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Influence of electrolyte species and concentration on the aggregation and transport of fullerene nanoparticles in quartz sands
Author(s) -
Wang Yonggang,
Li Yusong,
Pennell Kurt D.
Publication year - 2008
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1897/08-039.1
Subject(s) - electrolyte , quartz , ionic strength , particle (ecology) , nanoparticle , chemistry , chemical engineering , suspension (topology) , particle size , effluent , materials science , geology , electrode , organic chemistry , environmental engineering , composite material , aqueous solution , oceanography , mathematics , homotopy , pure mathematics , engineering
The potential toxicity of nanoscale particles has received considerable attention, but the fate of engineered nanomaterials in the environment has been studied only under a limited set of conditions. In the present study, batch and column experiments were performed to assess the aggregation and transport of nanoscale fullerene (nC 60 ) particles in water‐saturated quartz sands as a function of electrolyte concentration and species. As the electrolyte concentration increased from 1 to 100 mM, the change in nC 60 particle diameter was minimal in the presence of NaCl but increased by more than sevenfold in the presence of CaCl 2 . The latter effect was attributed to the agglomeration of individual nC 60 particles, consistent with a net attractive force between particles and suppression of the electrical double layer. At low ionic strength (3.05 mM), nC 60 particles were readily transported through 40‐ to 50‐mesh quartz sand, appearing in the column effluent after introducing less than 1.5 pore volumes of nC 60 suspension, with approximately 30% and less than 10% of the injected mass retained in the presence of CaCl 2 or NaCl, respectively. At higher ionic strength (30.05 mM) and in finer Ottawa sand (100–140 mesh), greater than 95% of the introduced nC 60 particles were retained in the column regardless of the electrolyte species. Approximately 50% of the deposited nC 60 particles were recovered from 100‐ to 140‐mesh Ottawa sand after sequential introduction of deionized water adjusted the pH to 10 and 12. These findings demonstrate that nC 60 transport and retention in water‐saturated sand is strongly dependent on electrolyte conditions and that release of deposited nC 60 requires substantial changes in surface charge, consistent with retention in a primary energy minimum.