TY - JOUR
T1 - Controls on the formation of Fe(II,III) (hydr)oxides by Fe(0) electrolysis
AU - van Genuchten, C.M.
AU - Behrends, T.
AU - Kraal, P.
AU - Stipp, S. L.S.
AU - Dideriksen, K.
N1 - Funding Information:
Funding provided by a NWO Veni Grant (Project No. 14400 ) awarded to CMvG for the planning and execution of experiments, data analysis and article preparation is acknowledged. PK acknowledges funding provided a NWO Veni Grant ( 863.14.014 ). KD is grateful for support from the NanoGeoScience Group. We thank Marcel Ceccato, Marco Mangayayam and Henning Osholm Sørensen at the University of Copenhagen and Simon Mueller at Utrecht University for technical support or advice along the various stages of this work. We acknowledge the European Synchrotron Radiation Facility for provision of synchrotron radiation facilities and we thank Dipanjan Banerjee for assistance in using the Dutch-Belgium beamline ( BM-26A ), which receives funding from the Dutch (NWO) and Flemish (FWO) Science Foundations.
Publisher Copyright:
© 2018 Elsevier Ltd
PY - 2018/10/1
Y1 - 2018/10/1
N2 - This study identifies the electrochemical and solution chemical controls on the production of Fe(II,III) (hydr)oxides formed by the electrolysis of Fe(0) metal, also knows as Fe(0) electrocoagulation. EXAFS spectroscopy and X-ray diffraction were used to characterize the solids produced as a function of: i) applied current, which corresponded to iron(II) production rates of 30–300 μM min−1, ii) pH and iii) background electrolyte. Two systems were investigated where: i) the dissolved oxygen (O2) concentration was maintained at 0.1, 0.3 and 3.0 mg L−1 and ii) the O2 drifted in response to varied Fe(II) addition rates. A narrow range of O2 separated the domains for Fe(II,III) and Fe(III) (hydr)oxide formation. At O2 ≥ 0.3 mg L−1, Fe(III) solids dominated, while Fe(II,III) (hydr)oxides were the principal phases at O2 = 0.1 mg L−1. The highest fraction of Fe(II,III) (hydr)oxides formed in the O2 drift experiments at the highest Fe(II) production rate, i.e. 300 μM min−1. The background electrolyte determined the type of Fe(II,III) (hydr)oxide that formed: NaCl solutions favored magnetite and NaHCO3 solutions favored carbonate green rust. Our results are consistent with an Fe(II,III) (hydr)oxide formation pathway where Fe(II) addition after O2 depletion leads to rapid (<10 min) transformation of precursory Fe(III) precipitates.
AB - This study identifies the electrochemical and solution chemical controls on the production of Fe(II,III) (hydr)oxides formed by the electrolysis of Fe(0) metal, also knows as Fe(0) electrocoagulation. EXAFS spectroscopy and X-ray diffraction were used to characterize the solids produced as a function of: i) applied current, which corresponded to iron(II) production rates of 30–300 μM min−1, ii) pH and iii) background electrolyte. Two systems were investigated where: i) the dissolved oxygen (O2) concentration was maintained at 0.1, 0.3 and 3.0 mg L−1 and ii) the O2 drifted in response to varied Fe(II) addition rates. A narrow range of O2 separated the domains for Fe(II,III) and Fe(III) (hydr)oxide formation. At O2 ≥ 0.3 mg L−1, Fe(III) solids dominated, while Fe(II,III) (hydr)oxides were the principal phases at O2 = 0.1 mg L−1. The highest fraction of Fe(II,III) (hydr)oxides formed in the O2 drift experiments at the highest Fe(II) production rate, i.e. 300 μM min−1. The background electrolyte determined the type of Fe(II,III) (hydr)oxide that formed: NaCl solutions favored magnetite and NaHCO3 solutions favored carbonate green rust. Our results are consistent with an Fe(II,III) (hydr)oxide formation pathway where Fe(II) addition after O2 depletion leads to rapid (<10 min) transformation of precursory Fe(III) precipitates.
KW - EXAFS spectroscopy
KW - Fe(0) electrocoagulation
KW - Green rust
KW - Magnetite
KW - Mineral formation
UR - http://www.scopus.com/inward/record.url?scp=85051764199&partnerID=8YFLogxK
U2 - 10.1016/j.electacta.2018.08.031
DO - 10.1016/j.electacta.2018.08.031
M3 - Article
AN - SCOPUS:85051764199
VL - 286
SP - 324
EP - 338
JO - Electrochimica Acta
JF - Electrochimica Acta
SN - 0013-4686
ER -