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

WATER RESEARCH

卷:161

Article

Ahmad, Arslan^1,2,3,4  van der Wal, Albert^3,4  Bhattacharya, Prosun^2,5  van Genuchten, Case M.^6,7 

[1] KWR Water Cycle Res Inst, Nieuwegein, Netherlands

[2] KTH Royal Inst Technol, Dept Sustainable Dev Environm Sci & Engn, KTH Int Groundwater Arsen Res Grp, Stockholm, Sweden

[3] WUR, Dept Environm Technol, Wageningen, Netherlands

[4] Evides Water Co NV, Rotterdam, Netherlands

[5] Univ Southern Queensland, Int Ctr Appl Climate Sci, Toowoomba, Qld, Australia

[6] Geol Survey Denmark & Greenland GEUS, Geochem Dept, Copenhagen, Denmark

[7] Univ Utrecht, Fac Geosci, Dept Earth Sci Geochem, Utrecht, Netherlands

关键词: Mn and Fe removal;    Drinking water;    Filtration;    Iron and manganese oxidation and precipitation;    Groundwater treatment;    X-ray absorption spectroscopy;   

DOI  :  10.1016/j.watres.2019.06.036

来源: Elsevier

【 摘 要 】

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 O-2, 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), O-2 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 O-2 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. (C) 2019 The Authors. Published by Elsevier Ltd.

【 授权许可】

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