Method for smelting and enriching platinum group metals from industrial scrap iron filings and waste automobile exhaust catalysts

Abstract

The present invention discloses a method for smelting and enriching platinum group metals from industrial waste iron scraps and waste automotive exhaust catalysts, which relates to the technical field of solid waste resource recovery and metallurgy. The method for smelting and enriching platinum group metals includes: uniformly mixing waste automotive exhaust catalysts, slag formers, reducing agents and industrial waste iron scraps, and performing high-temperature smelting to obtain an alloy phase and a slag phase containing platinum group metals. In the method for smelting and enriching platinum group metals of the present invention, by using industrial waste iron scraps instead of conventional elemental iron collectors, not only the production cost is saved, but also the un-reduced FeO in the industrial waste iron scraps enters the molten slag, which will promote the fluidity of the molten slag, facilitate the separation of the slag and the metal. Moreover, by adding boron trioxide to the slag former and controlling the mass ratio of CaO and SiO2 in the molten slag and the mass fraction of magnesium oxide, 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 present invention relates to the technical field of solid waste resource recovery and metallurgy, and particularly relates to a method for smelting and enriching platinum group metals from industrial iron filings and waste automotive exhaust catalysts. Background Art

[0002] Platinum group metals (platinum, palladium, rhodium) are widely used in the industrial field due to their excellent physical and chemical properties (good electrical conductivity, chemical stability, catalytic activity, etc.), especially as an important part of catalysts. The natural resource content of platinum group metals is extremely low, and the extraction and refining costs are relatively high. Therefore, it is necessary to develop a recycling process for platinum group metals. As an important application of platinum group metals, after the service life of automotive exhaust catalysts, platinum group metals adhere to the surface of the carrier. According to statistics, the content of platinum group metals in waste automotive exhaust catalysts is 2000 g / t, which is much higher than that in platinum group metal symbiotic ores (0.8 g / t). At the same time, waste automotive exhaust catalysts contain a large amount of harmful heavy metals and are classified as solid waste. If placed randomly, it will not only waste a large amount of land resources but also cause serious harm to the environment. Therefore, it is necessary to explore a process for efficiently and harmlessly recovering platinum group metals. This is of great significance for both the economy and the environment.

[0003] Currently, the processes for recovering platinum group metals from waste automotive exhaust catalysts can be mainly divided into two categories: pyrometallurgical recovery and hydrometallurgical recovery. Hydrometallurgical recovery has high requirements for raw materials, a cumbersome process, and a large demand for materials, and is not suitable for large-scale production. Pyrometallurgical recovery has low requirements for the grade of raw materials and can be applied to large-scale production. The most important method in the pyrometallurgical process is the metal trapping method.

[0004] Copper trapping has the advantage of low energy consumption, but the subsequent separation operation process is cumbersome and costly. The melting temperature required for iron trapping is relatively high, which easily reduces SiO in the waste automotive exhaust catalyst 2 to form a poorly soluble ferrosilicon alloy with iron. The harmful heavy metals in the waste automotive exhaust catalyst still remain in the slag, posing a risk of environmental pollution. In addition, a large amount of metal as a trapping agent also has a relatively high cost. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the present invention provides a method for recovering platinum group metals from waste automotive exhaust catalysts with low cost and environmental harmlessness.

[0006] To this end, the present invention provides a method for smelting and enriching platinum group metals from industrial iron filings and waste automotive exhaust catalysts, including:

[0007] Mixing the waste automotive exhaust catalyst, slag former, reducing agent, and industrial iron filings evenly, and smelting to obtain an alloy phase and a slag phase containing platinum group metals;

[0008] Among them, the slag-forming agent is calcium oxide, silicon dioxide, magnesium oxide and boron trioxide; in the slag phase, the mass ratio of calcium oxide to silicon dioxide is (0.75~0.9):1, the mass fraction of magnesium oxide is 5%~8%, and the mass fraction of boron trioxide is 4%~8%.

[0009] Furthermore, the mass ratio of the waste automotive exhaust catalyst, the slag-forming agent, the reducing agent to the industrial waste iron filings is 100:(200~350):(4~6):(8~15).

[0010] Furthermore, the smelting temperature is 1400°C~1600°C, and the smelting time is 30min~60min.

[0011] Furthermore, the components of the waste automotive exhaust catalyst include: silicon dioxide, aluminum trioxide, magnesium oxide and platinum group metals;

[0012] Among them, in the waste automotive exhaust catalyst, by mass fraction, silicon dioxide is 25%~35%, aluminum trioxide is 30%~45%, and magnesium oxide is 7%~10%; among the platinum group metals, the platinum content is 300ppm~600ppm, the palladium content is 1800ppm~3300ppm, and the rhodium content is 150ppm~320ppm.

[0013] Furthermore, the reducing agent is carbon powder.

[0014] Furthermore, the particle size of the industrial waste iron filings is less than 500μm.

[0015] Using the above method for smelting and enriching platinum group metals with industrial waste iron filings and waste automotive 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 obtained molten slag is tested for toxic leaching by the acetic acid buffer solution method, and the content of harmful metals is far lower than the environmental protection industry standard of the People's Republic of China.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects:

[0017] The method for smelting and enriching platinum group metals provided by the present invention replaces the conventional elemental iron collector with industrial waste iron filings, which not only saves production costs, but also the un-reduced FeO in the industrial waste iron filings enters the molten slag, which will promote the fluidity of the molten slag and is conducive to slag-metal separation. And by adding boron trioxide to the slag-forming agent and controlling the mass ratio of CaO and SiO 2 in the molten slag and the mass fraction of magnesium oxide, 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 of the Drawings

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments described in the embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings.

[0019] Figure 1 It is a process flow diagram of a method for smelting and enriching platinum group metals from industrial waste iron filings and waste automotive exhaust catalysts provided by the embodiments of the present invention. Specific embodiments

[0020] To better understand the above technical solutions, the following will describe the technical solutions of the embodiments of the present application in detail through the drawings and specific embodiments. It should be understood that the specific features in the embodiments of the present application and the embodiments are detailed descriptions of the technical solutions of the embodiments of the present application, rather than limitations on the technical solutions of the present application. Without conflict, the technical features in the embodiments of the present application and the embodiments can be combined with each other.

[0021] The embodiments of the present invention provide a method for smelting and enriching platinum group metals from industrial waste iron filings and waste automotive exhaust catalysts, including: uniformly mixing waste automotive exhaust catalysts, slag formers, reducing agents, and industrial waste iron filings, and performing high-temperature smelting to obtain an alloy phase and a slag phase containing platinum group metals.

[0022] In the method for smelting and enriching platinum group metals from industrial waste iron filings and waste automotive exhaust catalysts provided by the embodiments of the present invention, by using industrial waste iron filings instead of conventional elemental iron capture agents, not only the production cost is saved, but also the un-reduced FeO in the industrial waste iron filings enters the slag, which will promote the fluidity of the slag and is beneficial to the separation of slag and metal. Optionally, the uniformly mixed materials are put into a crucible, and the crucible is put into an intermediate frequency induction furnace for capture smelting. After high-temperature smelting, the melt is poured into a prepared container, and the alloy phase and the slag phase containing platinum group metals are separated under the action of gravity, and the alloy phase settles at the bottom of the melt.

[0023] In some embodiments, the slag formers are calcium oxide, silicon dioxide, magnesium oxide, and boron trioxide. Among them, the source of boron trioxide can be boric acid.

[0024] Specifically, a part of the un-reduced ferrous oxide in the industrial waste iron filings, together with the alumina, silicon dioxide, and magnesium oxide contained in the slag former and the waste automotive exhaust catalyst, jointly constitute CaO-SiO 2 -Al 2 O 3 -MgO-B 2 O 3-FeO six-component slag system. This slag system can not only effectively reduce the smelting temperature and energy consumption, but also more easily generate glass slag that can effectively encapsulate harmful heavy metals in waste automotive exhaust catalysts, where FeO and B 2 O 3 can effectively reduce the melting point and viscosity of the molten slag, thereby reducing the operating temperature of the heating equipment and reducing energy consumption. In addition, B 2 O 3 can form a network structure with silicate, enhance the amorphous structure of the glass, inhibit the formation of crystals, thereby improving the degree of vitrification of the glass, and promoting the encapsulation of heavy metals in the melt.

[0025] In some embodiments, in the slag phase, the mass ratio of calcium oxide to silicon dioxide 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%.

[0026] By adjusting the calcium-silicon mass ratio of the molten slag, the mass fraction of magnesium oxide, and adding boron trioxide as a glass former, the final slag becomes amorphous glass slag. The glass slag can encapsulate harmful substances in the waste automotive exhaust catalyst in the molten slag and is difficult to leach, thus reducing the harm to the environment. And boron trioxide can reduce the trapping temperature of smelting, and further improve the fluidity of the molten slag and the trapping efficiency.

[0027] In some embodiments, the mass ratio of the waste automotive exhaust catalyst, slag former, reducing agent, and industrial iron filings is 100:(200~350):(4~6):(8~15).

[0028] In some embodiments, the smelting temperature is 1400°C~1600°C, and the smelting time is 30 min~60 min. Preferably, the smelting temperature is 1500°C±20°C, and the smelting time is 40 min~50 min.

[0029] Specifically, when the smelting temperature is lower than 1400°C, it will affect the fluidity of the molten slag, resulting in difficulty in trapping platinum group metals in the poorly flowing melt and affecting the recovery efficiency. When the smelting temperature is higher than 1600°C, silicon in the melt will be reduced to form insoluble ferrosilicon alloy with iron as the trapping agent, which causes great difficulties for the subsequent separation operation of platinum group metals. If the smelting time is too short, less than 30 min, there will not be enough time for platinum group metals to form alloy particles with trapping metals and settle to the bottom of the melt, resulting in their remaining in the melt and affecting the recovery rate of platinum group metals. If the smelting time is too long, more than 60 min, it will affect the service life of the equipment and consume a large amount of heat energy, wasting resources. And, on an industrial scale, the common operating temperature range for iron trapping and recovering platinum group metals is 1600°C~2000°C, and this application significantly reduces the smelting temperature.

[0030] In some embodiments, the components of the waste automotive exhaust catalyst include: silica, alumina, magnesia, and platinum group metals; wherein, in the waste automotive exhaust catalyst, by mass fraction, silica is 25% - 35%, alumina is 30% - 45%, and magnesia is 7% - 10%; among the platinum group metals, the platinum content is 300 ppm - 600 ppm, the palladium content is 1800 ppm - 3300 ppm, and the rhodium content is 150 ppm - 320 ppm.

[0031] In some embodiments, the reducing agent is carbon powder.

[0032] Specifically, the reducing agent is carbon powder. The reducing agent can not only effectively reduce the oxides of platinum group metals in the waste automotive exhaust catalyst to the metallic state, improving the recovery efficiency and purity, but also reduce a part of the iron oxides in the iron filings to elemental iron, ultimately achieving the purpose of efficient and energy-saving recovery. Common reducing agents are H 2 and CO. Compared with CO, using H 2 has a certain degree of danger and may explode if operated improperly. Therefore, carbon powder is selected as the reducing agent to generate CO.

[0033] In some embodiments, the particle size of the industrial waste iron filings is less than 500 μm.

[0034] It can be understood that during the smelting process, the larger the contact area of the collector in the melt, the easier it is to promote the capture of platinum group metals by the capture metal. Therefore, it is necessary to control the particle size of the iron filings to make it have a larger specific surface area, which means that with the same mass of the collector, more surfaces are used to contact the platinum group metals in the melt, thereby promoting the progress of the recovery process.

[0035] In summary, using the above method of smelting and enriching platinum group metals with industrial waste iron filings and waste automotive 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 obtained slag is subjected to a toxicity leaching test 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).

[0036] Example 1 A method for smelting and enriching platinum group metals with industrial waste iron filings and waste automotive exhaust catalysts

[0037] As Figure 1 shown, it includes the following steps:

[0038] (1) Batching

[0039] Crush and grind the waste automotive exhaust catalyst (the main components are shown in Table 1), and then weigh 100 g and mix it with 96 g of SiO 2, 99 g of CaO, 10 g of MgO, 32 g of boric acid, 10 g of iron filings and 5 g of carbon powder are mixed evenly and placed in a graphite crucible.

[0040] Table 1 Main components of a certain waste automobile exhaust catalyst

[0041]

[0042] (2) Collection smelting

[0043] The graphite crucible is placed in an intermediate frequency induction furnace and heated at a rate of 10 °C / min under air conditions. After heating to 1500 °C, it is kept warm for 40 min. After the heat preservation is completed, the melt is poured into a pre-prepared mold. The platinum group metals enter the metal phase, and the alloy phase and the slag phase are separated under the action of gravity. The alloy phase settles at the bottom of the melt to obtain ferroalloy and molten slag (the main components are shown in Table 2).

[0044] Table 2 Main components of molten slag

[0045]

[0046] In this example scheme, the CaO / SiO of the molten slag 2 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%.

[0047] (3) Toxicity test

[0048] The obtained molten slag is sampled, ground into fine powder, and subjected to a toxicity leaching test by the acetic acid dissolution method (the results are shown in Table 3).

[0049] Table 3 Toxicity test results

[0050]

[0051] Example 2 A method for smelting and enriching platinum group metals from industrial waste iron filings and waste automobile exhaust catalysts

[0052] As Figure 1 shown, it includes the following steps:

[0053] (1) Batching

[0054] The waste automobile exhaust catalyst (the main components are shown in Table 4) is crushed and ground, and then 100 g is weighed and mixed evenly with 140 g of SiO 2 , 155 g of CaO, 24 g of MgO, 22 g of boric acid, 10 g of iron filings and 5 g of carbon powder, and placed in a graphite crucible.

[0055] Table 4 Main components of a certain waste automobile exhaust catalyst

[0056]

[0057] (2) Trapping and smelting

[0058] Put the graphite crucible into the intermediate frequency induction furnace and heat it up at a rate of 10 °C / min under air conditions. After heating up to 1600 °C, keep it warm for 50 min. After the heat preservation is completed, pour the melt into a pre-prepared mold. The platinum group metals enter the metal phase, and the alloy phase and the slag phase are separated under the action of gravity. The alloy phase settles at the bottom of the melt to obtain ferroalloy and molten slag (the main components are shown in Table 5).

[0059] Table 5 Main components of molten slag

[0060]

[0061] For the solution of this example, the CaO / SiO of the molten slag 2 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%.

[0062] (3)Toxicity test

[0063] Take samples of the obtained molten slag, grind them into fine powder, and conduct toxicity leaching tests through the acetic acid dissolution method (the results are shown in Table 6).

[0064] Table 6 Toxicity test results

[0065]

[0066] Example 3

[0067] As Figure 1 shown, it includes the following steps:

[0068] (1)Batching

[0069] Crush and grind the waste automotive exhaust catalyst (the main components are shown in Table 7), then weigh 100 g and mix it evenly with 105 g of SiO 2 , 105 g of CaO, 7 g of MgO, 36 g of boric acid, 10 g of iron filings and 5 g of carbon powder, and put them into a graphite crucible.

[0070] Table 7 Main components of a certain waste automotive exhaust catalyst

[0071]

[0072] (2)Trapping and smelting

[0073] Put the graphite crucible into a medium-frequency induction furnace and heat it up at a rate of 10 °C / min under air conditions. After heating up to 1500 °C, keep it warm for 60 min. After the heat preservation is over, pour the melt into a pre-prepared mold. The platinum group metals enter the metal phase, and the alloy phase and the slag phase are separated under the action of gravity. The alloy phase settles at the bottom of the melt to obtain ferroalloy and molten slag (the main components are shown in Table 8).

[0074] Table 8 Main components of the molten slag

[0075]

[0076] For this example scheme, the CaO / SiO of the molten slag 2 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%.

[0077] (3)Toxicity test

[0078] Take a sample of the obtained molten slag, grind it into fine powder, and conduct a toxicity leaching test by the acetic acid dissolution method (the results are shown in Table 9).

[0079] Table 9 Toxicity test results

[0080]

[0081] Example 4

[0082] As Figure 1 shown, it includes the following steps:

[0083] (1)Batching

[0084] Crush and grind the waste automotive exhaust catalyst (the main components are shown in Table 10), then weigh 100 g and mix it evenly with 91 g of SiO 2 , 98 g of CaO, 8.3 g of MgO, 43 g of boric acid, 10 g of iron filings and 5 g of carbon powder, and put them into a graphite crucible.

[0085] Table 10 Main components of a certain waste automotive exhaust catalyst

[0086]

[0087] (2)Trapping smelting

[0088] Put the graphite crucible into a medium-frequency induction furnace and heat it up at a rate of 10 °C / min under air conditions. After heating up to 1400 °C, keep it warm for 30 min. After the heat preservation is over, pour the melt into a pre-prepared mold. The platinum group metals enter the metal phase, and the alloy phase and the slag phase are separated under the action of gravity. The alloy phase settles at the bottom of the melt to obtain ferroalloy and molten slag (the main components are shown in Table 11).

[0089] Table 11 Main components of the slag

[0090]

[0091] For this embodiment, the CaO / SiO of the slag 2 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%.

[0092] (3)Toxicity test

[0093] Take samples of the obtained slag, grind them into fine powder, and conduct toxicity leaching tests by acetic acid dissolution method (the results are shown in Table 12).

[0094] Table 12 Toxicity test results

[0095]

[0096] Example 5

[0097] As Figure 1 shown, it includes the following steps:

[0098] (1)Batch preparation

[0099] Crush and grind the waste automotive exhaust catalyst (the main components are shown in Table 13), then weigh 100 g and mix it evenly with 124 g of SiO 2 , 130 g of CaO, 22 g of MgO, 27 g of boric acid, 10 g of iron filings and 5 g of carbon powder, and put them into a graphite crucible.

[0100] Table 13 Main components of a certain waste automotive exhaust catalyst

[0101]

[0102] (2)Collection smelting

[0103] Put the graphite crucible into an intermediate frequency induction furnace and heat it at a rate of 10 °C / min under air conditions. After heating to 1500 °C, keep it warm for 40 min. After the heat preservation ends, pour the melt into a pre-prepared mold. The platinum group metals enter the metal phase, and the alloy phase and the slag phase are separated under the action of gravity. The alloy phase settles at the bottom of the melt to obtain ferroalloy and slag (the main components are shown in Table 14).

[0104] Table 14 Main components of the slag

[0105]

[0106] For this embodiment, the CaO / SiO of the slag 2 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%.

[0107] (3)Toxicity test

[0108] 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).

[0109] Table 15 Toxicity test results

[0110]

[0111] Comparative example 1

[0112] (1)Batching

[0113] The waste automotive exhaust catalyst (the main components are shown in Table 16) was crushed and ground, and then 100 g was weighed and mixed evenly with 96 g of SiO 2 , 99 g of CaO, 10 g of MgO, 32 g of boric acid, 10 g of iron filings and 5 g of carbon powder, and placed in a graphite crucible.

[0114] Table 16 Main components of a certain waste automotive exhaust catalyst

[0115]

[0116] (2)Trapping smelting

[0117] The graphite crucible was placed in an intermediate frequency induction furnace and heated at a rate of 10 °C / min under air conditions until it reached 1500 °C and then held for 10 min. After the holding period, 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 ferroalloy and slag (the main components are shown in Table 17).

[0118] Table 17 Main components of the slag

[0119]

[0120] For the embodiment scheme, the CaO / SiO 2 of the slag 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%.

[0121] (3)Toxicity test

[0122] 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).

[0123] Table 18 Toxicity test results

[0124]

[0125] Comparative example 2

[0126] 1) Ingredients

[0127] Crush and grind the waste automotive exhaust catalyst (the main components are shown in Table 19), then weigh 100 g and mix it evenly with 136 g of SiO 2 , 80 g of CaO, 10 g of MgO, 32 g of boric acid, 10 g of iron filings and 5 g of carbon powder, and put them into a graphite crucible.

[0128] Table 19 Main components of a certain waste automotive exhaust catalyst

[0129]

[0130] (2) Trapping smelting

[0131] Put the graphite crucible into an intermediate frequency induction furnace and heat it up at a rate of 10 °C / min under air conditions. After heating up to 1500 °C, keep it warm for 40 min. After the heat preservation is over, pour the melt into a pre-prepared mold. The platinum group metals enter the metal phase, and the alloy phase and the slag phase are separated under the action of gravity. The alloy phase settles at the bottom of the melt to obtain ferroalloy and molten slag (the main components are shown in Table 20).

[0132] Table 20 Main components of the molten slag

[0133]

[0134] For the embodiment scheme, the CaO / SiO of the molten slag 2 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%.

[0135] (3) Toxicity test

[0136] Take a sample of the obtained molten slag, grind it into fine powder, and conduct a toxicity leaching test by the acetic acid dissolution method (the results are shown in Table 21).

[0137] Table 21 Toxicity test results

[0138]

[0139] Comparative example 3

[0140] 1) Ingredients

[0141] Crush and grind the waste automotive exhaust catalyst (the main components are shown in Table 22), then weigh 100 g and mix it evenly with 96 g of SiO 2 , 99 g of CaO, 10 g of MgO, 32 g of boric acid, 10 g of iron filings and 5 g of carbon powder, and put them into a graphite crucible.

[0142] Table 22 Main components of a certain waste automotive exhaust catalyst

[0143]

[0144] (2)Collection smelting

[0145] Put the graphite crucible into the intermediate frequency induction furnace and heat it up at a rate of 10 °C / min under air conditions. After heating up to 1300 °C, keep it warm for 40 min. After the heat preservation is over, pour the melt into a pre-prepared mold. The platinum group metals enter the metal phase, and the alloy phase and the slag phase are separated under the action of gravity. The alloy phase settles at the bottom of the melt to obtain ferroalloy and molten slag (the main components are shown in Table 23).

[0146] Table 23 Main components of molten slag

[0147]

[0148] For the solution of this embodiment, the CaO / SiO of the molten slag 2 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%.

[0149] (3)Toxicity test

[0150] Take samples of the obtained molten slag, grind them into fine powder, and conduct toxicity leaching tests by acetic acid dissolution method (the results are shown in Table 24).

[0151] Table 24 Toxicity test results

[0152]

[0153] Comparative example 4

[0154] (1)Batching

[0155] Crush and grind the waste automotive exhaust catalyst (the main components are shown in Table 25), then weigh 100 g and mix it evenly with 118 g of SiO 2 , 115 g of CaO, 10 g of iron filings and 5 g of carbon powder, and put them into a graphite crucible.

[0156] Table 25 Main components of a certain waste automotive exhaust catalyst

[0157]

[0158] (2)Collection smelting

[0159] Put the graphite crucible into the intermediate frequency induction furnace and heat it up at a rate of 10 °C / min under air conditions. After heating up to 1700 °C, keep it warm for 80 min. After the heat preservation is over, pour the melt into a pre-prepared mold. The platinum group metals enter the metal phase, and the alloy phase and the slag phase are separated under the action of gravity. The alloy phase settles at the bottom of the melt to obtain ferroalloy and molten slag (the main components are shown in Table 26).

[0160] Table 26 Main components of the slag

[0161]

[0162] In this example, the CaO / SiO of the slag 2 is approximately 0.8, the Pt recovery rate is 96.9%, the Pd recovery rate is 97.2%, and the Rh recovery rate is 95.8%.

[0163] (3)Toxicity test

[0164] 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 27).

[0165] Table 27 Toxicity test results

[0166]

[0167] Comparative example 5

[0168] (1)Batching

[0169] The waste automotive exhaust catalyst (the main components are shown in Table 28) was crushed and ground, and then 100 g was weighed and mixed evenly with 96 g of SiO 2 , 99 g of CaO, 10 g of MgO, 32 g of boric acid, 10 g of reduced iron powder and 5 g of carbon powder, and placed in a graphite crucible.

[0170] Table 28 Main components of a certain waste automotive exhaust catalyst

[0171]

[0172] (2)Trapping smelting

[0173] The graphite crucible was placed in an intermediate frequency induction furnace and heated at a rate of 10 °C / min under air conditions. After heating to 1500 °C, it was held for 40 min. After the holding was completed, 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 ferroalloy and slag (the main components are shown in Table 29).

[0174] Table 29 Main components of the slag

[0175]

[0176] In this example, the CaO / SiO of the slag 2 is approximately 0.8, the Pt recovery rate is 98.7%, the Pd recovery rate is 99.1%, and the Rh recovery rate is 98.5%.

[0177] (3)Toxicity test

[0178] The obtained slag was sampled, ground into fine powder, and subjected to a toxicity leaching test by acetic acid dissolution method (the results are shown in Table 30).

[0179] Table 30 Toxicity test results

[0180]

[0181] Results and discussion

[0182] It can be seen from Examples 1 to 5 that by following the addition ranges of various fluxes described in this application and the ranges of smelting time and smelting temperature, the recovery rate of platinum group metals can reach over 98%, and the toxicity test results are all good.

[0183] It can be seen from Comparative Example 1 that the CaO / SiO in the slag 2 is about 0.79, the smelting time is 10 min, and the recovery rate of platinum group metals is significantly reduced, indicating that the smelting time should not be too short.

[0184] It can be seen from Comparative Example 2 that the CaO / SiO in the slag 2 is about 0.49, and the recovery rate of platinum group metals is significantly reduced, indicating that too low CaO / SiO 2 is not suitable for the recovery of platinum group metals.

[0185] It can be seen from Comparative Example 3 that the CaO / SiO in the slag 2 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 smelting temperature is not conducive to the recovery of platinum group metals.

[0186] It can be seen from Comparative Example 4 that when the slag former does not contain B 2 O 3 , and without additional addition of MgO, not only higher smelting temperature and longer smelting time are required, but also the recovery rate of platinum group metals is lower, and more heavy metals are leached from the slag.

[0187] 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 results are close to those of Example 1. It shows that compared with reduced iron powder, industrial waste iron filings have lower cost and follow the principle of resource recycling.

[0188] It is easily understandable to those skilled in the art that, on the premise of no conflict, the above-mentioned advantageous ways can be freely combined and superimposed. The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application. The above is only the preferred implementation manner of the present application. It should be noted that for those of ordinary skill in the art in this technical field, several improvements and variations can be made without departing from the technical principle of the present application, and these improvements and variations should also be regarded as within 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%; 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); the ferrous oxide in the industrial waste iron filings that is not reduced by the reducing agent, the aluminum oxide, silicon dioxide and magnesium oxide contained in the slag-forming agent and the waste automobile exhaust catalyst together form a CaO-SiO2-Al2O3-MgO-B2O3-FeO hexavalent slag system; 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.

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 melting temperature is 1400℃~1600℃, and the melting time is 30min~60min.

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 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.

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 reducing agent is carbon powder.

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 particle size of the industrial scrap iron is less than 500 μm.

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 platinum recovery rate is greater than 98%, the palladium recovery rate is greater than 98%, and the rhodium recovery rate is greater than 98%.

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