title: Production and transformation of mixed-valent nanoparticles generated by Fe(0) electrocoagulation.
abstract: Mixed-valent iron nanoparticles (NP) generated electrochemically by Fe(0) electrocoagulation (EC) show promise for on-demand industrial and drinking water treatment in engineered systems. This work applies multiple characterization techniques (in situ Raman spectroscopy, XRD, SEM, and cryo-TEM) to investigate the formation and persistence of magnetite and green rust (GR) NP phases produced via the Fe(0) EC process. Current density and background electrolyte composition were examined in a controlled anaerobic system to determine the initial Fe phases generated as well as transformation products with aging. Fe phases were characterized in an aerobic EC system with both simple model electrolytes and real groundwater to investigate the formation and aging of Fe phases produced in a system representing treatment of arsenic-contaminated ground waters in South Asia. Two central pathways for magnetite production via Fe(0) EC were identified: (i) as a primary product (formation within seconds when DO absent, no intermediates detected) and (ii) as a transformation product of GR (from minutes to days depending on pH, electrolyte composition, and aging conditions). This study provides a better understanding of the formation conditions of magnetite, GR, and ferric (oxyhydr)oxides in Fe EC, which is essential for process optimization for varying source waters.
authors.affiliation: Department of Chemical and Biological Engineering, University of British Columbia , Vancouver, British Columbia V6T 1Z3, Canada.
authors.forename: Kristian L
authors.initials: KL
authors.lastname: Dubrawski
authors.forename: Case M
authors.initials: CM
authors.lastname: van Genuchten
authors.forename: Caroline
authors.initials: C
authors.lastname: Delaire
authors.forename: Susan E
authors.initials: SE
authors.lastname: Amrose
authors.forename: Ashok J
authors.initials: AJ
authors.lastname: Gadgil
authors.forename: Madjid
authors.initials: M
authors.lastname: Mohseni
mesh_terms: D001151:Arsenic / Q000032:analysis; D001208:Asia; D020285:Cryoelectron Microscopy; D060766:Drinking Water / Q000737:chemistry*; D055664:Electrochemical Techniques; D052203:Ferrosoferric Oxide / Q000737:chemistry; D060587:Groundwater / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D058085:Iron Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D013059:Spectrum Analysis, Raman; D014874:Water Pollutants, Chemical / Q000032:analysis*; D018508:Water Purification / Q000379:methods*; D014961:X-Ray Diffraction
chemical_list: D060766:Drinking Water; D058085:Iron Compounds; D014874:Water Pollutants, Chemical; D007501:Iron; D001151:Arsenic; D052203:Ferrosoferric Oxide