Jiang Danlie, Hu Xialin, Wang Rui, Yin Daqiang
Key Laboratory of Yangtze River Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China.
Key Laboratory of Yangtze River Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China; State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China.
Chemosphere. 2015 Mar;122:8-13. doi: 10.1016/j.chemosphere.2014.09.095. Epub 2014 Nov 28.
Oxidations of nanoscale zero-valent iron (nZVI) under aerobic (dissolved oxygen≈8mgL(-1)) and anaerobic (dissolved oxygen <3mgL(-1)) conditions were simulated, and their influences on aggregation behaviors of nZVI were investigated. The two oxidation products were noted as HO-nZVI (nZVI oxidized in highly oxygenated water) and LO-nZVI (nZVI oxidized in lowly oxygenated water) respectively. The metallic iron of the oxidized nZVI was almost exhausted (Fe(0)≈8±5%), thus magnetization mainly depended on magnetite content. Since sufficient dissolved oxygen led to the much less magnetite (∼15%) in HO-nZVI than that in LO-nZVI (>90%), HO-nZVI was far less magnetic (Ms=88kAm(-1)) than LO-nZVI (Ms=365kAm(-1)). Consequently, HO-nZVI formed small agglomerates (228±10nm), while LO-nZVI tended to form chain-like aggregations (>1μm) which precipitated rapidly. Based on the EDLVO theory, we suggested that dissolved oxygen level determined aggregation morphologies by controlling the degree of oxidation and the magnitude of magnetization. Then the chain-like alignment of LO-nZVI would promote further aggregation, but the agglomerate morphology of HO-nZVI would eliminate magnetic forces and inhibit the aggregation while HO-nZVI remained magnetic. Our results indicated the fine colloidal stability of HO-nZVI, which might lead to the great mobility in the environment.
模拟了纳米级零价铁（nZVI）在好氧（溶解氧≈8mgL⁻¹）和厌氧（溶解氧<3mgL⁻¹）条件下的氧化过程，并研究了其对nZVI聚集行为的影响。两种氧化产物分别记为HO-nZVI（在高氧水中氧化的nZVI）和LO-nZVI（在低氧水中氧化的nZVI）。氧化后的nZVI中的金属铁几乎耗尽（Fe(0)≈8±5%），因此磁化主要取决于磁铁矿含量。由于充足的溶解氧导致HO-nZVI中的磁铁矿（约15%）比LO-nZVI中的磁铁矿（>90%）少得多，HO-nZVI的磁性（Ms=88kAm⁻¹）远低于LO-nZVI（Ms=365kAm⁻¹）。因此，HO-nZVI形成小团聚体（228±10nm），而LO-nZVI倾向于形成链状聚集体（>1μm）并迅速沉淀。基于EDLVO理论，我们认为溶解氧水平通过控制氧化程度和磁化强度来决定聚集形态。然后，LO-nZVI的链状排列会促进进一步聚集，但HO-nZVI的团聚形态会消除磁力并抑制聚集，同时HO-nZVI仍具有磁性。我们的结果表明HO-nZVI具有良好的胶体稳定性，这可能导致其在环境中具有很大的迁移性。
