Method for smelting and enriching platinum group metal by using industrial scrap iron and waste automobile exhaust catalyst

Abstract

The invention discloses a method for smelting and enriching platinum group metals by using industrial scrap iron and a waste automobile exhaust catalyst, and relates to the technical field of solid waste resource recovery and metallurgy. The method for smelting and enriching the platinum group metal comprises the following steps: uniformly mixing a waste automobile exhaust catalyst, a slag former, a reducing agent and industrial scrap iron, and smelting at high temperature to obtain an alloy phase containing the platinum group metal and a slag phase. According to the method for smelting and enriching the platinum group metal, the industrial scrap iron replaces a conventional elemental iron trapping agent, the production cost is saved, FeO which is not reduced in the industrial scrap iron enters the slag, the fluidity of the slag can be promoted, slag-metal separation is facilitated, diboron trioxide is added into the slagging constituent, and the slag-metal separation efficiency is improved. And the mass ratio of CaO to SiO2 in the slag and the mass fraction of magnesium oxide are controlled, so that the recovery rates of platinum, palladium and rhodium are all greater than 98%, and the content of harmful metals is far lower than the environmental protection industry standard of the People's Republic of China.

Description

Technical Field

[0001] The invention relates to the field of solid waste resource recovery and metallurgical technology, and in particular to a method for smelting and enriching platinum group metals from industrial waste iron filings and waste automobile exhaust catalysts. Background Art

[0002] Platinum group metals (platinum, palladium, rhodium) are widely used in the industrial field because of their excellent physical and chemical properties (good electrical conductivity, chemical stability and catalytic activity, etc.), especially as an important component of catalysts. The natural resource content of platinum group metals is extremely small, and the cost of mining and refining is relatively high. Therefore, it is necessary to develop a recycling process for platinum group metals. Automobile exhaust catalysts are an important use of platinum group metals. After exceeding the service life, platinum group metals adhere to the surface of the carrier. According to statistics, the content of platinum group metals in waste automobile exhaust catalysts is 2000g / t, which is much higher than the content in platinum group metal co-existing ores (0.8g / t). At the same time, waste automobile exhaust catalysts contain a large amount of harmful heavy metals and are classified as solid waste. Random placement will not only waste a lot of land resources, but also cause serious harm to the environment. Therefore, it is necessary to explore efficient and harmless recovery of platinum group metals. This is of great significance to both the economy and the environment.

[0003] At present, the processes for recovering platinum group metals from waste automobile exhaust catalysts can be mainly divided into two categories: pyrometallurgical recovery and wet recovery. Wet recovery has high requirements for raw materials, cumbersome processes, and large material requirements, and is not suitable for large-scale production. Pyrometallurgical recovery does not require high raw material quality and can be applied to large-scale production. The most important method in the pyrometallurgical process is metal capture.

[0004] Copper capture has the advantage of low energy consumption, but the subsequent separation process is cumbersome and costly. The high smelting temperature required for iron capture can easily reduce SiO2 in waste automobile exhaust catalysts and form insoluble ferrosilicon alloys with iron. Harmful heavy metals in waste automobile exhaust catalysts still remain in the slag, posing a risk of environmental pollution. In addition, large amounts of metals as capture agents also have high costs. Summary of the invention

[0005] The present invention aims at the deficiencies of the prior art and provides a low-cost and environmentally friendly method for recovering platinum group metals from waste automobile exhaust catalysts.

[0006] To this end, the present invention provides a method for smelting and enriching platinum group metals from industrial waste iron scraps and waste automobile exhaust catalysts, comprising: The waste automobile exhaust catalyst, slag-making agent, reducing agent and industrial waste iron filings are uniformly mixed and smelted to obtain an alloy phase and a slag phase containing platinum group metals; The slag-forming agent is calcium oxide, silicon dioxide, magnesium oxide and boron trioxide; the mass ratio of calcium oxide to silicon dioxide in the slag phase is controlled to be (0.75-0.9):1, the mass fraction of magnesium oxide is 5%-8%, and the mass fraction of boron trioxide is 4%-8%.

[0007] Furthermore, the mass ratio of the waste automobile exhaust catalyst, the slag-forming agent, the reducing agent and the industrial waste iron filings is 100: (200-350): (4-6): (8-15).

[0008] Furthermore, the smelting temperature is 1400°C to 1600°C, and the smelting time is 30min to 60min.

[0009] Furthermore, the components of the waste automobile exhaust catalyst include: silicon dioxide, aluminum oxide, magnesium oxide and platinum group metals; Among them, the waste automobile exhaust catalyst contains, by mass fraction, 25% to 35% silicon dioxide, 30% to 45% aluminum oxide, and 7% to 10% magnesium oxide; among the platinum group metals, the platinum content is 300ppm to 600ppm, the palladium content is 1800ppm to 3300ppm, and the rhodium content is 150ppm to 320ppm.

[0010] Furthermore, the reducing agent is carbon powder.

[0011] Furthermore, the particle size of the industrial scrap iron is less than 500 μm.

[0012] By adopting the above-mentioned method of smelting and enriching platinum group metals using industrial waste iron filings and waste automobile exhaust catalysts, the platinum recovery rate is greater than 98%, the palladium recovery rate is greater than 98%, and the rhodium recovery rate is greater than 98%. The obtained slag is subjected to toxicity leaching test by acetic acid buffer solution method, and the harmful metal content is far lower than the environmental protection industry standard of the People's Republic of China.

[0013] Compared with the prior art, the present invention has at least the following beneficial effects: The method for smelting and enriching platinum group metals provided by the present invention replaces the conventional elemental iron collector with industrial scrap iron, which not only saves production costs, but also the unreduced FeO in the industrial scrap iron enters the slag, which promotes the fluidity of the slag and is beneficial to the separation of slag and gold. In addition, by adding boron trioxide to the slag-making agent and controlling the mass ratio of CaO and SiO2 and the mass fraction of magnesium oxide in the slag, the recovery rates of platinum, palladium and rhodium are all greater than 98%, and the content of harmful metals is far lower than the environmental protection industry standard of the People's Republic of China. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the embodiments of the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0015] Figure 1 A flow chart of a method for smelting and enriching platinum group metals from industrial scrap iron and waste automobile exhaust catalysts provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0016] In order to better understand the above-mentioned technical scheme, the technical scheme of the embodiments of the present application is described in detail below through the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present application and the specific features in the embodiments are detailed descriptions of the technical scheme of the embodiments of the present application, rather than limitations on the technical scheme of the present application. In the absence of conflict, the embodiments of the present application and the technical features in the embodiments may be combined with each other.

[0017] The embodiment of the present invention provides a method for smelting and enriching platinum group metals with industrial scrap iron and waste automobile exhaust catalyst, comprising: uniformly mixing waste automobile exhaust catalyst, slag-forming agent, reducing agent and industrial scrap iron, and smelting at high temperature to obtain an alloy phase and a slag phase containing platinum group metals.

[0018] The method for smelting and enriching platinum group metals with industrial scrap iron and waste automobile exhaust catalyst provided in an embodiment of the present invention not only saves production costs by replacing conventional elemental iron collectors with industrial scrap iron, but also the unreduced FeO in the industrial scrap iron enters the slag, which will promote the fluidity of the slag and facilitate the separation of slag and gold. Optionally, the evenly mixed materials are placed in a crucible, and the crucible is placed in a medium frequency induction furnace for capture and smelting. After high-temperature smelting, the melt is poured into a prepared container, and the alloy phase containing platinum group metals and the slag phase are separated under the action of gravity, and the alloy phase settles at the bottom of the melt.

[0019] In some embodiments, the slag forming agent is calcium oxide, silicon dioxide, magnesium oxide and boron trioxide, wherein the source of the boron trioxide can be boric acid.

[0020] Specifically, the ferrous oxide in the industrial scrap iron that is not reduced by the reducing agent, together with the aluminum oxide, silicon dioxide and magnesium oxide contained in the slag-making agent and the waste automobile exhaust catalyst, constitutes the CaO-SiO2-Al2O3-MgO-B2O3-FeO hexavalent slag system. This slag system can not only effectively reduce the smelting temperature and reduce energy consumption, but also more easily generate glass slag that can effectively encapsulate harmful heavy metals in the waste automobile exhaust catalyst, wherein FeO and B2O3 can effectively reduce the melting point and viscosity of the slag, thereby reducing the operating temperature of the heating equipment and reducing energy consumption. In addition, B2O3 can form a network structure with silicate, enhance the amorphous structure of the glass, inhibit the formation of crystals, thereby increasing the degree of vitrification of the glass, and has a promoting effect on encapsulating heavy metals in the melt.

[0021] In some embodiments, the mass ratio of calcium oxide to silicon dioxide in the slag phase is controlled to be (0.75-0.9):1, the mass fraction of magnesium oxide is 5%-8%, and the mass fraction of boron trioxide is 4%-8%.

[0022] By adjusting the calcium-silicon mass ratio of the slag, the mass fraction of magnesium oxide and adding boron trioxide as a glass former, the final slag becomes amorphous glass slag. Glass slag can encapsulate harmful substances in waste automobile exhaust catalysts in the slag and make them difficult to leach, thereby reducing the harm to the environment. In addition, boron trioxide can reduce the capture temperature of smelting, further improve the fluidity of the slag, and improve the capture efficiency.

[0023] In some embodiments, the mass ratio of waste automobile exhaust catalyst, slag-forming agent, reducing agent and industrial waste iron filings is 100: (200-350): (4-6): (8-15).

[0024] In some embodiments, the melting temperature is 1400°C to 1600°C, and the melting time is 30 min to 60 min. Preferably, the melting temperature is 1500°C ± 20°C, and the melting time is 40 min to 50 min.

[0025] Specifically, if the smelting temperature is lower than 1400°C, it will affect the fluidity of the slag, making it difficult for platinum group metals to be captured in the melt with poor fluidity, affecting the recovery efficiency. If the smelting temperature is higher than 1600°C, the silicon in the melt will be reduced and the iron used as the capture agent will form an insoluble ferrosilicon alloy, which will cause great difficulties for the subsequent separation operation of platinum group metals. If the smelting time is too short, less than 30 minutes, the platinum group metals will not have enough time to form alloy particles with the capture metal and settle to the bottom of the melt, causing them to remain in the melt, affecting the recovery rate of platinum group metals. If the smelting time is too long, greater than 60 minutes, it will affect the service life of the equipment and consume a lot of heat energy, wasting resources. Moreover, on an industrial scale, the common operating temperature range of iron capture and recovery of platinum group metals is 1600°C~2000°C, and this application significantly reduces the smelting temperature.

[0026] In some embodiments, the components of the waste automobile exhaust catalyst include: silicon dioxide, aluminum oxide, magnesium oxide and platinum group metals; wherein, the waste automobile exhaust catalyst contains 25% to 35% silicon dioxide, 30% to 45% aluminum oxide, and 7% to 10% magnesium oxide by mass fraction; among the platinum group metals, the platinum content is 300ppm to 600ppm, the palladium content is 1800ppm to 3300ppm, and the rhodium content is 150ppm to 320ppm.

[0027] In some embodiments, the reducing agent is carbon powder.

[0028] Specifically, the reducing agent carbon powder can not only effectively reduce the oxides of platinum group metals in waste automobile exhaust catalysts to metallic state, improve the recovery efficiency and purity, but also reduce part of the iron oxides in iron filings to elemental iron, ultimately achieving the purpose of efficient and energy-saving recovery. Common reducing agents include H2 and CO. Compared with CO, the use of H2 is somewhat dangerous and may explode if improperly operated. Therefore, carbon powder is selected as the reducing agent to generate CO.

[0029] In some embodiments, the particle size of the industrial scrap iron is less than 500 μm.

[0030] It is understandable that during the smelting process, the larger the contact area of ​​the collector in the melt, the easier it is for the collector metal to capture the platinum group metals. Therefore, the particle size of the iron filings should be controlled to have a larger specific surface area, which means that with the same mass of the collector, more surface is used to contact the platinum group metals in the melt, thereby promoting the recovery process.

[0031] In summary, by adopting the above-mentioned method for smelting and enriching platinum group metals with industrial waste iron filings and waste automobile exhaust catalysts, the recovery rate of platinum is greater than 98%, the recovery rate of palladium is greater than 98%, and the recovery rate of rhodium is greater than 98%. The toxicity leaching test of the obtained slag is carried out by the acetic acid buffer solution method (HJ / T 300-2007), and the content of harmful metals is far lower than the environmental protection industry standard of the People's Republic of China (GB 5085.3-2007).

[0032] Example 1 A method for smelting and enriching platinum group metals from industrial scrap iron and waste automobile exhaust catalysts like Figure 1 As shown, the following steps are included: (1) Ingredients The waste automobile exhaust catalyst (the main components are shown in Table 1) was crushed and ground, and then 100g was weighed and mixed evenly with 96g SiO2, 99g CaO, 10g MgO, 32g boric acid, 10g iron filings and 5g carbon powder, and put into a graphite crucible.

[0033] Table 1 Main components of a waste automobile exhaust catalyst

[0034] (2) Capture and smelting The graphite crucible was placed in a medium frequency induction furnace and heated at 10°C / min under air conditions. After heating to 1500°C, the temperature was maintained for 40 minutes. After the temperature was maintained, the melt was poured into a pre-prepared mold. The platinum group metals entered the metal phase, and the alloy phase and the slag phase were separated under the action of gravity. The alloy phase settled at the bottom of the melt to obtain the ferroalloy and slag (the main components are shown in Table 2).

[0035] Table 2 Main components of slag

[0036] In this embodiment, the slag CaO / SiO2 is about 0.80, the Pt recovery rate is 99.4%, the Pd recovery rate is 99.7%, and the Rh recovery rate is 99.2%.

[0037] (3) Toxicity test The obtained slag was sampled, ground into fine powder, and subjected to toxicity leaching test by acetic acid dissolution method (the results are shown in Table 3).

[0038] Table 3 Toxicity test results

[0039] Example 2 A method for smelting and enriching platinum group metals from industrial scrap iron and waste automobile exhaust catalysts like Figure 1 As shown, the following steps are included: (1) Ingredients The waste automobile exhaust catalyst (the main components are shown in Table 4) was crushed and ground, and then 100g was weighed and mixed with 140g SiO2, 155g CaO, 24g MgO, 22g boric acid, 10g iron filings and 5g carbon powder, and put into a graphite crucible.

[0040] Table 4 Main components of a waste automobile exhaust catalyst

[0041] (2) Capture and smelting The graphite crucible was placed in a medium frequency induction furnace and heated at 10°C / min under air conditions. After heating to 1600°C, the temperature was kept for 50 minutes. After the temperature was kept, the melt was poured into a pre-prepared mold. The platinum group metals entered the metal phase, and the alloy phase and the slag phase were separated under the action of gravity. The alloy phase settled at the bottom of the melt to obtain the ferroalloy and slag (the main components are shown in Table 5).

[0042] Table 5 Main components of slag

[0043] In this embodiment, the slag CaO / SiO2 is about 0.9, the Pt recovery rate is 98.8%, the Pd recovery rate is 99.5%, and the Rh recovery rate is 98.2%.

[0044] (3) Toxicity test The obtained slag was sampled, ground into fine powder, and subjected to toxicity leaching test by acetic acid dissolution method (the results are shown in Table 6).

[0045] Table 6 Toxicity test results

[0046] Example 3 like Figure 1 As shown, the following steps are included: (1) Ingredients The waste automobile exhaust catalyst (the main components are shown in Table 7) was crushed and ground, and then 100g was weighed and mixed with 105g SiO2, 105g CaO, 7g MgO, 36g boric acid, 10g iron filings and 5g carbon powder, and put into a graphite crucible.

[0047] Table 7 Main components of a waste automobile exhaust catalyst

[0048] (2) Capture and smelting The graphite crucible was placed in a medium frequency induction furnace and heated at 10°C / min under air conditions. After heating to 1500°C, the temperature was kept for 60 minutes. After the temperature was kept, the melt was poured into a pre-prepared mold. The platinum group metals entered the metal phase, and the alloy phase and the slag phase were separated under the action of gravity. The alloy phase settled at the bottom of the melt to obtain the ferroalloy and slag (the main components are shown in Table 8).

[0049] Table 8 Main components of slag

[0050] In this embodiment, the slag CaO / SiO2 is about 0.76, the Pt recovery rate is 99.1%, the Pd recovery rate is 99.6%, and the Rh recovery rate is 98.7%.

[0051] (3) Toxicity test The obtained slag was sampled, ground into fine powder, and subjected to toxicity leaching test by acetic acid dissolution method (the results are shown in Table 9).

[0052] Table 9 Toxicity test results

[0053] Example 4 like Figure 1 As shown, the following steps are included: (1) Ingredients The waste automobile exhaust catalyst (the main components are shown in Table 10) was crushed and ground, and then 100g was weighed and mixed evenly with 91g SiO2, 98g CaO, 8.3g MgO, 43g boric acid, 10g iron filings and 5g carbon powder, and put into a graphite crucible.

[0054] Table 10 Main components of a waste automobile exhaust catalyst

[0055] (2) Capture and smelting The graphite crucible was placed in a medium frequency induction furnace and heated at 10°C / min under air conditions. After heating to 1400°C, the temperature was kept at that temperature for 30 minutes. After the temperature was kept at that temperature, the melt was poured into a pre-prepared mold. The platinum group metals entered the metal phase, and the alloy phase and the slag phase were separated under the action of gravity. The alloy phase settled at the bottom of the melt to obtain the ferroalloy and slag (the main components are shown in Table 11).

[0056] Table 11 Main components of slag

[0057] In this embodiment, the slag CaO / SiO2 is about 0.77, the Pt recovery rate is 99.3%, the Pd recovery rate is 99.7%, and the Rh recovery rate is 98.9%.

[0058] (3) Toxicity test The obtained slag was sampled, ground into fine powder, and subjected to toxicity leaching test by acetic acid dissolution method (the results are shown in Table 12).

[0059] Table 12 Toxicity test results

[0060] Example 5 like Figure 1 As shown, the following steps are included: (1) Ingredients The waste automobile exhaust catalyst (the main components are shown in Table 13) was crushed and ground, and then 100g was weighed and mixed with 124g SiO2, 130g CaO, 22g MgO, 27g boric acid, 10g iron filings and 5g carbon powder, and put into a graphite crucible.

[0061] Table 13 Main components of a waste automobile exhaust catalyst

[0062] (2) Capture and smelting The graphite crucible was placed in a medium frequency induction furnace and heated at 10°C / min under air conditions. After heating to 1500°C, the temperature was kept at that temperature for 40 minutes. After the temperature was kept at that temperature, the melt was poured into a pre-prepared mold. The platinum group metals entered the metal phase, and the alloy phase and the slag phase were separated under the action of gravity. The alloy phase settled at the bottom of the melt to obtain the ferroalloy and slag (the main components are shown in Table 14).

[0063] Table 14 Main components of slag

[0064] In this embodiment, the slag CaO / SiO2 is about 0.87, the Pt recovery rate is 99.3%, the Pd recovery rate is 99.8%, and the Rh recovery rate is 99.3%.

[0065] (3) Toxicity test The obtained slag was sampled, ground into fine powder, and subjected to toxicity leaching test by acetic acid dissolution method (the results are shown in Table 18).

[0066] Table 15 Toxicity test results

[0067] Comparative Example 1 (1) Ingredients The waste automobile exhaust catalyst (the main components are shown in Table 16) was crushed and ground, and then 100g was weighed and mixed evenly with 96g SiO2, 99g CaO, 10g MgO, 32g boric acid, 10g iron filings and 5g carbon powder, and put into a graphite crucible.

[0068] Table 16 Main components of a waste automobile exhaust catalyst

[0069] (2) Capture and smelting The graphite crucible was placed in a medium frequency induction furnace and heated at 10°C / min under air conditions. After heating to 1500°C, the temperature was kept for 10 minutes. After the temperature was kept, the melt was poured into a pre-prepared mold. The platinum group metals entered the metal phase, and the alloy phase and the slag phase were separated under the action of gravity. The alloy phase settled at the bottom of the melt to obtain the ferroalloy and slag (the main components are shown in Table 17).

[0070] Table 17 Main components of slag

[0071] In this embodiment, the slag CaO / SiO2 is about 0.79, the Pt recovery rate is 85.4%, the Pd recovery rate is 86.2%, and the Rh recovery rate is 85.1%.

[0072] (3) Toxicity test The obtained slag was sampled, ground into fine powder, and subjected to toxicity leaching test by acetic acid dissolution method (the results are shown in Table 18).

[0073] Table 18 Toxicity test results

[0074] Comparative Example 2 1) Ingredients The waste automobile exhaust catalyst (the main components are shown in Table 19) was crushed and ground, and then 100g was weighed and mixed with 136g SiO2, 80g CaO, 10g MgO, 32g boric acid, 10g iron filings and 5g carbon powder, and put into a graphite crucible.

[0075] Table 19 Main components of a waste automobile exhaust catalyst

[0076] (2) Capture and smelting The graphite crucible was placed in a medium frequency induction furnace and heated at 10°C / min under air conditions. After heating to 1500°C, the temperature was maintained for 40 minutes. After the temperature was maintained, the melt was poured into a pre-prepared mold. The platinum group metals entered the metal phase, and the alloy phase and the slag phase were separated under the action of gravity. The alloy phase settled at the bottom of the melt to obtain the ferroalloy and slag (the main components are shown in Table 20).

[0077] Table 20 Main components of slag

[0078] In this embodiment, the slag CaO / SiO2 is about 0.49, the Pt recovery rate is 88.3%, the Pd recovery rate is 87.6%, and the Rh recovery rate is 81.4%.

[0079] (3) Toxicity test The obtained slag was sampled, ground into fine powder, and subjected to toxicity leaching test by acetic acid dissolution method (the results are shown in Table 21).

[0080] Table 21 Toxicity test results

[0081] Comparative Example 3 1) Ingredients The waste automobile exhaust catalyst (the main components are shown in Table 22) was crushed and ground, and then 100g was weighed and mixed evenly with 96gSiO2, 99gCaO, 10gMgO, 32g boric acid, 10g iron filings and 5g carbon powder, and put into a graphite crucible.

[0082] Table 22 Main components of a waste automobile exhaust catalyst

[0083] (2) Capture and smelting The graphite crucible was placed in a medium frequency induction furnace and heated at 10°C / min under air conditions. After heating to 1300°C, the temperature was kept at that temperature for 40 minutes. After the temperature was kept at that temperature, the melt was poured into a pre-prepared mold. The platinum group metals entered the metal phase, and the alloy phase and the slag phase were separated under the action of gravity. The alloy phase settled at the bottom of the melt to obtain the ferroalloy and slag (the main components are shown in Table 23).

[0084] Table 23 Main components of slag

[0085] In this embodiment, the slag CaO / SiO2 is about 0.81, the Pt recovery rate is 82.6%, the Pd recovery rate is 83.8%, and the Rh recovery rate is 79.4%.

[0086] (3) Toxicity test The resulting slag was sampled, ground into fine powder, and subjected to toxicity leaching test by acetic acid dissolution method (the results are shown in Table 24).

[0087] Table 24 Toxicity test results

[0088] Comparative Example 4 (1) Ingredients The waste automobile exhaust catalyst (the main components are shown in Table 25) was crushed and ground, and then 100g was weighed and mixed with 118g SiO2, 115g CaO, 10g iron filings and 5g carbon powder, and put into a graphite crucible.

[0089] Table 25 Main components of a waste automobile exhaust catalyst

[0090] (2) Capture and smelting The graphite crucible was placed in a medium frequency induction furnace and heated at 10°C / min under air conditions. After heating to 1700°C, the temperature was kept at this temperature for 80 minutes. After the temperature was kept at this temperature, the melt was poured into a pre-prepared mold. The platinum group metals entered the metal phase, and the alloy phase and the slag phase were separated under the action of gravity. The alloy phase settled at the bottom of the melt to obtain the ferroalloy and slag (the main components are shown in Table 26).

[0091] Table 26 Main components of slag

[0092] In this embodiment, the slag CaO / SiO2 is about 0.8, the Pt recovery rate is 96.9%, the Pd recovery rate is 97.2%, and the Rh recovery rate is 95.8%.

[0093] (3) Toxicity test The resulting slag was sampled, ground into fine powder, and subjected to toxicity leaching test by acetic acid dissolution method (the results are shown in Table 27).

[0094] Table 27 Toxicity test results

[0095] Comparative Example 5 (1) Ingredients The waste automobile exhaust catalyst (the main components are shown in Table 28) was crushed and ground, and then 100g was weighed and mixed evenly with 96gSiO2, 99gCaO, 10gMgO, 32g boric acid, 10g reduced iron powder and 5g carbon powder, and put into a graphite crucible.

[0096] Table 28 Main components of a waste automobile exhaust catalyst

[0097] (2) Capture and smelting The graphite crucible was placed in a medium frequency induction furnace and heated at 10°C / min under air conditions. After heating to 1500°C, the temperature was maintained for 40 minutes. After the temperature was maintained, the melt was poured into a pre-prepared mold. The platinum group metals entered the metal phase, and the alloy phase and the slag phase were separated under the action of gravity. The alloy phase settled at the bottom of the melt to obtain an iron alloy and slag (the main components are shown in Table 29).

[0098] Table 29 Main components of slag

[0099] In this embodiment, the slag CaO / SiO2 is about 0.8, the Pt recovery rate is 98.7%, the Pd recovery rate is 99.1%, and the Rh recovery rate is 98.5%.

[0100] (3) Toxicity test The obtained slag was sampled, ground into fine powder, and subjected to toxicity leaching test by acetic acid dissolution method (the results are shown in Table 30).

[0101] Table 30 Toxicity test results

[0102] Results and Discussion It can be seen from Examples 1 to 5 that by following the addition range of various fluxes, smelting time and smelting temperature ranges described in this application, the recovery rate of platinum group metals can reach more than 98%, and the toxicity test results are all good.

[0103] It can be seen from Comparative Example 1 that the CaO / SiO2 in the slag is about 0.79, the smelting time is 10 minutes, and the recovery rate of platinum group metals is significantly reduced, indicating that the smelting time should not be too short.

[0104] It can be seen from Comparative Example 2 that the CaO / SiO2 in the slag is about 0.49, and the recovery rate of platinum group metals is significantly reduced, indicating that too low CaO / SiO2 is not suitable for the recovery of platinum group metals.

[0105] It can be seen from Comparative Example 3 that the CaO / SiO2 in the slag is about 0.81, the smelting temperature is 1300°C, and the recovery rate of platinum group metals is significantly reduced, indicating that too low a smelting temperature is not conducive to the recovery of platinum group metals.

[0106] It can be seen from Comparative Example 4 that when the slag-forming agent does not contain B2O3 and no additional MgO is added, not only a higher smelting temperature and a longer smelting time are required, but also the recovery rate of platinum group metals is lower and more heavy metals are leached out of the slag.

[0107] It can be seen from Comparative Example 5 that when the collector is reduced iron powder, the recovery rate of platinum group metals is slightly lower, and the toxicity test result is close to that of Example 1. This shows that compared with reduced iron powder, industrial scrap iron is cheaper and complies with the principle of resource recycling.

[0108] It is easy for those skilled in the art to understand that, under the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed. The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application. The above are only preferred implementation methods of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and variations can be made without departing from the technical principles of the present application, and these improvements and variations should also be regarded as the protection scope of the present application.

Claims

1. A method for smelting and enriching platinum group metals from industrial waste iron scraps and waste automobile exhaust catalysts, characterized in that: include: The waste automobile exhaust catalyst, slag-making agent, reducing agent and industrial waste iron filings are uniformly mixed and smelted to obtain an alloy phase and a slag phase containing platinum group metals; Wherein, the slag-forming agent is calcium oxide, silicon dioxide, magnesium oxide and boron trioxide; The mass ratio of calcium oxide to silicon dioxide in the slag phase is controlled to be (0.75-0.9):1, the mass fraction of magnesium oxide is 5%-8%, and the mass fraction of boron trioxide is 4%-8%.

2. The method for smelting and enriching platinum group metals from industrial waste iron filings and waste automobile exhaust catalysts according to claim 1, characterized in that: The mass ratio of the waste automobile exhaust catalyst, the slag-forming agent, the reducing agent and the industrial waste iron filings is 100: (200-350): (4-6): (8-15).

3. The method for smelting and enriching platinum group metals from industrial scrap iron and waste automobile exhaust catalysts according to claim 2, characterized in that: The melting temperature is 1400℃~1600℃, and the melting time is 30min~60min.

4. The method for smelting and enriching platinum group metals from industrial scrap iron and waste automobile exhaust catalysts according to claim 3, characterized in that: The components of the waste automobile exhaust catalyst include: silicon dioxide, aluminum oxide, magnesium oxide and platinum group metals; The waste automobile exhaust catalyst contains 25% to 35% silicon dioxide, 30% to 45% aluminum oxide, and 7% to 10% magnesium oxide by mass fraction. Among the platinum group metals, the platinum content is 300ppm~600ppm, the palladium content is 1800ppm~3300ppm, and the rhodium content is 150ppm~320ppm.

5. The method for smelting and enriching platinum group metals from industrial scrap iron and waste automobile exhaust catalysts according to claim 4, characterized in that: The reducing agent is carbon powder.

6. The method for smelting and enriching platinum group metals from industrial scrap iron and waste automobile exhaust catalysts according to claim 5, characterized in that: The particle size of the industrial scrap iron is less than 500 μm.

7. The method for smelting and enriching platinum group metals from industrial scrap iron and waste automobile exhaust catalysts according to claim 6, characterized in that: The platinum recovery rate is greater than 98%, the palladium recovery rate is greater than 98%, and the rhodium recovery rate is greater than 98%.

8. The method for smelting and enriching platinum group metals from industrial scrap iron and waste automobile exhaust catalysts according to claim 7, characterized in that: The obtained slag was subjected to toxicity leaching test by acetic acid buffer solution method, and the harmful metal content was lower than the environmental protection industry standard of the People's Republic of China.

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