3 research outputs found
Effective Antiscaling Performance of Reverse-Osmosis Membranes Made of Carbon Nanotubes and Polyamide Nanocomposites
The antiscaling properties of multiwalled
carbon nanotube (MWCNT)âpolyamide
(PA) nanocomposite reverse-osmosis (RO) desalination membranes (MWCNTâPA
membranes) were studied. An aqueous solution of calcium chloride (CaCl<sub>2</sub>) and sodium bicarbonate (NaHCO<sub>3</sub>) was used to precipitate
in situ calcium carbonate (CaCO<sub>3</sub>) to emulate scaling. The
MWCNT contents of the studied nanocomposite membranes prepared by
interfacial polymerization ranged from 0 wt % (plain PA) to 25 wt
%. The inorganic antiscaling performances were compared for the MWCNTâPA
membranes to laboratory-made plain and commercial PA-based RO membranes.
The scaling process on the membrane surface was monitored by fluorescence
microscopy after labeling the scale with a fluorescent dye. The deposited
scale on the MWCNTâPA membrane was less abundant and more easily
detached by the shear stress under cross-flow compared to other membranes.
Molecular dynamics simulations revealed that the attraction of Ca<sup>2+</sup> ions was hindered by the interfacial water layer formed
on the surface of the MWCNTâPA membrane. Together, our findings
revealed that the observed outstanding antiscaling performance of
MWCNTâPA membranes results from (i) a smooth surface morphology,
(ii) a low surface charge, and (iii) the formation of an interfacial
water layer. The MWCNTâPA membranes described herein are advantageous
for water treatment
Super-stretchable Graphene Oxide Macroscopic Fibers with Outstanding Knotability Fabricated by Dry Film Scrolling
Graphene oxide (GO) has recently become an attractive building block for fabricating graphene-based functional materials. GO films and fibers have been prepared mainly by vacuum filtration and wet spinning. These materials exhibit relatively high Youngâs moduli but low toughness and a high tendency to tear or break. Here, we report an alternative method, using bar coating and drying of water/GO dispersions, for preparing large-area GO thin films (<i>e.g.</i>, 800â1200 cm<sup>2</sup> or larger) with an outstanding mechanical behavior and excellent tear resistance. These dried films were subsequently scrolled to prepare GO fibers with extremely large elongation to fracture (up to 76%), high toughness (up to 17 J/m<sup>3</sup>), and attractive macroscopic properties, such as uniform circular cross section, smooth surface, and great knotability. This method is simple, and after thermal reduction of the GO material, it can render highly electrically conducting graphene-based fibers with values up to 416 S/cm at room temperature. In this context, GO fibers annealed at 2000 °C were also successfully used as electron field emitters operating at low turn on voltages of <i>ca.</i> 0.48 V/ÎŒm and high current densities (5.3 A/cm<sup>2</sup>). Robust GO fibers and large-area films with fascinating architectures and outstanding mechanical and electrical properties were prepared with bar coating followed by dry film scrolling
Antiorganic Fouling and Low-Protein Adhesion on Reverse-Osmosis Membranes Made of Carbon Nanotubes and Polyamide Nanocomposite
We
demonstrate efficient antifouling and low protein adhesion of multiwalled
carbon nanotubes-polyamide nanocomposite (MWCNT-PA) reverse-osmosis
(RO) membranes by combining experimental and theoretical studies using
molecular dynamics (MD) simulations. Fluorescein isothiocyanate (FITC)-labeled
bovine serum albumin (FITC-BSA) was used for the fouling studies.
The fouling was observed in real time by using a crossflow system
coupled to a fluorescence microscope. Notably, it was observed that
BSA anchoring on the smooth MWCNT-PA membrane was considerably weaker
than that of other commercial/laboratory-made plain PA membranes.
The permeate flux reduction of the MWCNT-PA nanocomposite membranes
by the addition of FITC-BSA was 15% of its original value, whereas
those of laboratory-made plain PA and commercial membranes were much
larger at 34%â50%. Computational MD simulations indicated that
the presence of MWCNT in PA results in weaker interactions between
the membrane surface and BSA molecule due to the formation of (i)
a stiffer PA structure resulting in lower conformity of the molecular
structure against BSA, (ii) a smoother surface morphology, and (iii)
an increased hydrophilicity involving the formation of an interfacial
water layer. These results are important for the design and development
of promising antiorganic fouling RO membranes for water treatment