Effects of pH and fulvic acids concentration on the stability of fulvic acids--cerium (IV) oxide nanoparticle complexes.
The behavior of cerium (IV) oxide nanoparticles has been first investigated at different pH conditions. The point of zero charge was determined as well as the stability domains using dynamic light scattering, nanoparticle tracking analysis and scanning electron microscopy. A baseline hydrodynamic diameter of 180 nm was obtained indicating that individual CeO2 nanoparticles are forming small aggregates. Then we analyzed the particle behavior at variable concentrations of fulvic acids for three different pH-electrostatic scenarios corresponding to positive, neutral and negative CeO2 surface charges. The presence of fulvic acids was found to play a key role on the CeO2 stability via the formation of electrostatic complexes. It was shown that a small amount of fulvic acids (2 mg L(-1)), representative of environmental fresh water concentrations, is sufficient to stabilize CeO2 nanoparticles (50 mg L(-1)). When electrostatic complexes are formed between negatively charged FAs and positively charged CeO2 NPs the stability of such complexes is obtained with time (up to 7 weeks) as well as in pH changing conditions. Based on zeta potential variations we also found that the fulvic acids are changing the CeO2 acid-base surface properties. Obtained results presented here constitute an important outcome in the domain of risk assessment, transformation and removal of engineered nanomaterials released into the environment.
University of Geneva, Earth and Environmental Science Section, F.-A. Forel Institute, Group of Environmental Physical Chemistry, 10 Route de Suisse, CH-1290 Versoix, Switzerland. Electronic address: Olena.Oriekhova@unige.ch.
Olena
O
Oriekhova
University of Geneva, Earth and Environmental Science Section, F.-A. Forel Institute, Group of Environmental Physical Chemistry, 10 Route de Suisse, CH-1290 Versoix, Switzerland. Electronic address: Serge.Stoll@unige.ch.
Serge
S
Stoll
D001578:Benzopyrans / Q000737:chemistry*; D002563:Cerium / Q000737:chemistry*; D005618:Fresh Water / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D053768:Metal Nanoparticles / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D055672:Static Electricity; D013499:Surface Properties
D001578:Benzopyrans; D010087:Oxides; D002563:Cerium; C005023:fulvic acid
CeO(2) nanoparticles; Fulvic acids; Hydrophobic effect; Nanoparticle coating; Nanoparticle stability; Nanoparticle surface charge and pH