INFLUENCE OF ACETATE AND CITRATE IONS ON CATHODIC REDUCTION OF Yb(III) AT MERCURY ELECTRODES
Relevance. Ytterbium, its alloys and compounds are characterized by valuable thermoelectric, magnetic and optical properties, ytterbium-containing materials are used in military and nuclear industries. Due to the high chemical activity, as well as similarities with other rare earth elements, ytterbium isolation technologies include a large number of operations, among them deposition, electrolysis, cementation, adsorption, etc. The peculiarity of ytterbium (as well as europium and samarium) in comparison with other rare earth elements is the possibility of cathodic deposition at the mercury electrode and formation of amalgam at relatively low negative potentials. In this regard, the study of the regularities of the electrode processes involving ytterbium is an urgent task both from a fundamental and technological point of view. The aim of the research is to determine the features of the effect of complexing agents (acetate and citrate ions) on cathodic reduction of Yb(IlI) at mercury electrodes. Objects: ytterbium oxide, perchloric and acetic acids, solutions of salts (NaClO, LiCl, N(C<sub>2</sub>H<sub>5</sub>)<sub>4</sub>Cl, sodium acetate and citrate) and alkali (NaOH). Methods: direct and alternating current polarography, cyclic voltammetry with mercury electrodes. Results. The range of potential of the cathodic process Yb(III)^Yb(II) (1-1Cr<sup>4</sup>...1-10r<sup>3</sup> M) at mercury electrodes (dropping, stationary) in non-complexing and complexing (acetate, citrate) supporting electrolytes in a wide pH range 2...9 has been refined. The effect of complexation of Yb(III) on the ratio of ytterbium and hydrogen ions reduction currents and on the stability of the intermediate product Yb(II) of the cathode process in the solution medium was established. The paper introduces the catalytic nature of the chemical reaction of Yb(II) oxidation by hydrogen ions occurred in the near-cathode layer of the solution to the process Yb(III)→Yb(II) at potentials -1,3...-1,5 V (vs. Ag/AgCl/KCl). Interpretation of the results of electrochemical studies was carried out using the calculated diagrams E-pH for Yb-H<sub>2</sub>O-CH<sub>3</sub>COO and Yb-H<sub>2</sub>O-Cit<sup>3-</sup> systems in comparison with the system without complexing agent. The importance of taking into account Yb (III) state in solutions and electrolysis conditions for the cathode process is discussed.