State Key Laboratory of Nuclear Resources and Environment, East China University of Technology, No. 418, Guanglan Avenue, Nanchang 330013, PR China; School of Nuclear Science and Engineering, East China University of Technology, No. 418, Guanglan Avenue, Nanchang 330013, PR China.
Anhui Nuclear Exploration Technology Central Institute, No. 8, Zhanghe Road, Wuhu 241000, PR China; School of Nuclear Science and Engineering, East China University of Technology, No. 418, Guanglan Avenue, Nanchang 330013, PR China.
Environ Pollut. 2020 May;260:114070. doi: 10.1016/j.envpol.2020.114070. Epub 2020 Jan 25.
Photocatalysis is a promising method to eliminate hexavalent uranium (U(Ⅵ)) and recycle it from wastewater. However, most of researched photocatalysts are metal-contained, inactive in visible light, and inconvenient to recycle, which unfortunately impedes the further utilization of photocatalytic technology in U(Ⅵ) pollution treatment. Herein, g-CN isotype heterojunction with interpenetrated tri-s-triazine structure (ipCN) was prepared by inserting urea into the interlayer of tri-s-triazine planes of thiourea-derived g-CN and in-site thermal treating. The synthesized nanocomposites were used to convert soluble U(Ⅵ) ions into U(Ⅳ) sediment under visible light. Experimental and characterization results reveal that ipCN possess larger BET surface area, more negative-charged surface, higher U(Ⅵ) adsorption capability, and more efficient mass diffusion and charges transfer properties. With these excellent characteristics, nearly 98% U(Ⅵ) could be removed within 20 min over ipCN and 92% photoreduction efficiency could also be kept after 7 cycle uses, which were equal to or even superior than most reported metal-based photocatalysts. It is also proven that the configuration of U(Ⅵ) and photogenerated ·O play a significant role in the photocatalytic U(Ⅵ) reduction process, with (UO)(OH) are more prone to be adsorbed and the photoinduced process of ·O will steal electrons from photocatalysts. Furthermore, with the self-generated ·O and HO, a green and facile regeneration process of photocatalysts was proposed This work provides a promising scheme to extract U(Ⅵ) from the perspectives of photocatalysts exploitation, photocatalytic reduction, and photocatalysts regeneration, which is meaningful for the sustainable U(Ⅵ) resource recovery and U(Ⅵ) pollution purification.
光催化是一种很有前途的方法，可以消除六价铀 (U(VI)) 并从废水中回收它。然而，大多数研究的光催化剂都含有金属，对可见光不活跃，且不方便回收，这不幸地阻碍了光催化技术在 U(VI) 污染处理中的进一步应用。在此，通过将尿素插入硫脲衍生的 g-CN 的三嗪平面层间，原位热处理制备了具有互穿三嗪结构的 g-CN 同型异质结 (ipCN)。所合成的纳米复合材料被用于在可见光下将可溶性 U(VI) 离子转化为 U(IV) 沉淀物。实验和表征结果表明，ipCN 具有更大的 BET 表面积、更多的负电荷表面、更高的 U(VI) 吸附能力，以及更高效率的质量扩散和电荷转移特性。具有这些优异的特性，ipCN 在 20 分钟内几乎可以去除 98%的 U(VI)，并且在 7 次循环使用后仍保持 92%的光还原效率，这与大多数报道的金属基光催化剂相当或更优。还证明了 U(VI) 的构型和光生·O 在光催化 U(VI) 还原过程中起着重要作用，(UO)(OH) 更容易被吸附，而光诱导的·O 过程将从光催化剂中窃取电子。此外，通过自生的·O 和 HO，提出了一种绿色且简便的光催化剂再生过程。这项工作为从光催化剂开发、光催化还原和光催化剂再生的角度提取 U(VI) 提供了一种很有前途的方案，这对于可持续的 U(VI) 资源回收和 U(VI) 污染净化具有重要意义。
