title: Oxidation of nanoscale zero-valent iron under sufficient and limited dissolved oxygen: Influences on aggregation behaviors.
abstract: 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.
authors.affiliation: Key Laboratory of Yangtze River Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China.
authors.forename: Danlie
authors.initials: D
authors.lastname: Jiang
authors.affiliation: 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.
authors.forename: Xialin
authors.initials: X
authors.lastname: Hu
authors.affiliation: Key Laboratory of Yangtze River Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Wang
authors.affiliation: 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. Electronic address: yindq@tongji.edu.cn.
authors.forename: Daqiang
authors.initials: D
authors.lastname: Yin
mesh_terms: D007501:Iron / Q000737:chemistry*; D060328:Magnetic Phenomena; D053768:Metal Nanoparticles / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*
chemical_list: D007501:Iron; D010100:Oxygen
keywords: Aggregation behavior; Dissolved oxygen; Extended DLVO theory; Magnetization; Nanoscale zero-valent iron