The use of a rotating cylinder electrode to selective recover palladium from acid solutions used to manufacture automotive catalytic converters

• Published in: Journal of applied electrochemistry Vol. 41; no. 1; pp. 89 - 97
• Main Authors: Terrazas-Rodríguez, J. E., Gutiérrez-Granados, S., Alatorre-Ordaz, M. A., Ponce de León, C., Walsh, F. C.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 2011
• Subjects: Automotive components; Carbon; Chemistry; Chemistry and Materials Science; Electrochemistry; Electrodes; Exhaust systems; Industrial Chemistry/Chemical Engineering; Neodymium; Original Paper; Palladium; Physical Chemistry; Rhodium; Stainless steels; Neodymium; Rhodium; Rotating cylinder electrode; Palladium; Metal recovery; Platinum group metals; Catalytic converters
• ISSN: 0021-891X; 1572-8838
• DOI: 10.1007/s10800-010-0212-9

The reduction of palladium, rhodium and neodymium ions at concentrations of 0.94, 0.97 and 0.69 mol dm
−3
, respectively was studied in 1 mol dm
−3
HNO
3
or 1 mol dm
−3
HCl, at a stainless steel and a vitreous carbon electrode, at 25 °C. At a vitreous carbon electrode in a solution containing rhodium and palladium ions in 1 mol dm
−3
HCl electrolyte, the reduction of metal ions occurred at a similar potential to the formation of hydrogen gas, which impeded the selective separation of the two metals. At a stainless steel cathode in 1 mol dm
−3
HNO
3
, palladium deposition occurred at a potential ≈0.35 V less negative than that of rhodium allowing the selective recovery of palladium. Neodymium ions were not electroactive in acidic chloride or nitrate media at pH 0. Using a solution obtained from a catalytic converter manufacturer containing palladium, rhodium and neodymium ions in 1 mol dm
−3
HNO
3
, palladium ions were preferentially removed at 0.15 V versus SHE at an average cumulative current efficiency of 57%.