title: Polyphosphates and Fulvates Enhance Environmental Stability of PO4-Bearing Colloidal Iron Oxyhydroxides.
abstract: Iron oxyhydroxide nanoparticles (Fe-NPs) are natural vectors of phosphate (PO4) in the environment. Their mobility is determined by colloidal stability, which is affected by surface composition. This might be manipulated in engineered NPs for environmental or agricultural applications. Here, the stability of PO4-Fe-NPs (HFO/goethite) was determined across contrasting environmental conditions (pH, Ca concentration) and by using fulvates (FA) and polyphosphates (poly-P's) as coatings. The PO4-Fe-NPs are unstable at Ca concentrations above 0.1 mM. Addition of FA and some poly-P's significantly improved stability. Zeta potential explained colloidal stability across treatments; surface charge was calculated with surface complexation models and explained for phytic acid (PA) and hexametaphosphate (HMP) by a partial (1-4 of the 6 PO4units) adsorption to the surface, while the remaining PO4units stayed in solution. This study suggests that Ca concentration mainly affects the mobility of natural or engineered PO4-Fe-NPs and that HMP is a promising agent for increasing colloidal stability.
authors.affiliation: Department of Earth and Environmental Sciences, KU Leuven , Kasteelpark Arenberg 20 bus 2459, 3001 Leuven, Belgium.
authors.forename: Jessica
authors.initials: J
authors.lastname: Bollyn
authors.affiliation: Department of Earth and Environmental Sciences, KU Leuven , Kasteelpark Arenberg 20 bus 2459, 3001 Leuven, Belgium.
authors.forename: Mathias
authors.initials: M
authors.lastname: Nijsen
authors.affiliation: Department of Earth and Environmental Sciences, KU Leuven , Kasteelpark Arenberg 20 bus 2459, 3001 Leuven, Belgium.
authors.forename: Stijn
authors.initials: S
authors.lastname: Baken
authors.affiliation: Department of Microbial and Molecular Systems, KU Leuven , Kasteelpark Arenberg 22 bus 2463, 3001 Leuven, Belgium.
authors.forename: Iris
authors.initials: I
authors.lastname: Joye
authors.affiliation: Service Trace Elements, CODA-CERVA , Leuvensesteenweg 17, 3080 Tervuren, Belgium.
authors.forename: Nadia
authors.initials: N
authors.lastname: Waegeneers
authors.affiliation: Department of Soil and Environment, SLU , Box 7014, 750 07 Uppsala, Sweden.
authors.forename: Geert
authors.initials: G
authors.lastname: Cornelis
authors.affiliation: Department of Earth and Environmental Sciences, KU Leuven , Kasteelpark Arenberg 20 bus 2459, 3001 Leuven, Belgium.
authors.forename: Erik
authors.initials: E
authors.lastname: Smolders
mesh_terms: D000327:Adsorption; D003102:Colloids / Q000737:chemistry; D005290:Ferric Compounds / Q000737:chemistry*; D058085:Iron Compounds / Q000737:chemistry; D008903:Minerals / Q000737:chemistry; D053758:Nanoparticles / Q000737:chemistry; D011122:Polyphosphates / Q000737:chemistry*
chemical_list: D003102:Colloids; D005290:Ferric Compounds; D058085:Iron Compounds; D008903:Minerals; D011122:Polyphosphates; C094886:goethite; C021024:ferric hydroxide
keywords: colloidal stability; iron oxyhydroxide nanoparticles; natural organic matter; phosphate transport; phytate; polyphosphate