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Spatiotemporal Mineral Phase Evolution and Arsenic Retention in Microfluidic Models of Zerovalent Iron-Based Water Treatment
- Source :
- Environmental Science & Technology, 56 (19)
- Publication Year :
- 2022
- Publisher :
- American Chemical Society (ACS), 2022.
-
Abstract
- Arsenic (As) is a toxic element, and elevated levels of geogenic As in drinking water pose a threat to the health of several hundred million people worldwide. In this study, we used microfluidics in combination with optical microscopy and X-ray spectroscopy to investigate zerovalent iron (ZVI) corrosion, secondary iron (Fe) phase formation, and As retention processes at the pore scale in ZVI-based water treatment filters. Two 250 μm thick microchannels filled with single ZVI and quartz grain layers were operated intermittently (12 h flow/12 h no-flow) with synthetic groundwater (pH 7.5; 570 μg/L As(III)) over 13 and 49 days. Initially, lepidocrocite (Lp) and carbonate green rust (GRC) were the dominant secondary Fe-phases and underwent cyclic transformation. During no-flow, lepidocrocite partially transformed into GRC and small fractions of magnetite, kinetically limited by Fe(II) diffusion or by decreasing corrosion rates. When flow resumed, GRC rapidly and nearly completely transformed back into lepidocrocite. Longer filter operation combined with a prolonged no-flow period accelerated magnetite formation. Phosphate adsorption onto Fe-phases allowed for downstream calcium carbonate precipitation and, consequently, accelerated anoxic ZVI corrosion. Arsenic was retained on Fe-coated quartz grains and in zones of cyclic Lp-GRC transformation. Our results suggest that intermittent filter operation leads to denser secondary Fe-solids and thereby ensures prolonged filter performance.<br />Environmental Science & Technology, 56 (19)<br />ISSN:0013-936X<br />ISSN:1520-5851
- Subjects :
- water filter
corrosion
zerovalent iron
Drinking Water
Iron
Microfluidics
Quartz
General Chemistry
Ferric Compounds
Ferrosoferric Oxide
Arsenic
Calcium Carbonate
Phosphates
Water Purification
arsenic
microfluidics
microscopy
synchrotron X-ray spectroscopy
Humans
Environmental Chemistry
Water Pollutants, Chemical
Subjects
Details
- ISSN :
- 15205851 and 0013936X
- Volume :
- 56
- Database :
- OpenAIRE
- Journal :
- Environmental Science & Technology
- Accession number :
- edsair.doi.dedup.....7725c3964f346878c1f8fc9144f51b08