School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, China.
School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, China.
Sci Total Environ. 2022 Jan 20;805:150326. doi: 10.1016/j.scitotenv.2021.150326. Epub 2021 Sep 14.
This study investigated the degradation of perfluorooctanoic acid (PFOA) on zerovalent iron-laden biochar (BC-ZVI) prepared by carbothermal reduction. Results show that over 99% PFOA can be removed by BC-ZVI in hydrothermal conditions under 240 °C within 6 h. The maximum defluorination rate of 63.2% was achieved after 192 h, and this outcome was significantly better than biochar (BC) and zero-valent iron (ZVI) alone. The short-chain perfluorinated compounds (PFCs) and perfluoroheptanal were detected in the liquid phase after degradation, suggesting that the degradation of PFOAs by BC-ZVI followed the Kobel decarboxylation process. XRD and SEM-EDS analyses strongly suggested that carbothermal reduction could avoid the agglomeration of ZVI loaded onto biochar, which helped make the PFOA degradation more efficient. The frontier molecular orbital theory calculated by density functional theory revealed there were two possibilities for ZVI loading on BC (edged or internal loading), while the edge loaded ZVI had a greater tendency to provide electrons for the defluorination of PFOA than internally loaded ZVI.
本研究考察了零价铁负载生物炭（BC-ZVI）在水热条件下对全氟辛酸（PFOA）的降解。结果表明，在 240°C 下，6 h 内超过 99%的 PFOA 可以被 BC-ZVI 去除。192 h 后，最大脱氟率达到 63.2%，这一结果明显优于单独的生物炭（BC）和零价铁（ZVI）。降解后在液相中检测到短链全氟化合物（PFCs）和全氟庚醛，表明 BC-ZVI 降解 PFOA 遵循 Kobel 脱羧过程。XRD 和 SEM-EDS 分析强烈表明，碳热还原可以避免负载在生物炭上的 ZVI 的团聚，这有助于提高 PFOA 的降解效率。密度泛函理论计算的前沿分子轨道理论表明，ZVI 有两种负载在 BC 上的可能性（边缘或内部负载），而边缘负载的 ZVI 比内部负载的 ZVI 更有倾向为 PFOA 的脱氟提供电子。
