Theoretical Analysis of Changes in the Solution Composition during Anodic Electrolysis of Bromide

Resumo

The changes in indicator-electrode potential and (quasi)equilibrium solution composition in the anodic compartment of a model electrolyzer initially filled with aqueous electrolyte containing 0.5 M concentration of bromide anions are calculated under the condition that pH 2 is maintained constant in this compartment. The theoretical analysis is carried out for three different hypotheses concerning the possible depth of electrolysis and the nature of processes involved: (1) no bromine compounds with positive degree of oxidation are formed; (2) bromine compounds with the degree of oxidation not higher than +1 are formed; (3) the process can involve the formation of both bromate ions and bromine compounds with the lower degrees of oxidation (\({\text{Br}}_{{\text{3}}}^{ - },\)\({\text{Br}}_{{\text{5}}}^{ - },\) Br₂, BrO^–, HBrO) in solution as well as the liquid phase of bromine \(\left( {{\text{Br}}_{{\text{2}}}^{{{\text{liq}}}}} \right).\) All electrochemical and chemical reactions involving bromine-containing species taken into account within the framework of hypotheses of system evolution 1, 2, and 3 are assumed to be (quasi)equilibrium, and the electric current through the cell separator is assumed to be provided by supporting electrolyte ions. Methods are proposed for experimental determination of the version of evolution of Br-containing anolyte during electrolysis.