Application of alkyl chain quaternary ammonium salt compound as platinum group metal precipitator and platinum group metal recovery method

Abstract

The invention discloses application of an alkyl chain quaternary ammonium salt compound as a platinum group metal precipitator and a platinum group metal recovery method, and belongs to the technical field of precious metal secondary resource recycling. According to the method, the platinum group metal precipitant and the aqueous solution containing platinum group metal (platinum, iridium, rhodium and palladium) ions are mixed, target metal is selectively precipitated through the coordination effect and the steric hindrance effect of the platinum group metal precipitant, the high-purity platinum group metal is obtained through solid-liquid separation and calcination, the breakthrough of an efficient precious metal recovery technology is achieved, and the method is suitable for industrial production. And the recycling efficiency of precious metal resources is remarkably improved. The method solves the technical problems of large amount of precipitant, poor selectivity and high residual concentration of tail liquid in the traditional process, has the advantages of efficient selectivity, simplified process flow, environmental friendliness, high recovery efficiency, improved resource utilization rate and the like, and provides an innovative solution for efficient cyclic utilization of noble metal resources.

Description

Technical Field

[0001] The present invention belongs to the technical field of recycling of precious metal secondary resources, and specifically relates to the application of an alkyl chain quaternary ammonium salt compound as a precipitant for platinum group metals and a method for recovering platinum group metals. Background Art

[0002] Platinum group metals (including ruthenium, rhodium, palladium, osmium, iridium, and platinum), as irreplaceable strategic resources, play an irreplaceable and important role in key fields such as new energy, high-end manufacturing, and environmental protection. The crustal abundance of platinum group metals is less than one in a hundred million, and primary ores are extremely scarce.

[0003] Current platinum group metal recovery processes mainly include solvent extraction and direct precipitation. Although solvent extraction can achieve high recovery rates, it has defects such as high toxicity, flammability, and explosiveness of the extractant, strong equipment corrosion, and complex process flow and high operating costs due to multi-stage extraction operations. In contrast, direct precipitation is more promising for industrial applications due to its simple process and environmental friendliness. However, traditional precipitants such as ammonium chloride are commonly used in the existing technology, which have technical bottlenecks such as poor selectivity, large dosage of precipitant, and high residual concentration in the tail liquid, seriously restricting the recovery efficiency and economy. Summary of the Invention

[0004] In view of the technical defects such as poor selectivity, large consumption of precipitant, and high residual concentration in the tail liquid existing in the current platinum group metal recovery process, the present invention provides an application of an alkyl chain quaternary ammonium salt compound as a precipitant for platinum group metals and a method for recovering platinum group metals. The platinum group metal precipitant can achieve a breakthrough in high-efficiency precious metal recovery technology and significantly improve the recycling efficiency of precious metal resources.

[0005] To achieve the above object, based on the coordination characteristics and steric hindrance effect of platinum group metal complex anions, the present invention provides an application of a series of alkyl chain quaternary ammonium salt compounds as precipitants for platinum group metals. This series of alkyl chain quaternary ammonium salt compounds includes single long-chain alkyl trimethyl quaternary ammonium salts: C8-C 22 alkyl trimethyl ammonium chloride ([C n H 2n+1 (CH3)3N]Cl, n = 8 - 22) and its bromide ([C n H 2n+1 (CH3)3N]Br, n = 8 - 22); double long-chain alkyl dimethyl ammonium halides: C8-C 18 dialkyl dimethyl ammonium chloride ([(C n H 2n+1 )2(CH3)2N]Cl, n = 8 - 18) and its bromide ([(C n H 2n+1 )2(CH3)2N]Br, n = 8 - 18), dodecyl trimethyl ammonium hydroxide ([C12 H 25 (CH3)3N]OH), hexadecyltrimethylammonium hydroxide ([C 16 H 33 (CH3)3N]OH); polymethyl quaternary ammonium salts: hexamethylhexanediammonium bromide ((CH2)6[N(CH3)3]2Br2), hexamethylhexanediammonium chloride ((CH2)6[N(CH3)3]2Cl2), decamethonium bromide ((CH2) 10 [N(CH3)3]2Br2), hexamethylhexanediammonium hydroxide ([(CH2)6[N(CH3)3]2(OH)2).

[0006] The method for recovering platinum group metals according to the present invention comprises the following steps:

[0007] (a) A platinum group metal precipitant and platinum group metals are added to an aqueous solution containing platinum, iridium, rhodium or palladium ions with a hydrochloric acid concentration of 0 - 6 mol / L in a molar ratio of 2 - 50:1;

[0008] (b) The solution obtained in step (a) is stirred at 4 - 30 °C for 10 - 30 minutes, then allowed to settle for 1 - 12 hours, and finally the precipitate is separated by centrifugation or suction filtration;

[0009] (c) The precipitate obtained in step (b) is calcined at 500 - 900 °C (the heating rate during calcination is 1 - 10 °C / min) for 30 - 300 minutes in a certain atmosphere (such as air, hydrogen, argon, nitrogen, etc.) to obtain high-purity platinum group metals.

[0010] In the present invention, a platinum group metal precipitant is mixed with an aqueous solution containing platinum group metal (platinum, iridium, rhodium, palladium) ions. By utilizing the coordination effect and steric hindrance effect of the platinum group metal precipitant, the target metal is selectively precipitated, and high-purity platinum group metals are obtained through solid-liquid separation and calcination. The present invention uses an inductively coupled plasma optical emission spectrometer (ICP-OES) to quantitatively analyze the solution containing platinum, iridium, rhodium or palladium ions before and after treatment, and the recovery rate of platinum group metals can be measured. The composition of the product after calcination of the precipitate can be determined by X-ray diffraction analysis (XRD). The present invention solves the technical problems of large consumption of precipitants, poor selectivity and high residual concentration in the tail liquid in the traditional process, and has the advantages of simplified process flow, environmental friendliness, high recovery efficiency, etc., providing an innovative solution for the efficient recycling of precious metal resources.

[0011] Beneficial effects

[0012] 1. High efficiency and selectivity: It can achieve high-selectivity precipitation of platinum group metals and effectively separate coexisting impurity metals;

[0013] 2. Simplified process flow: Metal recovery can be completed through a single-stage precipitation reaction, eliminating the need for complex extraction or multi-stage purification steps;

[0014] 3. Environmental friendliness: Avoid using toxic organic solvents, reducing the difficulty of wastewater treatment and environmental risks;

[0015] 4. Improved resource utilization rate: Significantly reduce the dosage of precipitants, improving the recovery efficiency and economy of precious metals. Brief Description of the Drawings

[0016] Figure 1 It is the XRD pattern of the product after calcination in Example 1. The positions of its diffraction peaks are consistent with the standard PDF card of Pt, proving that the product is high-purity platinum metal;

[0017] Figure 2 It is the XRD pattern of the product after calcination in Example 2. The positions of its diffraction peaks are consistent with the standard PDF card of Ir, proving that the product is high-purity iridium metal;

[0018] Figure 3 It is the XRD pattern of the product after calcination in Example 3. The positions of its diffraction peaks are consistent with the standard PDF card of Rh, proving that the product is high-purity rhodium metal;

[0019] Figure 4 It is the XRD pattern of the product after calcination in Example 4. The positions of its diffraction peaks are consistent with the standard PDF card of Pd, proving that the product is high-purity palladium metal. Detailed Embodiments

[0020] The present invention will be further described in conjunction with the embodiments and the drawings. However, the protection scope of the present invention includes but is not limited to the following embodiments. Changes and adjustments made without departing from the gist and scope of the present invention will also be included in the protection scope of the present invention.

[0021] The present invention will be described below with reference to specific embodiments. The numerical values of the process conditions taken in the following embodiments are all exemplary, and their available numerical ranges are as shown in the foregoing invention content. For process parameters not specifically noted, reference may be made to conventional techniques.

[0022] Example 1

[0023] Platinum recovery: Weigh 465 mg of sodium chloroplatinate (analytical pure, ≥99%) and dissolve it in 300 mL of deionized water, stirring until completely dissolved; then measure 167 mL of concentrated hydrochloric acid with a mass fraction of 37% and slowly add it thereto; then transfer it to a 1000 mL volumetric flask and make up the volume to the scale line with deionized water, and shake well to obtain an aqueous solution containing 200 mg / L of platinum and a hydrochloric acid concentration of 2 mol / L. Using cetyltrimethylammonium chloride ([C 16 H 33(CH3)3N]Cl) was used as a precipitant for platinum group metals for the recovery experiment. In the specific operation, cetyltrimethylammonium chloride was added to the above-mentioned platinum-containing aqueous solution at a molar ratio of 10:1 to platinum, stirred at 20 °C for 30 minutes, then allowed to settle for 6 hours, and finally the precipitate was separated by filtration. The obtained precipitate was placed in a tubular furnace and calcined at 600 °C for 120 minutes (heating rate 10 °C / min) under an air atmosphere. The product after calcination was determined to be high-purity platinum metal powder by XRD( Figure 1 ). ICP-OES was used to quantitatively analyze the solution before and after treatment, and the platinum recovery rate was measured to be 99.3%. Platinum recovery rate (%) = (platinum mass in the original solution - platinum mass in the tail solution) / platinum mass in the original solution × 100%.

[0024] Based on the same conditions as in Example 1, a comparative experiment was carried out by changing the type of precipitant. As shown in Table 1, cetyltrimethylammonium chloride showed the highest recovery rate, significantly superior to other quaternary ammonium salt precipitants.

[0025] Table 1: Recovery rate data of platinum by different quaternary ammonium salt precipitants

[0026]

[0027]

[0028] Example 2

[0029] Iridium recovery: Weigh 503 mg of potassium hexachloroiridate (analytical pure, ≥99%), dissolve it in 300 mL of deionized water, and stir until completely dissolved; then measure 167 mL of concentrated hydrochloric acid with a mass fraction of 37% and slowly add it; then transfer it to a 1000 mL volumetric flask, and make up to the mark with deionized water, shake well to obtain an aqueous solution containing 200 mg / L of iridium and a hydrochloric acid concentration of 2 mol / L. Tetradecyltrimethylammonium chloride ([C 14 H 29 (CH3)3N]Cl) was used as a precipitant for the recovery experiment. In the specific operation, tetradecyltrimethylammonium chloride was added to the above-mentioned iridium-containing solution at a molar ratio of 10:1 to iridium, stirred at 20 °C for 30 minutes, then allowed to settle for 10 hours, and finally the precipitate was separated by filtration. The obtained precipitate was placed in a tubular furnace and calcined at 900 °C for 60 minutes (heating rate 10 °C / min) under an air atmosphere. The product after calcination was determined to be high-purity iridium metal powder by XRD( Figure 2 ). ICP-OES was used to quantitatively analyze the solution before and after treatment, and the iridium recovery rate was measured to be 99.1%. Iridium recovery rate (%) = (iridium mass in the original solution - iridium mass in the tail solution) / iridium mass in the original solution × 100%.

[0030] Based on the same conditions as in Example 2, comparative experiments were carried out by changing the type of precipitant. As shown in Table 2, tetradecyltrimethylammonium chloride showed the highest recovery rate, significantly superior to other quaternary ammonium salt precipitants.

[0031] Table 2: Recovery rate data of iridium by different quaternary ammonium salt precipitants

[0032] Metal precipitant Iridium recovery rate (%) <![CDATA[Octyltrimethylammonium chloride ([C8H 17 (CH3)3N]Cl)]]> 69.3 <![CDATA[Decyltrimethylammonium chloride ([C 10 H 21 (CH3)3N]Cl)]]> 85.2 <![CDATA[Dodecyl trimethyl ammonium chloride ([C 12 H 25 (CH3)3N]Cl)]]> 95.9 <![CDATA[Tetradecyltrimethylammonium chloride ([C 14 H 29 (CH3)3N]Cl)]]> 99.1 <![CDATA[Tetradecyltrimethylammonium bromide ([C 14 H 29 (CH3)3N]Br)]]> 96.2 <![CDATA[Cetyltrimethylammonium chloride ([C 16 H 33 (CH3)3N]Cl)]]> 88.6 <![CDATA[Cetyltrimethylammonium bromide ([C 16 H 33 (CH3)3N]Br)]]> 86.5 <![CDATA[Dodecyldimethylammonium chloride ([(C 12 H 25 )2(CH3)2N]Cl2)]]> 69.9 <![CDATA[Hexamethylhexamethylenediammonium chloride ((CH2)6[N(CH3)3]2Cl2)]]> 83.7 <![CDATA[Decamethonium bromide ((CH2) 10 [N(CH3)3]2Br2)]]> 92.1

[0033] Example 3

[0034] Rhodium recovery: Weigh 1263 mg of potassium hexachlororhodate (analytical pure, ≥99%) and dissolve it in 200 mL of deionized water, stirring until completely dissolved; then measure 333 mL of concentrated hydrochloric acid with a mass fraction of 37% and slowly add it; then transfer it to a 1000 mL volumetric flask and make up to the mark with deionized water, shake well to obtain an aqueous solution containing 300 mg / L of rhodium and a hydrochloric acid concentration of 4 mol / L. Dodecyltrimethylammonium chloride ([C 12 H 25 (CH3)3N]Cl) was used as the precipitant for the recovery experiment. In the specific operation, dodecyltrimethylammonium chloride and iridium were added to the above rhodium-containing solution in a molar ratio of 30:1, stirred at 20 °C for 20 minutes, then settled for 10 hours, and finally the precipitate was separated by filtration. The obtained precipitate was placed in a tube furnace and calcined at 600 °C for 120 minutes (heating rate 10 °C / min) in an air atmosphere. The product after calcination was determined to be high-purity rhodium metal powder by XRD ( Figure 3 ). ICP-OES was used to quantitatively analyze the solution before and after treatment, and the rhodium recovery rate was measured to be 98.3%. Rhodium recovery rate (%) = (rhodium mass in the original solution - rhodium mass in the tail solution) / rhodium mass in the original solution × 100%.

[0035] Based on the same conditions as in Example 3, comparative experiments were carried out by changing the type of precipitant. As shown in Table 3, dodecyltrimethylammonium chloride showed the highest recovery rate, significantly superior to other quaternary ammonium salt precipitants. The recovery rate data of each precipitant for rhodium are shown in Table 3:

[0036] Table 3: Recovery rate data of rhodium by different quaternary ammonium salt precipitants

[0037] Metal precipitant Rhodium recovery rate (%) <![CDATA[Octyltrimethylammonium chloride ([C8H 17 (CH3)3N]Cl)]]> 79.3 <![CDATA[Decyltrimethylammonium chloride ([C 10 H 21 (CH3)3N]Cl)]]> 91.2 <![CDATA[Dodecyl trimethyl ammonium chloride ([C 12 H 25 (CH3)3N]Cl)]]> 98.3 <![CDATA[Ammonium dodecyl trimethyl bromide ([C 12 H 25 (CH3)3N]Br)]]> 95.1 <![CDATA[Dodecyltrimethylammonium hydroxide ([C 12 H 25 (CH3)3N]OH)]]> 95.7 <![CDATA[Tetradecyltrimethylammonium chloride ([C 14 H 29 (CH3)3N]Cl)]]> 82.4 <![CDATA[Tetradecyltrimethylammonium bromide ([C 14 H 29 (CH3)3N]Br)]]> 78.7 <![CDATA[Cetyltrimethylammonium chloride ([C 16 H 33 (CH3)3N]Cl)]]> 67.3 <![CDATA[Dicetyldimethylammonium chloride ([(C 16 H 33 )2(CH3)2N]Cl2)]]> 77.3 <![CDATA[Hexamethylhexamethylenediammonium chloride ((CH2)6[N(CH3)3]2Cl2)]]> 65.8

[0038] Example 4

[0039] Palladium Recovery: Weigh 830 mg of potassium tetrachloropalladate (analytical pure, ≥99%) and dissolve it in 300 mL of deionized water, stirring until completely dissolved. Then measure 167 mL of concentrated hydrochloric acid with a mass fraction of 37% and slowly add it thereto. Transfer the solution to a 1000 mL volumetric flask and make up the volume to the calibration line with deionized water, and shake well to obtain an aqueous solution containing 300 mg / L of palladium and a hydrochloric acid concentration of 2 mol / L. Use dodecyltrimethylammonium chloride ([C 10 H 23 (CH3)3N]Cl) as a precipitant for the recovery experiment. In the specific operation, add dodecyltrimethylammonium chloride and iridium to the above palladium-containing solution at a molar ratio of 30:1, stir at 20 °C for 30 minutes, then sediment for 6 hours, and finally filter to separate the precipitate. Place the obtained precipitate in a tube furnace and calcine it at 600 °C for 60 minutes (heating rate 10 °C / min) under a hydrogen atmosphere. The product after calcination can be determined to be high-purity palladium metal powder by XRD( Figure 4 ). Use ICP-OES to quantitatively analyze the solution before and after treatment, and the measured palladium recovery rate reaches 98.3%. Palladium recovery rate (%) = (mass of palladium in the original solution – mass of palladium in the tail solution) / mass of palladium in the original solution × 100%.

[0040] Based on the same conditions as in Example 4, comparative experiments were carried out by changing the type of precipitant. As shown in Table 4, dodecyltrimethylammonium chloride showed the highest recovery rate, significantly superior to other quaternary ammonium salt precipitants.

[0041] Table 4: Palladium recovery rate data of different quaternary ammonium salt precipitants

[0042] Metal precipitant Palladium recovery rate (%) <![CDATA[n-Octyltrimethylammonium chloride ([C8H 17 (CH3)3N]Cl)]]> 82.6 <![CDATA[Decyl trimethyl ammonium chloride ([C 10 H 21 (CH3)3N]Cl)]]> 98.7 <![CDATA[Decyltrimethylammonium bromide ([C 10 H 21 (CH3)3N]Br)]]> 94.5 <![CDATA[Dodecyl trimethyl ammonium chloride ([C 12 H 25 (CH3)3N]Cl)]]> 91.4 <![CDATA[Ammonium dodecyl trimethyl bromide ([C 12 H 25 (CH3)3N]Br)]]> 85.6 <![CDATA[Tetradecyltrimethylammonium chloride ([C 14 H 29 (CH3)3N]Cl)]]> 79.2 <![CDATA[Tetradecyltrimethylammonium bromide ([C 14 H 29 (CH3)3N]Br)]]> 71.9 <![CDATA[Cetyltrimethylammonium chloride ([C 16 H 33 (CH3)3N]Cl)]]> 63.5 <![CDATA[Dicetyldimethylammonium chloride ([(C 16 H 33 )2(CH3)2N]Cl2)]]> 69.7 <![CDATA[Hexamethylhexamethylenediammonium chloride ((CH2)6[N(CH3)3]2Cl2)]]> 78.8

[0043] In summary, the platinum group metal precipitant described in the present invention has a good recovery rate for platinum group metals.

Claims

1. Application of an alkyl chain quaternary ammonium salt compound in use as a platinum group metal precipitant, characterized in that: The alkyl chain quaternary ammonium salt compound is one of single long-chain alkyl trimethyl quaternary ammonium salt, double long-chain alkyl dimethyl ammonium halide, dodecyl trimethyl ammonium hydroxide, cetyl trimethyl ammonium hydroxide, and polymethyl quaternary ammonium salt.

2. Use of an alkyl chain quaternary ammonium salt compound as defined in claim 1 as a precipitant for platinum group metals, characterized in that: The alkyl chain quaternary ammonium salt compound is C8-C 22 alkyltrimethylammonium chloride ([C n H 2n+1 (CH3)3N]Cl, n = 8 - 22) and its bromide ([C n H 2n+1 (CH3)3N]Br, n = 8 - 22), C8-C 18 dialkyldimethylammonium chloride ([(C n H 2n+1 )2(CH3)2N]Cl, n = 8 - 18) and its bromide ([(C n H 2n+1 )2(CH3)2N]Br, n = 8 - 18), dodecyltrimethylammonium hydroxide ([C 12 H 25 (CH3)3N]OH), cetyltrimethylammonium hydroxide ([C 16 H 33 (CH3)3N]OH), hexamethylhexanediammonium bromide ((CH2)6[N(CH3)3]2Br2), hexamethylhexanediammonium chloride ((CH2)6[N(CH3)3]2Cl2), decamethonium bromide ((CH2) 10 [N(CH3)3]2Br2), hexamethylhexanediammonium hydroxide ([(CH2)6[N(CH3)3]2(OH)2).

3. Use of an alkyl chain quaternary ammonium salt compound as claimed in claim 1 as a precipitant for platinum group metals, characterized in that: The platinum group metal is one of platinum, iridium, rhodium, and palladium.

4. A method for recovering platinum group metals, comprising the following steps: (a) Adding the alkyl chain quaternary ammonium salt compound as a platinum group metal precipitant described in Claim 1 or 2 and the platinum group metal to an aqueous solution containing platinum, iridium, rhodium, or palladium ions with a hydrochloric acid concentration of 0 - 6 mol / L in a molar ratio of 2 - 50:1; (b) Stirring the solution obtained in step (a) at 4 - 30 °C for 10 - 30 minutes, then allowing it to settle for 1 - 12 hours, and finally separating the precipitate by centrifugation or suction filtration; (c) Calcining the precipitate obtained in step (b) in a certain atmosphere (such as air, hydrogen, argon, nitrogen, etc.) at 500 - 900 °C for 30 - 300 minutes to obtain high-purity platinum group metals.

5. The platinum group metal recovery method according to claim 4, characterized in that: It is an atmosphere of air, hydrogen, argon, or nitrogen.

6. The platinum group metal recovery method according to claim 4, wherein: The heating rate during calcination is 1 - 10 °C / min.

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