Research on the Mechanism of Triclosan Degradation by Advanced Oxidation Processes

　　As an antibacterial agent, triclosan (TCS) is extensively used in toys, textiles and personal care products such as handwashing fluids and toothpastes, resulting in TCS's widespread presence in sediment, sewage, lakes and rivers. Due to their endocrine disrupting properties, there are potential human health risks. Recent research has shown that early-life exposure to TCS may adversely impact childhood neurodevelopment. Furthermore, due to the spread of COVID-19 in the world, TCS-containing supplies such as hand sanitizers, disinfectants, and antibacterial drugs are used in large quantities. Microbes play an important role in pollution treatment including TCS. However, they have disadvantages such as time consuming, poor environmental applicability, and incomplete mineralization. When TCS is treated by the microbial method, it is converted into other types of chlorinated compounds if not completely mineralized. Therefore, it is necessary to find an efficient, green, and low-cost degradation treatment technology.

Fig. 1. The mechanism of TCS degradation in CuO/HNTs-PS system

　　The environmental chemistry research team from Institute of Analysis, Guangdong Academy of Science cooperated with teams from Guangdong University of Technology and Hong Kong Polytechnic University to complete this work. They prepared a nano-CuO loaded halloysite nanotube (CuO/HNTs) using a hydrothermal method and applied it to activate PS for the degradation and mineralization of TCS. The morphology, crystal structure, specific surface and surface composition were characterized by SEM, TEM, BET, XRD and XPS. The result showed that the nano-CuO was uniformly loaded on the HNTs to form corn-like structures with a large specific surface area. TCS was totally removed in 180 min under optimized conditions. The mechanism study indicated that even radical reactions (?OH and O2?-) pathway existed; the nonradical mechanism (1O2 and surface electron transport) was dominant to efficient TCS degradation. Moreover, by using FT-ICR MS the degradation intermediates were identified, and transformation pathways were proposed. The toxicity of the solution was also evaluated by the survival rate of the luminescent bacteria, and the toxicity of the solution decreased overall. A stability study showed that CuO/HNTs retained good catalyzing ability even after 5 cycles.

　　Relevant research results were published in Separation and Purification Technology. The first and corresponding author are from Institute of Analysis, Guangdong Academy of Science. This work was supported by the Guangdong Provincial Key R&D Programme, National Key Research and Development Program of China, National Natural Science Foundation of China and the GDAS' Project of Science and Technology Development.

　　Research Information: Huang, Z., Lin, Q., Cai, N., Weng, Q., Xu, J., Gan, S., Chen, C., Zhong, Q., Fu, H., Xia, Y., & Guo, P. (2021). Coexistence of free radical and nonradical mechanisms for triclosan degradation by CuO/HNTs. Separation and Purification Technology, 119318.

　　Link: https://doi.org/10.1016/j.seppur.2021.119318