Abstract

The equilibrium distribution of nicotinic acid and iron(III) between an aqueous solution and Dowex-50 sulfonic cation exchanger has been investigated. The equilibrium constants of ligand sorption of nicotinic acid by sulfonic cation Dowex-50 containing protons or cations of iron have been determined. An algorithm is proposed for calculating the equilibrium composition of an aqueous solution of a mixture of nicotinic acid and FeCl₃ allowing one to get sulfonic cation exchanger Dowex-50 with a predetermined counter-ionic composition. The predictive ability of the proposed algorithm is confirmed by experimental studies of the process of sorption of complexes of nicotinic acid and iron(III) from aqueous solutions of H and Fe(III) forms of Dowex-50 sulfonic cation exchanger. It has been shown that, in a sulfonic cation exchanger equilibrated with an aquatic solution having a ratio of molarities of cations Н⁺ : [H₂L]⁺ : Fe³⁺ : [FeL]²⁺equal to 1 : 1 : 0.16 : 0.1, the content of complex cations [FeL]²⁺ is 44.5 wt %.