Heteroaggregation of CeO2 nanoparticles in presence of alginate and iron (III) oxide

Abstract

When manufactured nanoparticles are released to natural waters, heteroaggregation between nanoparticles and water compounds is expected to occur and play a key role in nanoparticle fate, transport and transformation. In this work, the heteroaggregation between CeO2 nanoparticles and Fe2O3 inorganic colloids, which represent the main inorganic fraction from Lake Geneva water, is studied. The heteroaggregation processes between CeO2, Fe2O3 and alginate in multiple water samples are investigated using zeta potential and z-average diameter measurements. The kinetics of heteroaggregation of individual components as well as mixtures of CeO2 nanoparticles and Fe2O3 colloids and alginate are studied using time resolved dynamic light scattering. The global attachment efficiency (αglobal) is calculated using data from kinetic experiments. αglobal for pristine CeO2 nanoparticles varied from 0.5 to 0.7 in lake and synthetic waters and is found around 1 for pristine Fe2O3 and mixture CeO2 and Fe2O3. Our findings demonstrate that heteroaggregation is highly dependent on environmental conditions and resulting electrostatic scenarios. No heteroaggregation at pH 8 between CeO2, Fe2O3 and alginate is observed in ultrapure water, because of electrostatic repulsions between negatively charged compounds. In synthetic and lake waters, the situation is opposite. Indeed, specific adsorption of divalent cations and presence of salt are found to promote heteroaggregation via cation bridging and screening effects. The kinetic experiments indicate that aggregation rate of pristine Fe2O3 is higher (89 nm/min in lake water) compared to pristine CeO2 nanoparticles (50 nm/min) and on the same level as mixture of CeO2 and Fe2O3 (96 nm/min). Low alginate concentration, 0.25 mg/L, has no effect on heteroaggregation in mixture of CeO2 and Fe2O3 in lake and synthetic waters. On the other hand, in natural water, the presence of higher alginate concentration, 2 mg/L, is found to reduce the heteroaggregation rate.

Assessing CeO2 and TiO2 Nanoparticle Concentrations in the Seine River and Its Tributaries Near Paris

“…In addition to TiO 2 , ZnO, and CeO 2 NPs aggregates were also shown to be stabilized at 300 nm with the occurrence of NOM in mesocosm freshwater (Keller et al, 2010) and natural surface waters (Peters et al, 2018). In another study, NOM stabilized CeO 2 NPs (from 2.2 mgC L −1 in an algal medium) and prevented the formation of larger aggregation of the NPs (>1 mm; Van Hoecke et al, 2011;Oriekhova and Stoll, 2019). Moreover, CeO 2 NPs are supposed to be insoluble at pH higher than 7 .…”

“…CeO 2 NPs are insoluble in water when the pH is superior to 7 , which is the case of the Seine River and of the studied tributaries. Moreover, the occurrence of Natural Organic Matter (NOM) as well as the ionic strength are parameters that will partly control the aggregation state of TiO 2 NPs and CeO 2 NPs (Van Hoecke et al, 2011;Oriekhova and Stoll, 2019). The aggregation of the NPs are dependent of the ionic strength with a commonly observed increase of aggregation when the ionic strength increases (Thio et al, 2011).…”

Removal efficiency and adsorption mechanisms of CeO2 nanoparticles onto granular activated carbon used in drinking water treatment plants

“…In natural aquatic systems such as Lake Geneva, the presence of NOM, multivalent ions and suspended particles can strongly affect CeO 2 NPs surface properties and aggregation state (Oriekhova and Stoll, 2019).…”

Strategies for determining heteroaggregation attachment efficiencies of engineered nanoparticles in aquatic environments

“…18 It has also been applied to study heteroaggregation by several authors. 49,[60][61][62][63][64][65][66][67] The determination of α homo,11 using time-resolved DLS follows eqn (4) and is described in more detail in Chen and Elimelech, 55 Holthoff et al, 56 Kretzschmar et al 68 or Petosa et al 18 The main advantages of DLS are its relative ease of use and the wide availability of the instrument. However, DLS relies on particle motion being solely driven by diffusion.…”

“…laser diffraction) and model calculations. 53,54 Moreover, the determination of α global may be feasible 65 when the limitations of DLS are taken into account.…”