Aggregation, Dissolution, and Transformation of Copper Nanoparticles in Natural Waters

Abstract

Time-dependent aggregation, sedimentation, dissolution, and transformation of three copper-based engineered nanomaterials (ENMs) of varied properties were measured in eight natural and artificial waters. Nano-Cu and Cu(OH) 2 aggregated rapidly to >10 3 nm while the aggregate size of nano-CuO averaged between 250 and 400 nm. Aggregate size for both nano-Cu and nano-CuO showed a positive correlation with ionic strength with a few exceptions. Aggregate size did not correlate well with sedimentation rate, suggesting sedimentation was influenced by other factors. Controlling factors in sedimentation rates varied by particle: Cu(OH) 2 particles remained stable in all waters but groundwater, nano-Cu was generally unstable except in waters with high organic content, and nano-CuO was stabilized by the presence of phosphate, which reversed surface charge polarity at concentrations as low as 0.1 mg PO 4 3− L −1. Dissolution generally correlated with pH, although in saline waters, dissolved copper formed insoluble complexes. Nano-Cu was rapidly oxidized, resulting in dissolution immediately followed by the formation of precipitates. These results suggest factors including phosphate, carbonate, and ENM oxidation state may be key in determining Cu ENM behavior in natural waters.

Aqueous stability and mobility of C60 complexed by sodium dodecyl benzene sulfonate surfactant

“…However, when the NaCl concentration increased to 200 mmol/L, the growth of the hydrated particle radius became observable. The positive correlation of the aggregate size of SDBS-complexed C 60 with ionic strength is in accordance with other kinds of nano-particles (Conway et al, 2015). With the further increase in NaCl concentration from 200 to 550 mmol/L, the drHðtÞ dt value increased rapidly, which meant an increasing degree of aggregation with increasing electrolyte concentration.…”

Release and detection of nanosized copper from a commercial antifouling paint

“…In general, dissolved organic carbon (DOC) enhances dissolution of Cu in natural waters via complexation Conway et al, 2015). In this study however, complexation of Cu by DOC is minimal compared to that of Cl À based on the amounts of both complexing agents present.…”

“…4). In a previous study using MINTEQ modeling, copper nanoparticles were predicted to oxidize, at equilibrium, mainly to CuO and Cu 2 Cl(OH) 3 in marine systems (Conway et al, 2015). It should be noted that CuO can also dissolve to an extent over time, leading to more complexation and precipitation…”

“…This explains the abundance of Cu diss in seawater (Cl À z 19.3 g/L (Keller et al, 2010)) and estuary (Cl À z 9.70 g/L, based on dilution of seawater), compared to freshwater, (Cl À ¼ 0.06 g/L; determined by a Hg(NO 3 ) 2 titration method, Hanna Instruments) (Conway et al, 2015). Although the fraction of Cu diss decreased over time in seawater, the actual concentration of Cu diss increased from 18.4 mg/ L at the start of the experiment to 555 mg/L after 180 d. Increasing amounts of Cu bulk over time in seawater is probably due to the formation of Cu 2þ solids (e.g.…”

“…Total Cu leached ( Conway et al, 2015). A TEM micrograph of paint leachate showing the presence of particles is shown in Fig.…”