A method for preparing InP from ITO waste

Abstract

The present invention discloses a method for preparing InP from ITO waste, belonging to the technical field of resource recycling of ITO waste. The ITO waste is crushed and then indium and tin are leached with sulfuric acid to obtain an indium-tin leaching solution; phosphoric acid is added to the indium-tin leaching solution for selective precipitation to obtain indium phosphate precipitate; the indium phosphate precipitate is subjected to reduction roasting to obtain a crude InP product; and the crude InP product is leached with sulfuric acid for impurity removal to obtain an InP product. This method adopts the combined process technology of wet extraction and pyrometallurgy, can use ITO waste as a direct raw material, and synthesize high-quality InP materials through a low-energy-consuming and simple process path, realizing the resource utilization of ITO waste and reducing the production cost of InP.

Description

Technical Field

[0001] The present invention relates to a method for recycling ITO waste, in particular to a method for preparing InP from ITO waste, and belongs to the technical field of ITO waste resource utilization. Background Art

[0002] ITO waste is a high-risk solid waste generated in the manufacturing process of the optoelectronic display industry, which is generated in the processing, use and recycling links of indium tin oxide (ITO) targets. Waste targets are the leftover scraps or defective products remaining after the ITO targets are sputtered by magnetron for coating. With the rapid development of the global display panel, touch screen and photovoltaic industries, the demand for ITO targets has increased sharply, and the output of waste targets has also risen accordingly. However, the existing technologies for recycling waste targets have high technical thresholds and high treatment costs, and their comprehensive recovery rates are very low. A large amount of waste targets are sealed or landfilled for a long time, resulting in increasingly serious problems of resource waste and environmental pollution. The indium content in ITO waste can reach 80% - 90%, which is much higher than that of primary indium ore. The indium value per ton of ITO waste is as high as one million yuan, and it has extremely high recycling economic value.

[0003] In the field of semiconductor materials, indium phosphide (InP) has become the core material for high-frequency devices due to its excellent electron mobility and optoelectronic properties. However, the traditional high-temperature synthesis method has high raw material costs and high energy consumption, which seriously restricts the development of the industry. For example, Chinese Patent (Publication No. CN111472047B) discloses an indium phosphide crystal and its growth method. In this method, indium blocks and phosphorus grains are placed in an atmospheric pressure polycrystalline synthesis furnace. First, the temperature is raised to melt the indium. After the phosphorus grains are completely absorbed by the melted indium, the temperature is gradually raised to 1030 - 1100 °C to obtain indium phosphide polycrystals.

[0004] Based on the technical defects existing in the existing InP preparation process, if the by-product ITO waste in the flat panel display industry can be resourcefully utilized and high-value-added InP materials can be prepared through a simple metallurgical process, the production cost of indium phosphide will be greatly reduced, and it will have broad application prospects. Summary of the Invention

[0005] Aiming at the technical problems existing in the existing ITO waste resource utilization and InP preparation processes, the purpose of the present invention is to provide a method for preparing InP from ITO waste. This method uses a combined process technology of wet extraction and pyrometallurgy, which can use ITO waste as the direct raw material, synthesize high-quality InP materials through a low-energy-consuming and simple process path, realize the resource utilization of ITO waste, and reduce the production cost of InP.

[0006] To achieve the above technical objectives, the present invention provides a method for preparing InP from ITO waste. The method involves crushing the ITO waste and then leaching indium and tin with sulfuric acid to obtain an indium-tin leaching solution; adding phosphoric acid to the indium-tin leaching solution for selective precipitation to obtain indium phosphate precipitate; subjecting the indium phosphate precipitate to reduction roasting to obtain a crude InP product; and subjecting the crude InP product to sulfuric acid leaching for impurity removal to obtain an InP product.

[0007] The key to the technical solution of the present invention lies in: firstly, selectively extracting tin and indium, and making full use of the solubility difference between indium tin oxide and impurity components in sulfuric acid to achieve the selective extraction of indium and tin and preliminarily remove most impurities; secondly, separating tin and indium through phosphorylation, and making full use of the difference in solubility products of indium phosphate and tin phosphate to achieve the separation of indium and tin; thirdly, reducing and converting indium phosphate to obtain indium phosphide at low temperature, and using a weakly reducing atmosphere to directionally reduce indium phosphate to InP; finally, using sulfuric acid leaching for deep impurity removal, and relying on the solubility difference between indium phosphate and InP in sulfuric acid at high temperature to achieve the purification of the InP product, and ultimately obtain an InP product with a purity of over 99.9%.

[0008] As a preferred embodiment, the particle size of the crushed ITO waste satisfies that the mass ratio of particles smaller than 0.074 mm is greater than 80%. The ITO waste in the present invention is the waste generated during the ITO sputtering production process. Crushing the ITO waste to a sufficiently fine size can enable full monomer dissociation of each phase in the ITO waste and ensure good subsequent leaching and impurity removal effects.

[0009] As a preferred embodiment, the conditions for leaching indium and tin with sulfuric acid are as follows: the concentration of H2SO4 is 80 - 120 g / L, the liquid-solid ratio is 9 - 11 mL / g, the leaching time is 2 - 3 hours, and the leaching temperature is 80 - 120 °C. During the process of leaching indium and tin with sulfuric acid, the leaching efficiency and selectivity of indium and tin are mainly affected by the concentration of H2SO4 and temperature. For example, the lower the concentration of H2SO4 and the lower the leaching temperature, the lower the leaching efficiency of indium and tin. While the higher the concentration of H2SO4 and the higher the leaching temperature, although the leaching efficiency of indium and tin is higher, the leaching rate of other impurities will also increase. The liquid-solid ratio of the leaching solution and the leaching time are secondary factors affecting the leaching efficiency and selectivity of indium and tin. For example, when other conditions are constant, the effect on the leaching rate is very small when the liquid-solid ratio is greater than 9 mL / g, and too high a liquid-solid ratio leads to difficulties in subsequent precipitation and waste of acid solution. After optimizing other conditions, an indium leaching rate of over 99% can be achieved after leaching for more than 2 hours. When the temperature or the concentration of H2SO4 is low, the leaching time needs to be appropriately extended.

[0010] As a preferred embodiment, during the selective precipitation process, phosphoric acid is added and the pH is controlled within the range of 6.2 to 6.5. A pH within the range of 6.2 to 6.5 belongs to the optimal precipitation pH range of indium phosphate to reduce the impurity content in indium phosphate.

[0011] As a preferred embodiment, the conditions for the reduction roasting are as follows: in an atmosphere containing hydrogen, at a temperature of 550 to 700 °C, roasting for 45 to 90 minutes. The temperature of the reduction roasting depends on the temperature at which indium phosphate is reduced by hydrogen. When the temperature is too low, the reaction is difficult to occur or the rate is very low even if it occurs. After exceeding the temperature limit, higher temperatures do not bring a significant increase in the reaction rate but will instead consume a large amount of energy additionally.

[0012] As a preferred embodiment, the hydrogen-containing atmosphere includes a mixed gas of H2 and H2O, and the volume ratio H2 / H2O is 4 to 20. The partial pressure of H2 in the hydrogen-containing atmosphere needs to be controlled within an appropriate range. When the partial pressure of H2 is low, the Gibbs free energy of the reduction reaction is still relatively high and the reaction rate is low. When the partial pressure of H2 is high, too high a partial pressure of the reducing gas is likely to cause indium phosphate to be over-reduced to metallic indium. The hydrogen-containing atmosphere is maintained by continuously introducing a mixed gas of H2 and H2O. The flow rate of the mixed gas of H2 and H2O is 0.05 to 0.1 L / min (relative to each gram of indium phosphate raw material). If the gas flow rate is too small, it will lead to insufficient supply of the reducing gas. After the flow rate exceeds a certain limit, it will no longer have a positive impact on the reaction and will cause waste of resources.

[0013] As a preferred embodiment, the conditions for the sulfuric acid leaching for impurity removal are as follows: the concentration of H2SO4 is 80 to 120 g / L, the temperature is 120 to 150 °C, and the leaching time is 6 to 9 hours. Under the preferred conditions, the difference in solubility between indium phosphate and InP in sulfuric acid can be utilized to remove a small amount of incompletely converted indium phosphate in the InP product, and finally obtain an InP product with a purity of more than 99.9%. At an appropriate sulfuric acid concentration, increasing the temperature can increase the solubility of indium phosphate, while indium phosphide is not affected. Therefore, the difference in solubility between the two is utilized to separate them.

[0014] Compared with the prior art, the beneficial technical effects brought by the technical solution of the present invention are as follows:

[0015] 1) The present invention proposes a method for preparing InP materials from ITO waste, adopting a technical means combining hydrometallurgy and pyrometallurgy, enabling the ITO waste to achieve resource recovery and utilization of solid waste, and at the same time obtaining high-quality InP materials, providing a new path for the comprehensive utilization of ITO waste and the production of InP, and solving the technical problems such as the difficult recovery of current ITO waste and the high production cost of indium phosphide.

[0016] 2) The present invention can be produced using existing large-scale industrial mature equipment such as rotary kilns and reduction shaft furnaces. The technical route is simple, greatly improving production efficiency and resource utilization rate. The solutions and gases used are common and frequently used in industrial production processes, which is conducive to achieving large-scale and industrialization.

[0017] 3) In the process of preparing InP materials from ITO waste, the present invention makes full use of the solubility difference between indium tin oxide and impurity components in sulfuric acid to achieve selective extraction of indium and tin, and then realizes the separation of indium and tin through the solubility product difference between indium phosphate and tin phosphate. Then, using a weak reducing atmosphere of H2, indium phosphate is directionally reduced to InP. Finally, relying on the solubility difference between indium phosphate and InP in sulfuric acid at high temperature, product purification is achieved. While recovering ITO waste resources, an InP product with higher added value is obtained. Specific Embodiments

[0018] The following examples are intended to further illustrate the content of the present invention rather than limit the protection scope of the claims of the present invention.

[0019] Comparative Example 1

[0020] This comparative example is used to illustrate that if the crushing fineness of the raw material is insufficient, it is not conducive to leaching and reduction.

[0021] Compared with Example 1, the only difference is that the ITO waste is finely crushed to a proportion of 30% with a particle size of -0.074 mm.

[0022] The performance of the obtained product was detected: the purity of InP was only 97.2%, and the indium recovery rate was only 56.8%.

[0023] Comparative Example 2

[0024] This comparative example is used to illustrate that if the leaching acidity is too low, it is not conducive to leaching and impurity removal.

[0025] Compared with Example 1, the only difference is that the ITO waste finely crushed to a proportion of 80% with a particle size of -0.074 mm is leached with 50 g / L of H2SO4, the liquid-solid ratio is 11 mL / g, the leaching time is 2 hours, and the leaching temperature is 120°C.

[0026] The performance of the obtained product was detected: the purity of InP was only 97.8%, and the indium recovery rate was only 47.2%.

[0027] Comparative Example 3

[0028] This comparative example is used to illustrate that if the leaching temperature is low, it is not conducive to leaching and impurity removal.

[0029] Compared with Example 2, the only difference is that ITO waste with 90% of the particles being finer than -0.074 mm is leached with 120 g / L of H2SO4 at a liquid-to-solid ratio of 9 mL / g for 3 hours at a leaching temperature of 60 °C.

[0030] The performance of the obtained product was tested: the purity of InP was only 96.7%, and the indium recovery rate was only 42.9%.

[0031] Comparative Example 4

[0032] This comparative example is used to illustrate that if the pH is too low during phosphoric acid precipitation, it is difficult to form indium phosphate precipitation.

[0033] Compared with Example 2, the only difference is that a precipitate is obtained after adding phosphoric acid to the obtained leaching solution and adjusting the pH to 4.0.

[0034] The performance of the obtained product was tested: the purity of InP was 99.9%, and the indium recovery rate was only 8.9%.

[0035] Comparative Example 5

[0036] This comparative example is used to illustrate that if the hydrogen concentration is insufficient, it is not conducive to the reduction of indium phosphate to indium phosphide.

[0037] Compared with Example 3, the only difference is that the precipitate is subjected to reduction roasting with a H2 / H2O volume ratio of 2 and a flow rate of 0.1 L·min

[0041] ,

[0036] ,

[0040] ,

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[0044] ,

[0039] ,

[0043] ,

[0038] ,

[0042] ,

[0037] , , , , -1 , ,

[0045] , , , , , , per gram of raw material, the roasting temperature is 550 °C, and the holding time is 90 minutes.

[0038] The performance of the obtained product was tested: the purity of InP was only 78.2%, and the indium recovery rate was 46.8%.

[0039] Comparative Example 6

[0040] This comparative example is used to illustrate that if the roasting temperature is low, it is not conducive to the reduction of indium phosphate to indium phosphide.

[0041] Compared with Example 3, the only difference is that the precipitate is subjected to reduction roasting with a H2 / H2O volume ratio of 4 and a flow rate of 0.1 L·min -1 per gram of raw material, the roasting temperature is 400 °C, and the holding time is 90 minutes.

[0042] The performance of the obtained product was tested: the purity of InP was only 72.7%, and the indium recovery rate was 33.5%.

[0043] Comparative Example 7

[0044] This comparative example is used to illustrate that if the temperature is too low during high-temperature leaching for impurity removal, it is difficult to remove indium phosphate impurities.

[0045] Compared with Example 4, the only difference is that: the calcined product is further leached with 80 g / L of H2SO4 at 100 °C for 9 hours, and the high-temperature leaching residue is the InP precursor material.

[0046] Performance testing was carried out on the obtained product: the purity of InP was only 87.9%, and the indium recovery rate was only 56.8%.

[0047] Example 1

[0048] Using the ITO waste from a certain factory (the indium-tin ratio In2O3 / SnO2 = 9, the Al2O3 content is 0.4%, the TiO2 content is 0.3%, and it also contains trace impurities such as Fe, Zr, W, and Cu), sulfuric acid, phosphoric acid, and hydrogen as raw materials. First, the ITO waste crushed to -0.074 mm with a proportion of 80% is leached with 80 g / L of H2SO4, the liquid-solid ratio is 11 mL / g, the leaching time is 2 hours, and the leaching temperature is 120 °C; phosphoric acid is added to the obtained leaching solution and the pH is adjusted to 6.2 to obtain a precipitate, and the precipitate is subjected to reduction roasting, the H2 / H2O volume ratio is 4, and the flow rate is 0.05 L·min -1 For every gram of raw material, the roasting temperature is 550 °C and the heat preservation time is 90 minutes; the roasted product is further leached with 80 g / L of H2SO4 at 120 °C for 9 hours, and the high-temperature leaching residue is the high-quality InP precursor material.

[0049] Performance testing was carried out on the obtained product: the purity of InP was 99.9%, and the indium recovery rate was 90.8%.

[0050] Example 2

[0051] Using the ITO waste from a certain factory (the indium-tin ratio In2O3 / SnO2 = 9, the Al2O3 content is 0.4%, the TiO2 content is 0.3%, and it also contains trace impurities such as Fe, Zr, W, and Cu), sulfuric acid, phosphoric acid, and hydrogen as raw materials. First, the ITO waste crushed to -0.074 mm with a proportion of 90% is leached with 120 g / L of H2SO4, the liquid-solid ratio is 9 mL / g, the leaching time is 3 hours, and the leaching temperature is 120 °C; phosphoric acid is added to the obtained leaching solution and the pH is adjusted to 6.2 to obtain a precipitate, and the precipitate is subjected to reduction roasting, the H2 / H2O volume ratio is 4, and the flow rate is 0.05 L·min -1 For every gram of raw material, the roasting temperature is 550 °C and the heat preservation time is 90 minutes; the roasted product is further leached with 80 g / L of H2SO4 at 120 °C for 9 hours, and the high-temperature leaching residue is the high-quality InP precursor material.

[0052] Performance testing was carried out on the obtained product: the purity of InP was 99.9%, and the indium recovery rate was 91.2%.

[0053] Example 3

[0054] Using the ITO waste from a certain factory (In2O3 / SnO2 indium-tin ratio = 9, Al2O3 content 0.4%, TiO2 content 0.3%, and containing trace impurities such as Fe, Zr, W, Cu, etc.), sulfuric acid, phosphoric acid, and hydrogen as raw materials, first leach the ITO waste with a particle size of -0.074 mm accounting for 80% using 80 g / L of H2SO4, with a liquid-solid ratio of 11 mL / g, a leaching time of 2 hours, and a leaching temperature of 80 °C; add phosphoric acid to the obtained leachate and adjust the pH to 6.5 to obtain a precipitate, and perform reduction roasting on the precipitate, with a H2 / H2O volume ratio of 4 and a flow rate of 0.1 L·min -1 Per gram of raw material, the roasting temperature is 550 °C, and keep warm for 90 minutes; the roasted product is then leached with 80 g / L of H2SO4 at 120 °C for 9 hours, and the high-temperature leaching residue is the high-quality InP precursor material.

[0055] Perform performance testing on the obtained product: InP purity is 99.9%, and indium recovery rate is 92.1%

[0056] Example 4

[0057] Using the ITO waste from a certain factory (In2O3 / SnO2 indium-tin ratio = 9, Al2O3 content 0.4%, TiO2 content 0.3%, and containing trace impurities such as Fe, Zr, W, Cu, etc.), sulfuric acid, phosphoric acid, and hydrogen as raw materials, first leach the ITO waste with a particle size of -0.074 mm accounting for 80% using 80 g / L of H2SO4, with a liquid-solid ratio of 11 mL / g, a leaching time of 2 hours, and a leaching temperature of 120 °C; add phosphoric acid to the obtained leachate and adjust the pH to 6.2 to obtain a precipitate, and perform reduction roasting on the precipitate, with a H2 / H2O volume ratio of 20 and a flow rate of 0.05 L·min -1 Per gram of raw material, the roasting temperature is 700 °C, and keep warm for 45 minutes; the roasted product is then leached with 80 g / L of H2SO4 at 120 °C for 9 hours, and the high-temperature leaching residue is the high-quality InP precursor material.

[0058] Perform performance testing on the obtained product: InP purity is 99.9%, and indium recovery rate is 90.2%.

[0059] Example 5

[0060] Using the ITO waste from a certain factory (the indium-tin ratio In2O3 / SnO2 = 9, the Al2O3 content is 0.4%, the TiO2 content is 0.3%, and it also contains trace impurities such as Fe, Zr, W, and Cu), sulfuric acid, phosphoric acid, and hydrogen as raw materials. First, the ITO waste that has been crushed to -0.074 mm with a proportion of 80% is leached with 80 g / L of H2SO4, the liquid-solid ratio is 11 mL / g, the leaching time is 2 hours, and the leaching temperature is 120 °C; phosphoric acid is added to the obtained leaching solution and the pH is adjusted to 6.2 to obtain a precipitate, and the precipitate is subjected to reduction roasting, the H2 / H2O volume ratio is 4, and the flow rate is 0.05 L·min -1 per gram of raw material, the roasting temperature is 550 °C, and the heat preservation time is 90 minutes; the roasted product is then leached with 120 g / L of H2SO4 at 150 °C for 6 hours, and the high-temperature leaching residue is a high-quality InP precursor material.

[0061] Perform performance testing on the obtained product: the purity of InP is 99.9%, and the indium recovery rate is 91.5%.

Claims

1. A method for preparing InP from ITO waste, characterized in that: The ITO waste is crushed and then indium and tin are leached with sulfuric acid to obtain an indium-tin leaching solution; phosphoric acid is added to the indium-tin leaching solution for selective precipitation to obtain indium phosphate precipitate; the indium phosphate precipitate is subjected to reduction roasting to obtain a crude InP product; the crude InP product is leached with sulfuric acid for impurity removal to obtain an InP product; The conditions for leaching indium and tin with sulfuric acid are as follows: the concentration of H2SO4 is 80-120 g / L, the liquid-solid ratio is 9-11 mL / g, the leaching time is 2-3 hours, and the leaching temperature is 80-120 °C; During the selective precipitation process, phosphoric acid is added and the pH is controlled within the range of 6.2-6.5; The conditions for leaching with sulfuric acid for impurity removal are as follows: the concentration of H2SO4 is 80-120 g / L, the temperature is 120-150 °C, and the leaching time is 6-9 hours.

2. The method for preparing InP from ITO waste according to claim 1, characterized in that: The particle size of the crushed ITO waste meets the requirement that the mass ratio of particles smaller than 0.074 mm is greater than 80%.

3. A method for preparing InP from ITO waste according to claim 1, characterized in that: The conditions for reduction roasting are as follows: in an atmosphere containing hydrogen, at a temperature of 550-700 °C, roasting for 45-90 min.

4. The method for preparing InP from ITO waste according to claim 3, characterized in that: The atmosphere containing hydrogen includes a mixed gas of H2 and H2O, and the volume ratio of H2 / H2O is 4-20.