Method for separating and purifying palladium from alumina catalyst particles

Abstract

The invention discloses a method for separating and purifying palladium from aluminum oxide catalyst particles, and aims to separate and purify palladium on the premise of not damaging the aluminum oxide catalyst particles, and the method comprises the following steps: placing the aluminum oxide catalyst particles in a strong acid solution containing an oxidizing agent, and leaching palladium to obtain a palladium-containing solution; in the leaching process, an air stirrer is arranged in the strong acid solution, and the air stirrer introduces gas into the strong acid solution to stir the strong acid solution; the method belongs to the technical field of precious metal recovery.

Description

Technical Field

[0001] The present invention belongs to the technical field of precious metal recovery, and more specifically, relates to a method for separating and purifying palladium from aluminum oxide catalyst particles. Background Art

[0002] Before the palladium-containing alumina catalyst particles are dissolved by traditional methods, the materials need to go through processes such as grinding, pre-calcination, smelting and capturing, and then wet leaching and purification, which results in low palladium dissolution rate and high impurity content, making wet purification difficult;

[0003] Moreover, in this method, the structure of the alumina catalyst particles will be destroyed and cannot be recycled, resulting in material waste. Summary of the invention

[0004] The main purpose of the present invention is to provide a method for separating and purifying palladium from alumina catalyst particles, aiming to separate and purify palladium without destroying the alumina catalyst particles.

[0005] According to a first aspect of the present invention, there is provided a method for separating and purifying palladium from alumina catalyst particles, comprising the following steps:

[0006] Step 1: placing aluminum oxide catalyst particles in a strong acid solution containing an oxidant to leach palladium to obtain a palladium-containing solution; during the leaching process, an air agitator is provided in the strong acid solution to introduce gas into the strong acid solution to stir the strong acid solution;

[0007] Step 2: Extracting palladium from a palladium-containing solution.

[0008] The present invention utilizes the gas introduced by the air agitator to stir the strong acid solution, which can effectively dissolve the palladium on the alumina catalyst particles without destroying the alumina catalyst particles, and the palladium leaching rate is higher.

[0009] In the above-mentioned method for separating and purifying palladium from alumina catalyst particles, the air agitator includes a connecting pipe and a coil, the connecting pipe connects the coil with an external air generator, the coil is spiral, and a plurality of air outlets are provided on the coil.

[0010] In the above-mentioned method for separating and purifying palladium from alumina catalyst particles, the gas outlet holes include first gas outlet holes, and the gas outlet direction of the first gas outlet holes is parallel to the axial direction of the coil.

[0011] In the above-mentioned method for separating and purifying palladium from alumina catalyst particles, the gas outlet hole includes a second gas outlet hole, and the angle between the gas outlet direction of the second gas outlet hole and the axis of the coil is 45°.

[0012] In the above method for separating and purifying palladium from alumina catalyst particles, the air agitator discharges gas at intervals of 4 to 6 seconds, the discharge time is 4 to 6 seconds, and the gas flow rate during discharge is 9 to 11 m / s.

[0013] Preferably, the air agitator releases air at intervals of 5 seconds.

[0014] Preferably, the air agitator discharges air for 5 seconds each time.

[0015] Preferably, the gas flow rate of the air agitator when exhausting gas is 10m / s.

[0016] In the above-mentioned method for separating and purifying palladium from alumina catalyst particles, in step 1, during the leaching process, an ultrasonic vibration rod is provided in the strong acid solution to promote the dissolution of palladium on the alumina catalyst particles.

[0017] Preferably, the frequency of the ultrasonic vibration rod is 65 Hz, and the ultrasonic length of the ultrasonic vibration rod is 10 mm.

[0018] In the above-mentioned method for separating and purifying palladium from alumina catalyst particles, the oxidant is hydrogen peroxide or a mixture of hydrogen peroxide and sodium chlorate.

[0019] Preferably, the strong acid solution containing the oxidant includes pure water, hydrochloric acid solution, hydrogen peroxide solution and sodium chlorate solution. Before performing step 1, the pure water, hydrochloric acid solution and hydrogen peroxide solution are placed in a container, and the aluminum oxide catalyst particles are divided into multiple portions; step 1 includes the following steps:

[0020] Step 11: Add sodium chlorate solution into the container; allow the sodium chlorate solution to be diluted in the solution first;

[0021] Step 12: Add a portion of alumina catalyst particles into the hanging basket, immerse the hanging basket into the container, and take out the hanging basket after immersion for a predetermined time;

[0022] Step 13: Repeat steps 11 to 12 until all the alumina catalyst particles are added;

[0023] Step 14: Let the hanging basket be immersed in the container, heat the solution in the container to 50°C ~ 60°C, and keep it warm for 2 hours; then heat the solution in the container to 85°C ~ 95°C, and keep it warm for 30 minutes; then cool the solution in the container to below 50°C, take out the hanging basket containing alumina catalyst particles, rinse it with pure water, combine the rinse liquid and the solution in the container to obtain a palladium-containing solution.

[0024] Preferably, the mass fraction of the hydrochloric acid solution is 35%, and the mass fraction of the hydrogen peroxide solution is 50%;

[0025] The ratio of the volume of pure water to the total volume of the alumina catalyst particles is 1-5:1, the ratio of the mass of the hydrochloric acid solution to the total mass of the alumina catalyst particles is 0.5-1.5:1, and the ratio of the mass of the hydrogen peroxide solution to the total mass of the alumina catalyst particles is 1:55-65:;

[0026] The solubility of the sodium chlorate solution is 0.1 g / ml, and the ratio of the mass of the sodium chlorate solution added each time to the mass of each portion of the aluminum oxide catalyst particles is 1:20-30.

[0027] Preferably, the ratio of the volume of pure water to the total volume of the alumina catalyst particles is 3:1.

[0028] Preferably, the ratio of the mass of the hydrochloric acid solution to the total mass of the alumina catalyst particles is 1:1.

[0029] Preferably, the ratio of the mass of the hydrogen peroxide solution to the total mass of the alumina catalyst particles is 1:60.

[0030] Preferably, the ratio of the mass of the sodium chlorate solution added each time to the mass of each portion of the alumina catalyst particles is 1:25.

[0031] Preferably, the strong acid solution containing the oxidizing agent comprises aqua regia.

[0032] In the above method for separating and purifying palladium from alumina catalyst particles, the step 2 comprises the following steps:

[0033] Step 21: filtering out base metal cations in the palladium-containing solution to obtain a first filtrate; since the base metal cation impurities are removed, the palladium product obtained after subsequent purification has a relatively high purity;

[0034] Step 22: adding a 35% hydrochloric acid solution, sodium chlorate and ammonium chloride to the first filtrate, wherein the ratio of the hydrochloric acid solution to the palladium in the palladium-containing solution is 1-2L:1kg, the ratio of the sodium chlorate to the palladium in the palladium-containing solution is 0.4-1.2kg:1kg, and the ratio of the ammonium chloride to the palladium in the palladium-containing solution is 10-20kg:1kg; filtering to obtain ammonium chloropalladate solid;

[0035] Step 23: dissolving the ammonium chloropalladate solid into an aqueous ammonia solution, and filtering to obtain a second filtrate;

[0036] Step 24: The pH of the second filtrate is adjusted to 8-9 with aqueous ammonia solution, and then added dropwise to hydrazine hydrate for reduction to obtain sponge palladium.

[0037] Preferably, in step 21, a polydimethylaminoethyl methacrylate (PDM) hollow fiber internal pressure nanofiltration membrane is used for suction filtration to remove base metal cations in the palladium-containing solution.

[0038] Preferably, in step 22, the ratio of the mass of the acid solution to the mass of palladium in the palladium-containing solution is 1.5L:1kg.

[0039] Preferably, in step 22, the mass ratio of sodium chlorate to palladium in the palladium-containing solution is 0.7 kg:1 kg.

[0040] Preferably, in step 22, the ratio of the mass of ammonium chloride to the mass of palladium in the palladium-containing solution is 15kg:1kg.

[0041] Preferably, in step 23, the mass ratio of the ammonia solution to the palladium in the palladium-containing solution is 7-11 kg:1 kg.

[0042] Preferably, in step 23, the mass ratio of the ammonia solution to the palladium in the palladium-containing solution is 9kg:1kg.

[0043] One of the above technical solutions of the present invention has at least one of the following advantages or beneficial effects:

[0044] In the present invention, an air agitator is provided during the leaching process, and the air agitator introduces gas into the strong acid solution, thereby stirring the strong acid solution, promoting the dissolution of palladium on the alumina catalyst particles, and not destroying the alumina catalyst particles, so that the leaching rate of palladium is higher;

[0045] At the same time, during the leaching process, alumina catalyst particles are added to the hanging basket in multiple times. Each time alumina catalyst particles are added, the hanging basket is immersed in the container. Before the hanging basket is immersed, a portion of sodium chlorate solution needs to be added to the container to control the contact time between the alumina catalyst particles and the solution, reduce excessive reaction between the alumina catalyst particles and the solution, reduce the dissolution rate of the alumina catalyst particles, and facilitate the recycling of the alumina catalyst particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The present invention is further described below in conjunction with the accompanying drawings and embodiments;

[0047] Figure 1 is a flow chart of a first embodiment of the present invention;

[0048] Figure 2 is a front view of an air agitator according to a first embodiment of the present invention;

[0049] Figure 3 1 is a top view of an air agitator according to a first embodiment of the present invention. DETAILED DESCRIPTION

[0050] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions from beginning to end. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0051] The following disclosure provides many different embodiments or examples for implementing different solutions of the present invention.

[0052] Example 1

[0053] Reference Figures 1 to 3 As shown, a method for separating and purifying palladium from alumina catalyst particles comprises the following steps:

[0054] Weigh 150 g of alumina catalyst particles containing 2354 ppm palladium, and the palladium content is 0.3531 g;

[0055] Step 1: placing aluminum oxide catalyst particles in a strong acid solution containing an oxidant to leach palladium to obtain a palladium-containing solution; during the leaching process, an air agitator 1 is provided in the strong acid solution, and the air agitator 1 introduces gas into the strong acid solution to stir the strong acid solution, thereby promoting the dissolution of palladium on the aluminum oxide catalyst particles without destroying the aluminum oxide catalyst particles, and the palladium leaching rate is higher;

[0056] Specifically, the strong acid solution containing the oxidant includes pure water, a hydrochloric acid solution with a mass fraction of 35%, a hydrogen peroxide solution with a mass fraction of 50%, and a sodium chlorate solution with a solubility of 0.1 g / ml. 150 ml of pure water, 150 g of hydrochloric acid solution, and 2.5 g of hydrogen peroxide solution are placed in a container, the ratio of the volume of pure water to the total volume of the aluminum oxide catalyst particles is 3:1, the ratio of the mass of the hydrochloric acid solution to the total mass of the aluminum oxide catalyst particles is 1:1, and the ratio of the mass of the hydrogen peroxide solution to the total mass of the aluminum oxide catalyst particles is 1:60;

[0057] An air agitator 1 and an ultrasonic vibrating rod are provided in the container;

[0058] The alumina catalyst particles were divided into 6 portions;

[0059] Step 11: adding 1 g of sodium chlorate solution into the container; the solubility of the sodium chlorate solution is 0.1 g / ml, and the ratio of the mass of the sodium chlorate solution added each time to the mass of each portion of the alumina catalyst particles is 1:25;

[0060] Step 12: Add a portion of alumina catalyst particles, that is, 25g of alumina catalyst particles, into the hanging basket, immerse the hanging basket into the container, and take out the hanging basket after immersion for a predetermined time; the hanging basket is a titanium hanging basket, the diameter of the titanium hanging basket mesh is designed to be 0.6mm, and the particle size range of the alumina catalyst particles is 1mm to 2mm;

[0061] Step 13: Repeat steps 11 to 12 until all the alumina catalyst particles are added;

[0062] Step 14: immerse the hanging basket in the container, heat the solution in the container to 50°C to 60°C, and keep it warm for 2 hours; then heat the solution in the container to 85°C to 95°C, and keep it warm for 30 minutes; then cool the solution in the container to below 50°C, take out the hanging basket containing the alumina catalyst particles, rinse with pure water until the rinse liquid is colorless, combine the rinse liquid and the solution in the container to obtain a palladium-containing solution;

[0063] The net weight of the palladium-containing solution was 989.76 g. The palladium-containing solution was sent for inspection, and the palladium content was 0.3408 g. The alumina catalyst particles in the hanging basket were dried and weighed to 122.35 g. The calculated dissolution rate of palladium was 96.52%, and the dissolution rate of alumina catalyst particles was 18.43%.

[0064] Adding the alumina catalyst particles and the sodium chlorate solution in multiple times can control the contact time between the alumina catalyst particles and the solution, reduce excessive reaction between the alumina catalyst particles and the solution, reduce the dissolution rate of the alumina catalyst particles, and facilitate the recycling of the alumina catalyst particles; and, the sodium chlorate solution should be added before placing it in the hanging basket to allow the sodium chlorate solution to be diluted in the solution in the container first to avoid the situation where the sodium chlorate solubility is too high locally, which will cause excessive dissolution of the alumina catalyst particles.

[0065] Step 2: Extracting palladium from a palladium-containing solution.

[0066] The specific steps include:

[0067] Step 21: filtering out base metal cations in the palladium-containing solution to obtain a first filtrate; since the base metal cation impurities are removed, the palladium product obtained after subsequent purification has a relatively high purity;

[0068] The base metal cations in the palladium-containing solution can be removed by suction filtration using a poly(dimethylaminoethyl methacrylate) (PDM) hollow fiber internal pressure nanofiltration membrane;

[0069] Step 22: adding 0.53 ml of 35% hydrochloric acid solution, 0.24 g of sodium chlorate solid and 5.1 g of ammonium chloride solid to the first filtrate, wherein the ratio of the hydrochloric acid solution to the palladium in the palladium-containing solution is 1.5 L:1 kg, the ratio of the sodium chlorate to the palladium in the palladium-containing solution is 0.7 kg:1 kg, and the ratio of the ammonium chloride to the palladium in the palladium-containing solution is 15 kg:1 kg; filtering to obtain ammonium chloropalladate solid;

[0070] Step 23: dissolving the ammonium chloropalladate solid in an ammonia solution, filtering, and obtaining a second filtrate; the ammonia solution is 3.07 g, and the ratio of the ammonia solution to the palladium mass in the palladium-containing solution is 9 kg:1 kg;

[0071] Step 24: The pH value of the second filtrate is adjusted to 8-9 with aqueous ammonia solution, and then added dropwise to hydrazine hydrate for reduction to obtain a black precipitate of sponge palladium with a purity of 3N5 or above.

[0072] The sponge palladium was sent for testing and found to have a purity of 99.98%.

[0073] In this embodiment, the air agitator 1 includes a connecting pipe 11 and a coil 12. The connecting pipe 11 connects the coil 12 with an external air generator. The coil 12 is spiral-shaped and has a plurality of air outlets. The air outlets exhaust air at intervals of 5 seconds. The duration of each air outlet is 5 seconds. The gas flow rate during air outlet is 10 m / s. The interval air outlet can intermittently surge the solution to allow the solution to fully contact with the alumina catalyst particles.

[0074] Specifically, the air outlet includes a first air outlet 121 and a second air outlet 122. The air outlet direction of the first air outlet 121 is parallel to the axial direction of the coil 12, and the angle between the air outlet direction of the second air outlet 122 and the axis of the coil 12 is 45°. The first air outlet 121 and the second air outlet 122 both penetrate the coil 12 along their air outlet directions. Under this structure, the gas not only moves up and down, but also moves obliquely upward or obliquely upward, thereby disturbing the solution and allowing the solution to be fully stirred without destroying the alumina catalyst particles.

[0075] Generally speaking, on the coil 12, the first air outlet holes 121 and the second air outlet holes 122 are arranged alternately;

[0076] The gas outlet directions of two adjacent second gas outlet holes 122 are staggered, one second gas outlet hole 122 is inclined upward in a direction away from the axis of the coil 12, and the other second gas outlet hole 122 is inclined upward in a direction close to the axis of the coil 12. In this way, the gas outlet direction is changeable, and the solution flow direction is changeable, so that the solution is fully stirred.

[0077] In this embodiment, the frequency of the ultrasonic vibration rod is 65 Hz, and the ultrasonic length of the ultrasonic vibration rod is 10 mm.

[0078] Example 2

[0079] The embodiment is substantially the same as the first embodiment, except that: the air agitator 1 is only provided with the first air outlet 121 .

[0080] Example 3

[0081] The embodiment is substantially the same as the first embodiment, except that: the air agitator 1 is only provided with the second air outlet 122 .

[0082] Example 4

[0083] The method is substantially the same as Example 1, except that the alumina catalyst particles are divided into two equal parts.

[0084] Example 5

[0085] The method is substantially the same as Example 1, except that the alumina catalyst particles are divided into 9 equal parts.

[0086] Example 6

[0087] The method is substantially the same as Example 1, except that the ratio of the mass of the sodium chlorate solution added each time to the mass of each portion of the aluminum oxide catalyst particles is 1:15.

[0088] Example 7

[0089] The method is substantially the same as Example 1, except that the ratio of the mass of the sodium chlorate solution added each time to the mass of each portion of the aluminum oxide catalyst particles is 1:30.

[0090] Example 8

[0091] It is substantially the same as Example 1, except that the strong acid solution containing the oxidant is aqua regia liquid, and the ratio of the volume of the aqua regia liquid to the total volume of the alumina catalyst particles is 1:1.

[0092] Comparative Example 1

[0093] It is substantially the same as Example 1, except that no air agitator 1 is provided during the leaching process.

[0094] Comparative Example 2

[0095] It is substantially the same as Example 1, except that a stirring shaft is used to replace the air stirrer 1, and the stirring shaft rotates under the drive of a motor to stir the solution in the container.

[0096] Results Analysis

[0097] The dissolution rate of palladium, the dissolution rate of alumina catalyst particles, the weight of palladium products and the purity of palladium products of Examples 1-8 and Comparative Examples 1-2 were respectively detected. The palladium-containing solution was mixed and sampled, and the palladium content was detected by ICP-OES to calculate its leaching rate. The alumina catalyst particles were washed, dried and weighed to calculate their dissolution rate, and the purity of sponge palladium was detected by ICP-OES. The specific values ​​are shown in Table 1.

[0098] Table 1

[0099]

[0100] Compared with Examples 1 to 3, the air outlet holes on the air agitator have a greater influence on the dissolution rate of palladium. If there are only the first air outlet hole and the second air outlet hole on the air agitator, the dissolution rate of palladium will be lower.

[0101] Comparing Examples 1, 4 and 5, when the alumina catalyst particles were divided into only 2 portions for leaching, the dissolution rate of palladium was low, and when the alumina catalyst particles were divided into 9 portions for leaching, the dissolution rate of palladium was better, but the dissolution rate of the alumina catalyst particles also became higher, affecting the recycling of the alumina catalyst particles;

[0102] Comparing Examples 1, 6 and 7, when more sodium chlorate solution is added each time, the dissolution rate of palladium is better, but the dissolution rate of the alumina catalyst particles is also high; when less sodium chlorate solution is added each time, the dissolution rate of palladium is poor;

[0103] Comparing Examples 1 and 8, when aqua regia solution was used, the dissolution rate of palladium was very good, but the dissolution rate of the alumina catalyst particles was extremely high, and too few alumina catalyst particles could be recovered;

[0104] Comparing Example 1 with Comparative Example 1, when the air agitator is not used, the dissolution rate of palladium is extremely low, and too little sponge palladium can be obtained;

[0105] Comparing Example 1 with Comparative Example 2, when mechanical stirring is used, the dissolution rate of palladium is better, but mechanical stirring easily destroys the alumina catalyst particles, which increases the dissolution rate of the alumina catalyst particles and makes the alumina catalyst particles difficult to recycle.

[0106] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for separating and purifying palladium from alumina catalyst particles, characterized in that: The following steps are involved: Step 1: placing aluminum oxide catalyst particles in a strong acid solution containing an oxidant to leach palladium to obtain a palladium-containing solution; during the leaching process, an air agitator is provided in the strong acid solution to introduce gas into the strong acid solution to stir the strong acid solution; Step 2: Extracting palladium from a palladium-containing solution.

2. The method for separating and purifying palladium from alumina catalyst particles according to claim 1, characterized in that: The air agitator comprises a connecting pipe and a coil, wherein the connecting pipe connects the coil and an external air generator, the coil is spiral-shaped, and a plurality of air outlet holes are arranged on the coil.

3. The method for separating and purifying palladium from alumina catalyst particles according to claim 2, characterized in that: The air outlet holes include a first air outlet hole, and the air outlet direction of the first air outlet hole is parallel to the axial direction of the coil.

4. The method for separating and purifying palladium from alumina catalyst particles according to claim 2 or 3, characterized in that: The air outlet hole includes a second air outlet hole, and the angle between the air outlet direction of the second air outlet hole and the axis of the coil is 45°.

5. The method for separating and purifying palladium from alumina catalyst particles according to claim 2, characterized in that: The air agitator discharges air at intervals of 4 to 6 seconds, the discharge time is 4 to 6 seconds, and the gas flow rate during discharge is 9 to 11 m / s.

6. The method for separating and purifying palladium from alumina catalyst particles according to claim 1, characterized in that: In step 1, during the leaching process, an ultrasonic vibrating rod is placed in the strong acid solution.

7. The method for separating and purifying palladium from alumina catalyst particles according to claim 1, characterized in that: The oxidant is hydrogen peroxide or a mixture of hydrogen peroxide and sodium chlorate.

8. The method for separating and purifying palladium from alumina catalyst particles according to claim 7, characterized in that: Before performing step 1, pure water, hydrochloric acid solution and hydrogen peroxide solution are placed in a container, and the aluminum oxide catalyst particles are divided into multiple portions; step 1 comprises the following steps: Step 11: Add sodium chlorate solution into the container; Step 12: Add a portion of alumina catalyst particles into the hanging basket, immerse the hanging basket into the container, and take out the hanging basket after immersion for a predetermined time; Step 13: Repeat steps 11 to 12 until all the alumina catalyst particles are added; Step 14: Let the hanging basket be immersed in the container, heat the solution in the container to 50°C ~ 60°C, and keep it warm for 2 hours; then heat the solution in the container to 85°C ~ 95°C, and keep it warm for 30 minutes; then cool the solution in the container to below 50°C, take out the hanging basket containing alumina catalyst particles, rinse it with pure water, combine the rinse liquid and the solution in the container to obtain a palladium-containing solution.

9. The method for separating and purifying palladium from alumina catalyst particles according to claim 8, characterized in that: The mass fraction of hydrochloric acid solution is 35%, and the mass fraction of hydrogen peroxide solution is 50%; The ratio of the volume of pure water to the total volume of the alumina catalyst particles is 1 to 5:1, the ratio of the mass of the hydrochloric acid solution to the total mass of the alumina catalyst particles is 0.5 to 1.5:1, and the ratio of the mass of the hydrogen peroxide solution to the total mass of the alumina catalyst particles is 1:55 to 65; The solubility of the sodium chlorate solution is 0.1 g / ml, and the ratio of the mass of the sodium chlorate solution added each time to the mass of each portion of the aluminum oxide catalyst particles is 1:20-30.

10. The method for separating and purifying palladium from alumina catalyst particles according to claim 1, characterized in that: The step 2 comprises the following steps: Step 21: filtering out base metal cations in the palladium-containing solution to obtain a first filtrate; Step 22: adding a 35% by mass hydrochloric acid solution, sodium chlorate and ammonium chloride to the first filtrate, wherein the ratio of the hydrochloric acid solution to the palladium in the palladium-containing solution is 1-2L:1kg, the ratio of the sodium chlorate to the palladium in the palladium-containing solution is 0.4-1.2kg:1kg, and the ratio of the ammonium chloride to the palladium in the palladium-containing solution is 10-20kg:1kg; filtering to obtain ammonium chloropalladate solid; Step 23: dissolving the ammonium chloropalladate solid into an aqueous ammonia solution, and filtering to obtain a second filtrate; Step 24: The pH of the second filtrate is adjusted to 8-9 with aqueous ammonia solution, and then added dropwise to hydrazine hydrate for reduction to obtain sponge palladium.

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