Method and application for recovering nanometer titanium dioxide and metals from waste led devices

Abstract

The application discloses a method for recycling nano titanium dioxide and metal support iron copper nickel from waste LED electronic devices. The waste gallium arsenide LED is treated by a hydrothermal-ammonia water-oxidation system, and organic resin in the waste LED can be removed by oxidation, so that the inorganic part in the remaining LED is recycled. The inorganic part is mainly metal support iron copper nickel and titanium dioxide of the LED. Then, a screen is used to separate the titanium dioxide and the metal support according to the size difference. Then, the nano titanium dioxide is recycled by filtration. Finally, the two are placed in an oven for drying, and finally, the nano titanium dioxide with a purity higher than 97% and the metal support iron copper nickel of the LED without impurities are obtained. The application also discloses application of the method in recycling nano titanium dioxide and metal support iron copper nickel from waste LED electronic devices.

Description

Technical Field

[0001] This invention belongs to the field of recycling, reuse, and resource utilization technology of nanoscale inorganic fillers and metals in electronic waste, specifically involving a method and application for recovering nano-titanium dioxide and metals from waste LEDs. Background Technology

[0002] LEDs, also known as light-emitting diodes, are common electronic components that convert electrical energy into light energy. Due to their energy-saving, long-life, and mercury-free characteristics, their use has increased dramatically over the past decade. LEDs are widely used in displays, LCDs, mobile phone backlights, and general lighting. More importantly, for energy-saving reasons, many countries and regions are implementing legislation to phase out incandescent lamps and promote the use of LED lights, which means that the future usage of LEDs will inevitably grow rapidly. Waste LEDs mainly consist of white resin, transparent epoxy resin, metal brackets, metal leads, and chips. They contain precious metals such as gold and silver, and strategic metals such as gallium and indium, mainly concentrated in the chips and metal leads. At the same time, as a new type of electronic waste, LEDs are classified as hazardous waste in some regions such as the EU, Canada, and the US. Therefore, while LEDs have a resource-generating aspect, they also pose a potential risk of environmental pollution. Thus, it is necessary to dispose of LED waste in a green and harmless manner.

[0003] There are currently some studies on recovering metals from LEDs. Methods for recycling waste LEDs that can be referenced include mechanical separation, vacuum metallurgical separation, pyrometallurgy, hydrometallurgy, and bioleaching. Of these methods, only pyrometallurgy provides a green and environmentally friendly solution for decomposing the organic resins in waste LEDs. Pyrometallurgy also carries the risk of dioxin formation and toxin release during the processing of organic resins. Previous research on waste LED recycling has mainly focused on the recycling of metals, neglecting the removal of harmful substances such as organic encapsulation materials. The recovery of non-metallic inorganic materials, such as inorganic fillers in the resin, has also been overlooked.

[0004] TiO2, a filler that constitutes a large proportion of LED packaging materials, has been overlooked in previous recycling processes. TiO2 is widely used as a filler in polymer composites due to its high thermal conductivity (approximately 11.7 W / mK), low coefficient of thermal expansion (8.6 ppm / ℃), high resistivity, and non-toxic properties. The addition of TiO2 can improve the mechanical properties and thermal stability of polymer materials, such as tensile, flexural, and dielectric strength. In LED packaging materials, TiO2 not only improves the thermal conductivity of the resin but also enhances reflection and strengthens LED light output. Therefore, in the recycling of waste LEDs, while recovering the metals, the large proportion of titanium dioxide filler should also receive sufficient attention. Summary of the Invention

[0005] The purpose of this invention is to solve the problems of resource waste and environmental pollution caused by improper disposal of waste LEDs. It proposes an efficient and green method and application for recycling nano-titanium dioxide and metals from LEDs. This achieves the harmless treatment of organic resins in waste LEDs and the resource-based recycling of nano-titanium dioxide and metals.

[0006] The hydrothermal method, using water as a solvent in a closed reaction vessel, is a green, non-toxic, and pollution-free approach. It is used to create cleaner, safer, and more environmentally friendly chemical processes. It supports ionic, polar nonionic, and free radical reactions. More importantly, individual water molecules can participate in the reaction as reactants or catalysts. This invention innovatively proposes a method for recovering nano-titanium dioxide with a purity higher than 97% and impurity-free LED metal support iron-copper-nickel from waste LEDs through a hydrothermal-ammonia-oxidation system under specific conditions. This invention removes organic resins from waste LEDs through hydrolysis and oxidation using the hydrothermal-ammonia-oxidation system, leaving the inorganic components. These inorganic components mainly consist of the LED's metal support iron-copper-nickel and titanium dioxide. A sieve is then used to separate the titanium dioxide and the metal support based on their size differences. Then, filtration is used to recover the nano-titanium dioxide. The metal support iron-copper-nickel and titanium dioxide are then dried separately in an oven, ultimately yielding high-purity nano-titanium dioxide and impurity-free LED metal support iron-copper-nickel.

[0007] The specific technical solution for achieving the objective of this invention is as follows:

[0008] This invention proposes a method for recovering nano-titanium dioxide and the iron-copper-nickel metal support structure from waste LEDs. The method is characterized by treating the organic resin contained in the waste LEDs using a hydrothermal-ammonia-oxidation system to oxidize and degrade the organic matter in the LEDs. The remaining inorganic matter mainly consists of titanium dioxide and the iron-copper-nickel metal support structure. A sieve is used to separate the titanium dioxide and the metal support structure based on their size differences. Then, filtration is used to recover the nano-titanium dioxide. Both are then dried separately in an oven, ultimately yielding the nano-titanium dioxide and the iron-copper-nickel metal support structure of the LED. The method specifically includes the following steps:

[0009] (1) Place the waste LEDs into the lining of the reactor, and then add water, ammonia and oxidant to form a hydrothermal-ammonia-oxidation system;

[0010] (2) Place the reactor liner into the reactor, and then seal the reactor. Set the parameters for each experimental variable, turn on the heating button, and wait for the reaction to finish;

[0011] (3) The hydrothermal fluid obtained by the reaction in step (2) is sieved to separate the iron, copper and nickel metal support from the hydrothermal fluid;

[0012] (4) The remaining hydrothermal fluid after step (3) is filtered by a filtration method to separate and enrich nano-titanium dioxide from the water.

[0013] (5) The metal support iron, copper and nickel obtained in step (3) and the nano titanium dioxide obtained in step (4) are placed in an oven for drying treatment, and finally impurity-free metal support iron, copper and nickel and high-purity nano titanium dioxide are obtained.

[0014] In step (1), the ammonia water is selected from industrial ammonia water containing 25% to 28% ammonia; preferably, it is industrial ammonia water with 28% ammonia.

[0015] In step (1), the oxidant is selected from one or more of ozone, oxygen, hydrogen peroxide, etc.; preferably, it is hydrogen peroxide.

[0016] In step (1), the water is selected from one or more of deionized water, ultrapure water, tap water, groundwater, etc.; preferably, it is tap water.

[0017] In step (1), the amount of ammonia added is 1-5% of the water; preferably, it is 3%.

[0018] In step (1), the amount of oxidant added is 1 to 10% of water; preferably, it is 5%.

[0019] In step (1), the mass ratio of the waste LED, ammonia, water, and oxidant is (0.2-4):(1-13)(100-250):(1-25); preferably, it is 0.4:6:200:10.

[0020] In step (2), the reaction temperature is 180–350°C; preferably, it is 270°C.

[0021] In step (2), the reaction time is 5 to 60 minutes; preferably, it is 20 minutes.

[0022] In step (2), the rotation speed of the reactor is 200-1000 r / min; preferably, it is 800 r / min.

[0023] Furthermore, the preferred experimental variables are a reaction temperature of 270°C, a reaction time of 20 min, and a reaction vessel rotation speed of 800 r / min.

[0024] In step (3), the mesh size of the sieve is 10 to 200 mesh; preferably, it is 50 mesh.

[0025] In step (4), the filtration process is performed by vacuum filtration.

[0026] In step (5), the drying process uses a drying temperature between 50 and 150°C and a drying time between 50 and 600 min; preferably, the drying temperature is 70°C and the drying time is 100 min.

[0027] In step (5), a metal scaffold free of impurities, consisting of iron, copper, and nickel, with an impurity content of less than 0.1%, is finally obtained, along with high-purity nano-titanium dioxide, with a purity exceeding 97%.

[0028] Traditional research on the resource recovery of waste LEDs has largely focused on recycling the metals. Traditional recycling methods can be broadly categorized into three types: mechanical, dry heat, and wet processes. Mechanical methods, such as ball milling, use mechanical force to separate the metal and non-metal parts of the LED for recycling. However, this method has a drawback: while the organic encapsulation material in the LED can be broken down, a significant portion of the broken organic material adheres to the metal, affecting the recovery rate and purity of the metal. Dry heat methods, such as tube furnaces, suffer from the drawback of producing a large amount of carbon residue after dry heat treatment. This carbon residue, along with incompletely carbonized organic encapsulation material, adheres to the treated LED, thus dry heat methods cannot recover high-purity titanium dioxide and metal supports. Wet metallurgy commonly uses strong acids, such as aqua regia, to completely dissolve the waste LED under heating conditions, and then extracts the metals from the leachate. The disadvantages of this method are the environmental pollution and health risks associated with the strong acids or alkalis used, and the relatively complex recycling process. More importantly, this method directly dissolves titanium dioxide with strong acid, making it impossible to recover the titanium dioxide. This not only wastes resources but also poses potential risks to the environment.

[0029] The method of this invention is characterized by its ability to remove organic encapsulation materials from waste LEDs without leaving any residual carbon residue or dissolving titanium dioxide or metals. This method overcomes the shortcomings of traditional methods. Under a hydrothermal-ammonia-oxidation system, the organic encapsulation materials of LEDs first undergo hydrolysis at a lower temperature, breaking down large organic molecules into smaller monomers. Then, at a higher temperature, these smaller monomers are oxidized, ultimately converting into water and carbon dioxide. This method efficiently and environmentally removes organic encapsulation materials from LEDs without leaving any residue or damaging the titanium dioxide or metal support structure. Therefore, this method can recover impurity-free (impurity content less than 0.1%) iron, copper, and nickel metal support structures, as well as high-purity (purity higher than 97%) nano-titanium dioxide.

[0030] This invention also proposes the application of the method in recovering nano-titanium dioxide and metal support iron, copper and nickel from waste LED electronic devices.

[0031] The innovation of this invention lies in its ability to directly and efficiently recycle non-metallic components from waste LEDs without requiring pretreatment such as crushing or ball milling, or the addition of any organic or inorganic acids. Compared to the carbon slag residue caused by traditional dry heat methods, the method described in this invention can achieve the one-step recovery of high-purity titanium dioxide and impurity-free iron, copper, and nickel from the metal support structure. Compared to hydrometallurgy, the method described in this invention has the advantage of achieving efficient and high-purity recovery of metals from LEDs without consuming any acid, and the recovery process is simpler and more environmentally friendly than hydrometallurgy.

[0032] The beneficial effects of this invention are as follows: This invention proposes an efficient and green method for recycling nano-titanium dioxide and metals from LEDs. This invention achieves the harmless treatment of organic resins in waste LEDs and the resource recovery of nano-titanium dioxide and metals through a hydrothermal-ammonia-oxidation system, ultimately obtaining impurity-free (impurity content less than 0.1%) metal support iron-copper-nickel and high-purity (purity higher than 97%) nano-titanium dioxide. Attached Figure Description

[0033] Figure 1 The present invention relates to the recovery of nano-titanium dioxide and metals. Detailed Implementation

[0034] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below in conjunction with the accompanying drawings and specific embodiments. In the following embodiments, unless otherwise specified, the experimental methods used are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0035] Example 1

[0036] First, 0.78g of waste LED electronic devices containing gallium arsenide were heated at 260℃ for 10 minutes at a rotation speed of 300 rpm, and treated in a hydrothermal-ammonia-oxidation system with 6g of 28% industrial ammonia, 200g of tap water, and 10g of hydrogen peroxide. After the reaction, the reactor was opened and the liner was removed. The remaining hydrothermal liquid and residual solids were then filtered through a 70-mesh sieve to obtain the solid residue, which is the metal (copper, iron, nickel) portion. The remaining hydrothermal liquid after filtration was then filtered to recover the nano-titanium dioxide. Both were then dried in an oven at 60℃ for 100 minutes. In this case, the impurity-free metal support (iron, copper, nickel) had an impurity content of less than 0.1%, and the high-purity nano-titanium dioxide had a purity higher than 98%.

[0037] Example 2

[0038] First, 0.73g of waste LED electronic devices containing gallium arsenide were heated at 250℃ for 15 minutes at a rotation speed of 800 rpm, and treated in a hydrothermal-ammonia-oxidation system with 6g of 25% industrial ammonia, 200g of ultrapure water, and 15g of hydrogen peroxide. After the reaction, the reactor was opened and the liner was removed. The remaining hydrothermal liquid and residual solids were then filtered through a 50-mesh sieve to obtain the solid residue, which is the metal (copper, iron, nickel) portion. The remaining hydrothermal liquid after filtration was then filtered to recover the nano-titanium dioxide. Both were then dried in an oven at 80℃ for 200 minutes. In this case, the impurity-free metal support (iron, copper, nickel) had an impurity content of less than 0.1%, and the high-purity nano-titanium dioxide had a purity higher than 98%.

[0039] Example 3

[0040] First, 0.67g of waste LED electronic devices containing gallium arsenide were subjected to a hydrothermal-ammonia-oxidation system under the following conditions: heating at 280℃ for 25 minutes, rotation speed of 400 r / min, and the presence of 4g of 28% industrial ammonia, 200g of deionized water, and 8g of hydrogen peroxide. After the reaction, the reactor was opened and the liner was removed. The remaining hydrothermal liquid and residual solids were then filtered through a 100-mesh sieve to obtain the solid residue, which is the metal (copper, iron, nickel) portion. The remaining hydrothermal liquid after filtration was then filtered to recover the nano-titanium dioxide. Both were then dried in an oven at 110℃ for 50 minutes. In this implementation case, the impurity-free metal support (iron, copper, nickel) had an impurity content of less than 0.1%, and the high-purity nano-titanium dioxide had a purity higher than 98%.

[0041] Comparative Example 1

[0042] First, 0.82g of waste LED electronic devices containing gallium arsenide were subjected to a hydrothermal-ammonia-oxidation system under the conditions of heating at 250℃ for 15 minutes, rotating at 800 rpm, and using 200g of ultrapure water. After the reaction, the reactor was opened and the liner was removed. Then, the remaining hydrothermal liquid and residual solids were filtered through a 50-mesh sieve to obtain the solid residue, which is the metal (copper, iron, nickel) portion. The remaining hydrothermal liquid after sieving was then filtered to recover the nano-titanium dioxide. Both were then dried in an oven at 80℃ for 200 minutes. In this comparative example, the impurity content of the iron, copper, and nickel metal support was greater than 6.4%, and the purity of the nano-titanium dioxide was less than 72.3%.

[0043] The scope of protection of this invention is not limited to the above embodiments. Any variations and advantages that can be conceived by those skilled in the art without departing from the spirit and scope of this invention are included in this invention and are protected by the appended claims.

Claims

1. A method for recovering nano-titanium dioxide and metal support structures (iron, copper, nickel) from waste LED electronic devices, characterized in that, The hydrothermal fluid of the waste LED after being treated by the hydrothermal-ammonia-oxidation system is screened to separate the titanium dioxide from the metal support; then the nano titanium dioxide is recovered by filtration; finally, the nano titanium dioxide and the metal support are placed in an oven to dry, and finally nano titanium dioxide and the iron-copper-nickel metal support of the LED are obtained. The method specifically includes the following steps: (1) Place the waste LEDs into the lining of the reactor, and then add water, ammonia and oxidant to form a hydrothermal-ammonia-oxidation system; (2) Place the reactor liner into the reactor, then seal the reactor, set the experimental parameters, turn on the heating button, and wait for the reaction to finish; (3) The hydrothermal fluid obtained in step (2) is sieved to separate the iron, copper and nickel metal support from the hydrothermal fluid; (4) The remaining hydrothermal fluid after step (3) is filtered to separate and enrich nano-titanium dioxide from the water. (5) The metal support iron, copper and nickel obtained in step (3) and the nano titanium dioxide obtained in step (4) are placed in an oven for drying treatment, and finally impurity-free metal support iron, copper and nickel and high-purity nano titanium dioxide are obtained. In step (1), the ammonia water is selected from industrial ammonia water containing 25% to 28% ammonia; the oxidant is selected from one or more of ozone, oxygen, and hydrogen peroxide; the water is selected from one or more of deionized water, ultrapure water, tap water, and groundwater; the mass ratio of the waste LED, ammonia water, water, and oxidant is (0.2 to 4): (1 to 13) (100 to 250): (1 to 25). In step (2), the reaction temperature is 180-350℃; the reaction time is 5-60 min; and the rotation speed of the reaction vessel is 800 r / min.

2. The method as described in claim 1, characterized in that, In step (3), the mesh size of the sieve is 10 to 200 mesh.

3. The method as described in claim 1, characterized in that, In step (4), the filtration process is performed by vacuum filtration.

4. The method as described in claim 1, characterized in that, In step (5), the drying process is carried out at a temperature between 50 and 150°C for a time of 50 to 600 minutes.

5. The method as described in claim 1, characterized in that, In step (5), the impurity-free metal support iron-copper-nickel has an impurity content of less than 0.1%; the high-purity nano titanium dioxide has a purity of more than 97%.

6. The application of the method according to any one of claims 1-5 in the recovery of nano-titanium dioxide and metal support iron-copper-nickel from waste LEDs.

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