Determination of Au, Pd, Pt, and Rh inks, ores, concentrates, and sulfide float samples by ICP-OES/FAAS after reductive coprecipitation using Se as collector

摘要

A method is described for the determination of gold, palladium, platinum, and rhodium inks, ores, and concentrates, including sulfide float samples, by inductively coupled plasma optical emission spectrometry (ICP-OES) and flame atomic absorption spectroscopy (FAAS). The samples were analyzed after decomposition with a mixture of hydrofluoric acid aqua regia and hydrochloric acid potassium chlorate for sulfide matrix samples. Fusion was used for any insoluble residue with sodium peroxide and the analytes were collected using selenium as the collector and stannous chloride as the reductant. The method was tested for Au, Pd, Pt, and Rh with three Canadian certified reference standards, MA-lb, PTC-1, and PTM-l, and one National Institute of Metallurgical Standard from South Africa, SARM-7, and then applied to the determination of these elements in some ore samples and sulfide-rich flotation products from the Jaduguda Uranium deposits in Singhbhum (Bihar, India). The results obtained by this method compare favorably with the certified values. The gold and palladium values obtained in sulfide float samples are discussed and compared with the values obtained by the ICP-MS methods. Detailed studies were carried out to precipitate gold and platinum- group elements (PGEs) using different precipitating agents such as H sub 2 S, Na sub 2 S in the presence of various carrier elements. Investigations were also carried out using Se as the collector and various reducing agents such as sulfurous acid (SO sub 2 ), hypophosphorous acid (H sub 3 PO sub 2 ), ammonium formate (HCOO NH sub 4 ), hydroquinone [C sub 6 H sub 4 (OH) sub 2 ], and hydroxyl ammonium chloride (NH sub 2 OH HCl). The recoveries of Au, Pd, and other PGEs are discussed. The relative error for one sulfide float sample was established to be within plus/minus1.0 to 1.5% RSD for both Au and Pd values using the proposed method.