title: Effects of nitrate on the treatment of lead contaminated groundwater by nanoscale zerovalent iron.
abstract: Nanoscale zerovalent iron (nZVI) is efficient for removing Pb(2+) and nitrate from water. However, the influence of nitrate, a common groundwater anion, on Pb(2+) removal by nZVI is not well understood. In this study, we showed that under excess Fe(0) conditions (molar ratio of Fe(0)/nitrate>4), Pb(2+) ions were immobilized more quickly (<5 min) than in nitrate-free systems (∼ 15 min) due to increasing pH. With nitrate in excess (molar ratio of Fe(0)/nitrate<4), nitrate stimulated the formation of crystal PbxFe3-xO4 (ferrite), which provided additional Pb(2+) removal. However, ∼ 7% of immobilized Pb(2+) ions were released into aqueous phase within 2h due to ferrite deformation. Oxidation-reduction potential (ORP) values below -600 mV correlated with excess Fe(0) conditions (complete Pb(2+) immobilization), while ORP values ≥-475 mV characterized excess nitrate conditions (ferrite process and Pb(2+) release occurrence). This study indicates that ORP monitoring is important for proper management of nZVI-based remediation in the subsurface to avoid lead remobilization in the presence of nitrate.
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai 200092, China; Bren School of Environmental Science & Management, University of California, Santa Barbara, 3420 Bren Hall, CA 93106, USA; University of California Center for Environmental Implications of Nanotechnology, Santa Barbara, CA, USA.
authors.forename: Yiming
authors.initials: Y
authors.lastname: Su
authors.affiliation: Bren School of Environmental Science & Management, University of California, Santa Barbara, 3420 Bren Hall, CA 93106, USA; University of California Center for Environmental Implications of Nanotechnology, Santa Barbara, CA, USA.
authors.forename: Adeyemi S
authors.initials: AS
authors.lastname: Adeleye
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai 200092, China.
authors.forename: Xuefei
authors.initials: X
authors.lastname: Zhou
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai 200092, China; College of Civil Engineering, Tongji University, Shanghai 200092, China.
authors.forename: Chaomeng
authors.initials: C
authors.lastname: Dai
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai 200092, China.
authors.forename: Weixian
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Bren School of Environmental Science & Management, University of California, Santa Barbara, 3420 Bren Hall, CA 93106, USA; University of California Center for Environmental Implications of Nanotechnology, Santa Barbara, CA, USA. Electronic address: keller@bren.ucsb.edu.
authors.forename: Arturo A
authors.initials: AA
authors.lastname: Keller
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai 200092, China. Electronic address: zhangyalei@tongji.edu.cn.
authors.forename: Yalei
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D060587:Groundwater / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D007854:Lead / Q000302:isolation & purification*; D009566:Nitrates / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*
chemical_list: D009566:Nitrates; D014874:Water Pollutants, Chemical; D007854:Lead; D007501:Iron
keywords: Ferrite process; Lead pollution; Nanoscale zerovalent iron; Nitrate influence; Oxidation–reduction potential