JPH0853720A - Dissolving method of platinum group metal in collector metal - Google Patents

Abstract

PURPOSE:To efficiently dissolve a platinum group metal in a collector metal by firing the collector metal and heating and dissolving it in hydrochloric acid while adding an oxidizing agent. CONSTITUTION:A hardly soluble waste catalyst powder (collector metal) containing platinum group metal with various impurities is fired at 700-100 deg.C for 2-12hr in closed state. The collector metal is heated and dissolved in the hydrochloric acid by stirring and keeping at 60-100 deg.C for 2-10hr while adding the oxidizing agent (H2O2). In this case, 700-1200ml hydrochloric acid of 35% concn. and 400-700ml H2O2 of 35% concn. per 100g collector metal are used. As a result, the platinum group metal is dissolved at about 87.5% dissolution rate without using a special reagent and repeating complicated processes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently dissolving a platinum group metal from a sparingly soluble waste catalyst powder (hereinafter referred to as a collector metal) containing a platinum group metal together with various impurities.

[0002]

2. Description of the Prior Art Used automobile catalysts are dissolved together with the muffler, and in the case of a ceramic honeycomb, Si is used.
Fe as a catalyst substance (Pt, Pd, Rh) supported on the layer
The layer is phased and atomized into powder, and in the case of a stainless honeycomb, it is simply melted and atomized. In this case as well, since Fe collects the platinum group metal, it is commonly called a collector metal, but it is expected that the Si quality will increase if the ratio of the ceramic honeycomb is large. Although this powder contains a trace amount of platinum group metals (Pt, Pd, Rh), it is based on Fe and other various metals (Cu, Ni, Cr, etc.) and nonmetals (Si, P, S).
Etc.), it is very difficult to process. Table 1 shows an example of the quality.

[0003]

[Table 1]

Conventionally, in order to dissolve the platinum group metal in the collector metal as described above, no pretreatment was carried out, and aqua regia or hydrochloric acid alone was dissolved.

However, among the conventional methods, the method of dissolving with hydrochloric acid alone has a low elution rate of 30 to 80%, and the elution rate varies considerably.
The variation is due to the Si grade in the raw material, and generally S
When the i grade was high, the elution rate was low. The uneluted content remained in the residue and was repeated in the process, so the recovery rate of the platinum group metal in one pass was low.

Also, in the case of dissolution with aqua regia, the material of the container for dissolution is limited, so considering the actual operation, there is a risk that the equipment will be expensive when the scale is increased. Further, aqua regia with a hydrochloric acid to nitric acid ratio of 3: 1 interfered with the subsequent steps and required denitrification treatment.

The object of the present invention is to use no special reagents,
Another object of the present invention is to provide a method for efficiently dissolving the platinum group metal in the collector metal in one pass without depending on a complicated method or repetition, and an object of the invention is to dissolve the platinum group metal in a hydrochloric acid system for the convenience of the treatment in the subsequent step.

[0008]

The present invention is characterized in that after the collector metal is fired, it is heated and dissolved while adding an oxidizing agent to hydrochloric acid. Hereinafter, the present invention will be described by dividing it into a pre-stage firing step and a post-stage melting step.

Firing step The collector metal is a complex oxide based on Fe,
According to the differential thermal analysis, it is a mixed powder of chloride, sulfide, etc.
There was a point around 850 to 870 ° C where the morphology seemed to have changed. Therefore, the present inventors considered that it is possible to change the collector metal into a form in which it is easily melted by firing at around this temperature. By actually firing, the elution rate is remarkably improved to 87.5% as will be apparent from the examples described later.

The firing temperature is 700 to 1000 ° C.,
More preferably, the temperature is set to 850 to 900 ° C., and the firing time is set to 2 hours to 12 hours, preferably 5 hours to 7 hours. The firing is preferably held in a firing furnace in a sealed state.

Dissolution step The concentration of hydrochloric acid used is 700 to 1200 ml of hydrochloric acid having a concentration of 35% with respect to 100 g of collector metal, more preferably 1000 ml, and 35% H ₂ O ₂ and 400 as oxidizers.
~ 700 ml, more preferably 600 ml is added and dissolved. The amount of hydrochloric acid and H ₂ O ₂ is 100 g / mol of collector metal with respect to the amount of collector metal.
l is optimal. I want to dissolve as much collector metal as possible against the amount of hydrochloric acid, but if it exceeds 100 g / l,
Filtration after dissolution is deteriorated, and at 150 g / l, it is extremely deteriorated. The addition ratio of the oxidizing agent to 5 of concentrated hydrochloric acid is 1 to 4, preferably 3. The amount of H ₂ O ₂ added is 5% concentrated hydrochloric acid as described above.
On the other hand, 3 is the optimum condition, but if it is added more than that, the elution rate is not improved, and if it is added too much, the acid concentration after dissolution becomes low, which is not preferable. Even if the amount of H ₂ O ₂ added is about 1 with respect to hydrochloric acid 5, the effect of improving the elution rate is high, but if not used at all, the elution rate becomes extremely poor. Practically, the ratio of addition of hydrochloric acid should be at least 5: 1.

A good filtration rate can be obtained by maintaining the temperature at the time of dissolution at 60 to 100 ° C., more preferably at 80 ° C., and stirring for 2 to 10 hours, more preferably 6 hours. .

The melting process in the present invention is as follows. That is, H ₂ O ₂ has a strong oxidizing power,
When added to Cl, it foams and decomposes.

(Equation 1) Also, by acting on hydrochloric acid,

(Equation 2) At this time, it assists the elution of Pt, Pd, and Rh in the collector metal. Since H ₂ O generated at the same time lowers the acid concentration after dissolution, it is important to add the necessary minimum amount.

[0014]

Example 1 600 g of collector metal was placed in a graphite crucible, and the one sealed with a lid was baked at 870 ° C. for 6 hours in an electric furnace. After that, load into a beaker and add 6 liters of 35% hydrochloric acid (concentration of collector metal to 100 g / l).
Was added and kept at a temperature of 80 ° C., and 35% H ₂ O ₂ was added while changing the amount so that the addition ratio to hydrochloric acid was 5: 3 and 5: 1, while the addition ratio of H ₂ O ₂ was 5%. : 3 hours for 6 hours, H ₂ O ₂
The addition ratio of 5: 1 was dissolved with stirring for 4 hours. After dissolution, it was cooled, filtered and analyzed. When the average dissolution rate of Pt, Pd, and Rh was obtained by treating 5 batches under the same conditions, the results shown in Table 2 were obtained.

[0015]

Example 2 A test was conducted under the same conditions as in Example 1, except that the firing temperature and firing time were changed. That is, the firing conditions are 800 ° C. and 6
Baking for 1 hour at 870 ° C. and 6 hours at 500 ° C. Thereafter, the hydrochloric acid concentration and the H ₂ O ₂ addition ratio were set to 5: 3, and Pt, Pd, and Rh were added in the same manner as in Example 1.
The average dissolution rate of The results are also shown in Table 2.

[0016]

[Comparative Examples 1 to 3] As comparative examples, the same as Example 1 except that each was tested without firing (Comparative Example 1), hydrochloric acid was added, but H ₂ O ₂ was not added. For each example (Comparative Example 2), Pt, P
When the average dissolution rates of d and Rh were determined, the results shown in Table 2 were obtained.

[0017]

PRIOR ART As a conventional example, tests were carried out with and without calcination when dissolved in aqua regia. In addition, the test was performed using concentrated hydrochloric acid alone. Table 2 shows the results.

[0018]

[Table 2]

[0019]

As described above, according to the present invention, the platinum group metal in the collector metal can be removed in one pass without using a special reagent such as conventional aqua regia and without using a complicated method or repetition. It can be dissolved efficiently.

Claims (1)

[Claims] 1. A method for dissolving a platinum group metal in a collector metal, which comprises heating a hardly soluble waste catalyst powder (collector metal) and then heating and dissolving it while adding an oxidizing agent to hydrochloric acid.