RU194300U1 - VOLUME AC ELECTRODE FOR EXTRACTION OF NOBLE METALS - Google Patents

Abstract

The utility model relates to the electrochemistry of noble metals, in particular electrochlorination, and can be used in the processing of secondary metals of the platinum group, including catalysts, as well as their concentrates and refined metals. A volumetric alternating current electrode for extracting precious metals from porous ceramic catalysts includes a ceramic porous catalyst base particle with noble metals located in its pores. Moreover, in the pores, it additionally contains non-consumable particles with electronic conductivity in the form of dispersed particles of nanographite. The technical result is an increase in the percentage of extraction of precious metals at the cathode due to the complete electrochlorination of the entire volume of processed raw materials. 1 ill., 2 ave.

Description

The utility model relates to the electrochemistry of noble metals, in particular electrochlorination, and can be used in the processing of secondary metals of the platinum group (PGM), including catalysts, as well as their concentrates and refined metals. These methods are based on the processes of extracting PGMs from raw materials and isolating them at the cathode (Monograph: VI Maksimov “Electrochlorination as a method of complex metal extraction”, Moscow, Metallurgy. 1955).

It is known to use a suspension (acid and nanomaterial dispersed in it) as an electrolyte in galvanic methods for producing electrochemical oxide coatings modified with nanomaterial. In these methods, the electrolyte - suspension is used to increase the wear resistance and microhardness of the coatings.

It is known (RF patent No. 2607075) the use of a suspension of sulfuric acid and carbon nanomaterial powder as an electrolyte in direct current electroplating to increase the microhardness of the obtained anode coatings. As an anode, an aluminum part is used. Fullerene-like carbon nanotubes are used as the nanodispersed material. The use of this suspension as a volume electrode is not applicable for the extraction of secondary noble metals, where the deposition of metals occurs at the cathode, and their leaching from raw materials due to the formation of a chlorine ion.

It is known to use a suspension - solution (g / l) - K2CO3 / 20-35; KCNS / 150-200, containing Ag / 20-36 ions and modified with 5-30% nitric acid, nanocarbon-diamond material 0.2-2.0 as an electrolyte to obtain an electrochemical silver-nanocarbon-diamond cathode coating (RF patent No. RU 2599473) with increased wear resistance due to the introduction of a modified nanocarbon-diamond material into the silver coating. The sacrificial anode is a silver plate.

This suspension is not applicable as a volume electrode for scrap processing with a noble metal content of 0.05-0.5% and a non-conductive base (catalysts, electronics boards, etc.), because leaching of precious metals requires their anodic polarization. In addition, this electrolyte does not contain chlorine ion for the leaching of PGMs and their electrodeposition.

Known volume-porous electrode (anode or cathode) for a flow electrolyzer (RF patent No. 2178017), consisting of non-woven fibers metallized syntepon with a highly developed specific surface as a base, having electronic conductivity, and is also equipped with one or more layers of non-metallized syntepon having horizontal seals. This electrode has a current lead to a metallized matrix. The presented electrode is intended for a more complete deposition of metals from a solution already containing noble metals. However, it is useless for the initial extraction (leaching) from scrap of a noble metal into a solution for the purpose of its subsequent electrodeposition. Thus, its useful properties are realized only in the second stage during electrodeposition.

Closest to the proposed electrode design (prototype) is a volumetric AC electrode described in (RF patent No. 2198947). The presence of even a small amount of the metal phase (up to 0.2 wt%) in the ceramic raw material (catalyst) located in the interelectrode space under external alternating current leads to alternating polarization of the active metal centers, turning them into a dipole. In this case, the entire bulk of the bulk material begins to be a volumetric multipolar electrode, providing anodic dissolution of the metal in the entire volume of the raw material and subsequent separation on the cathode when applying direct current. Moreover, at a low frequency of the current, the polarity of the dipole changes alternately in time. During the existence of a particle as an anode, electrolyte decomposition occurs on it and active chlorine ion is released. Active chlorine reveals the passive form of PGM and its dissolution occurs, however, the efficiency of this electrode rapidly decreases under conditions of constant dissolution of active metal centers (initial PGMs), which leads to a decrease in the rate of dissolution of residual PGMs and an increase in the time of the whole process.

The objective of the present invention is to increase the efficiency of the process of extraction of precious metals, in particular PGM, with obtaining a technical result, which consists in increasing the productivity of the process and a high percentage of recovery of precious metals.

The technical result is achieved by the fact that a suspension based on a solution of hydrochloric acid is used as a volume electrode, and nanographite particles with electronic conductivity are used.

The proposed suspension penetrates into the pores of the ceramic carrier, and is also located in the channels and voids directly in the volume of the backfill. When an alternating current is applied, graphite particles at anodic polarization generate active chlorine in the immediate vicinity of the PGM in the entire volume and pores. Moreover, carbon particles are not consumed in the process and effectively act throughout the entire process, depassivating and chlorinating residual noble metals.

A proposed utility model is illustrated in FIG. one.

In FIG. 1 shows a volumetric AC electrode for the extraction of precious metals.

In FIG. 1, the following notation is used. 1 - graphite electrodes of alternating current. 2 - porous catalyst particle with PGM. 3 - decomposition of HCl on a graphite particle with the formation of Cl and N.

Example 1

Spent automotive catalyst with a platinum content of 0.1%, palladium 0.1%, rhodium 0.035% by weight after grinding was loaded into the interelectrode space of the electrolyzer in an amount of 0.5 kg. Next, a suspension was prepared on the basis of an aqueous solution of hydrochloric acid and nanographite. Mixing of the suspension was carried out by an ultrasonic generator. The prepared suspension was poured into the electrolyzer with a catalyst in a solid / liquid volume ratio of 1 / 1.5. Then, alternating current was switched on (I = 25 A, U = 12 V) and with the help of it the system was heated to 95-100 ° С. The AC electrodes were made of graphite. At the same time, direct current (I = 20 A, U = 1.7 V) was supplied to the electrolyzer from an independent source to direct current electrodes (titanium cathode, graphite anode). Electrochlorination with alternating current and simultaneous electrodeposition of PGMs on the cathode in direct current were carried out for 5 hours. At the end of the electrodeposition process by X-ray photoelectron spectroscopy, the residual content of PGMs on the support was analyzed. The result was the following concentrations of Pt = 70ppm, Pd = 50ppm and Rh = 40ppm. After washing the treated tail of the catalyst, the residual content was Pt = 12 ppm, Pd = 8 ppm and Rh = 20 ppm.

Example 2

The same catalyst with the same parameters was treated in a hydrochloric acid electrolyte of the same concentration without the addition of nanographite. Almost the same residual PGM content was obtained after 11 hours of treatment.

Thus, comparison of experimental results indicates a more efficient chlorination and leaching of PGMs due to the addition of nanographite to the electrolyte, which in this case works as a volume electrode.

Claims (1)

A volumetric AC electrode for extracting precious metals from porous ceramic-based catalysts containing a ceramic porous catalyst base particle with noble metals located in its pores, characterized in that it additionally contains non-consumable particles with electronic conductivity in the form of dispersed particles of nanographite.

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