title: Sorption and coprecipitation of copper to ferrihydrite and humic acid organomineral complexes and controls on copper availability.
abstract: Coprecipitation of Fe oxide and organic matter in redox dynamic sediments controls the net retention and form of Cu in the solid precipitates. In this study, coprecipitation and sorption of Cu with organomineral precipitation solids formed at different Fe:organic carbon (OC) ratios were compared for net Cu removal and extractability. As more humic acid was present during precipitation of Fe, TEM images indicated smaller Fe oxide particles formed within an organic matrix as expected. In coprecipitation reactions, as the ratio of Fe:OC decreased, more Cu was removed from solution at pH 5.5 and below. However, in sorption reactions, there was an inhibition of Cu removal at low OC concentrations. As the pH increased from 5.5 to 7 and as solution phase OC concentration increased, more Cu remained dissolved in both coprecipitation and sorption reactions. The addition of Ca(2+), glycine, histidine and citric acid or lowering the pH resulted in more extractable Cu from the coprecipitation compared with the sorption reactions. The variations in Cu extraction were likely due to a combination of a more amorphous structure in CPT products, and the relative abundance of available Fe oxide or OC binding sites. This has implications for the assumption of additivity in binding phases and for researchers conducting binding or exposure experiments.
authors.affiliation: Department of Civil and Environmental Engineering, University of Connecticut, Storrs, CT 06269, USA. Electronic address: neila.seda@uconn.edu.
authors.forename: Neila N
authors.initials: NN
authors.lastname: Seda
authors.affiliation: Department of Civil and Environmental Engineering, University of Connecticut, Storrs, CT 06269, USA. Electronic address: faye.koenigsmark@uconn.edu.
authors.forename: Faye
authors.initials: F
authors.lastname: Koenigsmark
authors.affiliation: Department of Civil and Environmental Engineering, University of Connecticut, Storrs, CT 06269, USA; Center for Environmental Science and Engineering, University of Connecticut, Storrs, CT 06269, USA. Electronic address: vadas@engr.uconn.edu.
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Vadas
mesh_terms: D000327:Adsorption; D011232:Chemical Precipitation; D003300:Copper / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D006812:Humic Substances; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D012996:Solutions
chemical_list: D005290:Ferric Compounds; D006812:Humic Substances; D012996:Solutions; C000499:ferric oxide; D003300:Copper; C092844:ferric oxyhydroxide
keywords: Copper; Coprecipitation; Ferrihydrite; Humic acids; Organic carbon; Sorption