Impact of CeO2 nanoparticles on the aggregation kinetics and stability of polystyrene nanoplastics: Importance of surface functionalization and solution chemistry

• Published in: Water research (Oxford) 2020-11, Vol.186, p.116324-116324, Article 116324
• Main Authors: Li, Xing, He, Erkai, Xia, Bing, Van Gestel, Cornelis A.M., Peijnenburg, Willie J.G.M., Cao, Xinde, Qiu, Hao
• Format: Article
• Language: English
• Subjects: Engineered nanoparticles; Hydrochemical condition; Stability; Surface functional groups
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2020.116324

•The presence of CeO2 NPs aggravated the aggregation of polystyrene nanoplastics.•Surface coatings affected the interaction patterns between PS NPs and CeO2 NPs.•NOMs played a role in the heteroaggrergation of PS NPs with CeO2 NPs in sea water.•High anion levels induced a fast heteroaggreagtion of PS-NH2 and CeO2 NPs. The increasing application of plastics is accompanied by increasing concern over the stability and potential risk of nanoplastics. Heteroaggregation with metal-based nanoparticles (e.g., CeO2-NPs) is critical to the environmental mobility of nanoplastics, as they are likely to be jointly emitted to the aquatic environment. Here, time-resolved dynamic light scattering was employed to evaluate the influence of CeO2-NPs on the aggregation kinetics of differentially surface functionalized polystyrene nanoplastics (PS-NPs) in various water types. Natural organic matters and ionic strength were dominating factors influencing the heteroaggregation of PS-NPs and CeO2-NPs in surface waters. The critical coagulation concentrations of PS-NPs were dependent on their surface coatings, which decreased in the presence of CeO2-NPs due to electrostatic attraction and/or specific adsorption. Incubation of PS-NPs and CeO2-NPs under different pH confirmed the importance of electrostatic force in the aggregation of PS NPs. A relatively low humic acid (HA) concentration promoted the heteroaggregation of NH2-coated PS-NPs and CeO2-NPs because the introduction of a HA surface coating decreased the electrostatic hindrance. At high HA concentrations, the aggregation was inhibited by steric repulsion. The combined effects of high efficiency of double layer compression, bridging and complexation contributed to the high capacity of Ca2+ in destabilizing the particles. These findings demonstrate that the environmental behavior of nanoplastics is influenced by the presence of other non-plastic particles and improve our understanding of the interactions between PS-NPs and CeO2-NPs in complex and realistic aqueous environments. [Display omitted]