A regeneration method for YAG:Ce phosphor in white light LED

Abstract

The present invention discloses a method for regenerating YAG:Ce phosphor in white light LEDs. The method comprises the following steps: Step 1: material selection and classification, where the YAG:Ce phosphor is classified into two categories based on the process of coating the phosphor with different adhesives when used on a blue light chip; Step 2: cleaning, where both types of phosphor are cleaned with water; Step 3: crushing, where the cleaned phosphor is crushed and cleaned again; Step 4: filtering, where the filter residues are taken and dried; Step 5: where the dried phosphors of the two types are loaded into an atmosphere furnace and oxidized and calcined in an oxygen environment to remove adhesive substances on the phosphor surfaces; Step 6: where the debonded Type I phosphor waste is reduced to obtain regenerated Type I phosphor; and where the Type II phosphor is acid-washed with a hydrofluoric acid solution and filtered, the filter residue is dried, reduced, and coated with tetraethyl orthosilicate to obtain regenerated Type II phosphor. The method of the present invention regenerates YAG:Ce phosphor, promoting the recycling of waste resources.

Description

Technical Field

[0001] The invention belongs to the technical field of waste recycling and reuse, and in particular relates to a regeneration method for YAG:Ce phosphor in a white light LED. Background Art

[0002] LED lighting is widely used in modern society. However, the use of a large number of LED lamps shows that as the use time of LED increases, LED lamps will gradually age due to the high temperature at which LED emits light. Aging includes not only the aging of LED lamps, but also the aging of LED phosphors. Common aging phenomena of LED phosphors include: weakening of phosphor fluorescence intensity and drift of phosphor luminescence color coordinates. These changes lead to a decrease in the white light power of white LED lamps, affecting the white light synthesis and causing the luminous color to deviate from white. Therefore, white light LED lamps cannot be used if they are used for too long. It is generally believed that Y3Al5O 12 :Ce 3+ The thermal induced light decay of phosphors is caused by the activation of Ce ions 3+ Experts and scholars pointed out that when trivalent Ce 3+ Oxidized to tetravalent Ce 4 + Afterwards, Ce 4+ and Y in the matrix lattice 3+ 、Al 3+ Charge mismatch. At the same time, due to the difference in ionic radius, the aluminum oxide tetrahedron in the YAG structure gradually transforms into an aluminum oxide octahedron, causing microstructural distortion and further exacerbating the light decay of YAG:Ce. Therefore, the key factor in restoring the yellow YAG:Ce phosphor used in white LEDs is to reduce the Ce ion. The current method to extend the service life of YAG:Ce phosphors is to coat the phosphors with inorganic materials on the surface to inhibit oxygen intrusion and reduce surface defects. The most common recycling method for waste phosphors used in LED lamps is to recover the various elements in the LED phosphors, among which rare earth materials are particularly in need of recovery. After separating the various rare earths, new rare earth compounds are prepared. These methods recover a small amount of rare earth compounds from a large amount of phosphor, but the phosphors need to be completely dissolved, precipitated, and the rare earth elements separated and calcined. The recovery method is relatively complex and consumes a lot of acid and alkali.

[0003] Compared to extracting rare earth compounds from YAG:Ce phosphor waste and then reproducing it to synthesize phosphors, directly regenerating YAG:Ce phosphors significantly reduces the process flow, avoids the extraction and separation of various rare earth elements, and reduces raw material consumption. This not only conserves resources and human resources, but also significantly reduces costs. Considering the current scale of white light LED lamps, the recycling and regeneration of YAG:Ce phosphors is particularly important. Summary of the Invention

[0004] In view of this, the present invention provides a method for regenerating YAG:Ce phosphor in white light LEDs, which regenerates the YAG:Ce phosphor in failed white light LEDs to reduce costs, save resources, protect the environment, and promote the recycling of waste resources. This application provides the following technical solutions:

[0005] A method for regenerating YAG:Ce phosphor in white light LEDs comprises the following steps: step 1, material selection and classification, wherein the YAG:Ce phosphor is classified into two categories according to the process of coating the YAG:Ce phosphor with different glues on a blue light chip during use, wherein the epoxy organic glue containing three elements of C, H and O is classified as type I, and the glue containing silica gel is classified as type II, and the two types of phosphor waste are subjected to regeneration processes respectively; step 2, cleaning, wherein both types of phosphor are cleaned with clean water; step 3, crushing, wherein the cleaned phosphor is crushed and cleaned again; step 4, filtering, wherein the filter residues are respectively taken and dried; step 5, wherein the dried type I phosphor and type II phosphor are respectively loaded into an atmosphere furnace, and oxidized and calcined in an oxygen environment. Burn to remove the glue-like substances on the surface of the phosphor; Step 6, reduce the Class I phosphor waste after degumming, cool the Class I phosphor to room temperature in an atmosphere furnace, close the oxygen valve, and then evacuate the oxygen in the atmosphere furnace. After extracting the oxygen, pass nitrogen and continue to drain the oxygen, and finally pass a reducing gas, wherein the reducing gas is hydrogen and nitrogen. After passing the reducing gas, heat up and calcine again, cool in a reducing atmosphere, and take out to obtain the regenerated Class I phosphor; the Class II phosphor is cooled in an aerobic environment of an atmosphere furnace, and a calcined product is taken out to obtain the calcined product. The calcined product is acid-washed with a hydrofluoric acid solution and filtered, and the filter residue is dried and reduced and coated with tetraethyl orthosilicate to finally obtain the regenerated Class II phosphor.

[0006] Preferably, the crushed particle size is 0.2-0.5 mm.

[0007] Preferably, in step 4, the temperature for drying the filter residue is 60-80°C.

[0008] Preferably, in step 5, the calcination temperature of Class I phosphor waste is 500-720° C., the calcination temperature of Class II phosphor waste is 700-900° C., and the calcination time is 1.5-2 hours.

[0009] Preferably, in the step 6, during the reduction treatment of Class I phosphor waste, the volume ratio of hydrogen is 10%, and the total air flow is controlled at 50-70 cm 3 / min, after ventilation for 15 minutes, heat up the atmosphere furnace, and control the heating rate at 15-20℃ / min. When the temperature of the atmosphere furnace is controlled at 950-1200℃, keep it warm for 2 hours, and finally maintain the reducing atmosphere in the reduction furnace and cool it to room temperature;

[0010] Preferably, the mass percent concentration of the hydrofluoric acid solution is 4%.

[0011] Preferably, the calcined product is dried and placed in an atmosphere furnace, and subjected to the same reduction treatment as the Class I phosphor waste to obtain a reduced product.

[0012] Preferably, the tetraethyl orthosilicate coating treatment process is specifically as follows: tetraethyl orthosilicate, ethanol, and deionized water are formed into a mixed solution, which is fully stirred, a dilute nitric acid solution is added to the mixed solution, and the pH value of the mixed solution is adjusted to 1-2. After the mixed solution is completely hydrolyzed, the pH value is adjusted to 6-7 with an ammonia solution to obtain a dispersion, the reduction product is added, and urea is added while stirring. The solution is heated to 95°C and stirred for 2 hours. After the reaction is completed, the product of the regenerated coated Class II phosphor is obtained after filtration and drying.

[0013] Working principle of the present invention:

[0014] 1. For Type I phosphors

[0015] 1. Oxidation reaction

[0016] After cleaning and crushing, the Type I YAG:Ce can be oxidized and calcined in an oxygen environment for 1.5-2 hours to burn off the organic glue on the surface of the YAG:Ce phosphor. The specific reaction is

[0017] 4C l H m O n +(4l+m–2n)O2→4lCO2+2mH2O

[0018] 2. Reduction reaction

[0019] Afterwards, in a hydrogen environment, Ce in YAG:Ce 3+ The following reduction reaction will occur:

[0020] 2Ce 4+ +H2→2Ce 3+ +2H +

[0021] These H + With YAG(Y3Al5O 12 ) in O 2– Water will be formed, and the specific reaction is as follows:

[0022] 2H + +O 2– →H2O

[0023] This reaction is based on the following three points:

[0024] (1) Under a reducing atmosphere and at a suitable high temperature, cerium dioxide undergoes the following reaction (Jaewon Lee, Eungchul Kim, Chulwoo Bae, Hyunho Seok, Jinil Cho, Kubra Aydin, Taesung Kim, Improvement of oxide chemical mechanical polishing performance by increasing Ce 3+ / Ce 4+ ratio in ceria slurry via hydrogen reduction Materials Science in Semiconductor Processing, 2023,159: 107349):

[0025] CeO2+xH2→2H x CeO2

[0026] As the reaction proceeds, H x CeO2 will further reduce

[0027] 2H x CeO2+xH2→Ce2O 4–2x +2xH2O

[0028] At sufficiently high temperatures, that is, around 1000°C, x can be halved, at which point the following overall reaction can proceed:

[0029] 2CeO2+H2→Ce2O3+H2O

[0030] In YAG crystals, due to the lack of surrounding O, Ce 4+ It is easier to restore.

[0031] (2) Al in YAG crystal 3+ and Y 2+ , is not a variable valence element and will not be reduced under such conditions.

[0032] (3) The melting point of YAG is about 1950℃, and it will not melt in an environment around 1000℃.

[0033] Under a reducing atmosphere, Ce remains in the trivalent form after cooling to room temperature.

[0034] At this time, the Ce in YAG:Ce is reduced, while the oxide film on the surface of the phosphor is not affected, so the YAG:Ce in the film can be 3+ Phosphor. At the same time, when the tetravalent Ce4+ Reduced to trivalent Ce 3+ Afterwards, due to the difference in ionic radius and charge, Ce 3+ The surrounding lattice undergoes a certain amount of fine-tuning to balance the charge and adapt to the new Ce 3+ Ionic radius. The fine-tuned lattice can maintain trivalent Ce 3+ Exist stably within a certain range.

[0035] 2. For Type II phosphors

[0036] 1. Oxidation reaction

[0037] After cleaning and crushing, the Type I YAG:Ce is oxidized and calcined in an oxygen environment for 1.5-2 hours to burn the organic silica gel on the surface of the YAG:Ce phosphor, but some SiO2 will remain on the surface of the YAG:Ce phosphor. The specific reaction is

[0038] 4Si l H m O n +(4l+m–2n)O2→4lSiO2+2mH2O

[0039] 2. Pickling process

[0040] Hydrofluoric acid can dissolve the SiO2 remaining on the surface of YAG:Ce phosphor, while YAG will not be dissolved. The specific reaction is as follows:

[0041] SiO2+4HF→SiF4+2H2O

[0042] 3. Reduction reaction

[0043] Afterwards, in a hydrogen environment, Ce in YAG:Ce 3+ The following reduction reaction will occur:

[0044] 2Ce 4+ +H2→2Ce 3+ +2H +

[0045] These H + With YAG(Y3Al5O 12 ) in O 2– Water will be formed, and the specific reaction is as follows:

[0046] 2H + +O 2– →H2O

[0047] Similarly, when tetravalent Ce 4+ Reduced to trivalent Ce 3+ Afterwards, due to the difference in ionic radius and charge, Ce3+ The surrounding lattice undergoes a certain amount of fine-tuning to balance the charge and adapt to the new Ce 3+ Ionic radius. The fine-tuned lattice can maintain trivalent Ce 3+ Exist stably within a certain range.

[0048] 4. When wrapping

[0049] After the acid washing reaction, the SiO2 coating on the YAG surface is destroyed and washed away. To maintain the long life of the YAG:Ce phosphor, the YAG:Ce phosphor must be coated. During the coating process:

[0050] Complete hydrolysis of TEOS,

[0051] Si(OC2H5)4+4H2O→Si(OH)4+4C2H5OH

[0052] xSi(OH)4→(O-Si-O) x +2xH2O

[0053] When the pH of the mixed solution reaches 1-2, the entire system becomes strongly acidic, completely hydrolyzing the ethyl orthosilicate to form orthosilicic acid. Ammonia is added to adjust the pH to 6-7, making the system weakly acidic. At this point, single molecules of orthosilicic acid are highly chemically active. Due to crystal defects on the surface of the YAG:Ce phosphor, these molecules disperse into the water and possess a certain number of hydroxyl groups, which bind to the orthosilicic acid, forming junctions. As urea uniformly hydrolyzes in a high-temperature water bath, the reaction system gradually becomes alkaline, and the hydrolysis product, orthosilicic acid, gradually adsorbs onto the surface of the phosphor particles and undergoes dehydration and condensation. As the reaction time increases, the system's alkalinity increases, accelerating the polymerization of the hydrolysis products and forming a silicon oxide coating.

[0054] Beneficial effects of the present invention:

[0055] The invention proposes a white light LED yellow YAG:Ce phosphor regeneration method, the processing method is simple, through removing the glue, Ce 4+ The YAG:Ce phosphor can be regenerated through a reduction treatment. The brightness and optimal color coordinates are restored after regeneration, which is beneficial to resource conservation and environmental protection, and promotes the recycling of waste resources. DETAILED DESCRIPTION

[0056] The present embodiment provides a method for regenerating YAG:Ce phosphor in a white light LED, comprising the following steps: A method for regenerating yellow YAG:Ce phosphor in a white light LED, comprising the following steps:

[0057] 1) Material selection: When recycling, YAG:Ce phosphors are classified into two types: one is when the glue used is epoxy or other materials containing the three elements C, H, and O. This type of YAG:Ce phosphor is classified as Class I phosphor. The other is when the glue used is mainly silicone. This type of YAG:Ce phosphor is classified as Class II phosphor.

[0058] 2) introducing the Class I YAG:Ce phosphor into a mechanical cleaning machine and washing the waste Class I YAG:Ce phosphor with clean water;

[0059] 3) The waste Class I YAG:Ce phosphor that has been washed with clean water is crushed into particles of 0.2-0.5 mm using a crusher;

[0060] 4) The crushed Class I YAG:Ce phosphor is again introduced into a mechanical cleaning machine for cleaning;

[0061] 5) introducing the crushed and cleaned Class I YAG:Ce phosphor into a filter press, filtering, and removing the filter residue;

[0062] 6) Drying the Type I YAG:Ce phosphor residue at 60-80°C;

[0063] 7) The dried Class I waste YAG:Ce phosphor is oxidized and calcined in an atmosphere furnace under an oxygen environment at 500-720° C. for 1.5-2 hours to remove organic gum substances on the surface of the waste YAG:Ce phosphor.

[0064] 8) The Class I waste YAG:Ce phosphor, after burning off the surface organic glue, is left in the atmosphere furnace to cool to room temperature. The oxygen valve is closed and the oxygen in the atmosphere furnace is then evacuated. After the oxygen is evacuated, nitrogen is introduced to further drain the oxygen. A reducing atmosphere is then introduced, with a hydrogen and nitrogen volume ratio of 10% and a total airflow of 50-70 cm3. 3 / min. 15 minutes after ventilation, heat the atmosphere furnace at a rate of 15-20°C / min. When the atmosphere furnace temperature is controlled at 950-1200°C, maintain the temperature for 2 hours. Finally, maintain the reducing atmosphere in the reduction furnace and cool to room temperature to obtain finished product No. 1.

[0065] 9) For the Class II YAG:Ce phosphor, introduce the Class II YAG:Ce phosphor into a mechanical cleaning machine and wash the waste Class II YAG:Ce phosphor with clean water;

[0066] 10) The waste type II YAG:Ce phosphor washed with clean water is crushed into particles of 0.2-0.5 mm using a crusher;

[0067] 11) The crushed Type II YAG:Ce phosphor is again introduced into a mechanical cleaning machine for cleaning;

[0068] 12) introducing the crushed and cleaned type II YAG:Ce phosphor into a filter press, filtering, and removing the filter residue;

[0069] 13) Drying the Type II YAG:Ce phosphor residue at 60-80°C;

[0070] 14) The dried Class II waste YAG:Ce phosphor is oxidatively calcined in an atmosphere furnace at 700-900° C. in an oxygen environment for 1.5-2 hours to remove organic gum substances on the surface of the waste YAG:Ce phosphor.

[0071] 15) The calcined Class II waste YAG:Ce phosphor is cooled in an oxygen environment and taken out to obtain a calcined product A.

[0072] 16) Pour 90 kg of deionized water into the batching tank, add 10 kg of 40% high-concentration hydrofluoric acid solution, and stir continuously to obtain 100 kg of hydrofluoric acid solution with a mass concentration of 4%. Introduce the prepared 4% hydrofluoric acid solution into storage tank I.

[0073] 17) 50 l of hydrofluoric acid solution in storage tank No. 1 was introduced into reactor No. 1, and 20-30 kg of calcined product A was added from feed port No. 0. The mixture was stirred for 30 min and cleaned to remove SiO2 on the surface of calcined product A to obtain cleaned product B.

[0074] 18) The cleaning product B is drawn out from the bottom of the reactor, enters a filter press, and is filtered and washed three times, filtered three times, and the filter residue is removed.

[0075] 19) drying the Type II YAG:Ce phosphor residue at 60-80° C. to obtain a drying product C;

[0076] 20) Place the dried product C in an atmosphere furnace, close the oxygen valve, and exhaust the oxygen in the atmosphere furnace. After the oxygen is extracted, pass nitrogen to continue to drain the oxygen. Then pass the reducing gas. The reducing atmosphere is provided by hydrogen and nitrogen, where the volume ratio of hydrogen is 10%, and the total airflow is controlled at 50-70 cm 3 / min. After 15 minutes of ventilation, the atmosphere furnace was heated at a rate of 15-20°C / min. When the atmosphere furnace temperature was controlled at 950-1200°C, it was kept at this temperature for 2 hours. Finally, the reducing atmosphere in the reduction furnace was maintained and the mixture was cooled to room temperature to obtain the reduced product D.

[0077] 21) In the batch tank II, pour 5-10 kg of tetraethyl orthosilicate (TEOS) from the feed port No. 1, add 25-50 l of ethanol to the feed port No. II, add 25-50 l of deionized water to the feed port No. III to form a mixed solution, stir thoroughly, add dilute nitric acid solution to the feed port No. IV, adjust the pH value of the mixed solution to 1-2, and stir continuously.

[0078] 22) After the reactants are completely hydrolyzed, the pH is adjusted to 6-7 with aqueous ammonia solution to obtain dispersion E.

[0079] 23) Introduce 50 l of dispersion E from the batching tank into the reaction tank, add 25-50 kg of reduction product D, stir continuously, add 25-50 kg of urea, stir continuously, and heat to 95 ° C and stir for 2 hours.

[0080] 24) After the reaction is completed, the coated phosphor No. 2 product is obtained after filtering and drying.

[0081] The regeneration method of the present invention is described below by means of specific examples:

[0082] Implementation Method 1

[0083] 1) Material selection: When recycling, YAG:Ce phosphors are classified into two types: one is when the glue used is epoxy with three elements of C, H, and O, and this type of YAG:Ce phosphor is classified as Class I phosphor; the other is when the glue used is silicone as the main glue material, and this type of YAG:Ce phosphor is classified as Class II phosphor;

[0084] 2) introducing the Class I YAG:Ce phosphor into a mechanical cleaning machine and washing the waste Class I YAG:Ce phosphor with clean water;

[0085] 3) The waste Class I YAG:Ce phosphor that has been washed with clean water is crushed into 0.5 mm particles using a crusher;

[0086] 4) The crushed Class I YAG:Ce phosphor is again introduced into a mechanical cleaning machine for cleaning;

[0087] 5) introducing the crushed and cleaned Class I YAG:Ce phosphor into a filter press, filtering, and removing the filter residue;

[0088] 6) drying the Type I YAG:Ce phosphor residue at 60°C;

[0089] 7) The dried Class I waste YAG:Ce phosphor was oxidatively calcined in an atmosphere furnace under an oxygen environment at 500° C. for 1.5 hours to remove organic glue substances on the surface of the waste YAG:Ce phosphor;

[0090] 8) The Class I waste YAG:Ce phosphor with the organic glue on the surface burned off was kept in the atmosphere furnace and cooled to room temperature. The oxygen valve was closed and the oxygen in the atmosphere furnace was evacuated. After the oxygen was evacuated, nitrogen was introduced to continue to drain the oxygen. Then, a reducing gas was introduced. The reducing atmosphere was provided by hydrogen and nitrogen, with the volume ratio of hydrogen being 10%. The total airflow was controlled at 50 cm 3 / min, after ventilation for 15 minutes, heat up the atmosphere furnace, and control the heating rate at 20℃ / min. When the temperature of the atmosphere furnace is controlled at 950℃, keep it warm for 2 hours. Finally, maintain the reducing atmosphere in the reduction furnace and cool it to room temperature to obtain finished product No. 1;

[0091] 9) For the Class II YAG:Ce phosphor, introduce the Class II YAG:Ce phosphor into a mechanical cleaning machine and wash the waste Class II YAG:Ce phosphor with clean water;

[0092] 10) The waste type II YAG:Ce phosphor washed with clean water is crushed into 0.5 mm particles using a crusher;

[0093] 11) The crushed Type II YAG:Ce phosphor is again introduced into a mechanical cleaning machine for cleaning;

[0094] 12) introducing the crushed and cleaned type II YAG:Ce phosphor into a filter press, filtering, and removing the filter residue;

[0095] 13) drying the Type II YAG:Ce phosphor residue at 60°C;

[0096] 14) The dried Class II waste YAG:Ce phosphor was oxidatively calcined in an atmosphere furnace at 700° C. in an oxygen environment for 1.5 hours to remove organic glue substances on the surface of the waste YAG:Ce phosphor;

[0097] 15) Cooling the calcined Class II waste YAG:Ce phosphor in an oxygen environment and taking out the calcined product A;

[0098] 16) Pour 90 kg of deionized water into the batching tank, add 10 kg of 40% high-concentration hydrofluoric acid solution, and stir continuously to obtain 100 kg of 4% hydrofluoric acid solution. The prepared 4% hydrofluoric acid solution is introduced into storage tank 1;

[0099] 17) 50 l of hydrofluoric acid solution in storage tank No. 1 was introduced into reactor No. 1, and 20 kg of calcined product A was added from feed port No. 0. The mixture was stirred for 30 min and cleaned to remove SiO2 on the surface of calcined product A to obtain cleaned product B;

[0100] 18) The cleaning product B is drawn out from the bottom of the reactor, enters a filter press, and is filtered and washed three times, filtered three times, and the filter residue is removed.

[0101] 19) drying the Type II YAG:Ce phosphor residue at 60° C. to obtain a drying product C;

[0102] 20) Place the dried product C in an atmosphere furnace, close the oxygen valve, and exhaust the oxygen in the atmosphere furnace. After the oxygen is exhausted, pass nitrogen to continue to drain the oxygen, and then pass the reducing gas. The reducing atmosphere is provided by hydrogen and nitrogen, wherein the volume ratio of hydrogen is 10%, and the total airflow is controlled at 50cm 3 / min. After 15 minutes of ventilation, the atmosphere furnace was heated at a rate of 20°C / min. When the temperature of the atmosphere furnace was controlled at 950°C, it was kept at this temperature for 2 hours. Finally, the reducing atmosphere in the reduction furnace was maintained and cooled to room temperature to obtain the reduced product D.

[0103] 21) In the batch tank II, pour 5 kg of tetraethyl orthosilicate (TEOS) from the feed port No. 1, add 25 l of ethanol to the feed port No. II, add 25 l of deionized water to the feed port No. III to form a mixed solution, stir thoroughly, add dilute nitric acid solution to the feed port No. IV, adjust the pH value of the mixed solution to 2, and stir continuously;

[0104] 22) After the reactants are completely hydrolyzed, the pH is adjusted to 7 with aqueous ammonia solution to obtain dispersion E;

[0105] 23) Introduce 50 l of dispersion E from the batching tank into the reaction tank, add 25 kg of reduction product D, stir continuously, add 25 kg of urea, stir continuously, and heat to 95 ° C and stir for 2 hours;

[0106] 24) After the reaction is completed, the coated phosphor No. 2 product is obtained after filtering and drying.

[0107] Implementation Method 2

[0108] 1) Material selection: When recycling, YAG:Ce phosphors are classified into two types: one is when the glue used is epoxy with three elements of C, H, and O, and this type of YAG:Ce phosphor is classified as Class I phosphor; the other is when the glue used is silicone as the main glue material, and this type of YAG:Ce phosphor is classified as Class II phosphor;

[0109] 2) introducing the Class I YAG:Ce phosphor into a mechanical cleaning machine and washing the waste Class I YAG:Ce phosphor with clean water;

[0110] 3) The waste Class I YAG:Ce phosphor that has been washed with clean water is crushed into 0.3 mm particles using a crusher;

[0111] 4) The crushed Class I YAG:Ce phosphor is again introduced into a mechanical cleaning machine for cleaning;

[0112] 5) introducing the crushed and cleaned Class I YAG:Ce phosphor into a filter press, filtering, and removing the filter residue;

[0113] 6) drying the Type I YAG:Ce phosphor residue at 70°C;

[0114] 7) The dried Class I waste YAG:Ce phosphor is oxidized and calcined in an atmosphere furnace at 600° C. in an oxygen environment for 2 hours to remove organic glue substances on the surface of the waste YAG:Ce phosphor.

[0115] 8) The Class I waste YAG:Ce phosphor with the surface organic glue burned off was continued to cool to room temperature in the atmosphere furnace. The oxygen valve was closed and the oxygen in the atmosphere furnace was evacuated. After the oxygen was evacuated, nitrogen was introduced to continue to drain the oxygen. Then, a reducing gas was introduced. The reducing atmosphere was provided by hydrogen and nitrogen, with the volume ratio of hydrogen being 10%. The total airflow was controlled at 60 cm 3 / min. After 15 minutes of ventilation, the atmosphere furnace was heated at a rate of 17°C / min. When the temperature of the atmosphere furnace was controlled at 1000°C, it was kept warm for 2 hours. Finally, the reducing atmosphere in the reduction furnace was maintained and cooled to room temperature to obtain finished product No. 1.

[0116] 9) For the Class II YAG:Ce phosphor, introduce the Class II YAG:Ce phosphor into a mechanical cleaning machine and wash the waste Class II YAG:Ce phosphor with clean water;

[0117] 10) The waste type II YAG:Ce phosphor washed with clean water is crushed into 0.3 mm particles using a crusher;

[0118] 11) The crushed Type II YAG:Ce phosphor is again introduced into a mechanical cleaning machine for cleaning;

[0119] 12) introducing the crushed and cleaned type II YAG:Ce phosphor into a filter press, filtering, and removing the filter residue;

[0120] 13) drying the Type II YAG:Ce phosphor residue at 70°C;

[0121] 14) The dried Class II waste YAG:Ce phosphor was oxidatively calcined in an atmosphere furnace at 800° C. in an oxygen environment for 2 hours to remove organic glue substances on the surface of the waste YAG:Ce phosphor;

[0122] 15) Cooling the calcined Class II waste YAG:Ce phosphor in an oxygen environment and taking out the calcined product A;

[0123] 16) Pour 90 kg of deionized water into the batching tank, add 10 kg of 40% high-concentration hydrofluoric acid solution, and stir continuously to obtain 100 kg of 4% hydrofluoric acid solution. The prepared 4% hydrofluoric acid solution is introduced into storage tank 1;

[0124] 17) 50 l of hydrofluoric acid solution in storage tank No. 1 was introduced into reactor No. 1, and 25 kg of calcined product A was added from feed port No. 0. The mixture was stirred for 30 min and cleaned to remove SiO2 on the surface of calcined product A to obtain cleaned product B;

[0125] 18) The cleaned product B was drawn out from the bottom of the reactor, passed into a filter press, filtered, and washed three times, filtered three times, and the filter residue was removed;

[0126] 19) drying the Type II YAG:Ce phosphor residue at 70° C. to obtain a drying product C;

[0127] 20) Place the dried product C in an atmosphere furnace, close the oxygen valve, and exhaust the oxygen in the atmosphere furnace. After the oxygen is extracted, pass nitrogen to continue to drain the oxygen, and then pass the reducing gas. The reducing atmosphere is provided by hydrogen and nitrogen, wherein the volume ratio of hydrogen is 10%, and the total airflow is controlled at 60cm 3 / min, and after 15 minutes of ventilation, heat the atmosphere furnace at a heating rate of 17℃ / min. When the temperature of the atmosphere furnace is controlled at 1000℃, keep it warm for 2 hours. Finally, maintain the reducing atmosphere in the reduction furnace and cool it to room temperature to obtain the reduced product D;

[0128] 21) In the batch tank II, pour 10 kg of TEOS from the feed port No. 1, add 50 l of ethanol to the feed port No. II, and add 50 l of deionized water to the feed port No. III to form a mixed solution. Stir thoroughly, add dilute nitric acid solution to the feed port No. IV, adjust the pH value of the mixed solution to 1, and stir continuously;

[0129] 22) After the reactants are completely hydrolyzed, the pH is adjusted to 6 with aqueous ammonia solution to obtain dispersion E;

[0130] 23) Introduce 50 l of dispersion E from the batching tank into the reaction tank, add 50 kg of reduction product D, stir continuously, add 50 kg of urea, stir continuously, and heat to 95 ° C and stir for 2 hours;

[0131] 24) After the reaction is completed, the coated phosphor No. 2 product is obtained after filtering and drying.

[0132] Implementation 3

[0133] 1) Material selection: When recycling, YAG:Ce phosphors are classified into two types: one is when the glue used during the application is epoxy and other materials with the three elements C, H, and O. This type of YAG:Ce phosphor is classified as Class I phosphor. The other type of YAG:Ce phosphors are when the glue used during the application is silicone as the main glue material. This type of YAG:Ce phosphor is classified as Class II phosphor.

[0134] 2) introducing the Class I YAG:Ce phosphor into a mechanical cleaning machine and washing the waste Class I YAG:Ce phosphor with clean water;

[0135] 3) The waste Class I YAG:Ce phosphor that has been washed with clean water is crushed into 0.2 mm particles using a crusher;

[0136] 4) The crushed Class I YAG:Ce phosphor is again introduced into a mechanical cleaning machine for cleaning;

[0137] 5) introducing the crushed and cleaned Class I YAG:Ce phosphor into a filter press, filtering, and removing the filter residue;

[0138] 6) drying the Type I YAG:Ce phosphor residue at 80°C;

[0139] 7) The dried Class I waste YAG:Ce phosphor was oxidatively calcined in an atmosphere furnace under an oxygen environment at 720°C for 2 hours to remove organic glue substances on the surface of the waste YAG:Ce phosphor;

[0140] 8) The Class I waste YAG:Ce phosphor with the organic glue on the surface burned off was kept in the atmosphere furnace and cooled to room temperature. The oxygen valve was closed and the oxygen in the atmosphere furnace was evacuated. After the oxygen was evacuated, nitrogen was introduced to continue to drain the oxygen. Then, a reducing gas was introduced. The reducing atmosphere was provided by hydrogen and nitrogen, with the volume ratio of hydrogen being 10%. The total airflow was controlled at 70 cm 3 / min, after ventilation for 15 minutes, heat up the atmosphere furnace, and control the heating rate at 15℃ / min. When the temperature of the atmosphere furnace is controlled at 1200℃, keep it warm for 2 hours, and finally maintain the reducing atmosphere in the reduction furnace, cool to room temperature, and obtain finished product No. 1;

[0141] 9) For the Class II YAG:Ce phosphor, introduce the Class II YAG:Ce phosphor into a mechanical cleaning machine and wash the waste Class II YAG:Ce phosphor with clean water;

[0142] 10) The waste type II YAG:Ce phosphor washed with clean water is crushed into 0.2 mm particles using a crusher;

[0143] 11) The crushed Type II YAG:Ce phosphor is again introduced into a mechanical cleaning machine for cleaning;

[0144] 12) introducing the crushed and cleaned type II YAG:Ce phosphor into a filter press, filtering, and removing the filter residue;

[0145] 13) drying the Type II YAG:Ce phosphor residue at 80°C;

[0146] 14) The dried Class II waste YAG:Ce phosphor was oxidatively calcined in an atmosphere furnace at 900° C. in an oxygen environment for 2 hours to remove organic glue substances on the surface of the waste YAG:Ce phosphor;

[0147] 15) Cooling the calcined Class II waste YAG:Ce phosphor in an oxygen environment and taking out the calcined product A;

[0148] 16) Pour 90 kg of deionized water into the batching tank, add 10 kg of 40% high-concentration hydrofluoric acid solution, and stir continuously to obtain 100 kg of 4% hydrofluoric acid solution. The prepared 4% hydrofluoric acid solution is introduced into storage tank 1;

[0149] 17) 50 l of hydrofluoric acid solution in storage tank No. 1 was introduced into reactor No. 1, and 20 kg of calcined product A was added from feed port No. 0. The mixture was stirred for 30 min and cleaned to remove SiO2 on the surface of calcined product A to obtain cleaned product B;

[0150] 18) The cleaned product B was drawn out from the bottom of the reactor, passed into a filter press, filtered, and washed three times, filtered three times, and the filter residue was removed;

[0151] 19) drying the Type II YAG:Ce phosphor residue at 80° C. to obtain a drying product C;

[0152] 20) Place the dried product C in an atmosphere furnace, close the oxygen valve, and exhaust the oxygen in the atmosphere furnace. After the oxygen is exhausted, pass nitrogen to continue to drain the oxygen. Then pass the reducing gas. The reducing atmosphere is provided by hydrogen and nitrogen, where the volume ratio of hydrogen is 10%, and the total airflow is controlled at 70cm 3 / min, after ventilation for 15 minutes, the atmosphere furnace was heated, and the heating rate was controlled at 15℃ / min. When the temperature of the atmosphere furnace was controlled at 1200℃, it was kept warm for 2 hours. Finally, the reducing atmosphere in the reduction furnace was maintained and cooled to room temperature to obtain the reduced product D;

[0153] 21) In the batch tank II, pour 10 kg of TEOS from the feed port No. 1, add 50 l of ethanol to the feed port No. II, and add 50 l of deionized water to the feed port No. III to form a mixed solution. Stir thoroughly, add dilute nitric acid solution to the feed port No. IV, adjust the pH value of the mixed solution to 1, and stir continuously;

[0154] 22) After the reactants are completely hydrolyzed, the pH is adjusted to 6 with aqueous ammonia solution to obtain dispersion E;

[0155] 23) Introduce 50 l of dispersion E from the batching tank into the reaction tank, add 50 kg of reduction product D, stir continuously, add 50 kg of urea, stir continuously, and heat to 95 ° C and stir for 2 hours;

[0156] 24) After the reaction is completed, the coated phosphor No. 2 product is obtained after filtering and drying.

[0157] Phosphor recovery experiment

[0158] Referring to CIE 127:2007 "LED Measurement Methods," we took a certain amount of waste phosphor and measured the relative brightness of the LED light using a brightness meter. After packaging the waste phosphor into an LED light, we measured the color coordinates of the LED light using a color coordinate meter. We then took recycled phosphor and conducted a comparative experiment. Considering that the color coordinates of standard white light are (0.333, 0.333), the color coordinate offset w is calculated as follows:

[0159]

[0160] The brightness recovery factor A is calculated as follows:

[0161]

[0162] The color coordinate recovery rate R is calculated as follows:

[0163]

[0164] Where x, y are the color coordinates (x, y) of the waste phosphor packaged into LED lights, B 废旧LED is the relative brightness of the waste phosphor, B 再生LED is the relative brightness of the regenerated phosphor, w 废旧LED The color coordinate deviation rate of LED lamp assembled with waste phosphor, w 再生LED The deviation rate of the color coordinates of LED lamps assembled with recycled phosphor.

[0165] Table 1 shows the regeneration performance of YAG:Ce phosphor. Although the different implementations slightly varied the fluorescence performance of the regenerated YAG:Ce phosphor, overall, the brightness recovered by more than 5 times after regeneration, and the optimal color coordinate recovery rate exceeded 86%. Considering that the depleted phosphor did not deviate much from white light, the regeneration method of the present invention is effective.

[0166] Table 1 Regeneration performance of YAG:Ce phosphor

[0167]

[0168] This embodiment has the following advantages: the method is simple, the YAG:Ce phosphor solid waste is effectively regenerated, and certain economic and social benefits are achieved.

[0169] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for regenerating YAG:Ce phosphor in white light LEDs, characterized by: The method comprises the following steps: step 1, material selection and classification, which is divided into two categories according to the process of mixing YAG:Ce phosphor with different glues and coating on blue light chips during use, wherein the glue is epoxy organic glue containing three elements of C, H and O as type I, and the glue is silica gel as type II, and the two types of phosphor waste are subjected to regeneration processes respectively; step 2, cleaning, which is to use clean water to clean both types of phosphors; step 3, crushing, which is to crush the phosphors to a particle size of 0.2-0.5 mm and then clean them again; step 4, filtering, taking the filter residue and drying it, and the drying temperature of the filter residue is 60-80°C; step 5, the dried type I phosphor and type II phosphor, The waste phosphors are loaded into an atmosphere furnace respectively, and oxidized and calcined in an oxygen environment to remove the glue substances on the surface of the phosphors. The calcination temperature of Class I phosphor waste is 500-720°C, and the calcination temperature of Class II phosphor waste is 700-900°C, and the calcination time is 1.5-2 hours. In step 6, the Class I phosphor waste after degumming is reduced. The Class I phosphor is cooled to room temperature in the atmosphere furnace, the oxygen valve is closed, and then the oxygen in the atmosphere furnace is exhausted. After the oxygen is exhausted, nitrogen is introduced and the oxygen is continuously drained. Finally, a reducing gas is introduced. The reducing gas is hydrogen and nitrogen, and the total airflow is controlled at 50-70 cm 3 / min, wherein the volume ratio of hydrogen is 10%, after passing a reducing gas, the temperature is raised to 950-1200℃ and calcined again for 2 hours, and cooled in a reducing atmosphere to obtain a regenerated Class I phosphor, wherein the heating rate is controlled at 15-20℃ / min; the Class II phosphor is cooled in an oxygen environment of an atmosphere furnace, and a calcined product is obtained. The calcined product is acid-washed with a hydrofluoric acid solution with a mass percentage concentration of 4-5%, and filtered. The filter residue is dried, reduced, and coated with tetraethyl orthosilicate to finally obtain a regenerated Class II phosphor.

2. The method for regenerating YAG:Ce phosphor in white light LED according to claim 1, characterized in that: The specific process of tetraethyl orthosilicate coating treatment is as follows: tetraethyl orthosilicate, ethanol, and deionized water are formed into a mixed solution, which is fully stirred, and a dilute nitric acid solution is added to the mixed solution to adjust the pH value of the mixed solution to 1-2. After the mixed solution is completely hydrolyzed, the pH value is adjusted to 6-7 with an ammonia solution to obtain a dispersion, the reduction product is added, and urea is added while stirring. The solution is heated to 95°C and stirred for 2-3 hours. After the reaction is completed, the regenerated coated Class II phosphor product is obtained after filtration and drying.

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