Advanced oxidation for the treatment of resin and fatty acids

Experiments were conducted to investigate the applicability of advanced oxidation processes (AOPs) to reduce the concentrations of resin and fatty acids (RFAs) found in pulp mill effluents. The focus of this study is on the reduction of toxicity due to RFAs, specifically abietic and linoleic acids, through their reaction with ozone and the resulting change in toxicity. The oxidation kinetics of the reaction between dissolved ozone and either RFA at pH of approximately 7.3 were evaluated using a continuous flow stirred tank reactor (CFSTR). The overall kinetics were modeled as a second order reaction being first order in respect to both ozone and RFA. At 20°C, the overall rate constants for abietic and linoleic acids were predicted to be 3.47 × 103 and 1.31 × 104 M −1s−1, respectively. It was observed that greater than 85% reduction of 12.0 mg/L linoleic acid and 70% reduction of 4.5 mg/L abietic acid were achieved with ozone doses on the order of 2.5 mg/L. Also, acute toxicity was investigated using Microtox® assays and it was found that treated abietic acid was more toxic than the raw abietic acid sample, whereas the treated linoleic acid showed a decrease in toxicity compared to the raw sample.