TY - JOUR
T1 - Characteristics of Fe and Mn bearing precipitates generated by Fe(II) and Mn(II) co-oxidation with O2, MnO4 and HOCl in the presence of groundwater ions
AU - Ahmad, Arslan
AU - van der Wal, Albert
AU - Bhattacharya, Prosun
AU - van Genuchten, Case M.
N1 - Funding Information:
This research is co-financed with PPS-funding from the Topconsortia for Knowledge & Innovation (TKI’s) of the Ministry of Economic Affairs and Climate. AA acknowledges support from Evides Waterbedrijf . CMvG acknowledges funding from a NWO Veni grant. The authors want to thank Luuk de Waal of KWR, Simon Mueller of Evides and Martijn Eikelboom of Wageningen University for their support during the experiments. We thank Ryan Davis at SSRL and Dipanjan Banerjee at ESRF for assistance during XAS data collection. Use of SSRL, SLAC National Accelerator Laboratory, was supported by the U.S. Department of Energy , Office of Science, Basic Energy Sciences, under Contract No. DE-AC02-76SF00515 .
Funding Information:
This research is co-financed with PPS-funding from the Topconsortia for Knowledge & Innovation (TKI's) of the Ministry of Economic Affairs and Climate. AA acknowledges support from Evides Waterbedrijf. CMvG acknowledges funding from a NWO Veni grant. The authors want to thank Luuk de Waal of KWR, Simon Mueller of Evides and Martijn Eikelboom of Wageningen University for their support during the experiments. We thank Ryan Davis at SSRL and Dipanjan Banerjee at ESRF for assistance during XAS data collection. Use of SSRL, SLAC National Accelerator Laboratory, was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Contract No. DE-AC02-76SF00515.
Publisher Copyright:
© 2019 The Authors
PY - 2019/9/15
Y1 - 2019/9/15
N2 - In this work, we combined macroscopic measurements of precipitate aggregation and chemical composition (Mn/Fe solids ratio) with Fe and Mn K-edge X-ray absorption spectroscopy to investigate the solids formed by co-oxidation of Fe(II) and Mn(II) with O2, MnO4, and HOCl in the presence of groundwater ions. In the absence of the strongly sorbing oxyanions, phosphate (P) and silicate (Si), and calcium (Ca), O2 and HOCl produced suspensions that aggregated rapidly, whereas co-oxidation of Fe(II) and Mn(II) by MnO4 generated colloidally stable suspensions. The aggregation of all suspensions decreased in P and Si solutions, but Ca counteracted these oxyanion effects. The speciation of oxidized Fe and Mn in the absence of P and Si also depended on the oxidant, with O2 producing Mn(III)-incorporated lepidocrocite (Mn/Fe = 0.01–0.02 mol/mol), HOCl producing Mn(III)-incorporated hydrous ferric oxide (HFO) (Mn/Fe = 0.08 mol/mol), and MnO4 producing poorly-ordered MnO2 and HFO (Mn/Fe > 0.5 mol/mol). In general, the presence of P and Si decreased the crystallinity of the Fe(III) phase and increased the Mn/Fe solids ratio, which was found by Mn K-edge XAS analysis to be due to an increase in surface-bound Mn(II). By contrast, Ca decreased the Mn/Fe solids ratio and decreased the fraction of Mn(II) associated with the solids, suggesting that Ca and Mn(II) compete for sorption sites. Based on these results, we discuss strategies to optimize the design (i.e. filter bed operation and chemical dosing) of water treatment plants that aim to remove Fe(II) and Mn(II) by co-oxidation.
AB - In this work, we combined macroscopic measurements of precipitate aggregation and chemical composition (Mn/Fe solids ratio) with Fe and Mn K-edge X-ray absorption spectroscopy to investigate the solids formed by co-oxidation of Fe(II) and Mn(II) with O2, MnO4, and HOCl in the presence of groundwater ions. In the absence of the strongly sorbing oxyanions, phosphate (P) and silicate (Si), and calcium (Ca), O2 and HOCl produced suspensions that aggregated rapidly, whereas co-oxidation of Fe(II) and Mn(II) by MnO4 generated colloidally stable suspensions. The aggregation of all suspensions decreased in P and Si solutions, but Ca counteracted these oxyanion effects. The speciation of oxidized Fe and Mn in the absence of P and Si also depended on the oxidant, with O2 producing Mn(III)-incorporated lepidocrocite (Mn/Fe = 0.01–0.02 mol/mol), HOCl producing Mn(III)-incorporated hydrous ferric oxide (HFO) (Mn/Fe = 0.08 mol/mol), and MnO4 producing poorly-ordered MnO2 and HFO (Mn/Fe > 0.5 mol/mol). In general, the presence of P and Si decreased the crystallinity of the Fe(III) phase and increased the Mn/Fe solids ratio, which was found by Mn K-edge XAS analysis to be due to an increase in surface-bound Mn(II). By contrast, Ca decreased the Mn/Fe solids ratio and decreased the fraction of Mn(II) associated with the solids, suggesting that Ca and Mn(II) compete for sorption sites. Based on these results, we discuss strategies to optimize the design (i.e. filter bed operation and chemical dosing) of water treatment plants that aim to remove Fe(II) and Mn(II) by co-oxidation.
KW - Drinking water
KW - Filtration
KW - Groundwater treatment
KW - Iron and manganese oxidation and precipitation
KW - Mn and Fe removal
KW - X-ray absorption spectroscopy
UR - http://www.scopus.com/inward/record.url?scp=85067487534&partnerID=8YFLogxK
U2 - 10.1016/j.watres.2019.06.036
DO - 10.1016/j.watres.2019.06.036
M3 - Article
C2 - 31229731
AN - SCOPUS:85067487534
SN - 0043-1354
VL - 161
SP - 505
EP - 516
JO - Water Research
JF - Water Research
ER -