4 research outputs found
Low-Temperature Carbon Capture Using Aqueous Ammonia and Organic Solvents
Current postcombustion CO<sub>2</sub> capture technologies are
energy intensive, require high-temperature heat sources, and dramatically
increase the cost of power generation. In this work, we introduce
a new carbon capture process requiring significantly lower temperatures
and less energy, creating further impetus to reduce CO<sub>2</sub> emissions from power generation. In this process, high-purity CO<sub>2</sub> is generated through the addition of an organic solvent (acetone,
dimethoxymethane, or acetaldehyde) to a CO<sub>2</sub> rich, aqueous
ammonia/carbon dioxide solution under room-temperature and -pressure
conditions. The organic solvent and CO<sub>2</sub>-absorbing solution
are then regenerated using low-temperature heat. When acetone, dimethoxymethane,
or acetaldehyde was added at a concentration of 16.7% (v/v) to 2 M
aqueous ammonium bicarbonate, 39.8, 48.6, or 86.5%, respectively,
of the aqueous CO<sub>2</sub> species transformed into high-purity
CO<sub>2</sub> gas over 3 h. Thermal energy and temperature requirements
for recovering acetaldehyde, the best-performing organic solvent investigated,
and the CO<sub>2</sub>-absorbing solution were 1.39 MJ/kg of CO<sub>2</sub> generated and 68 °C, respectively, 75% less energy than
the amount used in a pilot chilled ammonia process and a temperature
53 °C lower. Our findings exhibit the promise of economically
viable carbon capture powered entirely by abundant low-temperature
waste heat
Hydrophobic CuO Nanosheets Functionalized with Organic Adsorbates
A new
class of hydrophobic CuO nanosheets is introduced by functionalization
of the cupric oxide surface with <i>p</i>-xylene, toluene,
hexane, methylcyclohexane, and chlorobenzene. The resulting nanosheets
exhibit a wide range of contact angles from 146° (<i>p</i>-xylene) to 27° (chlorobenzene) due to significant changes in
surface composition induced by functionalization, as revealed by XPS
and ATR-FTIR spectroscopies and computational modeling. Aromatic adsorbates
are stable even up to 250–350 °C since they covalently
bind to the surface as alkoxides, upon reaction with the surface as
shown by DFT calculations and FTIR and <sup>1</sup>H NMR spectroscopy.
The resulting hydrophobicity correlates with H<sub>2</sub> temperature-programmed
reduction (H<sub>2</sub>-TPR) stability, which therefore provides
a practical gauge of hydrophobicity
Loss of Phospholipid Membrane Integrity Induced by Two-Dimensional Nanomaterials
The
interaction of two-dimensional (2D) nanomaterials with biological
membranes has important implications for ecotoxicity and human health.
In this study, we use a dye-leakage assay to quantitatively assess
the disruption of a model phospholipid bilayer membrane (i.e., lipid
vesicles) by five emerging 2D nanomaterials: graphene oxide (GO),
reduced graphene oxide (rGO), molybdenum disulfide (MoS<sub>2</sub>), copper oxide (CuO), and iron oxide (α-Fe<sub>2</sub>O<sub>3</sub>). Leakage of dye from the vesicle inner solution, which indicates
loss of membrane integrity, was observed for GO, rGO, and MoS<sub>2</sub> nanosheets but not for CuO and α-Fe<sub>2</sub>O<sub>3</sub>, implying that 2D morphology by itself is not sufficient
to cause loss of membrane integrity. Mixing GO and rGO with lipid
vesicles induced aggregation, whereas enhanced stability (dispersion)
was observed with MoS<sub>2</sub> nanosheets, suggesting different
aggregation mechanisms for the 2D nanomaterials upon interaction with
lipid bilayers. No loss of membrane integrity was observed under strong
oxidative conditions, indicating that nanosheet-driven membrane disruption
stemmed from a physical mechanism rather than chemical oxidation.
For GO, the most disruptive nanomaterial, we show that the extent
of membrane integrity loss was dependent on total surface area, not
edge length, which is consistent with a lipid-extraction mechanism
and inconsistent with a piercing mechanism
Shape-Dependent Surface Reactivity and Antimicrobial Activity of Nano-Cupric Oxide
Shape
of engineered nanomaterials (ENMs) can be used as a design
handle to achieve controlled manipulation of physicochemical properties.
This tailored material property approach necessitates the establishment
of relationships between specific ENM properties that result from
such manipulations (e.g., surface area, reactivity, or charge) and
the observed trend in behavior, from both a functional performance
and hazard perspective. In this study, these structure–property-function
(SPF) and structure–property-hazard (SPH) relationships are
established for nano-cupric oxide (n-CuO) as a function of shape,
including nanospheres and nanosheets. In addition to comparing these
shapes at the nanoscale, bulk CuO is studied to compare across length
scales. The results from comprehensive material characterization revealed
correlations between CuO surface reactivity and bacterial toxicity
with CuO nanosheets having the highest surface reactivity, electrochemical
activity, and antimicrobial activity. While less active than the nanosheets,
CuO nanoparticles (sphere-like shape) demonstrated enhanced reactivity
compared to the bulk CuO. This is in agreement with previous studies
investigating differences across length-scales. To elucidate the underlying
mechanisms of action to further explain the shape-dependent behavior,
kinetic models applied to the toxicity data. In addition to revealing
different CuO material kinetics, trends in observed response cannot
be explained by surface area alone. The compiled results contribute
to further elucidate pathways toward controlled design of ENMs