Decomposition of sulfamethoxazole and trimethoprim by continuous UVA/LED/TiO2photocatalysis: Decomposition pathways, residual antibacterial activity and toxicity.
In this study, continuous LED/UVA/TiO2photocatalytic decomposition of sulfamethoxazole (SMX) and trimethoprim (TMP) was investigated. More than 90% of SMX and TMP were removed within 20min by the continuous photoreactor (with the initial concentration of 400ppb for each). The removal rates of SMX and TMP decreased with higher initial antibiotics loadings. SMX was much easier decomposed in acidic condition, while pH affected little on TMP's decomposition. 0.003% was found to be the optimum H2O2dosage to enhance SMX photocatalytic decomposition. Decomposition pathways of SMX and TMP were proposed based on the intermediates identified by using LC-MS-MS and GC-MS. Aniline was identified as a new intermediate generated during SMX photocatalytic decomposition. Antibacterial activity study with a reference Escherichia coli strain was also conducted during the photocatalytic process. Results indicated that with every portion of TMP removed, the residual antibacterial activity decreased by one portion. However, the synergistic effect between SMX and TMP tended to slow down the antibacterial activity removal of SMX and TMP mixture. Chronic toxicity studies conducted with Vibrio fischeri exhibited 13-20% bioluminescence inhibition during the decomposition of 1ppm SMX and 1ppm TMP, no acute toxicity to V. fischeri was observed during the photocatalytic process.
Department of Civil and Environmental Engineering, National University of Singapore, 10 Kent Ridge Cresent, 119260, Singapore.
Qinqing
Q
Cai
Department of Civil and Environmental Engineering, National University of Singapore, 10 Kent Ridge Cresent, 119260, Singapore. Electronic address: ceehujy@nus.edu.sg.
Jiangyong
J
Hu
D048908:Aliivibrio fischeri / Q000187:drug effects; D002384:Catalysis; D004926:Escherichia coli / Q000187:drug effects; D006861:Hydrogen Peroxide / Q000737:chemistry; D007202:Indicators and Reagents; D055668:Photochemical Processes; D013420:Sulfamethoxazole / Q000737:chemistry* / Q000528:radiation effects / Q000633:toxicity; D014025:Titanium; D014295:Trimethoprim / Q000737:chemistry* / Q000528:radiation effects / Q000633:toxicity; D014466:Ultraviolet Rays
D007202:Indicators and Reagents; C009495:titanium dioxide; D014295:Trimethoprim; D006861:Hydrogen Peroxide; D014025:Titanium; D013420:Sulfamethoxazole
Photocatalysis; Sulfamethoxazole; TiO; Trimethoprim; UVA/LED