ИСТИНА

Noble metals (NMs: Ru, Rh, Pd, Ir, Pt and Au) form an important group of elements. Their consumption is constantly growing up in technologically developing world. Concentrations of NMs in geological matrix are of prime importance for exploration of rock-forming processes, Earth’s crust and mantle interactions. Geochemistry of NMs is a powerful instrument for evaluation of the post volcanoes eruption processes and meteorite falls aftermath. NMs’ host rocks generally consist of sulfide minerals, basic and ultrabasic rocks, where the NMs’ content is extremely low (10-9–10-6 wt%). For this reason, the determination of such low concentrations of NMs in rocks is a difficult analytical task. In general, appropriate for this purpose methods of analysis include three stages: chemical decomposition of the sample, separation from matrix and determination of the analytes. Nickel sulphide fire-assay (NiS-FA) and acid digestion under heating are most often used techniques for decomposition of geological objects. Direct determination of NMs in solution after acid digestion by ICP-MS, as in the case of NiS-FA technique, is problematic due to significant influence of macro- and microelements of the rock on analytical signals of analytes. Therefore, the stage of NMs’ preconcentration and matrix removal is necessary while using both of these variants of sample pretreatment. The efficiency of sorption of Ru, Pd, Ir, Pt and Au (NMs) on neutral sorbent Stirosorb-514 from the final solution after acidic digestion of the rock samples was investigated. It was found that general saline composition of the solutions strongly affects the degree of NMs extraction. It was found that different macro-components of rocks (Na, Ca, Mg, Al and Fe) specifically affect the extraction efficiency. The addition of Fe(III) in the final solution after a rock sample digestion increases the efficiency of Ir sorption up to 90%. The NiS fire-assay (NiS-FA) of rock samples plays the key role in achieving the quantitative extraction of NMs. It was proved that Ni concentration up to 4 g L-1 does not affect the efficiency of Ru sorption from solution after acid digestion. Sorption of five NMs (Ru, Pd, Ir, Pt, Au) on Stirisorb-514 of (97±3%) was achieved using combination of NiS-FA and addition of 2 g L-1 Fe3+ in final solution. Quantitative desorption of four NMs (Ru, Pd, Pt and Au) was realized using 1 mol L-1 HCl in ethanol as eluent.