EXAMPLES 1 -3

One gram samples each of hoof meal，tapestry white wool，and raw chicken feathers were placed in centrifuge tubes with 25 ml of 100 ppm solutions of chloroplatinic acid and placed on a reciprocal shaking machine at 28℃. Each cycle was originally for one day. At the end of each cycle, the solution in each tube was replaced with fresh solution. After several cycles, the cycle times were increased to two or more days as indicated in Table I. Assay of residual platinum after centrifugation of the solids was done colorimetrically using the stannous chloride test. At the end of 38 cycles, 90 percent of the platinum in the solution had been recovered by the hoof meal with a total recovery of 85.7 mg platinum per gram of hoof meal. At the end of 35 cycles 81 percent of the platinum had been recovered by the wool samples for a total of 70.5 mg of platinum per gram of wool. Ninety two percent of the platinum was recovered by the feathers in 35 cycles for a total recovery of 80.6 mg of platinum per gram of feathers. Results are summarized in Table II. 

EXAMPLE 4

The effectiveness of feathers for the recovery of precious metals from dilute solutions is indicated in a series of tests with the results summarized in Table III. In these tests, one liter samples of an inermediate refinery solution relatively rich in platinum and rhodium was contacted with successive 50 gram portions of proteinaceous material at 28°C. With continuous agitation for 20 hours each exposure. Residual metals concentrations in milligrams per liter (mg/I) and percentages of each metal recovered (% ) are shown in the table.

Similarly，a 50 gram portion of cleaned goose feathers，in a single exposure, recovered 67 percent of the palladium, 31 percent of the rhodium，and an undetermined amount of platinum from a one liter sample of the same intermediate refinery solution.

EXAMPLES 5

Hog hair ( Wilson & Company) was tested and proved effective for recovery of platinum and palladium from the test solution of Example 4 when contacted with the test solution at 28 °C. with continuous agitation for 20 hours at a dosage of 100 grams hog hair per liter of test solution. Test results are summarized in Table IV. 

It is evident from the foregoing examples that proteinaceous animal waste products selected from the group consisting of feathers, hair, hoof meal, and horn meal, are effective materials for the removal of precious metals from dilute solutions.