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 s urfaces. 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 la ctate, and methyl mandelate), with alpha-carbonyl carboxylic acids (gl yoxylic acid and pyruvic acid), with oxalic acid, and with substituted phenols (salicylic acid, 4-methoxyphenol, and resorcinol). Both goeth ite (alpha-Fe00H) and aluminum oxide (gamma-Al2O3) exert an appreciabl e catalytic effect, although somewhat less than that observed with tit anium dioxide. This study indicates that surface-catalyzed Cr-VI reduc tion may occur in soils, sediments, aquifers, and other aquatic enviro nments rich in mineral surfaces.