Catalytic Converter Processing for Platinum Group Metals

Introduction to the Process

• The video demonstrates a method for processing catalytic converters to recover platinum group metals (PGMs) from honeycomb ceramic.

• A simple test is shown where heating the ceramic causes it to glow red, indicating the presence of PGMs. After extinguishing the flame, blowing propane on the hot surface keeps it glowing.

Initial Steps in Recovery

• A one-kilogram sample of ceramic powder is mixed with 500 mL of hydrochloric acid and heated to 80°C. Sodium hypochlorite (bleach) is added in portions, which appears to facilitate a color reaction indicating progress.

• A Stannous chloride test verifies the presence of PGMs after adding 200 mL of bleach over four hours; the solution is then filtered using cotton and fabric to remove residual materials.

Refining Palladium and Platinum

• Zinc powder is introduced to cement out metals from the solution, which are then transferred for further refinement with nitric acid that dissolves palladium while leaving platinum intact. The solution is boiled to ensure complete dissolution of palladium before filtering out remaining platinum.

• The black residual powder may contain a mix of platinum and rhodium; hydrochloric acid is added for further purification steps involving filtration and washing processes.

Testing Solutions for PGMs

• Both palladium nitrate and platinum solutions are placed on a hotplate for evaporation; color changes indicate successful extraction: orange/brown suggests palladium, while olive green indicates platinum's presence.

• Ammonium chloride is used in testing the platinum solution, precipitating it as ammonium tetrachloroplatinate salt after eliminating residual nitric acid with sulfuric acid. Unfortunately, some footage was lost during this step.

Precipitation Processes

• For palladium recovery, hydrochloric acid is added to convert palladium nitrate into palladium chloride before precipitation occurs as yellow palladium diamine salt through slow addition of ammonia solution, resulting in pink precipitate formation known as Vogel's salt. This will dissolve upon further ammonia addition.

• After cooling down the mixture in a cold water bath, more hydrochloric acid is added again leading towards final precipitation steps that take about an hour before filtering out solidified palladium salts from the liquid phase.

Final Conversion Steps

• To ensure complete recovery, DMG (dimethylglyoxime) is added post-filtration as an additional measure against any remaining dissolved palladium salts before converting both platinum and palladium salts into metal forms using sodium formate solutions prepared with sodium hydroxide and formic acid under boiling conditions.