Surface-catalyzed chromium(VI) reduction: Reactivity comparisons of different organic reductants and different oxide surfaces

Cr-VI reduction by low molecular weight organic compounds with various functional groups was examined in the presence and absence of oxide surfaces. Surface-catalyzed Cr-VI reduction has been demonstrated with alpha-hydroxyl carboxylic acids (glycolic acid, lactic acid, mandelic acid, and tartaric acid) and their esters (methyl glycolate, methyl lactate, and methyl mandelate), with alpha-carbonyl carboxylic acids (glyoxylic acid and pyruvic acid), with oxalic acid, and with substituted phenols (salicylic acid, 4-methoxyphenol, and resorcinol). Both goethite (alpha-Fe00H) and aluminum oxide (gamma-Al2O3) exert an appreciable catalytic effect, although somewhat less than that observed with titanium dioxide. This study indicates that surface-catalyzed Cr-VI reduction may occur in soils, sediments, aquifers, and other aquatic environments rich in mineral surfaces.