Method for the recovery of precious metal

Abstract

The invention relates to a method for the recovery of precious metal from materials containing precious metal, said method comprises the following steps of: A) bringing the materials containing the precious metal into contact with an oxidizing agent, B) bringing the material containing the precious metal into contact with a reducing agent. Said method offers the possibility of recovering precious metal in a simple manner and in high purity from secondary materials.

Claims

1. A process for isolating noble metal from noble metal-containing materials, the process comprising the steps A) contacting of the noble metal-containing materials with an oxidizing agent and subsequently flushing with an inert gas to remove the oxidizing agent, B) contacting of the noble metal-containing material with a reducing agent and subsequently flushing with an inert gas to remove the reducing agent, wherein the steps A) and B) represent a reaction cycle which is carried out in aqueous solution; C) repeating the reaction cycle until a content of noble metal in the aqueous solution no longer increases.

2. The process as claimed in claim 1, characterized in that the noble metal is selected from the group consisting of Pt, Pd, Rh, Au, Ru, Ir, Os and Ag.

3. The process as claimed in claim 1, characterized in that the reaction cycle is carried out at a pH of 3 or 10.

4. The process as claimed in claim 3, characterized in that the pH is set by an acid selected from among HCl, HClO.sub.4, H.sub.2SO.sub.4, HNO.sub.3, aqua regia and any mixtures of the above, or an alkali metal hydroxide.

5. The process as claimed in claim 1, characterized in that at least one of the steps A) and B) is carried out in the presence of a complexing agent.

6. The process as claimed in claim 5, characterized in that the complexing agent is selected from among NaCl, KCl, NaBr, KBr, Nal, Kl, NaCN, NaOCN, NaSCN, KCN, KOCN and/or KSCN.

7. The process as claimed in claim 1, characterized in that the oxidizing agent is selected from among O.sub.2, O.sub.3 (ozone), H.sub.2O.sub.2, HClO.sub.4 or salts thereof, HClO.sub.3 or salts thereof, alkali metal permanganate, alkali metal percarbonates, alkali metal persulfates and any mixtures of the above.

8. The process as claimed in claim 1, characterized in that the reducing agent is selected from among H.sub.2S, SO.sub.2, SO.sub.3, CO, H.sub.2, methanol, ethanol and any mixtures thereof.

9. The process as claimed in claim 1, characterized in that the noble metal is isolated from the reaction solution by mechanical or electrochemical methods.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 shows the results of the experiments (i) to (iv) of Example 1 in graph form.

(2) FIG. 2 shows the results of Example 2 as a graph.

(3) FIG. 3 shows the results of Example 3 as a graph.

DESCRIPTION OF PREFERRED EMBODIMENTS

EXAMPLES

Example 1

(4) In a glass beaker provided with a magnetic stirrer bar, a solution was produced from 100 ml of 0.1 M HClO.sub.4 and 10 l of 1 M NaCl so as to give a solution having a chloride ion concentration of 0.1 M. 17.0128 g Pt particles having a particle size of 3 nm on activated carbon having a large surface area (loading with metal 46%) were deposited on a smooth carbon surface. The carbon support was dipped into the solution and rotated at 400 rpm. The glass beaker had two inlets for gases.

(5) Four different experiments were carried out in order to examine the influence of (i) reaction solution, (ii) ozone, (iii) exchange between ozone and hydrogen, (iv) exchange between ozone and CO and (v) exchange between ozone and CO in 0.1 M HCl as reaction solution. (i) stirring of the suspension in the presence of air for a period of 35 minutes (ii) stirring of the suspension in the presence of O.sub.3 for a period of 35 minutes (iii) stirring of the suspension for five minutes in each of O.sub.3, Ar, O.sub.2, Ar, O.sub.3, Ar, H.sub.2, Ar (iv) stirring of the suspension for five minutes in each of O.sub.3, Ar, Co, Ar, O.sub.3, Ar, CO and Ar.

(6) The results are shown in the following table.

(7) TABLE-US-00001 Reaction with % of Pt 1 0.51 2 O.sub.3 1.15 3 O.sub.3/H.sub.2 6.26 4 O.sub.3/CO 49.83

(8) The results of the experiments (i) to (iv) are shown in graph form in FIG. 1.

Example 2

(9) Pt particles having a particle size of 3 nm on activated carbon having a large surface area (loading with metal 46%) (obtainable from Tanaka Kikinzoku Intern, Japan) were suspended in a concentration of 0.1 mg/ml in 200 ml of 0.1 M HClO.sub.4 and 10 l of 1 M NaCl as per example 1 in a glass beaker containing a magnetic stirrer bar. The solution was stirred using a magnetic stirrer during the process. The glass beaker had two inlets for gases.

(10) Procedure:

(11) 20 min O3, 10 min Ar, 10 min CO, 10 min Ar, 10 min O3, 5 min Ar, 10 min CO, 10 min Ar, 10 min O3, 5 min Ar . . . .

(12) The results are shown in FIG. 2.

Example 3

(13) In a glass breaker containing 200 ml of 0.1 M HCl, nanoparticles comprising Pt and Pd which were embedded in the washcoat on SiAl-based honeycomb ceramic were suspended and filtered through a 200 nm filter. The glass beaker had two inlets for gases. The process was carried out with stirring.

(14) Procedure:

(15) CO 20 min+Ar 5 min+O.sub.3 20 min+Ar 5 min+CO 20 min+Ar 5 min+O.sub.3 20 min+5 min Ar . . . .

(16) The results are shown in the following table.

(17) TABLE-US-00002 Reaction with % of Pt (dissolved) 1 0.001 2 Sample 0.004 3 1 cycle 3.113 5 6 cycles 6.980 6 12 cycles 24.211 7 19 cycles 42.594

(18) The results are shown in graph form in FIG. 3.

(19) As the experimental results show, the Pt concentration increases linearly with the number of cycles (in each case reaction with ozone and CO). This means that a recovery of the noble metal of almost up to 100% is ultimately possible.