Wei Zhang - Effects of humic and fulvic acids on aggregation of aqu/nC60 nanoparticles

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      Publication Details (including relevant citation   information):

      Zhang, Wei, Rattanaudompol, U-sa, Li, Hui, Bouchard, Dermont,   Water Research, 2013, 47 (5),   pp 1793-1802


      Aggregation of fullerene nanoparticles (nC60) is a fundamental   process influencing its environmental fate and transport, and   toxicity. Using time-resolved dynamic light scattering we   systematically investigated aggregation kinetics of nC60   generated from extended mixing in water (termed as aqu/nC60) in a   range of symmetrical monovalent (NaCl) or divalent (MgSO4)   electrolyte concentrations with the presence/absence of model   natural organic matter (NOM), i.e., Suwannee River humic acid   (SRHA) and fulvic acid (SRFA), at three pH levels (4, 7.8, 9.8).   Electrophoretic mobility (EPM) data were interpreted according to   the Ohshima's soft particle theory to obtain average   characteristics of the adsorbed NOM layers, which was then used   to explain the observed aggregation profiles. Results indicate   that the presence of NOM stabilized aqu/nC60, and SRHA was more   effective than SRFA in suppressing aqu/nC60 aggregation. The   stabilization effect of NOM in the presence of NaCl was less   pronounced than in the presence of MgSO4, likely as a result of   high aggregation potential of aqu/nC60 in the presence of MgSO4   due to effective charge screening and neutralization. The   differential stabilization capacity between SRHA and SRFA could   be explained by the structural and conformational characteristics   of the adsorbed NOM layers by invoking steric repulsion, as   determined by both the adsorbed layer thickness and the NOM   affinity to aqu/nC60. While this was true under most conditions,   the discrepancy observed in the presence of MgSO4 at pH 9.8 may   be attributed to inter-particle aggregation through Mg2+ binding   with SRFA that is not included in steric repulsion theory.

      Address (URL): http://www.sciencedirect.com/science/article/pii/S004313541300002X