Pyruvic Acid Removal from Water by the Simultaneous Action of Ozone and Activated Carbon

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Abstract
Activated carbon (AC) has been used to catalyze the ozonation of pyruvic acid in water. Pyruvic acid conversions were found to be 9 and 37% after 90 min of single ozonation and single adsorption with 40 gL−1 AC, respectively, while 82% was reached at the same conditions during the AC catalytic ozonation. Also, for similar conditions, mineralization reached values of 67% in the AC catalytic ozonation against hardly 5% in the non-catalytic experiment. The process likely develops through both adsorption of ozone and pyruvic acid on the AC surface and generation of hydroxyl radicals that eventually is the responsible oxidizing species. Rate constants for both non-catalytic ozonation and AC-Ozone catalytic surface reaction, at 20°C and pH 7.5, were found to be 0.025 min−1 and 87.9 Lg−1s−1, respectively. For AC concentrations higher than 2.5 gL−1 gas-liquid mass transfer of ozone constituted the limiting step. At lower concentrations, internal diffusion plus surface reaction controlled the process rate.