Abstract
Abstract
Benzothiazoles (BTs) appear in the environment mainly due to their production and use as industrial chemicals in the leather and wood industries, and mainly as vulcanization accelerators in rubber production. Doubts about the possibility to biodegrade these compounds efficiently have been raised. Ozonation has been proposed in literature as a suitable method for detoxification of wastewater containing 2-mercaptobenzothiazole (MBT). Feasibility of the ozonation process to remove selected BTs and facilitation of subsequent biological wastewater treatment were studied in our work. Ozonation experiments were carried out in a lab-scale jet loop ozonation reactor. Synthetic wastewater contained MBT, BT, 2-hydroxybenzothiazole (OHBT), 2-aminobenzothiazole (ABT), benzothiazole-2-sulfonate (BTS), and aniline as the main organic pollutants of industrial wastewater. Kinetics of organic pollutant removal was investigated at pH=8.5 and 5.8. Significantly higher influence of the pH value (thus also the influence of ozone reaction mechanisms) on the BT removal in the presence of other BT derivatives in comparison with published data for single BT removal follows from the results of our work. Higher removal rates of MBT and BT were observed at higher pH value. On the other hand, removal rate of MBT was 2.8 times higher compared to that of BT. MBT and BT removals occurred according to a first-order reaction. Observed pathway of the MBT and BT removals differed from that presented in literature as a result of single MBT ozonation in pure water. Accumulation of BTS was observed as the concentration of MBT declined during the ozonation performed at both the pH values. After the removal of MBT, BTS reduction was also realized. At the same time, the removal rate of BT significantly increased. The removals of BT, OHBT, and ABT occurred simultaneously during this period of ozonation. Significantly higher conversions of OHBT and ABT were observed also during the ozonation carried out at higher pH.
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