Method for leaching rare earth elements from fluorescent lamp waste

Abstract

This disclosure relates to a method that enables the direct leaching of Y and Eu in red phosphorus, and especially La, Ce, Gd, and Tb metals in blue and green phosphorus, in a single step, without the need for a pretreatment step of the phosphor powder in fluorescent lamp waste that requires high energy consumption.

Description

Technical Field

[0001] The present invention relates to a method for leaching rare earth elements (REE) in phosphorus powder.

[0002] The present disclosure particularly relates to a method that enables the direct leaching of Y and Eu in red phosphorus in phosphor powder, and in particular La, Ce, Gd, and Tb metals in blue and green phosphorus in phosphor powder in a single step without using a pretreatment process for phosphor powder in fluorescent lamp waste that requires high energy consumption.

Background Art

[0003] The use of fluorescent lamps is still quite common in many regions of the world. Even when fluorescent lamps reach the end of their life or are discarded due to any malfunction, it is important to recycle the materials contained therein because they have various uses in today's technology.

[0004] Rechargeable batteries, electronic devices, and fluorescent lamps become important sources of raw materials when they become waste. In particular, the phosphor powder in fluorescent lamps is rich in rare earth elements and is an important source of raw materials, and is the subject of this study from the perspective of recovering rare earth elements.

[0005] In today's technology, the methods for obtaining rare earth elements from natural resources are considered to be high-cost and complex process applications. Low-cost and environmentally friendly methods are required for recycling waste equipment and recovering materials.

[0006] For recovering rare earth elements, leaching is a preferred wet smelting process because it is economical and its parameters are controllable. In the leaching process, a solvent is used to remove soluble components from the ore or similar solid into a solution. Existing methods require preparing the process by subjecting the ore or solid material to be used to processes such as alkali fusion and mechanical activation, which require high energy. This makes the method costly, energy-intensive, and prolonged. To overcome the shortcomings of the prior art and to extract rare earth elements from phosphorus powder with high efficiency, the present invention includes a microwave leaching process.

[0007] The most advanced technology is described in Australian Patent Application Publication No. 2003229402, which utilizes a microwave energy leaching process to recover valuable components such as metals from ore. This document describes parameters such as the pulse duration, intensity, and waiting interval of the microwave energy. "Microwave energy" is specified as electromagnetic radiation having a frequency in the range of 0.3 to 300 GHz. Paragraph 12 of this document explains that unwanted materials can be separated from contaminants by separating them from crushed ore particles, with phosphorus and aluminum materials given as examples. The document states that phosphorus should be separated from the ore as a contaminant, and it was observed that there is no motivation to separate rare earth elements and metals from phosphorus dust.

[0008] Australian Patent Application Publication 2014250661 describes a method for recovering rare earth elements that requires multiple steps and includes a pre-leaching process. In the related technology, pre-leaching of ore with sulfuric acid requires the application of multiple iterative processes, such as mixing acid-insoluble minerals and calcium sulfate precipitates present in the solid phase with sulfuric acid, acid-calcining the mixture at a temperature of 200-300°C to produce a calcined solid phase, then subjecting it to aqueous leaching and / or pre-leaching of the liquid phase in water, dissolving the rare earth elements in the acid-calcined solid phase, forming a liquid phase by leaching with water, and forming a solid phase by leaching with water. Unlike the method described in the aforementioned technology, the method of the present invention involves applying microwave leaching, and it has been shown that REE in blue phosphorus and green phosphorus can be separated by the parameters applied to the method of the present invention. Therefore, it is understood that the technology of Australian Patent Application Publication 2014250661 is not for phosphorus powder, and the parameters are not suitable for leaching Tb, La, Ce, and Gd.

[0009] International Publication No. 2017100933 describes a process for selectively extracting rare earth elements from ores or mineral concentrates containing one or more gangue-derived elements, such as iron, aluminum, zirconium, and niobium. This process comprises the steps of: preparing a mineral concentrate; mixing concentrated sulfuric acid with the mineral concentrate; heating the mixture in a first heat vessel to promote sulfation; increasing the temperature in a second heat vessel to selectively decompose the sulfation of non-rare earth metals; and preparing a leaching solution containing rare earth elements. Evaluation of the steps and parameters of this method reveals that the leaching process is intended for ores containing gangue-derived elements such as iron, aluminum, zirconium, and niobium, and is not suitable for application to phosphorus powder. Parameters and steps related to the recovery of La, Ce, Gd, and Tb metals are not included.

[0010] The October 2019 publication "Investigation of the Recovery of REEs in Phosphorus Powder Used in Fluorescent Glasses," in which the inventors were involved, is also relevant technical literature. This publication investigates the dissolution behavior of Y and Eu metals in phosphorus powder by H2SO4 leaching at different times and temperatures, and describes the methods applied and the results (https: / / www.researchgate.net / publication / 337414536_Floresan_Camlarda_Kullanilan_Fosfor_Tozundaki_NTE's_Geri_Kazaniminin_Arastirilmasi). The 2019 publication describes research on the leaching of Y and Eu metals with sulfuric acid, and since it mentions obtaining Y and Eu metals, it is understood to be research on red phosphorus.

[0011] Phosphorus powder is known to contain red phosphorus, blue phosphorus, and green phosphorus. Red phosphorus contains oxide forms of Y and Eu metals, while blue and green phosphorus contain aluminate and phosphate-bonded structures of La, Ce, Gd, and Tb metals.

[0012] According to the literature, it is known that preliminary processes such as alkali fusion and mechanical activation are necessary to leach Tb, La, Ce, and Gd from blue and green phosphorus. After these pretreatments, it is possible to leach the metals La, Ce, Gd, and Tb with high efficiency by repeating the leaching process in an acidic solution. A search of the prior art and literature in this field reveals that there are no studies on the single-step leaching of REE from phosphorus powder, particularly blue and green phosphorus.

[0013] As a result, due to the inadequacy of known technical applications and developed solutions, innovation is needed in methods for leaching rare earth elements (REEs), particularly blue and green phosphorus, from fluorescent lamp waste.

[0014] Brief Description of the Invention The present invention relates to a method for leaching rare earth elements (REEs) from fluorescent lamp waste, which satisfies the above requirements, eliminates all drawbacks, and brings about several additional advantages.

[0015] The present invention aims to obtain a solution to which a high concentration of rare earth elements has been added.

[0016] The present invention aims to obtain metals separately and efficiently by using a microwave leaching process, and to enable a uniform, rapid, and controllable reaction.

[0017] The present invention aims to obtain a REE-added solution without requiring high-energy pretreatment.

[0018] According to the method of the present invention, Tb, La, Ce, and Gd metals are incorporated into the solution in a single step. The objective is to obtain a high-concentration REE-added solution in this manner.

[0019] The present invention aims to incorporate Tb, La, Ce, and Gd metals into a solution while simultaneously leaching Y and Eu metals with greater efficiency.

[0020] The present invention aims to achieve environmentally friendly and highly efficient REE extraction with less energy consumption by avoiding the use of pretreatments such as alkaline fusion and mechanical activation.

[0021] The present invention aims to directly extract blue phosphorus and green phosphorus from phosphorus powder in a single step, a method that is the first of its kind in the literature.

[0022] In the method of the present invention, microwave leaching is applied to increase the yield of recovered metal and reduce processing time. The microwave leaching process provides an opportunity to work with more controllable parameters.

[0023] The structural features and characteristics of the present invention, as well as all its advantages, will be more clearly understood from the detailed description provided. Therefore, the evaluation should be made taking this detailed description into consideration.

[0024] The method developed for the leaching of rare earth elements (REE) in fluorescent waste, which is the subject of this application, is shown in the attached drawings.

Brief Description of the Drawings

[0025] [Figure 1] It is a diagram of the process steps representing the method of the present invention.

Modes for Carrying Out the Invention

[0026] In this detailed description, the preferred embodiments of the method for leaching rare earth elements (REE) in fluorescent waste are described only for better understanding of the subject matter and have no limiting effect.

[0027] The method of the present invention enables the direct leaching of rare earth elements (REE) in phosphorus dust in a single step without using a pretreatment step that requires high energy for the phosphorus dust in fluorescent waste, and includes the following process steps: · Procurement of raw materials (101) · Pretreatment of raw materials that do not require high energy (102) - Size classification of phosphorus powder (102.1) - Homogenization of phosphorus powder (102.2) · Microwave leaching process (103), · Solid-liquid separation (104).

[0028] In the step of procuring raw materials (101), 1 to 1000 kg of fluorescent waste phosphorus powder is procured from a recycling facility.

[0029] The raw material pretreatment process (102) includes processes that do not require high energy. Process 102 involves size sorting (102.1) and homogenization (102.2) of the phosphorus powder obtained by recycling.

[0030] The phosphorus powder size classification step (102.1) is a process of classifying the particle size of phosphorus powder by passing it through 100 μm and 45 μm sieves.

[0031] The phosphorus powder homogenization step (102.2) includes homogenizing the phosphorus powder in a ball mill for 0.1 to 100 hours at a grinding speed of 50 to 5000 rpm and washing them with pure water.

[0032] The microwave leaching process makes it possible to incorporate Tb, La, Ce, and Gd metals in blue and green phosphorus and Eu and Y metals in red phosphorus into the solution in a single step (103). The microwave leaching process is applied to phosphorus powder in an acidic solution of 0.01 to 12 M, with a volume of 0.1 to 1000 L, at a temperature of 15 to 250°C for 0.1 to 20 hours.

[0033] The power applied to the microwave leaching process (103) is not constant. The application of microwaves varies between 0 and 1600 W depending on the specified temperature (15-250°C). By applying microwaves at various values ​​within the above parameters, highly efficient REE-added solutions were obtained.

[0034] In the microwave leaching process (103), 0.01–12 M sulfuric acid (H2SO4), nitric acid (HNO3), and hydrochloric acid (HCl) solutions are used.

[0035] Single-step solutions of Tb, La, Ce, and Gd metals in blue and green phosphorus and Eu and Y metals in red phosphorus are obtained by applying a microwave leaching process (103). Using the parameters described, the dissolution of rare earth elements into phosphorus powder was achieved in a single process step. As a final step, solid-liquid separation is performed (104) after the microwave leaching process (103). In the solid-liquid separation (104) process, solids that do not enter the solution are preferably separated by filtration.

[0036] [Table 1]

[0037] When the method of the present invention is applied, the final product obtained is a solution containing high concentrations of Y and Eu, as well as La, Ce, Gd, and Tb. The table above shows the method that is the subject of the present invention. The REE value obtained as a result of applying the formula is shown. [Explanation of Symbols]

[0038] Description of the process steps of the method 101 Procurement of raw materials 102 Pre-processing of raw materials 102.1 Size Classification of Phosphorus Powder 102.2 Homogenization of phosphorus powder 103 Microwave leaching process 104 Solid-liquid separation

Claims

1. A method for leaching rare earth elements (REEs) from fluorescent lamp waste, comprising the following steps: Procurement of phosphorus powder from fluorescent lamp waste (101), The aforementioned phosphorus powder waste from fluorescent lamps is classified by size (102.1) and homogenized (102.2), Application of a microwave leaching process (103) to homogenized (102.1) fluorescent lamp waste phosphorus powder, Separation of solid and liquid formed as a result of the process (104), A method characterized by including

2. The method according to claim 1, characterized in that the fluorescent lamp waste phosphorus powder is passed through sieves of 100 μm and 45 μm in order to perform the size classification (102.1).

3. The method according to claim 1 or 2, characterized in that the grinding operation is performed at a value in the range of 50 to 5000 rpm in order to perform the homogenization (102.2).

4. The method according to claim 3, characterized in that the grinding operation for homogenization (102.2) is performed in a ball mill for a value in the range of 0.1 hours to 100 hours.

5. The method according to any one of claims 1 to 4, characterized in that after homogenization (102.2), washing with water is performed at least once.

6. The method according to any one of claims 1 to 5, characterized in that the microwave leaching process (103) uses at least one of the group consisting of sulfuric acid, nitric acid, or hydrochloric acid as an acid solution.

7. The method according to claim 6, characterized in that the microwave leaching process (103) is performed in which the acid solution is used at a value in the range of 0.01 M to 12 M or in a volume in the range of 0.1 L to 1000 L.

8. The method according to any one of claims 1 to 7, characterized in that the microwave leaching process (103) is carried out at a temperature in the range of 15°C to 250°C and for a period of time in the range of 0.1 hours to 20 hours.

9. The method according to any one of claims 1 to 8, characterized in that the microwave leaching process (103) is carried out at a maximum of 1600 W.

10. When using blue and / or green fluorescent lamp waste phosphorus powder as a raw material, at least one metal among Tb, La, Ce, or Gd is obtained. The method according to any one of claims 1 to 9, characterized in that when red fluorescent lamp waste phosphorus powder is used as a raw material, at least one metal selected from metals Eu or Y can be obtained.

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