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

A method is described for the determination of gold, palladium, platinum, a nd rhodium in rocks, ores, and concentrates, including sulfide float sample s, by inductively coupled plasma optical emission spectrometry (ICP-OES) an d flame atomic absorption spectroscopy (FAAS). The samples were analyzed af ter decomposition with a mixture of hydrofluoric acid aqua regia and hydroc hloric acid potassium chlorate for sulfide matrix samples. Fusion was used for any insoluble residue with sodium peroxide and the analytes were collec ted 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-1b, PTC-1, and PTM-1, 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 flotat ion products from the Jaduguda Uranium deposits in Singhbhum (Bihar, India) . The results obtained by this method compare favorably with the certified values. The sold 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 el ements (PGEs) using different precipitating agents such as H2S, Na2S in the presence of various carrier elements. Investigations were also carried out using Se as the collector and various reducing agents such as sulfurous ac id (SO2), hypophosphorous acid (H3PO2), ammonium formate (HCOO NH4), hydroq uinone [C6H4 (OH)(2)], and hydroxyl ammonium chloride (NH2 OH HCl). The rec overies of Au, Pd, and other PGEs are discussed. The relative error for one sulfide float sample was established to be within +/-1.0 to 1.5% RSD for b oth Au and Pd values using the proposed method.