THE DIFFERENCE OF THE COMPLEX FORMATION OF THE RARE‑EARTH ELEMENTS WITH THE L-MALIC ACID AT METAL ION EXCESS

Vladimir Buzko, Igor Sukhno,* and Varvara Klimova

Kuban State University, Chemistry Department, 350040, Krasnodar, Stavropolskaya Street 149, Russia

e-mail: Sukhno@chem.kubsu.ru

Abstract

The complex formation of the rare-earth ions (Ce³⁺, Pr³⁺, Nd³⁺, Sm³⁺) with L-malic acid (H₃Mal) in the aqueous solutions was studied by pH-metric titration method in pH region 3.00 to 9.00 and constant ionic strength 0.1 M KCl. The ratios of the concentrations of the L-malic acid and the rare-earth elements (Ln) were 1:1and 1:2. The compositions and the stability constants of the rare-earth element complexes with L-malic acid were calculated by SuperQuad program for complex equilibria. It was shown, that in addition to 1:1 complexes, the hydroxocomplexes, protonated and polynuclear complexes of the rare-earth elements are also formed.

Key words: complex formation, lanthanides, L-malic acid