1 research outputs found
Hydroxyl Radical Formation during Ozonation of Multiwalled Carbon Nanotubes: Performance Optimization and Demonstration of a Reactive CNT Filter
We
explored factors influencing hydroxyl radical (<sup>•</sup>OH) formation during ozonation of multiwalled carbon nanotubes (MWCNTs)
and assessed this system’s viability as a next-generation advanced
oxidation process (AOP). Using standard reactivity metrics for ozone-based
AOPs (<i>R</i><sub>CT</sub> values), MWCNTs promoted <sup>•</sup>OH formation during ozonation to levels exceeding ozone
(both alone and with activated carbon) and equivalent to ozone with
hydrogen peroxide. MWCNTs oxidized with nitric acid exhibited vastly
greater rates of ozone consumption and <sup>•</sup>OH formation
relative to as-received MWCNTs. While some of this enhancement reflects
their greater suspension stability, a strong correlation between <i>R</i><sub>CT</sub> values and surface oxygen concentrations
from X-ray photoelectron spectroscopy suggests that surface sites
generated during MWCNT oxidation promote <sup>•</sup>OH exposure.
Removal of several ozone-recalcitrant species [<i>para</i>-chlorobenzoic acid (<i>p</i>-CBA), atrazine, DEET, and
ibuprofen] was not significantly inhibited in the presence of radical
scavengers (humic acid, carbonate), in complex aquatic matrices (Iowa
River water) and after 12 h of continuous exposure of MWCNTs to concentrated
ozone solutions. As a proof-of-concept, oxidized MWCNTs deposited
on a ceramic membrane chemically oxidized <i>p</i>-CBA in
a flow through system, with removal increasing with influent ozone
concentration and mass of deposited MWCNTs (in mg/cm<sup>2</sup>).
This hybrid membrane platform, which integrates adsorption, oxidation,
and filtration via an immobilized MWCNT layer, may serve as the basis
for future novel nanomaterial-enabled technologies, although long-term
performance trials under representative treatment scenarios remain
necessary