Efficient photoreductive decomposition of N-nitrosodimethylamine by UV/iodide process.
N-nitrosodimethylamine (NDMA) has aroused extensive concern as a disinfection byproduct due to its high toxicity and elevated concentration levels in water sources. This study investigates the photoreductive decomposition of NDMA by UV/iodide process. The results showed that this process is an effective strategy for the treatment of NDMA with 99.2% NDMA removed within 10min. The depletion of NDMA by UV/iodide process obeyed pseudo-first-order kinetics with a rate constant (k1) of 0.60±0.03min-1. Hydrated electrons (eaq-) generated by the UV irradiation of iodide were proven to play a critical role. Dimethylamine (DMA) and nitrite (NO2-) were formed as the main intermediate products, which completely converted to formate (HCOO-), ammonium (NH4+) and nitrogen (N2). Therefore, not only the high efficiencies in NDMA destruction, but the elimination of toxic intermediates make UV/iodide process advantageous. A photoreduction mechanism was proposed: NDMA initially absorbed photons to a photoexcited state, and underwent a cleavage of NNO bond under the attack of eaq-. The solution pH had little impact on NDMA removal. However, alkaline conditions were more favorable for the elimination of DMA and NO2-, thus effectively reducing the secondary pollution.
State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
Zhuyu
Z
Sun
State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China. Electronic address: myrazh@tongji.edu.cn.
Chaojie
C
Zhang
State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
Xiaoyun
X
Zhao
State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
Jing
J
Chen
State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
Qi
Q
Zhou
Hydrated electrons; Mechanism; N-nitrosodimethylamine; Photoreduction; pH effect