Synthesis and study of bismuth(III) oxalates precipitated from mineral acid solutions

Abstract

Bismuth oxalates of the compositions BiOH(C2O4), Bi2(C2O4)3·6H2O, Bi2(C2O4)3·7H2O, and Bi2(C2O4)3·8H2O were obtained by precipitation from bismuth solutions in perchloric, nitric, and hydrochloric acids with addition of oxalic acid. Compound compositions were confirmed by X-ray powder diffraction and chemical analysis, IR and Raman spectroscopy, and thermogravimetry. It has been shown that in the composition of bismuth(III) oxalate hydrates Bi2(C2O4)3· х H2O bismuth cation is coordinated by the oxygen atoms of carboxyl groups of oxalate ions and water molecules in the same way, and compositions, taking into account the structural features, are described by the general formula {[Bi2(C2O4)3(H2O)4]∙( x -4)H2O} n . Conditions for the oxidative thermolysis of BiOH(C2O4) and Bi2(C2O4)3·7H2O to yield the tetragonal modification of bismuth oxide β-Bi2O3 were determined.