Removal of benzotriazole from secondary municipal wastewater effluent by catalytic ozonation in the presence of magnetic alumina nanocomposite

Abstract

This research aimed at studying the degradation of benzotriazole (BT), an abundant contaminant in many natural waters, using catalytic and non-catalytic ozonation processes performed in a semi-continuous reactor. Magnetic alumina nanocomposite (MANC) was successfully synthesized and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and vibrating-sample magnetometer (VSM). The results revealed that the MANC dramatically enhanced the removal rate of BT. Experiments were evaluated at different solution pH values, catalyst doses, initial benzotriazole concentrations, and oxygen gas flow rates. The results showed that the removal rate of BT strongly influenced by the initial pH, and it increased by enhancing the pH value from 2 to 10 in both catalytic and non-catalytic ozonation. However, the catalyst showed its highest activity at pH near to its point of zero charge, indicating the critical importance of surface hydroxyl groups of alumina. Introducing tert-butyl alcohol (TBA) to the reactor highly decreased the degradation efficiency in the non-catalytic ozonation process, suggesting that the MANC catalyzes the decomposition of ozone to hydroxyl radical. The catalyst stability experiments after four successive runs showed that the catalyst was efficient and stable. Finally, the degradation of BT in secondary municipal wastewater effluent was studied under optimum operating conditions in order to examine the performance of the catalyst in the presence of components available in real streams. The results indicated no significant decrease in the performance of the catalyst. Furthermore, the catalytic ozonation process had also a great performance for removing phosphorus.