JPS61110731A - Method for collecting platinum and palladium from platinum catalyst - Google Patents

Abstract

PURPOSE:To collect a platinum metal with a high yield by dissolving and extracting a waste catalyst using the platinum metal, by a strong acid, adding an excessive iron powder to said catalyst, executing simultaneously hydrogen reduction and cementation, precipitating the platinum metal, and thereafter, adsorbing and removing the excessive iron powder by a magnetic separating machine. CONSTITUTION:A used waste catalyst of a Pt precious metal catalyst of Pt, Pd, etc. carried by a carrier of alumina, silica, etc. is treated by a strong acid water solution of >=60 deg.C of HCl=1.0N, HNO3>0.2N, in a state that it remains uncrashed, and Pt, Pd, etc. are dissolved and extracted. An excessive iron powder is added to an extracted liquid separated from the carrier, a reducing reaction of an H2 gas and a cementation are executed simultaneously within a range of -50mV-250mV of the reducing potential, and Pt and Pd dissolved in the acid liquid are precipitated with a yield of >=95% in a short time. The excessive iron powder mixed to Pt and Pd precipitated in the end is adsorbed and separated by a magnetic separating machine, and Pt and Pd are collected with a high yield.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for simultaneously recovering platinum and palladium from spent platinum catalysts used for automobile exhaust gas purification at low cost and with a high yield of 95% or more.

In general, catalyst carriers are often made of acid-insoluble materials such as alumina, silica, and carbon, and these carriers are coated with platinum metal elements that maintain strong catalytic reactions. However, although such elements are scarcely available as domestic resources, their demand is only increasing with the development of the automobile industry. On the other hand, the technical aspect of collection is still not sufficient.

Automotive catalysts are broadly divided into pellet-shaped and honeycomb-shaped catalysts, but both shapes can be extracted in an unpulverized state.

Therefore, the present invention consists of a combination of the following three steps.

First step: The used catalyst has a solid-liquid ratio of 173 () 1.0)
Add HCl 18 or more (preferably 1.5 to 2.0N) and HHO30,
2N or more (0.4N is preferable) and 60'C or more (
The reaction extraction is carried out for 2 hours at a temperature of 75-80°C (most preferably 75-80°C).

After the reaction, the mixture is diluted approximately twice with water and subjected to solid-liquid separation using a sedimentation method.

Second step: Precipitation from the extract is carried out at room temperature, and generally cementation involves the addition of alkali to achieve a predetermined pH.
A known method is to then perform cementation with iron or zinc, but the present invention provides a method that does not use any neutralizing agent. Accordingly, in the present invention, iron powder is added to a strongly acidic extract (pH below), and the reduction reaction of H1 gas and cementation are simultaneously carried out, and platinum and palladium are precipitated in a short time due to a synergistic effect. It is something that can be done. Furthermore, this precipitation reaction has a reduction potential of −50
It is characterized in that it is carried out within the range of -25On+V.

This makes it possible to maintain a relatively high yield of 98% or more of the platinum metal element from the solution.

Third Step If the reduction potential is less than 150 mV, there is a risk that the precipitated platinum and palladium will be redissolved, so a high yield can generally be maintained by adding iron powder in a slightly excessive amount.

Therefore, excess iron powder causes a decrease in the quality of precipitated platinum and palladium, so it is separated and recovered by magnetic separation and returned to the second step for reuse.

Next, the present invention will be explained in detail with reference to examples. The composition of the catalyst used in this example is shown in Table 1, and the results of this process according to the process flow shown in FIG. 1 are shown in Tables 2 to 4.

Table 1: Composition of catalyst (weight%) Table 2 Conditions and results of the first step Table 4 Results of the third step The use of strong oxidizing agents is not preferred in the first elution step.

This is because a large amount of iron powder is required in the second step. Furthermore, although many types of reducing agents can be used in the precipitation reaction in the second step, all of them are expensive, and no technology has been established to recover the amount added in excess. The present invention uses recoverable iron powder and significantly reduces production costs.

Further, in the reduction reaction, if the reduction potential is -50 mV or less, the precipitation is incomplete, and the precipitated platinum metal element is redissolved, resulting in a significant decrease in yield.

As a result of applying the present invention to three types of catalysts, all catalysts could be recovered with a high yield of 95% or more. Therefore, the present invention is a technology for recovering even higher yields quickly at low cost. has been established and will greatly contribute to resource development.

[Brief explanation of the drawing]

FIG. 1 shows a processing flow of an embodiment of the present invention. Patent applicant: Japan Magnetic Separation Co., Ltd. Figure 1

Claims (1)

[Claims] 1. Platinum on alumina, silica, and carbon carriers,
Platinum-based catalysts containing palladium etc. are treated with HCl in an unpulverized state.
1.0N and HHO_30.2N or more, the first step is extraction at 60°C or higher, and the solid-liquid separation of the extract is performed, and iron powder is added to the strongly acidic liquid (pH 1.0 or less) to reduce the reduction potential to -5.
A second step in which hydrogen reduction and cementation are simultaneously reacted within the range of 0 mV to -250 mV, and a third step in which excess iron powder added in the second step is recovered by magnetic beneficiation and returned to the second step. A method for recovering platinum and palladium from a platinum-based catalyst, the method comprising recovering platinum and palladium from a platinum-based catalyst.