title: Simultaneous removal of cadmium and nitrate in aqueous media by nanoscale zerovalent iron (nZVI) and Au doped nZVI particles.
abstract: Nanoscale zerovalent iron (nZVI) has demonstrated high efficacy for treating nitrate or cadmium (Cd) contamination, but its efficiency for simultaneous removal of nitrate and Cd has not been investigated. This study evaluated the reactivity of nZVI to the co-contaminants and by-product formation, employed different catalysts to reduce nitrite yield from nitrate, and examined the transformation of nZVI after reaction. Nitrate reduction resulted in high solution pH, negatively charged surface of nZVI, formation of Fe3O4 (a stable transformation of nZVI), and no release of ionic iron. Increased pH and negative charge contributed to significant increase in Cd(II) removal capacity (from 40 mg/g to 188 mg/g) with nitrate present. In addition, nitrate reduction by nZVI could be catalyzed by Cd(II): while 30% of nitrate was reduced by nZVI within 2 h in the absence of Cd(II), complete nitrate reduction was observed in the presence of 40 mg-Cd/L due to the formation of Cd islands (Cd(0) and CdO) on the nZVI particles. While nitrate was reduced mostly to ammonium when Cd(II) was not present or at Cd(II) concentrations ≥ 40 mg/L, up to 20% of the initial nitrate was reduced to nitrite at Cd(II) concentrations < 40 mg/L. Among nZVI particles doped with 1 wt. % Cu, Ag, or Au, nZVI deposited with 1 wt. % Au reduced nitrite yield to less than 3% of the initial nitrate, while maintaining a high Cd(II) removal capacity.
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: Bren School of Environmental Science & Management, University of California, Santa Barbara, 3420 Bren Hall, CA 93106, USA.
authors.forename: Yuxiong
authors.initials: Y
authors.lastname: Huang
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai 200092, China.
authors.forename: Xiaoya
authors.initials: X
authors.lastname: Sun
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: Xuefei
authors.initials: X
authors.lastname: Zhou
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai 200092, China; Key Laboratory of Yangtze Water Environment for Ministry of Education, Tongji University, Shanghai 200092, China. Electronic address: zhangyalei@tongji.edu.cn.
authors.forename: Yalei
authors.initials: Y
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
mesh_terms: D002104:Cadmium / Q000737:chemistry*; D003300:Copper / Q000737:chemistry; D006046:Gold / Q000737:chemistry; D007501:Iron / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D009566:Nitrates / Q000737:chemistry*; D009573:Nitrites / Q000032:analysis; D012834:Silver / Q000737:chemistry; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D009566:Nitrates; D009573:Nitrites; D014874:Water Pollutants, Chemical; D002104:Cadmium; D012834:Silver; D006046:Gold; D003300:Copper; D007501:Iron
keywords: Bimetallic nanoparticles; Cd removal; Nanoscale zerovalent iron; Nitrate reduction