Abstract
Many studies have shown the effect of solution chemistry on the environmental behavior of metal-based nanoparticles (NPs), except CuO NPs. Here, we investigated the agglomeration, sedimentation, dissolution, and speciation of CuO NPs by varying pH, ionic strength, ionic valence, and natural organic matter (NOM). The results showed that as the pH moved away from 6, the size of CuO agglomerates decreased, along with the enhanced NP suspension stabilization, due to the increase of electrostatic repulsive force. Increasing ionic strength and valence intensified the agglomeration and sedimentation of CuO NPs because of the compression of electrical double layers. The presence of humic acid and citric acid enhanced the dispersion and stabilization of CuO NP suspension, but l-cysteine showed a different impact. Decreasing pH, increasing ionic strength and all NOM improved the dissolution of CuO NPs, but the divalent electrolyte (CaCl2) inhibited the Cu2+ release from CuO NPs compared to the monovalent electrolyte (NaCl). In addition, X-ray absorption near edge structure (XANES) analysis demonstrated that the presence of l-cysteine transformed more than 30% of CuO NPs to Cu(I)-cysteine by coordinating with thiol group. This study can give us an in-depth understanding on the environmental behavior and fate of CuO NPs in the aquatic environment.
Highlights
Metal-based nanoparticles (MNPs), as an important category of engineered nanomaterials, have had a 30% market share of the consumer product nanotechnology, as early as 2009 [1]
The results showed that the effect of cation ions Na+ and Ca2+ on the dissolution of CuO NPs was not significantly different at low ionic strength, divalent cations (Ca2+) had a lesser impact on the CuO NP dissolution when compared to monovalent cations (Na +) at high ionic strength
Our results demonstrate that the solution chemistry obviously alters the environmental behavior of CuO NPs
Summary
Metal-based nanoparticles (MNPs), as an important category of engineered nanomaterials, have had a 30% market share of the consumer product nanotechnology, as early as 2009 [1]. As one of the most important MNPs, copper oxide nanoparticles (CuO NPs) are extensively used in energy storage, sensors, surfactants, catalysts, and antimicrobial agent in various industries, agricultural activities and environmental remediation, due to their specific electrical, thermal, catalytic, and antibacterial properties [2,3,4]. NPs is leading to the release of NPs from point and non-point sources into the environment, especially the aquatic environment. The persistence, bioavailability/bioabsorption, reactivity, and toxicity of NPs are largely determined by the environmental behavior of NPs. it is of significance to understand the transformation of CuO NPs in the aquatic environment for evaluating the environmental and ecological risks of CuO NPs
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