Polyoxometalates entrapped in sol-gel matrices as electron exchange columns and catalysts for the reductive de-halogenation of halo-organic acids in water

Halo-organic acids in aqueous solutions are widespread pollutants. An enormous number of technologies have been proposed for their elimination. In this context, reducing electron exchange columns seem to be an optimal solution for their degradation, as they do not introduce any new chemical into the solution to be purified. The electron exchange columns used in this study consist of entrapped polyoxometalates (POMs) in silica sol-gel matrices that were used as the reducing medium for the reductive de-halogenation of Br₃CCO₂ ⁻, Cl₃CCO₂ ⁻, BrCH₂CO₂ ⁻ and ClCH₂CO₂ ⁻. The same matrices were also applied as catalysts for the reduction of the investigated halo-acetates by BH₄ ⁻. Surprisingly, the results indicate that the mechanisms of de-halogenation of Br₃CCO₂ ⁻, Cl₃CCO₂ ⁻, BrCH₂CO₂ ⁻ and ClCH₂CO₂ ⁻ differ from each other.