The application of
molybdenum disulfide (MoS2) for water decontamination is
expanded toward a novel approach for mercury removal using nanofibrous
mats coated with MoS2. A bottom-up synthesis method for
growing MoS2 on carbon nanofibers was employed to maximize
the nanocomposite decontamination potential while minimizing the release
of the nanomaterial to treated water. First, a co-polymer of polyacrylonitrile
and polystyrene was electrospun as nanofibrous mats and pretreated
to form pristine carbon fibers. Next, three solvothermal methods of
controlled in situ MoS2 growth of different morphologies
were achieved on the surface of the fibers using three different sets
of precursors. Finally, these MoS2-enabled fibers were
extensively characterized and evaluated for their mercuric removal
efficiency. Two mercury removal mechanisms, including reduction–oxidation
reactions and physicochemical adsorption, were elucidated. The two
nanocomposites with the fastest (0.436 min–1 mg–1) and highest mercury removal (6258.7 mg g–1) were then further optimized through intercalation with poly(vinylpyrrolidone),
which increased the MoS2 interlayer distance from 0.68
nm to more than 0.90 nm. The final, optimal fabrication technique
(evaluated according to mercuric capacity, kinetics, and nanocomposite
stability) demonstrated five times higher adsorption than the second-best
method and obtained 70% of the theoretical mercury adsorption capacity
of MoS2. Overall, results from this study indicate an alternative,
advanced material to increase the efficiency of aqueous mercury removal
while also providing the basis for other novel environmental applications
such as selective sensing, disinfection, and photocatalysis.
This study demonstrates the fabrication of nanoceria-immobilized silica nanofibers for efficient water decontamination with easy reuse and regeneration properties. Commercially-available ceria (CeO 2 ) nanoparticles were immobilized on electrospun silica nanofiber mats. Optimal conditions for both oxidation of model trace organic compounds (TrOCs) and hydroxyl-radical formation were determined in batch experiments with ceria nanoparticles. Kinetic experiments showed comparable oxidation rates of positively-and neutrally-charged TrOCs (95 and 98%, respectively) by the nanofiber composites at pH 2 in 0.5 mM H 2 O 2 . We demonstrated the reuse properties of the ceria nanofiber composites, finding less than a 15% reduction in oxidation performance after 10 cycles. In addition to this oxidative performance, the electrospun CeO 2 nanofiber composites are also applicable for adsorbing the persistent contaminant perfluorooctanesulfonic acid (PFOS) through electrostatic interactions. Regeneration of the fibers was enabled through a one-hour heat treatment at 550 C in air. Overall, results from this study show that the nanoceria-immobilized silica nanofibers can be used as efficient oxidative and adsorptive media to treat TrOCs in acidic waters, without use of an additional catalyst separation stage from solution.
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