Tekhnoatom JSC, Moscow, Russia:

A. A. Antonov, Senior Researcher, Candidate of Technical Sciences, mobile: +7-903-722-07-05

ReMetall AG, Drochov, Germany:
A. Titts, Chairman of the Board

National Research Nuclear University MEPhI, Moscow, Russia:

N. N. Samotaev, Associate Professor, Candidate of Technical Sciences

National Research Nuclear University MEPhI, Moscow, Russia¹ ; I. P. Bardin Science Institute for Ferrous Metallurgy, Moscow, Russia²:
A. S. Kirichenko, Engineer¹, Researcher²

This paper considers some advanced recycling techniques for spent auto catalysts, as well as the main drawbacks related to their utilization in industry. Electrochlorination is proposed as the basic recycling technique for secondary platinoids. 10 tons of spent catalysts were recycled as part of the tests. Research data on extraction of platinum, palladium and rhodium have been analyzed. The recovery figures reached for Pt, Pd and Rh were 97, 97 and 80%, correspondingly. The main drawbacks of the conventional electrochlorination process include a long process of platinoid electrodeposition (up to 50 hours), the need for thermal pre-activation of platinoids, a technical difficulty related to electrolyte circulation when the material is finely dispersed, a low recovery of rhodium (80%), and disposal of waste electrolyte. The conventional electrochlorination process has been optimized, and thus a new highly efficient and environmentally friendly process has been developed enabling a high recovery of platinoids with no need for thermal pre-activation. The originality of the proposed process is that two independent electrodeposition processes (involving direct and alternating current with variable frequency) overlap amid forced, continuous and complete overcondensation of electrolyte resulting in a superadditive effect. The use of direct and alternating current from different sources helped achieve a higher recovery of platinoids (Pt, Pd and Rh — 98, 98 and 90%, respectively) by loosening their passive forms with atomic chlorine and thus skipping the thermal pre-activation stage. Through forced evaporation and overcondensation of electrolyte in a separate container, the authors were able to increase the rate of platinoid electrodeposition and obtain treated solutions which could be re-used saving the need for electrolyte circulation. The full treatment cycle took 6-8 hours. The authors elaborate on the prospective development of the new process, which will create a breakthrough in spent catalyst recycling.
This research was funded by the Ministry of Higher Education and Science of the Russian Federation (Grant Agreement No. 14.575.21.0153 dated 26/09/2017; ID: RFMEFI57517X0153).

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