Identification and quantitative characterization of nanoparticles (NPs) in coal flyash (CFA) is critical for a better understanding of the eco-environmental and health related risks caused by CFA. In the present study, various metal-containing NPs were identified based on electron microscopy techniques, among which Fe- and Ti-containing NPs are dominant. Iron oxides, including hematite, magnetite and goethite particles, as well as titanium oxides, including rutile, anatase, and Magnéli phases (TixO2x-1), were found to be ubiquitous in CFA samples. Based on single particle-ICP-MS technique, the particle number concentrations of Fe- and Ti- containing NPs were investigated ranging from 2.5 × 107 to 2.5 × 108 particles/mg, and their concentrations were regulated by the feed coals and combustion conditions of various CFAs tested. In cases where these NPs in CFAs become airborne and are inhaled, they can be taken up in pulmonary interstitial fluids. In the analyzed Gamble’s solution (a pulmonary fluid simulant), 51-87 % of Fe and 63-89 % of Ti existed in NP-oxide form and remained suspended in solution. These NP are bioavailable and have been ignored in past traditional risk assessment methods for metals, which has resulted in underestimates when evaluating the risks caused by CFA related metals.

Metal-containing nanoparticles in coal flyash: Identification, quantification and environmental implications

ACS Fall 2021

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