Patent DE-102006056017-A1 (DE)
Title: Recovering of ruthenium, rhodium, palladium, osmium, iridium and platinum from precious metal containing solution by cathodic separation, comprises supplying the solution to cathode chamber and then separating or detaching the metal
Inventor: FRIEDRICH HANS-JUERGEN
IPC: C25C1/20
Filed: 2006-11-23
Abstract: The procedure for recovering of ruthenium, rhodium, palladium, osmium, iridium and platinum from a precious metal containing solution by cathodic separation with the help of a electrolysis cell separated by a cation exchanger membrane, comprises supplying the solution to a cathode chamber, and then mechanically separating or electro-chemically detaching the precious metal. The separation is carried out with a current density of 10-50 mA/cm2> at a cathode potential of -240 to -280 mV related to the potential of a saturated calomel electrode at a temperature of 313-333 K. The procedure for recovering of ruthenium, rhodium, palladium, osmium, iridium and platinum from a precious metal containing solution by cathodic separation with the help of a electrolysis cell separated by a cation exchanger membrane, comprises supplying the solution to a cathode chamber, and then mechanically separating or electro-chemically detaching the precious metal. The separation is carried out with a current density of 10-50 mA/cm2> at a cathode potential of -240 to -280 mV related to the potential of a saturated calomel electrode at a temperature of 313-333 K and the electro-chemical separation is stopped, if redox potential, which is measured by silver/silver chloride-combined electrode, of the precious metal solution in the cathode chamber of the electrolysis cell is dropped to less than -100 mV related to the reference electrode. Anolyte nitric acid of concentration 1.5-5 Mol/liter is used as electrolytes, which flow throughable by the cathode- and anode ring of the respective electrode chamber. The base elements separated on the electrode are replaced by anodically dissolving in the nitric acid of the concentration 0.5-2.0 Mol/liter with a potential of 400-1000 mV referred on the potential of the calomel electrode. The palladium is obtained by anodically dissolving the metal precipitate with a potential of 1.0-1.2 V related to the potential of the calomel electrode in sulfuric acid of the concentration 0.5-1.5 Mol/liter nitric acid and 1.0-4.5 Mol/liter hydrochloric acid at a temperature of 313-343 K. The platinum is obtained by anodically dissolving the precipitate with a potential of 1200-1400 mV related to the potential of the calomel electrode in diluted aqua regia of the concentration 0.5-1.5 Mol/liter nitric acid and 1.0-4.5 Mol/liter hydrochloric acid at a temperature of 313-343 K. The rhodium is obtained by anodically dissolving in hydrobromic acid of the concentration 1-5 Mol/liter with a potential of 1000-1400 mV related to the potential of the calomel electrode. The separation takes place on an electrode, which is coated with diamond contaminated with boron. The distance between cathode and membrane is 2.5-5 mm and the cathode is coated by a plastic net. The cathodes are intended as sheet metals. The anodes are intended as sheet metals, perforated plates, expanded metal or fabrics. Spacers from plastic nets with an aperture greater than 60% are present between the electrodes and the membrane. The flow rate of the electrolytes in cathode and anode region is 0.1-10 cm/second. The precious metal components are crushed for the receipt of precious metal solution and disrupted by the extraction with a diluted acid mixture. The precious metal components are released by casing and isolation. The diluted aqua regia of the concentration 0.8-1.2 Mol/liter nitric acid and 2.5-3.5 Mol/liter hydrochloric acid is used for the extraction, which is carried out repeatedly in a temperature of 323-343 K for 4-14 hours. The decomposition solution is agitated while the extraction. Solids are separated from the decomposition solution. The separated solids with a quantity of less than 50% of their volume are washed at diluted aqua regia. The washing solution is added to the decomposition solution and the washing process is repetitively carried out. The cathodes and anodes are used on basis of titanium, niobium and tantalum, which are superficially coated with niobium, rhodium, tantalum, iridium and platinum or its alloys or its oxides.