A method for recovering valuable elements from waste metal catalysts

Abstract

The present invention discloses a method for recovering valuable elements from waste metal catalysts. The method comprises the following steps: (1) alkaline leaching: pre-treated waste acrylonitrile catalyst is subjected to alkaline leaching, followed by solid-liquid separation to obtain filtrate I and filter residue I; (2) ion exchange: filtrate I obtained in step (1) is subjected to ion exchange to obtain exchange liquid II, and exchange liquid II is crystallized to obtain a molybdenum silicic acid product; (3) acid leaching: filter residue I obtained in step (1) is subjected to acid leaching, followed by solid-liquid separation to obtain filtrate II and filter residue II, and filter residue II is dried to obtain a Si-containing product; (4) extraction and stripping: Mo and Fe are extracted from filtrate II obtained in step (3) to obtain extract III and raffinate III, and extract III is stripped in steps and post-treated to obtain Fe-containing and Mo-containing products, respectively; (5) precipitation: Bi, Ni, and Mg are recovered in sequence. The method has the characteristics of high metal recovery rate, high selectivity, and high product purity.

Description

Technical Field

[0001] The present invention relates to the technical field of waste catalyst recovery, and more particularly to a method for resource utilization of waste metal catalysts. Background Art

[0002] Catalysts play a vital role in the modern chemical industry, with statistics showing that catalysts are used in over 90% of industrial processes. Globally, approximately 800,000 tons of solid catalysts are consumed annually, generating 500,000 to 700,000 tons of waste catalysts. With economic development, this amount of waste catalyst is expected to increase further. In recent years, with increasing attention to environmental protection and rising metal prices, numerous companies and research institutions have begun recovering valuable metals such as platinum, palladium, gold, rhodium, ruthenium, cobalt, aluminum, rhenium, nickel, and copper from spent catalysts.

[0003] Common recovery methods for various types of spent industrial catalysts are generally categorized as dry, wet, and a combination of dry and wet methods. Dry recovery is currently relatively mature due to its simplicity and lack of engineering expertise. However, it cannot separate similar metals and also suffers from high energy consumption and pollution. Wet recovery, on the other hand, is more suitable for processing complex secondary resources like spent catalysts. Its closed material transport pipelines eliminate the generation of toxic and hazardous gases. However, wet recovery processes are lengthy, and much research remains at the laboratory level. A comprehensive, industrially viable technology has yet to be developed.

[0004] Currently, almost all industrial acrylonitrile production uses the propylene ammoxidation process, requiring tens of thousands of tons of catalyst per year with a lifespan of typically 4 to 7 years. The catalysts used primarily include antimonates and molybdates, with molybdenum, bismuth, and iron being the dominant group (approximately 90%) in molybdate catalysts. Bismuth accounts for approximately 1% to 5% of this type of catalyst, nickel for approximately 1% to 10%, and molybdenum for approximately 5% to 21%. Failure to recycle the valuable metals after deactivation can lead to a significant waste of resources, and improper disposal can also result in solid waste that pollutes the environment. Therefore, recycling the valuable metals from spent catalysts offers significant economic and environmental benefits. Currently, there are very few reports on the recovery of valuable elements from discarded acrylonitrile catalysts. Wang Chongxin restored the activity of the catalyst by adding elements to the waste acrylonitrile catalyst to adjust the composition and then carried out a series of treatments (Wang Chongxin. Research and industrial investigation on the recovery of acrylonitrile catalyst, Lanhua Science and Technology, 4: 261-264); Zhu Binyao et al. used acid leaching-hydrolysis to recover bismuth and nickel from waste acrylonitrile catalyst (Zhu Binyao, Liu Jianshe, Zhu Ailan, Zhou Jun, Wu Liuxi. Study on leaching and separation of bismuth and nickel from waste acrylonitrile catalyst, Mining and Metallurgical Engineering, 2014, 34(6): 70-75); CN201110223824.1 disclosed a method for recovering valuable metals from waste acrylonitrile catalyst; Liu Xiuqing et al. used acid leaching followed by alkaline leaching to suppress the dissolution of carrier aluminum oxide and silicon dioxide and effectively separate the valuable elements (Liu Xiuqing, Xu Sumin, Wen Junjie. 65 # Research on comprehensive recovery of spent acrylonitrile catalysts. Inorganic Salt Industry, 2002, 34(5):35-36); Qiu Zhaofu et al. used an oxidative leaching method to transfer Mo from spent acrylonitrile catalysts into a solution to achieve the separation of Mo and Ni (Jian Liu, Zhaofu Qiu, Ji Yang, Limei Cao, Wei Zhang. Recovery of Mo and Ni from spent acrylonitrile catalysts using an oxidation leaching–chemical precipitation technique, Hydrometallurgy 164(2016)64–70). None of the above methods can achieve the comprehensive recovery of valuable elements in spent catalysts, and the separation of the elements is not complete. Summary of the Invention

[0005] To address the problem of low selectivity in separating valuable metals from waste metal catalysts in the prior art, the present invention provides a method for recovering valuable elements from waste metal catalysts. The method has the characteristics of high metal recovery rate, high selectivity, and high product purity.

[0006] The present invention provides a method for recovering valuable elements from waste metal catalysts, comprising the following steps:

[0007] (1) Alkali leaching: alkali leaching of the pretreated waste acrylonitrile catalyst, solid-liquid separation, and obtaining filtrate I and filter residue I;

[0008] (2) ion exchange: the filtrate I obtained in step (1) is subjected to ion exchange to obtain exchange liquid II, and the exchange liquid II is crystallized to obtain a molybdosilicic acid product;

[0009] (3) Acid leaching: The filter residue I obtained in step (1) is subjected to acid leaching, solid-liquid separation, and filtrate II and filter residue II are obtained. The filter residue II is dried to obtain the Si-containing product;

[0010] (4) Extraction and stripping: Mo and Fe are extracted from the filtrate II obtained in step (3) to obtain an extract III and a raffinate III. The extract III is stripped in steps and post-treated to obtain Fe-containing and Mo-containing products, respectively;

[0011] (5) precipitation: adding a precipitant to the raffinate III obtained in step (4), and recovering Bi, Ni, and Mg in sequence under different precipitation conditions;

[0012] The waste acrylonitrile catalyst comprises a metal active element composite oxide and a carrier, wherein the carrier is silicon dioxide, and the metal active elements comprise Mo, Fe, Bi, Ni, and Mg.

[0013] In the above technical solution, the composition of the waste acrylonitrile catalyst in step (1), based on the mass of the catalyst, includes: Bi content of 0.1% to 10%, Fe content of 0.1% to 10%, Mg content of 0.1% to 10%, Mo content of 0.1% to 40%, Ni content of 0.1% to 20%, and Si content of 1% to 40%. The waste acrylonitrile catalyst may further include at least one of Cr, Rb, K, Cs, P, B, Ce, Sb, and Mn.

[0014] In the above technical solution, the operating conditions of the pretreatment in step (1) are: calcination at a temperature of 400°C to 800°C for 2h to 10h.

[0015] In the above technical solution, the alkaline leaching agent in step (1) is a solution containing hydroxide, and the preferred alkaline leaching agent includes at least one of sodium hydroxide and potassium hydroxide.

[0016] In the above technical solution, the waste acrylonitrile catalyst described in step (1) comes from the waste catalyst of the propylene ammoxidation device.

[0017] In the above technical solution, the concentration of the alkaline leaching agent in step (1) is 0.5 mol / L to 10 mol / L, the reaction temperature is 50°C to 200°C, and the reaction time is 0.5 h to 48 h. Preferably, the concentration of the alkaline leaching agent is 3 mol / L to 10 mol / L, the reaction temperature is 80°C to 200°C, and the reaction time is 1 h to 3 h.

[0018] In the above technical solution, the filtrate I obtained in step (1) is measured using an inductively coupled plasma emission spectrometer (ICP, Varian, 725-ES) to measure the concentrations of Bi, Fe, Mg, Mo, and Ni in the filtrate I. The leaching rate is defined as the metal content in the filtrate divided by the total mass of the metal in the raw material. The leaching rate of Mo is 50% to 100%, the leaching rate of Si is 40% to 80%, and the leaching rates of Bi, Fe, Mg, and Ni are all less than 10%, preferably less than 6%.

[0019] In the above technical solution, hydrogen-type cation exchange resin is used for exchange in the ion exchange process described in step (2), and Na ions are exchanged onto the resin to obtain exchange liquid II, which is evaporated and crystallized to obtain molybdosilicic acid product.

[0020] In the above technical solution, hydrogen-type cation exchange resin is used for exchange in the ion exchange process described in step (2), and preferred resins include 732 hydrogen-type strong acid cation exchange resin, IR-120 cation exchange resin, macroporous strong acid styrene cation exchange resin, etc.

[0021] In the above technical solution, the acidic leaching agent in step (3) is an acidic solvent containing hydrogen ions, and the preferred acidic leaching agent includes at least one of nitric acid, sulfuric acid, hydrochloric acid, and perchloric acid.

[0022] In the above technical solution, the H of the acidic leaching agent in step (3) is + The concentration is 1.5mol / L to 10mol / L, the reaction temperature is 50℃ to 200℃, and the reaction time is 0.5h to 48h. + The concentration is 3 mol / L to 10 mol / L, the reaction temperature is 90°C to 200°C, and the reaction time is 1h to 3h.

[0023] In the above technical solution, the leaching rate of Bi in the filtrate II in step (3) is 25% to 100%, the leaching rate of Fe is 60% to 100%, the leaching rate of Mo is 20% to 100%, the leaching rate of Mg is 80% to 100%, the leaching rate of Ni is 80% to 100%, and the leaching rate of Si is less than 5%.

[0024] In the above technical solution, the organic acidic extractant used in the extraction described in step (4) is preferably at least one of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (P507), di(2-ethylhexyl)phosphoric acid (P204), and di-(2,4,4-trimethylpentyl)phosphonic acid (Cyanex272).

[0025] In the above technical solution, the extraction conditions of step (4) are as follows: reaction time 10 min to 24 h, extractant concentration 10 vol.% to 30 vol.%, aqueous phase / organic phase volume ratio (A / O) 0.1:1 to 2:1, and reaction temperature 0°C to 60°C. Preferably, the extraction conditions are as follows: reaction time 20 min to 2 h, extractant concentration 10 vol.% to 30 vol.%, aqueous phase / organic phase volume ratio (A / O) 0.5:1 to 1.2:1, and reaction temperature 20°C to 30°C.

[0026] In the above technical solution, the specific operation of the stepwise stripping described in step (4) is: first, Fe is stripped with acid, and then Mo is stripped with alkali, and the extractant is acid-washed and reused; wherein the acid used is one or more of hydrochloric acid, sulfuric acid, and oxalic acid with a concentration of 2 mol / L to 4 mol / L; the alkali used is NH4 + The alkaline solution with a concentration of 1 mol / L to 10 mol / L is selected from one or more of ammonium sulfate, ammonium chloride, ammonium nitrate, ammonium carbonate, ammonium bicarbonate, and ammonia water.

[0027] In the above technical solution, the single-stage extraction rates of Mo and Fe in step (4) are 80% to 100% and 40% to 100% respectively. If the extraction rates are low, a multi-stage extraction method can be used.

[0028] In the above technical solution, the raffinate III in step (5) is added with a precipitant, wherein the precipitant is selected from at least one of sodium hydroxide and potassium hydroxide, and the pH value is adjusted step by step to 5-6, 6-8.4 and 8.4-14. According to the solubility product constant (K sp ) calculation, bismuth hydroxide product is obtained when the pH value is below 6, nickel hydroxide product is obtained when the pH value is between 6 and 8.4, and magnesium hydroxide product is obtained when the pH reaches above 8.4.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] The present invention provides a method for recovering valuable elements from waste metal catalysts. By adopting a step-by-step dissolution method, Mo and Si are first highly selectively dissolved, and then the metal elements Bi, Fe, Mg, Mo, and Ni in the leached residue are dissolved, thereby reducing the cost of subsequent separation, achieving high-value-added utilization of all elements, and providing technical support for the recovery of metal elements from other waste catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the process flow of the present invention;

[0032] Figure 2 The following are SEM images of the nickel hydroxide and magnesium hydroxide products obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0033] The recovery method provided by the present invention is further described below with reference to the embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0034] In the present invention, the scanning electron microscope (SEM) images of the example samples were taken on a Hitachi S-4800II scanning electron microscope.

[0035] Example 1

[0036] (1) Pretreatment: A waste metal catalyst raw material (mass percentage of Bi is 1.8%, Fe is 2.8%, Mg is 0.9%, Mo is 22%, Ni is 7%, and Si is 24%) is put into a muffle furnace, and the roasting temperature is 550°C and the roasting time is 4 hours to obtain material I.

[0037] Alkali Leaching: Material I was leached with 4 mol / L sodium hydroxide at 120°C for 1 hour, followed by solid-liquid separation to obtain filtrate I and residue I. The concentrations of Bi, Fe, Mg, Mo, and Ni in filtrate I were measured using an inductively coupled plasma optical emission spectrometer (ICP, Varian, 725-ES). The leaching rate is defined as the metal content in the filtrate divided by the total mass of the metal in the raw material. Based on the ICP results, the leaching rate of Mo was calculated to be 99.6%, the leaching rate of Si was 65.5%, and the leaching rates of Bi, Fe, Mg, and Ni were all 0%.

[0038] (2) Ion exchange: Filtrate I is passed through 732 hydrogen type cation exchange resin to obtain exchange liquid II, and exchange liquid II is evaporated and crystallized to obtain molybdosilicic acid product.

[0039] (3) Acid leaching: The filter residue I was leached with 3 mol / L nitric acid at 90°C for 1 h, and the solid-liquid separation was performed to obtain filtrate II and filter residue II. The filter residue II was dried to obtain the silica product. The ICP analysis results of the filtrate II showed that the leaching rates of Bi were 97%, Fe were 92%, Mg were 100%, Ni were 99.7%, Mo were 94.5%, and Si were 0%.

[0040] (4) Extraction and back-extraction: P507 was used to extract Mo and Fe from the filtrate II. The extraction conditions were: reaction time 40 min, extractant concentration 20 vol.%, aqueous phase / organic phase volume ratio (A / O) 1:1, reaction temperature 25 °C, and Mo and Fe extraction rates of 98.4% and 96%, respectively. Extract III and raffinate III were obtained. Extract III was back-extracted with Fe using 4 mol / L hydrochloric acid, and then with 1 mol / L ammonia water + 1 mol / L ammonium chloride to back-extract Mo. After post-treatment, products containing Fe and Mo were obtained, respectively. The extractant was acid-washed and reused.

[0041] (5) Precipitation: The raffinate III is precipitated with sodium hydroxide to obtain bismuth hydroxide at pH = 6, nickel hydroxide at pH = 8.3, and magnesium hydroxide at pH = 11.76. The remaining liquid is evaporated and crystallized to obtain sodium nitrate crystals.

[0042] The process flow diagram of this embodiment is shown in Figure 1 The SEM images of nickel hydroxide and magnesium hydroxide products obtained in the embodiment are shown in FIG. Figure 2 .

[0043] Example 2

[0044] (1) Pretreatment: A waste metal catalyst raw material (mass percentage of Bi is 1.8%, Fe is 2.8%, Mg is 0.9%, Mo is 22%, Ni is 7%, and Si is 24%) is put into a muffle furnace, and the roasting temperature is 550°C and the roasting time is 4 hours to obtain material I.

[0045] Alkali Leaching: Material I was leached with 3 mol / L sodium hydroxide at 90°C for 2 h, followed by solid-liquid separation to obtain filtrate I and residue I. The concentrations of Bi, Fe, Mg, Mo, and Ni in filtrate I were measured using an inductively coupled plasma optical emission spectrometer (ICP, Varian, 725-ES). The leaching rate is defined as the metal content in the filtrate divided by the total mass of the metal in the raw material. Based on the ICP results, the leaching rate for Mo was 95.8%, the leaching rate for Si was 58.1%, and the leaching rates for Bi, Fe, Mg, and Ni were all 0%.

[0046] (2)-(5) are the same as in Example 1.

[0047] Example 3

[0048] (1) Pretreatment: A waste metal catalyst raw material (mass percentage of Bi is 1.8%, Fe is 2.8%, Mg is 0.9%, Mo is 22%, Ni is 7%, and Si is 24%) is put into a muffle furnace, and the roasting temperature is 550°C and the roasting time is 4 hours to obtain material I.

[0049] Alkali Leaching: Material I was leached with 3 mol / L sodium hydroxide at 90°C for 2 h, followed by solid-liquid separation to obtain filtrate I and residue I. The concentrations of Bi, Fe, Mg, Mo, and Ni in filtrate I were measured using an inductively coupled plasma optical emission spectrometer (ICP, Varian, 725-ES). The leaching rate is defined as the metal content in the filtrate divided by the total mass of the metal in the raw material. Based on the ICP results, the leaching rate for Mo was 95.8%, the leaching rate for Si was 58.1%, and the leaching rates for Bi, Fe, Mg, and Ni were all 0%.

[0050] (2) Ion exchange: Filtrate I is passed through 732 hydrogen type cation exchange resin to obtain exchange liquid II, and exchange liquid II is evaporated and crystallized to obtain molybdosilicic acid product.

[0051] (3) Acid leaching: The filter residue I was leached with 9 mol / L nitric acid at 90°C for 30 min, and the solid-liquid separation was performed to obtain filtrate II and filter residue II. The filter residue II was dried to obtain the silica product. The ICP analysis results of the filtrate II showed that the leaching rates of Bi were 98.1%, Fe were 94%, Mg were 100%, Ni were 100%, Mo were 99.8%, and Si were 4.5%.

[0052] (4)-(5) are the same as in Example 1.

[0053] Example 4

[0054] (1) Pretreatment: A waste metal catalyst raw material (mass percentage of Bi is 1.8%, Fe is 2.8%, Mg is 0.9%, Mo is 22%, Ni is 7%, and Si is 24%) is put into a muffle furnace, and the roasting temperature is 550°C and the roasting time is 4 hours to obtain material I.

[0055] Alkali Leaching: Material I was leached with 4 mol / L sodium hydroxide at 120°C for 1 hour, followed by solid-liquid separation to obtain filtrate I and residue I. The concentrations of Bi, Fe, Mg, Mo, and Ni in filtrate I were measured using an inductively coupled plasma optical emission spectrometer (ICP, Varian, 725-ES). The leaching rate is defined as the metal content in the filtrate divided by the total mass of the metal in the raw material. Based on the ICP results, the leaching rate of Mo was calculated to be 99.6%, the leaching rate of Si was 65.5%, and the leaching rates of Bi, Fe, Mg, and Ni were all 0%.

[0056] (2) Ion exchange: Filtrate I is passed through 732 hydrogen type cation exchange resin to obtain exchange liquid II, and exchange liquid II is evaporated and crystallized to obtain molybdosilicic acid product.

[0057] (3) Acid leaching: The filter residue I was leached with 3 mol / L nitric acid at 90°C for 1 h, and the solid-liquid separation was performed to obtain filtrate II and filter residue II. The filter residue II was dried to obtain the silica product. The ICP analysis results of the filtrate II showed that the leaching rates of Bi were 97%, Fe were 92%, Mg were 100%, Ni were 99.7%, Mo were 94.5%, and Si were 0%.

[0058] (4) Extraction and back-extraction: P507 was used to extract Mo and Fe from the filtrate II. The extraction conditions were: reaction time 40 min, extractant concentration 30 vol.%, aqueous phase / organic phase volume ratio (A / O) 1:1, reaction temperature 25 °C, and Mo and Fe extraction rates of 99.1% and 98%, respectively. Extract III and raffinate III were obtained. Extract III was back-extracted with Fe using 4 mol / L hydrochloric acid, and then with 1 mol / L ammonia water + 1 mol / L ammonium chloride to back-extract Mo. After post-treatment, products containing Fe and Mo were obtained, respectively. The extractant was acid-washed and reused.

[0059] (5) Same as Example 1.

[0060] Example 5

[0061] (1) Pretreatment: A waste metal catalyst raw material (mass percentage of Bi is 1.8%, Fe is 2.8%, Mg is 0.9%, Mo is 22%, Ni is 7%, and Si is 24%) is put into a muffle furnace, and the roasting temperature is 550°C and the roasting time is 4 hours to obtain material I.

[0062] Alkali Leaching: Material I was leached with 9 mol / L sodium hydroxide at 160°C for 2 h, followed by solid-liquid separation to obtain filtrate I and residue I. The concentrations of Bi, Fe, Mg, Mo, and Ni in filtrate I were measured using an inductively coupled plasma optical emission spectrometer (ICP, Varian, 725-ES). The leaching rate is defined as the metal content in the filtrate divided by the total mass of the metal in the raw material. Based on the ICP results, the leaching rate for Mo was calculated to be 99.9%, the leaching rate for Si was 70%, and the leaching rates for Bi, Fe, Mg, and Ni were 5.8%, 5%, 8%, and 4.5%, respectively.

[0063] (2)-(5) are the same as in Example 1.

[0064] Example 6

[0065] (1) Pretreatment: A waste metal catalyst raw material (mass percentage of Bi is 1.8%, Fe is 2.8%, Mg is 0.9%, Mo is 22%, Ni is 7%, and Si is 24%) is put into a muffle furnace, and the roasting temperature is 550°C and the roasting time is 4 hours to obtain material I.

[0066] Alkali Leaching: Material I was leached with 4 mol / L sodium hydroxide at 120°C for 1 hour, followed by solid-liquid separation to obtain filtrate I and residue I. The concentrations of Bi, Fe, Mg, Mo, and Ni in filtrate I were measured using an inductively coupled plasma optical emission spectrometer (ICP, Varian, 725-ES). The leaching rate is defined as the metal content in the filtrate divided by the total mass of the metal in the raw material. Based on the ICP results, the leaching rate of Mo was calculated to be 99.6%, the leaching rate of Si was 65.5%, and the leaching rates of Bi, Fe, Mg, and Ni were all 0%.

[0067] (2) Ion exchange: Filtrate I is passed through 732 hydrogen type cation exchange resin to obtain exchange liquid II, and exchange liquid II is evaporated and crystallized to obtain molybdosilicic acid product.

[0068] (3) Acid leaching: The filter residue I was leached with 3 mol / L nitric acid at 90°C for 1 h, and the solid-liquid separation was performed to obtain filtrate II and filter residue II. The filter residue II was dried to obtain the silica product. The ICP analysis results of the filtrate II showed that the leaching rates of Bi were 97%, Fe were 92%, Mg were 100%, Ni were 99.7%, Mo were 94.5%, and Si were 0%.

[0069] (4) Extraction and back-extraction: Mo and Fe were extracted from the filtrate II using Cyanex272, wherein the extraction conditions were a reaction time of 2 h, an extractant concentration of 30 vol.%, an aqueous phase / organic phase volume ratio (A / O) of 0.5:1, a reaction temperature of 30°C, and the extraction rates of Mo and Fe were 99.9% and 99.4%, respectively, to obtain extract III and raffinate III. The extract III was back-extracted with Fe using 4 mol / L hydrochloric acid, and then with 1 mol / L ammonia water + 1 mol / L ammonium chloride to back-extract Mo. After post-treatment, products containing Fe and Mo were obtained, respectively; the extractant was acid-washed and reused.

[0070] (5) Same as Example 1.

[0071] Comparative Example 1

[0072] (1) Pretreatment: A waste metal catalyst raw material (mass percentage of Bi is 1.8%, Fe is 2.8%, Mg is 0.9%, Mo is 22%, Ni is 7%, and Si is 24%) is put into a muffle furnace, and the roasting temperature is 550°C and the roasting time is 4 hours to obtain material I.

[0073] (2) Acid leaching: The material I obtained in step (1) was leached with 3 mol / L nitric acid at 90°C for 1 h, and the solid-liquid separation was performed to obtain a filtrate I and a filter residue I. The concentrations of Bi, Fe, Mg, Mo, and Ni in the filtrate I were measured using an inductively coupled plasma emission spectrometer (ICP, Varian, 725-ES). The leaching rate is defined as the metal content in the filtrate divided by the total mass of the metal in the raw material. According to the ICP results, the leaching rates of Bi, Fe, Mg, Mo, and Ni were calculated to be 95.1%, 98.7%, 99.5%, 94.6%, and 99.2%, respectively. The purpose of highly selective leaching was not achieved, and corresponding separation methods had to be taken to obtain the product subsequently, which increased the processing cost.

[0074] Comparative Example 2

[0075] (1) Pretreatment: A waste metal catalyst raw material (mass percentage of Bi is 1.8%, Fe is 2.8%, Mg is 0.9%, Mo is 22%, Ni is 7%, and Si is 24%) is put into a muffle furnace, and the roasting temperature is 550°C and the roasting time is 4 hours to obtain material I.

[0076] Alkali leaching: The material I obtained in step (1) was leached with 3 mol / L ammonia water at 90°C for 2 h, and solid-liquid separation was performed to obtain filtrate I and residue I. The concentrations of Bi, Fe, Mg, Mo, and Ni in filtrate I were measured using an inductively coupled plasma emission spectrometer (ICP, Varian, 725-ES). The leaching rate is defined as the metal content in the filtrate divided by the total mass of the metal in the raw material. Based on the ICP results, the leaching rates of Bi, Fe, Mg, Mo, and Ni were calculated to be 15%, 13%, 15.5%, 90%, and 85.1%, respectively. The purpose of highly selective leaching was not achieved, and subsequent separation measures had to be taken to obtain the product, increasing the processing cost.

[0077] Comparative Example 3

[0078] (1) Pretreatment: A waste metal catalyst raw material (mass percentage of Bi is 1.8%, Fe is 2.8%, Mg is 0.9%, Mo is 22%, Ni is 7%, and Si is 24%) is put into a muffle furnace, and the roasting temperature is 550°C and the roasting time is 4 hours to obtain material I.

[0079] Alkali Leaching: Material I was leached with 3 mol / L sodium hydroxide at 90°C for 2 h, followed by solid-liquid separation to obtain filtrate I and residue I. The concentrations of Bi, Fe, Mg, Mo, and Ni in filtrate I were measured using an inductively coupled plasma optical emission spectrometer (ICP, Varian, 725-ES). The leaching rate is defined as the metal content in the filtrate divided by the total mass of the metal in the raw material. Based on the ICP results, the leaching rate for Mo was 95.8%, the leaching rate for Si was 58.1%, and the leaching rates for Bi, Fe, Mg, and Ni were all 0%.

[0080] (2) Ion exchange: Filtrate I is passed through 732 hydrogen type cation exchange resin to obtain exchange liquid II, and exchange liquid II is evaporated and crystallized to obtain molybdosilicic acid product.

[0081] (3) Acid leaching: The filter residue I was leached with 3 mol / L nitric acid at 90°C for 1 h, and the solid-liquid separation was performed to obtain filtrate II and filter residue II. The filter residue II was dried to obtain the silica product. The ICP analysis results of the filtrate II showed that the leaching rates of Bi were 97%, Fe were 92%, Mg were 100%, Ni were 99.7%, Mo were 94.5%, and Si were 0%.

[0082] (4) Extraction and back extraction: Filtrate II was extracted with TBP. The extraction conditions were: reaction time 40 min, extractant concentration 30 vol.%, aqueous phase / organic phase volume ratio (A / O) 1:1, reaction temperature 25°C, and the extraction rates of Bi, Fe, Mg, Mo, and Ni were all 0%, indicating that the metals could not be separated.

[0083] Comparative Example 4

[0084] (1) Pretreatment: A waste metal catalyst raw material (mass percentage of Bi is 1.8%, Fe is 2.8%, Mg is 0.9%, Mo is 22%, Ni is 7%, and Si is 24%) is put into a muffle furnace, and the roasting temperature is 550°C and the roasting time is 4 hours to obtain material I.

[0085] Alkali Leaching: Material I was leached with 0.1 mol / L sodium hydroxide at 90°C for 2 hours. Solid-liquid separation was then performed to obtain filtrate I and residue I. The concentrations of Bi, Fe, Mg, Mo, and Ni in filtrate I were measured using an inductively coupled plasma optical emission spectrometer (ICP, Varian, 725-ES). The leaching rate is defined as the metal content in the filtrate divided by the total mass of metal in the raw material. Based on the ICP results, the leaching rate for Mo was 5.2%, the leaching rate for Si was 2%, and the leaching rates for Bi, Fe, Mg, and Ni were all 0%. Due to the low leaching rate, the recovery of valuable elements could not be achieved.

Claims

1. A method for recovering valuable elements from waste metal catalysts, comprising the following steps: (1) Alkali leaching: Alkali leaching of pretreated waste acrylonitrile catalyst, solid-liquid separation, and obtaining filtrate I and filter residue I; (2) Ion exchange: The filtrate I obtained in step (1) is subjected to ion exchange to obtain exchange solution II, and the exchange solution II is crystallized to obtain molybdosilicic acid product; (3) Acid leaching: The filter residue I obtained in step (1) is subjected to acid leaching, and solid-liquid separation is performed to obtain filtrate II and filter residue II. The filter residue II is dried to obtain the Si-containing product; (4) Extraction and stripping: Mo and Fe are extracted from the filtrate II obtained in step (3) to obtain extract III and raffinate III. The extract III is stripped in steps and post-treated to obtain Fe-containing and Mo-containing products, respectively; (5) Precipitation: Add a precipitant to the raffinate III obtained in step (4), and sequentially recover Bi, Ni, and Mg under different precipitation conditions; The waste acrylonitrile catalyst comprises a metal active element composite oxide and a carrier, wherein the carrier is silicon dioxide, and the metal active elements comprise Mo, Fe, Bi, Ni, and Mg.

2. The method according to claim 1, characterized in that The composition of the waste acrylonitrile catalyst in step (1), based on the mass of the catalyst, includes: a Bi content of 0.1% to 10%, a Fe content of 0.1% to 10%, a Mg content of 0.1% to 10%, a Mo content of 0.1% to 40%, a Ni content of 0.1% to 20%, and a Si content of 1% to 40%.

3. The method according to claim 1, characterized in that The operating conditions of the pretreatment in step (1) are: calcination at a temperature of 400°C to 800°C for 2 h to 10 h.

4. The method according to claim 1, wherein In step (1), the concentration of the alkaline leaching agent is 0.5 mol / L~10 mol / L, the reaction temperature is 50℃~200℃, and the reaction time is 0.5h~48h.

5. The method according to claim 1, wherein In step (1), the concentration of the alkaline leaching agent is 3 mol / L~10 mol / L, the reaction temperature is 80℃~200℃, and the reaction time is 1 h~3 h.

6. The method according to claim 1, characterized in that In the ion exchange process described in step (2), hydrogen-type cation exchange resin is used for exchange, and Na ions are exchanged onto the resin to obtain exchange liquid II, and the exchange liquid II is evaporated and crystallized to obtain the molybdosilicic acid product.

7. The method according to claim 1, characterized in that Step (3) H of acidic leaching agent + The concentration is 1.5 mol / L~10 mol / L, the reaction temperature is 50 ℃~200 ℃, and the reaction time is 0.5 h~48 h.

8. The method according to claim 1, characterized in that An organic acidic extractant is used in the extraction described in step (4).

9. The method according to claim 1, characterized in that The extraction conditions of step (4) are as follows: reaction time 10 min~24 h, extractant concentration 10 vol.%~30 vol.%, aqueous phase / organic phase volume ratio (A / O) 0.1:1~2:1, and reaction temperature 0 °C~60 °C.

10. The method according to claim 1, characterized in that The specific operation of the stepwise stripping described in step (4) is as follows: first, Fe is stripped with acid, and then Mo is stripped with alkali, and the extractant is acid-washed and reused; wherein the acid used is one or more of hydrochloric acid, sulfuric acid, and oxalic acid with a concentration of 2 mol / L to 4 mol / L; the alkali used is NH4 + The alkaline solution with a concentration of 1 mol / L to 10 mol / L is selected from one or more of ammonium sulfate, ammonium chloride, ammonium nitrate, ammonium carbonate, ammonium bicarbonate, and ammonia water.

11. The method according to claim 1, wherein The raffinate III described in step (5) is added with a precipitant, wherein the precipitant is selected from at least one of sodium hydroxide and potassium hydroxide.

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