Abstract

Ozone and chlorine dioxide have been used as oxidants to eliminate gallic acid and epicatechin, two pollutants of distillery wastewaters. In the ozonation, the kinetic regime of absorption has been investigated being slow and moderate to fast for gallic acid and epicatechin ozonations, respectively. Rate constants of ozonation were obtained from competitive oxidation of phenol and the organics studied, being 13,300 and 102,700 M −1 s −1 for ozone-gallic acid and ozone-epicatechin reactions, respectively. Chlorine dioxide was also found to be an effective oxidant. With this oxidant, gallic acid and epicatechin disappear in less than 5 min when the ratio between initial concentrations of chlorine dioxide and the organic is higher than 1. Comparing with ozonation, it was observed that both oxidants have a similar capacity to eliminate both organics, that is, the same amounts of oxidant are needed to oxidize the same amounts of gallic acid and epicatechin. Chlorine dioxide oxidation, however, requires much less time than ozonation to reach that situation because ozone mass transfer slows down the oxidation rate.

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