This review article is devoted to bridging the conventional and newly-developed NF membranes with the potential environmental applications by systematically discussing the synthesis–property–performance relationships.
Despite recent advancements in photocatalysis
enabled by materials
science innovations, the application of photocatalysts in water treatment
is still hampered due to low overall efficiency. Herein, we present
a TiO2 photocatalytic process with significantly enhanced
efficiency by the introduction of micro–nano bubbles (MNBs).
Notably, the removal rate of a model organic contaminant (methylene
blue, MB) in an air MNB-assisted photocatalytic degradation (PCD)
process was 41–141% higher than that obtained in conventional
macrobubble (MaB)-assisted PCD under identical conditions. Experimental
observations and supporting mechanistic modeling suggest that the
enhanced photocatalytic degradation is attributed to the combined
effects of increased dissolution of oxygen, improved colloidal stability
and dispersion of the TiO2 nanocatalysts, and interfacial
photoelectric effects of TiO2/MNB suspensions. The maximum
dissolved oxygen (DO) concentration of the MNB suspension (i.e., 11.7
mg/L) was 32% higher than that of an MaB-aerated aqueous solution
(i.e., 8.8 mg/L), thus accelerating the hole oxidation of H2O on TiO2. We further confirmed that the MNBs induced
unique light-scattering effects, consequently increasing the optical
path length in the TiO2/MNB suspension by 7.6%. A force
balance model confirmed that a three-phase contact was formed on the
surface of the bubble–TiO2 complex, which promoted
high complex stability and PCD performance. Overall, this study demonstrates
the enhanced photocatalytic water decontamination by MNBs and provides
the underlying mechanisms for the process.
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