Yang Kunlun, Chi Yanxiao, Yang Yuxuan, Lou Zimo, Wang Tonghui, Wang Dengyang, Miao Hengfeng, Xu Xinhua
School of Environmental and Civil Engineering, Jiangnan University, Wuxi 214122, China; Suzhou Institute of Environmental Sciences, Postdoctoral Innovation and Practice Base of Jiangsu Province, Suzhou 21500, China.
School of Environmental and Civil Engineering, Jiangnan University, Wuxi 214122, China.
Sci Total Environ. 2024 Jan 10;907:168123. doi: 10.1016/j.scitotenv.2023.168123. Epub 2023 Oct 25.
To avoid severe aggregation and synergistically utilize the intrinsic and photocatalytic reducibility, pyrite (FeS) was loaded onto N-doped reduced graphene oxides (N-rGO) to fabricate a novel FeS/N-rGO heterojunction catalyst for enhanced chromium (Cr(VI)) reduction in oxic condition to simultaneously investigate the specific effect and role of dissolved oxygen (DO). Characterization results showed that strong interaction and combination of FeS and N-rGO not only achieved the uniform distribution of FeS, but also increased the defects, and exposed more functional groups. Meanwhile, the Type II heterojunction was formed in FeS/N-rGO, which facilitated the separation efficiency of photo-generated carriers and electrons, endowing FeS/N-rGO a superior photocatalytic activity. Cr(VI) was almost completely reduced via FeS/N-rGO within 60 min under irradiation (Cr(VI) = 10 mg/L, dosage = 0.2 g/L), 3 times that of pristine FeS (18.7 %). Trapping and Electron Spin Resonance (ESR) experiments indicated that photo-generated e and derived O species from photoactivation of dioxygen (DO) were the key reactive species for the enhancement of photo-assisted Cr(VI) reduction, rather than reductive Fe and S species. Although the photocatalysis of FeS/N-rGO cannot directly generate hydroxyl radicals (OH), the oxidative OH ascribed to superoxide radicals (O), photo-induced holes and free DO preferentially consumed by Fe and S with stronger reducibility. Hence, as compared to the anoxic condition, the reduction rate of Cr(VI) was slightly decreased, but still could be totally removed within 60 min in the oxic conditions. Due to the excessive amount of FeS/N-rGO, Cr(III) after reduction would not be influenced by oxidative species and maintain stability under oxic condition. This study provided a facile modification strategy for FeS based composites and uncovered its working mechanism for Cr(VI) decontamination.
为避免严重团聚并协同利用本征和光催化还原能力，将黄铁矿（FeS）负载到氮掺杂还原氧化石墨烯（N-rGO）上，制备了一种新型的FeS/N-rGO异质结催化剂，用于在有氧条件下增强铬（Cr(VI)）的还原，同时研究溶解氧（DO）的具体作用。表征结果表明，FeS与N-rGO之间的强相互作用和结合不仅实现了FeS的均匀分布，还增加了缺陷并暴露出更多官能团。同时，FeS/N-rGO中形成了II型异质结，这促进了光生载流子和电子的分离效率，赋予FeS/N-rGO优异的光催化活性。在光照下（Cr(VI)=10mg/L，用量=0.2g/L），FeS/N-rGO在60分钟内几乎完全将Cr(VI)还原，是原始FeS（18.7%）的3倍。捕获和电子自旋共振（ESR）实验表明，光生电子和由溶解氧（DO）光活化衍生的氧物种是增强光辅助Cr(VI)还原的关键活性物种，而不是还原性的Fe和S物种。虽然FeS/N-rGO的光催化不能直接产生羟基自由基（OH），但归因于超氧自由基（O）、光生空穴和溶解氧（DO）的氧化型OH优先被还原性更强的Fe和S消耗。因此，与缺氧条件相比，Cr(VI)的还原速率略有下降，但在有氧条件下仍能在60分钟内完全去除。由于FeS/N-rGO过量，还原后的Cr(III)在有氧条件下不会受到氧化物种的影响并保持稳定。本研究为基于FeS的复合材料提供了一种简便的改性策略，并揭示了其Cr(VI)去污的工作机制。
