Issue 2, 2019

Mechanisms limiting the release of TiO2 nanomaterials during photocatalytic cement alteration: the role of surface charge and porous network morphology

Abstract

Nanomaterials have been widely used in a wide range of manufactured products in order to improve/add new properties. Photocatalytic cement maintains clean and white wall fronts and also provides interesting air pollution-reducing properties due to the photocatalytic activity of incorporated TiO2-NMs. However, despite these environmental benefits, there is evidence of the release of TiO2-NMs during cement use. Therefore, it is crucial to understand the parameters controlling TiO2-NM release. The zeta potentials of TiO2-NMs were investigated from the unaltered core to the cement altered surface using simulated cement pore waters. The mineralogy and chemical composition of the altered layer were investigated using X-ray diffraction (XRD) and micro X-ray fluorescence spectroscopy (micro-XRF). Finally, the pore network morphology was fully analyzed using X-ray computed tomography at both micro and nano-scales (micro and nano-CT) and quantified using 3D morphological software (i-Morph). This study provides evidence that the TiO2-NM release comes from a very thin “active surface layer” (thickness less than 20 μm) where both the cement surface chemistry and the pore network appear to be favorable for the TiO2-NM diffusion. The pore volume connected to the surface with a throat size of ≥1016 nm appears to control and be used as a predictor for TiO2-NM release.

Graphical abstract: Mechanisms limiting the release of TiO2 nanomaterials during photocatalytic cement alteration: the role of surface charge and porous network morphology

Supplementary files

Article information

Article type
Paper
Submitted
28 Jun 2018
Accepted
10 Jan 2019
First published
11 Jan 2019

Environ. Sci.: Nano, 2019,6, 624-634

Mechanisms limiting the release of TiO2 nanomaterials during photocatalytic cement alteration: the role of surface charge and porous network morphology

N. Bossa, P. Chaurand, C. Levard, J. Vicente, D. Borschneck, C. Geantet, O. Aguerre-Chariol and J. Rose, Environ. Sci.: Nano, 2019, 6, 624 DOI: 10.1039/C8EN00700D

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