State Key Laboratory for Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai, 200092, China.
State Key Laboratory for Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai, 200092, China.
Chemosphere. 2021 Jan;263:127875. doi: 10.1016/j.chemosphere.2020.127875. Epub 2020 Aug 3.
Nanoscale zero-valent iron (nZVI) settled slowly and incompletely in a nano-iron reactor (NIR) in wastewater treatment, and the effluent quality and processing capacity of nZVI were degenerated. Herein, three types of polyacrylamide (PAM), anionic-APAM (nZVI), cationic-CPAM (nZVI), and nonionic-NPAM (nZVI)) were applied to modify the nZVI (nZVI), which were proved to enhance aggregation and sedimentation in the gravity settling clarifier of NIR. PAM modification lead to aggregate by forming large agglomerates. The median sizes of aggregates were 32, 194, 168 and 133 μm respectively for nZVI, nZVI, nZVI, and nZVI. Under quiescent conditions, bare nZVI needed 5 min to reach sedimentation equilibrium, while nZVI just within 1 min nZVI settled more quickly and completely than nZVI and nZVI. The Fe concentration in the dynamic flow NIR effluent could keep a low level for 8 h for nZVI, while bare nZVI for 6 h. Iron concentration was 3.11, 0.037, 0.93, and 1.20 mg·L for nZVI, nZVI, nZVI, and nZVI after 8-h-reaction. Meanwhile, the reactivity of nZVI was kept much longer for lead removal in the NIR. Results demonstrated PAM modifications (especially CPAM) provided a reliable solution for nZVI aggregation and sedimentation in wastewater treatment.
纳米零价铁（nZVI）在废水处理中的纳米铁反应器（NIR）中缓慢且不完全沉降，导致 nZVI 的出水质量和处理能力下降。在此，三种类型的聚丙烯酰胺（PAM），阴离子-APAM（nZVI），阳离子-CPAM（nZVI）和非离子-NPAM（nZVI）被应用于修饰 nZVI（nZVI），证明了它们能够增强 NIR 重力沉降澄清器中的聚集和沉降。PAM 修饰导致通过形成大团聚体来聚集。聚集体的中值粒径分别为 32、194、168 和 133μm，对于 nZVI、nZVI、nZVI 和 nZVI。在静止条件下，裸露的 nZVI 需要 5 分钟才能达到沉降平衡，而 nZVI 只需 1 分钟，nZVI 的沉降速度比 nZVI 和 nZVI 更快、更完全。在动态流动 NIR 流出物中，nZVI 的铁浓度可以在 8 小时内保持在低水平，而裸露的 nZVI 则为 6 小时。反应 8 小时后，nZVI、nZVI、nZVI 和 nZVI 的铁浓度分别为 3.11、0.037、0.93 和 1.20mg·L。同时，nZVI 的反应性在 NIR 中去除铅的过程中保持了更长的时间。结果表明，PAM 修饰（特别是 CPAM）为 nZVI 在废水处理中的聚集和沉降提供了可靠的解决方案。
