ИСТИНА

Noble metals (NMs: Ru, Rh, Pd, Ir, Pt и Au) are widely used in various industries, and the demand for these metals is steadily growing. However, the depletion of natural resources of NMs leads to the necessity of their recovery from different secondary sources and technogenic materials. NMs are recovered from secondary raw materials by precipitation, extraction and sorption on various organic polymer sorbents. Of particular importance in this case is sorption preconcentration on ion-exchangers, which is characterized by high efficiency, selectivity and ecological safety. In addition, sorption preconcentration on ionexchangers can be easily combined with methods employed in subsequent determination of NMs (for example, ICP-AES, ICP-MS). The NMs’ chlorocomplexes are the most well studied and important, as aqueous chloride solutions is the only cost-effective medium in which all the NMs can be brought into solution and concentrated. On the other hand, NMs’ ions form stable complexes with protonated Ncontaining ligands (various amines) in acidic media. This fact allows us to choose selective sorbents based on hyper-crosslinked polystyrene with different covalently bonded aminogroups for group extraction of NMs from solutions of complex composition. In this work StrataX-AW with ethylenediamine groups (Phenomenex, USA), DETA with ethylenetriamine groups (MSU, Russia) and Stirosorb-416 with dimethylbenzylamine groups (INEOS RAS, Russia) were used as weak anion exchange sorbents. Sorption preconcentration of NMs was carried out in a dynamic mode from strong acidic solutions using a flow mixing scheme. The most effective sorbent for the quantitative sorption of Ir, Pd and Au from model solutions was StrataX-AW; for Ir, Rh, Pd, Pt and Au – Stirosorb-416 and for the group NMs sorption – DETA. The extraction of NMs’ chlorocomplexes from solutions with various acidities was investigated. The optimal acidity approximately 1 mol L-1 HCl (after flow mixing) was chosen for quantitative group sorption of NMs at low flow rate (1.0−1.2 mL min-1). The main reason of quantitative NMs’ sorption may be the interaction of negatively charged chlorocomplexes with protonated N-atoms of the sorbent. For recovery of NMs in this case it is necessary to deprotonate these N-atoms. In this work, aqueous and aqueous-ethanol solutions of ammonia, sodium tetraborate and potassium oxalate were used for desorption of NMs. The maximum recovery was achieved by using of 5−10% aqueous ammonia as eluent. NMs concentrations in eluates were determined by ICP-MS. This work was supported by the Russian Foundation for Basic Research (RFBR, grant 16-03- 00428).