Degradation mechanism of ammonia nitrogen synergistic with bromate under UV or UV/TiO2.

Abstract

Bromate (BrO3-) and ammonia nitrogen (NH4+) are both typical environmental pollutants: BrO3- has been categorized as one of the Group 2B carcinogen by IARC; an excess of NH4+ might result in the eutrophication of water. The existence of NH4+ could inhibit the transformation of bromide (Br-) to bromate (BrO3-). However, the interaction of NH4+ and BrO3- during the removal process is not clear. This study intends to disclose the mutual relationships of ammonia nitrogen and bromate ions under UV irradiation or UV/TiO2 conditions. Without UV irradiation, BrO3- and NH4+ were both stable even under the presentation of each other. Under UV irradiation or UV/TiO2 conditions, BrO3- and NH4+ promoted the degradation of each other, showing the synergistic degradation mechanism. In the neutral environment, both of BrO3- and NH4+ could be transformed effectively. Furthermore, NH4+ accelerated the transformation of BrO3- to Br- at the reaction beginning and the existence of BrO3- is beneficial for the transformation of NH4+ to N2.