Abstract
Aggregation of engineered nanoparticles (NPs) plays a crucial role in their environmental transport, fate,bioavailability and biological effects. This study investigated the temperature effect on the aggregation kinetics of CeO2 NPs in KCl and CaCl2 solutions using time-resolved dynamic light scattering. The results show that in KCl and CaCl2, the aggregation rate became faster as the temperature increased. The critical coagulation concentration (CCC) of CeO2 NPs went down from approximately 100 to 10 mM in KCl and from approximately 10 to 2 mM in CaCl2 solutions when the temperature increased from 4 to 37°C. The observations were analyzed in the framework of extended Derjaguin-Landau-Verwey-Overbeek (EDLVO) theory in order to find out the mechanisms underlying the temperature effect. Moreover, a theoretical model developed on the basis of EDLVO theory and von Smoluchowski’s population balance equation was used to predict the aggregation kinetics of CeO2 NPs under different temperature. The model predictions agreed well with experimental data, suggesting that the model could be employed to predict the size change of NPs in solution. Overall, this work provides insights into NP aggregation using experimental and modeling approaches, and allows people to better understand and theoretically predict the environmental behavior and risk of NPs.
Highlights
Engineered nanoparticles (NPs) have received enormous attention owing to their potential commercial and industrial applications in many sectors, such as cosmetics, textiles, pharmaceutical, catalysts and electronics [1,2]
The lower zeta potential of CeO2 NPs implies that the electrostatic repulsion force between particles is weaker, and this probably promotes the particle aggregation
As the temperature increased from 4°C to 37°C, the coagulation concentration (CCC) for CeO2 NPs decreased from ca. 100 to 10 mM in KCl and from ca. 10 to 2 mM in CaCl2
Summary
Engineered nanoparticles (NPs) have received enormous attention owing to their potential commercial and industrial applications in many sectors, such as cosmetics, textiles, pharmaceutical, catalysts and electronics [1,2]. It is important to evaluate the environmental and health risks of NPs before their mass production. Since the toxicological testing’s of NPs are expensive and time-consuming, researchers are developing theoretical models to evaluate and predict the behavior and risks of NPs in environmental systems [4,5,6]. The aggregation of NPs is fundamentally governed by the interfacial force between interacting particles, which includes several either attractive or repulsive forces. For NP aggregation, many studies have found that a discrepancy exists between DLVO predictions and experimental observations [14]. This problem might be overcome by taking non-DLVO forces into account, such as the polar Lewis acid/base (AB) force [15] and steric force [16]. The precise theoretical analysis of NP interaction and quantitative description of NP aggregation can be obtained by incorporating those non-DLVO forces into the DLVO theory, which is known as the extended DLVO (EDLVO or XDLVO) theory [15]
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