Photocatalytic degradation of trihalomethanes and haloacetonitriles on graphitic carbon nitride under visible light irradiation

Xueming Chang; Xiaolong Yao; Ning Ding; Xiufeng Yin; Qinmin Zheng; Songliu Lu; Danmeng Shuai; Yingxue Sun

doi:10.1016/j.scitotenv.2019.05.075

Photocatalytic degradation of trihalomethanes and haloacetonitriles on graphitic carbon nitride under visible light irradiation

Sci Total Environ. 2019 Sep 10:682:200-207. doi: 10.1016/j.scitotenv.2019.05.075. Epub 2019 May 7.

Authors

Xueming Chang¹, Xiaolong Yao², Ning Ding¹, Xiufeng Yin¹, Qinmin Zheng³, Songliu Lu⁴, Danmeng Shuai³, Yingxue Sun⁵

Affiliations

¹ Department of Environmental Science and Engineering, Beijing Technology and Business University, Beijing 100048, China.
² Department of Environmental Science and Engineering, Beijing Technology and Business University, Beijing 100048, China. Electronic address: yaoxiaolong@btbu.edu.cn.
³ Department of Civil and Environmental Engineering, The George Washington University, Washington, DC 20052, US.
⁴ Tus-Water Group Limited, Shanghai 200072, China.
⁵ Department of Environmental Science and Engineering, Beijing Technology and Business University, Beijing 100048, China. Electronic address: sunyx@th.btbu.edu.cn.

PMID: 31121346
DOI: 10.1016/j.scitotenv.2019.05.075

Abstract

Trihalomethanes (THMs) and haloacetonitriles (HANs), most common disinfection by-products in drinking water, pose adverse environmental impacts and potential risks to human health. There is a pressing need to develop innovative, economically feasible, and environmentally benign processes to control these persistent contaminants. In this paper, visible-light-responsive graphitic carbon nitride (g-C₃N₄) samples were synthesized to degrade the THMs and HANs and the photocatalytic degradation mechanism was explored. The results indicated that a carbon-doped g-C₃N₄ with an optimum dopant content (MCB_0.07) displayed the best photocatalytic activity for the total trihalomethanes (TTHM) and total haloacetonitriles (THAN), with the reaction rate constant of 11.6 and 10.4 (10^-3 min^-1), respectively. MCB_0.07 demonstrated a high THMs and HANs removal efficiency under visible light irradiation and could be reused. According to scavenger tests of the selected reactive species and X-ray photoelectron spectroscopy, holes play a dominant role for both THMs and HANs degradation on the MCB_0.07. The degradation of HANs by holes proceeded mainly through breakage of the CC bond in the CCN group. The THMs degradation was achieved through hydrogen abstraction or/and dehalogenation. The brominated-THMs/HANs were more photosensitive than their chlorinated analogous and were less stable than bromo-chloro-THMs/HANs. This study sheds light on the mechanism of the photocatalytic degradation of THMs and HANs under visible light irradiation by carbon-doped g-C₃N₄. Furthermore, it could provide insights for engineering applications and contaminant control in drinking water purification.

Keywords: Graphitic carbon nitride; Haloacetonitriles (HANs); Photocatalysis; Trihalomethanes (THMs); Visible light.