New Mechanism for Depositing Platinum, Palladium, and Rhodium on Iron Metal Collector
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NEW MECHANISM FOR DEPOSITING PLATINUM, PALLADIUM, AND RHODIUM ON IRON METAL COLLECTOR A. S. Kirichenko,1 S. M. Nekhamin,2 N. N. Samotaev,3 and A. A. Antonov4
UDC 669.4:669.046.5:669.046.582.5: 669.054.8
The effect of using an iron metal collector (MC) instead of copper on the degree of extraction of platinum, palladium, and rhodium is investigated in processing ceramic-based automotive catalysts in an electric arc furnace. The dependence of the effect of melt holding time on platinum group metal (PGM) deposition rate on a furnace hearth is analyzed. It is determined that during creation of a homogeneous mixture and introducing a metal collector (MС) into the catalyst composition effective Pt, Pd, Rh extraction occurs in the first 20 minutes of melt exposure. In spite of the twice as high density of platinum, the degree of its extraction is at the level for Pd and Rh, which points to the possibility of depositing platinum group metals (PGM) on the furnace hearth using the surface of coarser added MС powder. Testing of various methods for adding MС demonstrate the effectiveness of introduction to the melt surface. When a melt is heated above the melting temperature of platinum and palladium, the maximum degree of extraction is reached in 6 min. This shows that solid rhodium may passivate the surface of added MС. In order to create conditions when there is always an MС free surface to which solid rhodium may adhere, the rate coefficient is determined for effective dissolution of Rh in iron MС. Determination of this coefficient makes it possible to scale up results of laboratory studies and to predict the minimum time required for melting MС on the furnace hearth without loss of valuable component. Keywords: spent automotive catalysts, surface passivation, rhodium extraction, platinum group metal extraction, metal-collector, introduction method, dissolution rate.
Currently spent automobile catalyzers based on ceramic are treated in electric furnaces, melting the acidresistant ceramic part with its conversion into slag and depositing heavy metals of the platinum group (MPG) on a furnace hearth [1–6]. In order to separate metals from slag a copper metal collector (MC) is placed on the hearth. In the next treatment stage the copper base is dissolved, and the residue obtained is fed for refining. Due to the high impact strength of copper it submits badly to crushing, as a result of which it is necessary to dissolve large pieces from which it is not possible to extract the MC copper base. Loss of expensive copper base with the residue has an unfavorable effect on treatment costs. In view of this it was decided to check the effect of a cheaper form of MC based on iron on extraction. In the scientific studies performed melt was held in a Tamman laboratory furnace charged with a homogenizing mixture consisting of, g: 200 catalyst, 70 lime, and 10 iron powder. The melt holding temperature was 1650 ºC that is connected with a requirement for melting the iron metal collector in order to deposit solid valuable components upon it.
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