The large amount of oil sands processaffected water (OSPW), produced from the extraction of oil from oil sands in Alberta, Canada, has demonstrated both acute and chronic toxicity to many species due to the presence of naphthenic acids (NAs). The Bzero discharge^policy posted by the Alberta government presents a major challenge for the oil sands industries. In this study, ozonation was used to remove model NAs from water. It was found that the removal of NAs increased with the temperature. The kinetics of direct ozonation between molecular ozone and NAs was investigated in the presence of a radical scavenger, sodium bicarbonate. The rate constants of the direct ozonation at 5, 15 and 25°C were determined to be 0.67, 2.71 and 8.85 M −1 s −1 , respectively, and the activation energy of the direct ozonation was found to be 88.85 kJ mol −1 . The kinetics of indirect ozonation was also studied. By using pCBA as a hydroxyl radical probe compound to determine the hydroxyl radical concentration and applying the ratio of hydroxyl radical concentration to dissolved ozone concentration, R ct , the rate constants of the indirect ozonation of NAs were found to be 1.12×10 8 , 1.78×10 8 and 2.33×10 8 M −1 s −1 at 5, 15 and 25°C, respectively. In addition, from the Arrhenius plot of the rate constants, the activation energy of the indirect ozonation was found to be 25.41 kJ mole −1 .

Naphthenic acids (NAs) are toxic constituents of oil sands process-affected water (OSPW) which is generated during the extraction of bitumen from oil sands. NAs consist mainly of carboxylic acids which are generally biorefractory. For the treatment of OSPW, ozonation is a very beneficial method. It can significantly reduce the concentration of NAs and it can also convert NAs from biorefractory to biodegradable. In this study, a factorial design (2(4)) was used for the ozonation of OSPW to study the influences of the operating parameters (ozone concentration, oxygen/ozone flow rate, pH, and mixing) on the removal of a model NAs in a semi-batch reactor. It was found that ozone concentration had the most significant effect on the NAs concentration compared to other parameters. An empirical model was developed to correlate the concentration of NAs with ozone concentration, oxygen/ozone flow rate, and pH. In addition, a theoretical analysis was conducted to gain the insight into the relationship between the removal of NAs and the operating parameters.

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The oil sands process‐affected water (OSPW), produced in large amounts during the extraction of crude oil from oil sands, is toxic mainly due to the presence of naphthenic acids (NAs), among other constituents. Ozonation is an effective method for the removal of NAs. To provide information for better control of NAs ozonation, models based on mass balance were developed in this study to predict the concentration profiles of commercial NAs, dissolved ozone, and gaseous ozone during the process. It was found that the developed models successfully predicted the concentrations of commercial NAs and gaseous ozone. For the dissolved ozone concentration, the developed model can predict the equilibrium concentrations well. However, the actual ozone consumption was higher than that predicted by the model at the initial period of the ozonation process. This deviation possibly resulted from the inapplicability of the gas‐liquid equilibrium conditions at the initial high rate stage of the reaction. In addition, the Henry's law constant and the overall mass transfer coefficient for the given system were determined experimentally. Also investigated in this study was the effects of inlet gaseous ozone concentration into the reactor on the removal of NAs and on the concentration of dissolved ozone. As expected, the increase in inlet ozone concentration enhanced the removal of NAs and increased the concentration of dissolved ozone.

In an attempt to maximize the amount of ozone reacting with lignin inside humid wheat straw, some of the ozone-reactive lignin degradation products were washed away before a second ozonolysis delignification stage. The total contact time for the two stages was kept the same as that for a one-stage process for comparison. A significant decrease in the Acid Insoluble Lignin (AIL) content of the straw resulted: from 13.04 wt. % (after a 30-min one-stage ozonolysis) to 9.34 wt. % (after a 30-min two-stage ozonolysis, separated by a washing step). This significant improvement was accompanied by an increase in released fermentable sugars from an enzymatic hydrolysis. The yield increased from 60% theoretical sugars to 80%. A further improvement in AIL (down to 7.36 wt. %) and released sugars (up to 90% theoretical) occurred when the moisture content (MC) of the straw entering the second stage was adjusted to the optimum value of the straw entering first stage (45 wt. %, predicted from an experimental design). The authors believe this is the first time results are published for the introduction of a two-stage process separated by a washing step. 542