A method for separating indium oxide and tin oxide from indium tin oxide waste targets by a vacuum method

Abstract

The present invention discloses a method for separating indium oxide and tin oxide from indium tin oxide waste targets by a vacuum method, which relates to the technical field of resource recycling and utilization, and includes: taking indium tin oxide waste target raw materials, adding indium to the indium tin oxide waste target raw materials, and then heating and keeping warm under vacuum conditions; after the heat preservation ends, the low-valent oxide of indium volatilizes into the volatiles to obtain indium oxide; tin oxide remains in the condensate to obtain tin oxide. According to the present invention, indium oxide can generate volatile low-valent oxide (In2O) when heated in indium melt, and the generated low-valent oxide can volatilize to the condensation area for condensation, thereby realizing the separation of indium oxide and tin oxide, and realizing the resource recycling and utilization of indium tin oxide waste target materials.

Description

Technical Field

[0001] The present invention relates to the technical field of resource recycling, and particularly relates to a method for separating indium oxide and tin oxide from indium tin oxide waste targets by a vacuum method. Background Art

[0002] Indium resources are scarce. There are almost no industrial exploitable ore bodies of indium alone in nature. It mostly occurs in non-ferrous metal sulfides. Metallic indium is mainly recovered from the by-products of non-ferrous metal smelting and secondary resources of indium. During the smelting process, due to the similar physical and chemical properties of tin and indium, tin is often enriched and recovered together with indium. More than 80% of the indium production is used to produce indium tin oxide (ITO). The scraps, waste targets, or waste LCD screens generated during the production of ITO are all mixtures of indium tin oxides.

[0003] As a key material for the production of transparent conductive films, the usage amount of ITO is increasing rapidly. Therefore, the output of ITO waste targets is also increasing rapidly. Recycling indium from ITO waste targets is becoming increasingly important for resources, the environment, and the economy. At present, the methods for recycling indium from ITO waste targets at home and abroad are mainly divided into two categories: pyrometallurgy and hydrometallurgy. Pyrometallurgy includes processes such as reduction, separation, and purification. Hydrometallurgy includes acid leaching, solvent extraction, ion exchange, etc. Hydrometallurgical recycling is the mainstream process for recycling indium from ITO waste targets in the industry at present.

[0004] (1) Patent document CN1420184A discloses a method for "extracting refined indium from indium tin oxide waste materials". It dissolves indium tin oxide in an acid solution. During the indium tin separation process, hydrogen peroxide is added to oxidize Sn 2+ to Sn 4+ , and then an inorganic coprecipitant (magnesium sulfate) is added to form a dense precipitate to remove tin, and the tin removal rate is greater than 99%. (2) Patent document CN101701292A discloses a method for "recovering indium and tin from ITO waste targets by an oxidation method". Utilizing the fact that tin has two states, divalent and tetravalent, in solution, and the precipitation pH difference between tetravalent tin and trivalent indium ions in solution is relatively large. By controlling a certain pH value and using hydrogen peroxide for secondary oxidation to oxidize tin ions to tetravalent to generate hydrolysis precipitation, while indium remains in the aqueous solution, thus realizing the complete separation of indium and tin. The tin content in the separated solution is less than 2 ppm. (3) Patent document CN1487102A discloses a method for "recovering indium from indium tin oxide waste targets". It includes steps such as leaching, impurity removal, replacement, and electrolysis. Impurity removal is carried out at 25 - 60K under the condition of using sponge indium or indium flakes as a purification agent. The tin content in the solution after impurity removal is <0.1 g / L. (4) Patent document CN10163425A discloses "a method for extracting and separating indium and tin from an indium tin mixed solution". In an acidic solution system containing indium and tin, P 204Extract indium and tin simultaneously, and then use 0.5 - 3 mol / L fluoride (HF, NaF, NH₄F) to complex and strip tin. After acid washing the stripping residue liquid, use 4 - 6 mol / L hydrochloric acid to strip indium. Obtain a high-purity indium solution and a high-purity tin solution, realizing the complete separation of indium and tin. (5) Patent document CN101528988A discloses a method for "recovering valuable metals from ITO waste", which electrolyzes the ITO waste as the anode to recover indium. The electrolytic cell is separated by a diaphragm or an anion exchange membrane between the anode and the cathode. Then, the anode electrolyte is pumped out to remove tin, and the purified post-liquid is filled into the cathode side for electrolysis, thereby enabling the selective recovery of metallic indium. For the method of removing tin, methods such as neutralization method, displacement method, metastannic acid method, hydrolysis method, etc. can be used, and there will be a small amount of tin residue in the anode electrolyte. (6) Patent document CN101104883A discloses a method for "recovering indium and tin from ITO waste by acid leaching - sulfide precipitation combined process", which adds sodium sulfide to the indium and tin leaching solution to precipitate tin as sulfide and remove it from the solution. (7) Patent document CN101660056 "Method for separating indium and tin by vacuum distillation of indium-tin alloy" and CN201567361U "Production device for continuously removing tin from crude indium" respectively disclose a method and a device for separating indium and tin by vacuum distillation method. (8) Patent document CN103194625A discloses "a method for separating tin-indium alloy", which under the condition of 850 - 1250K, sprays industrial oxygen with a purity of 93 - 98.5% onto the surface of the tin-indium alloy to oxidize all tin and indium into oxides, then leach with 80 - 100 g / L acid, filter, the obtained filter residue is reduced and smelted to produce crude tin, and the filtrate is subjected to conventional extraction, stripping, and displacement to obtain crude indium, realizing the separation of tin and indium. (9) Patent document CN1757768A discloses "a method for separating indium-tin mixture", which separates indium and tin by leaching and two-stage displacement method. First, add zinc powder to the acid solution of the indium-tin mixture to displace tin ions into solid tin, and perform solid-liquid separation to achieve the separation of tin and indium. The tin slag is soaked with concentrated nitric acid for impurity removal and then reduced and smelted with coke powder to obtain crude tin; the solution after removing tin by zinc sheet displacement is used to obtain sponge indium, which is pelletized - melted into crude indium. (10) Patent document CN101701291A discloses a method for "recovering indium and tin from ITO waste target by distillation method", which utilizes the fact that the boiling point of SnCl₄ is relatively low under normal pressure and there is a certain interval between the sublimation temperature of InCl₃ under normal pressure, and separates the chloride salts of indium and tin by distillation. The ITO waste target is leached with hydrochloric acid, and after leaching, an appropriate amount of oxidant is added to oxidize Sn 2+ to Sn 4+ , distill at 120 - 140K for 3 - 9h, collect the distillate and the residue respectively, dissolve the residue with dilute hydrochloric acid, displace with aluminum plate, and perform alkali fusion to obtain crude indium.

[0005] The wet recycling process of ITO waste targets is as follows: First, the ITO targets are pretreated, then leached, and the leachate is processed to separate indium and tin. Indium is extracted and refined, and finally pure indium is obtained. The key to wet recycling lies in the separation of indium and tin in the solution. Separation methods include metal displacement method, solvent extraction method, sulfide precipitation method, neutralization method, etc. Han Qiying et al. recovered indium from ITO waste targets by acid dissolution, displacement, and alkali fusion. Liu Zhihong et al. separated indium and tin by sulfide precipitation using the different solubility products of In2S3 and SnS. Sheng-Jen Hsieh recovered indium from waste ITO targets by wet and hot-dip methods. Li Yanhui et al. recovered indium from ITO waste targets by acid leaching, secondary displacement, and alkali fusion operations. Jung-Chul adopted a new method of hydrothermal reaction in an alkaline solution to remove tin and enrich indium metal from ITO target waste. Gu et al. proposed a process of distillation crystallization for separating indium and tin by chlorination method. Wen Zhipeng et al. proposed a process of strengthening the leaching of ITO waste targets by microwave pretreatment.

[0006] The pyrometallurgical recycling process of ITO waste targets mainly includes two steps: reduction of oxides and separation of indium and tin. Chen Jian et al. adopted hydrogen reduction - secondary molten salt electrolysis; Xu et al. directly reduced ITO waste targets with H2; He Yunxia et al. recovered indium from ITO waste targets by vacuum carbothermal reduction method; Deng Yong et al. adopted a carbothermal reduction - vacuum distillation method to recover metallic indium from ITO waste targets; Itoh et al. directly reduced ITO waste targets using a CO - CO2 mixed gas as a reducing agent; Ma En et al. recovered indium from ITO waste targets by a crude vacuum chlorination separation method; Wang Ruixue et al. prepared indium tin by in-situ pyrolytic reduction of waste liquid crystal panels (LCDs); Wang Hongyu et al. directly recovered metallic indium and metallic tin from ITO waste targets by a one-step vacuum carbothermal reduction method.

[0007] For other recycling processes of ITO waste targets, Ogi et al. developed a biosorption system for recovering indium using bacterial algae; Higashi et al. recovered indium in ITO using microorganisms (Shewanella). Wang Yuanyuan et al. recovered indium from ITO waste targets by molten salt electrolysis; Su Xianwei et al. explored a method of using s-ITO (waste targets) to replace the graphite anode and directly electrolyzing s-ITO in CaO - CaCl2 molten salt.

[0008] The key to the recycling process of ITO waste targets lies in the separation of indium and tin. The methods recorded in the above existing technologies mainly adopt wet methods, vacuum distillation methods or sulfide precipitation methods. These methods have technical problems such as long process flow, incomplete separation of indium and tin, and introduction of new impurities during the reduction process.

[0009] Therefore, it is necessary to study a method for separating indium oxide and tin oxide from indium tin oxide waste targets by vacuum method to solve the above technical problems. Summary of the Invention

[0010] The object of the present invention is to provide a method for separating indium oxide and tin oxide from indium tin oxide waste targets by a vacuum method. This method is based on the fact that indium oxide can form volatile lower-valent oxides (In2O) when heated in an indium melt, and the generated lower-valent oxides can volatilize to the condensation region for condensation, thereby realizing the separation of indium oxide and tin oxide.

[0011] To achieve the above object, the present invention provides a method for separating indium oxide and tin oxide from indium tin oxide waste targets by a vacuum method, including the following steps:

[0012] (1) Take indium tin oxide waste target raw materials, add indium to the indium tin oxide waste target raw materials, and then heat and keep warm under vacuum conditions;

[0013] (2) The lower-valent oxides of indium volatilize into the volatiles to obtain indium oxide; tin oxide remains in the condensate to obtain tin oxide.

[0014] Further, in step (1), the molar ratio of indium oxide to indium in the indium tin oxide waste target raw materials is 1:1 to 4.

[0015] Further, in step (1), the pressure under the vacuum conditions is 5 to 20 Pa.

[0016] Further, in step (1), the heating temperature is 1050 to 1250 K.

[0017] Further, in step (1), the heat preservation time is 30 to 60 min.

[0018] 1. The separation method of the present invention can separate indium oxide and tin oxide in indium tin oxide waste target materials without introducing other impurities.

[0019] 2. Due to the fact that indium oxide can form volatile lower-valent oxides (In2O) when heated in an indium melt, and the generated lower-valent oxides can volatilize to the condensation region for condensation, the separation method of the present invention realizes the separation of indium oxide and tin oxide in indium tin oxide waste target materials, and realizes the resource recycling of indium tin oxide waste target materials. Detailed Embodiments

[0020] The following details the embodiments of the present invention, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The following described embodiments are exemplary and are intended to explain the present invention and should not be construed as a limitation to the present invention. In the description of the present invention, "a plurality" means two or more unless otherwise specifically defined. Example 1

[0021] The method for separating indium tin oxide by a vacuum method is as follows:

[0022] Weigh indium tin oxide waste target material (ITO target) and indium according to the molar ratio of indium oxide to indium in the indium tin oxide waste target material being 1:1, and put them into a graphite crucible; then put the graphite crucible into a vacuum furnace. The pressure in the vacuum furnace is 5 Pa, heat it up to 1073 K, and keep it warm for 60 min. After the heat preservation ends, open the vacuum furnace and take out the distillate and residue respectively. The metallic indium forms low-valent oxides of indium and volatilizes into the volatile matter, and the tin oxide in the ITO target remains in the condensate, realizing the separation of indium oxide and tin oxide in the ITO target. Example 2

[0023] The method for separating indium tin oxide by the vacuum method is as follows:

[0024] Weigh indium tin oxide waste target material (ITO target) and indium according to the molar ratio of indium oxide to indium in the indium tin oxide waste target material being 1:4, and put them into a graphite crucible; then put the graphite crucible into a vacuum furnace. The pressure in the vacuum furnace is 10 Pa, heat it up to 1223 K, and keep it warm for 30 min. After the heat preservation ends, open the vacuum furnace and take out the distillate and residue respectively. The metallic indium forms low-valent oxides of indium and volatilizes into the volatile matter, and the tin oxide in the ITO target remains in the condensate, realizing the separation of indium oxide and tin oxide in the ITO target. Example 3

[0025] The method for separating indium tin oxide by the vacuum method is as follows:

[0026] Weigh indium tin oxide waste target material (ITO target) and indium according to the molar ratio of indium oxide to indium in the indium tin oxide waste target material being 1:2, and put them into a graphite crucible; then put the graphite crucible into a vacuum furnace. The pressure in the vacuum furnace is 20 Pa, heat it up to 1173 K, and keep it warm for 60 min. After the heat preservation ends, open the vacuum furnace and take out the distillate and residue respectively. The metallic indium forms low-valent oxides of indium and volatilizes into the volatile matter, and the tin oxide in the ITO target remains in the condensate, realizing the separation of indium oxide and tin oxide in the ITO target. Example 4

[0027] The method for separating indium tin oxide by the vacuum method is as follows:

[0028] Weigh indium tin oxide waste target material (ITO target) and indium according to the molar ratio of indium oxide to indium in the indium tin oxide waste target material being 1:1, and put them into a graphite crucible; then put the graphite crucible into a vacuum furnace. The pressure in the vacuum furnace is 10 Pa, heat it up to 1050 K, and keep it warm for 40 min. After the heat preservation ends, open the vacuum furnace and take out the distillate and residue respectively. The metallic indium forms low-valent oxides of indium and volatilizes into the volatile matter, and the tin oxide in the ITO target remains in the condensate, realizing the separation of indium oxide and tin oxide in the ITO target. Example 5

[0029] A method for separating indium tin oxide by vacuum method comprises the following steps:

[0030] Weigh indium tin oxide waste target raw material (ITO target) and indium according to the molar ratio of indium oxide to indium in the indium tin oxide waste target raw material being 1:3, and put them into a graphite crucible; then put the graphite crucible into a vacuum furnace. The pressure in the vacuum furnace is 10 Pa, heat it up to 1250 K, and keep it warm for 50 min. After the heat preservation is over, open the vacuum furnace and take out the distillate and residue respectively. The metallic indium forms low-valent oxides of indium and volatilizes into the volatile matter, and the tin oxide in the ITO target remains in the condensate, realizing the separation of indium oxide and tin oxide in the ITO target.

[0031] In summary, the preparation method of the present invention is based on the fact that indium oxide can generate volatile low-valent oxides (In2O) when heated in indium melt, and the generated low-valent oxides can volatilize to the condensation area and condense, thereby realizing the separation of indium oxide and tin oxide; this separation method can separate indium oxide and tin oxide in the indium tin oxide waste target material without introducing other impurities, and realizes the resource recycling of the indium tin oxide waste target material.

[0032] What is disclosed above is only some embodiments of the present invention, and the scope of rights of the present invention cannot be limited thereby. Those of ordinary skill in the art can understand all or part of the processes of implementing the above embodiments, and the equivalent changes made according to the claims of the present invention still fall within the scope covered by the invention.

Claims

1. A method for separating indium oxide and tin oxide from indium tin oxide waste targets by a vacuum method, characterized in that: It includes the following steps: (1) Take the indium tin oxide waste target raw material, add indium to the indium tin oxide waste target raw material, and then heat and keep warm under vacuum conditions; (2) After the heat preservation ends, the low-valent oxide of indium volatilizes into the volatile matter to obtain indium oxide; tin oxide remains in the condensate to obtain tin oxide; In step (1), the heating temperature is 1050 - 1250K.

2. The method for separating indium oxide and tin oxide from indium tin oxide waste targets by the vacuum method according to claim 1, characterized in that, In step (1), the molar ratio of indium oxide to indium in the indium tin oxide waste target raw material is 1:1 - 4.

3. The method for separating indium oxide and tin oxide from indium tin oxide waste targets by the vacuum method according to claim 1, characterized in that, In step (1), the pressure of the vacuum condition is 5 - 20Pa.

4. The method for separating indium oxide and tin oxide from indium tin oxide waste targets by the vacuum method according to claim 1, characterized in that, In step (1), the heat preservation time is 30 - 60min.