title: Effects of molecular weight-dependent physicochemical heterogeneity of natural organic matter on the aggregation of fullerene nanoparticles in mono- and di-valent electrolyte solutions.
abstract: Given the wide presence of heterogeneous natural organic matter (NOM) and metal ions (Na(+)/Ca(2+)/Mg(2+)), as well as their significant role in governing nanoparticle stability in aqueous environments, it is of great importance to understand how the molecular weight (MW)-dependent physicochemical properties of NOM impact fundamental transportation processes like the aggregation of engineered nanoparticles (ENPs) in the presence of Na(+)/Ca(2+)/Mg(2+). Here, we report on the aggregation behavior of a model ENP, fullerene nanoparticles (nC60) in the presence of five MW fractions of Suwannee River NOM (Mf-SRNOMs, separated by ultrafiltration techniques) and three electrolytes (NaCl, CaCl2 and MgCl2). We found that in all NaCl treatments and low concentration CaCl2/MgCl2 treatments, the enhancement of nC60 stability positively correlated with the MW of Mf-SRNOMs. Whereas, the stability efficiency of identical Mf-SRNOM in different electrolytes followed an order of NaCl > MgCl2 > CaCl2, and the enhanced attachment of nC60-SRNOM associations was observed in high MW Mf-SRNOM (SRNOM>100 kD and SRNOM 30-100 kD) at high concentration CaCl2/MgCl2. Our results indicate that although the high MW NOM with large humic-like material is the key component for stabilizing nC60 in monovalent electrolyte, it could play a reversed role in promoting the attachment of nC60, especially in long term aggregations and at high concentrations of divalent cations. Therefore, a detailed understanding of the effects of heterogeneous NOM on the aggregation of ENPs should be highly valued, and properly assessed against different cation species and concentrations.
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China.
authors.forename: Mo-Hai
authors.initials: MH
authors.lastname: Shen
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China.
authors.forename: Yong-Guang
authors.initials: YG
authors.lastname: Yin
authors.affiliation: SINTEF Materials and Chemistry, Trondheim, NO-7465, Norway.
authors.forename: Andy
authors.initials: A
authors.lastname: Booth
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China. Electronic address: jfliu@rcees.ac.cn.
authors.forename: Jing-Fu
authors.initials: JF
authors.lastname: Liu
mesh_terms: D002122:Calcium Chloride / Q000737:chemistry; D004573:Electrolytes; D005618:Fresh Water / Q000737:chemistry; D037741:Fullerenes / Q000737:chemistry*; D006812:Humic Substances / Q000032:analysis*; D015636:Magnesium Chloride / Q000737:chemistry; D008970:Molecular Weight; D053758:Nanoparticles / Q000737:chemistry; D009930:Organic Chemicals / Q000737:chemistry*; D012965:Sodium Chloride / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000737:chemistry
chemical_list: D004573:Electrolytes; D037741:Fullerenes; D006812:Humic Substances; D009930:Organic Chemicals; D014874:Water Pollutants, Chemical; D015636:Magnesium Chloride; D012965:Sodium Chloride; D002122:Calcium Chloride
keywords: Aggregation; Electrolytes; Fullerene nanoparticles (nC(60)); Molecular weight (MW); Natural organic matter (NOM)