Recovery and Then Individual Separation of Platinum, Palladium, and Rhodium from Spent Car Catalytic Converters Using Hydrometallurgical Technique followed by Successive Precipitation Methods

Abstract

Recovery of PGMs (especially rhodium, platinum, and palladium) from different spent manufactured products (like catalytic converters) is considered as an important task as they are rarely found in nature, and they possess high economic value. In this work, the honeycomb of a car catalytic converter was primarily processed by crushing, grinding, and then treating in a hydrogen atmosphere. In order to establish an economic and ecofriendly method for the recovery of studied PGMs, different experimental conditions of changing HCl/H2O2 (as a leaching solution) ratio, temperature, and contact time were studied through batch experiments to obtain the optimum leaching conditions. The use of 0.8 vol% H2O2 and 9.0 M HCl mixture at 60°C for a contact time of 2.5 hours during the leaching process may be considered as the best conditions to be followed to save chemicals, energy, and time (about 86%, 96%, and 98% of Rh, Pt, and Pd were recovered, respectively). Individual separation of PGM ions from each other using precipitation technique from their leaching liquor was performed where % purity values of 99.5, 99.3, and 95.5 were obtained for Pt, Pd, and Rh, respectively.

Status of Recovery of Strategic Metals from Spent Secondary Products

“…Another study reported spent automotive catalysts that were heated under a hydrogen atmosphere at 250 • C, which improved metal recovery during leaching due to the elimination of the hydrocarbons and charcoal present on the catalyst surface and the reduction of oxidized PGMs [38]. Pretreatment of the catalytic powder also assists in stabilizing the PGMs in their metallic form, making them easy to dissolve with leaching solutions [45].…”

Selective precipitation of ammonium hexachloropalladate from leaching solutions of cemented palladium with zinc

“…Some conditions have been reported to precipitate Pd ions from several kinds of aqueous solutions containing other ions. It has been found that addition of NaClO3 to the acidic solution in the absence of platinum ion could oxidize Pd(II) to Pd(IV) and slowly precipitate Pd(IV) as (NH4)2PdCl6 at high temperature (90°C) [9,10]. Besides, (NH4)2PdCl6 can be precipitated from the aqua regia solution containing Zn, Ni, Ag, Au by adding NH4Cl but the purity of the precipitates has not been reported [11].…”

Application of Ion Exchange for Recovery of Noble Metals

“…Noble metals, such as platinum, palladium, rhodium, and gold, are some of the most valuable elements due to their exceptional properties, such as high chemical and thermal resistance, which directly leads to their wide applicability in the electrical, jewelry, and automotive industries [1][2][3][4]. Due to their scarcity in the deposits naturally occurring in the Earth s crust, the current manufacturing tendency is slowly shifting to obtaining them from secondary raw materials, e.g., automotive catalysts, computer parts, and other electronic equipment [5][6][7]. Recovering noble metals from such sources is not an easy task, due to the similarity of their properties and the presence of other metals such as copper, iron, and zinc, which often hinder the recovery process [8,9].…”