from the waste phosphor fine powder-strong acid reaction solution from which the rare earth elements are leached.

The waste phosphor of the lighting device including the waste phosphor is applied to the inside of the glass of the lighting device, and can be obtained by disassembling the lighting device to separate metal components and rubbing the inside of the glass to detach from the surface. The waste phosphor can be obtained in the form of a fine powder, and can be obtained as a fine powder having a diameter of less than 700 μm using a 3255 mesh. When the waste phosphor is separated using a 325 mesh, residual glass fragments are removed. If the diameter of the fine powder of the waste phosphor exceeds 700 μm, the specific surface area is small and heavy, and thus the reactivity during the leaching reaction may be reduced.

The waste phosphor contains rare earth elements. The rare earth element is characterized in that it is yttrium, europium, cerium, terbium, or lanthanum, and exists in a very stable state as an oxide.

According to one embodiment of the present invention, the rare earth element in an oxide state has a disadvantage in that the amount of leaching through a general strong acid leaching unit is small. In particular, terbium oxide and lanthanum oxide had very low leaching efficiency using strong acid, making recovery using acid leaching impossible. Accordingly, in the present invention, the acid leaching efficiency was increased by carrying out the alkaline chlorination reaction of rare earth oxides by performing alkaline roasting.

The present invention is characterized by alkali roasting the waste phosphor fine powder at 900 to 1100 ° C. for 2 to 4 hours. The alkaline roasting is characterized by adding any one or a mixture of two or more selected from the group consisting of sodium carbonate, sodium hydroxide, potassium carbonate, and potassium hydroxide in an amount 1.5 to 3 times the weight of the waste phosphor fine powder. Preferably, the alkaline roasting is performed by adding sodium carbonate twice the weight of the waste phosphor fine powder.

If the reaction conditions are not met, alkali chloride of oxides of rare earth elements due to alkaline roasting may be insufficient, and acid leaching efficiency may be lowered. Terbium), and lanthanum (Lanthanum) are most effective as a roasting agent for simultaneous acid leaching.

The alkaline-roasted waste phosphor micropowder is added with strong acid to prepare a waste phosphor micropowder-strong acid reaction solution and reacted at 50 to 60° C. to simultaneously leach rare earth elements. The strong acid may be any one or a mixed acid of two or more selected from the group consisting of hydrochloric acid (HCl), nitric acid (HNO ₃ ), and sulfuric acid (H ₂ SO ₄ ), and its concentration is 0.2 to 0.4N. Preferably the strong acid is sulfuric acid and its concentration is 0.3N.

According to an embodiment of the present invention, a strong acid having a concentration of 3N or higher is required to elute rare earth elements by acid leaching waste phosphors that have not been alkaline-roasted. Furthermore, in the case of terbium and lanthanum, acid leaching was impossible at a concentration of 3N, so a separate acid leaching process using a higher concentration of strong acid had to be further performed.

However, as a result of acid leaching after alkaline roasting under optimal conditions for the waste phosphor, all of the rare earth elements in the waste phosphor could be eluted with only a strong acid equivalent to 10% of the level of the case where alkali roasting was not performed. In particular, acid leaching of terbium and lanthanum, which had been impossible for acid leaching, became possible, and yttrium, europium, cerium, terbium, and lanthanum were simultaneously recovered with only one acid leaching process. It became possible. The above results drastically reduce the amount of wastewater inevitably generated in the process of recovering rare earth elements from waste phosphors and simplify the separation process of rare earth elements, thereby reducing recycling costs.

The reaction solution from which rare earth elements are leached by the above method can be purified into high-purity rare earth elements through a known rare earth separation and purification technology, and a conventional fractional crystallization method, fractional precipitation method, or selective oxidation-reduction method can be applied as a separation and purification method of rare earth elements. .

In the following, the present invention will be described in detail through examples.

Example

1. Experiment method

The waste phosphor sample for the present invention was provided by the Waste Fluorescent Lamp Recycling Corporation.

The process of recycling waste fluorescent lamps of the present invention consists of a crushing process, a pearlization process, a classification process, and a heat treatment process. The crushing process is a process of crushing waste fluorescent lamps in a decompression chamber and adsorbing and removing mercury vapor by guiding it to an activated carbon absorption tower. The pearlizing process is a process of separating sharp glass fragments and phosphors crushed through friction. The classification process is a process of dividing and recovering the desorbed fine phosphors by 325#. The heat treatment process is a process of volatilizing and removing trace amounts of mercury present in waste glass from which phosphors have been removed by heating to 750°C.

The physical properties and chemical composition of the particulate phosphors recovered through the classification process were analyzed.

1 shows the result of X-ray diffraction analysis of the particulate phosphor isolated from the waste fluorescent lamp of the present invention, and FIG. 2 shows the result of scanning electron microscope (SEM) analysis of the particulate phosphor isolated from the waste fluorescent lamp of the present invention. show

As a result of observing the shape and size of the waste phosphor by SEM, it was confirmed that the waste phosphor was an agglomerate with a diameter of 5 to 15 μm composed of primary particles with a diameter of 0.05 to 3 μm. As a result of X-ray diffraction analysis, it is confirmed that the waste phosphor contains yttrium oxide as a main component and further contains barium magnesium aluminum oxide and magnesium aluminum lanthanum oxide. Table 1 shows the results of analyzing the components of the waste phosphor of the present invention by X-ray diffraction analysis.

Y ₂ O ₃ Al ₂ O ₃ SiO ₂ CaO P ₂ O ₅ CeO ₂ BaO MgO Na ₂ O Eu ₂ O ₃ Tb ₄ O ₇ La ₂ O ₃ wt% 29.1 27.4 13.8 6.71 3.68 3.49 2.74 2.60 2.40 1.98 1.77 1.47

According to the results of Table 1 and FIG. 2, it is confirmed that a significant amount of SiO ₂ is present in the waste phosphor. However, according to the X-ray diffraction pattern of FIG. 1, it is confirmed that the diffraction pattern of SiO ₂ is not observed, which is considered to be because the SiO ₂ exists in a very low crystallization state. The phosphor of the present invention contains 29.1 wt% of Y ₂ O ₃ , a rare earth oxide, 3.49 wt% of CeO ₂ , and 1.98 wt% of Eu ₂ O ₃ , Tb ₄ O ₇ is included in 1.77wt%, Since La ₂ O ₃ is included in 1.47 wt%, it is determined that sufficient economic feasibility can be secured if recovered through a recovery process.

Figure 3 shows the acid leaching test system for the waste phosphor of the present invention. The waste phosphor acid leaching system of the present invention uses a double-jacketed glass reactor capable of controlling temperature and atmosphere. Temperature and pH changes during the acid leaching reaction were measured, and samples of the acid leaching solution were taken at intervals of one hour using a syringe filter, and the concentration of each dissolved component was analyzed by an inductively coupled plasma (ICP) method.

The acid leaching experiment was conducted with different acid types, concentrations, and temperatures, and from the results, the leaching reaction rate and leaching reaction activation energy for each rare earth element were obtained. The acid leaching test was conducted on roasted and non-roasted samples, respectively, and optimal roasting conditions were found by varying the roasting agent and roasting temperature.

The leaching rate was calculated by Equation 1 below by analyzing the concentration of rare earth elements in the filtrate and the concentration of rare earth elements in the leaching residue after filtering the leaching reaction product.

2. Experiment results and consideration

_{The reaction conditions ( temperature _ _ _} The acid leaching behavior of 5 rare earth elements (yttrium: Y, europium: Eu, cerium: Ce, lanthanum: La, terbium: Tb) was observed from the waste phosphor according to , concentration, time) and acid leaching behavior according to the roasting conditions also investigated.

2-1. Leaching rate according to the type of element

900 ml of distilled water and 10 g of waste phosphor powder were added to two types of jacketed reactors designed to precisely control the temperature of the reaction solution, and after the temperature of the reaction solution reached 50 ° C, 100 ml of 3N hydrochloric acid solution at 50 ° C was added. was added, and solution samples were taken at predetermined time intervals to measure the concentration of dissolved rare earth elements.

4 shows the result of leaching the waste phosphor powder of the present invention into a 3N hydrochloric acid solution. As a result of the experiment, it was confirmed that Y was eluted the most, and it was confirmed that dissolution proceeded rapidly until 1 hour, but after that, a very slow dissolution reaction proceeded. Considering that the content of Y in the sample is 2500 mg/L, it is confirmed that 92% of Y is eluted within 3 hours. In the case of Eu and Ce, it was confirmed that the trend was very similar to that of Y, but the leaching rate was confirmed to be lower than that of 70% and 8%. It was confirmed that Tb and La were not dissolved at all. This phenomenon was almost the same under all tested conditions (acid type, concentration and temperature).

2-2. Elution rate of Y according to acid type

The above five acids prepared to have a hydrogen ion concentration of 3N (hydrochloric acid (HCl), sulfuric acid (SO ₄ ), nitric acid (HNO ₃ ), aqua regia (3HCl + HNO ₃ ), mixed acid (1H ₂ SO ₄ + 1C ₆ 100 ml of each H ₈ O ₇ ) was aliquoted to 50 ° C, and acid leaching was performed by adding 10 g of waste phosphor powder and 900 ml of distilled water. Rare earth concentrations were measured from

5 shows that the waste phosphor powder of the present invention is hydrochloric acid (HCl), sulfuric acid (SO ₄ ), nitric acid (HNO ₃ ), aqua regia (3HCl+HNO ₃ ), and mixed acid (1H ₂ SO ₄ +1C ₆ H ₈ O ₇ ) shows the result of elution. As a result of the experiment, the concentration of Y leached at 10 minutes, the initial reaction, was the highest at 1100 mg/ℓ in mixed acid (1H ₂ SO ₄ +1C ₆ H ₈ O ₇ ) and the lowest at 200 mg/ℓ in hydrochloric acid, about 5.5 times higher. It was confirmed that there was a difference in the leaching rate of However, it was found that the leaching rate of all acids was the same when the reaction time was more than 1 hour. In addition, it was found that the concentration of Y leached from the spent phosphor at 50° C. for 180 minutes was 2300 to 2400 mg/L depending on the type of acid, and the leaching rate was 92 to 96%.

2-3. Elution change of Y according to acid concentration

100 ml of hydrochloric acid having concentrations of 3N, 1N, and 0.3N, respectively, at 50°C was added to a reaction solution at 50°C in which 10 g of waste phosphor and 900 ml of distilled water were mixed, and stirred to collect samples at predetermined time intervals. The sample was filtered to prepare a filtrate, and the concentration of rare earth elements present in the filtrate was measured.

6 shows the result of Y leached by leaching the waste phosphor of the present invention by hydrochloric acid at various concentrations. As a result of the experiment, when the reaction concentration was 0.03N, the concentration of Y leached at 180 minutes was 449mg/L, and when the reaction concentration was 0.1N, the concentration of Y leached at 180 minutes was 1568mg/L, and at 0.3N In this case, the concentration of Y leached at 180 minutes of reaction time was 2308 mg/L. From the above results, despite the 3.33-fold increase in the acid concentration from 0.03N to 0.1N, the 3.49-fold increase in the leaching concentration of Y is determined to be due to the presence of about 0.0019 N equivalent of a substance that reacts with hydrochloric acid rather than Y. In addition, from the fact that 1568 mg/L, which is 67.93% of the final concentration of 2308 mg/L, is leached under the conditions of a reaction concentration of 0.1 N and a reaction time of 180 minutes, 2308 mg of hydrochloric acid soluble in 2500 mg of Y contained in 10 g of spent phosphor The minimum amount of hydrochloric acid required to completely dissolve Y is calculated to be 0.147N.

2-4. Elution change of Y according to leaching temperature

The reaction temperature of the acid leaching reaction, which is carried out by adding 100 ml of 3N hydrochloric acid to the reaction solution in which 10 g of the waste phosphor and 900 ml of distilled water is mixed, is changed to 20 ° C, 50 ° C, and 80 ° C, respectively, Y over time, Leaching concentrations of Eu, Ce, La, and Tb were measured.

7 shows the results of Y leached by leaching the waste phosphor of the present invention by 3N hydrochloric acid at 20 ° C, 50 ° C or 80 ° C. As a result of the experiment, when the reaction temperature was 20℃ and the acid leaching reaction was performed for 180 minutes, the leaching reaction speed was slow, so even if the leaching reaction was performed for 180 minutes, the leaching reaction was performed at 80℃ for 180 minutes. It was confirmed that only (393㎎/ℓ) was leached, and it was confirmed that only 94.6% (2308㎎/ℓ) of the result of performing the leaching reaction at 50 ℃ for 180 minutes was leached at 80 ℃ for 180 minutes. . Therefore, it is advantageous in terms of leaching rate and recovery rate to carry out the acid leaching process of rare earth elements from waste phosphors as high as possible in terms of leaching rate and recovery. It was found that it could be recovered by leaching.

2-5. leaching reaction rate

Table 2 shows the initial leaching reaction rate for each rare earth element (Ce, Eu, Y) calculated by treating the waste phosphor of the present invention according to conditions of temperature, concentration, and type of acid.

acid Conc.
(N) Temp.
(℃) initial leaching reaction rate (mol/L s) Ce Eu Y HCl 0.03 20 ND 0.00004387 0.0006749 50 0.00001189 0.00006581 0.0015185 80 0.00002379 0.0001755 0.005324 0.1 20 ND 0.00004387 0.0008436 50 0.00001189 0.0001316 0.0029994 80 0.00008326 0.0005703 0.0140036 0.3 20 ND 0.00006581 0.0011248 50 0.00001189 0.0001535 0.0037868 80 0.0001427 0.0011297 0.0275572 HNO ₃ 0.03 20 ND 0.00005484 0.0011623 50 0.00001189 0.00009871 0.0022871 80 0.00003568 0.0001645 0.0044429 0.1 20 ND 0.00004381 0.0007862 50 0.00001207 0.0001558 0.0036326 80 0.00007755 0.0007151 0.0174174 0.3 20 ND 0.00007677 0.0047053 50 0.00004758 0.0004277 0.0098606 80 0.0002498 0.0011407 0.0329936 H ₂ SO ₄ 0.03 20 ND 0.00004387 0.0006374 50 0.00002379 0.00008774 0.0019309 80 0.00003568 0.0002523 0.0071049 0.1 20 ND 0.00001687 0.0016006 50 0.00002017 0.0001581 0.0036234 80 0.00007505 0.0007266 0.0178808 0.3 20 ND 0.00007677 0.0013497 50 0.00003568 0.0002303 0.0054552 80 0.0001903 0.0017 0.0353557

From the results of Table 2, it was found that the initial leaching reaction rate of Ce, Eu, and Y increases as the concentration and temperature increase regardless of the type of acid, and the rate increases in the order of Y>Eu>Ce under the same conditions. . In the case of Y, the initial leaching reaction rate at 80 ° C using 0.3 N sulfuric acid was the fastest at 0.035 mol / L s, followed by nitric acid at 0.033 mol / L s and hydrochloric acid at 0.028 mol / s. It was confirmed to have a leaching reaction rate of L·s.

In the case of Eu, the initial leaching reaction rate at 80 ° C using 0.3 N sulfuric acid was 0.0017 mol / L s, which was the fastest, followed by nitric acid (0.00114 mol / L s) and hydrochloric acid (0.00113 mol / L It was confirmed that it was faster in the order of s).

In the case of Ce, the initial leaching reaction rate at 80 °C using 0.3N nitric acid was the fastest at 0.00025 mol/L s, followed by sulfuric acid (0.00019 mol/L s) and hydrochloric acid (0.00014 mol/L). s) followed.

2-6. Effect of Roasting Additives

In the above, an acid leaching reaction experiment was conducted on waste phosphors that were not roasted. As a result, it is possible to leach and recover more than 92% of Y and Eu without roasting, but the recovery rate of Ce is too low and La and Te cannot be recovered at all. I found out that there is no

Accordingly, in order to recover Ce, La, and Tb, the waste phosphor was alkaline-roasted and then an acid leaching experiment was conducted. As an additive for alkaline roasting (roasting agent), sodium carbonate, sodium hydroxide, potassium carbonate, potassium hydroxide, and sodium carbonate 1 + potassium carbonate 1 were used.

20 g of each roasting agent was mixed with 10 g of the waste phosphor, roasted at 1000 ° C for 2 hours, and then leached with 1 liter of 0.6 N sulfuric acid solution at 50 ° C for 2 hours. A sample was taken from the reaction solution and the concentration of rare earth elements present in the filtered filtrate was investigated.

8 shows the result of analyzing rare earth elements present in the reaction solution in which acid leaching was performed for 2 hours with 1 liter of 0.6 N sulfuric acid solution at 50° C. after alkaline roasting was performed on the waste phosphor of the present invention. As a result of the experiment, it was confirmed that Y and Eu were leached almost 100% regardless of the type of roasting agent, but the leaching rate of Ce was significantly different depending on the type of roasting agent. For example, when sodium carbonate 1 + potassium carbonate 1 was used as a roasting agent, the highest leaching rate was about 96%, whereas when potassium carbonate was used as a roasting agent, it was confirmed that the lowest leaching rate was about 50%. In the case of Tb, the highest leaching rate was about 98% when potassium carbonate was used as a roasting agent, and the lowest was about 65% when potassium hydroxide was used as a roasting agent. In the case of La, the highest leaching rate was about 76% when sodium carbonate was used as a roasting agent, and the lowest was about 41% when potassium hydroxide was used as a roasting agent.

The above result means that it is possible to select the most suitable additive according to the type of rare earth when only one type of rare earth is to be recovered. However, in the case of the present invention, since all five types of rare earth elements (Y, Eu, Ce, La, and Tb) are to be recovered in the study, it was determined that sodium carbonate would be most suitable as a roasting agent in comprehensive consideration. In the following experiment, a change in the roasting condition when sodium carbonate is used as a roasting agent and a resultant change in the leaching rate of rare earth elements will be described.

2-7. Effect of roasting temperature

A sample obtained by mixing 10 g of the waste phosphor powder and 20 g of sodium carbonate powder of the present invention was roasted at a predetermined temperature for 2 hours, and then an acid leaching reaction was performed. Roasting temperatures were 600 ° C, 800 ° C, 1,000 ° C, and 1,200 ° C, and the leaching reaction was carried out at 50 ° C with 1 liter of 0.6 N sulfuric acid aqueous solution for 2 hours. After the acid leaching reaction was completed, the reaction solution was filtered to separate the filtrate and the leaching residue, and the concentration of each rare earth element was analyzed to calculate the leaching rate.

9 shows the result of calculating the leaching rate of each rare earth element in which the waste phosphor of the present invention was alkaline-roasted with sodium carbonate and leached in sulfuric acid.

According to FIG. 9, Y showed a leaching rate of 99 to 100% regardless of the roasting temperature, and Eu showed a leaching rate of 92% at 600 ° C and 100% at 1000 ° C. showed a decrease in %. La showed a leaching rate of 83% at 600 ° C and the highest leaching rate of 89% at 1000 ° C, but rapidly decreased to 60% again at 1200 ° C. Although the leaching rate of Tb increased as the temperature increased, it was confirmed that the leaching rate rather decreased as the temperature further increased, peaking at 87% at 1100 ° C. Finally, it was confirmed that the leaching rate of Ce continued to increase as the temperature increased, showing a leaching rate of 100% at 1200 °C.

In summary, 1200 ° C is suitable for the roasting temperature to improve the leaching rate of Ce, but 1000 ° C is suitable for the roasting temperature to improve the leaching rate of Tb, La, and Eu, and in the case of Y, the roasting temperature is 600 ° C or higher. is judged to be desirable. The reason why the leaching rate of Tb, La, and Eu is lower at 1200℃ than at 1000℃ is that the formation reaction of sodium salt produced by the reaction between rare earth oxides and sodium carbonate is completed at about 1000℃, but at 1200℃ the crystallinity of the sodium salt is developed. This is considered to be more stable.

2-8. Effect of Roasting Time

A mixture of 10 g of the waste phosphor powder and 20 g of sodium carbonate powder of the present invention was calcined at 1,000 ° C for a predetermined time, and then an acid leaching reaction was performed. The roasting time was 30 minutes, 60 minutes, 120 minutes and 240 minutes, and the leaching reaction was carried out for 2 hours with 1 liter of 0.6N sulfuric acid aqueous solution at 50 ℃.

10 shows the result of calculating the leaching rate of each rare earth element in which the waste phosphor of the present invention was alkaline-roasted with sodium carbonate for a predetermined time and leached in sulfuric acid.

As a result of the experiment, Y shows a leaching rate of 99 to 100% regardless of the roasting time, and Eu has a leaching rate of about 89% at 30 minutes of roasting time, but when the roasting time is increased to 120 minutes, the leaching rate increases to 100%. It was confirmed that the leaching rate tended to decrease to about 93% when increased up to 10 min. It was confirmed that the leaching rate of La was about 60% at 30 minutes of roasting time, but when the roasting time was increased to 120 minutes, the leaching rate increased to 90%, and when the roasting time was increased to 240 minutes, the leaching rate tended to decrease to about 64%. It became.

La and Eu showed the highest leaching rate at 120 minutes of roasting time and rather decreased leaching rate at 240 minutes of roasting time. It is believed that this is because the reaction proceeds and the surface of the sodium salt particle is stabilized, so that leaching is suppressed.

The leaching rate of Tb was 85% at 30 minutes of roasting time and increased to 95% at 240 minutes of roasting time. The leaching rate of Ce was 57% at 20 minutes of roasting time and 98% at 240 minutes of roasting time. It showed a tendency to increase, which means that the alkali chloride reaction between Ce and Tb continued until 240 minutes.

In summary, when roasting with sodium carbonate at 1000 ° C., it is judged that the preferred roasting time of Y, Eu, and La is about 2 hours, and the preferred roasting time of Tb and Ce is about 4 hours.

2-9. Added amount of roasting agent

A sample of a mixture of 10 g of the waste phosphor powder of the present invention and a predetermined amount of sodium carbonate powder was roasted at 1,000° C. for 2 hours, and then an acid leaching reaction was performed. The amount of sodium carbonate mixed was 5 g, 10 g, 20 g, and 40 g, respectively, and the leaching reaction was carried out at 50 ° C. with 1 liter of 0.6 N sulfuric acid aqueous solution for 2 hours.

11 shows the result of calculating the leaching rate of each rare earth element, which was subjected to a leaching reaction in sulfuric acid after alkaline roasting was performed with the waste phosphor of the present invention and a predetermined amount of sodium carbonate.

Y and Eu show a leaching rate of 99 to 100% regardless of the amount of sodium carbonate added, and La shows a leaching rate of about 90% at the same addition amount of 10 g as the spent phosphor, and the leaching rate increases even if the amount added is more than that. It can be seen that it does not

Tb showed a leaching rate of 65% at 5 g, but increased to 93% at 20 g, and no increase in leaching rate was observed at more than 5 g. Ce showed a leaching rate of 27% at 5 g, but increased to 70% at 20 g. It can be seen that the leaching rate increases and no increase in the leaching rate is observed at a higher addition amount.

From the above results, since the rare earth contained in the waste phosphor reacts with sodium carbonate at 1000 ℃ and is roasted, it is judged that the order of the reaction to produce sodium salt is Y>Eu>La>Tb>Ce, and leaches rare earth from the waste phosphor with high efficiency It is considered that the amount of sodium carbonate added for this purpose is about twice the weight of the phosphor.

3. Conclusion

The conclusion of confirming the acid leaching behavior of five rare earth elements (Y, Eu, Ce, La, Tb) from the waste phosphor powder of the present invention is as follows.

1) When the unroasted mine powder is leached at 50℃ with 0.3N hydrochloric acid, about 92% of Y is eluted, 70% of Eu is eluted, and 8% of Ce is eluted for 3 hours, but Tb and La are eluted. not eluted at all.

2) As a result of comparing the leaching rate according to the type of acid for the unroasted waste phosphor powder, there was a slight difference in the initial leaching rate, but the leaching rate after 1 hour was almost the same. It is advantageous in terms of leaching rate and recovery rate, and when Y is to be leached, a leaching rate of 97.5% can be obtained by reacting at 80 ° C for 60 minutes.

3) Y, Eu, Ce leached from waste phosphor powder that is not roasted, regardless of the type of acid, the higher the concentration of acid and the higher the leaching temperature, the faster the initial reaction rate. Under the same conditions, the order of Y>Eu>Ce leaching rate is fast. In the case of Y, the initial leaching reaction rate at 80 °C using 0.3N sulfuric acid was the fastest at 0.035 mol/L s, followed by nitric acid at 0.033 mol/L s and hydrochloric acid at 0.028 mol/L s. confirmed as In the case of Eu, the initial leaching reaction rate at 80 ℃ using 0.3N sulfuric acid was the fastest at 0.0017 mol/L s, followed by nitric acid at 0.00114 mol/L s and hydrochloric acid at 0.00113 mol/L s. confirmed as s. In the case of Ce, the initial leaching reaction rate at 80 ° C using 0.3N nitric acid was the fastest at 0.00025 mol/L s, followed by sulfuric acid at 0.00019 mol/L s and hydrochloric acid at 0.00014 mol/L s. s was investigated.

4) When acid leaching was performed after alkaline roasting under optimum conditions for each element, it was confirmed that the leaching rate of Y and Eu increased to 100%, cerium to 98%, terbium to 92%, and lanthanum to 89%. Y, Eu, Ce, La, Tb) in case of leaching all rare earth elements at once, sodium carbonate is most suitable as a roasting agent. About twice the weight is appropriate.

Specific examples described in this specification are meant to represent preferred embodiments or examples of the present invention, and the scope of the present invention is not limited thereby. It will be apparent to those skilled in the art that variations and other uses of the present invention do not depart from the scope of the invention described in the claims.

Claims (5)

A method for recovering rare earth elements from a lighting device containing waste phosphors,
A first step of crushing the lighting device including the waste phosphor and obtaining a fine powder of the waste phosphor having a diameter of less than 700 μm;
A second step of mixing the waste phosphor micropowder and sodium carbonate at a weight ratio of 1:2, followed by alkaline roasting at 1000° C. for 2 to 4 hours;
A 0.6N sulfuric acid solution was added to the alkali-roasted waste phosphor micropowder to prepare a waste phosphor micropowder-strong acid reaction solution and reacted at 50 to 60° C. to produce rare earth elements such as yttrium, europium, and cerium. ), a third step of simultaneously leaching Terbium and Lanthanum; and
a fourth step of recovering rare earth elements from the spent phosphor fine powder-strong acid reaction solution from which the rare earth elements are leached;
A method for simultaneously recovering yttrium, europium, cerium, terbium, and lanthanum, which are rare earth elements, from a lighting device including a waste phosphor comprising a.
The method of claim 1, wherein 100% of the yttrium is leached and recovered from the alkali-roasted waste phosphor fine powder; The europium is 100% leached and recovered from the alkali-roasted waste phosphor fine powder; 98% of the cerium is leached and recovered from the alkali-roasted waste phosphor fine powder; 92% of the terbium is leached and recovered from the alkali-roasted waste phosphor fine powder; 89% of the lanthanum is leached and recovered from the alkali-roasted waste phosphor fine powder; A method for simultaneously recovering yttrium, europium, cerium, terbium, and lanthanum, which are rare earth elements, from a lighting device containing a waste phosphor.
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