Abstract:
Platinum-palladium concentrate, obtained from copper anode slime through Kaldo furnace smelting, silver electrolysis, and aqua regia gold parting, is primarily used for palladium recovery. Accurate determination of palladium content in such concentrates is of great significance for the resource utilization of palladium. A lead fire assay enrichment-dimethyl glyoxime gravimetric method was developed for palladium determination in platinum-palladium concentrates. In this method, palladium was pre-enriched by lead fire assay, and the precious metal bead was digested stepwise with nitric acid(1+4) and hydrochloric acid. Using hydrochloric acid as a precipitant, the solution was diluted with water and filtered hot to remove silver interference. In a 10 % hydrochloric acid medium, 40 mL of 20 g/L ethanol solution of dimethyl glyoxime was added, and the mixture was left to stand for 5 h before vacuum filtration to separate palladium for gravimetric determination. The precious metal bead digestion process was optimized in the experiment by first using nitric acid(1+4) for preliminary digestion, preventing the formation of precipitates from the reaction of silver element and chloride ions that hinders further dissolution of beads, followed by hydrochloric acid addition to form aqua regia medium for complete digestion and to supply chloride ions for the generation of silver precipitation as AgCl. With hydrochloric acid as the precipitation agent and 100 mL water added for dilution, the AgCl was coagulated by heating, then immediately filtered hot with slow-rate filter papers so that the silver element is separated and the effect of AgCl precipitation on palladium adsorption is eliminated. In a 10 % hydrochloric acid medium, 40 mL of 20 g/L ethanol solution of dimethyl glyoxime was added to react with palladium and generate precipitants, and the mixture was left to stand for 5 h to ensure complete palladium precipitation from the platinum-palladium concentrate. Interference tests showed that coexisting elements Au(30 mg), Pt(70 mg), Cu(30 mg), Pb(30 mg), Bi(50 mg), and Te(20 mg) did not affect palladium determination. The method exhibited relative standard deviations of 0.37 %-1.05 %(
n=7) and spike recoveries of 99.32 %-100.8 %, with good reproducibility and low cost, making it suitable for batch analysis of palladium in platinum-palladium concentrates.