Ozone treatment for the degradation of resin and unsaturated fatty acids at low temperatures

Ozonation of abietic and linoleic acids (resin and fatty acids; RFAs) was investigated at various pHs and low temperatures (0 to 10 °C) using a rapid-scan stopped-flow spectrophotometer. Degradation of abietic and linoleic acids could be enhanced by manipulating reaction conditions, including ozone dose, temperature, and pH. Improved degradation of RFAs at higher pHs suggests hydroxyl radical reaction is playing an important role during the ozonation. The apparent overall second order rate constants were determined based on the pseudo-first order rate constants for acids and for ozone. At pH 11 and 10 °C, they were calculated as 6.6 x 10³ M^–1· s^–1 and 1.0 x 10⁴ M^–1· s^–1 for abietic and linoleic acids, respectively. The acute toxicity assessed by Microtox^® bioassay increased after ozonation by 140% in the case of abietic acid, whereas it reduced to half in the case of linoleic acid. Key words: ozone, oxidation kinetics, resin acids, fatty acids, toxicity, rapid-scan stopped-flow spectrophotometry, pulp mill effluent.