Method for photocatalytic leaching of precious metal in aqueous phase of chlorinated salt

Abstract

The invention belongs to the technical field of photocatalytic application, and particularly relates to a photocatalytic leaching method for precious metal in a brine phase of chlorate. The method comprises the following steps: mixing the waste rich in noble metal, a solution containing chlorate and a photocatalyst, carrying out photocatalytic leaching reaction on the obtained mixed slurry under an illumination condition, and carrying out solid-liquid separation to obtain a leaching solution containing noble metal. The chlorate solution is used as a solution environment, a photocatalytic leaching method is used, precious metal is oxidized to generate a precious metal chlorine complex, the precious metal chlorine complex is dissolved in water, and finally the purpose that the precious metal is leached into a solution from a solid is achieved. The method has the characteristics of low reaction cost, low reaction energy consumption and high leaching rate.

Description

Technical Field

[0001] This invention belongs to the field of photocatalysis application technology, specifically relating to a method for photocatalytic leaching of noble metals in a chloride brine phase. Background Technology

[0002] Platinum group metals (PGMs) refer to six metals: ruthenium, rhodium, palladium, osmium, iridium, and platinum. These metals possess excellent properties such as high stability, high temperature resistance, and high catalytic activity. Platinum (Pt), palladium (Pd), and rhodium (Rh), in particular, are considered the "vitamins" of modern industry and are widely used in automotive catalysts, petroleum, electronics, chemicals, and environmental protection. Catalysts are the primary consumer of PGMs. With the depletion and disposal of catalysts, a large amount of secondary PGM resources are generated, such as depleted automotive catalysts and spent petrochemical catalysts. Given the scarcity of PGM resources, effectively regenerating and utilizing PGMs from depleted catalysts will help conserve primary PGM ore resources.

[0003] Taking spent automotive catalysts as an example, platinum group metals in spent automotive three-way catalysts are currently mainly recovered through pyrometallurgical and hydrometallurgical processes. However, pyrometallurgical recovery suffers from drawbacks such as high energy consumption and demanding equipment requirements, while hydrometallurgical processes may generate toxic gases and are difficult to recycle waste liquid. Photocatalysis technology, due to its mild reaction conditions, environmental friendliness, and high efficiency, is widely used to degrade pollutants and shows great application potential in the energy and environmental protection fields. Related technologies disclose a photocatalytic metal dissolution method, mainly using cyanide compounds and organochlorides as solvents to dissolve the metal. This method avoids the harsh conditions of high temperature, high pressure, and strong acid to some extent, but the entire reaction involves organic solutions, resulting in high production costs and the potential for toxic and harmful byproducts from the decomposition of organic solvents during organic leaching. Related technologies also disclose a method for photocatalytic metal dissolution in aqueous solutions, which avoids pollution from organic solutions, but the iodine and bromide ions in the halogen salts used still pose a certain degree of pollution to water bodies. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a method for photocatalytic leaching of precious metals in chloride brine phase. The method provided by this invention can efficiently leach precious metals from waste containing precious metals, and is green, environmentally friendly, pollution-free, low-cost, with low reaction energy consumption and high leaching rate.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for photocatalytic leaching of noble metals from a chloride brine phase, comprising the following steps:

[0007] Waste rich in precious metals, a solution containing chloride salts, and a photocatalyst are mixed. The resulting slurry is subjected to photocatalytic leaching under light conditions, followed by solid-liquid separation to obtain a leachate containing precious metals.

[0008] Preferably, the precious metals in the waste rich in precious metals include one or more of ruthenium, rhodium, palladium, osmium, iridium and platinum.

[0009] Preferably, the chloride salt is a chlorinated inorganic salt; the chlorinated inorganic salt includes one or more of sodium chloride, potassium chloride, magnesium chloride, ammonium chloride, calcium chloride, aluminum chloride, and lithium chloride.

[0010] Preferably, the photocatalyst comprises an organic photocatalyst and / or an inorganic photocatalyst; the organic photocatalyst comprises one or more of g-C3N4, perylene diimide, and perylene tetracarboxylic acid; the inorganic photocatalyst comprises one or more of BiOCl, BiVO4, Bi2MoO6, ZnO, ZnS, WO3, and TiO2.

[0011] Preferably, the wavelength of the illumination is 150–1500 nm; the intensity of the illumination is ≥100 μW / cm². 2 The illumination time is 0.01 to 3600 hours.

[0012] Preferably, the concentration of chloride in the chloride-containing solution is 0.001–10000 g / L.

[0013] Preferably, the mass ratio of the waste rich in precious metals to the volume of the chloride-containing solution is 1 g:(1-1000) mL.

[0014] Preferably, the mass ratio of the precious metal-rich waste to the photocatalyst is 0.1 to 500:1.

[0015] Preferably, the pH value of the chloride-containing solution is <7.

[0016] Preferably, before mixing the waste material rich in precious metals, the chloride-containing solution, and the photocatalyst, the method further includes: sequentially crushing, grinding, and sieving the waste material rich in precious metals to obtain the waste powder rich in precious metals; the particle size of the waste powder rich in precious metals is ≥0.5μm.

[0017] This invention provides a method for photocatalytic leaching of precious metals in a chloride salt solution, comprising the following steps: mixing waste rich in precious metals, a chloride salt solution and a photocatalyst, subjecting the resulting mixed slurry to a photocatalytic leaching reaction under light irradiation, separating the solid and liquid phases to obtain a leachate containing precious metals.

[0018] This invention uses a chloride-containing solution as the solution environment. A photocatalyst generates photogenerated electrons and holes under illumination. These photogenerated holes oxidize chloride ions to produce chlorine free radicals. The noble metal is oxidized by these chlorine free radicals, changing from a low-valence state to a high-valence state. The chlorine free radicals then coordinate with chloride ions to form water-soluble noble metal chloride complexes, thus achieving the purpose of leaching the noble metal from a solid to a solution. Compared with existing technologies that use high temperatures, high pressures, strong acids, and organic pollutants, the method of this invention has lower equipment requirements. Leaching can be completed under room temperature, normal pressure, and weakly acidic conditions. It is environmentally friendly, pollution-free, low-cost, has low reaction energy consumption, and a high leaching rate. Attached Figure Description

[0019] Figure 1 The graph shows a comparison of the leaching rates of Pd in ​​Examples 1-13 and Comparative Examples 1-2.

[0020] Figure 2 The graph shows a comparison of the leaching rates of Pt in Examples 1-13 and Comparative Examples 1-2.

[0021] Figure 3 The graph shows a comparison of the leaching rates of Rh in Examples 1-13 and Comparative Examples 1-2. Detailed Implementation

[0022] This invention provides a method for photocatalytic leaching of noble metals from a chloride brine phase, comprising the following steps:

[0023] Waste rich in precious metals, a solution containing chloride salts, and a photocatalyst are mixed. The resulting slurry is subjected to photocatalytic leaching under light conditions, followed by solid-liquid separation to obtain a leachate containing precious metals.

[0024] Unless otherwise specified, the present invention does not have special requirements on the source of raw materials used, and commercially available products well known to those skilled in the art can be used.

[0025] This invention mixes waste rich in precious metals, a solution containing chloride salts, and a photocatalyst. The resulting mixed slurry undergoes a photocatalytic leaching reaction under light irradiation, followed by solid-liquid separation to obtain a leachate containing precious metals.

[0026] In one implementation, the precious metal-rich waste contains one or more of ruthenium, rhodium, palladium, osmium, iridium, and platinum, specifically one or more of rhodium (Rh), palladium (Pd), and platinum (Pt). The content of precious metals in the waste is higher than the cutoff grades: Pt grade greater than 0.341 g / t, Pd grade greater than 0.386 g / t, Os+Ir grade greater than 0.041 g / t, and Rh+Ru grade greater than 0.028 g / t. In a specific embodiment, the Pt grade is 2980 g / t, the Pd grade is 3870 g / t, and the Rh grade is 8 g / t. The precious metals can form complexes with Cl and leach from the solid waste.

[0027] As one implementation method, the waste material rich in precious metals includes waste automotive three-way catalysts, waste petrochemical catalysts, proton exchange membranes from waste fuel cells, implantable electronic devices containing precious metals in medicine, biosensors containing precious metals, high-end electronic components and circuit boards. In a specific embodiment, it is waste automotive three-way catalysts; the waste automotive three-way catalyst is a waste automotive three-way catalyst rich in platinum, palladium and rhodium.

[0028] In one implementation method, before mixing the waste rich in precious metals, the chloride-containing solution, and the photocatalyst, the process further includes: sequentially crushing, grinding, and sieving the waste rich in precious metals to obtain the waste powder rich in precious metals. This invention does not specifically limit the crushing and grinding process; any crushing and grinding process well-known in the art can be used. The crushing equipment is a crusher; the grinding equipment is a grinder; the mesh size of the sieve used for sieving is ≤6250 mesh, specifically 70 mesh in this embodiment; the particle size of the waste powder rich in precious metals is ≥0.5 μm, specifically 0.5–212 μm in this embodiment. The waste powder rich in precious metals used in this invention only needs to be ≥0.5 μm. The specific leaching effect depends on the coating state of the precious metals in the waste. For example, virgin waste may not require crushing or grinding, and the entire piece can be leached. The particle size of the waste rich in precious metals affects the leaching rate of the precious metals; as the particle size of the waste rich in precious metals decreases, the leaching effect initially increases and then slowly decreases. The present invention utilizes the particle size of precious metal-rich waste within the aforementioned range to maximize the complete leaching of precious metals. The particle size of the precious metal-rich waste powder is related to the occurrence state of the precious metals and the size of the reaction vessel. For example, for raw materials such as automotive three-way catalysts where the precious metals are only on the surface of the carrier, they can be directly subjected to photocatalytic leaching without crushing or grinding. The only difference is that smaller particle sizes can accelerate the reaction.

[0029] In one embodiment, the chloride salt is a chlorinated inorganic salt; the chlorinated inorganic salt includes one or more of sodium chloride (NaCl), potassium chloride (KCl), magnesium chloride (MgCl2), ammonium chloride (NH4Cl), calcium chloride (CaCl2), aluminum chloride (AlCl3), and lithium chloride (LiCl), with specific embodiments including sodium chloride, potassium chloride, ammonium chloride, calcium chloride, or aluminum chloride; the concentration of chloride salt in the chloride-containing solution is 0.001–10000 g / L, another embodiment is 50–200 g / L, and a specific embodiment is 142 g / L; the mass ratio of the precious metal-rich waste to the volume of the chloride-containing solution is 1 g:(1–1000) mL, another embodiment is 1 g:(10–200) mL, and a specific embodiment is 1 g:50 mL; the molar concentration of chloride ions in the chloride-containing solution is greater than the molar concentration of precious metals in the precious metal-rich waste, thereby ensuring that the precious metals in the precious metal waste can be completely leached out.

[0030] In one embodiment, the chloride-containing solution is an aqueous solution containing chloride, specifically salt lake water or seawater.

[0031] As one implementation method, the pH value of the chloride-containing solution is <7, specifically 5 in this embodiment; when the pH value of the chloride-containing solution is ≥7, the pH value of the chloride-containing solution is adjusted to <7 using HCl.

[0032] In one embodiment, the photocatalyst comprises an organic photocatalyst and / or an inorganic photocatalyst; the organic photocatalyst comprises one or more of g-C3N4, perylene diimide, and perylene tetracarboxylic acid, with g-C3N4 being a specific example; the inorganic photocatalyst comprises one or more of BiOCl, BiVO4, Bi2MoO6, ZnO, ZnS, WO3, and TiO2, with BiOCl, BiVO4, Bi2MoO6, ZnO, ZnS, WO3, or TiO2 being a specific example; the mass ratio of the precious metal-rich waste to the photocatalyst is 0.1–500:1, in another embodiment it is 5–200:1, and in a specific example it is 10:1.

[0033] The optimal amount of photocatalyst required varies depending on the type of waste rich in precious metals. As the amount of photocatalyst increases, the leaching effect initially increases and then plateaus. This invention utilizes the ratio of the total mass of precious metals in the waste rich in precious metals to the mass of the photocatalyst within the aforementioned range to effectively leach the precious metals from the waste.

[0034] In one embodiment, the wavelength of the illumination is 150–1500 nm, in another embodiment it is 200–1000 nm, and in a specific embodiment it is 365 nm; the intensity of the illumination is ≥100 μW / cm². 2 In another embodiment, the value is 1000–10000 μW / cm. 2 In a specific embodiment, it is 6000 μW / cm 2 The illumination time is 0.01–3600 h, or 5–50 h in another embodiment, and 12 h in a specific example; the photocatalytic leaching reaction is carried out under stirring conditions; the stirring rate is ≥100 rpm, and 540 rpm in a specific example. The light intensity used in this invention can ensure the photocatalytic leaching reaction rate and promote the complete leaching of precious metals.

[0035] The illumination used in this invention covers deep ultraviolet light, ultraviolet light, visible light, and near-infrared light.

[0036] As one implementation method, the solid-liquid separation method is sedimentation, filtration, centrifugation or evaporation, and in a specific embodiment it is filtration; the filtration method is to use a vacuum filtration device to separate the liquid and solid by passing them through qualitative filter paper.

[0037] The mechanism of this invention mainly relies on the generation of photogenerated electrons and holes by the photocatalyst under illumination. The photogenerated holes oxidize chloride ions to produce chloride radicals, which then oxidize and coordinate the noble metal, forming corresponding noble metal chloride complexes that dissolve in water. Taking TiO2 as the photocatalyst and NaCl solution as the solvent as an example, the main stoichiometric equations are as follows:

[0038] TiO2→e - +h + (1)

[0039] e - +O2→·O2 - (2)

[0040] h + +NaCl→ · Cl+Na + (3)

[0041] Pt+2NaCl+4·Cl→Na2{PtCl6] (4)

[0042] Pd+2NaCl+2·Cl→Na2[PdCl4] (5)

[0043] Rh+3NaCl+3·Cl→Na3[RhCl6] (6).

[0044] In this invention, the chloride-containing solution can be recycled multiple times. The method of this invention is less affected by the cations of chloride salts and mainly relies on photocatalytic oxidation of chloride ions to generate chloride free radicals. After the reaction, the unused chloride free radicals can react with water to generate chloride ions or chlorine gas. After multiple cycles of reaction, the chloride ion consumption can be maintained by adding solid chloride salts to the chloride-containing solution.

[0045] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0046] Example 1

[0047] (1) First, the waste three-way catalyst of automobiles rich in platinum, palladium and rhodium was used as raw material. The platinum, palladium and rhodium content is shown in Table 1. The catalyst was crushed, ground and dried.

[0048] Table 1. Precious metal content in spent automotive three-way catalysts

[0049] element Pd Pt Rh Content (mg / g) 3.94 2.97 0.01

[0050] (2) Secondly, taking inexpensive NaCl as an example, prepare a 2mol / L sodium chloride solution and adjust the pH to 5 using HCl;

[0051] (3) Subsequently, 1g of waste automotive three-way catalyst and 0.1g of photocatalyst (TiO2, commercially available P25) were added to the prepared 50mL NaCl solution, and the solution was placed under light irradiation (wavelength 365nm) and stirred at 540rpm for 12h with a light intensity of 6000μW / cm². 2 To achieve photocatalytic leaching reaction;

[0052] (4) Finally, after leaching, solid and liquid are separated. The resulting leaching residue is washed with deionized water until neutral, collected and dried through a vacuum filter funnel, and then 0.2g of leaching residue is microwave digested with 4.5mL of aqua regia at a microwave power of 650W, a digestion temperature of 220℃, and a digestion time of 20min. After digestion, the acid solution is filtered, diluted to a final volume, and transferred to a centrifuge tube for testing.

[0053] (5) Test of photocatalytic leaching rate:

[0054] The leaching rate of noble metals was determined using inductively coupled plasma (ICP). Each experiment was repeated twice, and the ICP measurement was repeated three times. Leaching rate (μ) s The calculation formula is shown in equation (1):

[0055]

[0056] Where R0 represents the grade (%) of the target element in the waste automotive three-way catalyst added before photocatalytic leaching, ms The mass (mg) of photocatalytic leaching residue digested, C s and V s The values ​​represent the concentration (mg / L) and the volume (L) of the target element in the ICP measurement solution of the photocatalytic leaching residue after digestion and volume adjustment, respectively. A higher leaching rate indicates a better leaching effect.

[0057] Example 2

[0058] The specific steps are the same as those in Example 1, except that NaCl is replaced with KCl in step (2) of Example 1.

[0059] Example 3

[0060] The specific steps are the same as those in Example 1, except that in step (2) of Example 1, NaCl is replaced with AlCl3.

[0061] Example 4

[0062] The specific steps are the same as those in Example 1, except that in step (2) of Example 1, NaCl is replaced with NH4Cl.

[0063] Example 5

[0064] The specific steps are the same as those in Example 1, except that in step (2) of Example 1, NaCl is replaced with CaCl2.

[0065] Example 6

[0066] The specific steps are the same as those in Example 1, except that the photocatalyst in step (3) of Example 1 is replaced with self-made g-C3N4. The preparation method of g-C3N4 powder is as follows: 15g of melamine is added to a covered alumina crucible, and then heated to 550℃ at a heating rate of 2℃ / min, kept warm and calcined for 4h, and then cooled naturally. After cooling to room temperature, the resulting yellow product is g-C3N4.

[0067] Example 7

[0068] The specific steps are the same as those in Example 1, except that the photocatalyst in step (3) of Example 1 is replaced with a self-made BiOCl. The specific preparation method is as follows: First, 1 mmol Bi(NO3)3·5H2O is dissolved in 15 mL of HNO3 (2 mol / L) solution to form solution A. At the same time, 1 mmol KCl is dissolved in 30 mL of deionized water to form solution B. Solution B is added dropwise to solution A under continuous stirring to form solution C. Stirring is maintained for 30 min (300 rpm). Then, the pH of the above homogeneous liquid slurry is adjusted to pH=5 with NaOH (1 mol / L) solution. Stirring is maintained for 2 h. Next, the above mixture is transferred to a 100 mL polytetrafluoroethylene autoclave and kept at 160 °C for 18 h. Then, the precipitate is collected by filtration and washing. Finally, the precipitate is dried in air at 80 °C for 12 h to obtain a white product, which is BiOCl.

[0069] Example 8

[0070] The specific steps are the same as those in Example 1, except that the photocatalyst in step (3) of Example 1 is replaced with self-made BiVO4. The specific preparation method is as follows: First, 1 mmol Bi(NO3)3·5H2O is dissolved in 15 mL of HNO3 (2 mol / L) solution to form solution A. At the same time, 1 mmol NH4VO3 is dissolved in 15 mL of deionized water to form solution B. Solution B is added dropwise to solution A under continuous stirring to form solution C. Stirring is maintained for 30 min (300 rpm). Then, the pH of the above homogeneous liquid slurry is adjusted to pH=7 with ammonia water (v(NH3·H2O):v(H2O)=1:2). Stirring is maintained for 2 h. Next, the above mixture is transferred to a 100 mL polytetrafluoroethylene autoclave and kept at 180℃ for 24 h. Then, the precipitate is collected by filtration and washing. Finally, the precipitate is dried in air at 80℃ for 12 h to obtain the yellow product, which is BiVO4.

[0071] Example 9

[0072] The specific steps are the same as those in Example 1, except that the photocatalyst in step (3) of Example 1 is replaced with self-made Bi2MoO6. The specific preparation method is as follows: First, 1 mmol Bi(NO3)3·5H2O is dissolved in 15 mL of HNO3 (2 mol / L) solution to form solution A. At the same time, 0.5 mmol Na2MoO4·H2O is dissolved in 15 mL of deionized water to form solution B. Solution B is added dropwise to solution A under continuous stirring to form solution C. Stirring is maintained for 30 min (300 rpm). Then, the pH of the above homogeneous liquid slurry is adjusted to pH=5 with NaOH (1 mol / L) solution. Stirring is maintained for 2 h. Next, the above mixture is transferred to a 100 mL polytetrafluoroethylene autoclave and kept at 160℃ for 18 h. Then, the precipitate is collected by filtration and washing. Finally, the precipitate is dried in air at 80℃ for 12 h to obtain the yellow product, which is Bi2MoO6.

[0073] Example 10

[0074] The specific steps are the same as those in Example 1, except that the photocatalyst in step (3) of Example 1 is replaced with self-made ZnO. The specific preparation method is as follows: ZnO is prepared by low-temperature hydrothermal method. Take 25 mL of 0.025 mol / L zinc nitrate and 25 mL of 0.025 mol / L hexamethylenetetramine solution, mix and stir for 10 min (300 rpm), then place the suspension in the reaction vessel, react at 90℃ for 5 h, and the powder obtained by filtration and drying after reaction is ZnO.

[0075] Example 11

[0076] The specific steps are the same as those in Example 1, except that the photocatalyst in step (3) of Example 1 is replaced with self-made ZnS. The specific preparation method is as follows: using zinc acetate dihydrate (CH3COO)2Zn·2H2O as the zinc source, thioacetamide (C2H5NS) as the sulfur source, and hexadecyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfonate (SDS) as surfactants, nano ZnS is prepared by hydrothermal synthesis. First, 100 mg of SDS and CTAB surfactants are weighed and their ratio is 1:2. Then, the weighed surfactants are poured into a container containing 50 mL of deionized water. The solution was placed in a beaker of water and stirred on a magnetic stirrer for 30 minutes (300 rpm). 2 mmol of (CH3COO)2Zn·2H2O and 2 mmol of C2H5NS were accurately weighed and placed in the beaker, and stirred on a magnetic stirrer for 1 hour. The clear solution after stirring was poured into a reaction vessel and reacted at 120℃ for 12 hours. After the hydrothermal reaction, the mixture was cooled to room temperature, and the supernatant in the reaction vessel was discarded. The precipitate was then washed repeatedly with anhydrous ethanol and deionized water. Finally, the washed precipitate was placed in an oven at 80℃ for drying for 12 hours to obtain ZnS powder.

[0077] Example 12

[0078] The specific steps are the same as those in Example 1, except that the photocatalyst in step (3) of Example 1 is replaced with self-made WO3. The specific preparation method is as follows: Specific synthesis method: 2.5g H2WO4 was dissolved in 60 mL of deionized water and 20 mL of 30 wt.% hydrogen peroxide (H2O2). The solution was then heated and stirred in a 95 °C water bath (300 rpm) until it became clear. Deionized water was added to the clear solution and the solution was diluted to 200 mL to obtain a 0.05 mol / L peroxytungstic acid (PTA) precursor solution. 6 mL of the PTA precursor solution was taken and 1 mL of hydrochloric acid (6 mol / L) and 30 mL of a mixture of acetonitrile and deionized water were added to it. The volume ratio of deionized water to acetonitrile was set to 1:1. The mixture was then stirred at room temperature for 30 min (300 rpm). Finally, the well-mixed solution was transferred to a 100 mL reactor and reacted in an oven at 180 °C for 12 h. After the reaction, the precipitate was washed repeatedly with anhydrous ethanol and deionized water. Finally, the washed precipitate was placed in an oven at 60 °C for drying for 12 h to obtain WO3 powder.

[0079] Example 13

[0080] The specific steps are the same as those in Example 1, except that the photocatalyst in step (3) of Example 1 is replaced with self-made TiO2. Pure TiO2 is prepared by sol-gel method. The specific preparation method is as follows: 24 mL of anhydrous ethanol, 2 mL of CH3COOH and 3 mL of tetrabutyl titanate are added to a beaker in sequence and stirred evenly to form solution A. 28 mL of ethanol aqueous solution (V(C2H5OH):V(H2O)=1:1) is added to the beaker, and then 80 μL of concentrated hydrochloric acid is added and stirred evenly to form solution B. Using a peristaltic pump, solution B is slowly added dropwise to solution A and the stirring speed is reduced. The mixture is slowly stirred for 12 h to form TiO2 gel. The obtained gel is placed in an 80℃ oven to dry for 12 h and then ground to below 74 μm. After grinding evenly, the powder sample is placed in a ash dish and spread evenly. Then it is placed in a muffle furnace and calcined at 600℃ for 2 h (the heating rate of the muffle furnace is 5℃ / min). The white powder after calcination is TiO2.

[0081] Comparative Example 1

[0082] The specific steps are the same as those in Example 1, except that NaCl was not added in step (2) of Example 1. The main purpose of this step is to prove that Cl ions need to coordinate with noble metals to form complexes during the reaction process.

[0083] Comparative Example 2

[0084] The specific steps are the same as those in Example 1, except that step (3) in Example 1 did not include a photocatalyst. The main purpose of this step was to prove that the reaction process is a photocatalytic leaching process and requires a photocatalyst.

[0085] Performance testing

[0086] Figures 1-3 The figures show a comparison of the leaching rates of Pd, Pt, and Rh in Examples 1-13 and Comparative Examples 1-2, respectively.

[0087] from Figure 1 As can be seen, the leaching rate of Pd in ​​the platinum-palladium-rhodium-rich automotive waste three-way catalyst of the present invention is 57.94-99.97%, while the leaching rate of Pd in ​​Comparative Example 1 is 2.41% and the leaching rate of Pd in ​​Comparative Example 2 is 24.13%. It is evident that the present invention can significantly improve the leaching rate of Pd in ​​the platinum-palladium-rhodium-rich automotive waste three-way catalyst.

[0088] from Figure 2 As can be seen, the leaching rate of Pt in platinum-palladium-rhodium-rich automotive waste three-way catalysts of the present invention is 48.89-99.45%, while the leaching rate of Pt in Comparative Example 1 is 0.00% and the leaching rate of Pt in Comparative Example 2 is 10.30%. It is evident that the present invention can significantly improve the leaching rate of Pt in platinum-palladium-rhodium-rich automotive waste three-way catalysts.

[0089] from Figure 3 As can be seen, the leaching rate of Rh in platinum-palladium-rhodium-rich automotive waste three-way catalysts of the present invention is 31.15-95.03%, basically reaching more than 70%, while the leaching rate of Rh in Comparative Example 1 is 0.00% and the leaching rate of Rh in Comparative Example 2 is 40.28%. It can be seen that the present invention can significantly improve the leaching rate of Rh in platinum-palladium-rhodium-rich automotive waste three-way catalysts.

[0090] In summary, the leaching method provided by this invention can significantly improve the leaching rate of Pd, Pt and Rh in platinum-palladium-rhodium-rich automotive waste three-way catalysts.

[0091] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for photocatalytic leaching of noble metals from a chloride brine phase, characterized in that, Includes the following steps: Waste rich in precious metals, a solution containing chloride salts, and a photocatalyst are mixed. The resulting slurry is subjected to photocatalytic leaching under light conditions, followed by solid-liquid separation to obtain a leachate containing precious metals.

2. The method according to claim 1, characterized in that, The precious metals in the waste rich in precious metals include one or more of ruthenium, rhodium, palladium, osmium, iridium and platinum.

3. The method according to claim 1, characterized in that, The chloride salt is a chlorine-containing inorganic salt; the chlorine-containing inorganic salt includes one or more of sodium chloride, potassium chloride, magnesium chloride, ammonium chloride, calcium chloride, aluminum chloride, and lithium chloride.

4. The method according to claim 1, characterized in that, The photocatalyst includes organic photocatalysts and / or inorganic photocatalysts; the organic photocatalyst includes one or more of g-C3N4, perylene diimide, and perylene tetracarboxylic acid; the inorganic photocatalyst includes one or more of BiOCl, BiVO4, Bi2MoO6, ZnO, ZnS, WO3, and TiO2.

5. The method according to claim 1, characterized in that, The wavelength of the illumination is 150–1500 nm; the intensity of the illumination is ≥100 μW / cm². 2 The illumination time is 0.01 to 3600 hours.

6. The method according to claim 1, characterized in that, The concentration of chloride in the chloride-containing solution is 0.001–10000 g / L.

7. The method according to claim 1 or 6, characterized in that, The ratio of the mass of the precious metal-rich waste to the volume of the chloride-containing solution is 1 g: (1-1000) mL.

8. The method according to claim 1, characterized in that, The mass ratio of the precious metal-rich waste to the photocatalyst is 0.1 to 500:

1.

9. The method according to claim 1, characterized in that, The pH value of the chloride-containing solution is <7.

10. The method according to claim 1, characterized in that, Before mixing the waste material rich in precious metals, the chloride-containing salt solution, and the photocatalyst, the process further includes: sequentially crushing, grinding, and sieving the waste material rich in precious metals to obtain the waste powder rich in precious metals; the particle size of the waste powder rich in precious metals is ≥0.5μm.

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