Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR 000, China; National Engineering Laboratory for Clean Technology of Leather Manufacture, Sichuan University, Chengdu 610065, China.
Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR 000, China; School of Environmental and Chemical Engineering, Foshan University, Foshan 528000, China.
Water Res. 2023 May 15;235:119889. doi: 10.1016/j.watres.2023.119889. Epub 2023 Mar 20.
The photolysis of monochloramine (NHCl), a widely used disinfectant, under UVC irradiation produces different radicals for the micropollutant degradation. For the first time, this study demonstrates the degradation of bisphenol A (BPA) via the NHCl activation by graphitic carbon nitride (g-CN) photocatalysis using visible light-LEDs at 420 nm, termed as the Vis/g-CN/NHCl process. The process produces •NH, •NHOO, •NO and •NO via the e- and O-induced activation pathways and •NHCl and NHClOO• via the h-induced activation pathway. The produced reactive nitrogen species (RNS) enhanced 100% of the BPA degradation compared with the Vis/g-CN. Density functional theory calculations confirmed the proposed NHCl activation pathways and further demonstrated that e/O and h induced the cleavage of N-Cl and N-H bonds in NHCl, respectively. The process converted 73.5% of the decomposed NHCl to nitrogen-containing gas, compared with that of approximately 20% in the UVC/NHCl process, leaving much less ammonia, nitrite and nitrate in water. Among different operating conditions and water matrices tested, of particular significance is natural organic matter of 5 mgDOC/L only reduced 13.1% of the BPA degradation compared against that of at least 46% reduction in the UVC/NHCl process. Only 0.017-0.161 µg/L of disinfection byproducts were produced, two orders of magnitudes lower than that in the UVC/chlorine and UVC/NHCl processes. The combined use of visible light-LEDs, g-CN and NHCl significantly improves the micropollutant degradation and reduces the energy consumption and byproduct formation of the NHCl-based AOP.
次氯胺 (NHCl) 的光解作用，作为一种广泛使用的消毒剂，在 UVC 辐射下会产生不同的自由基，从而促进微量污染物的降解。本研究首次采用可见光 LED 照射石墨相氮化碳 (g-CN) 催化剂，通过 NHCl 活化作用，在 420nm 下实现了双酚 A (BPA) 的降解，该过程被称为 Vis/g-CN/NHCl 工艺。该过程通过电子和 O 诱导的活化途径生成 •NH、•NHOO、•NO 和 •NO，并通过 h 诱导的活化途径生成 •NHCl 和 NHClOO•。所产生的活性氮物种 (RNS) 使 BPA 的降解率提高了 100%，相比于单独的 Vis/g-CN 过程。密度泛函理论计算证实了所提出的 NHCl 活化途径，并进一步表明电子/O 和 h 分别诱导 NHCl 中 N-Cl 和 N-H 键的断裂。该过程将 73.5%的分解 NHCl 转化为含氮气体，而在 UVC/NHCl 过程中，这一比例约为 20%，水中剩余的氨、亚硝酸盐和硝酸盐更少。在测试的不同操作条件和水基质中，特别重要的是 5mgDOC/L 的天然有机物仅使 BPA 的降解率降低了 13.1%，而在 UVC/NHCl 过程中，这一比例至少降低了 46%。仅产生了 0.017-0.161µg/L 的消毒副产物，比 UVC/氯气和 UVC/NHCl 过程低两个数量级。可见光 LED、g-CN 和 NHCl 的联合使用显著提高了微量污染物的降解效率，同时降低了基于 NHCl 的 AOP 的能耗和副产物生成。
