Scandium-zirconium powder as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of solid oxide fuel cells, and particularly relates to scandium-zirconium powder as well as a preparation method and application thereof. According to the preparation method of the scandium-zirconium powder provided by the invention, the scandium-zirconium mixed solution and the carbon source react in the spray drying process to generate the granulated spherical powder of the amorphous scandium-zirconium precursor and the carbon source, and the carbon source is uniformly distributed in the granulated balls, so that the effect of inhibiting agglomeration of the scandium-zirconium precursor is achieved; the prepared scandium-zirconium powder is narrow in particle size distribution range, and good control over the particle size is achieved. In addition, the preparation method of the scandium-zirconium powder is mild in reaction condition and low in equipment requirement, and energy consumption and cost are reduced.

Description

Technical Field

[0001] The present application belongs to the field of solid oxide fuel cell technology, and in particular relates to a scandium-zirconium powder and a preparation method and application thereof. Background Art

[0002] Carbon-containing compounds such as coal, oil, and natural gas are collectively referred to as carbon-based fuels and are a major energy resource. Currently, the primary power generation efficiency of carbon-based fuels is only around 30%, resulting in significant pollution and greenhouse gas emissions. Fuel cells are electrochemical power generation devices that directly convert the chemical energy of fuel into electrical energy. Due to their high efficiency and low pollution, they have become a focus of intense development and competition. Among them, solid oxide fuel cells (SOFCs) are the most effective way to efficiently and cleanly utilize carbon-based fuels, with a primary power generation efficiency of 50-60%. They are a new, leading industry that is knowledge- and technology-intensive, consumes minimal material resources, has great growth potential, and offers excellent overall benefits.

[0003] In a single cell, poor thermal compatibility between the sintering properties of electrode and electrolyte materials, unstable electrolyte conductivity, and structural damage caused by weak cell strength can all lead to degradation of the overall stack performance. Therefore, intensified research on electrolyte materials is key to the commercial development of SOFCs. Currently, the vast majority of commercial SOFCs use 6-10 mol% yttria-stabilized zirconia (YSZ) as a solid electrolyte. However, traditional SOFCs using YSZ as an electrolyte suffer from high operating temperatures, adverse interfacial reactions between cell materials, low conductivity, and difficulty in sealing, all of which hinder the commercial development of SOFCs. Therefore, enhancing SOFC conductivity has become an inevitable trend in the commercial development of SOFCs. Scandium oxide stabilized zirconia (ScSZ) has been developed into a new electrolyte material for SOFC due to its excellent oxygen ion conductivity. The small particle size and concentrated particle size distribution of ScSZ powder will help reduce the sintering temperature of subsequent films, thereby improving the sintering activity and achieving higher conductivity. However, due to the easy agglomeration of zirconia powder itself, the particle size D50 of the currently prepared ScSZ powder is usually greater than 0.25μm, and the wide particle size distribution seriously restricts its development.

[0004] In addition, the waste acid discharged by zirconium oxychloride production enterprises contains a large amount of scandium. The amount of waste liquid generated by producing one ton of zirconium oxychloride is about 0.2m3. 3 Sc content is about 500~1000g / m 3 , the content is high, and after discharge, it not only wastes resources but also pollutes the environment. Therefore, the reasonable recycling and reuse of waste acid can turn waste into treasure, which will be the most ideal treatment method. Summary of the Invention

[0005] The purpose of this application is to provide a scandium-zirconium powder and its preparation method and application, so as to obtain scandium-zirconium powder with smaller particle size and concentrated particle size distribution. Furthermore, scandium-zirconium powder in waste zirconium oxychloride acid can be recovered to achieve resource recycling.

[0006] To this end, this application provides the following technical solutions:

[0007] According to one aspect of the present application, a method for preparing scandium-zirconium powder is provided, comprising the following steps:

[0008] S1, preparing a scandium-zirconium mixed solution according to the composition of the target product, adding a carbon source, wherein the mass ratio of the carbon source to the cations in the scandium-zirconium mixed solution is 5:1-50, to obtain a carbon-containing scandium-zirconium solution; and then spray drying the carbon-containing scandium-zirconium solution to obtain a precursor powder;

[0009] S2, heat-treating the precursor powder to obtain scandium-zirconium powder; the heat treatment temperature is 700 to 1300° C., the heating rate is 200-1000° C. / s, and the holding time is 1-3600s.

[0010] In the present application, the chemical formula composition of the scandium-zirconium powder can be (Sc2O3) y (ZrO2) 1-y ; Among them, the value range of y is 0.05-0.12.

[0011] In some optional embodiments, in S1, preparing a scandium-zirconium mixed solution using zirconium oxychloride waste acid comprises the following steps:

[0012] S11, extracting the zirconium oxychloride waste acid using a scandium-zirconium synergistic extractant to obtain a scandium-zirconium extract;

[0013] S12, stripping the scandium-zirconium extract with a stripping agent to obtain a scandium-zirconium stripping solution, and regulating the ratio of the scandium-zirconium element in the scandium-zirconium stripping solution according to the composition of the target product to obtain a scandium-zirconium mixed solution;

[0014] Wherein, in S11, the scandium-zirconium synergistic extractant comprises compound A, compound B and sulfonated kerosene in a volume ratio of 10-20:20-35:45-65,

[0015] Wherein, the compound A includes at least one of diisooctyl phosphate (P204), di(2-ethylhexyl)phenyl phosphate (CAS: 16368-97-1), and bis(2,4,4-trimethylpentyl)phosphonic acid (cyanex272, CAS: 83411-71-6);

[0016] The compound B includes at least one of tributyl phosphate (TBP) and trialkylphosphine oxide (CAS: 31160-64-2, cyanex923);

[0017] In the present application, the waste zirconium oxychloride acid comes from the waste acid discharged by the zirconium oxychloride production enterprise, which contains elements such as zirconium, scandium, titanium, and iron.

[0018] In the present application, the proportion of the scandium zirconium element in the scandium zirconium strip solution can be controlled by adding zirconium oxychloride, scandium chloride, zirconium oxynitrate, scandium nitrate, etc. to the scandium zirconium strip solution.

[0019] In some optional embodiments, in S11, the scandium-zirconium synergistic extractant comprises compound A, compound B, synergistic extractant C, and sulfonated kerosene in a volume ratio of 10-20:20-35:10-15:45-65;

[0020] The synergist C includes at least one of 1-hexyl-3-methylimidazolium bistrifluoromethanesulfonyl imide salt (CAS: 916729-96-9), 1-butyl-3-methylimidazolium hexafluorophosphate (CAS: 174501-64-5), and N-butylpyridinium nitrate ([C4py][NO3]).

[0021] In some optional embodiments, in S11, the extraction temperature is 20-50°C, the extraction time is 10-120 min, and the extraction method used is 3-5 stage countercurrent extraction.

[0022] And / or, a washing and impurity removal step is further included after the extraction;

[0023] Optionally, the washing and impurity removal adopts a mixed aqueous solution of a reducing agent and an inorganic acid with a pH of 1-2, wherein the molar ratio of the reducing agent to the inorganic acid is 1:2-5, the washing and impurity removal adopts countercurrent washing, the washing stage number is 4-8 stages, and the washing temperature is 30-50°C;

[0024] Optionally, the reducing agent includes at least one of sodium sulfite, sodium metabisulfite, sodium thiosulfate and sodium dithionite.

[0025] In this application, the obtained scandium- and zirconium-containing extract is washed and impurity-removed to improve the purity of the product, providing a high-purity raw material for the next step of preparing scandium-zirconium powder. Specifically, by selecting a scandium-zirconium synergistic extractant with a specific composition, the high-valent titanium and iron in the waste acid easily undergo a complex reaction with the extractant. The reducing agent in the washing and impurity removal step then reduces the titanium and iron to a low-valent state, thereby achieving separation and impurity removal.

[0026] In some optional embodiments, in S12, the stripping agent is a 3-8 mol / L inorganic acid aqueous solution, the stripping temperature is 20-50° C., the stripping time is 10-120 min, and the stripping method is 5-8 stage countercurrent stripping;

[0027] Optionally, the inorganic acid in the inorganic acid aqueous solution includes at least one of hydrochloric acid, nitric acid and sulfuric acid.

[0028] In some optional embodiments, in S1, the cation concentration in the scandium-zirconium mixed solution is 0.1-4 mol / L;

[0029] and / or, the mass ratio of the carbon source to the cations in the scandium-zirconium mixed solution is 5:2-30;

[0030] and / or, the inlet temperature of the spray drying is 110-180° C.;

[0031] And / or, the carbon source includes at least one of citric acid, polyethylene glycol, polyvinyl alcohol, and polyvinyl pyrrolidone; wherein the molecular weight of polyethylene glycol is between 5000-20000, the molecular weight of polyvinyl alcohol is between 16000 and 20000, and the molecular weight of polyvinyl pyrrolidone is between 8000-50000.

[0032] In some optional embodiments, in S1, the amount ratio of the carbon source to the cations in the scandium-zirconium mixed solution is 5:3-15;

[0033] and / or, the inlet temperature of the spray drying is 110-150° C., optionally, the inlet temperature of the spray drying is 120-140° C.;

[0034] And / or, the cation concentration in the scandium-zirconium mixed solution is 0.5-1 mol / l.

[0035] In the present application, the spray temperature is conducive to carbonization of the carbon source but not easy to oxidize, which makes the carbon source evenly distributed in the granulation balls, and plays a role in inhibiting the agglomeration of the scandium-zirconium precursor. By limiting the cation concentration in the scandium-zirconium mixed solution, it is possible to achieve a balance between product particle size and production efficiency. When the cation concentration in the scandium-zirconium mixed solution is too high, the solution viscosity increases, making it difficult to atomize, and the atomized droplet size is large, the primary particle size of the granulation balls increases, and the final scandium-zirconium powder particle size increases; while if the cation concentration in the scandium-zirconium mixed solution is too low, the atomization efficiency is low and the output is low.

[0036] In some optional embodiments, in S2, the heating rate of the heat treatment is 500-1000°C / s, and the holding time is 10-600s; optionally, the heating rate is 500-800°C / s, and the holding time is 10-100s;

[0037] And / or, the heat treatment temperature is 900 to 1200°C, optionally, the heat treatment temperature is 1000 to 1100°C.

[0038] In some alternative embodiments, the heat treatment is performed in a Joule heating device.

[0039] The present application also provides a scandium-zirconium powder prepared by the above-mentioned preparation method.

[0040] The present application also provides an application of the scandium-zirconium powder in a solid oxide fuel cell. In the present application, the composition and preparation method of the solid oxide fuel cell are conventional in the field and are not specifically limited in the present application, and may include any technology disclosed in the prior art.

[0041] Preferably, the method for preparing scandium-zirconium powder provided in the present application may include the following steps:

[0042] Step 1) Scandium-zirconium synergistic extraction: extracting the zirconium oxychloride waste acid with a scandium-zirconium synergistic extractant to obtain a scandium-zirconium extract;

[0043] Step 2) stripping the scandium-zirconium extract with a stripping agent to obtain a scandium-zirconium stripping solution;

[0044] Step 3) adding a carbon source to the scandium-zirconium stripping solution, wherein the molar ratio of the carbon source to the cations of the scandium-zirconium mixed solution is 5:1-50, to obtain a carbon-containing scandium-zirconium solution; and then spray drying the carbon-containing scandium-zirconium solution to obtain a precursor powder;

[0045] Step 4) heat-treating the precursor powder in a Joule heating device to obtain scandium-zirconium powder.

[0046] This application uses a scandium-zirconium synergistic extractant to simultaneously extract scandium and zirconium from waste zirconium oxychloride acid, achieving comprehensive utilization of scandium-zirconium resources. The addition of a carbon source allows the scandium-zirconium solution to form pellets with the carbon source during the spray drying process. The carbon source is then rapidly heated through Joule heating, causing rapid oxidation. The rapid heating and cooling suppresses the agglomeration of the scandium-zirconium powder during the oxidation process. Too little carbon source will not significantly suppress particle agglomeration, while too much can easily lead to waste of raw materials and environmental pollution.

[0047] Optionally, the scandium-zirconium synergistic extractant comprises compound A, compound B and sulfonated kerosene in a volume ratio of 10-20:20-35:45-65,

[0048] Wherein, the compound A includes at least one of P204 (diisooctyl phosphate), di(2-ethylhexyl)phenyl phosphate (CAS: 16368-97-1), and bis(2,4,4-trimethylpentyl)phosphonic acid (cyanex272, CAS: 83411-71-6);

[0049] The compound B includes at least one of TBP (tributyl phosphate) and cyanex923 extractant;

[0050] In the present application, sulfonated kerosene, also known as No. 260 solvent oil, is a conventional reagent in the field and can be obtained through commercial channels.

[0051] Optionally, the scandium-zirconium synergistic extractant also includes a synergist C, which includes at least one of 1-hexyl-3-methylimidazolium bistrifluoromethanesulfonyl imide (CAS: 916729-96-9), 1-butyl-3-methylimidazolium hexafluorophosphate (CAS: 174501-64-5), and N-butylpyridinium nitrate ([C4py][NO3]). In this application, synergist C is a modified ionic liquid that provides a special microenvironment, enhancing selectivity for Sc and Zr. It also functions as both an extractant and a diluent, reducing the use of sulfonated kerosene.

[0052] In some optional embodiments, the scandium-zirconium synergistic extractant comprises compound A, compound B, synergistic extractant C and sulfonated kerosene in a volume ratio of 10-20:20-35:10-15:45-65.

[0053] Optionally, in step 2), the stripping agent is a 3-8 mol / L hydrochloric acid aqueous solution, the stripping temperature is controlled at 20-50° C., the stripping time is 10-120 min, and the stripping stage is 5-8 countercurrent stripping stages.

[0054] Optionally, the heat treatment temperature is 700 to 1300° C., the heating rate is 200-1000° C. / s, and the holding time is 1-3600s;

[0055] The present invention controls the heat treatment temperature to 700-1300°C, which facilitates the transformation of the amorphous scandium-zirconium precursor into cubic scandium-zirconium powder. Heat treatment temperatures that are too high can easily lead to particle agglomeration, while too low a temperature may not fully transform the crystal structure. The heating rate of 200-1000°C / s is used in this application to rapidly increase the temperature, preventing the scandium-zirconium powder from agglomerating and thus preventing particle compaction.

[0056] In this application, a high-purity scandium-zirconium precursor solution is produced through early synergistic extraction and impurity removal and stripping, achieving efficient and comprehensive resource utilization and turning waste into treasure. The synergistic effect of spray drying and heat treatment under specific conditions can achieve a scandium-zirconium powder particle size D50 of less than 0.25μm.

[0057] Beneficial effects of this application:

[0058] The preparation method of scandium-zirconium powder provided in the present application includes the following steps: S1, preparing a scandium-zirconium mixed solution according to the composition of the target product, adding a carbon source, and the mass ratio of the carbon source to the cations in the scandium-zirconium mixed solution is 5:1-50 to obtain a carbon-containing scandium-zirconium solution; then spray drying the carbon-containing scandium-zirconium solution to obtain a precursor powder; S2, heat treating the precursor powder to obtain scandium-zirconium powder; the heat treatment temperature is 700 to 1300°C, the heating rate is 200-1000°C / s, and the holding time is 1-3600s. The present application generates a granulated spherical powder of an amorphous scandium-zirconium precursor and a carbon source by reacting a scandium-zirconium mixed solution and a carbon source during a spray drying process. The carbon source is evenly distributed in the granulated balls, which inhibits the agglomeration of the scandium-zirconium precursor. The powder is then rapidly heated to a heat treatment temperature for heat treatment. The prepared scandium-zirconium powder has a narrow particle size distribution range, achieving good control of the particle size. In addition, the preparation method of the scandium-zirconium powder provided by the present application has mild reaction conditions, low equipment requirements, and reduced energy consumption and costs.

[0059] The preparation method of scandium-zirconium powder provided in the present application uses waste zirconium oxychloride acid as raw material. By selecting a scandium-zirconium synergistic extraction agent of a specific composition, a scandium-zirconium solution is synergistically extracted from the waste zirconium oxychloride acid, thereby turning waste into treasure and reducing costs. The performance of the obtained scandium-zirconium powder is no significantly different from that of fresh raw materials. DETAILED DESCRIPTION

[0060] Various exemplary embodiments of the present application are now described in detail. This detailed description should not be considered as a limitation of the present application, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present application. It should be understood that the terms used in this application are only for describing specific embodiments and are not intended to limit the present application.

[0061] In addition, for numerical ranges in this application, it is understood that each intervening value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any stated value or stated range, and any other stated value or intervening value in the stated range, is also encompassed within this application. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0062] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0063] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application relates. Although this application describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of this application.

[0064] The zirconium oxychloride waste acid used in this application comes from a certain company. Its components include zirconium, scandium, titanium, and iron, with scandium concentrations ranging from 1-5 g / L, zirconium concentrations from 50-80 g / L, titanium concentrations from 5-10 g / L, and iron concentrations from 3-10 g / L. To facilitate data comparison, the zirconium oxychloride waste acid in the following examples and comparative examples contains, by element, 4 g / L of scandium, 70 g / L of zirconium, 5 g / L of titanium, and 5 g / L of iron.

[0065] Example 1

[0066] This embodiment provides a scandium-zirconium powder, and the specific preparation steps and operating parameters are as follows:

[0067] 1) A scandium-zirconium synergistic extractant consisting of a mixture of cyanex272, cyanex923, 1-hexyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide salt and sulfonated kerosene (No. 260 solvent oil, manufactured by Guangdong Zhengmao Petrochemical, the same below) in a volume ratio of 15:35:10:55 was used to extract the waste zirconium oxychloride acid. The extraction temperature was controlled at 25°C, the extraction time was 30 minutes, and the extraction stage was 4 countercurrent extraction. An organic phase loaded with scandium and zirconium (containing a scandium-zirconium extract) was obtained.

[0068] 2) The obtained organic phase loaded with scandium and zirconium was subjected to 8-stage countercurrent washing to effectively remove impurities. The washing liquid used was a mixed aqueous solution of sodium sulfite and sulfuric acid with a pH of 1.5, a molar ratio of sodium sulfite to sulfuric acid of 1:3, and a washing temperature of 40°C.

[0069] 3) Stripping the impurity-removed, finely loaded scandium-zirconium organic phase with a stripping agent. The stripping agent solution is a 5 mol / L hydrochloric acid aqueous solution. The stripping temperature is controlled at 30° C., the stripping time is 60 minutes, and the stripping stage is 7 countercurrent stripping stages to obtain a scandium-zirconium stripping solution.

[0070] 4) The stripping solution is supplemented with zirconium oxychloride solution and / or scandium chloride solution at a scandium oxide to zirconium oxide doping molar ratio of 10:90 to obtain a scandium-zirconium mixed solution (the Fe2O3 and TiO2 contents are tested). Citric acid is then added to dissolve the solution and the solution is transferred to a spray drying vessel for spray drying. In this step, the spray inlet temperature is controlled at 140°C, the molar ratio of citric acid to cations in the scandium-zirconium mixed solution is 5:3, and the cation concentration in the scandium-zirconium mixed solution is 0.5 mol / l.

[0071] 5) The prepared product was placed in a Joule heating device for reaction, rapidly heating and cooling to form scandium-zirconium powder. In this step, the maximum temperature generated by Joule heating was 1100°C, the heating rate was 800°C / s, and the holding time was 100s.

[0072] Example 2

[0073] This embodiment provides a scandium-zirconium powder, and the specific preparation steps and operating parameters are as follows:

[0074] 1) Zirconium oxychloride waste acid was extracted with a scandium-zirconium synergistic extractant consisting of P204 (diethyl phosphate), cyanex923, 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), and sulfonated kerosene in a volume ratio of 10:25:15:65. The extraction temperature was controlled at 20°C, the extraction time was 120 min, and the extraction stage was 5 countercurrent extraction to obtain an organic phase loaded with scandium and zirconium.

[0075] 2) The obtained organic phase loaded with scandium and zirconium was subjected to six levels of countercurrent washing to effectively remove impurities. The washing liquid used was a mixed aqueous solution of sodium metabisulfite and hydrochloric acid with a pH of 1, a molar ratio of sodium metabisulfite to hydrochloric acid of 1:5, and a washing temperature of 30°C.

[0076] 3) Stripping the impurity-removed, finely loaded scandium-zirconium organic phase with a stripping agent. The stripping agent solution is a 7 mol / L hydrochloric acid aqueous solution. The stripping temperature is controlled at 20° C., the stripping time is 120 minutes, and the stripping stage is 5 countercurrent stripping to obtain a scandium-zirconium stripping solution.

[0077] 4) The stripping solution is supplemented with zirconium oxychloride solution and / or scandium chloride solution at a scandium oxide to zirconium oxide doping molar ratio of 6:94 to produce a scandium-zirconium mixed solution. Polyvinyl alcohol (20,000 molecular weight) is then added to dissolve the solution and transferred to a spray drying vessel for reaction. During this step, the spray inlet temperature is controlled at 160°C, the molar ratio of polyvinyl alcohol to the scandium-zirconium mixed solution cations is 5:1, and the cation concentration in the scandium-zirconium mixed solution is 1 mol / l.

[0078] 5) The prepared product was placed in a Joule heating device for reaction, rapidly heating and cooling to form scandium-zirconium powder. In this step, the maximum temperature generated by Joule heating was 1200°C, the heating rate was 500°C / s, and the holding time was 50s.

[0079] Example 3

[0080] This embodiment provides a scandium-zirconium powder, and the specific preparation steps and operating parameters are as follows:

[0081] 1) A scandium-zirconium synergistic extractant consisting of a mixture of TBP (tributyl phosphate), cyanex272, N-butylpyridinium nitrate ([C4py][NO3]) and sulfonated kerosene in a volume ratio of 20:20:13:50 was used to extract the waste zirconium oxychloride acid. The extraction temperature was controlled at 50°C, the extraction time was 10 min, and the extraction stage was three-stage countercurrent extraction to obtain an organic phase loaded with scandium and zirconium.

[0082] 2) The obtained organic phase loaded with scandium and zirconium was subjected to four-stage countercurrent washing to effectively remove impurities. The washing liquid used was a mixed aqueous solution of sodium thiosulfate and nitric acid with a pH of 2, a molar ratio of sodium thiosulfate to nitric acid of 1:2, and a washing temperature of 50°C.

[0083] 3) Stripping the impurity-removed, finely loaded scandium-zirconium organic phase with a stripping agent. The stripping agent solution is an 8 mol / L aqueous nitric acid solution. The stripping temperature is controlled at 50° C., the stripping time is 10 minutes, and the stripping stage is 8 countercurrent stripping stages to obtain a scandium-zirconium stripping solution.

[0084] 4) The stripping solution is supplemented with zirconyl nitrate solution and / or scandium nitrate solution at a scandium oxide to zirconium oxide doping molar ratio of 12:88. Polyvinyl pyrrolidone (8000 molecular weight) is then added for dissolution and transferred to a spray drying vessel for reaction. During this step, the spray inlet temperature is controlled at 110°C, the molar ratio of cations in the polyvinyl pyrrolidone to the scandium-zirconium mixed solution is 1:10, and the cation concentration in the scandium-zirconium mixed solution is 0.1 mol / l.

[0085] 5) The prepared product was placed in a Joule heating device for reaction, rapidly heating and cooling to form scandium-zirconium powder. In this step, the maximum temperature generated by Joule heating was 700°C, the heating rate was 1000°C / s, and the holding time was 600s.

[0086] Example 4

[0087] This embodiment provides a scandium-zirconium powder, and the specific preparation steps and operating parameters are as follows:

[0088] 1) Zirconium oxychloride waste acid was extracted with a scandium-zirconium synergistic extractant consisting of P204 (diethyl phosphate), TBP (tributyl phosphate), 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), and sulfonated kerosene in a volume ratio of 13:30:12:45. The extraction temperature was controlled at 35°C, the extraction time was 60 min, and the extraction stage was four countercurrent extraction to obtain an organic phase loaded with scandium and zirconium.

[0089] 2) The obtained organic phase loaded with scandium and zirconium was subjected to 7-stage countercurrent washing to effectively remove impurities. The washing liquid used was a mixed aqueous solution of sodium dithionite and sulfuric acid with a pH of 1.2, a molar ratio of sodium dithionite to sulfuric acid of 1:4, and a washing temperature of 35°C.

[0090] 3) Stripping the impurity-removed, finely loaded scandium-zirconium organic phase with a stripping agent. The stripping agent solution is a 3 mol / L aqueous sulfuric acid solution. The stripping temperature is controlled at 35° C., the stripping time is 30 minutes, and the stripping stage is 6, with countercurrent stripping, to obtain a scandium-zirconium stripping solution.

[0091] 4) The stripping solution is supplemented with zirconium oxychloride solution and / or scandium chloride solution at a scandium oxide to zirconium oxide doping ratio of 5:95. Polyethylene glycol with a molecular weight of 10,000 is then added for dissolution and transferred to a spray drying vessel for reaction. During this step, the spray inlet temperature is controlled at 180°C, the molar ratio of the polyethylene glycol to the cations in the scandium-zirconium mixed solution is 1:6, and the cation concentration in the scandium-zirconium mixed solution is 1.5 mol / L.

[0092] 5) The prepared product was placed in a Joule heating device for reaction, rapidly heating and cooling to form scandium-zirconium powder. In this step, the maximum temperature generated by Joule heating was 1000°C, the heating rate was 500°C / s, and the holding time was 10s.

[0093] Example 5

[0094] The difference from Example 1 is that the number of washing stages in step 2) is 2.

[0095] Example 6

[0096] The difference from Example 1 is that the mass ratio of cations in the mixed solution of citric acid and scandium zirconium is 1:7.

[0097] Example 7

[0098] The difference from Example 1 is that the cation concentration in the scandium-zirconium mixed solution is 4 mol / l.

[0099] Example 8

[0100] The difference from Example 1 is that the maximum temperature generated by Joule heat is 1300°C.

[0101] Example 9

[0102] The difference from Example 1 is that the heating rate is 200° C. / s and the holding time is 3600 s.

[0103] Example 10

[0104] The difference from Example 1 is that a scandium-zirconium synergistic extractant prepared by mixing cyanex272, cyanex923 and sulfonated kerosene in a volume ratio of 15:35:55 is used to extract the zirconium oxychloride waste acid. The result is low selectivity for scandium and zirconium and high levels of impurity elements.

[0105] Example 11

[0106] The difference from Example 1 is that zirconium oxychloride and scandium chloride are directly used to prepare the scandium-zirconium mixed solution.

[0107] Example 12

[0108] The difference from Example 1 is that no sodium sulfite reducing agent is added in step 2).

[0109] Comparative Example 1

[0110] The difference from Example 1 is that after spray drying in step S4, calcination is performed in an ordinary muffle furnace at a calcination temperature of 900°C, a heating rate of 10°C / min, and a holding time of 3 hours, so that sintering necks are formed between the scandium-zirconium powder particles.

[0111] Comparative Example 2

[0112] The difference from Example 1 is that no carbon source is added to the scandium-zirconium solution.

[0113] Comparative Example 3

[0114] The difference from Example 1 is that the stripping solution is supplemented with zirconium oxychloride solution and / or scandium chloride solution according to the scandium oxide and zirconium oxide doping ratio of 10:90, followed by a coprecipitation reaction, and the pH of the scandium zirconium mixed solution is adjusted to 9 by adding ammonia water to obtain a scandium zirconium precursor solution, which is then gelled with hydrochloric acid to adjust the pH to 6. The prepared scandium zirconium precursor solution is filtered and repeatedly washed with water until there is no chloride ion. The precipitated colloid is slurried to a solid content of 8% in the slurry, and the slurry is fed into a spray pyrolysis device for one-step continuous rapid atomization, drying, thermal decomposition and sintering to obtain scandium zirconium powder. The ultrasonic nozzle power is 15W, the carrier gas flow rate is 30L / min, and the spray pyrolysis temperature is 1100°C.

[0115] Test Case

[0116] The particle size and electrical conductivity of the scandium-zirconium powders provided in the examples and comparative examples of the present application were tested. The specific testing methods are as follows:

[0117] 1. Particle size test

[0118] The particle sizes D10, D50 and D90 of the scandium-zirconium powders prepared in the examples and comparative examples were measured using a British Malvern MASTERSIZER 3000 laser particle size tester.

[0119] The span of a particle size distribution is a parameter that describes the width of the particle size distribution. In particle size analysis, the span is used to measure the breadth of the particle size distribution, that is, the range of particle sizes.

[0120] The span is usually calculated using the three parameters D10, D50 and D90, which represent the particle sizes at 10%, 50% and 90% of the cumulative percentage respectively. The formula for span is usually:

[0121]

[0122] Typically, the span value ranges from 0 to 10. A smaller span indicates a more concentrated particle size distribution; a larger span indicates a more dispersed particle size distribution.

[0123] In engineering and materials science, span is often used to assess the uniformity of particle size distribution and the granular properties of a material.

[0124] 2. Conductivity test

[0125] The conductivity of the scandium oxide stabilized zirconia electrolyte ceramic sheet (the ceramic sheet is made by pressing the scandium oxide zirconium powder prepared in Examples 1 to 11 and Comparative Examples 1 to 3 and then sintering at 1500°C for 5 hours, with a diameter of 15 mm and a thickness of 2 mm) is tested using AC impedance spectroscopy.

[0126] The specific test results are summarized in the following table:

[0127] Table 1

[0128]

[0129]

[0130] Note: “<0.0001” in the last two columns of the table means not detected, which is below the detection limit.

[0131] From the above description, it can be seen that the above embodiments of the present application achieve the following technical effects:

[0132] By comparing the embodiments and comparative examples, it can be seen that the preparation method provided in this application can produce scandium-zirconium powder with a particle size D50 < 0.25 μm, a relatively small span of particle size distribution, and a narrow particle size distribution. The obtained scandium-zirconium powder has a high electrical conductivity.

[0133] Comparing Example 1 and Example 5, it can be seen that limiting the number of countercurrent washing stages to the preferred range of the present application is beneficial to reducing the impurity content in the scandium-zirconium mixed solution and obtaining higher conductivity.

[0134] Comparing Example 1 and Example 6, it can be seen that limiting the mass ratio of the carbon source and the cations of the scandium-zirconium mixed solution to the preferred range of this application is beneficial to inhibiting particle agglomeration, reducing the particle size of the powder, achieving a narrower particle size distribution, and obtaining higher conductivity.

[0135] Comparing Example 1 and Example 7, it can be seen that limiting the cation concentration of the scandium-zirconium mixed solution to the preferred range of this application is beneficial to reducing the particle size of the powder, achieving a narrower particle size distribution, and obtaining higher conductivity.

[0136] Comparing Example 1 with Example 8 and Example 9, it can be seen that limiting the maximum Joule heat temperature, heating rate, and holding time within the preferred range of this application is beneficial to reducing the particle size of the powder, achieving a narrow particle size distribution, and obtaining higher electrical conductivity.

[0137] Comparing Example 1 and Example 10, it can be seen that the use of co-extractant C can improve the extraction rate of scandium and zirconium in waste acid, reduce the impurity content, and achieve effective recovery of scandium and zirconium.

[0138] Comparing Example 1 and Example 11, it can be seen that when scandium zirconium powder is prepared using waste zirconium oxychloride acid as raw material, the performance of the obtained product is close to that of the product prepared from fresh raw materials, with no significant difference.

[0139] Comparing Example 1 and Example 12, it can be seen that the addition of the reducing agent can reduce the impurity content in the scandium-zirconium stripping solution and achieve effective recovery of scandium-zirconium.

[0140] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing scandium-zirconium powder, characterized in that: The steps include: S1, preparing a scandium-zirconium mixed solution according to the composition of the target product, adding a carbon source, wherein the mass ratio of the carbon source to the cations in the scandium-zirconium mixed solution is 5:1-50, to obtain a carbon-containing scandium-zirconium solution; and then spray drying the carbon-containing scandium-zirconium solution to obtain a precursor powder; S2, heat-treating the precursor powder to obtain scandium-zirconium powder; the heat treatment temperature is 700 to 1300° C., the heating rate is 200-1000° C. / s, and the holding time is 1-3600s.

2. The method for preparing scandium-zirconium powder according to claim 1, wherein In S1, waste zirconium oxychloride acid is used to prepare a scandium-zirconium mixed solution, which includes the following steps: S11, extracting the zirconium oxychloride waste acid using a scandium-zirconium synergistic extractant to obtain a scandium-zirconium extract; S12, stripping the scandium-zirconium extract with a stripping agent to obtain a scandium-zirconium stripping solution, and regulating the ratio of the scandium-zirconium element in the scandium-zirconium stripping solution according to the composition of the target product to obtain a scandium-zirconium mixed solution; Wherein, in S11, the scandium-zirconium synergistic extractant comprises compound A, compound B and sulfonated kerosene in a volume ratio of 10-20:20-35:45-65, Wherein, the compound A comprises at least one of diisooctyl phosphate, di(2-ethylhexyl)phenyl phosphate, and bis(2,4,4-trimethylpentyl)phosphonic acid; The compound B includes at least one of tributyl phosphate and trialkylphosphine oxide.

3. The method for preparing scandium-zirconium powder according to claim 2, wherein: In S11, the scandium-zirconium synergistic extractant includes compound A, compound B, synergistic extractant C, and sulfonated kerosene in a volume ratio of 10-20:20-35:10-15:45-65; The co-extractant C includes at least one of 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, 1-butyl-3-methylimidazolium hexafluorophosphate, and N-butylpyridine nitrate.

4. The method for preparing scandium-zirconium powder according to claim 2, wherein: In S11, the extraction temperature is 20-50°C, the extraction time is 10-120 min, and the extraction is 3-5 stage countercurrent extraction; And / or, a washing and impurity removal step is further included after the extraction; Optionally, the washing and impurity removal adopts a mixed aqueous solution of a reducing agent and an inorganic acid with a pH of 1-2, wherein the molar ratio of the reducing agent to the inorganic acid is 1:2-5, the washing and impurity removal adopts countercurrent washing, the washing stage number is 4-8 stages, and the washing temperature is 30-50°C; Optionally, the reducing agent includes at least one of sodium sulfite, sodium metabisulfite, sodium thiosulfate and sodium dithionite.

5. The method for preparing scandium-zirconium powder according to claim 2, wherein: In S12, the stripping agent is a 3-8 mol / L inorganic acid aqueous solution, the stripping temperature is 20-50° C., the stripping time is 10-120 min, and the stripping is 5-8 level countercurrent stripping; Optionally, the inorganic acid in the inorganic acid aqueous solution includes at least one of hydrochloric acid, nitric acid and sulfuric acid.

6. The method for preparing scandium-zirconium powder according to any one of claims 1 to 5, characterized in that: In S1, the cation concentration in the scandium-zirconium mixed solution is 0.1-4 mol / L; and / or, the mass ratio of the carbon source to the cations in the scandium-zirconium mixed solution is 5:2-30; and / or, the inlet temperature of the spray drying is 110-180° C.; And / or, the carbon source includes at least one of citric acid, polyethylene glycol, polyvinyl alcohol, and polyvinyl pyrrolidone.

7. The method for preparing scandium-zirconium powder according to claim 6, characterized in that: In S1, the mass ratio of the carbon source to the cations in the scandium-zirconium mixed solution is 5:3-15; and / or, the inlet temperature of the spray drying is 110-150° C., optionally, the inlet temperature of the spray drying is 120-140° C.; And / or, the cation concentration in the scandium-zirconium mixed solution is 0.5-1 mol / l.

8. The method for preparing scandium-zirconium powder according to any one of claims 1 to 5, characterized in that: In S2, the heating rate of the heat treatment is 500-1000°C / s, and the holding time is 10-600s; optionally, the heating rate is 500-800°C / s, and the holding time is 10-100s; And / or, the heat treatment temperature is 900 to 1200°C, optionally, the heat treatment temperature is 1000 to 1100°C.

9. Scandium-zirconium powder prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the scandium-zirconium powder according to claim 9 in a solid oxide fuel cell.

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