Recovery of PGM from Virgin Automotive Catalysts by Cyanide Leaching.
Atkinson-GB; Desmond-DP; Kuczynski-RJ; Walters-LA
Proc Seminar of Int'l Precious Metals Institute Las Vegas Nevada, 1989 :109-115
The U.S. Bureau of Mines investigated leaching virgin automotive catalytic convertor biscuits with cyanide solution for recovery of platinum-group metals to establish baseline leaching parameters for expansion of the technology to leaching used catalysts. Two types of monoliths were tested: an oxidation type with 500 ppm pd and 1,000 ppm pt, and a three-way type with 2,000 ppm pt and 200 ppm rh. Monoliths were crushed to minus 12, plus 30 mesh. Preleaching treatment of the biscuits was necessary for high recovery. This involved oxidation and reduction. Best results were obtained with air for 1 h at 550 deg c followed by h2 reduction for 1 h at 550 deg c. Twenty-gram samples were leached in stirred beakers with 100 ml of solution for 1 h at 80 deg c. Five percent nacn-1 pct proprietary promoter dissolved 99 pct of the pd and 98 pct of the pt in the oxidation catalyst. This reaction consumed 20 lb nacn per ton of catalyst. Five percent nacn-1 pct promoter dissolved 98 pct pt and 98 pct rh from the three-way catalyst and consumed 150 lb nacn per ton of catalyst.
Proc. Seminar of Int'l Precious Metals Institute, Las Vegas, Nevada, 1989, PP. 109-115